regional committee
PAN AMERICAN
HEALTH
ORGANIZATION
XXIX MeetingWORLD
HEALTH
ORGANIZATION
XXXV Meeting
Washington, D.C.
September - October 1983
INDEXED
158S2t
CD29/INF/2 (Eng.) 12 August 1983
ORIGINAL: ENGLISH-SPANISH
STATUS OF MALARIA PROGRAMS IN THE AMERICAS
XXXI REPORT
TABLE OF CONTENTS
Page
Introduction ... 1
I. PRESENT STATUS OF MALARIA ERADICATION PROGRAMS . 2 A. General Information ... 2
B. Field Operations ... 4
C. Budget ... 5
D. Country Information ... 6
II. PROBLEMS AFFECTING THE PROGRESS OF THE PROGRAM . 16 III. RESEARCH ... 19
A. Trials with insecticides and vector pathogens 19 B. Malaria Chemotherapy ... 21
C. Social Science and Malaria ... 22
D. Information Systems ... 22
E. Malaria Immunology ... 22
IV. PERSONNEL TRAINING ... 23
TABLES, MAPS AND GRAPHS
Tables Page
1 Malaria morbidity in the Americas, 1958-1982 28
2 Population in the malarious areas in the Americas,
1958-1982 ... 29
3 Status of the malaria programs in the Americas,
by population, 1982 ... 30
4 Status of the malaria programs in the Americas,
by area, 1982 ... 31
5 Malaria cases registered, 1979, 1982 ... 32
6 Case detection by country and phase of
program, 1982 ... 34
7 Slides examined and positives, by species
and classification, Maintenance phase, 1982 ... 35
8 Slides examined and positives, by species
and classification, Consolidation phase, 1982 .... 36
9 Slides examined and positives, by species,
Attack phase, 1982 ... 37
10 Slides examined and positives by specie,
Non-malarious areas, 1982 ... 38
11 Comparative results of active and passive
case detection in malaria programs in the Americas,
1982 39
12 Spraying with residual insecticides applied
in 1981 and 1982 in the malaria programs of
the Americas ... 40
13 Insecticides used in the malaria programs,
1982 and estimated 1983 ... 41
-Tables (Cont.) Page
14 Antimalarial Drugs used in the Malaria
Programs in 1982 and Estimated for 1983 ... 42
15 Personnel employed in the malaria programs
in the Americas, 1981 and 1982 ... 43
16 National and International contributions to
the Malaria programs of the Americas,
expenditures 1981-1982 and budget 1983 ... 44
17 Geographical distribution of areas with
technical problems, 1982 ... 49
Maps
1 Status of the Malaria Programs in the Americas,
1982 ... 33
2 Distribution of A. (N) Albimanus and resistance
to DDT and Propoxur (December 1982) ... 46
3 Distribution of A. (A) pseudopunctipennis and
resistance to DDT ... 47
4 Response of P. falciparum to chloroquine ... 48
5 Geographical distribution of areas with
tech-nical problems, 1982 ... 52
Graphs
1 Funds invested in the Malaria Programs in the
Americas, 1957-1982 ... 45
-STATUS OF MALARIA ERADICATION PROGRAMS IN THE AMERICAS XXXI REPORT
INTRODUCTION
The number of malaria cases in the region of the Americas increased
steadily during the last decade: from 344,170 cases in 1970 to 709,255
in 1980. In general, surveillance activities in the remote communities
decreased because of limited resources, transportation problems, and
difficulties related to administrative and human factors. Between 1972
and 1982, the population in the originally malarious areas increased by 29.0%, while the number of blood slides examined in 1982 represented
89.3% of those collected in 1972. Other studies have shown that,
although fewer blood samples were collected in 1982, the slide positivity rate increased (from 3.0% in 1973 to 8.1% in 1982).
The health authorities of the Region have repeatedly expressed concern about the malaria situation at meetings at the Governing Bodies of the Organization at which several pertinent resolutions have been
adopted. In 1978, the XX Pan American Sanitary Conference adopted a
resolution reaffirming that eradication was the goal of the malaria
program in the Americas. The following year, the III Meeting of
Directors of National Malaria Eradication Services (SNEM) was held in Mexico to review the progress and strategy of the program and to prepare a document that was to lay the bases for the development of a hemispheric
plan of action against malaria in the Americas. At its 1979 and 1980
meetings, the Directing Council reviewed the malaria program and
requested the Member Governments and the Organization to reformulate the
national malaria plans with a view to: a) adapting them to the specific
situation in each country; (b) giving top priority to the financing and implementation of those plans; (c) exploring all possible sources of
financing for the support of malaria activities at the national
hemispheric level; and (d) strengthening the training program and
stepping up field research activities.
In 1982, the Member Governments and the Organization continued to make efforts to implement those resolutions, and for that purpose prepared national malaria plans, held a planning seminar on the training of malaria personnel and another on epidemiology of P. falciparum malaria and its resistance to drugs, and expanded research activities in the fields of immunology, chemotherapy, entomology, epidemiology and vector
control. Immediate improvement of the malaria situation is difficult
because of the complexity of the problems which are political, social, economic and human behavioral in nature.
The purpose of this report is to briefly describe the malaria situation in the Region of the Americas and the problems that are impeding progress and to detail research, training and international
cooperation activities. An effort has been made to update the
2
-I. PRESENT STATUS OF MALARIA ERADICATION PROGRAMS
A. General Information
Although the number of positive blood slides has steadily increased since 1974, the number of slides examined has slowly decreased, with
minor yearly fluctuations. The slide positivity rate was 8.1% in 1982,
the highest ever recorded since 1958. The annual parasite incidence for 1982 was 2.86 per 1,000 inhabitants (malarious areas only), also the
highest since the initiation of the malaria eradication program. The
annual blood examination rate fell from 4.6% in 1973 to 3.5% in 1982
because of the smaller number of blood samples obtained from an
increasing population. These indicators show that the general situation
of malaria in the Americas continues to worsen (Table 1). Section I.D.
of this report presents figures for each country.
