High Seroprevalence but Low Rate of Isolation of Toxoplasma gondii from Wild Elk (Cervus Canadensis) in Pennsylvania

Toxoplasma gondii infections are prevalent in most warm-blooded animals worldwide. During the 2018 November hunting season in Pennsylvania, fresh (unfixed, not frozen) samples obtained from 99 harvested elk (Cervus canadensis) were tested for T. gondii infection. Antibodies to T. gondii were detected in 69 of 99 (69.7%) elk tested by the modified agglutination test (MAT, 1:25 cut-off). Tongues and hearts from 16 elk with high MAT titers (>1:200) were bioassayed for T. gondii by inoculation in outbred Swiss Webster (SW) and interferon-gamma gene knockout (KO) mice. Viable T. gondii was isolated from tongues of 2 elk with MAT titers of 1:200 and 1:3,200. Toxoplasma gondii from both isolates were successfully propagated in cell culture. Genetic typing on DNA extracted from culture-derived tachyzoites using the PCR restriction fragment length polymorphism with 10 genetic markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) revealed that both isolates belonged to ToxoDB PCR-RFLP genotype #5 that is widely prevalent in wildlife in the United States. Our results suggest that elk may clear T. gondii organisms from their tissues.

Characterisation of the bacterial community in the gastrointestinal tracts of elk (Cervus canadensis)

The resident bacteria of the gastrointestinal tract (GIT) and the behaviour of these microbes have been poorly characterised in elk as compared to other ruminant animal species such as sheep and cattle. In addition, most microbial community studies of deer gut have focused on rumen or faeces, while other parts of the GIT such as the small and large intestine have received little attention. To address this issue, the present study investigated the diversity of the GIT bacterial community in elk (Cervus canadensis) by 16S rRNA pyrosequencing analysis. Eight distinct GIT segments including the stomach (rumen, omasum, and abomasum), small intestine (duodenum and jejunum), and large intestine (cecum, colon, and rectum) obtained from four elks were examined. We found that bacterial richness and diversity were higher in the stomach and large intestine than in the small intestine (P < 0.05). A total of 733 genera belonging to 26 phyla were distributed throughout elk GITs, with Firmicutes, Bacteroidetes, and Proteobacteria identified as the predominant phyla. In addition, there was spatial heterogeneity in the composition, diversity, and species abundance of microbiota in the GIT (P < 0.0001). To the best of our knowledge, this is the first study to characterise bacterial communities from eight GIT regions of elk by 16S rRNA pyrosequencing.