John Berryman (1914–72), U.S. poet. Dream Song 63, in The Dream Songs (1969).

Man and bats have lived in close proximity since the very earliest of our gaining the distinction of being a species of our own. Our current domiciles and workplaces appear to bats much as the caves we shared in past generations. Bear in mind, that though I speak a word of caution in our dealings with bats, that bats occupy an valuable niche, from the human perspective. They consume a substantial bio-mass of mosquitoes, and thereby aid in controlling a vector of other important human diseases e.g. West Nile Virus encephalitis. Insectivorous Silver-haired, Pipistrelle and Brown bats native to Iowa migrate south to tropical climates in Latin America where they interact with rabies infected vampire bats. The long incubation period and internecine transmission provides for a substantial rate of rabies among these bats in Iowa. While the true incidence of rabies in the bat population is not known, It is not unusual for 10 – 15% of bats examined in Iowa to have evidence of rabies.

If by sentinel event, we mean a tragedy, which knowledge of the firmest of science could have predicted, then the death of an Iowan September 28, 2002 from encephalitis caused by a strain of rabies virus found almost exclusively in bats should be regarded as a sentinel event. This diagnosis was confirmed by Direct Fluorescent Antibody (DFA) staining for rabies virus antigen and was positive by reverse transcriptase polymerase chain reaction (RT-PCR) for rabies virus RNA. DNA sequence analysis revealed a virus variant found in either the silver-haired or the eastern pipistrelle bat. Neither a history of exposure nor of a bat encounter was elicited in this case.

For over a decade now 78% of all cases of rabies has occured in the absence of any history of animal bite. This was the case in all but 7 of the last 35 cases of human rabies in the USA.

From 1990 through 2002 the CDC documented 27 cases of human rabies caused by strains known to be associated with bats. These strains do occasionally infect other mammals capable of transmitting the disease to humans. In three of these cases a history of bat bite was obtained. There are 24 cases with no known source of exposure (NKSE). In 14 of these 24 cases there was a history of a non-bite bat encounter. Several of the encounters are characterized: examining the teeth of a killed bat (1), bite or sting at night while gardening, (1), wakening with a bat on the body (2), capturing or disposing of bats (4), bats in the room (6). There was one exposure to sick dying cat, and one exposure to a sick cow that died.

The CDC position statement:

Morbidity and Mortality Weekly Report
Recommendations and Reports March 21, 2003 / Vol. 52 / No. RR-5 department of health and human services
Centers for Disease Control and Prevention
Compendium of Animal Rabies
Prevention and Control, 2003
National Association of State Public Health Veterinarians, Inc.
(NASPHV)

“Bats. Indigenous rabid bats have been reported from every state except Hawaii, and have caused rabies in at least 36 humans in the United States (18). Bats should be excluded from houses and adjacent structures to
prevent direct association with humans (19,20). Such structures should then be made bat-proof by sealing
entrances used by bats. Controlling rabies in bats through programs designed to reduce bat populations
is neither feasible nor desirable.”

Reconciled to deal with rabid bat encounters, the definition of rabies exposure is a subject worthy of a careful examination here in Iowa. There is an absence of any scientific evidence that rabies can be transmitted by aerosol. Non-the less, it would be wise for speleolists to obtain pre-exposure prophylaxis. It being unclear how so many people with no know exposure to a bat strain of rabies acquired the virus, one can only speculate based on the encounters described earlier. It can be difficult to determine whether an encounter with a bat or a suspicion of an exposure justifies prophylaxis. The safety and efficacy of the vaccine and HIRIG if properly timed is excellent. Prudence then would direct the physician to a low threshold for recommending prophylaxis. Russell W. Currier, DVM, MPH an Environmental Epidemiologist at the Iowa State Health Department has been a valuable resource to those of us who grapple with these questions for over 28 years.

The exclusion of possible rabies exposure by examination of the bat can be a very useful strategy. However a technique by which a live flying bat can be safely captured and brought to examination without exposing oneself to infection and without rendering the specimen un-suitable for viral studies has not been promulgated by any authority I am aware of. Bats should not be violently swatted from the air or crushed, nor should they be handled bare handed. Specimens should be refrigerated but never frozen. Bats, don’t want to live with them, but don’t want to live without them either.

Additional references furnished on request.