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.