The Occurrence of the Avian Schistosome Allobilharzia Visceralis Kolářová, Rudolfová, Hampl Et Skírnisson, 2006 (schistosomatidae) in the Tundra Swan, Cygnus Columbianus (anatidae), from North America

Twelve tundra swans, Cygnus columbianus (Ord), from Nevada and one from New Mexico were collected and examined for schistosomes. Mature worms, determined as Allobilharzia visceralis, were found in 92% of the swans, in the inferior mesenteric vein of the large intestine and its branches. In 12 cases, there was endophlebitis of the inferior mesenteric vein. The morphology of the worms is consistent with the recently described genus Allobilharzia. Placement in this genus was confirmed also by phylogenetic analysis of nuclear 28S, 18S and, internal transcribed spacer (ITS) ribosomal DNA (rDNA), and mitochondrial cytochrome oxidase I (CO1) sequences. Data further suggest the worms are conspecific with the European A. visceralis, the only described species of the genus and which was found to be the sister taxon to the most diverse avian schistosome genus, Trichobilharzia. This is the first report of a schistosome infection from native swans in North America. Schistosomes have achieved notoriety because they are the etiological agent of the human disease, schistosomiasis, which is caused by 7 of 21 nominal species of Schistosoma; namely S. japonicum, S. malayensis, S mekongi, S. mansoni, S. mattheei, S. intercalatum, S. haematobium, and S. guineensis (see Webster et al. 2006). Although mammalian schistosomes are better known for this reason, avian schistosomes by comparison are much more diverse and widespread (Horák et al. 2002, Brant et al. 2006). For example, Trichobilharzia is the most speciose of the 14 named schistosome genera, with roughly 40 species described, all from birds (Blair and Islam 1983, Horák et al. 2002). Cercariae of Trichobilharzia play a significant role in outbreaks of cercarial dermatitis (swimmer’s itch) in humans across the world, though there are several other schistosome genera that also cause dermatitis (Cort 1950, Jarcho and van Burkalow 1952, Leedom and Short 1981). Recently, investigations of an outbreak of cercarial dermatitis in Iceland led to the discovery of a new genus and species of schistosome, Allobilharzia visceralis Kolářová, Rudolfová, Hampl et Skírnisson, 2006, in Cygnus cygnus whooper swans. This new finding inspired the current study, wherein I examined a swan species native to North America, the tundra swan, Cygnus columbianus columbianus (Ord, 1815). Twelve (5 young of the year) tundra swans, C. c. columbianus, were collected during the hunting season from Stillwater National Wildlife Refuge, Churchill County, Nevada (39°54’N, 118°49’W) on 18–19 November 2005. One young of the year was collected in January 2006 from Lake Avalon, Lea County, New Mexico (32°29’N, 104°15’W). The viscera and nasal tissues were examined for schistosomes between 30 Address for correspondence: S. Brant, University of New Mexico, Department of Biology, 167 Castetter Hall, Albuquerque, New Mexico 87110, USA. Phone: ++1 505 277 2517; Fax: ++1 505 277 0304; E-mail: [email protected] Fig. 1. Egg of Allobilharzia visceralis in Cygnus columbianus from a mass of adults and tissue in the nodule above the inferior mesenteric vein (see Fig. 3). Scale bar = 50 μm. minutes to 6 hours after death, except for the specimen from New Mexico which was previously frozen. Intestinal scrapings and samples from the enlarged large inferior mesenteric vein were examined for eggs, intestinal lesions were photographed, and then worms were teased out and either relaxed and killed in hot water or put into 95% ethanol for subsequent DNA analysis. Attempts were made to hatch eggs. Faeces were rinsed, and then diluted in store bought spring water in an Erlenmeyer flask. The flask was 90% covered from the bottom up, in aluminium foil to expose to light only the top 3 cm of the flask. No miracidia were recovered. Specimens of Dendritobilharzia pulverulenta were collected from Mergus merganser (Cheboygan County, Michigan, August 2005) and Gigantobilharzia huronensis was collected from Agelaius phoeniceus (Albuquerque, Bernalillo County, New Mexico, 1998). Worms were stained in Semichon’s acetocarmine and mounted in Canada balsam on slides for measurements and morphology (Pritchard and Kruse 1982). Voucher specimens of Allobilharzia were deposited in the U.S. National Parasite Collection, Beltsville, Maryland (USNPC# 099527). DNA was extracted from fixed whole worms with the DNeasy Tissue Kit (Qiagen, Valencia, CA, USA) according to manufacturer’s guidelines. Fragments of DNA (internal transcribed spacer – ITS (18S partial sequence; ITS1, 5.8S, ITS2, and 28S partial sequence), 18S and 28S rDNA, and mtDNA cytochrome oxidase 1 (CO1) were amplified by polymerase chain reaction (Takara Ex Taq kit, Takara Biomedicals, Otsu, Japan) and sequenced using previously published primers: ITS: its4, its5 (Dvořák et al. 2002), 3S (Bowles et al. 1995) and 4S (Bowles and McManus 1993), 18S, 28S, and CO1 primers as referenced in Morgan et al. (2003) and Snyder (2004). PCR products were purified with Montage Microcon The information given in this paper was presented at the XI International Congress of Parasitology – ICOPA XI, held in Glasgow, UK, August 6–11, 2006. FOLIA PARASITOLOGICA 54: 99–104, 2007