Mosquito abundance in a Dirofilaria immitis hotspot in the eastern state of Rio de Janeiro, Brazil

Abstract

Coastal lowlands in the state of Rio de Janeiro, Brazil, support high numbers of heartworm-infected dogs. Microfilariae of heartworm need to be ingested by a potencial mosquito vector in order to develop into infective larvae and infect a new host. Ochlerotatus taeniorhynchus and Ochlerotatus scapularis are the primary vector species in the coastal lowlands of metropolitan Rio de Janeiro; thus, the aim of this study was to investigate whether these two species were abundant enough at the heartworm hotspot in the eastern area of the state to be important to the local parasite's life cycle. The study was conducted at the Massambaba sandbank (22°55'45″S;42°18'51″W), where canine heartworm prevalence was 53.1%. Mosquitoes were captured monthly using two traps with CO₂, as well as eventual human landing. A total of 6118 mosquitoes of 16 species were collected. Ochlerotatus taeniorhynchus (37.5%), Culex quinquefasciatus (19.3%), Oc. scapularis (18.2%), and Coquillettidia sp. (10.5%) were the most abundant species. The monthly variation in frequency was marked for Oc. scapularis and Cx. quinquefasciatus and steadier for Oc. taeniorhynchus and Coquillettidia sp. The abundance of the two Ochlerotatus species reaffirms that they are the primary natural vectors for D. immitis in the coastal Rio de Janeiro state lowlands.

Keywords: Heartworm; Mosquito vector; Mosquito-borne parasite.