A
BSTRACll.S AND REPORTS
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ALARIA CONTROL IN THE AMERICAS:
A CRITICAL ANALYSIS
Malaria Program Objectives
The objectives of any malaria control program should be envisaged chronologically as immediate, intermediate, and ultimate. Putting the last of these first, the zZtimate objective of any malaria control program in the Americas is eradication of the disease. Never- theless, it has been suggested that the effort, knowledge, and resources ap- plied by malariologists and public health workers should not be used to treat only one disease that in many parts of the continent does not rate top prior- ity.
In this vein, the idea that efforts and resources should be concentrated on places where malaria has important re- percussions on socioeconomic development was clearly expressed during the III and IV Meetings of the Directors of the National Malaria Services of the Americas in 1979 and 1983. It was also recommended that programming be started at the local level using the experience of malaria workers and the ca- pacity of the health services for solving local problems. Such action is com- patible with the policy-unanimously embraced by PAHO’S Member Govern-
ments-of making all possible efforts to develop and provide primary health care to all communities.
The interme&.& objective of malaria control relates to areas where malaria eradication does not now appear feasi- ble. That objective is to reduce malaria endemicity, morbidity, and mortality through the following activities:
l assessment of malaria’s socioeconomic
l national development and strengthen-
ing of the education and training capability of all personnel involved in planning and executing training, research, and control programs (including personnel em- ployed in primary health care);
. design, development, implementation, selection, and evaluation of effective and economical control methods;
l strengthening of research capabilities in
malarious countries;
l improvement of intercountry and re-
gional cooperation and coordination regarding malaria research, prevention, surveil- lance, and control activities.
The immediate objectives of malaria control include (a) reduction of malaria transmission levels in epidemic areas, (b) reduction of malaria morbidity and mortality, (c) prevention of the spread of malaria to areas freed of the disease, and (d) assistance with the process of social and economic development in affected areas.
Within the context of these objec- tives, the report of the XVII WHO Expert Committee on Malaria’ proposed a sequence of goals and associated malaria methodologies referred to as “tacti- cal variants.” The goals of these tactical variants, which sought to encompass the major malaria control possibilities, were as follows:
1 reduction and prevention of mortality due
to malaria;
2 reduction and prevention of malaria mor- bidity and mortality, with special attention to reduction of morbidity in high-risk groups;
3 same as variant No. 2, plus reduction of
malaria’s prevalence;
4 countrywide malaria control with the ulti-
mate objective of eradication; keeping countries or areas free from malaria where
eradication has been achieved; and vigilance in countries that are naturally malaria- free but are threatened by the introduction of the disease.
For purposes of reducing or even elim- inating malaria’s impact on the affected human population, a prevention and control program is indispensable. It is generally agreed by all the govern- ments involved that malaria prevention and control programs for individual areas should be based on a national commitment (not merely a health minis- try commitment), as well as upon consideration of prevailing malaria epide- miology, the effectiveness and efficiency of available technologies, the avail- ability of human and financial resources, and each country’s managerial capacity.
’ World Health Organization, WHO Ewpelt Committee on Ma/aria: Seventeenth Report, WHO Technical Report Series, No. 640, Geneva, 1979.
For purposes of practical planning, ex- ecution, and evaluation, the objectives pursued will change with changes in knowledge about conditions of life and human health; changes in the avail- ability and analysis of information about transmission and control determi- nants; and, particularly, changes in the degree of development of basic health services. There is of course a wide spectrum of intervention efforts, but in each specific case the approaches defined and goals set establish the frame- work within which the planner should design a program appropriate for his area, district, country, subregion, or region. In exceptional cases basic health services have malaria prevention and control programs, and in other cases national malaria eradication programs have utilized or developed basic health services. So, in response to such factors, as well as a multitude of oth- ers, the specific malaria control methodology that should best be adopted in different situations will vary with the overall program objective pursued and the related tactical variant employed.
In this regard, it should be noted that all the tactical variants proposed by the XVII WHO Expert Committee on Malaria included reduction of malaria mortality as a common goal. Never- theless, in most of the malarious countries of the Americas, specific malaria mortality and case-fatality ratios are underregistered if not totally ignored. Likewise, reduction of malaria morbidity is a common aim of the second, third, and fourth tactical variants; but prevailing morbidity-in terms of the length and severity of illness episodes as well as the number of ill people-is a variable that has not been sufficiently measured.
