Bats and rabies in Alberta

Overview

Rabies can kill any warm-blooded bird or mammal, including humans. It was first identified in North American bats in 1953 in Florida but has probably affected them for centuries.

The rabies virus is present in the Alberta bat population, but the prevalence is believed to be extremely low.

Facts about rabies

Rabies is a viral disease that can cause fatal infections. The virus:

• prefers to live in nerve tissue, particularly in the brain and central nervous system
• causes damage to specific areas of the brain that control behaviour, resulting in changes including:
  • an initial aggressive stage
  • a later lethargic stage

In bats, the aggressive stage is short. In the longer lethargy stage, the bats can be found on the ground, unable to fly.

Death finally occurs when the virus damages vital parts of the brain.

Transmission

The rabies virus accumulates in the salivary glands and is transferred in saliva. Transmission can be:

• direct, occurring when an animal eats or is bitten by an infected individual
• indirect, occurring if large amounts of saliva contaminate an object, then are transferred to an open wound in the skin

Facts about rabies in bats

In bats, the rabies virus:

• is transmitted between individuals of the same or different bat species
• rarely infects species other than bats
• overwinters in a dormant state in hibernating bats
• is reactivated by stress or a return to a bat’s normal metabolic conditions after hibernation, resulting in more rabid bats in early summer and fall
• is seen in bats that are under stress due to long, rigorous migrations

Where are rabid bats found?

The pattern of rabies in insectivorous bats is consistent across North America and has not changed in 50 years.

For information on rabies in Western Canada, read a 1986 article in the Journal of Wildlife Diseases here:

• Rabies in Insectivorous Bats of Western Canada, 1979 to 1983

Rabies in Alberta bats

In Alberta, rabies has been diagnosed in the following bat species:

• Big brown bat (Eptesicus fuscus)
• Hoary bat (Lasiurus cinereus)
• Little brown bat (Myotis lucifugus)
• Silver-haired bat (Lasionycteris noctivagans)
• Western small-footed bat (Myotis ciliolabrum), a single individual

Prevalence by bat species

Data collected in Alberta through testing done by the Canadian Food Inspection Agency (CFIA) indicates that the prevalence of rabies infection in bats varies by species.

Big brown bats

The prevalence of rabies in suspect big brown bats (those that are acting strange or are on the ground) has been consistent. It is 5% to 10% of those tested.

Hoary bats

The number of these bats submitted for testing is too low to establish an infection rate. Very few rabid hoary bats are found.

Little brown bats

This is by far the most common bat species in Alberta. The prevalence of the rabies virus in the species decreased significantly in the 1970s. It has all but disappeared since then.

Silver-haired bats

The prevalence in this species is erratic, ranging from 0% to 18%. The infection rate is affected by the low number of these bats that are tested.

Bat collection and testing

Alberta has a long history of rabies control. A general fact sheet about rabies and a summary of rabies management in Alberta are available at Wildlife Diseases.

Most rabid bats are collected in August and September. The number of infected bats differs from year to year and among species. But it is consistently low (6 to 10 rabid bats each year).

Random collection

Alberta government staff randomly collect bats from nursery colonies. These bats are rarely infected with rabies (1 in 1,500 tested since 1979).

This tells us that while the virus is present in the general bat population, the prevalence is extremely low.

Bats collected by the public

Albertans can submit bats that have come in contact with a person, pet or livestock to any veterinary or Fish and Wildlife office for rabies testing.

If animals have had physical contact with a bat, animal owners should follow-up with a veterinarian.

Any person who has had physical contact with a bat should follow-up with a healthcare provider to determine if they need post-exposure treatment.

Who does rabies testing?

The Canadian Food Inspection Agency (CFIA) conducts all rabies testing in Canada. To view testing results, go to Positive Rabies in Canada on the CFIA website.

Distribution in Alberta

The number of bats with rabies in Alberta is low (6 to 10 rabid bats each year) but they can be found throughout the province. Sick or dead bats are normally reported where people live. Sick or dead bats go largely unnoticed in uninhabited areas.

More bats are collected and tested in southern Alberta because of increased public awareness and concern about rabies in that area.

There has been no significant change in the rabies rate in Alberta bats since data was reported in the 1970s.

Related

Canadian Food Inspection Agency: Rabies