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

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.

Can P-glycoprotein and ß-tubulin polymorphisms be used as genetic markers of resistance in Dirofilaria immitis from Rio de Janeiro, Brazil?

OBJECTIVE: Dirofilaria immitis, the causative agent of canine heartworm infection, is worldwide the most important filarid to affect domestic dogs. Prevention of this infection is done by macrocyclic lactones, but some reports on the lack of efficacy have been published. Although the actual cause of resistance is unknown, single nucleotide polymorphisms (SNPs) on a P-glycoprotein ABC transporter and ß-tubulin genes have been pointed out as candidates for genetic markers of resistance. We conducted a survey to verify the presence of these suggested genetic markers in microfilariae from 30 naturally infected dogs under macrocyclic lactones treatment living in an endemic area in the state of Rio de Janeiro. RESULTS: The analysis of these specific SNPs demonstrated no sign of polymorphism on the P-glycoprotein loci, while 72 and 48% of the samples were polymorphic to the first and second SNPs on ß-tubulin loci, respectively. This work demonstrates that the P-glycoprotein position 11 and 618 were not polymorphic and, therefore, not suitable as a genetic marker of resistance in Rio de Janeiro whereas both ß-tubulin loci were polimorphic. This work points out the difficulty of finding a universal genetic marker for resistance.

Serological evidence of canine exposure to arthropod-borne pathogens in different landscapes in Rio de Janeiro, Brazil.

Arthropod-borne infections are dependent on environmental conditions, and several combinations of natural and human-related variables play an important role in vector populations as well as the life cycle of agents carried by the arthropods. The top 5 canine arthropod-transmitted agents, Dirofilaria immitis, Leishmania spp., Ehrlichia canis, Anaplasma phagocytophilum, and Borrelia burgdorferi infect unprotected animals without propensity. The purpose of this study was to determine the prevalence of these parasite species in three different landscape settings (sandbanks, plains and mountains) along a 60-km line. During a 6-month period, blood samples were collected from dogs (>12months old) living in the different settings. Prevalence of D. immitis was determined by modified Knott test and ELISA. Prevalence of E. canis, A. phagocytophilum, and B. burgdorferi was determined by ELISA, and Leishmania spp. by ELISA, indirect immunofluorescence, and immunocromatographic assays. D. immitis was most prevalent in the sandbank (68.9%) as well as Leishmania spp. (34.5%), and tick-transmitted agents, A. phagocytophilum and E. canis in the plains (61.7%). B. burgdorferi was not detected. Depending on the resources for arthropods present in regions, dogs are likely to be exposed to different arthropod-borne parasites and should receive preventives tailored to the risk of infection in the region in which the dog resides.