Managing biosecurity risks from drug-resistant parasites and other diseases in deer

Abstract

Deer are susceptible to infection from various pathogens which are typically associated with livestock. Parasitic helminths, including gastro-intestinal nematodes, are of increasing economic concern in the livestock industry due to the growing issue of anthelmintic drug resistance. Deer can obtain nematodes with anthelmintic resistant alleles, and transmit these to new livestock hosts. Factors which impact a deer populations ability to transmit drug resistant nematodes, and contemporary methods for researching this phenomenon are identified, and the research aims of this thesis are determined (chapter 1). Further, it’s found that deer which reside in landscapes associated with livestock farming, have significantly higher prevalence of the abomasal nematodes Teladorsagia circumcincta, Haemonchus contortus, Trichostrongylus axei and Ostertagia ostertagi (P = 0.01) as highlighted using a meta-analysis (chapter 2). All of these nematode species are prone to contain drug resistant alleles in livestock populations, and infections are often heavily driven by climate. Indeed, climate conditions are found to predict H. contortus infection in sheep and goats (R = 0.67, P = 0.02) as determined by a macro parasite reproductive quotient model (chapter 3). No such relationship was identified between climate and H. contortus or T. circumcincta infection in deer in Europe, indicating that other factors are more important in driving infection in wild hosts. As such, an Agent Based Model was developed for fallow (Dama dama) and roe deer (Capreolus capreolus), to examine the role of host ecology and landscape factors in determining their potential to transmit drug resistant nematodes to sheep pastures in fragmented and non-fragmented landscapes. Across all landscapes, roe deer deposited more eggs which developed to adult nematodes in sheep compared to fallow deer (P < 0.01). Lastly, livestock related abomasal nematodes including T. circumcincta were discovered in wild red deer (Cervus elaphus) on the Isle of Rona (chapter 5), which were in close proximity to pastures containing sheep. Further, the helminth fauna of wild fallow deer was identified in Northern Ireland, with common cervid nematodes being identified such as Spiculopteragia asymmetrica (chapter 5). This work indicates that livestock proximity, and access to livestock pasture, is a key factor influencing the helminth fauna of wild hosts and further, that deer helminth fauna could provide insights into their grazing behaviour which is also relevant to the epidemiology of other pathogens.

Thesis embargoed until 31st July 2026

Date of Award	Jul 2023
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Department of Agriculture, Environment and Rural Affairs
Supervisor	Eric Morgan (Supervisor), Paul Caplat (Supervisor), Siobhán Porter (Supervisor) & Angela Lahuerta-Marin (Supervisor)