Following the practice of previous years, all the countries of the region reported on the status of their programs and classified the
malarious areas into the different program phases. Although the original
phase definition criteria are not strictly followed, the classification still serves as a general indicator of the status of the program in
relation to the goal of eradication. In 1982, the population of
different areas was: maintenance phase, 118.3 million inhabitants
(48.2%); consolidation phase, 62.0 million (25.3%); and attack phase,
64.9 million (26.5%). There was no change in the extension of the area
in each phase from the previous year (see Tables 2, 3 and 4).
At the III Meeting of Directors of National Malaria Services held in
Mexico in 1979, the 33 political units were classified into four groups
according to the extent of progress, the magnitude of problems, and the
availability of resources of the malaria programs. This classification
is still valid, but requires a subdivision of Group II and a further notation for other groups if an updated picture of the malaria situation
in 1982 is to be presented (see Table 5). The four groups of countries
are as follows:
Group I. It includes 12 countries and territories with a population
of 75,829,000 or 30.9% of the total population of the originally
malarious area. There was no evidence of malaria transmission in this
group. Although 972 cases were registered, they were all imported or
introduced, compared with 1,599 cases registered in the previous year.
Group II. Eight countries or territories with a total population of
15,637,000 inhabitants or 6.4% of the total population of the originally
malarious areas are included in this group. In all these countries,
malaria transmission was once interrupted or reduced to an insignificant
level. However, because of the importation of cases from neighboring
countries, costly surveillance activities have had to be carried out to
3
-foci of imported cases could be eliminated but at other times it was impossible to prevent the reestablishment of transmission, with the
result that what had been achieved in earlier years was lost. It is
believed that the following two subgroups revealed the present situation:
Subgroup A. Argentina, Costa Rica, Panama and Paraguay have been successful in maintaining the favorable situation observed since 1979. Although importation of malaria cases continued, transmission has never
been reestablished. In spite of the fact that autochthonous cases were
reported, the sources of infection was effectively eliminated in those
countries without leaving residual foci of transmission. Furthermore, in
French Guiana, which also belong to this subgroup, the number of cases registered rose from 769 in 1981 to 1,143 in 1982.
Subgroup B. Since 1979, Belize and the Dominican Republic have
shown a deteriorating trend because malaria transmission has been
reestablished in many areas in which it had been interrupted. In Guyana,
the number of cases registered decreased in 1982.
Group III. This group includes five countries with a total
population of 109,403,000 inhabitants or 44.6% of the total population of
the originally malarious area. Since 1979, transmission has increased in
the areas in the attack phase but there has been no significant change in
those in the consolidation or maintenance phase. In Brazil, there was a
marked increase in the number of malaria cases due to epidemic outbreaks
in the Amazon region where land settlement is intense. In the province
of Esmeraldas, Ecuador, the number of cases increased sharply. In
Mexico, the number of cases registered increased. No significant
progress has been made in Venezuela in the past four years. Suriname
continued to face operational problems with the mobile teams in the interior and frequent interruption in malaria activities; accordingly,
the health authorities decided to transfer responsibility for the
operations to the Medical Mission of the Interior (MEDIZEBS), whose satisfactory network of health services in the area made it possible to give continuity to field activities.
Group IV. The eight countries of this group together have a
population of 44,462,000 inhabitants or 18.1% of the total population of
the originally malarious area. These countries continued to face serious
technical, economic, administrative and financial problems which are
difficult to solve. In 1982, the number of malaria cases registered was
401,927 or 56.7% of the total for the Americas. Only in Bolivia was
there an improvement in the situation, due to the increase in operations to which USAID financial support under Public Law 480 contributed.
Colombia reorganized its malaria activities by order of priority,
following completion of the epidemiological stratification. Of the four
countries of Central America, E1l Salvador and Nicaragua made slight
4
-Table 5 shows the cases of malaria registered in the last four years
in each group of countries and Map 1 shows their distribution. Table 6
summarizes case detection activities by countries and by phase. Tables 7 and 8 show the number of blood slides examined and positives by plasmodium species as well as the classification of malaria cases in the
maintenance and consolidation phases respectively. Tables 9 and 10 show
the number of blood slides examined,the positives and the species of
parasites in the attack phase area and in the non-malarious area. Table
11 compares the results of active and passive case detection by country.
B. Field Operations
The spraying of residual insecticides continues to be the principal antimalarial measure used in the 21 countries with areas in the attack phase and DDT is the insecticide most frequently in intradomiciliary sprayings when the vector is susceptible.
In 1982, the number of DDT sprayings decreased compared with 1981, but those of other insecticides, especially fenitrothion, increased. However, the total number of sprayings with any type of insecticides was
31.5% lower than in 1981. In the Central American countries and in
Haiti, where the vector is DDT resistant, new or alternative insecticides
were most often used. During the year there were 4,462,826 sprayings
with DDT, 779,526 with fenitrothion, 135,721 with chlorphoxim, 104,937
with deltamethrin and 85,848 with propoxur (see Tables 12 and 13). In
Guatemala, deltamethrin was used in a pilot study to establish its
effectiveness. The results were evaluated by a group of national and
international technical personnel which concluded that the insecticide (a synthetic pyrethroid) showed acceptable residual action and produced "good epidemiological results" by reducing the number of cases of malaria
in the test area. However, the product was found to have a certain
excito-repellency effect that needs to be further evaluated.
In Bolivia, Ecuador, El Salvador, Haiti, Mexico, Nicaragua and the Dominican Republic, anti-larval or source reduction measures were applied
but to a lesser extent than in 1981. Types of larvicides or methods of
source reduction were not specified but the inhabitants protected were reported as follows:
Anti-larval Population
Country Measures Protected
Bolivia Larvicides 16,016
Ecuador Larvicides 83,178
El Salvador Larvicides 3,350
Source reduction 105 sites
Haiti Larvicides 115,743
Source reduction 47,751
Mexico Larvicides 202,935
Source reduction 295,139
Nicaragua Larvicides 663,465
5
-Space spraying at ultra low volume was used in El Salvador and protected 140,000 persons and low volume space spraying protected 82,000 inhabitants in
134 localities. In both cases the type of insecticides used was resmethrin (a
synthetic pyrethroid).
Antimalarial drugs continued to be used as an important complementary measure to the application of insecticides and other control measures.
In addition to the routine use of drugs in presumptive and curative treatments, mass drug administration was carried out by the malaria services in order to prevent epidemic outbreaks, reduce high incidence or test the efficacy and acceptability of the health programs planned and executed by public agencies.