Malaria Program Interventions
Among all the various methods for malaria control and the varying results of their application, the rational use of antimalarial medicaments is of paramount importance and is included within the scope of all the tactical variants. The challenge is to administer the right specific treatment to all possible persons infected with plasmodia and to perform an evaluation regarding treatment tolerance and efficacy.
This intervention implies the organi- zation of a very efficient network of primary health workers, public health representatives, voluntary collaborators, and other interested individuals in the community. It also requires reference centers for further analysis of the diagnostic results, handling of possible treatment failures or severe cases, and suitable monitoring of the disease agents’ susceptibility to drugs. To promote the success of malaria chemotherapy in different circumstances, some coun- tries have already started to review their regulations and policies regarding importation, production, distribution, sales, and administration of antima- larial drugs.
infections resistant to that combination, even when a short dose of quinine is added. As an alternative treatment, use has been made of prolonged doses of quinine and/or tetracycline. In addition, clinical tests with mefloquine against falciparum infections have shown the greatest degree of effectiveness combined with good toleration of the drug by the patient.
Recent advances in malaria immunol- ogy have raised the possibility of applying immunizing agents in the not too distant future as a means of diagnosing and controlling the disease.
Regarding other interventions, intra- domiciliary spraying with residual insecticides is still the most dependable (if not the only practical and feasible) attack measure for vector control in the Americas. The trend toward diversifying into integral vector control has re- sulted mainly from serious administrative, operational, and financial diffi- culties.
The resistance of plasmodia to anti- malarial drugs and that of anophelines to insecticides are partially docu- mented, but there is no evidence that these phenomena are impeding the development of malaria prevention and control. The significance of these resistance phenomena for malaria transmission has not yet been documented in the Americas. In Panama, resistance of AnopkeZes aZ&maws to DDT and other insecticides has been demonstrated, as has resistance of E faZcz$anm to chloroquine; and yet, malaria transmission has been interrupted and a stable situation maintained in the whole country, with the exception of three resid- ual foci where other factors have possibly impeded control.
Development of a system for monitor- ing Ff faZcz..amm infections and the resistance of this parasite to antimalarial drugs in the Americas is summarized in PAHO Scientific Publication 471 ,2 the result of a seminar held at the University of New Mexico in 1982.
A PAHOIWHO review of recent vector susceptibility to different compounds3 was presented at WHO/H~~ in Geneva during a November 1985 meeting of the Expert Committee on Resistance of Vectors and Reservoirs of Disease to Pesticides.
Regarding integrated disease control strategies, their design and implementation vary-depending on the type of program for which they were created. In this same vein, the approaches used may vary according to the different diseases and vectors encountered; prevail- ing geographic conditions; the types of housing used; the social, economic, educational, and cultural levels of the affected population; and responses to the measures and resources applied. Above all, however, these approaches tend to relate to the complex situations giving rise to the political decision to adopt them.
’ Pan American Health Organization, Epideemidogy and Con&o/ of Fdczipanrm Ma/a% in the Ameriar. Washington, D.C.. 1984, 48 pp.
J Uribe. Alvaro, Extension and Operational Jmportance of the Resistance of Vectors to Pesticides in the Region of the Americas, WHO mimeographed document, World Health Organization, 1985.
may be implemented as follows:
In general, integrated control schemes
l through popular participation in a
planned program for control of one or more diseases;
l as part of established programs that in-
volve large segments of the population at risk, in which several vectors and more than one disease are being combated; and
l on a national scale, when they are de-
signed for the control or elimination of a single disease.
The Status of Malaria Programs in the Americas
Every year PAHO’s Secretariat presents
a report on the status of malaria programs in the Americas to the Organiza- tion’s Governing Bodies for their consideration. In 1985, in addition to its usual material, an analysis was made of the three following annual malario-
metric indicators during the period between 1959 and 1984:
l the trend of malarial infections, as ex-
pressed by the number of patent parasitemias registered annually per thousand in- habitants in each country. (This is also known as the annual parasite incidence, or
API.)
l the trend in primary health care given
to symptomatic or suspected,malaria cases, as indicated by the number of thick blood film microscopic examinations given annually per hundred inhabitants and the con- comitant administration of at least a single dose of a blood schitontocidal treatment. (This is also known as the annual blood examination rate, or ABER.)
l the trend of vector control coverage, in
terms of the rate of house sprayings per thousand inhabitants.
