Mycoplasma conjunctivae in domestic small ruminants from high mountain habitats in Northern Spain

Background: Infectious keratoconjunctivitis (IKC) is a clinical condition affecting eyes of domestic and wild Caprinae worldwide, and Mycoplasma conjunctivae is considered the primary causative agent of IKC in sheep, goats and wild Caprinae. Domestic ruminants from high mountain habitats share grazing areas with wild mountain ungulates, such as chamois (Rupicapra spp.), Alpine ibex (Capra ibex) and European mouflon (Ovis aries musimon), and domestic sheep seem to act as M. conjunctivae reservoir. In this study, the presence of M. conjunctivae in domestic sheep and goats from the two main mountain ranges of Northern Spain, the Pyrenees and the Cantabrian Mountains, has been investigated. Results: Eye swabs were obtained from 439 domestic small ruminants selected from flocks that seasonally graze in alpine meadows during three consecutive years (2011-2012-2013). Seventy-nine out of the 378 domestic sheep (20.9%) tested positive to a M. conjunctivae specific real time-PCR (rt-PCR) in at least one eye, whereas all the 61 sampled domestic goats were negative. Statistically significant higher prevalence and higher proportion of infected flocks (P < 0.001) was observed in the Pyrenees (25.7%; 12 flocks out of 13), where M. conjunctivae is widespread and probably endemic in domestic sheep, than in the Cantabrian Mountains (7.8%; one flock out of six). Twenty-five sheep (three from the Pyrenees and 22 from the Cantabrian Mountains) which showed clinical signs consistent with infectious keratoconjunctivitis (IKC) were negative by rt-PCR. In contrast, 62 out of the 71 (87.3%) M. conjunctivae-positive sheep from the Pyrenees and the eight positive sheep from the Cantabrian Mountains were asymptomatic. Conclusions: This study provides rt-PCR-based evidences of M. conjunctivae maintenance in domestic sheep, as well as a relationship between prevalence in domestic sheep and previously reported M. conjunctivae and IKC in wild ruminants. Domestic goats do not seem to play an important role in the epidemiology of M. conjunctivae in alpine habitats from Northern Spain.