New records of helminth parasites of nine species of waterfowl in Mexico, and a checklist of the helminth fauna of Anatidae occurring in Mexican wetlands.

Wild and domestic populations of waterfowl garner economic benefits, as they are hunted for human consumption or as a recreational activity. Waterfowl migrate to their wintering grounds in Mexican wetlands where habitat conditions are more favourable. In this study, we present a list of helminth species sampled from the gastrointestinal tract of 59 wild birds belonging to the family Anatidae in three localities of Mexico, and a checklist of the helminth parasite fauna of the members of the family in the whole country, built from literature records. After helminthological examination, 25 taxa were identified: eight trematodes; four cestodes; 12 nematodes; and one acanthocephalan. Obtained records dated from 1943 to 2019. Our literature search yielded 563 records corresponding to 95 parasite taxa: 38 trematodes, 24 cestodes, 23 nematodes and ten acanthocephalans. In Mexico, 17 anatid species have been studied for helminths. Records correspond to 55 locations from 20 Mexican states. An insight gained from the collated literature and recent records was that trematodes represent the most diverse parasite group in anatids in Mexico. We briefly discuss that the information about helminths parasitizing waterfowl will be useful for understanding the effect of habitat loss and pollution of wetlands where migratory birds spend the breeding season, for addressing ecological programs aimed to guarantee the health and conservation of North American migratory birds or the effect of bird migration in the composition of the helminth parasite communities, and for freshwater biologists interested in the understanding of freshwater ecosystem health.

Tziminema unachi n. gen., n. sp. (Nematoda: Strongylidae: Strongylinae) parasite of Baird's tapir Tapirus bairdii from Mexico.

A new genus and species of nematode, Tziminema unachi n. gen., n. sp. is described from the caecum and colon of Baird's tapir Tapirus bairdii (Gill, 1865), found dead in the Reserva de la Biósfera El Triunfo, Chiapas State, in the Neotropical realm of Mexico. Tziminema n. gen. differs from the other nine genera included in the Strongylinae by two main characteristics: having 7-9 posteriorly directed tooth-like structures at the anterior end of the buccal capsule, and the external surface of the buccal capsule being heavily striated. Phylogenetic analyses of the DNA sequences of the mitochondrial cytochrome c oxidase and nuclear DNA, including a partial sequence of the internal transcribed spacer 1, 5.8S and a partial sequence of the internal transcribed spacer 2 of the new taxon, confirmed its inclusion in Strongylinae and its rank as a new genus.

Records of the bird capillariid nematode Ornithocapillaria appendiculata (Freitas, 1933) n. comb. from freshwater fishes in Mexico, with remarks on Capillaria patzcuarensis Osorio-Sarabia et al., 1986.

Re-examination of capillariid specimens collected from the freshwater fish Chirostoma estor Jordan from Lake Pátzcuaro in 1985-1986 and deposited as paratypes of Capillaria patzcuarensis Osorio-Sarabia, Pérez-Ponce de León & Salgado-Maldonado, 1986 showed that their morphology was in contradiction with the description of this species and, in fact, they could be identified as the species originally described as C. appendiculata Freitas, 1933 from cormorants Phalacrocorax brasilianus (Gm.) in Brazil; conspecific capillariid specimens were later recorded from Chirostoma estor and Cyprinus carpio L. from the same locality. This species and two others are transferred to Ornithocapillaria Barus & Sergeeva, 1990 as O. appendiculata (Freitas, 1933) n. comb., O. carbonis (Dubinin & Dubinina, 1940) n. comb., and O. phalacrocoraxi (Borgarenko, 1975) n. comb. This is the first record of O. appendiculata in Mexico. Its occurrence in fishes suggests that these nematodes may be acquired by their fish hosts accidentally while feeding on cormorant excrement containing mature nematodes. A female capillariid collected from one of 110 Chirostoma estor examined from this locality in April, 1998 was identified as Capillaria patzcuarensis. Both capillariid species are briefly described and illustrated.

Experimental infection of Contracaecum multipapillatum (Nematoda: Anisakinae) from Mexico in the domestic cat.

Juveniles of Contracaecum multipapillatum infected the Mayan cichlid (Cichlasoma urophthalmus) and adults infected the olivaceous cormorant (Phalacrocorax olivaceus) and the great egret (Casmerodius albus) in the coastal lagoon at Celestun, State of Yucatan, Mexico. All are new host records, and, even though the geographic locality record of Mexico for the species has not been published, unidentified but presumably conspecific specimens have been reported from there. When juveniles of C. multipapillatum were fed to a kitten, but not rats, ducks, or chickens, they developed into adults. Measurements and morphological data are provided on the specimens from the kitten. Development of an avian ascaridoid in the intestine of a mammal increases the potential of this widespread species to infect other mammals, including humans.