COM UNICAÇÃO
OBSERVATIONS ON POTENTIAL TICK VECTORS OF
H U M A N DISEASE IN THE CERRADO REGION
OF CENTRAL BRAZIL
J. C. Knight
R e v is ta d a S o c ie d a d e B r a s ile ir a d e M e d ic in a T r o p ic a l 2 5 ( 2 ) : ] 4 5 - 1 4 6 , a b r - ju n , 1 9 9 2
T h e chagin g e c o lo g y o f the Cerrado region th r o u g h e x t e n s iv e a g r ic u ltu r a l and hum an d evelop m en t3 has meant increasing opportunities for hum an contact w ith natural foci o f zoonotic tick-borne d isease and enhancem ent o f rodent hosts. T he ex isten ce o f L ym e disease has been
postulated in B razil6; infection due to R i c h e t t s i a
r i c h e t t s i i is w ell docum ented2. T he details o f a sm all study m ade betw een M arch and M ay 1991 are reported here, and aspects o f potential vector ep id em io lo g y . T h e results o f arbovirus isolation from ticks brought back to the U .K . w ill be reported elsew here.
C ollection sites included D istrict Federal (1 6 ’S 4 8 ’W ); M am bai, G oias (1 4 ’30"S 4 6 ’W ); and U b era b a , M in as G era is ( 1 9 ’S 4 8 ’W ). T ick abundance in the Cerrado region is h ighly seasonal5
from M ay to a m axim um in July co in cid in g w ith the hot dry period.
A lim ited num ber o f I x o d i d a e s p e c i e s w ere
found livin g in c lo se proxim ity to man, w ith 4 genera, A m b l y o m m c i , A n o c e n t o r , R h i p i c e p h a l u s a n d
B o o p h i l u s represented in the co llectio n (T a b le t).
A n o c e n t o r , rep resen ted b y the s in g le s p e c ie s
A n o c e n t o r n i t e n s (N eum ann) w a s the m ost abundant and made up 66% o f the 1357 ticks collected .
A m b l y o m m a , w ith tw o s p e c ie s A m b l y o m m a
c a j e n n e n s e (Fabricius) and A m b l y o m m a r o t u n d a t u m (K och), made up 6% ; the other genera represented b y 1 sp e c ie s each , R h i p i c e p h a l u s s a n g u i n e u s
(Latereille) and B o o p h i l u s m i c r o p l u s (C anetsrini)
made up 9% and 19% respectively (T able 1). A total o f 273 anim als w ere exam ined for ticks. A very high degree o f hosts p ecificity w a s found. O f
T a b l e 1 - l x o d i d t i c k s c o l l e c t e d .
G enus N ° o f
species
Adult fem ales
Adult males
N ym phs Larvae Total % o f
total
A m b l y o m m a 2 34 7 35 - 76 6
A n o c e n t o r 1 408 28 4 199 6 897 66
R h i p i c e p h a l u s 1 53 64 5 - 122 9
B o o p h i l u s 1 211 41 8 2 2 6 2 19
Total 5 706 396 247 8 1357
and this w as confirm ed w ith a questionnaire (n = 4 8 ) in w h ich local p eop le reported tick num bers rising
V i s i n g r e s e a r c h s t u d e n t , N ú c l e o d e M e d i c i n a T r o p i c a l , U n i v e r s i d a d e d e B r a s í l i a , B r a s í l i a , D F , B r a s il .
R e c e b i d o p a r a p u b l i c a ç ã o e m 2 6 / 1 1 / 9 1 .
77 dogs exam ined, 16 (20% ) w ere found to be infested v / i t h R h i p i c e p a h l u s s a n g u i n e u s ; o f 37 horses
3 4 (9 2 % ) had A n o c e n t o r niten s and 9 (2 4 % ) also had
A m b l y o m m a c a j e n n e n s e : o f 6 7 c o w s (m ixed Zebu
breed 5 0 (75 %) had aB o o p h i l u s m i c r o p l u s load; and
C o m u n ic a ç ã o . K n ig h t J C . O b s e r v a tio n s o n p o te n c ia l lic k v e c to r s o f h u m a n d is e a s e in th e C e r r a d o r e g io n o f c e n tr a l B r a z il. R e v is ta d a S o c ie d a d e B r a s ile ir a d e M e d ic in a T r o p ic a l 2 5 :1 4 5 -1 4 6 , a b r- ju n , 1 992.
o f 2 7 goats exam ined A n o c e n t o r n i t e n s w as present
in 8 (30 % ). W ild anim als exam ined included arm adillo, deer, fo x , fro g, tapir, em u and boa constrictor; o n ly the latter w ere found to have ticks
present w ith heavy infestation o f A m b l y o m m a
r o t u n d a t u m . N o sm all m am m als w ere caught from
a total o f 6 0 trap n igh ts during the study in M am bai. Careful search and partial dem olition o f 19 chicken h ouses revealed n o A rgasidae. Very few free-living or questing ticks w ere encoutered at the tim e o f the study despite extensive flagging and burrow sampling usin g a portable vacuu m suction device.
