Rabies in two big brown bats in Saskatchewan

Big Brown Bat. Matt Reinhold-Flickr

The Canadian Wildlife Health Cooperative (CWHC), Western and Northern Region, recently had two interesting big brown bat submissions. One bat had been submitted to a rehabilitation facility in October 2013 after being found on the ground by members of the public in Saskatoon. She had bruising around her shoulder and was described as “bitey” when being handled. The second bat was found in a local church on January 10^th, 2014, captured in a container and taken to the same rehabilitation facility. This male bat had crusting lesions on his chin. The bats were housed individually under conditions that would induce normal torpor or hibernation but they were reluctant to drink and had lost weight. There was difficulty regulating the temperature of the hibernation chamber, with the temperature dropping below 4 C rather than maintaining the desired temperature range of 6 – 9 C. The bats subsequently died within 2 days of each other (the female on February 16 and the male on February 18) and were submitted for autopsy the following day. On examination of brain tissues under light microscopy characteristic rabies virus inclusion bodies, so called negri bodies, were observed and immunohistochemical stains, specific for rabies, confirmed the diagnosis. As there was no history of direct human contact, samples were not sent to the Canadian Food Inspection Agency (CFIA) rabies lab until after the diagnosis was made by CWHC.

These cases are interesting for several reasons. First, it highlights the importance of bats as a source of rabies in Canada, and elsewhere, and the potential of bats to come into contact with humans. Big brown bats often hibernate in buildings and for that reason are found frequently by members of the public. Live bats are commonly taken to rehabilitation facilities due to public education campaigns stressing the importance of these often maligned animals. Fortunately this rehabilitation facility had taken precautions to prevent human exposure. We have had similar situations in the past where bats have tested positive while being rehabilitated and precautions had not been taken which resulted in post-exposure treatment of people and considerable anxiety for those involved. These two cases are also interesting because of the long incubation period observed in these bats, assuming they were suffering from rabies at the time they were submitted to the rehabilitation centre and they did not have contact with each other.

Big Brown Bat.  Matt Reinbold – Flickr

Finally these cases are also noteworthy as it highlights the changing role of the federal Canadian Food Inspection Agency in rabies diagnosis and surveillance. The CFIA will only test animals for rabies when there is a human health risk but will confirm the diagnosis of positive tests from non-human health risk cases done in other laboratories. The Canadian Wildlife Health Cooperative, and other similar agencies, have now taken on primary responsibility for diagnosis and surveillance of rabies in wildlife. Appropriate precautions should always be taken when handling bats in order to prevent exposure to rabies and other diseases.