The following countries reported on mass drug distribution (MDD):
No. of persons protected
Colombia 870,826
Ecuador (No numerical data available)
El Salvador 330,000 + 165,000 (selective medication)
Haiti 300,662 (mass doing distribution)
Mexico 134,920
Nicaragua 200,000 (radical treatment in three day
schedules
In Guyana chloroquine was distributed in the form of medicated salt to
40,706 inhabitants of districts in the interior of the country. Table 14
shows the amounts of antimalaria drugs administered in 1982 and estimated for 1983.
C. Budget
The expenditures for the malaria programs in 1981 and 1982 and the estimated budget for 1983 are summarized in Table 16 by source of funds and
country.
In 1982, national expenditures for most of the programs increased
compared with 1981 although in some cases the opposite was true. In 1982,
outlays for the countries as a whole decreased by US$15,900,438 (11.2%), compared with 1981.
The 1981 and 1982 figures, for the PAHO/WHO contribution, show the actual expenditures for each year while the figures for 1983 are estimates equivalent to one-half of the 1982-1983 biennial budget.
In 1982, total investments in malaria programs in the Americas amounted to US$126,605,118 and the cumulative total to US$1,673,850,514 of which 90%
came from the governments and 10% from international and bilateral
6
-D. Country Information
ARGENTINA
The area that is still in the attack phase (3.2% of the total malarious area) contains a population of 85,000 inhabitants affected by residual
malaria. The measures used continue to be DDT sprayings and the presumptive
supply of medicaments as well as the radical treatment of the cases detected. Although the household visits made amounted to only 43.1% of the target, the number of cases in this area increased slightly compared with those detected in the previous year. The most important problem occurred in the area in the maintenance phase, where an epidemic outbreak produced 43% of the cases
detected in 1982. This outbreak occurred in the Province of Jujuy and was
attributed to shortcomings in epidemiological surveillance activities.
Only 65% of the target for sprayings in the attack phase area of the
Province of Salta was reached. To control the Jujuy focus, 841 emergency
sprayings were made.
BELIZE
This country attained independence in 1981. Since then, it has been
planned to implement a national health plan; it includes a priority
antimalaria program which will be executed to the extent that resources are
available. The malaria program was assigned to the environmental health
division in the expectation that this would make activities more flexible and
improve supervision. Difficult financial conditions prevented the plan drawn
up from being duly implemented, and the number of cases detected in 1982 was
almost twice those of the previous year. There was also an increase in the
number of P. falciparum infections. The migratory movements of persons coming from neighboring countries and the improvised nature of dwellings erected in new settlements are mentioned as causes of the deterioration in the situation.
BOLIVIA
The malaria situation in this country continued to improve compared with the previous year as a result of an increase in field operations, which was facilitated in part by the financial aid to the program under an agreement with the United States (Public Law 480). The number of cases fell from 16,619
in 1980 to 9,774 in 1981 and 6,699 in 1982.
Attack measures were carried out in the four principal foci of
transmission in the country: the inter-Andean valleys (Yungas) in the central
region; the Bermejo river area in the Department of Tarija, on the border with Argentina, in the east, in the Department of Chaco; and in the north, in the
Departments of Beni and Pando, up to the border with Brazil. The
7
-The principal measures used have been DDT sprayings, which in the
Guayaramerin area have been applied quarterly. They have been supplemented
with anti-larval measures and radical treatment of the cases detected. In
this region, quinine was used to treat P. falciparum cases resistant to chloroquine.
The program was affected by financial and operational problems. Foremost
among the technical problems was P. falciparum resistance, the migratory movements in various localities in the malarious areas, and the planned and spontaneous land settlement schemes, with the building of make-shift dwellings that afford their inhabitants little protection.
BRAZIL
In 1982, malaria incidence rose 12% over that of the previous year and the annual parasite incidence increased from 3.8% to 4.1% on a year to year
basis. The situation in the area in the maintenance phase was kept unchanged
compared with the previous year, thanks to appropriate epidemiological
surveillance activities for preventing the reintroduction of the disease. In
the area in the consolidation phase, the number of cases detected decreased although the number of blood slides examined in the area also decreased
relative to 1981. The area in the attack phase is that which is giving the
greatest problems to the malaria program of this country. The program
expanded its surveillance area when sprayings were suspended in an area of
116,642 Km2 with 826,972 inhabitants in the state of Bahia. In contrast,
because of the epidemiological conditions in the Amazon area, it was necessary
to shift areas of 1.6 million Km2 with 3.7 million inhabitants back to the
attack phase with DDT and to include them in regular coverage.
In the Amazon region, which is characterized by equatorial transmission conditions (throughout the year, because of the climatology and tropical ecology), the largest number of cases was detected (214,650 or 79% of the
total for the country). The epidemiological stratification carried out there
showed that only 60 municipalities produced the majority of cases (175,356). The API of this region was 16% while in the short-term eradication area it amounted to 0.2%.
Efforts to carry out insecticide operations have encountered many
obstacles. It is believed that, in the first cycle of 1982, only 66.3% of the
target was reached and in the second cycle, only 73.7%. Since the resources
are not sufficient for comprehensive coverage, the program continues to make efforts to stratify the areas epidemiologically and to apply attack measure
based on a more selective epidemiological approach. The country planned to
eliminate four residual foci located in Goias, Mato Grosso do Sul, Parana and
Santa Catarina. In 1982, in those foci, 312 autochthonous cases were
detected, of which 241 came from the first focus mentioned (Goias). Some
active foci were detected in the consolidation area of Piaui, Ceara, Rio de
Janeiro, Sao Paulo and Mato Grosso do Sul. These foci, 10 in all, were
promptly treated. In the area in the maintenance phase in the state of
8
-The common causes in the north of the country are the intense migratory movements of populations moving to occupy new territory in Amazonia and
logistic and administrative difficulties. In addition, P. falciparum
resistance to the drugs available is widespread.
