兽医科技

Monitoring of pseudotuberculosis in an Italian Population of Alpine Chamois: Preliminary Results

Abstract

Martina Besozzi, Emiliana Ballocchi, Pierluigi Cazzola and Roberto Viganò

Caseous lymphadenitis (CLA) of sheep and goats is a chronic and often sub-clinical disease, with high prevalence in different parts of the world, which can caused significant economic losses for farmers. The causative agent is Corynebacterium pseudotuberculosis that primarily infects domestic small ruminants, but it has been isolated also in wildlife such as pronghorns (Antilocapra americana) and elk (Cervus elaphus canadensis). Furthermore, a recent research has demonstrated a maintenance of the infection on an endemic level in a Spanish ibex (Capra pyrenaica hispanica) population after an outbreak with high morbidity and mortality. The typical clinical manifestation is lymph node abscess that may fistulize and discharge pus contaminating the environment where can survive for months in faeces, fomites, and soil. Infected subjects with the sub-clinical form can also shed bacteria through respiratory tract and mechanical vectors such as flies. Human infection is a rare event. Wildlife-livestock interfaces are dynamic and bidirectional and pathogens could be transmitted freely within and between the two species. The study area is the Alpine hunting district located in Vercelli province (formerly named C.A. VC1). The study was carried out during 2016 hunting season, between September and December and performed on hunted chamois. A macroscopic examination of each carcass has been conducted at the Control Centre, where each hunter had to bring the chamois after culling for the control by a veterinarian. Hunters collected post-mortem-blood samples via jugular or heart clot from their own bag and leaded up to the Control Centre where serum was obtained by centrifugation and stored at -20°C until further processing. A commercial enzyme-linked immunosorbent assay (ELISA) kit (ELITEST CLA, HYPHEN BioMed, France) has been used to detect antibodies (IgG) anti-PLD. Results have been expressed as OD after reading the plates at 450 nm in an ELISA microplate reader. The aim of this monitoring is to confirm the circulation of C. pseudotuberculosis in the chamois population as suspected on the basis of the finding of several chamois with characteristic lesions during previous hunting seasons and to identify risk factors for the infection and the development of clinical signs of disease. 196 chamois have been hunted in 2016 hunting season, a total of 34 sera have been processed (1 kid, 7 yearlings, 17 adult males, 9 adult females) showing a seroprevalence of 8.82% (c.i. 95% 0.0-18.26). One yearling female and two adult females resulted seropositive; at the macroscopic examination the two adults had showed typical lymph node abscesses in abdominal cavity and the oldest was underweight and presented typical dermatophilosis lesions. Furthermore, a 4-year-old male showed a grey zone OD. The results of this first year survey on the territory are to be considered as preliminary, the starting point for a data collection that can become a historical series that could give useful management guidance in the near future. In spite of this, it can be safely stated that the first results obtained confirm the circulation of C. pseudotuberculosis, together with the pathological and bacteriological diagnoses of previous years. The fact that a yearling seropositive has been found without any lesions found is evidence of the current circulation of the pathogen as this subject has come into contact with the infection during the previous year.