Introduction

Rabbits have been increasingly linked to the persistence of paratuberculosis in domestic ruminants in the UK. The aims of this study were to determine the routes of intra-specific transmission of Mycobacterium avium subsp. paratuberculosis (Map) in rabbits and to estimate the probability of transmission via each route, in order to gain understanding of the dynamics of Map in this host.

Methods

Rabbits were sampled from two sites where Map had previously been isolated from the livestock and rabbit populations. Gross examination of the samples was carried out before tissues including a gut pool, reproductive organs, milk and foetuses, were collected for microbiological and histopathological examination. Isolates of Map were confirmed by PCR using IS900.

Results

Overall prevalence of Map in rabbits was high at both sites, 39.7% and 23.0% respectively. Map was isolated from the gut pool, testes, uterus, placenta, foetuses, faeces and milk. Vertical and/or pseudo-vertical transmission occurred in up to 19.6% of offspring born to an infected doe, equating to a probability of infection via this route of up to 0.458. Increase in infection prevalence in the population through horizontal transmission occurred at a maximum rate of 2.28% per month, equating to an individual probability of infection via this route of up to 0.046 per month.

Discussion

This is the first time that this bacterium has been isolated from reproductive organs, foetuses, placenta or milk in a non-ruminant wildlife species. The presence of vertical, pseudo-vertical and horizontal routes of transmission within natural rabbit populations contribute to the maintenance of Map infections within such populations and, therefore, the environment.