One hundred eight rosy-billed pochards, Netta peposaca (Vieillot, 1816), collected in Brazil and Argentina were examined for endoparasites. Collection sites included the municipalities of Santa Vitória do Palmar and Jaguarão, Rio Grande do Sul State, Brazil (wintering site) and Alvear, Corrientes Province, northern Argentina (nesting site). Birds were frozen in dry ice after collection. During necropsy they were categorized according to sex and maturation, either adult or juvenile. The cestode Diploposthe laevis (Bloch) Jacobi, 1896 was found (prevalence 68.5%, mean infection was 2). The mean prevalence of D. laevis in Alvear (25.9%) was higher than found in Jaguarão and Santa Vitória do Palmar, Rio Grande do Sul (19%), and could be related to the nesting site and to the period when the birds may ingest a higher amount of food. This is the first record of a species of the genus Diploposthe in anatideans from South America, and the first record of the species in N. peposaca. Details of the cirrus pouch and vagina were described based on histological sections.
Argentina; Brazil; migratory flyway; nesting site; rosy-billed pochard; wintering site