COLOMBIA
Colombia has been carrying out a stratification process in order to enable it to make more efficient use of its resources, which are insufficient
for comprehensive coverage. At present the malarious areas of the country are
divided into low, medium and high risk areas. The last-mentioned covers
696,000 Km2 and contains 3,290,636 inhabitants (about 72% of the national malarious area and approximately 22.5% of its inhabitants, respectively). The persistence of transmission in this area is due to various factors, especially socio-economic and cultural factors, that hamper the eradication of malaria in
the short-term. In this area there are zones containing 378,327 inhabitants
in which activities have been interrupted because of concern for the safety of
field personnel. The areas with technico-operational problems account for
51.1% of the cases detected in the high risk areas, which in turn represented 45.7% of the total number of cases in the country.
Colombia has no areas in the maintenance phase. The areas in the
consolidation phase succeeded in maintaining their epidemiological situation without major change compared with 1981, despite the fact that the number of
cases detected in the area in this phase was rather high (7,925). But it was
in the attack phase area in which there was the greatest increase in
transmission: 70,301 cases in 1982 as opposed to 52,998 cases in the previous
year.
In Colombia, as in Brazil, P. falciparum is resistant to
4-aminoquinolines and the intense urban-rural and rural-urban migratory
movement constantly endangers the disease-free areas and those in which
progress has been made in recent years. There is also strong resistance to
DDT sprayings in some regions even though the vectors still remain susceptible to the insecticide.
COSTA RICA
Efforts to prevent the reintroduction of malaria have been successful, thanks to an adequate system of epidemiological surveillance and the priority
the government continues to assign to the program. At year-end 1982, 29 out
of the 36 cantons that make up the original malarious area of the country were still in the consolidation stage (584,427 inhabitants or 86.3% of the
population of the malarious area). The 110 cases detected during the year
- 9
-However, of continuing concern is the constant importation of cases as a
result of migrations, principally from Central American countries. In 1982,
out of a total of 110 cases, 58 were classified as imported; of these, 29
came from Nicaragua, 16 from El Salvador, 3 from Honduras, 9 from Guatemala, and 1 from Bolivia.
The financing assigned to the program in 1982 was considered adequate.
DOMINICAN REPUBLIC
Transmission increased in 1982, although the API still remains below 1%. However, the cases detected were scattered throughout almost the entire
country, which indicates that the disease is spreading. The problem is more
serious in the areas in which sugarcane and rice are cultivated.
The progress made by the program in past years, when it succeeded in shifting more than 97% of the population of the malarious area into the
maintenance phase, has stopped and deterioration has begun. The area in the
maintenance phase is endangered by the constant penetration of cases so that the threat of reestablisment of transmission is real if its advances are not
halted. Of the total number of cases detected in 1982 (4,654), 3,308 or 73%
came from the area in the maintenance phase. The attack measures planned for
dealing with active foci of transmission could not be carried out because of
lack of financial resources. The total number of houses sprayed during the
year only amounted to 16.7% of the target (48,000). Since August, insecticide
activities have been suspended because of lack of material. Some biological
control activities with larvivorous fish and the physical reduction of some breeding places were carried out but the results could not be evaluated.
A. Albimanus is DDT resistant in the Province of Dajabon. P. falciparum
is sensitive to the 4-aminoquinolines.
ECUADOR
There was a 14.6% increase in the number of malaria cases relative to the
previous year. The Province of Esmeraldas continues to be the principal focus
of transmission, although the measures taken there began to be reflected in a
slight reduction in the number of cases relative to 1981 (18%). In contrast,
transmission increased sharply in the Provinces of Rios (69%), Manabi (30%)
and Guayas (218%). The area in the consolidation phase succeeded in
maintaining its situation without major deterioration although there was also a slight increase in the number of cases registered (4,070 or 3.4% of the
total positivity). Sprayings with insecticides, DDT for the most part and in
- 10
-unprotected. Fiscal constraints on imports have hampered the purchase of
the necessary materials for the execution of operations, including not only insecticides but also antimalarial drugs and other materials and
equipment. The SNEM was reorganized and became responsible for the
control of other vector-borne diseases, in particular Aedes aegypti
control and malaria vaccination in the jungle area of the country. With
the assistance of TRD/WHO a study on the prevalence Chagas disease to be
carried out by the SNEM in 1983 was designed. In addition, the SNEM is
responding to the request of the provincial directors of health for vector control.
EL SALVADOR
The total number of cases registered in 1982 (86,202) decreased slightly relative to 1981 (93,187), although the number of slides collected also decreased so that the slide positive rate (SPR) remained
the same (25.3% and 24.5% respectively). The socio-political conditions
of the country in recent years have prevented it from carrying out a
comprehensive control program. It is believed that field operations for
the control of transmission can be carried out in 25% of the national
malarious area. However, it is interesting to note that the activities
being undertaken with the participation of the community and the general health services, in particular the collection of blood slides and drug distribution, continue to be carried out in all the months of the year
despite the special circumstances the country is experiencing. The
measures adopted consisted basically in active and passive case
detection, presumptive and radical treatment of patients, and some
activities aimed at controlling the vector in its aquatic phase. In
1982, the program was reviewed by a committee that included national and PAHO technical personnel; it suggested that consideration be given to the use of DDT sprayings in areas in which the vector is susceptible, despite the fact that its use has been abolished in the national territory.
FRENCH GUIANA
The number of cases increased from 769 in 1981 to 1,143 in 1982, especially in the area in the attack phase, in which there was a 100%
increase. The areas in the consolidation and maintenance phases remained
stationary. The situation has been of great concern to the authorities
who, together with PAHO, held a border meeting of almost all the countries of the northern region of South America (Venezuela, Guyana,
Suriname, French Guiana and Brazil). Its purpose was to discuss the
epidemiological problems the country is facing, especially that of
migratory movements through its border areas, which are steadily
increasing. A large number of the cases detected (161) were classified
as imported, Brazil being the country of origin of most of them. Of
- 11
-GUATEMALA
The total number of cases detected in Guatemala increased relative
to the previous year, from 67,994 in 1981 to 77,375 in 1982. The
resistance of the vector to several insecticides is compounded by political and social problems, which is why it was nezessary to
temporarily interrupt malaria control activities in some areas;
nevertheless, it was found possible to resume them during the year and to
carry out the program based fundamentally on the use of various
alternative insecticides that are applied in the Pacific area for the most part: deltamethrin in 6 monthly applications on an experimental
basis in some farm areas; fenitrothion, applied every 4 months as well
as chlorophoxim; DDT is used in the ecological area of the north, where the vector continues to be susceptible to this insecticide. The national authorities report that these measures have made it possible to halt the upward trend in the number of cases observed in the period during which
work was suspended. The budget of the program was reduced by 26% with
effect from April 1982.