The denominator used for all three of these calculations was the official United Nations yearly population of each country, as recorded in the United Nations Demogruphic Yearbook. Up to
1983 the malaria program reports classified the countries of the Americas according to the progress achieved against malaria and divided them (on the basis of transmission trends, problems encountered, and the resources avail- able for antimalaria activities) into the four following groups: countries with no evidence of malaria transmission; countries where malaria transmission has been reduced and a favorable situation maintained; countries where ma-
laria is increasing in endemic areas; and countries with serious socioeco- nomic, political, technical, administrative, and financial problems.
Tobago, and Puerto Rico have had very few cases imported from abroad.
Cuba and the United States have reported most of the cases registered in this
group during the period 1980-1984. However, all their cases have been clas- sified as imported, and no local transmission has been demonstrated.
Group II: Countries where malaria transmission has been reduced and a favorable situation maintained. Four countries showed a descending trend in the annual parasite incidence (API) between 1959 and 1984, these being Panama, Costa Rica, Paraguay, and Argentina.
Panama reduced its parasite incidence from 4.91%0 in 1959 to 0.06??10 in 1984. It was also the only country that was able to maintain a substantial spray coverage, spraying over 250 houses annu- ally per thousand population (x = 277.49, SD = 29) between 1962 and
1971.
The annual blood examination rate
(ABER) rose in 1969 from 7 % to 16%, and thereafter (through 1984) was maintained at around 20% per year. In all, 92% of the blood samples were taken by national malaria service personnel. Seventy-six per cent of the 125 malaria cases registered in 1984 were imported from other countries. If one wished to identify an excellent malaria control program, this would be a good one to select.
Costa Rica provided insecticide cover- age that at times exceeded 80 houses per thousand inhabitants; it also re- duced the API from 1.58%0 in 1959 to 0.84%0 in 1964 and from 2.82%0 in
1967 to 0.05%0 in 1982.
In addition, the ABER in Costa Rica has been substantially reduced-from 12.01% in 1969 to 4.14% in 1984. More than 95% of the blood samples collected for malaria diagnosis were taken by national malaria service personnel. However, during the time that the house spraying rate has fallen below 10 houses per thousand inhabitants (since 1980), the number of positive examinations has risen, going from 161 in 1973 to 569 in 1974.
Favorable effects produced in the early 1970s with insecticide coverage were strengthened by two years of intensive mass drug distribution every two weeks in endemic areas of Puntarenas and Nicoya. In 1984, the 569 registered malaria cases were dispersed in 120 locali- ties. Efforts are currently directed toward the most vulnerable localities in the San Carlos and Los Chiles areas. Half of these registered cases were imported from other countries in Central America, most of them (267) from Nicara- gua.
In Paraguay, spraying operations and surveillance activities were very irregular between 1959 and 1967. Great diffi- culties in organizing and implementing vector control activities resulted in
extremely low rates of house spraying between 1962 and 1967. Conse- quently, an API of 23.62Yio was observed in 1967.
Highly efficient vector control opera- tions conducted between 1969 and 1972, with an average house spraying rate of 227.93 houses per thousand inhabitants and radical treatment of all cases and collaterals reduced the API to 0.02960 in 1973. This incidence was main- tained below 0.08%0 between 1974 and 1983.
The opening of new agricultural bor- ders (involving soya and cotton plantations) produced an epidemic of 554 cases in 1984. The national malaria service is currently making a review of its field operations action program. A substantial renewal of supplies and equipment, as well as means of transportation, is needed to prevent worsen- ing of the current situation.
In Argentina, the average API over the last 26 years has been 0.038%0 (SD = 0.05). The highest rates of house spray- ing (an average of 7.38 per thousand inhabitants) were achieved between 1960 and 1963.
A relatively small proportion of the ’ vector control measures planned are actually carried out. Emergency spraying to control outbreaks in Salta and Jujuy provinces is the main activity. Efforts are being made to strengthen epidemiologic surveillance using the national health system.
Group III: Countries where malaria is increasing in endemic areas.
This group includes four South American countries where malaria is increas- ing, mostly in areas with high endemicity, and where effective application of vector control methods is a basic challenge due to the ecology of large areas of tropical forest and savanna in places with new settlements.
