Date Published: April 17, 2019
Publisher: Public Library of Science
Author(s): Alejandro R. Vila, Cristóbal Briceño, Denise McAloose, Tracie A. Seimon, Anibal G. Armién, Elizabeth A. Mauldin, Nicholas A. Be, James B. Thissen, Ana Hinojosa, Manuel Quezada, José Paredes, Iván Avendaño, Alejandra Silva, Marcela M. Uhart, Rachel L. Roper.
The huemul (Hippocamelus bisulcus) is an endangered cervid endemic to southern Argentina and Chile. Here we report foot lesions in 24 huemul from Bernardo O’Higgins National Park, Chile, between 2005 and 2010. Affected deer displayed variably severe clinical signs, including lameness and soft tissue swelling of the limbs proximal to the hoof or in the interdigital space, ulceration of the swollen tissues, and some developed severe proliferative tissue changes that caused various types of abnormal wear, entrapment, and/or displacement of the hooves and/or dewclaws. Animals showed signs of intense pain and reduced mobility followed by loss of body condition and recumbency, which often preceded death. The disease affected both genders and all age categories. Morbidity and mortality reached 80% and 40%, respectively. Diagnostics were restricted to a limited number of cases from which samples were available. Histology revealed severe papillomatous epidermal hyperplasia and superficial dermatitis. Electron microscopy identified viral particles consistent with viruses in the Chordopoxvirinae subfamily. The presence of parapoxvirus DNA was confirmed by a pan-poxvirus PCR assay, showing high identity (98%) with bovine papular stomatitis virus and pseudocowpoxvirus. This is the first report of foot disease in huemul deer in Chile, putatively attributed to poxvirus. Given the high morbidity and mortality observed, this virus might pose a considerable conservation threat to huemul deer in Chilean Patagonia. Moreover, this report highlights a need for improved monitoring of huemul populations and synergistic, rapid response efforts to adequately address disease events that threaten the species.
There is an increasing concern about the potential contribution of diseases in wildlife extinctions, particularly when they interact with other driving factors [1–5]. For example, the effects of infectious pathogens can have devastating effects when population size is small, when multi-host pathogens and reservoir hosts are available, when the infectious agent can survive in an abiotic environment or when disease transmission is influenced by environmental factors or climate change [6–8]. Furthermore, the outcome of an infectious disease depends on intrinsic characteristics of the pathogen that shape morbidity and mortality, ultimately defining severity of illness and the future of affected populations [5, 9, 10].
Overall, 24 huemul deer with foot lesions were identified between April 2005 and August 2010. Seventy five percent (n = 18) of affected huemul were located in HV; the remainder were found in the more isolated KV (n = 1) and BV (n = 5) (Fig 1). All affected deer displayed similar but varying degrees of clinical signs. These included lameness and soft tissue swelling in one or more limbs just proximal to the hoof or in the interdigital space and, in some cases ulceration of the swollen areas. Some cases spontaneously and completely resolved while others progressed to more severe, proliferative and/or suppurative forms that caused various types of abnormal wear, entrapment, and/or displacement of the hooves and/or dewclaws. These animals showed signs of intense pain such as marked lameness, reluctance to bear any weight on the affected feet, and reduced mobility followed by loss of body condition and prolonged recumbency, which often preceded death.
This is the first report of foot disease, putatively attributed to poxvirus, in huemul deer in Chile. The severity of clinical disease was variable, yet in a third of affected animals (at least six individuals), it resulted in complete incapacitation and death. That a minimum of 18 deer were affected in HV (over five years), with morbidity and mortality rates as high as 80% and 40%, respectively, denotes that foot lesions such as those reported here pose a considerable conservation threat for this species.