Avaliação das preferências alimentares das fêmeas de Anopheles darlingi e Anopheles aquasalis em Belém, Pará, por meio de Provas de precipitina (Publicado originalmente em 1949)

Abstract

Two types of experiments were simultaneously conducted in Belém, State of Pará, Brazil, for the purpose of determining, by means of precipitin tests, the host preference of the females of Anopheles darlingi and A. aquasalis, the main local vectors of Malaria. In one series of experiments the authors used mosquitoes collected inside houses. In another series, laboratory-raised specimens were released in a large cage where they remained overnight in the presence of eight different baits: man, dog, cat, pig, sheep, cow, horse and chicken. Anti-sera were prepared according to Kolmer and Boerner’s (1941) scheme. In the performance of the precipitin tests, Rice and Barber’s (1935) technique was followed with slight modifications. Results obtained showed that both A. darlingi and A. aquasalis are capable of feeding on all species of animals used as baits. In the tests made with mosquitoes captured inside houses the anthropophilic index was very high for both species of anophelines. Next to man, preference was given to dogs and few specimens had fed on cows and horses. On the other hand, in the tests made with mosquitoes released in the cage, A. darlingi showed a marked preference for the human bait, whereas A. aquasalis appeared to have no special liking for man. Next to man, A. darlingi fed more frequently on the cow and horse, and these two baits rated prior to man in the preferences of A. aquasalis. The dog was seldom seeked as a source of food. The percentages of tests positive for the blood of the different hosts were as follows. Over 91 percent of the tests were positive for a single host, but there were tests positive for two and even three hosts. A small number of tests using A. oswaldoi and A. intermedius – species which are common in Belém but have no domestic habits and no importance in the epidemiology of Malaria – revealed that the great majority of the specimens from the cage fed on the cow and a smaller number on the horse; a limited number fed on man, although tests made with the few females of these species captured inside houses were all positive for human blood. The experiments performed allowed the authors to confirm the fact that, in determining host preferences by means of precipitin tests, the use of mosquitoes caught inside houses may furnish misleading results, whereas more accurate data are obtained with specimens raised in the laboratory and placed in an enclosure along with different baits.