GUYANA
There was a slight decrease in the number of cases detected in 1982
relative to 1981. However, there was also a decrease in the number of
slides collected for parasitological examination and, as a result, the
positivity indexes remained virtually the same (1.8% and 1.9%
respectively in 1981 and 1982).
There was no major deterioration during the year in the area in the
maintenance phase. The program received increased assistance from the
general health services and voluntary collaborators (community
participation) both in the collection of blood slides and in the distribution of drugs. However, the difficulties that have persisted for several years such as the lack of sufficient financing and therefore means of transportation and communications and now a serious reduction in the trained personnel for executing field operations continue to be
unsolved. PAHO increased its assistance by assigning a consultant to the
country.
HAITI
Haiti is a country most seriously affected by malaria in the
Caribbean subregion. The number of cases increased in 1982 (65,354)
relative to 1981 (46,703).
- 12
-The country prepared an action plan for the period 1982-1986; and the first year was devoted to the programming of activities, review of
strategies, and training of personnel. The principal insecticides used
in 1982 was fenitrothion at a dose of 2 g/m2, although in the first
half of the year it was only applied in one operational area; in the other two areas selective drug distribution was carried out and protected
a total of 386,662 persons. The program encountered many difficulties
during the year, especially financial difficulties. It is believed that
it only protected 13% of the population resident in the malarious area
(625,325 persons out of a total of 4,642,277). PAHO maintains a group of
advisers in this country; in addition Haiti receives financial and
technical assistance from the Government of the United States (AID) for
its malaria program. The Government of Japan has also contributed to the
operations of the program under a bilateral agreement.
HONDURAS
The number of cases increased in 1982 relative to a previous year. It should be noted that the number of slides collected increased by more
than 100,000 relative to 1981. The period of greatest transmission was
the early months of the year (January-May). There was a 260% increase
relative to the same period in the previous year. This made it necessary
to take emergency measures, especially in the region of Choluteca, where
the vector is resistant to DDT, propoxur, and malathion. The measures
included the use of fenitrothion, and the fortnightly mass distribution of drugs in 12 cycles, which dramatically reduced the positivity rate. The country has begun to reorganize its malaria program and hopes to enlist greater participation of all the components of the health sector, of other sectors, and of the community.
MEXICO
The new strategy adopted in 1981, based on the stratification of the malarious area in order to select localities with higher transmission for
the execution of attack measures, continued to be used in 1982.
Intra-domiciliary sprayings were made only in localities with cases in the past 3 years and in the current year; this measure was supplemented by the administration of drugs in areas in the attack phase and the
radical treatment of cases and their epidemological contacts. Mass
treatments consisted in a single dose of chloroquine and primaquine each month for 3 months to selected populations because of their high malaria
incidence.
The areas in the maintenance phase succeeded in keeping themselves free of the disease during the year; in the area in the consolidation phase, there was an increase in the number of cases from 3,701 in 1981 to
4,928 in 1982. The increase in the number of cases in the area in the
attack phase is explained in part by improved case detection. Although
13
-Budgetary and financial problems were compounded by problems caused by extensive migratory movements of sick population from national and Central American foci of residual malaria.
The Malaria Research Center in the southeast of the country (Tapachula), which operates with the assistance of PAHO, continues to
conduct a number of studies designed to improve control methods,
especially in areas in which A. albimanus resistance to DDT and other insecticides normally used by the program predominates.
The program is being reorganized by means of a process of
administrative and technical decentralization which incorporates each operational zone into the coordinated health services of each of the states of the country.
NICARAGUA
This country showed some progress in its epidemiological situation in 1982 since the number of cases fell from 17,434 in 1981 to 15,601 in
1982. The parasite incidence was 5.5 cases per one thousand population
in 1982. The program continues to base its field operations on intra
domiciliary sprayings, radical treatment of patients, and mass drug
distribution in problem localities. Anti-larval measures and space
sprayings (ULV) have been somewhat reduced in selected areas and
localities.
The principal difficulties facing the program are the lack of sufficient resources and foreign exchange for the necessary imports as well as the expansion of vector resistance to insecticides.
PANAMA
In this country the epidemiological situation remained unchanged
relative to that of 1981. The total number of cases was only 334 in
comparison with 340 in the previous year. No deterioration occurred in
the area in the consolidation phase thanks to the efficient surveillance measures taken by the country and the priority the Government continues to assign to the malaria program.
A matter of continuing concern to the national authorities is the intense migration of workers in the Darien area, a highly receptive area
to which many persons infected move from the neighboring country. For
spraying its residual foci, the country had been using the insecticide
propoxur but because of its high cost, it is being replaced by
fenitrothion. Fenitrothion was used on an experimental basis in the
- 14
-PARAGUAY
It has kept the epidemiological situation of malaria under control as a result of the priority the Government assigns to surveillance measures for keeping the areas in which transmission was interrupted free
from the disease. In the country there are areas in the maintenance and
consolidation phases in which the situation is still entirely
satisfactory. There were no cases in the area in the consolidation phase
in which 38,965 blood slides were collected. Of a total number of 66
cases detected, 26 imported cases were registered in the area in the maintenance phase; in the Department of Boqueron, Paraguayan Chaco, a
small epidemic outbreak that produced 26 autochthonous cases was
reported; another 6 autochthonous cases were detected in the eastern region. The attack measures employed continued to be based on the use of
DDT to which the principal vector A. darlingi is still susceptible. The
19 cases of P. falciparum malaria discovered and classified as imported
proved sensitive to the drugs with which they were treated
(chloroquine-primaquine). The intense migratory movement in the area of
influence of the Itaipu dam is of concern to the authorities and requires them to step up surveillance measures.