Brazil has controlled malaria transmis- sion among two-thirds of its 55.9 million inhabitants exposed to risk in an area of approximately 1.4 million square kilometers. However, this has left about 19 million inhabitants at risk in an area of 5.5 million square kilome- ters. Although the malaria program is concentrating its efforts on priority areas of the states of Rondonia and Par& where 76% of the registered cases are occurring, the API has increased from 0.59%0 (54,644 cases) in 1970 to
2.85%0 (378,257 cases)in 1984.
The highest coverage with insecticides achieved a house spraying rate of 75.14 houses per thousand inhabitants in
1968 (over 40% more than between 1962 and 1977). After 1978, however, the house spraying rate was progressively reduced, declining to 14.24 per thousand inhabitants in 1984. The case-finding system produced uniform and high-level ABERS between 1964 and 1984, with a range of 2.26 % to
Suriname has provided one of the most irregular coverages in this group due to operational problems with its mobile teams in the interior of the country that have caused frequent inter- ruption of malaria control activities. The API has had sharp ups and downs (between 1.53%0 and 12.75%0, the 1984 API being 10.97%0). In general, the
ABER has been surprisingly high, probably because of responsibility assigned to the Medical Mission of the Interior (MEDIZEBS), which has been able to continue field work using the network of health services it has in the malari- ous areas. At present there is a great need to improve the recording of data and epidemiologic evaluation. A comprehensive seroepidemiologic study would be helpful.
French Guiana was able to maintain a relatively low API between 1965 (0.54%0) and 1970 (2.29%0) when house
spraying was sustained at a rate between 202 and 559 houses per thousand inhabitants. When the vector control operation became inconsistent, the API
rose, reaching 16.57%0 in 1982 and remaining over 14%0 in 1984. An in- crease in housing construction near forested areas seems to have been partly responsible for this increase in transmission.
Guyana has also experienced an irreg- ular pattern of vector control operations. The house spraying rate has been relatively low, the highest rates being 25.82 houses per thousand inhabitants in 1961 and 39.68 in 1962. Despite this, there was a marked decline in regis- tered cases between 1966 and 1974 (when the API fell from 1.38%0 to 0.09%0). This has been attributed to use of medicated salt during that pe- riod.
A drastic reduction of funds assigned to the malaria program in 1983 and 1984 made it impossible to carry out programmed activities. The number of reported cases rose by about 43 % in 1984. However, there was little change in the geographic area affected by malaria in 1984 as compared to 1983. More specifically, there was no evi- dence of transmission on the coast, although epidemiologic investigations indicated new foci of transmission downstream from the confluence of the Essequibo and Mazaruni rivers. The country is currently strengthening the intrasectorial links between its malaria control service and regional health teams and is concentrating on development of a passive case detection net- work as a substitute for active case detection activities.
Group IV Countries with serious socioeconomic, political, technical, administrative and financial problems. In the Caribbean subregion, ma- laria was confined to the island of Hispaniola.
In Haiti, the API was reduced from 4.98%0 in 1964 to 0.6%0 in 1968 after an intense distribution of antimalarial drugs_in 1964-1968 combined with an irregular but high rate of house spray- ing (X = 343.23 houses per thousand inhabitants; SD = 133.3) from 1962 to 1966. From 1972 to 1984 vector control operations became extremely irregu- lar, with a general trend toward reduction of house spraying-from 323
system has maintained an ABER of 5.6% to 8.4% from 1970 through 1983,
while the API has increased from O.b%o in 1968 to 12.57%0 in 1982. Since 1983 Haitian authorities have been making efforts to strengthen their volun- tary collaborators’ network by raising the number of personnel from 6,000 to
18,000, to join with the basic health services in organizing a permanent dis- tribution system for antimalarial drugs, and to intensify operational research on various aspects of planning and managing the program as well as on socio- cultural determinants of malaria transmission and control.
In the Dominican Republic transmis- sion was reduced drastically between 1961 and 1968, the API falling from 0.8 1%0 to O.Ol%o. However, as the rate of house spraying was progressively
reduced (from 259 houses per thousand inhabitants in 1965 to 9.8 in 1971, 2.5 in 1976, and 2.1 in 1981) the API rose from O.Ol%o in 1968 to 0.64%0 in 1983, remaining at 0.39%0 in 1984.
Besides experiencing the effects of budgetary constraints, the malaria problem seems to be linked to internal and external population migrations, which have played a dynamic role in the origin of outbreaks in certain areas.
Group IV countries in the Middle American subregion include five countries of Central America (Belize, El Salvador, Guatemala, Honduras, and Nicaragua) and one of Northern America (Mexico).
