Volume 13
Issue 4

The tragic death of a 13-year-old Connecticut girl from rabies last October has once again triggered an avalanche of dire warnings about the supposed dangers of sharing our neighborhoods with bats. Some communities have recommended eviction of any bats living near humans, and others have even mandated removal of backyard bat houses. Are such actions justified? Let’s examine the facts.

Only two diseases have been transmitted from bats to humans in North America: histoplasmosis and rabies. Histoplasmosis is a respiratory disease caused by a fungus that grows in soil enriched by animal droppings, most frequently birds. Ninety percent of all reported cases in humans come from the Ohio and Mississippi River valleys and adjacent areas where warm, humid conditions favor fungal growth. The disease is rare or nonexistent in most of Canada and in the far northern and western U.S. The vast majority of cases are asymptomatic or involve no more than flu-like symptoms, though a few individuals become seriously ill, especially if exposed to large quantities of spore-laden dust. To be safe, simply avoid breathing dust in areas where there are animal droppings.

Rabies is a viral infection of the central nervous system and is easily prevented by vaccination. The modern rabies vaccine ranks among the safest and least painful of all vaccines and provides excellent protection. Anyone who handles wild animals should obtain pre-exposure immunization, and anyone bitten or exposed to the saliva or nerve tissue of a rabies-suspect animal should immediately obtain post-exposure treatment. This treatment has been simplified and no longer requires a lengthy series of shots in the stomach as it did in the past.

Worldwide, more than 30,000 humans die from rabies each year, and 99 percent of these deaths are due to contact with rabid dogs. In modern countries, where most dogs and cats are now vaccinated against rabies, the disease is rare in humans. For example, only about one person per year contracts rabies in the U.S. Dog bites remain the most frequent cause for vaccination in North America, but fatalities more often result from contact with wildlife, which is less likely to be reported and treated.

Inexplicably, a strain believed to be associated with the silver-haired bat (Lasionycteris noctivagans), based on monoclonal antibody tests, now accounts for the majority of all North American human rabies cases. How this rare transmission occurs remains a mystery, since silver-haired bats seldom contact people and do not form colonies in buildings or bat houses. Such cases typically cannot be traced to any known exposure.

The good news is that the North American bat species most frequently found in our homes or bat houses, big and little brown bats (Eptesicus fuscus and Myotis lucifugus), are not known to have caused a single case of human rabies in the past 15 years. In fact, only four cases are believed to have come from common house-dwelling species in American history. Furthermore, contrary to occasional speculation, there is no evidence that bats living in buildings ever transmit rabies through parasites, the air, or fecal material.
Since 1980, 14 Americans have died of rabies contracted from bats, and eight of those were ascribed to silver-haired bats. Some cases could have been prevented—for example, the one involving a man who failed to report being bitten by a sick bat that he dunked in his beer during a barroom prank. Placed in perspective, we are hundreds of times more likely to die from riding a bicycle, falling down stairs, or hitting a deer while driving. In fact, dog attacks kill as many Americans annually as have died in the past 15 years from contact with bats. Death from bat rabies grabs headlines only because it is so rare.

Children should be taught to appreciate but never handle bats or any other wild animals. Only experienced animal rehabilitators, researchers, or educators should attempt to keep bats in captivity. Such people must be protected by pre-exposure immunization. Even newborn animals can be infected with rabies, and the virus can lie dormant in any mammal for many months before making it visibly sick or contagious. Rabies outbreaks in animals such as raccoons, skunks, and foxes are unaffected by, and independent of, the disease in bats. There is no evidence that outbreaks of rabies occur in bats, nor that the current incidence is any higher than in decades past. In bats, only occasional individuals succumb to the illness, and these typically remain nonaggressive, biting only in self-defense, if handled.

The odds of contracting rabies are virtually nonexistent for anyone who: 1) vaccinates family dogs and cats; 2) avoids handling wildlife; and 3) obtains prompt vaccination following any suspected exposure. It also makes sense to exclude bats from human living quarters, rarely a difficult task, even if bats live in the attic. There is no evidence to suggest that elimination of bats from buildings or bat houses would make any neighborhood measurably safer. In fact, loss of bats increases demand for pesticides that already threaten both human and environmental health. You can help by countering with facts when local media run needlessly scary stories.

– Merlin D. Tuttle
Founder and Executive Director

The silver-haired bat