Bat rabies in a striped skunk in Quebec
Following the documentation of one case of raccoon rabies in southern Quebec in 2006, a program to monitor the occurrence of raccoon rabies was launched. The main goal of this program is to detect as early as possible the presence of raccoon rabies in Quebec. The control measures put in place by the Ministère des forêts, de la faune et des parcs (MFFP), including the use of vaccine baits, made it possible to control this epidemic and then eliminate this variant from Quebec. Due to the presence of raccoon rabies cases in neighbouring states, less than 100 kilometres from the border, the MFFP continues its efforts to detect and control this fatal disease. As part of the enhanced monitoring program coordinated by the MFFP, raccoons, striped skunks and foxes found dead or sick are submitted to the Canadian Wildlife Health Cooperative (CWHC) for analysis. It should be noted that a case of raccoon rabies was documented in 2015, in the Quebec portion of the Akwesasne Reserve. This case was associated with the epidemic outbreak that emerged in upstate New York State (Franklin County) in 2015, where 15 cases of raccoon rabies were detected at a distance ranging from 1 to 18 km from the border with Quebec. Control interventions (application of vaccine baits) were adjusted accordingly in 2015 and subsequent years. No other case of raccoon rabies has been detected in Quebec since then.
Last summer (2019), a striped skunk was seen with abnormal behaviour in the middle of the afternoon in the city of Longueuil, Quebec. This skunk died a few minutes after its discovery. As part of the Enhanced Raccoon Rabies Surveillance Program, a technician from the MFFP retrieved the animal and submitted it for analysis. This skunk was submitted to the regional centre of the CWHC in Quebec (CQSAS) where the brain was evaluated by the Direct Rapid Immunoperoxidase Test (known under the acronym DRIT). This test, which could be performed quickly in a standard level II laboratory,turned out to be positive. A diagnosis of rabies was later confirmed in the level III laboratory of the Canadian Food Inspection Agency (CFIA) using the Fluorescent Antibody Test (known as FAT). The abnormal behaviour and death of this skunk were therefore caused by rabies.
“Positive” reaction of a DRIT test on a brain impression to assess the presence of rabies. The rusty areas show the presence of rabies virus (antigens) in the tissues.
It is important to mention that in Quebec, different variants of the rabies virus are or have been historically present: the variants of terrestrial rabies (variant of Arctic fox and raccoon), as well as several variants of bats. Although the different variants can cause rabies in all mammalian species, each variant is adapted to a group of species; the Arctic fox variant can be maintained in arctic fox and red fox, the raccoon variant can be maintained in the raccoon and the striped skunk, and those of bats can be maintained in different species of bats. The maintenance and transmission of each variant are usually within the respective reservoir species. Although occasionally an animal of another species is infected with one of these variants (so-called overflow or accidental infection), this type of infection will not allow the development of outbreaks of rabies in the population of an overflow species. In other words, although a skunk infected with the bat rabies virus can be contagious and die, this variant will not persist in the skunk population. Consequently, the detection of a virus from one of the bat variants, which are already present in the Quebec territory, does not have the same implication as the detection of a raccoon variant virus.
For this reason, when rabies is detected in an animal, it is essential to determine the variant of the detected virus. In this case, CFIA determined that this skunk was in fact infected with a bat variant. This suggests that this skunk was bitten by a sick bat. In addition, skunks, which have been known to scavenge carcasses of bats, could also get infected from contact with a dead rabid bat. The detection of this case of “bat rabies” does not have the same implication that the detection of an infection with the raccoon variant would have had.
This case demonstrates that the enhanced surveillance program for raccoon rabies set up in the Estrie and Montérégie regions and delivered in collaboration with the various provincial agencies, the CWHC and the CFIA, is able to detect the presence of cases of rabies in the territory.
For more information on the Quebec Raccoon Rabies Program, please visit:
https://www.rageduratonlaveur.gouv.qc.ca/en/
Prepared by Stéphanie Tremblay-Chapdelaine, Stéphane Lair (CWHC-Quebec) and Marianne Gagnier (MFFP)
