A Febre Maculosa no Brasil, uma revisão sistemática da literatura e o monitoramento da resistência aos acaricidas químicos do vetor Amblyomma cajennense
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2010-04-15
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Universidade Federal de Goiás
Resumo
Brazilian Spotted Fever (BSF) is an acute, infectious, febrile disease of varying
severity, its course ranging from asymptomatic cases to severe clinical forms with a
high lethality rate. The absence of pathognomonic signs in this anthropozoonosis often
results in late diagnosis, thereby serving as a stimulus for investigators to focus their
attention on the weakest link of its epidemiological chain, the vector. In Brazil, the
principal vector of Rickettsia rickettsii, the etiological agent of spotted fever in the New
World, is the ixodid tick Amblyomma cajennense. In the present study, a systematic
literature review was performed to search for publications on the epidemiology of BSF
in the country. With the objective of improving control of the vector, its resistance to the
principal acaricides applied against this tick was monitored. The systematic literature
review was performed by searching for scientific papers dealing with BSF in the
Cochrane Library, LILACS, MEDLINE and SciELO databases, using the keywords
Amblyomma cajennense, Brazilian spotted fever and Rickettsia rickettsii. The search
included articles published in English and Brazilian Portuguese that contained these
keywords. To evaluate susceptibility and resistance to the synthetic acaricides, larvae
had to be obtained from engorged female specimens of A. cajennense collected from
naturally infested horses that had been free of acaricidal residue for at least 45 days, on
farms belonging to five municipalities of the state of Goiás (Caldas Novas, Hidrolândia,
Goiás, Terezópolis and Goiânia). The larvae were exposed to different concentrations
of 12 commercially available acaricidal formulations using the larval packet test (LPT).
The possible development of resistance of adult specimens of A. cajennense to the
pyrethroid deltamethrin, the principal acaricide on the market in Goiás for the control of
ticks in the region, was also evaluated. Unfed adult male and female specimens of A.
Cajennense were collected on leaves of bushes along a nature trail in the municipality
of Caldas Novas, Goiás, Brazil. They were immersed in different concentrations of
deltamethrin and then placed in contact with filter paper impregnated with the
substance. The control groups were exposed to distilled water alone. The bioassays
were performed in quadruplicate at a temperature of 27oC, relative air humidity >80%
and 12-hour light/dark cycles. From the systematic literature review, it was found that there are no records or even systematic studies of BSF in Brazil up to the present
moment and the number of cases reported in the literature is lower than the figures
published by the health surveillance authorities of the Ministry of Health. The data
collected in this review should serve to stimulate investigators to design new studies
and carry out further work, since the distribution of this disease may be more
widespread than is currently supposed. Results from the bioassays showed a mean
percentage of mortality ( ) of 72.6% of the adult specimens after 24 hours of
exposure to the dose of deltamethrin prescribed by the manufacturer, characterizing a
status of resistance to deltamethrin. The males were found to be more susceptible to
this pyrethroid compared to the females. of 82%, 89%, 89.6% and 90% of the
larvae were obtained, respectively, with deltamethrin, cypermethrin + piperonyl
butoxide, amitraz and permethrin, characterizing a status of probable resistance of the
larvae to these acaricides. The combination of cypermethrin with citronellal and with
piperonyl butoxide did not significantly affect the lethal capacity of this pyrethroid
against the larvae of this vector. Significant mortality was not found in the control
groups (p = 0.05). These results encourage new studies to be conducted to develop
alternative methods of integrated control of this vector that would be more effective and
have less harm on the environment.
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Citação
FREITAS, Edméia de Paula e Souza. Spotted Fever in Brazil, a systematic literature review
and monitoring of resistance to chemical acaricides vector Amblyomma cajennense. 2010. 138 f. Dissertação (Mestrado em Ciências da Saúde - Medicina) - Universidade Federal de Goiás, Goiânia, 2010.