Caught On Film – TB Risk Of Badgers Visiting Farm Buildings

Using camera surveillance and radio tracking equipment, scientists have provided potential evidence showing how badgers could pass on bovine tuberculosis to cattle in UK farms.

In a paper published in a forthcoming Proceedings B, a Royal Society journal, researchers from the University of Sussex and the Central Science Laboratory have discovered that badgers regularly forage in farm premises such as cowsheds, feed sheds and cattle troughs, thereby making frequent contact with cattle, both directly and indirectly, in ways that could lead to tuberculosis transmission. The study suggests that one possible strategy to reduce the risk of infection would be to improve facilities for the storage of animal feeds.

Badgers from two social groups, including individuals known to be infected with bovine tuberculosis, were observed visiting and foraging in farm buildings at two farms in Woodchester Park, a beautiful secluded valley owned by the National Trust, near Stroud Gloucestershire, UK. The park is situated in one of the UK`s TB `hot spots`.

A large number of badgers were frequently observed eating from a number of food sources in and around farm buildings, including cattle feed and silage, and came into close contact with cattle. During the visits cattle feed was contaminated with badger droppings.

The minimum number of badgers visiting the farm buildings was strongly correlated with periods of dry weather. During dry weather earthworms, the badger`s preferred evening meal, tend to remain below ground to avoid desiccation.

Circumstantial evidence
Badgers are known to be susceptible to bovine TB and have been implicated in the transmission of the bacterium to cattle, however the precise route has not yet been determined.

“Research on transmission routes has focused on cattle grazing on contaminated pasture,” says Ben Garnett, whose work on this project is part of his PhD thesis at the University of Sussex. “However cattle will usually avoid feeding on pasture contaminated by badger excreta and the TB bacterium does not survive long on summer pastures.” Respiratory contact between badgers and cattle on pasture land, another potential infection route, is also unlikely as badgers rarely approach within 10 metres of cattle in the open.

Previously there have been very few reports of badgers using farm buildings for shelter or to forage, with any evidence being circumstantial or anecdotal. The current study was undertaken to further our understanding of such interactions between badgers and cattle, and the results were surprising.

“On some nights up to 10 badgers were observed foraging around the farm buildings,” explains Ben Garnett. “The visits usually occurred between 11pm and 4 am with the badgers exploiting a wide range of food sources from cattle feed to rodents. However cattle feed cake was the most popular food and was obtained from sheds, silos and also open feed troughs which badgers accessed by jumping or climbing in.” It was observed that calves and heifers would later feed from these troughs, even if contaminated with badger droppings, a clear potential transmission route for bovine TB. “Presumably the cattle feed cake is highly palatable and cattle are less discriminating than when feeding on pasture,” says Ben Garnett. “In addition the badgers sometimes came within two metres of cattle in these situations allowing the possibility of infection via aerosolised bacilli, especially in poorly ventilated farm buildings.”

An alternative strategy for TB control?
Ben Garnett believes that the current study suggests a possible alternative approach to managing bovine TB. “A potential solution is in the farmer`s hands,” says Ben Garnett. “This study shows the practice of storing farm animal feeds in facilities that can be accessed by badgers can result in direct and indirect contact between badgers and cattle that could lead to infection.”

Cattle on both farms used for observations suffered outbreaks of TB during the study. “This study has provided some exciting insights into the potential paths for TB transmission from badgers to cattle,” concludes Ben Garnett, “and suggests that changes to farm husbandry may be one strategy that farmers could adopt to reduce the risk of infection.”

The UK badger culling field trial, set up in 1998 following the report by Sir John Krebs on Bovine TB, has recently restarted following its suspension during the foot and mouth epidemic. The field trial aims to resolve the uncertainty about the effects of badger culling on the incidence of Bovine TB and is part of the UK Government`s current long-term strategy to control the disease. A summary of government strategy is available on the DEFRA website at http://www.defra.gov.uk/animalh/tb

The full title of this paper is:

Use of cattle farm resources by badgers (Meles meles) and risk of bovine tuberculosis (Mycobaterium bovis) transmission to cattle
by B.T. Garnett, R.J. Delahay and T.J. Roper

PLEASE ACKNOWLEDGE THE ROYAL SOCIETY PROCEEDINGS B AS THE SOURCE FOR THIS PAPER.
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Contact for further information
For more details of the featured and other papers, including how to obtain a full copy of this paper and contact details for the paper`s author, Ben Garnett, please contact:

Tim Reynolds on tel: or +44 (0) 7711 942974 or +32 (0)2640 3226,
Or email: tim.reynolds@absw.org.uk or timjreynolds@email.msn.com.