Occurrence, Quantification, and Genotyping of Mycoplasma Conjunctivae in Wild Caprinae With and Without Infectious Keratoconjunctivitis

Abstract

Mycoplasma conjunctivae, the causative agent of infectious keratoconjunctivitis (IKC), was recently detected in asymptomatic Alpine ibex (Capra ibex ibex). This suggested that an external source of infection may not be required for an IKC outbreak in wildlife but might be initiated by healthy carriers, which contradicted previous serologic investigations in chamois. Our aims were to 1) assess the prevalence of M. conjunctivae among asymptomatic ibex and Alpine chamois (Rupicapra rupicapra rupicapra) and its frequency in IKC-affected animals, 2) determine mycoplasma loads in different disease stages, and 3) characterize the M. conjunctivae strains involved. Eye swabs from 654 asymptomatic and 204 symptomatic animals were collected in diverse Swiss regions between 2008 and 2010, and tested by TaqMan real-time PCR. Data analysis was performed considering various patterns of IKC occurrence in the respective sampling regions. Strains from 24 animals were compared by cluster analysis. Prevalence of M. conjunctivae was 5.6% (95% confidence interval [CI]: 3.7-8.1%) in asymptomatic ibex and 5.8% (CI: 3.0-9.9%) in asymptomatic chamois, with significant differences between years and regions in both species. Detection frequency in symptomatic animals was significantly higher during IKC outbreaks than in nonepidemic situations (i.e., regular but low incidence or sporadic occurrence). Mycoplasma load was significantly lower in eyes from healthy carriers and animals with mild signs than from animals with moderate and severe signs. Although some strains were found in both asymptomatic and diseased animals of the same species, others apparently differed in their pathogenic potential depending on the infected species. Overall, we found a widespread occurrence of M. conjunctivae in wild Caprinae with and without IKC signs. Our results confirm the central role of M. conjunctivae in outbreaks but suggest that other infectious agents may be involved in IKC cases in nonepidemic situations. Additionally, presence and severity of signs are related to the quantity of M. conjunctivae in the eyes rather than to the strain. We propose that individual or environmental factors influence the clinical expression of the disease and that persistence of M. conjunctivae in populations of wild Caprinae cannot be excluded.

Is the development of infectious keratoconjunctivitis in Alpine ibex and Alpine chamois influenced by topographic features?

“…Regions are limited by geographical barriers and considered as epidemiological units (Fig. 1, Mavrot et al 2012). Convenience sampling was carried out by hunters, game keepers, and biologists on animals that were hunted, shot because of disease, found dead, or captured for marking procedures.…”

“…Each eye was sampled separately with a sterile swab. These were sent to the Centre for Fish and Wildlife Health within 48 h. Biological data of sampled animals, geographical coordinates, date and time of sampling, and a standardized description of ocular signs were systematically recorded (Mavrot et al 2012). All samples were tested for the presence of M. conjunctivae by quantitative real-time PCR according to established procedures (Vilei et al 2007), the obtained mycoplasmal load corresponding to the estimated amount of mycoplasma in the sample.…”

“…Sex and age imbalance in affected populations were observed in severe outbreaks (Degiorgis et al 2000;Tschopp et al 2005), indicating that age and social behavior including sexual segregation may be important risk factors. While possible differences in virulence between different strains do not seem to play a major role, mycoplasmal load is obviously associated to the presence and severity of signs (Ryser- Degiorgis et al 2009;Mavrot et al 2012). However, the driver of mycoplasmal multiplication in the host is unknown.…”

“…However, the driver of mycoplasmal multiplication in the host is unknown. Environmental factors may play a role, regarding both the expression of the disease in individual cases and the onset of an outbreak in a population (Mavrot et al 2012).…”

“…In wildlife, IKC is sometimes associated with high mortality (Giacometti et al 2002;Mavrot et al 2012).…”