On July 24, 2017, the Ohio Department of Health learned that a domestic cat in Summit County had tested positive for rabies. That was alarming, because Summit County is considered free of terrestrial rabies. Each year, bait laced with oral rabies vaccine is dropped for raccoons along the Ohio–Pennsylvania border to keep the raccoon rabies virus variant from spreading west, and the cat had been found on the far side of that barrier. Had raccoon rabies broken through?
It had not. Investigators found that the cat had come from North Carolina, and genetic analysis showed its virus matched the raccoon variant circulating there. The virus had been carried across the country by people, not spread by wildlife.
The cat's journey
The raccoon variant is one of several distinct rabies virus variants in the United States. It is entrenched across the eastern United States, from Florida to Maine, and in a few counties of northeast Ohio. Rabies vaccination protects animals against every variant.
The cat, referred to as cat A, had been one of several strays a couple took in as pets while living in North Carolina:
- Early February 2017: the two adults left North Carolina for Arkansas with two dogs and 13 cats.
- February 17–21: they traveled from Arkansas to Summit County, Ohio, to stay with family. The cats were kept in a garage and not allowed outside, with no known contact with other mammals. Cat A and another cat had kittens there, several of which died of unknown causes.
- April 28–May 3: no longer able to care for them, the owner surrendered 15 cats, including cat A and her four kittens, to the Humane Society of Summit County. The shelter gave routine vaccines and care, but it gives rabies vaccine at the time of spaying or neutering, so cat A was not vaccinated.
- May 5–July 11: cat A and her kittens stayed in a temporary home. She was treated for an upper respiratory infection, and on July 8 she was reported to be making abnormal vocalizations, which were attributed to estrus.
- July 18: almost 5 months after reaching Ohio, cat A began panting heavily, grew agitated, breathed with her mouth open and lost coordination in her hind legs. She declined rapidly and was euthanized on July 20.
No one had been bitten and there was no sign cat A had met a rabies-carrying animal, but her head was sent for testing anyway. The state laboratory confirmed rabies the day it received the sample.
Tracing the virus
With CDC, Ohio characterized the virus. Antigen typing identified the raccoon variant, and analysis of the virus's N gene placed it closest to a group of viruses found only in central North Carolina — where cat A had been picked up as a stray. None of the other cats developed signs of rabies. Cat A had most likely been infected as a stray and incubated the virus for at least 5 months, longer than the typical 3 weeks to 3 months.
On the way, she passed through eight states. Three of them — Arkansas, Indiana and Mississippi — are free of terrestrial rabies and have no enhanced federal rabies surveillance. Had she died in one of them, with no clear human exposure, routine surveillance would probably have missed the case. Had she become infectious during the trip, an outbreak among animals could have followed.
Protecting people and animals
Investigators focused on the period when cat A could have shed virus, from July 8 to July 20. Of 29 people who might have had contact with her, 26 were found and assessed. Four were advised to get post-exposure prophylaxis: three humane society staff and the adult caring for her in the temporary home, because of likely contact with saliva (for example, while giving oral medicine), uncertainty over bites or scratches, or a possible lapse in infection control during the removal of her head for testing.
The other 14 cats had been adopted or placed in care across 12 households. Cat A's kittens were presumed exposed through grooming and nursing, and the 10 cats from the garage were treated as potentially exposed to the same source in North Carolina. Six had been too young for rabies vaccine. All 14 were placed in strict quarantine for 6 months, and as of May 7, 2018, no further rabies cases had been linked to them.
Why it mattered
The U.S. Department of Agriculture's Wildlife Services spends more than $20 million a year on oral rabies vaccination in the eastern United States. Summit County lies within its zone of enhanced surveillance, so a breach there is taken seriously. If the evidence had pointed to raccoons spreading rabies naturally, an emergency baiting operation would probably have followed. Because the virus had evidently been carried in by people and the case was quickly contained, extra baiting was judged unnecessary. The genetic evidence therefore spared a costly emergency response.
The risk is real. Rabid raccoons moved by people from Florida to Virginia in the 1970s, and from Vermont to Hamilton, Canada, in 2015, set off large wildlife outbreaks whose control continues today. CDC estimates that rabies diagnosis, prevention and control cost U.S. public health $245 million to $510 million a year.
None of the 13 cats brought from North Carolina had a known rabies vaccination. Federal and state rules require rabies vaccination and a veterinary health certificate before animals cross state lines, but those rules are hard to enforce. Rabies is rare in vaccinated animals, and the authors conclude that vaccinating cat A when she was taken in, and before travel, could have prevented the whole event.
Sources
- Amber J. Singh, Richard B. Chipman, Sietske de Fijter, Richard Gary, Marilyn G. Haskell, Jordona Kirby, Li Yu, Rene E. Condori, Lillian Orciari and Ryan Wallace, "Translocation of a Stray Cat Infected with Rabies from North Carolina to a Terrestrial Rabies-Free County in Ohio, 2017," Morbidity and Mortality Weekly Report, CDC, with its published erratum: https://www.cdc.gov/mmwr/volumes/67/wr/mm6742a2.htm
- The report's figures, prepared with the Ohio Department of Health, are not reproduced.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
1
0
0
0
Comments
