Abstract
Functional roles of domestic and wild host populations in infectious keratoconjunctivitis (IKC) epidemiology have been extensively discussed claiming a domestic reservoir for the more susceptible wild hosts, however, based on limited data. With the aim to better assess IKC epidemiology in complex host-pathogen alpine systems, the long-term infectious dynamics and molecular epidemiology of Mycoplasma conjunctivae was investigated in all host populations from six study areas in the Pyrenees and one in the Cantabrian Mountains (Northern Spain). Detection of M. conjunctivae was performed by qPCR on 3600 eye swabs collected during seven years from hunted wild ungulates and sympatric domestic sheep (n = 1800 animals), and cluster analyses of the strains were performed including previous reported local strains. Mycoplasma conjunctivae was consistently detected in three Pyrenean chamois (Rupicapra p. pyrenaica) populations, as well as in sheep flocks (17.0% of sheep) and occasionally in mouflon (Ovis aries musimon) from the Pyrenees (22.2% in one year/area); statistically associated with ocular clinical signs only in chamois. Chamois populations showed different infection dynamics with low but steady prevalence (4.9%) and significant yearly fluctuations (0.0%– 40.0%). Persistence of specific M. conjunctivae strain clusters in wild host populations is demonstrated for six and nine years. Cross-species transmission between chamois and sheep and chamois and mouflon were also sporadically evidenced. Overall, independent M. conjunctivae sylvatic and domestic cycles occurred at the wildlife-livestock interface in the alpine ecosystems from the Pyrenees with sheep and chamois as the key host species for each cycle, and mouflon as a spill-over host. Host population characteristics and M. conjunctivae strains resulted in different epidemiological scenarios in chamois, ranging from the fading out of the mycoplasma to the epidemic and endemic long-term persistence. These findings highlight the capacity of M. conjunctivae to establish diverse interactions and persist in host populations, also with different transmission conditions.
Highlights
Complex systems involving several hosts suppose a challenge for disease ecology studies [1,2]
No specific M. conjunctivae distribution pattern was found in Pyrenean chamois from PyFS during 2012–2015 as those described in infectious keratoconjunctivitis (IKC) outbreaks [12,20], and infection cases were found distributed in all seasons and months throughout the reserve (Fig 3)
Independent M. conjunctivae sylvatic and domestic cycles mainly occurred at the wildlife-livestock interface in alpine ecosystems from the Pyrenees, indicating that M. conjunctivae was maintained in some chamois populations without the substantial contribution of other hosts
Summary
Complex systems involving several hosts suppose a challenge for disease ecology studies [1,2]. In the absence of genetics, patterns of incidence and pathogen prevalence are often used to assess the epidemiological roles of host populations, but they have a number of limitations that may infer wrong functional roles [3]. An illustrative example are infections by Mycoplasma conjunctivae at the wildlife-livestock interface in alpine ecosystems, where there is no clear consensus of the functional roles of wild and domestic hosts [7,8]. Mycoplasma conjunctivae is the causative agent of infectious keratoconjunctivitis (IKC), which is a highly contagious ocular disease that severely affects Caprinae [8]. Clinical signs of IKC are associated with ocular damage and inflammation, which causes visual impairment and blindness [9]. Mortality in wild hosts can range locally from 5 to 27% and is derived from blindness of the animals that either starve or die because of traumatic accidents [12,13]
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