Specificity of Mycoplasma conjunctivae strains for alpine chamois Rupicapra r. rupicapra

Infectious keratoconjunctivitis (IKC) is worldwide known as a common infection by Mycoplasma conjunctivae affecting the eyes of domestic sheep and goats where it generally leads to moderate symptoms known as ‘‘pink eye’’. IKC also occurs in severe outbreaks in free-ranging alpine chamois Rupicapra r. rupicapra and alpine ibex Capra i. ibex. It is characterised by grave clinical symptoms resulting in blindness and perforations of the cornea of the affected animals, and finally leads to their death. Transmission of M. conjunctivae from domestic sheep to wild Caprinae has been demonstrated by molecular epidemiological studies of the infectious agent. The relatively high prevalence of M. conjunctivae in sheep populations that share pastures in the Alps with wild Caprinae, in which outbreaks occur infrequently but with high virulence, raised an important question concerning the role of host-specificity of various strains of M. conjunctivae. Investigations on genetic variations of M. conjunctivae strains allowed subtyping of M. conjunctivae isolates using a molecular genetic method that can be directly applied to samples taken by eye swabs. Our studies revealed that sheep with IKC are frequently infected simultaneously with up to four different strains of M. conjunctivae. In contrast, affected chamois only showed infections with a single strain. Furthermore, among the different strains of M. conjunctivae that have been determined until now, 36 strains are repeatedly found in sheep, while only a few different strains, all belonging to a phylogenetically related cluster, were found in chamois with IKC. These few strains were responsible for all severe outbreaks of IKC in chamois during the last four years in Switzerland, Austria and Italy. Our studies indicate that a particular cluster of strains of M. conjunctivae has a host predilection for chamois where they cause severe infections.