Disseminated Mycobacterium ulcerans Infection in Wild Grasscutters (Thryonomys swinderianus), Côte d’Ivoire

Abstract

Buruli ulcer is an infectious disease provoking chronic, disabling skin ulcers in mammals and humans. Buruli ulcer is caused by Mycobacterium ulcerans, an environmental mycobacterium synthesizing a toxin called mycolactone responsible for the pathogenicity. The reservoirs and the modes of transmission of M. ulcerans remain elusive, limiting the prophylaxis capabilities in rural areas in endemic countries. In Australia, several studies have demonstrated the probable role of possums as reservoirs. In Côte d’Ivoire, some studies have speculated on the potential role of grasscutters in the transmission cycle of M. ulcerans. In this study, we detected M. ulcerans–specific sequences in rectal contents and spleens collected in wild grasscutters hunted in Buruli ulcer–endemic area in Côte d’Ivoire, but not in farmed negative control animals and in domesticated animals, namely, pigs, goats, cattle, and dogs, living in close contact with the local population. Some grasscutters exhibited the same sequence pattern in the feces and spleen. These observations confirm the asymptomatic gut carriage of M. ulcerans in this mammal species. Moreover, these observations suggest the dissemination of M. ulcerans from the gut to the spleen in grasscutters. These observations suggest that, in some mammals, M. ulcerans is not only an inoculated pathogen but also a translocating invasive pathogen.

TranslocatingMycobacterium ulcerans: an experimental model

“…Our experimental results thus confirm that some wild rodents are digestively infectable with M. ulcerans, as it has been previously observed for wild agoutis in Côte d’Ivoire [7–8]. and for possums in Australia [10].…”

“…We have previously reported the molecular detection of M. ulcerans DNA in the digestive tract and the spleens of wild agoutis caught in Côte d’Ivoire: and its culture in one case [7–8] In the present work, we developed an experimental model of gastrointestinal infection in rats to confirm that our field observations were the result of probable gastrointestinal contamination of wild agoutis. We chose the rat model as the laboratory mammal closest to agouti, sharing its general morphology (in terms of size and weight), a herbivorous rodent diet and a body temperature of 37°C, which also makes it a relevant model of human infection [15].…”

“…Accordingly, it’s been reported that M. ulcerans is being cultivated from aquatic Hemiptera [6]. indeed M. ulcerans DNA has also been detected in some animals including Thryonomys swinderianus (here designed agoutis, the word commonly used in West Africa) [7–8] rabbits and rats, which have all in common to be rodent mammals [9]. Moreover, two isolates of M. ulcerans have been reported from possum feces collected in Melbourne, region, Australia although characterization and repository reference were not provided [10].…”

“…Furthermore, we recently reported the isolation of M. ulcerans from T. swinderianus feces collected in the vicinity of the Kossou Dam, Côte d’Ivoire, although we were unable to sub-culture this isolate [8]. These observations suggested that T. swinderianus , an herbivorous mammal rodent may contaminate its digestive tract by the oral route after eating M. ulcerans -contaminated food; possibly acting as a secondary source of infection for populations as it is catched as brush meat and eaten after unprotected, manual evisceration [7] Likewise, it has been suggested that the small terrestrial mammals Mastomys natalensis can play a potential role in the natural history of M. ulcerans [12]. Also, we recently observed the PCR-based detection of the ketoreductase B gene (KR-b) and the IS 2404 and IS 2606 insertion sequences in one tenth of spleen specimens collected from T. swinderianus in the area of Yamoussoukro area, Côte d’Ivoire, and in spleen of common ringtail possums in some areas of Victoria endemic for M. ulcerans disease [7–10].…”

Translocating Mycobacterium ulcerans: An experimental model

“…M . ulcerans DNA has also been detected in some animals including Thryonomys swinderianus (referred to in this paper as “agoutis”, the word commonly used in West Africa) [ 7 , 8 ], rabbits and rats, which are all rodent mammals [ 9 ]. Moreover, two isolates of M .…”