Gastrointestinal helminths of waterfowl (Anatidae: Anatinae) in the Lerma marshes of central Mexico: Some pathological aspects.

Gastrointestinal helminths of migratory waterfowl can cause several lesions that may affect the health and even the survival of their hosts. As part of an ongoing project that aims to inventory the helminth species that infect this group of birds, as well as the histopathologic lesion they cause, a total of 200 digestive tracts of nine species of anatid birds (Spatula discors, S. cyanoptera, S. clypeata, Mareca strepera, M. americana, Anas crecca, A. acuta, A. platyrhynchos diazi, and Oxyura jamaicensis) were collected in the Atarasquillo marsh of Lerma, in the State of Mexico. The present work had a twofold goal: to determine the taxonomic identity of the helminth species present in waterfowl as well as their infection levels and to describe the lesions caused by gastrointestinal parasites in migratory and resident anatids in Atarasquillo marsh, State of Mexico. The specimens were examined using routine helminthological and histopathological techniques. A total of 23 helminths were identified: six trematodes (Zygocotyle lunata, Notocotylus triserialis, Notocotylus seineti, Psilochasmus oxyurus, Australapatemon burti and Cotylurus magniacetabulus), four cestodes (Cloacotaenia megalops, Fimbriaria fasciolaris, Gatrotaenia cygni and Diorchis sp.), eleven nematodes (Echinuria uncinata, Tetrameres sp., Tetrameres fissispina, Hystrichis sp., Streptocara sp., Amidostomum sp., Epomidiostomum uncinatum, Capillaria sp., Capillaria contorta, Ascaridia sp. and Heterakis sp.) and two acanthocephalans (Pseudocorynosoma constrictum and Filicollis sp.). At the proventriculus level, Echinuria uncinata caused the most severe lesions; in the gizzard, Amidostomum sp. and E. uncinatum produced hemorrhages and necrosis. Finally, the main lesions found in the intestine (necrosis, heterophilic granulomas and the formation of lumps on the serosa) were caused by the implantation of the acanthocephalans' proboscis. Eleven species of gastrointestinal helminths found are new records for the Lerma marshes, as well as the first record in Mexico of the nematode Capillaria contorta and the acanthocephalan Filicollis sp.