Dirofilariasis in Argentina: historical review and first report of Dirofilaria immitis in a natural mosquito population

Argentina is one of the four South American countries where the presence of Dirofilaria immitis is currently confirmed. The objective of this study was to review information on dirofilariasis in the country, and to report our recent findings on mosquito vectors. Since the first report of dogs with unidentified microfilariae in 1926, D. immitis was found in seven provinces and canine prevalence ranged 0-71% at local scale. National prevalence was 8% by the end of the 1980s and current information is available only for Buenos Aires Province. Four pulmonary human infections of D. immitis and one subcutaneous of Dirofilaria sp. were documented. The common coati was the only wild host found, and natural infection in mosquitoes was not previously reported in the country. In our recent mosquito survey in Greater Buenos Aires, we captured and dissected 2380 mosquitoes belonging to 20 species. According to a minimum temperature of 14 degrees C, the potential transmission period (PTP) for D. immitis in Buenos Aires covers 6 months, and the most favourable period (mean temperature above 20 degrees C) takes place from the middle of November to the beginning of April. To identify potential vectors of the parasite, we assessed weekly abundances of mosquito species during those PTP estimated previously. We found two specimens of Culex pipiens and one of Aedes aegypti carrying non-infective stages of D. immitis. These two highly anthropophilic mosquitoes may enhance the role of D. immitis as zoonotic agent in temperate Argentina.