Animal bites and rabies management in BC

Rabies is an almost invariably fatal zoonotic viral infection, and kills more than 59 000 people annually around the world, mostly in Asia and Africa. In Canada, rabies is rare; the last human case occurred in 2007. The only case in recent history in BC occurred in 2003 when an adult male was fatally infected with the bat-variant rabies virus. Potential rabies exposures, however, occur frequently and need to be assessed and managed properly.  

Rabies virus variants are maintained in particular reservoir species. Globally, dogs are the source of the vast majority of human rabies deaths. Fortunately, vaccination and animal-control programs in Canada have eliminated dogs as rabies reservoirs. In Canada, rabies is primarily transmitted by bats, skunks, and foxes;[1] however, these species are not reservoirs in all provinces, as discussed below. 

In BC, bats are the only known rabies reservoir species. In 2015 and 2016, 14% of the bat specimens sent from BC to the national reference laboratory tested positive for rabies. Infected bats are considered more likely to come into contact with humans and subsequently be tested because of altered behavior. It is estimated that less than 0.5% of bats are actually infected.[2] 

Other species in BC that have tested positive for rabies between 1969 and 2016 include 5 cats, 4 skunks, 1 beaver, and 1 horse. All had bat-variant rabies except for two cases, which had the skunk strain. Follow-up studies concluded that skunk and other nonbat rabies strains are not endemic in BC. 

Rabies is transmitted to humans by exposure to the saliva or neural tissue of an infected animal, most often through a bite, scratch, or contact with a mucous membrane. The incubation period in humans is usually 3 to 8 weeks, rarely as short as a few days or as long as several years. 

Immediate wound washing by flushing with warm water for 15 minutes decreases the risk of infection. If the risk of rabies is high, a course of rabies postexposure prophylaxis (RPEP) consisting of one dose of rabies immune globulin and four doses of rabies vaccine on days 0, 3, 7, and 14 is recommended. Once the clinical disease manifests, treatment does not usually affect the rapid progression to death. Other risk-management options include animal observation and animal testing.

Exposures considered a high risk for rabies should be discussed with the medical health officer, who must approve all requests for RPEP. 

In BC, as bats are reservoirs for rabies, any contact with a bat through which saliva or neural tissue may have been introduced is considered very high risk, and testing of the bat and immediate RPEP should be considered. Aside from bats, other animal bites in BC should be assessed to determine if there are factors that would increase the rabies risk. The most common situations where rabies risk is elevated involve animals that:
•    Are demonstrating neurological behavior compatible with rabies. In this case, the risk of rabies is high and testing of the animal and immediate RPEP should be considered.  
•    Have been imported from, or traveled to, a rabies-endemic area within the last 6 months. 
•    Had known contact with a bat within the last 6 months.

If none of these risk factors are present, then the risk of rabies is low. Dog bites are not reportable in BC unless rabies is a concern.  

It is important to note that these risk factors are specific to exposures that occur in BC. If the exposure has occurred elsewhere in Canada or outside of Canada, then the risk assessment and management must be adapted.

Fortunately, rabies remains a rare disease. Prevention by animal vaccination, public education to limit physical contact with bats, and postexposure prophylaxis are the mainstays of protection.
—Melissa McLaws, DVM, PhD
—Eleni Galanis, MD, MPH, FRCPC

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This article is the opinion of the BC Centre for Disease Control and has not been peer reviewed by the BCMJ Editorial Board.

References

1.    Canadian Food Inspection Agency. Rabies in Canada. Accessed 28 February 2017. http://www.inspection.gc.ca/animals/terrestrial-animals/diseases/reporta....
2.    Pybus MJ. Rabies in insectivorous bats of western Canada, 1979 to 1983. J Wildl Dis 1986;22:307-313.