Seasonal changes in the levels of anti-Dirofilaria immitis antibodies in an exposed human population.

A prospective follow-up study to define seasonal changes in the level of anti-Dirofilaria immitis antibodies in an exposed human population in Western Spain was conducted. Specific antibodies were detected using an enzymelinked immunosorbent assay (ELISA). Ig M antibodies predominated in Summer, during maximal vector activity, while Ig G rose to a maximum in Winter. The sole risk factor associated with higher optical densities in the ELISA proved to be age, indicating that repeated exposure to the parasite is the rule. It is concluded that, for serodiagnosis the endemic or non-endemic nature of the geographical area and the season of the year should be considered to define the basal level of positivity, and that as well as Ig G, Ig M should always be determined.