Infection of Wildlife by Mycobacterium bovis in France Assessment Through a National Surveillance System, Sylvatub

Abstract

Mycobacterium bovis infection was first described in free-ranging wildlife in France in 2001, with subsequent detection in hunter-harvested ungulates and badgers in areas where outbreaks of bovine tuberculosis (TB) were also detected in cattle. Increasing concerns regarding TB in wildlife led the French General Directorate for Food (DGAL) and the main institutions involved in animal health and wildlife management, to establish a national surveillance system for TB in free-ranging wildlife. This surveillance system is known as “Sylvatub.” The system coordinates the activities of various national and local partners. The main goal of Sylvatub is to detect and monitor M. bovis infection in wildlife through a combination of passive and active surveillance protocols adapted to the estimated risk level in each area of the country. Event-base surveillance relies on M. bovis identification (molecular detection) (i) in gross lesions detected in hunter-harvested ungulates, (ii) in ungulates that are found dead or dying, and (iii) in road-killed badgers. Additional targeted surveillance in badgers, wild boars and red deer is implemented on samples from trapped or hunted animals in at-risk areas. With the exception of one unexplained case in a wild boar, M. bovis infection in free-living wildlife has always been detected in the vicinity of cattle TB outbreaks with the same genotype of the infectious M. bovis strains. Since 2012, M. bovis was actively monitored in these infected areas and detected mainly in badgers and wild boars with apparent infection rates of 4.57–5.14% and 2.37–3.04%, respectively depending of the diagnostic test used (culture or PCR), the period and according to areas. Sporadic infection has also been detected in red deer and roe deer. This surveillance has demonstrated that M. bovis infection, in different areas of France, involves a multi-host system including cattle and wildlife. However, infection rates are lower than those observed in badgers in the United Kingdom or in wild boars in Spain.

Mycobacteria fecal shedding in wild boars (Sus scrofa), South-eastern France

“…Culture remains the reference method for the routine confirmation of mycobacterial infection in animals 1,28 . The culture protocol herein described allows to detect an inoculum of 10 3 -10 4 CFUs M. bovis which is in the range of that extrapolated from PCR-based observations in wild boars in Spain 15 . However, contamination is a major limitation of culturing feces.…”

“…However, the wide distribution of M. bovis in wildlife is a major obstacle to the eradication of tuberculosis in cattle 2,3 . In numerous countries, bovine tuberculosis is maintained by multi-host systems involving cattle and wild mammals 2–4 . While the role of the red deer ( Cervus elaphus ) remains controversial 3 , the European badger ( Meles meles ) in Great Britain and Ireland and the wild boar ( Sus scrofa ) in the Iberian Peninsula are acknowledged reservoirs for M. bovis 3,5 .…”

“…In France, the first cases of tuberculosis in wild animals were detected in 2001 in the Brotonne forest, Normandy 2 . Then, monitoring programs for tuberculosis in wild animals were applied and M. bovis was detected in badgers, wild boars, red deer, roe deer and red fox in proximity areas of bovine tuberculosis outbreak 4,19,22,24 . One case of tuberculosis was detected in a wild boar in Loir-et-Cher county which had remained free from bovine tuberculosis for more than twenty years 25 .…”

“…One case of tuberculosis was detected in a wild boar in Loir-et-Cher county which had remained free from bovine tuberculosis for more than twenty years 25 . In Southeastern France, there is a lack of information regarding the presence of tuberculosis and non-tuberculous mycobacteria in wild boars, except for information from the national surveillance system for tuberculosis in free-ranging wildlife (Sylvatub) which indicates that wild animals collect in this area are negative 4 whereas one study carried-out by serological methods that indirectly detected cases of M . bovis 26 .…”

The VetMAXTM M. tuberculosis Complex PCR Kit detects MTBC DNA in antemortem and postmortem samples from White rhinoceros (Ceratotherium simum), African elephants (Loxodonta africana) and African buffaloes (Syncerus caffer).

“…To date, the largest reported study for the use of a standardised commercial RT-qPCR in cattle was the use of the VetMAX TM MTBC qPCR Kit using a Bayesian approach and reported a sensitivity of 87.7% and a speci city of 97% (13). Since then, this RT-qPCR has been used extensively in wildlife like wild boars, badgers, and deer and its use has drastically improved bTB surveillance programs in France (16)(17)(18).…”