In Belize, a national malaria eradica- tion program was started in 1957, and by 1963 the whole country had en- tered the consolidation phase. Between 1959 and 1962 an average house spraying rate of 3 19.3 houses per thousand inhabitants (SD = 36.6) was es- tablished, and so the API was reduced from 11.58%0 in 1959 to 0.17%0 in
1963. Low API levels were maintained between 1968 and 1975 when vector control operations were still efficient (the house spraying rates remained be- tween 116 and 174 houses per thousand inhabitants). After 1977, however, the irregular spraying rates (between 50 and 127 houses per thousand inhab- itants) were not high enough to hold down the API, which increased from 1.42%0 in 1976 to 28.72%0 in 1983, while the number of positive localities nationwide rose from 16% of all localities in 1977 to 62% in 1982. Since then, and following approval of a substantial USAID grant, emphasis has been placed on strengthening the malaria program’s operational capacity, information system, field supervision, supervised radical treatment and fol- low-up of malaria cases, and passive case detection. Since 1959 the ABER has included between 10 % and 3 1% of the population.
reached a peak of 25 % in 1969 when the API was reduced to 7.5%0. Since then the ABER has declined, falling from 16.2% in 1970 to 5.0% in 1984.
In Guatemala the API increased from 0.89%0 in 1960 to 4.83%0 in 1966, mainly because of the decrease in house sprayings, which fell from 183.09 houses per thousand inhabitants in 1960 to 61.07 in 1966. After that year, the number of sprayings increased again and the API began to decline, reaching 0.67%0 in 1974, the lowest API registered in 26 years. The case detection system was rather irregular from 1959 to 1969, registering an ABER of 2.92% to 10.50%. Since 1970 the average ABER has been maintained at about 6.6% per year.
Honduras tended to have an increas- ing API between 1960 (2.98%0) and 1971 (17.86%0). A modest increase in house spraying (to 12 1 and 129 houses per thousand population in 1972 and 1973, respectively) led to a lower API of 2.5 l%o in 1974, but an effective level of insecticide coverage was not maintained for long, and the API rose to an average exceeding 10% between 1976 and 1982. In 1977 the National Ma- laria Eradication Service was disbanded and a new Division of Vector Control was created with the goal of integrating antimalaria activities into the general health services. However, antimalaria activities have continued under the di- rect supervision and executive authority of the head of the division; and anti- malaria activities within the general health services have been sporadic and have had no impact. The case detection system has reported a rather irregular
ABER that starts at 3.5% in 1959, goes up to 24.23% in 1968, drops to 4.03 % in 1979, and rises again to 10.68% in 1984.
In Nicaragua the average rate of house spraying was 173 houses per thousand inhabitants between 1959 and 1978 (SD = 89). During a period when propoxur was applied the API dropped from 13.39%0 in 1971 to 2.11%0 in 1973, but coverage could not be main- tained at an effective level. In 1968 heavy emphasis was placed in mass ad- ministration of antimalarial drugs, reducing the API to 4.73%0 in that year (from 9.59%0 in 1967). In 1980 the “brigadistas” of the literacy campaign distributed antimalarial drugs, and in November 1981 there was a national distribution of antimalarial drugs (chloroquine-primaquine) in three days that covered more than 80% of the total population. These measures proba- bly held down the API despite low coverage with insecticides in 1980-1983.
The average ABER has been about 10% per year since 1970.
At present, there is a new approach to effective malaria control that includes new “managerial” organization and decentralization of the decision-making process. The aim of this is to pro- duce a realistic plan of operations that permits better use of available re- sources.
In Mexico, the API gradually rose from
0.0960 in 1959 to 1.21%0 in 1970. The trend then reversed, and the API
declined from 0.82%0 in 1971 to O.Zg%o in 1978 before increasing again from 0.3 l%o in 1979 to 1.1 l%o in 1984. The average house spraying rate per thou- sand population was maintained at 89.85 houses between 1959 and 1971 (SD = 42.61); but it then experienced a major decline-dropping from 91.49 in 1972 to 4.39 in 1984. The productivity of the case detection system also declined substantially, the ABER failing from 5.27 % in 1962 to 1.42 % in
1984.
