Postepizootic Persistence of Asymptomatic Mycoplasma conjunctivae Infection in Iberian Ibex

Abstract

The susceptibility of the Iberian ibex (Capra pyrenaica) to Mycoplasma conjunctivae ocular infection and the changes in their interaction over time were studied in terms of clinical outcome, molecular detection, and IgG immune response in a captive population that underwent a severe infectious keratoconjunctivitis (IKC) outbreak. Mycoplasma conjunctivae was detected in the Iberian ibex, coinciding with the IKC outbreak. Its prevalence had a decreasing trend in 2013 that was consistent with the clinical resolution (August, 35.4%; September, 8.7%; November, 4.3%). Infections without clinical outcome were, however, still detected in the last handling in November. Sequencing and cluster analyses of the M. conjunctivae strains found 1 year later in the ibex population confirmed the persistence of the same strain lineage that caused the IKC outbreak but with a high prevalence (75.3%) of mostly asymptomatic infections and with lower DNA load of M. conjunctivae in the eyes (mean quantitative PCR [qPCR] cycle threshold [C T ], 36.1 versus 20.3 in severe IKC). Significant age-related differences of M. conjunctivae prevalence were observed only under IKC epizootic conditions. No substantial effect of systemic IgG on M. conjunctivae DNA in the eye was evidenced with a linear mixed-models selection, which indicated that systemic IgG does not necessarily drive the resolution of M. conjunctivae infection and does not explain the epidemiological changes observed. The results show how both epidemiological scenarios, i.e., severe IKC outbreak and mostly asymptomatic infections, can consecutively occur by entailing mycoplasma persistence.IMPORTANCE Mycoplasma infections are reported in a wide range of epidemiological scenarios that involve severe disease to asymptomatic infections. This study allows a better understanding of the transition between two different Mycoplasma conjunctivae epidemiological scenarios described in wild host populations and highlights the ability of M. conjunctivae to adapt, persist, and establish diverse interactions with its hosts. The proportion of asymptomatic and clinical M. conjunctivae infections in a host population may not be regarded only in response to intrinsic host species traits (i.e., susceptibility) but also to a specific host-pathogen interaction, which in turn influences the infection dynamics. Both epidemic infectious keratoconjunctivitis and a high prevalence of asymptomatic M. conjunctivae infections may occur in the same host population, depending on the circulation of M. conjunctivae, its maintenance, and the progression of the host-pathogen interactions.

Infectious keratoconjunctivitis and occurrence of Mycoplasma conjunctivae and Chlamydiaceae in small domestic ruminants from Central Karakoram, Pakistan

“… 7 8 Ocular clinical signs were however not related with the Ct values of the M. conjunctivae qPCR and several asymptomatic infections exhibited low Ct values (ie, inverse to mycoplasmal loads), which suggests that a different host–mycoplasma interaction than the previously described in wild Caprinae occurred in sheep and goats. 5 45 46 …”

Long-term dynamics of Mycoplasma conjunctivae at the wildlife-livestock interface in the Pyrenees

“…Since size and fusion rates of chamois groups increase with density [ 59 ], a nearly density-dependent transmission may occur if population density is high and groups/subpopulation units are highly connected [ 60 ]. The adaptive immune response of hosts does not always prevent mycoplasma re-infection [ 61 – 63 ], which may eventually be enhanced in denser populations and drive mycoplasma-host interaction to an endemic scenario [ 6 ], as observed in PyFS. Low population density in group-living ungulates can however shape pathogen transmission to be frequency-dependent if contacts between social groups or subpopulations are not common [ 60 , 64 ].…”

“…However, high number of asymptomatic M . conjunctivae infections have been reported in both epizootics and situations with low but regular incidence of IKC cases [ 6 , 31 ]. Clinical signs compatible with IKC were not registered in Cantabrian chamois, which agrees with the absence of M .…”

“…Even with genetics and the evidence of cross-species transmission, low resolution of spatiotemporal data may not provide a comprehensive insight of the host-pathogen system [ 4 ]. Furthermore, the identification of reservoir host populations can be especially critical in pathogens that can establish diverse interactions with its hosts, resulting in different clinical outcomes and epidemiological scenarios [ 5 , 6 ].…”

“…Several wild hosts have been described suffering from IKC, chamois ( Rupicapra spp. ), Alpine ibex ( Capra ibex ), Iberian ibex ( Capra pyrenaica ), mouflon ( Ovis aries musimon ), the Himalayan tahr ( Hemitragus jemlahicus ) and bighorn sheep ( Ovis canadensis ) [ 6 , 8 , 18 ]. Among them, chamois are the most common and widespread species in Europe and the one that have suffered more frequent and severe IKC outbreaks [ 12 , 15 , 17 , 19 , 20 ].…”