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Research Summary - 4

Exploring the species diversity of gastrointestinal nematodes in western Canadian beef cattle

Date/Time: 9/14/2019    9:00
Author: Eranga  De Seram
Clinic: University
City, State, ZIP: Saskatoon, SK  S7N 5B4

Exploring the species diversity of gastrointestinal nematodes in western Canadian beef cattle

E. De Seram, BVSc, MSc 1 ; E. Redman, PhD 2 ; C. de Queiroz, DVM, MSc 2 ; J. Campbell, DVSc, DVM 1 ; C. Pollock, DVM, MSc 3 ; J. Gilleard, BVSc,PhD, DipACVM, MRCVS 2 ;
1Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, S7N 5B4, Canada
2Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, T2N 4Z6, Canada
3Merck Animal Health, Kirkland, QC, H9H 4M7, Canada

Introduction:

The objectives of this study were to explore herd level species diversity of gastrointestinal nematode (GIN) communities in calves from western Canada and the effects of anthelmintic treatment on their relative species abundance in feedlot steers. Coinfection with multiple GIN species is common in cattle. Exploring the GIN diversity is important to understand parasite epidemiology and particularly the response to control programs; however, research is limited in Canadian beef cattle.

Materials and Methods:

Forty-three western Canadian cow-calf operations from 4 provinces were enrolled in the cross-sectional study of investigating herd level GIN species diversity. Individual fresh fecal samples were collected from 15-20 calves (n = 844 in total) from each herd between November 2016 and February 2017. Information on deworming status of sampled calves was provided by producers at fecal sample submission. To determine the effects of anthelmintic treatment on the relative species abundance of GIN, a randomized controlled trial was conducted in a research feedlot facility. Two hundred and thirty-four auction market-derived, weaned, fall-placed steers were equally assigned to three treatment groups: control; injectable ivermectin (IVM); combined treatment of injectable IVM and oral fenbendazole. Each group had replicates of 6 pens. Pre- and 14 days post-treatment fecal samples were collected from individual feedlot steers. To isolate third stage GIN larvae from individual coprocultures, fecal samples from calves and steers were pooled by herd and by pen, respectively. Species and relative proportions of GIN larvae were determined using a next generation deep amplicon ITS-2 rDNA nemabiome sequencing.

Results:

Ostertagia ostertagi was the predominant GIN species in most cow-calf operations while C. oncophora was the second most abundant species. Interestingly, in most of the dewormed cow-calf herds, the relative abundance of C. punctata or C. oncophora was greater than that of other GIN species. The relative abundance of C. punctata was noticeably higher in one province (Manitoba) compared to that of other provinces. In feedlot steers, O. ostertagi was predominant in the control group pre- and post-treatment and in the IVM group pre-treatment. However, C. oncophora was predominant in the IVM group post-treatment. There was a marked increase in the relative proportion of H. placei in steers post-IVM treatment. No larvae were recovered from post-treated steers that received the combined IVM and fenbendazole treatment.

Significance:

These results confirm that O. ostertagi is generally the most abundant GIN in the western Canadian beef operations sampled here. The regional and post-deworming predominance of C. punctata is noteworthy and must be explored further. Cooperia punctata is traditionally more abundant in more southern, tropical regions and has the potential for significant production impacts. Differing anthelmintic susceptibility is likely an important risk factor for the GIN species diversity in these cattle from western Canada.


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