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.IMPORTANCEMycoplasma 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.

Keywords: Capra pyrenaica; Iberian ibex; asymptomatic infection; host-pathogen interactions; infection persistence; infectious keratoconjunctivitis; molecular epidemiology; virulence.