Infectious keratoconjunctivitis in wild Caprinae: merging field observations and molecular analyses sheds light on factors shaping outbreak dynamics

Abstract

BackgroundInfectious keratoconjunctivitis (IKC) is an ocular infectious disease caused by Mycoplasma conjunctivae which affects small domestic and wild mountain ruminants. Domestic sheep maintain the pathogen but the detection of healthy carriers in wildlife has raised the question as to whether M. conjunctivae may also persist in the wild. Furthermore, the factors shaping the dynamics of IKC outbreaks in wildlife have remained largely unknown. The aims of this study were (1) to verify the etiological role of M. conjunctivae in IKC outbreaks recorded between 2002 and 2010 at four study sites in different regions of France (Pyrenees and Alps, samples from 159 Alpine ibex Capra ibex, Alpine chamois Rupicapra rupicapra and Pyrenean chamois Rupicapra pyrenaica); (2) to establish whether there existed any epidemiological links between the different regions through a cluster analysis of the detected strains (from 80 out of the 159 animals tested); (3) to explore selected pathogen, host and environmental factors potentially influencing the dynamics of IKC in wildlife, by joining results obtained by molecular analyses and by field observations (16,609 animal observations). All of the samples were tested for M. conjunctivae by qPCR, and cluster analysis was based on a highly variable part of the lppS gene.ResultsWe documented infections with M. conjunctivae in epidemic and endemic situations, both in symptomatic and asymptomatic animals. The identified M. conjunctivae strains were site-specific and persisted in the local wild population for at least 6 years. In epidemic situations, peaks of cases and disease resurgence were associated with the emergence of new similar strains in a given area. Social interactions, seasonal movements and the landscape structure such as natural and anthropogenic barriers influenced the spatio-temporal spread of IKC. Adults were more affected than young animals and host susceptibility differed depending on the involved strain.ConclusionOur study indicates that IKC is a multifactorial disease and that M. conjunctivae can persist in wildlife populations. The disease course in individual animals and populations is influenced by both host and mycoplasma characteristics, and the disease spread within and among populations is shaped by host behavior and landscape structure.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-017-0972-0) contains supplementary material, which is available to authorized users.

Postepizootic Persistence of Asymptomatic Mycoplasma conjunctivae Infection in Iberian Ibex

“…In contrast with previous reports of IKC epizootics in sheep and chamois (27,(40)(41)(42), more severe clinical signs and higher mycoplasma DNA loads were exhibited by kids than adults in this study. It suggests that in this case, ocular tissue damage was apparently directly caused by M. conjunctivae and was probably less influenced by the adverse effects of exacerbated immune responses (2,20,43). Captive conditions may have had an influence on these results and on the lack of female-biased IKC described in disease outbreaks (26,33).…”

“…On the other hand, the known clinical outcome of the introduction of M. conjunctivae in a host population does not correspond with the epidemiological scenario found in 2014 (25,37). The persistence of M. conjunctivae has also been recently suggested in free-ranging wild host populations (20). Within-host persistence of M. conjunctivae after clinical recovery has been reported from 3 to 6 months in sheep (15) and at least up to 2 months in Alpine ibex (Capra ibex) (14).…”

“…Both epidemiological situations (i.e., IKC outbreak and endemic asymptomatic infections) have been described in other domestic (16,25) and wild free-ranging (12,20,26,27) hosts. The results of the present study show how both epidemiological situations can occur consecutively in a host population, depending on M. conjunctivae circulation, its maintenance in the population, and the progression of the host-pathogen interactions.…”

“…The local fading out of clinical disease (IKC) and the more severe clinical signs typically exhibited by wild hosts have led some to propose that M. conjunctivae cannot be maintained in wild host populations (10,(17)(18)(19). However, diverse epidemiological scenarios have been described in wild Caprinae based on field records of IKC, including its apparently endemic occurrence (12,20). The recurrent detection of M. conjunctivae strain clusters in wild host populations also suggests that it may eventually persist in natural systems (20).…”

“…However, diverse epidemiological scenarios have been described in wild Caprinae based on field records of IKC, including its apparently endemic occurrence (12,20). The recurrent detection of M. conjunctivae strain clusters in wild host populations also suggests that it may eventually persist in natural systems (20).…”