T he absence o f I x o d e s from the collection is
notable giv en its vector status in L ym e disease, but the presence in Brazil o f at least9 species is recorded1, and sm all mam m al surveys4 reveal ectoparasites in c lu d in g I x o d e s and A m b l y o m m a s p e c i e s on
D e p h i n a e and M u r i d a e
T he risk o f tick bites is seasonal and r e l a t e d to
outdoor activities, w ith farm w orkers and children at m ost apparent risk. L o w biting rates w ere obtained during the relatively in active period during w hich
the study took place, w ith a p o sitiv e history (3 month recall) in only 6% o f those questionned (n = 4 8 ) . C linical m anifestations fo llo w in g tick bites included o n ly local rashes and fever.
In con clusion , there appears to be a lim ited seasonal risk o f tick bites to the hum am population. T h e Cerrado region is rapidly ch an gin g w ith agricultural developm ent and hum am m igration, such that little primary cerrado rem ains. Increased tick-m an contact in areas o f potential zo o n o tic foci exists, but this study revealed that a lim ited num ber o f tick sp ecies appear to occur in clo se proxim ity to man, and these did not include exam ples o f the genu s I x o d e s .
A C K N O W L E D G M E N T S
I w ou ld lik e to thank Dra. V anize M acedo and
Prof. Philip M arsden at the N u cleo de M edicina Tropical. Specim ens w ere confirm ed at the Cidade U niversid ade, Sao Paulo and the Natural H istory M useum , London.
R E FE R E N C E
1. A r g a o H , F o n s e c a F A . N o t a s d e I x o d o l o g i a . V I I I
L i s t a e c h a v e p a r a o s r e p r e s e n t a n t e s d a f a u n a I x o d o l ó g i c a B r a s i l i e i r a . M e m o r i a s d o I n s ti t u t o
O s w a l d o C r u z 5 9 : 1 1 5 - 1 3 0 , 1 9 6 1 .
2 . D i a s E , V i a n n a - M a r t i n s A . S p o t t e d f e v e r in B r a z i l .
A S u m m a r y . T h e A m e r i c a n J o u r n a l o f T r o p i c a l
M e d i c i n e a n d H y g i e n e 1 9 : 1 0 3 - 1 0 8 , 1 9 3 9 .
3 . F u r l e y P A , R a t t e r J A . S o i l r e s o u r c e s a n d p l a n t
c o m m u n i t i e s o f t h e c e n t r a l B r a s i l i a n c e r r a d o a n d
t h e i r d e v e l o p m e n t . J o u r n a l o f B i o g e o g r a p h y 1 5 : 9 7 - 1 0 8 , 1 9 8 8 .
4 M a r e s M A , B r a u n J K , G e t t i n g e r D . O b s e r v a t i o n s o n
t h e d i s t r i b u t i o n a n d e c o l o g y o f t h e m a m m a l s o f t h e
c e r r a d o g r a s s l a n d s o f c e n t r a l B r a z i l . A n n a l s o f
C a r n e g i e M u s e u m 5 8 : 1 - 6 0 , 1 9 8 9 .
5 M i n i s t é r i o d a A g r i c u l t u r a , S e c r e t a r i a N a c i o n a l d e
D e f e n s a A g r o p e c u á r i a , S e c r e t a r i a d e D e f e n s a
S a n i t a r i a A n i m a l . C a r r a p a t o , B e r n e e B i c h e i r a n o
B r a s i l 1 9 8 3 . I m p r e s s o n o : P a n - A m e r i c a n o d e f e b r e
a f t o s a . O r g a n i z a ç ã o P a n - A m e r i c a n a d e S a ú d e -
O r g a n i z a ç ã o M u n d i a l d e S a ú d e , 1 9 8 5 .
6 Y o s h i n a r i N H , S t e e r e A C , C o s s e r m e l l i W . R e v i s ã o
d a B o r r e l i o s e d e L y m e . R e v i s t a d a A s s o c i a ç ã o
M é d i c a B r a s i l e i r a 3 5 : 3 4 - 3 8 , 1 9 8 9 .
