Mallophagan vectors and the avian filarioids: new subspecies of Pelecitus fulicaeatrae (Nematoda: Filarioidea) in sympatric North American hosts, with development, epizootiology, and pathogenesis of the parasite in Fulica americana (Aves)

Abstract

Subspecies of Pelecitus fulicaeatrae (Diesing, 1861) Lopez-Néyra, 1956 are proposed for the first time. The parasite in the original type host, i.e., the Common Coot (Fulica atra L.) in Great Britain, becomes the nominotypical subspecies, namely Pelecitus fulicaeatrae fulicaeatrae (Diesing, 1861) n.subsp.; it requires further taxonomic study. Subspecies in two sympatric North American hosts are described, and transmission by lice (Mallophaga: Amblycera) is suggested to have played a role in their evolution. Pelecitus fulicaeatrae americanae n.subsp. in the American Coot (Fulica americana Gmelin) has narrower lateral alae at midbody in the male, tighter helical twisting and more rotations in the body of the adult female, and a vulva that tends to be closer to the end of the oesophagus than that of Pelecitus fulicaeatrae grisegenae n.subsp. in the Red-necked Grebe (Podiceps grisegena (Boddaert)). Development of P. f. americanae was followed in experimentally infected American Coots. At 20 days postinfection, worms had migrated to the definitive site in the ankles and developed to the adult stage; these worms were sexually immature and also differed in other morphologic ways from mature specimens. Worms at 210 and 265 d resembled those from wild-caught coots, and females contained microfilariae. Pelecitus f. americanae is reported for the first time in Wisconsin, North Dakota, and California and probably is widespread in coots in North America. Both nesting and wintering coots contained three age-classes of adult female worms (too young to produce microfilariae, producing microfilariae, senescent), suggesting that transmission is not restricted to any particular period during the year. In general, no evidence of infection was apparent upon external examination of intact wild-caught infected coots, whereas ankles of intact wild-caught infected grebes were frequently swollen. Upon internal examination of coots, a visible response to worms was also generally not observed. In a few coots, however, worms were within soft, thin-walled capsules and histologic examination revealed chronic proliferative tenosynovitis.