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% in the city of Niteroi. Nevertheless it is rarely detected in cats
(0.8%) from the same state. Dogs are the 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%) were: Aedes taeniorhynchus (30% of
the total catch; with the peak in May/June); Culex quinquefasciatus
(22.5%; August/October); Aedes scapularis (19.4%; August,
October/November and January) and Culex declarator (17%;
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.