PERU
The epidemiological situation of malaria in Peru worsened in 1982, up to September 1982, a total of 14,613 were recorded, compared to 14,812
for 1981 as a whole. In earlier years it had succeeded in shifting 43%
of its malarious area into the consolidation and maintenance phases. Transmission was reestablished in the area in the consolidation phase; up
to September, a total of 6,072 cases was registered. The number of cases
in the area in the attack phase increased from 7,500 in 1981 to 8,110 (up
to September). During this period a total of 85,204 blood slides were
examined compared with 189,164 in 1981, which shows that the situation is
more serious. The program continues to be incorporated into the general
health services whose activities consists in collecting blood slides,
administering treatments, and taking some emergency measures. This
situation is a matter of concern to the Government, which is taking measures to implement the recommendations of a group that reviewed the
program. The group consisted of national and PAHO officials. Prospects
for reactivating the program are excellent because of the interest of the health authorities in solving the serious epidemiological, ecological and socio-economic problems.
SURINAME
There has been no change in the situation relative to the previous
year. In 1982, a total of 2,805 cases were detected (2,479 in 1981),
almost all in the areas in the attack phase (2,453). There was no
serious deterioration in the areas in the consolidation and maintenance
phase. The epidemiological situation in the Upper Suriname river
improved significantly.
15
-VENEZUELA
At present the area in which malaria has been eradicated contains
10.3 million inhabitants. The area still infected (attack phase)
contains 651,729 inhabitants (1982) and is divided into two parts: the
western part where there are technical problems that hamper eradication, principally the outdoor resting of the vector, A. nufez-tovari, which easily eludes residual action insecticides; and the southern part, where the vector is A. darlingi, and there are malaria foci considered to be unapproachable because of the presence of nomadic indians, dwelling units with a small sprayable surface, and migratory movements of human groups
connected with mining activities.
In 1982, a total of 245,770 blood slides were collected and examined in the country; of these 112,092 were from the area in the attack phase
and 133,678 from the rest of the country. The number of cases of malaria
detected amounted to 4,306, of which 1,993 were classified as
autochthonous and introduced. However, it is believed that the number of
autochthonous and introduced cases was higher, about 3,000 cases, if cases imported from the areas in the attack and maintenance phases in
which some foci exists, are added. In the previous year a total of 3,377
cases were detected throughout the country.
The increase in the number of cases registered in 1982 compared with 1981 affected the country as a whole although the western focus of the
area in the attack phase was most affected. In addition, a relatively
high number of cases were imported into the originally malaria-free area of the state of Tachira on the border with Colombia.
In the western malarious focus, the increase in the number of cases
was attributed to: (i) cases imported from abroad, which represents 40%
of the cases for the area as a whole; and (ii) increase in local malaria transmission as a result of failure to carry out the anti-malaria
activities planned because of the lack of equipment, contractual
problems, execution of hydraulic and agricultural works that had
increased the number and mobility of the population to be covered by the
program's activities. Of the cases registered in this area, 60% are
attributed to local transmission.
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-II. PROBLEMS AFFECTING THE PROGRESS OF THE PROGRAM
The number of malaria cases registered has been steadily increasing in the past ten years (1973-1982) and reached 709,255 in 1982, the
highest ever recorded. This increase, however, is limited to certain
countries or even certain regions within a country. The magnitude and
nature of the problems causing this increase differ from one country to another but the countries classified in the groups presented in Table 5 have certain common features.
Group I. Surveillance activities indicate that transmission has not been reestablished and that the countries are free of malaria. So far no
serious problem has been reported. In this group, the number of cases
decreased from 1,599 in 1981 to 972 in 1982.
Group II. As a rule, in the countries in subgroup A it has been
possible to eliminate the foci of infection and to prevent the
reestablishment of transmission. The exception was French Guiana, where
the number of cases increased from 769 in 1981 to 1,143 in 1982, largely because of the pressure of external migrations and movement of workers coming from malarious areas.
In the three countries in subgroup B, the situation reported in the previous year continued to worsen. In Belize, this is connected with the migration of the population and the lack of human and financial resources
and of health structures to ensure effective control. Guyana reported a
smaller number of cases but it should be explained that surveillance activities were reduced because of the lack of means of transportation
and personnel. This problem affected Rupununi and the northwestern
region. In the Dominican Republic there was also an increase in the
number of cases and a greater dispersion of the foci, primarily because of the movements of workers coming from malarious areas and insufficient surveillance and control activities.
Group III. In the five countries of this group, parts of the
malarious areas are either in the consolidation phase, maintenance phase
or both. The malaria situation in these areas has been maintained
without serious problems. The areas in which malaria transmission has
increased are in the attack phase.
In addition to the problems mentioned, labor problems are frequent and hinder the normal conduct of operations.
Group IV. In the 1960's, the eight countries in this group made
considerable progress in their malaria programs. With the exception of
Haiti, all had areas which at one time or another were in the
consolidation or maintenance phase or both. However, this satisfactory
situation deteriorated because of the emergence of serious technical, administrative and financial problems at the end of the 1960's and the beginning of the 1970's, so much so that the eight countries have lost
almost all of, what they had gained. The principal problems are
17
-a) Technical Problems
The physiological resistance of A. albimanus to the
insecticides available has been the principal problem in El
Salvador, Guatemala, Honduras, Nicaragua and Haiti. On the
Pacific coast of the four countries of Central America, the vector is resistant to almost all the insecticides recommended
for the malaria program. Without this highly effective and
economical measure, these countries had to use more costly and less effective control measures such as larviciding, source
reduction operations, and mass drug administration. The
results obtained have been a limited protection of certain
population groups or a temporary relief from epidemic
situations without significant changes in the general malaria
picture. In Haiti, the vector is resistant to DDT.
A. albimanus resistance to DDT was also reported in Panama (Canal Zone and Comarca de San Blas) and in Costa Rica (Pacific
Coast) but this is not an important problem because
transmission had already been interrupted as a result of
propoxur sprayings and distribution of antimalarial drugs. In
the northwestern border region of the Dominican Republic
(Dajabon), A. albimanus increased its resistance to DDT.
Previously this did not present a problem because the area was
virtually exempt from malaria. However, in recent years
transmission has increased and therefore poses a serious threat
for the future. In the southern states of Mexico, along the
Balsas river, the vector A. pseudopunctipennis has become DDT
resistant. Susceptibility tests made in southern Mexico showed
that the average mortality is much higher with chlorphoxim and propoxur than with malathion and fenitrothion.