In 1983 the authorities decided to transform the National Malaria Eradication Commission into a control orga- nization and to gradually incorporate its activities within the public health service in accord with the Government’s policy of decentralization. Within this context, malaria programs are to be established at the state level with participation by various health sector institutions (including Social Security). In 1984, due to budgetary constraints, actions were directed at those areas with the worst epidemiologic situation. Despite the fact that the number of blood samples taken was reduced (from
1.6 million to 1.1 miIlion), the number of detected cases increased (from
75,029 to 85,501).
In Ecuador, a house spraying rate aver- aging 126.51 houses per thousand inhabitants between 1959 and 1966 (SD = 47.9) maintained an average API of 1.36%0 (SD = 0.56) between 1960 and 1967. After the house spraying rate fell to 2.75 houses per thousand inhabitants in 1967, an epidemic situation emerged in 1968 that lasted until 1971, after a higher rate of spraying operations had been resumed. Between 1970 and 1982 the house spraying rate averaged 59.53 houses per thousand inhabitants and the API remained around 1.5%0. However, following the re- duction of house spraying to 3.38 houses per thousand inhabitants in 1982, another epidemic situation emerged in 1983-1984 that raised the API from 1.64%0 in 1982 to 5.58%0 in 1983 and 8.21%0 in 1984.
As of 1984 the number of localities with malaria cases was increasing and 1,273 indigenous cases had been regis- tered in the city of Guayaquil. Active case detection and domiciliary treat- ments had been interrupted. Demands for service were to be met by a passive case detection system employing volunteer workers, the health services, and malaria laboratories. Plans also called for treating the highest possible num- ber of falciparum infections in order to avoid severe and fatal cases.
In Colombia the national malaria pro- gram organized its field operations in a highly efficient manner. However, the house spraying rate was progressively reduced from 157.83 houses per thousand inhabitants in 1959 to 15.62 in 1984. Overall, the API has tended to rise (from 0.28%0 in 1959 to 3.83%0 in 1983). Lack of administrative and budgetary autonomy has limited the development of basic activities, causing successive delays in field operations until the program was totally stopped for four months in 1984. Prospects for 1985 are worse, since the funds assigned are only 50% of the regular amount included in the budget. The ABER, and consequently primary health care related to malaria diagnosis and treatment, never exceeded 4.41% (1968), and since then it has tended to decline, its level being 1.48% in 1984.
The Departmental Health Section in Antioquia has begun an analysis of the malaria problem that involves study of basic parameters-morbidity, mortality, incidence, prevalence, case-fatal- ity ratios, and other biomedical indicators. It is also trying to organize diag- nosis, treatment, and follow-up of patients at different health care levels. This effort could mark the start of a real change in the development of a malaria prevention and control organization in Colombia.
Venezuela has experienced parallel de- clines in the ABER and house spraying-the former declining from 7.87 % in 1961 to 1.38 % in 1983, and the latter falling from 68 houses per thousand inhabitants in 1962 to 11 in 1983. Meanwhile, the API rose from 0.13%0 in 1959 to 2.23%0 in 1971, declined to 0.24%0 in 1981, and rose again to 0.51%0 in 1983 and 0.74%0 in 1984. Worsening of the situation is explained partially by a lack of sufficient financial support for field operations. (Intense recent transmission has been observed in maintenance phase areas of Barinas and Portuguesa states, and malaria outbreaks were detected in Monagas, Sucre, and Bolivar-states that are also in the maintenance phase-up to Septem- ber 1984.)
In Peru the level of house spraying has been low (between 68.7 and 2.3 houses per thousand inhabitants per year) for the past two and a half decades. Vector control has been practiced in limited areas, and some control over vivax malaria transmission was achieved up to 1972, when the API rose to 0.65%0. Some upgrading of vector control operations in 1974 and 1975 had no visible impact, and the API continued to rise-up to 2.03%0 in 1977. No significant increase in vector control opera- tions occurred between 1979 and 1983, and malaria has spread back to prac- tically all of the country’s originally malarious areas.
In Bolivia the number of houses sprayed per thousand inhabitants reached 79.3 in 1959 and then declined. Indeed, since 1963 the house-spraying rate has been very low, averaging be-
tween 10 and 20 houses per thousand inhabitants in most years. Meanwhile, the API has tended to rise, going from 0.20%0 in 1961 to 2.97%0 in 1980.
During 1984 the quality and quantity of malaria control activities dimin- ished, with a consequent worsening of the national epidemiologic situation, as indicated by an increase of the absolute number of cases and wider spread of the disease.
