Prevalence of microfilariae in understory birds in the Atlantic Forest of Paraná, Brazil

Microfilariae are the larval stage of filarioid nematodes living in the bloodstream of hosts which became infected after contact with bloodsucker invertebrates. Despite absence of clinical signals, microfilariae may still affect host’s fitness. This study describes the prevalence of microfilaria in Parana’s Atlantic Forest birds. Samplings occurred in Spring 2016 at seven points along an altitudinal gradient of forest with different successional stages at Reserva Natural Guaricica (Antonina/PR). We mist-netted birds for identification, banding and blood sampling. We made blood smears for each individual, latter stained in the lab with GIEMSA solution. We observed 100 fields at 400x magnification to determine microfilarial prevalence and intensity of infection in each smear. We used digital morphometry to acquire each larvae’s length, width, and tail and nerve ring. We analyzed 41 samples of 23 species out of which seven individuals were positive to microfilaria (six species). Two Turdus albicollis individuals had the highest infection intensity (12 and 8%, respectively), followed by T. flavipes (3%), Chiroxiphia caudata, Dendrocincla turdina, Mionectes rufiventris, and Tachyphonus coronatus (1% each). Only three sampling points had infected birds, the one located in a primary forest at 120m asl presenting 57% (n=4) of all infected birds. Larvae length varied from 44.11 to 107.17μm, width from 3.53 to 4.04μm, tail from 17.89 to 28.58μm and nerve ring from 12.19 to 25.7μm. Our results show the highest microfilaria prevalence (17.05%) in Neotropical birds, stimulating future studies to check for any environmental factors’ role on this elevated rate.