The behavioristic resistance (evasive behavior) of A.
nufeztovari to DDT in western Venezuela and in eastern Colombia continued to be a problem resulting in the persistance of
transmission. It is recommended that new trials be carried out
with insecticides that have some fumigant effect, under a well designed research program.
P. falciparum resistance to 4-aminoquinolines is a serious problem in some areas of countries in South America, especially
Colombia and Brazil. However, it will probably not become an
insuperable problem in the malaria eradication program because some alternative drugs that are effective are still available, and if the vector continues to be susceptible and responds to
the spraying of houses with residual insecticides.
These data underline the importance for the program of the
- 18
-susceptibility of the parasites to anti-malarial drugs as well as the review of the therapeutic schedules used to reduce the selective pressure of resistant strains and to obtain the best
possible results through the activities of the program. The
same applies to the vectors and their response to insecticides.
b) Problems characteristic of socio-economic development areas
Throughout the American continent socio-economic development
projects are being actively promoted. Many of these projects
are located in areas that coincide with highly receptive
zones. With the arrival in the recently opened up areas of
migrants and workers who live in make-shift housing, serious
outbreaks of malaria usually occur. Indeed, many areas or
places in which malaria is highly endemic today were
uninhabited 10 or 15 years ago. This phenomenon is very common
in Brazil and Colombia. It is not always possible to prevent
outbreaks because the location of the settlements are not
always known to the malaria service and furthermore the
allocation of funds, if any, is usually very delayed.
c) Problems connected with socio-political and human behavioral
problems
These problems have played an increasingly important role in the execution of the program in recent years. They are very difficult to quantify but in many countries they are the
principal factors in the reduction of operational and
supervisory capacities and have resulted in inadequate coverage
and poor quality of field work. Inadequate remuneration leads
to the loss of professional personnel, particularly those well qualified, and furthermore labor problems frequently paralyze
field operations. These socio-political and behavioral
problems are sometimes far more serious than some of the other problems mentioned.
d) Problems related to financing
Graph I shows the funds invested in the malaria programs in the
Americas since 1957. The allocations have clearly been
gradually increasing during the past 25 years. However, in
actual fact, that increase has been offset by the increasing costs of personnel, supplies, equipment and transportation, and by the additional requirements arising in the new malarious
areas such as recent land settlement areas. In addition, in
some countries the emergence of technical problems such as
vector resistance to DDT and parasite resistance to
antimalarial drugs makes it necessary to use more expensive complementary or alternative measures.
- 19
-III. RESEARCH
PAHO has continued to support research in immunology, chemotherapy and entomology, vector control, epidemiology and social sciences applied to malaria.
In addition it collaborates with the countries in epidemiological stratification, and feasibility studies and evaluation of control methods
adapted to local situations.
A. Trials with insecticides and vector pathogens
In the Malaria Research Center (CIP) of the malaria control program of Mexico, studies have been carried out, in collaboration with PAHO/WHO, on the susceptibility of A. albimanus in various areas (cotton, banana
and costal areas). The average mortality of the vector from chlorphoxim
is 99-100% in all three areas. Propoxur mortality is 97% on the coast
and 74% and 61% in the cotton and banana growing regions, respectively. Malathion mortality is high in the coastal area (83%), in the cotton
growing area (66%), and in the banana growing area (72%). The lowest
mortality was obtained with fenitrothion in the cotton (52%) and banana growing areas (64%) and the coastal areas (57%), the range being wider in the cotton growing area (19-71%).
With emphasis on the method of evaluation based on the behavior of A. albimanus and the mortality rates due to contact with the insecticide
chlorphoxim, three cycles of 50% wettable powder in a dose of 2g/m2
were applied in the interior of 172 houses in a locality situated to the north west of the municipality of Tapachula, Mexico. A gradual decrease in the relative mortality of the dead mosquitoes captured in curtain
traps and dead mosquitoes found on the floor was noted. The degree of
intoxication of the mosquitoes appears to be related to the places in
which they settle and rest before a blood meal. The degree of
intoxication is also related to the time of contact with treated
surfaces, as shown by recapture studies of marked mosquitoes. The
densities of mosquitoes biting men inside and outside the house did not decrease with the insecticide, but there were decreases in the rates of pregnant females following the first application. The conclusion reached was that a mortality of 80% or more can be expected inside the houses, following the third spraying, both of fed and fasting mosquitoes during a period of up to 16 weeks after the spraying.
However, 65% of the vectors showed a tendency towards outside feeding which means that the insecticides acts on less than 50% of the
antropophilic population. It is necessary to investigate the behavior of
20
-The Brazilian Public Health Campaigns Authority (SUCAM), in
cooperation with PAHO/WHO, is conducting studies on experimental houses constructed in accordance with the Tapari model, which has no walls, in
the settlements of workers in the rural or jungle areas. The Tapari
consists of a palm roof with or without a plastic sheet to protect it
against the sun and the rain. Jute (sisal or henequen) curtains that can
be moved and dismantled have been added to them. These curtains/wall
were impregnated with various insecticides (DDT, malathion, MGK, DDVP, decamethrine, propoxur) for the purpose, of evaluating an adequate animal bait (buffalo), its greater attraction for vector anopholines having been
previously evaluated. In addition, arbors were built with piled-up
vegetation to form shelters from mosquitoes, which at the same time act
as barriers. This innovative method for the entomological evaluation of
the action of insecticides should be extended to field studies in the
areas where transmission exists. Investigations with deltamethrine
(WHO-1998) are continuing in Guatemala; it caused the same mortality with
doses of 0.025 and 0.05 g/m2. In a dose of 0.025 it was applied in 307
localities with 43,000 cases in six-monthly sprayings with promising results.
In Haiti, it was demonstrated that a dose of 2 g/m2 of
fenitrothion is effective and therefore it is planned to expand the application to other areas to evaluate this insecticide with smaller doses.
In Ecuador fenitrothion was tested in 41 localities with 3,200 cases
in the Province of Esmeraldas, in six monthly cycles of 2.0 g/m2. The
final results are not yet available.
Furthermore, the CIP in Mexico is carrying out studies on the basic biological and ecological characteristics of anopholine breeding places
in order to gain a better understanding of the habitat of the aquatic
phases, their nutrition, pathogens, parasites and predators. Studies
have also been begun to evaluate the effectiveness of Bacillus
thuringiensis serotype H-14.