Vector control operations are suffering continuous interruptions because of strikes and lack of funding, and execu- tion of the budget has created serious problems tied to hyperinflation. In
1984, field and office workers actually worked only 42 % of the normal work- ing days.
The severe socioeconomic recession has created a need for a change in the malaria program’s objectives. Specifi- cally, malaria service personnel should direct their attention mainly to execu- tion of specific vector control activities and promotion of training for primary care workers.
Evolution of the Malaria Problem
The increase in malaria morbidity in the malarious areas of the Americas from 5 5.7 cases per 100,000 inhabitants in 1960 to 35 5.3 in 1984 has motivated broad discussions about resurgence of the disease, changes in control methodology, and the need to give new impe- tus to the program. Health administrators, scientists, and politicians all agree that efforts should be concentrated on exploring means for redirecting atten- tion to the situation and solving this problem of major social importance, taking into account the basic principles of health planning in order to obtain the political decisions and technical and financial cooperation needed to exe- cute the best antimalaria measures possible with the available resources at a cost that the countries can afford. Development of control methods and effi- cient measures should be directed toward solution of local problems, with a view to improving health infrastructures and making human and financial resources accessible to the groups at risk, concentrating special efforts on problem areas.
been a lack of effective policies that could positively influence interventions made to modify the social variables that affect the transmission or control of the disease.
As the foregoing suggests, the quan- tity and complexity of variables affecting malaria transmission demand broad knowledge of the relevant social, economic, ecologic, and biomedical factors. Furthermore, the epidemiologic study of malaria, like development and exe- cution of the methodology for malaria control and surveillance, requires ma- jor investments that can only be obtained by means of integrated systems.
It should also be noted that the in- crease in the incidence of malaria cases appears linked to precarious condi- tions of housing, food, and overcrowding. Concentration of people into de- velopment projects; occupation of new lands in tropical areas; channeling of the labor force into agricultural, livestock, and mining activities; opening of new human settlements; and population movements of various kinds all ap- pear to increase the risk of acquiring vector-borne diseases such as malaria. In rural areas with no health infrastructures, and in areas where the develop- ment and utilization of the general health services is very limited and the community has not been organized to participate in antimalarial activities, the situation is typically out of control.
Although migrations could be consid- ered an integral part of the structural changes included in the process of de- velopment , the phenomenon is occurring with great intensity in Latin Amer- ica as a result of various causes related to political, economic, and ecologic crises, the opening of new agricultural frontiers, and living and working con- ditions. In three countries of Central America (El Salvador, Guatemala, and Nicaragua) 0.5 million of the 15 million inhabitants have recently emigrated to Belize, Costa Rica, Honduras, Mexico, Panama, and the United States. Whatever its origin, this migration could have an effect on the emergence of poverty, misery, unhealthy conditions, and disease.
An in-depth assessment should be made of migration’s characteristics and its relation to malaria as a social prob- lem. This is especially true because public income has fallen as a result of the present recession while the population has continued to grow, and the conse- quent imbalance is being worsened by migration toward urban centers. With regard to malaria, the accelerated and disorderly increase in the human pop- ulation moving from endemic areas toward urban and periurban nuclei makes timely diagnosis and treatment difficult and is outstripping the capac- ity of the medical and health services to cope.
At the same time, new settlements as- sociated with development projects have tended to be situated in areas that are highly receptive and vulnerable to malaria. With the arrival of migrants and susceptible or infected workers who settle in precarious conditions, seri- ous epidemics of malaria tend to occur.
In the rural environment, the pres- ence of malarious infections appears closely related to (a) the forms and pro- cesses of agricultural production, (b) their seasonal and climatic variations,
ment and reproduction of the work force, (e) the level of development of scientific and technological innovations and the type of production, and (f) variables that depend on the circulation, mobility, or migration of the hu- man population.
Within this context, the preservation and enrichment or degradation of the ecology are eminently political matters that necessarily have an impact on preservation of flora, fauna, water, and soil resources, and on the living and health conditions of the population. Productive activities affect the environment in densely populated areas; the assault on the environment is directly tied to socioeconomic processes in the areas affected, and the worst damages are seen around the so-called “devel- opment poles” where sharply accelerated growth of productive activities is occurring-particularly growth of the construction industries and expansion of the transportation network. It should also be noted that the damage done to man’s physical surroundings increases markedly when traditional agricul- tural activities are replaced by agroindustry and extensive livestock raising; in this case the rural population is displaced toward urban nuclei-a circum- stance that, in the absence of an adequate infrastructure, encourages the cre- ation of marginal groups.
