Digestive tract nematode infections in non-native invasive American mink with the first molecular identification of Molineus patens

Abstract

Parasites may negatively affect hosts condition, especially when infection intensity is high. Species introduced to a new habitat are often less exposed to a parasite pressure but may accumulate parasites in time. American mink (Neovison vison) introduced to Europe, Asia, and South America is an example of such invasive species. We analysed nematode prevalence and digestive tract infection intensity in 796 feral American mink from Poland. The analyses were performed separately for stomach, duodenum, small intestine and large intestine. Parasite species identification was performed using molecular methods based on highly conserved nuclear 18S rRNA gene and supplemented with morphological analysis. In total, we collected 26,852 nematodes and 98.6% of them were isolated from mink stomachs. We found positive association between infection intensity in stomach and other parts of digestive tract. Nematode prevalence was estimated at 63.8% and average infection intensity per one American mink at 52.9 (range from 1 to 1118). If the stomach results were theoretically and intentionally omitted the prevalence was 5 times lower (12.7%) and infection intensity 14 times lower (3.7; range 1-50). We identified two nematode species in digestive tracts of American mink: Aonchotheca putorii and Molineus patens. The 18S rRNA gene sequence of Molineus patens has been reported for the first time. The results showed that Aonchotheca putorii is a dominating nematode in the invasive American mink and that it inhabits stomach intensively and preferably.

Keywords: Aonchotheca putorii; Digestive tract; Genetical methods; Molineus patens; Neovison vison.

Graphical abstract

Fig. 1

Relation between the number of nematodes in the stomach of American mink and the number of nematodes in other parts of the digestive tract (duodenum, small intestine, and large intestine).

Fig. 2

A phylogram based on the small subunit of 18S rRNA nuclear gene fragments for the 58 sequences obtained from the parasites isolated from different parts of the American mink digestive tract: s – stomach; d – duodenum; si – small intestine (bold – Aonchtheca putorii, navy blue and bold – Molineus patens) and sequences achieved from GeneBank (http://www.ncbi.nlm.nih.gov/) (in italics) of the other 8 Trichuridae species (phylum Nematoda). All newly achieved sequences are in bold (details in Appendix 1, Fig. S2). The evolutionary relationships of the taxa were implied using the maximum likelihood estimation method (Tamura and Nei, 1993) embedded in MEGA6 software (Tamura et al., 2013). The tree with the highest log likelihood (−1262.9129) is shown. The evolutionary distances were computed using the maximum composite likelihood method (Tamura et al., 2004) and are expressed as a number of base substitutions per site. All positions containing gaps and missing data were eliminated. There were a total of 456 positions in the final dataset.