Common ground

Over one hundred years ago the wild turkey was a familiar sight in North America. Unregulated hunting and habitat loss decimated their population in Ontario but that has since changed. In 1986, approximately 4,400 wild turkeys were re-introduced, and according to Ontario Ministry of Agriculture, Food and Rural Affairs figures from 2007, that population has reached over 70,000 and continues to grow.

What does this mean to their domestic counterparts, the 8,857,000 members of the same species that comprise the commercial production in Ontario? The turkeys are genetically identical – Meleagris gallopavo silvestris – but how do they relate with regard to disease and mortality?

As a PhD candidate at the department of pathobiology at the Ontario Veterinary College – under the supervision of Nicole Nemeth – Amanda MacDonald has been investigating the wild turkey population. Her goal is to establish a baseline of the current health status of the wild turkey population in Ontario.

There is keen interest from many groups in the province – from hunters and conservationists to farmers – since many shared pathogens affect both wild and domestic birds.

Preliminary work involved a retrospective review of postmortem diagnostic data gathered between 1992 and 2014 for carcasses submitted. This initial study was an important step towards ongoing disease surveillance among all bird populations, especially in the face of ongoing climate and habitat changes.

MacDonald and her research team found that of the 56 wild turkeys examined over a 20-year period in Ontario by the Canadian Wildlife Health Cooperative, 40 birds died from non-infectious causes, mostly emaciation and trauma, with a smaller number succumbing to zinc phosphide toxicosis; with one bird drowning, another dying of frostbite and another dying of unknown causes.

Given the harsh nature of Ontario weather, often with ice encrusted snow conditions that prevent foraging, MacDonald and her co-authors were not surprised by the increased end-of-winter malnutrition. Trauma was mostly attributed to shotgun pellets or collisions, while toxicosis was observed in locations near orchards where the turkeys would have access to rodenticides.

Sixteen (28.6 per cent) of the birds were diagnosed with infectious diseases, mostly viral, with seven of those (12.5 per cent) dying due to avian poxvirus, followed by bacterial infections (five birds, 8.9 per cent) manifested as septicemia related to Pasteurella multocida. Parasites accounted for mortality in three birds (5.4 per cent), mostly Histomonas meleagridis; and one bird died of a fungal infection.

The problem with this retroactive data is the inherent sampling bias, with sick or injured birds most likely to be submitted that may not provide a reflection of the flock in general. In an effort to reach more representative results, for the next stage of her research MacDonald reached out to turkey hunters.

The first legal turkey hunt in Ontario was in the spring of 1987; the hunt has now expanded to include both spring and fall hunts in an effort to sustainably manage wild turkey populations while providing important recreational opportunities. The Ontario Federation of Anglers and Hunters enthusiastically received her request for submission of turkey carcasses in the spring of 2015, quickly providing well over the 150 birds needed for the study.

This research is providing more disease-related information through laboratory testing for potential pathogens as well as GIS mapping and spatial analysis of locations of the tested birds, helping to identify potential hotspots of pathogens in Ontario.

Full analysis of the results will be available later in 2017, but preliminary data shows a 98.7 per cent prevalence of Mycoplasma spp., and 76 per cent prevalence of Eimeria spp., while 69.1 per cent tested positive for E. coli and 66.4 per cent were positive for lymphoproliferative disease virus (LPDV). There was also a small prevalence (5.9 per cent) of reticuloendotheliosis virus (REV) and avian poxvirus (1.3 per cent) but no avian influenza virus or Salmonella were found.

MacDonald hopes that the data will provide baseline disease prevalence information upon which to monitor future disease emergence, contributing to conservation and management strategies that will protect both domestic and wild turkey populations in Ontario.     

This research is funded by the OMAFRA-University of Guelph Research Program partnership with additional support through a student scholarship from the Ontario Federation of Anglers and Hunters.