Social Stratifmtion and Malaria
Malaria transmission depends on defi- nite ecologic factors including characteristics of the human population. One essential ingredient needed for improvement of malaria prevention and con- trol is study of local epidemiology-either in response to identified problems or in connection with possible development of more elaborate plans. And in order to properly type local epidemiologic conditions, it is essential that the social stratification of the community involved be analyzed, so as to elucidate critical social factors influencing malaria patterns.
Stratification as a social phenomenon involves a hierarchic system in which inequalities tend to be institutionalized and passed down from generation to generation. The stratification system is intimately related to economic, political, educational, and other institutions; and changes in the stratification system will lead to changes in these institu- tions. Conversely, changes in other parts of society will produce changes in the stratification system.
This all relates to the malaria problem by way of a hypothesis that different means of production may influence malaria’s epidemiologic profile, and that housing and sanitary conditions (as an expression of socioeconomic status) also affect malaria transmission and control.
In this vein, there appears an urgent need to carry out epidemiologic and operational research on: (a) develop- ment of methodologies to improve the understanding of local stratification systems; (b) identification of receptor mechanisms for development of basic health systems devoted to implementing, strengthening, and improving pri- mary health care; and (c) design of practical ways for creating basic health services, developing malaria prevention and control programs within the for- mat of primary health care strategies, and merging the malaria prevention and control activities with those of the basic health services.
The descriptive epidemiology typi- cally employed in eradication campaigns, which is limited to analysis of ma- laria distribution, does not explain how and why transmission persists. The sort of epidemiologic study desired should include an analysis not only of the biomedical factors involved in transmission, but also of the social, economic, ecologic, cultural, and political factors that affect the population’s living and working conditions, as well as that population’s mobility and distribution. This implies a need for training epidemiology workers in the field of medical sociology.
Finally, considering the magnitude of the malaria problem in the Americas, it appears necessary to create a regional training and research network. Such a network, devoted to developing lead- ership and reorienting existing personnel in the established services, would seek to ensure that training in malaria and its control is required by personnel in the general health services. It would also seek to mobilize mechanisms for coordinating technical cooperation among developing countries and be- tween those countries and developed countries.
Concluding Remarks
It is possible to attribute the resur- gence of malaria to a lack of human and financial resources in the established malaria services. However, there is also a clear need to build a broader con- ceptual framework that will make it possible to understand the interaction between the different variables that influence malaria transmission and af- fect its control in specific situations.
Within this context, it seems reason- able to assume that the levels of health prevailing in a given area are closely
related to levels and types of economic activity, to the resulting distribution of income, and to patterns of economic growth. And it would appear that there are severe restrictions on the development of more effective health pro- grams (including malaria programs) at present if economic circumstances re-
main the same.
It also appears that malaria, like other vector-borne diseases, could constitute a critical obstacle to attaining the goal of Health for All by the Year 2000. At present, many malaria control pro- grams are neither technically nor administratively sound. This circumstance should lead to political and financial decisions based on in-depth knowledge of major factors affecting transmission and control of the disease. However, while health authorities generally express the best intentions about reorient- ing malaria control programs, in the absence of a political decision there is no expectation that the essential changes needed to effect long-term control over malaria through an integrated health system will occur in the near fu- ture .
In order to carry out the careful ongo- ing study of malaria’s presence and spread that are pertinent to its effective control, it is indispensable to strengthen the malaria surveillance system, us- ing all the resources available in the health sector and other development- related sectors. It is also necessary to think about the basic characteristics of the available health services, about the organization that supports them, and about the social effectiveness of their utilization.
P
AHO’S ORIENTATION AND
PROGRAM PRIORITIES IN 1987-1990
This report is based on a document deaZ&g with generaZp0Zicie.s andpriorities for PAHO fecbnical cooperation in
the quadrennizlm 1987- 1990, which was presented by the Director of PAHO
to the XXX Pan American Sanitary Conference in Washington, D. C., in September of this yeaz The Conference adopted ResoZution XXI asking that these program priorities be a&died in the formuZation of PAHO’s program budgetprop0saZ.s andin the devezopment 0fproposaZs for technical coopera- tion by the Member Countries, andzcrging that speciaZ attention be given to improving national heaZth systems in ways that woz4Zd enhance efsorts to at- tain the god of AeaZth for aZZ by the year 2000.
