Descriçäo da populaçäo de animais de companhia e epidemiologia da dirofilariose canina em Itacoatiara, município de Niterói, RJ / Description of pet population and canine heartworm epidemiology in Itacoatiara, municipality of Niterói, RJ

Para conhecer a populaçäo de cäes e gatos de Itacoatiara, Niterói, RJ, realizou-se um censo de janeiro a março de 1995. Determinou-se somente a prevalência da infecçäo canina por Dirofilaria immitis no bairro, já que em gatos a microfilaremia é rara e transitória e, portanto, sem importância epidemiológica. Demonstrou-se também a ocorrência de casos autóctones da doença. A populaçäo de animais de companhia em Itacoatiara correspondeu a 36 por cento da populaçäo humana. Estimou-se que no bairro, em 1995, havia 95 cäes infectados por D. immitis e portadores de microfilaremia e, portanto, fonte de infecçäo. A prevalência de casos microfilarêmicos foi 31,7 por cento. Dentre os 91 cäes nascidos, criados e que nunca saíram de Itacoatiara (autóctones), 37,8 por cento eram portadores de microfilárias na circulaçäo.

Potencial vectors of Dirofilaria immitis (Leidy, 1856) in Itacoatiara, oceanic region of Niterói municipality, State of Rio de Janeiro, Brazil

Dirofilaria immitis is a widespread mosquito-borne parasite that causes dirofilariasis, a commonly diagnosed disease of dogs that is rarely reported in cats and humans. A mosquito survey was conducted in Itacoatiara in the State of Rio de Janeiro, from March 1995 to February 1996, using canine, feline and human baits. A total of 3.667 mosquitos were dissected for D. immitis larvae, representing 19 species and 10 genera. From those, Ae. scapularis, Ae. taeniorhynchus, Cx quinquefasciatus, Cx. declator, Cx. saltanensis and Wy. bourrouli were found infected with D. immitis parasites, and among those, only the first three harbored infective larvae. The majority of larvae were found in the Malpighian tubules (889/936), and larval melanization was observed in the two Aedes species. In descending order, the best vector were Ae. scapularis, Ae. taeniorhynchus, and Cx. quinquefasciatus which alternate seasonally in importance. Cx. quinquefasciatus is suggested to be a vector to cats. The potential transmission of D. immitis parasites by these three vectors to man is discussed.

Mosquito frequency and feeding habits in an enzootic canine dirofilariasis area in Niterói, State of Rio de Janeiro, Brazil

Heartworm, a chronic fatal mosquito-borne canine disease, is frequently diagnosed in dogs from the State of Rio de Janeiro, where its prevalence is 29,7 per cent in the city of Niteroi. Nevertheless it is rarely detected in cats (0.8 per cent) from the same state. Dogs are primary source of infection to mosquitoes, because cats either do not demonstrate microfilaremia or it is too low and transient for transmission. A mosquito survey was conducted in Itacoatiara, Niteroi, from March 1995 to February 1996, using canine, feline and human baits. A total of 21 mosquito species (3,888 females) was collected and biting frequency was highest at dusk. The four species collected most frequently (88.9 per cent) were: Aedes taeniorhynchus (30 per cent of the total catch; with the peak in May/June); Culex quinquefasciatus (22,5 per cent; August/October); Aedes scapularis (19,4 per cent; August, October/November and January) and Culex declarator (17 per cent November/January). Human baits were attractive to these species and dogs were significantly more attractive to them than cats. Ae. taeniorhynchus, Cx. quinquefasciatus, Ae. scapularis, Cx. declarator and Cx. nigripalpus are the most likely mosquito species to transmit Dirofilaria immitis parasites to dogs and may transmit the parasite to humans. It is also suggested that the vector to cats belongs to the genus Culex.