Hyperparasitism in Amblyomma rotundatum (Acari: Ixodidae).

In the present study, we report a case of hyperparasitism in Amblyomma rotundatum. During examination of live ticks immediately after collecting them from Boa constrictor snakes held in a reptile facility in Mossoró, RN, northeastern Brazil, 1 unengorged tick female was seen attached to the venter of a partially engorged female. The hypostome and chelicerae of the unengorged female had penetrated the integument of the partially engorged female to the level of the basis capitulli and the palps were splayed outward. To our knowledge, we present the second report of hyperparasitism for the genus Amblyomma.

[Canine heartworm on São Luís Island, Northeastern Brazil: a potential zoonosis]. / Dirofilariose canina na Ilha de São Luís, Nordeste do Brasil: uma zoonose potencial.

A survey on the prevalence of canine heartworm was conducted in 1, 495 dogs from Maranhão Island, State of Maranhão, Northeastern Brazil, from 1991 to 1994, by testing for microfilariae in blood. Of the total, 1,358 (12.8% of which were infected) were dogs with no known history; they included 1,265 homeless animals (10.3% with microfilariae) and 93 kept by owners at the time the survey was conducted (37.8% of which were infected). Prevalence is high among dogs captured and/or living along the seashore. Examples of such high coastal prevalence rates were found in Olho d'Agua and Calhau (46% and 43%, respectively). The search for microfilariae in blood samples of 137 exclusively domiciliary dogs with a known history showed that 43% of these animals were infected, confirming transmission of heartworm on the island. This was the first survey formally published on canine dirofilariasis in Northeastern Brazil. Since D. immitis is infective to man and prevalence of the parasite is high, particularly along the coast of Maranhão Island, human cases of dirofilariasis may be expected. Local physicians should consider this parasite among the possible causes of solitary lesions in humans living in this area.

[Mosquitoes potential vectors of canine heartworm in the Northeast Region from Brazil]. / Mosquitos vetores potenciais de dirofilariose canina na Região Nordeste do Brasil.

INTRODUCTION: In some coastal districts of São Luís, capital of the state of Maranhão, Brazil, the prevalence of Dirofilaria immitis is more than 40% in house dogs. Natural potential vectors, as found in other areas of Northeastern Brazil, are unknown. The aim of this study was to identify probable vectors of the disease. METHODS: Mosquito catches were performed at a coastal, district Olho d'Agua, in S. Luís, to look for local potential vectors. Captures were carried out monthly, from March 1996 to May 1997, outdoors, having a man and a dog as baits. Mosquitoes were dissected for D. immitis larvae. RESULTS: A total of 1,738 mosquitoes belonging to 11 species were collected. Culex quinquefasciatus, the only species collected every month, was more frequently in the dry season. It accounted for 54.5% of the total, followed by Aedes albopictus (20. 3%), Ae. scapularis (11%) and Ae. taeniorhynchus (11%). D. immitis larvae were detected in 0.1% of the Cx. quinquefasciatus dissected (L3 in the Malpighian tubules) and 0.5% of the Ae. taeniorhynchus (L2 in the Malpighian tubules). CONCLUSION: Ae. taeniorhynchus and Cx. quinquefasciatus are considered natural potential vectors of the canine heartworm in São Luís. The role of Cx. quinquefasciatus as primary vector of D. immitis, however, needs further evaluation.

Vector competence of Culex quinquefasciatus say from different regions of Brazil to Dirofilaria immitis.

The vector competence of Culex quinquefasciatus from five localities in Brazil to Dirofilaria immitis was evaluated experimentally. Females from each locality were fed on an infected dog ( approximately 6 microfilariae/microl blood). A sample of blood fed mosquitoes were dissected approximately 1 h after blood meal. These results demonstrated that all had ingested microfilariae (mean, 4.8 to 24.6 microfilariae/mosquito). Fifteen days after the infected blood meal, the infection and infective rates were low in all populations of Cx. quinquefasciatus. The mean number of infective larvae detected in the head and proboscis of these mosquitoes was 1-1.5. The vector efficiency, the number of microfilariae ingested/number of infective larvae, was low for all populations of Cx. quinquefasciatus. However, the survival rate for all populations was high (range 50-75%). The survival rate of Aedes aegypti assayed simultaneously for comparison was low (24.7%), while the vector efficiency was much higher than for Cx. quinquefasciatus. These data suggest that the vector competence of all assayed populations of Cx. quinquefasciatus to D. immitis in Brazil is similar and that this species is a secondary vector due to its low susceptibility. Nevertheless, vector capacity may vary between populations due to differences in biting frequency on dogs that has been reported in Brazil.