In the Ariari-Guejar area of Colombia, larval investigations are being carried out in breeding places, following application of B.t.i., in
order to determine the entomological impact.
The CIP in Mexico, in cooperation with project AMR-0901, is carrying out studies on the vector ability of various lines of A. albimanus, using physical methods of separation of sporozoites by density gradients and
immunological methods by means of monoclonal antibodies against
circumsporozoitic proteins.
In Ariari-Guejar, Colombia, entomo-epidemiological studies have been begun to examine the bloodlymph of adult anopheles of various species to
determine the presence of sporozoites by means of the method of
- 21
-Also in Colombia, in collaboration with the University of Davis, California, the feasibility of producing Romanomermis culicivorax in different colonies of Anopheles, Culex and Aedes is being studied.
B. Malaria Chemotherapy
In Brazil, Phase III of the clinical studies on the efficacy,
tolerance and pharmacodynamics of mefloquine is about to end. This drug
has been shown to be efficacious in the treatment of P. falciparum infections resistant to chloroquine and to a combination of pyrimethamine and sulfadoxine.
In Nicaragua, a 3-day treatment with chloroquine and primaquine was
administered to a total of 1,892,746 persons in November 4-6, 1981. The
results are being analyzed to evaluate the feasibility, efficacy and
tolerance of the treatment. Mass antimalaria drug treatment carried out
in 1981 reduced the positivity indexes both of P. vivax and of P.
falciparum. Provisional data indicate that the impact on P. vivax lasted
for 4 months whereas P. falciparum prevalence continued to decline for 3
months more. The immediate results suggest that mass antimalaria drug
administration prevented the occurrence of more than 9,000 cases and that about 75% of the population participated in the training and organization of antimalarial activities.
In Brazil, Colombia, Ecuador and Panama, evaluations of in vitro test have shown that about 80% of the P. falciparum specimens studied were resistant to chloroquine.
Up to 1982, the observations appear to indicate that P. falciparum is susceptible to chloroquine in the countries of Central America, Mexico, Haiti and the Dominican Republic.
However, in Guatemala, Haiti and Nicaragua the results of in vitro test indicate a lower degree of susceptibility of P. falciparum to chloroquine than in earlier years.
In collaboration with the University of New Mexico a workshop on the
epidemiology and control of P. falciparum infections was held. It
reviewed the current situation of drug-resistant malaria and studied the possibility of establishing a system of monitoring P. falciparum response to drugs; it also discussed the mechanisms for coordinating operations for the control of the disease and analyzed the principal areas of practical knowledge required for the development of applied research programs.
In Colombia, in vivo studies were undertaken to identify the
response of P. falciparum and to compare the efficacy of chloroquine and
amodiaquine in different epidemiological strata. Simultaneously, studies
22
-C. Social Sciences and Malaria
In the Dominican Republic a study was begun of the social variables
that influence the transmission and control of malaria. Furthermore,
greater importance is being assigned in the malaria program to an analysis of ways and means of strengthening surveillance systems with a
view to obtaining better planning, coordination, organization of
resources, and execution of control measures.
In the School of Medicine of the University of Antioquia, Colombia, studies were undertaken to construct a socio-medical research model of malaria, and a retrospective study on malaria and housing is being conducted.
The Center for Economic Development Studies of the School of Economics of the University of Los Andes, Colombia, is carrying out a survey to determine a micro-economic model of malaria. A survey of cases and controls was conducted, the information was processed and an analysis of the data begun.
In Guatemala, the evaluation of the system of voluntary
collaborators for epidemiological surveillance and treatment of malaria cases is continuing.
D. Information Systems
The malaria programs have expressed interest in improving data
processing in order to enable them better to analyze data. Brazil,
Colombia, Guatemala, Haiti, Honduras, Mexico and Nicaragua are conducting operational studies to define the redesign of the technical information system of the malaria program.
E. Malaria Immunology
The National Health Institute of Bogota, Colombia, is continuing its studies designed to evaluate the efficacy of P. falciparum merozoite
antigens cultivated in vitro with or without adjuvants for the
immunization of Aotus monkeys. Attempts are being made to breed these
monkeys in captivity. The Evandro Chagas Institute in Belem, Brazil, is
conducting studies on the biochemical antigenic and genetic
characterization of strains of P. falciparum. In the University of New
York, very promising results have been obtained in purifying
circumsporozoitic antigens and progress has been made in developing simple techniques for detecting antigens, in the vector and antibodies against sporozoites in the human population.
As part of the project for the development of immunizing agents, it
has become necessary to identify antigens that produce functional
23
-With the financial support of the Swedish Medical Research Council, the Swedish Agency for Cooperation and Research with developing countries '(SAREC) and the Rockefeller Foundation, the Department of Immunobiology
of the National University of Colombia is conducting studies on
regulating the immune response in P. falciparum infections. The
synthesis of DNA induced in vitro in lymphocytes of patients suffering from acute P. falciparum malaria was investigated.
IV. PERSONNEL TRAINING
The malaria erradication program was organized in the countries of the Americas when the disease was still endemic at the end of the 1950's
(1956-1959). The program was initially successful and by 1969 had
succeeded in interrupting transmission and reaching the consolidation or maintenance phases in originally malarious areas in which two-thirds of
the population of the original malarious area were living. Following the
progress obtained in the first ten years, the situation remained
stationary, which led the World Health Assembly to adopt Resolution WHA.22.39 (24 July, 1969) which inter alia recognized:
- The role played by socio-economic, financial, administrative
and operational factors, as well as the inadequacy of the basic health services, in the failures recorded in the implementation of the world malaria eradication program;
- That it was imperative to adapt the strategy to the local
epidemiological situation and the resources available in the countries affected;
- That it was necessary to encourage and step-up
multidisciplinary research, including the biological sciences, in order to simplify and improve methods of malaria eradication and the implementation of the program.
The considerations and recommendations mentioned are still valid for the global strategy of the malaria program and are more topical in view of Resolution WHA.32.30, which adopted the global strategy of "Health for
all by the year 2000". In that resolution the Assembly endorsed the
Report and the Declaration of the International Conference on Primary Health Care that met in Alma Alta, Soviet Union, in 1978.
