1997 Rabies Annual Summary
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Director, Rabies Laboratory
Richard Raczkowski:
Asst. Director, Rabies Laboratory
518-869-4527
Please contact us (518-869-4527) for data tables and image maps in an alternate format.
- Introduction
- Specimens Tested
- Rabies in Domestic Animals
- Raccoon Rabies
- Bat Rabies
- Human Serological Testing
- Rabies in Gray Foxes
- 1997 Rabies Incidence Map (GIF 14k)
- 1997 Bat Rabies Map (GIF 75k)
- 1997 Raccoon Rabies Map (JPG 153k)
- Additional 1997 Graphical Rabies Data
Introduction
The distribution of animal rabies in New York State during 1997 can best be described as diverse. The range in species affected by rabies is evidenced by the confirmation of cases in twenty different species during the year: 7 terrestrial wildlife species, 7 domestic species and 6 species of bats. Geographically, the raccoon rabies outbreak that spread into the state in 1990 continued to spread into the few remaining unaffected areas, so that by year's end it had been confirmed in 58 of the state's 62 counties. Rabies in bats during 1997 was reported from 64 different towns in 34 counties. Seasonal distribution of cases was also widespread: more than fifty confirmed terrestrial rabies cases occurred in each month of the year; bat rabies was confirmed in every month except January. The peaks of rabies cases in raccoons, bats, and skunks occurred in spring, summer, and fall respectively
Testing Results
There were 10,369 animals examined in New York State during the year for evidence of rabies infection: 9,449 at the Wadsworth Center Rabies Laboratory, and 920 at the New York City Department of Health. Sixty-four different species of mammals were received for rabies diagnosis in 1997. Domestic cats were most frequently tested, accounting for 2,569 or 25% of all specimens received, followed by bats (2,368, 23%), raccoons (2,019, 19%), and skunks (642, 6%). Overall, 22% of all animals received had reportedly bitten a person, 25% were involved in a non-bite human contact, 35% a domestic animal exposure, and 22% were non-contact surveillance specimens.
Rabies infection was confirmed in 1,266 animals in the state during the year, for an overall positivity rate of 12% among all animals tested. Rabid raccoons accounted for 836 of the cases, or 66% of the total, followed by 236 skunks (19%), 79 bats (6%), and 43 gray foxes (3%). The total cases in skunks and gray foxes for the year were the greatest annual totals recorded for those species in New York. Rabies also was confirmed in 10 red foxes, 10 woodchucks, 2 bobcats, and 2 opossum.
Rabies in Domestic Animals
In domestic animals, rabies infection was identified in 21 cats, 15 cattle, 5 dogs, 2 goats, 2 horses, 2 sheep and 1 rabbit. Rabies was far more common in cats than dogs, as it has been each year and cumulatively (207 rabid cats, 45 rabid dogs) since 1990. Wild species accounted for 96% of rabid animals, but only 63% of all animals tested, while domestic animals accounted for only 4% of rabies cases but 37% of all examinations. Among rabid animals, 6% of those received had reportedly bitten a person, 21% were involved in a non-bite human contact, 65% a domestic animal exposure, and 25% were non-contact surveillance specimens.
Rabies in Raccoons
The raccoon rabies outbreak spread into new areas of Lewis, Jefferson, Essex and Clinton counties during the year, and entered St. Lawrence County for the first time. The outbreak has now affected 871 different towns or cities in the 58 counties involved thus far, with only Franklin County in northern New York, Kings County (Brooklyn) in New York City, and Nassau and Suffolk counties of Long Island as yet unaffected. For the first time since 1991 there were no terrestrial rabies cases reported from the five boroughs of New York City. Overall, the number of rabid raccoons (836) increased 22% from the 1996 total (668), and the rabies positivity rate among all raccoons examined was 41%, up significantly from 33% in 1996. The percent rabid among those raccoons with reported human contact (40%) was similar to the overall rate in raccoons, but 66% (454 of 687) of raccoons that fought with a domestic dog were rabid. The cyclic nature of the raccoon rabies epizootic was made apparent by the observation that among 56 New York counties previously affected by the outbreak, 24 experienced more cases in 1997 than in 1996, 20 had fewer cases than in the previous year, and 12 were unchanged.
Rabies in Bats
Rabies in bats was again the preeminent rabies-related public health issue of 1997 nationally, as all of the four human rabies deaths during the year were the result of infection with bat rabies variants (3 with the variant associated with silver-haired and pipistrelle bats, 1 with the variant associated with the common big brown bat). In none of the cases, which occurred one each in Montana, Washington, Texas and New Jersey, was there a history of a bat bite or other animal bite, but in three of the cases there had been an indoor encounter with a live bat in the months preceding onset of rabies.
The 79 rabid bats in New York in 1997 were widespread geographically and by species, with cases in 34 of the state's 62 counties and in 6 of the 9 indigenous bat species. Overall, 3.3% of the 2,368 bats examined were rabid. The big brown bat accounted for 1510 (64%) of the bats examined and for 72 (91%) of the rabid bats. Other rabid bats included 2 little brown bats, 2 Keen's bats, 1 hoary bat, 1 red bat, and 1 silver-haired bat. The rabies positivity rate among big brown bats was 4.6%, for little brown bats 0.3%. Cumulatively since 1981, rabies positivity rates among all submitted bats has been 4.0% (n=23,148), among big brown bats 5.7% (n=13,970), and little brown bats 1.0% (n=7,050). Among the 2,337 bats received at the Wadsworth Center during 1997, 527 (23%) had a reported contact with a human, 719 (31%) had cat contact, and 189 (8%) contact with a dog. Among the 77 rabid bats examined at Wadsworth, 25 (32%) had human contact, 25 (32%) cat contact, and 11 (14%) had dog contact.
Human Serological Testing
There was a dramatic increase in the number of samples received at the Wadsworth Center Rabies Laboratory for serologic testing of human serum to determine the need for rabies vaccination booster injections. The 2,516 tests on human sera was 55% greater than the 1996 total, and 85% greater than the average for the previous 5 year period. The laboratory also tested 588 animal sera, largely in support of trials of the efficacy of oral rabies wildlife vaccination conducted by the College of Veterinary Medicine at Cornell University and the New York State Department of Health. The Wadsworth Rabies Laboratory performed 188 monoclonal antibody panel analyses for the antigenic characterization of the rabies virus variant associated with cases. These tests were performed on cases in unusual species or locations, domestic animal rabies cases and all rabid bats. All wild and domestic terrestrial mammals analyzed were found to be infected with the raccoon rabies variant of rabies virus, and all rabid bats were infected with one of the four bat rabies variants commonly identified in northeastern insectivorous bats.
Rabies in Gray Foxes
There were 43 rabid gray foxes in the state during 1997, from 27 different counties. A surprising proportion (58%) of these were involved in actual attacks on humans, that resulted in 19 bites and 6 non-bite human exposures (in contrast to a 23% human exposure rate among rabid raccoons during the year). The gray fox rabies cases are not the result of an independent cycle of rabies in that species, but spillover of the raccoon rabies into the foxes. This is evidenced by the widespread geographic distribution of the cases, as well as the antigenic identification of the rabies variant in each fox case examined as the raccoon rabies virus.
(New York City data provided by Dr. Igbal Poshni, Director, Virus Laboratory, New York City Department of Health)