Susana Rios

Date of Award

January 2014

Document Type


Degree Name

Master of Science (MS)



First Advisor

Vasyl V. Tkach


Avian blood flukes are digeneans belonging to the family Schistosomatidae and inhabit the blood circulatory system of birds. Their life cycle includes an intermediate snail host and a definitive bird host. They are found in representatives of several bird orders, but are most prevalent in waterfowl. North Dakota has a large number of wetlands, which provide important breeding sites for many aquatic birds and serve as stopover sites for migratory birds. The abundance and diversity of bird species that congregate in these wetlands ensures optimal conditions for parasite transmission within and among avian species. However, no study on avian blood flukes has ever been conducted in the state and little to no information is available from the surrounding states/provinces as well. The goals of this study were to investigate the diversity, host associations and distribution of avian schistosomatids in North Dakota. Phylogenetic analysis was also conducted to determine the systematic positioning of blood flukes collected in North Dakota within the Schistosomatidae.

Both the intermediate (snail) and definitive (bird) hosts were surveyed in the state. The larval (cercariae) and adult stages of the parasites were collected from their respective hosts and preserved for morphological and molecular study. Morphological study included measurements of cercariae on temporary mounts, preparing permanent total mounts of adult worms and scanning electron microscopy study of cercariae and adults. Sequences of the partial nuclear ribosomal 28s gene and partial mitochondrial cox1 gene were used in this study for species differentiation and phylogenetic analyses. Sequences obtained in this work were compared with the previously published sequences available in the GenBank database. Intraspecific and

interspecific sequence nucleotide variation was also calculated for all avian schistosomatid species collected in North Dakota. Sequences from North Dakota specimens as well as sequences from all other Schistosomatidae genera available from GenBank were included in a phylogenetic analysis of the Schistosomatidae.

This study focused on the collection of the intermediate snail host to determine the distribution of avian schistosomatid species that may complete their life cycle in the state. Snails were collected from 105 sites throughout the state between May-September of 2013 and screened for the larval stages of parasites. A total of 17,653 snails were collected from six snail genera with an overall infection prevalence of 0.8%. Seven avian schistosomatid species were collected from 4 snail genera. Numerous bird species were also examined and 11 species of avian blood flukes were collected from 22 species of birds. A total of 13 avian schistosomatid species were collected from North Dakota with five species collected from both their intermediate and definitive host. Molecular and morphological analysis also provided evidence for the existence of two Dendritobilharzia species in North America.

These results demonstrated high diversity of avian schistosomatids in North Dakota. Trichobilharzia was the most speciose genus containing 7 of the 13 avian blood fluke species collected in the state. The majority of infected snails belonged to the genera Stagnicola and Lymnaea, which were the most heavily sampled snail genera in this study. Further sampling of other snail genera including members of the families Physidae and Planorbidae may reveal the presence of additional avian schistosomatid species circulating in North Dakota. Further sampling of avian hosts, particularly passerines, in North Dakota may also reveal additional species of blood flukes and additional hosts of a widely distributed species Gigantobilharzia huronensis.