Diseases of red deer introduced to Patagonia and implications for native ungulates

Abstract

The red deer (Cervus elaphus) invasion in Patagonia has been continuing for nearly a century, with occurrence in all habitats between 34°S and 55°S. Their distribution, movement patterns and locally high densities raise concerns over their potential epidemiological role in maintaining disease reservoirs or transmitting diseases such as foot-and-mouth disease or tuberculosis, with potential severe health and economical impacts at the interface of humans, livestock or native wildlife. Among adult females collected by rifle and radio-collared deer that died naturally, no ectoparasites were found (n = 73). Fasciola hepatica was encountered in three surveys at prevalences ranging from 9% to 50% (n = 108). Taenia ovis krabbei was identified, and Cysticerus tenuicollis was found at a prevalence of 8% (n = 12). Ostertagia sp., Bunostomum sp. and Dictyocaulus sp. had a prevalence of 75%, 25% and 13% (n = 9), respectively. Several gastrointestinal parasites reported at low prevalence in endangered Patagonian huemul (Hippocamelus bisulcus) are common in livestock and considered commensals in domestic ruminants. Sympatry of huemul with livestock is commonplace, whereas with red deer it occurs in <2% of known populations, in which case there were 1.2 red deer, but 25.2 livestock per huemul, making livestock the determining epidemiological factor regarding disease transmission or reservoir. As red deer have been coexisting with livestock for >100 years in Argentina, both red deer and livestock play epidemiological roles for shared diseases. Research, conservation and management efforts should be directed towards livestock herd health programs or restriction of free livestock movements, particularly if diseases are shown to have an impact on recruitment of endangered natives. Livestock are routinely researched and inspected at slaughter and thus provide a proxy for diseases afflicting co-existing ungulates. Testing for antibodies to foot-and-mouth disease viral antigen was negative (n = 41). A tentative diagnosis of mycobacterial infection was based on typical visceral lesions. Antler damage occurred on 73% of shed antlers, with 36% having major breaks of tines and main beams, possibly indicating mineral imbalances. One male had both antlers, including pedicles with portions of frontal, parietal and occipital bones, broken off the skull, causing his death. The prevalence of 0.9% of campylognathia (n = 776) indicates that the disease is unlikely to be inheritable, because the founding stock of 20 animals would have had a prevalence of at least 5%. Among deer, handedness of scoliosis related significantly to the hemisphere where specimens originated (P < 0.001, n = 131). Coriolis forces are known to affect early stages of development, such as the innervation pattern of the mammalian vestibular system, or the plane of bilateral symmetry. It is, therefore, conceivable that the networks processing these environmental cues, or the mechanisms responsible for compensation, are malfunctioning and thus result in a preponderance of facial scoliosis in accordance to the earth’s rotation.