By Ethan Covey
In 2023, a stray kitten in Nebraska died of rabies caused by the Eastern raccoon rabies virus variant (RRVV) approximately 850 miles west of where this form of the virus is usually found, according to a recent report.
The case represents the westernmost detection of RRVV in a stray or wild animal in the United States. A raid, extensive public health response, which included intensive wildlife vaccination efforts, identified no additional cases over a 10-month period, suggesting that RRVV has not become established in wildlife in Nebraska (MMWR Morb Mortal Wkly Rep 2024;73[41]:933-935).
While officials are unsure how the rabies variant got to Nebraska, previous outbreaks have been caused by the movement of animals into new geographic areas.
“When people move wildlife, it can have significant health and ecosystem impacts,” said Ryan Wallace, DVM, MPH, a veterinary epidemiologist with the CDC’s Poxvirus and Rabies Branch. “One of the largest wildlife disease outbreaks in recorded history occurred when infected raccoons in Florida were moved by people to the mid-Atlantic states, which moved raccoon rabies virus variant as well.
“This occurred in the 1970s, and today USDA [U.S. Department of Agriculture] and CDC are still trying to contain the outbreak,” Dr. Wallace added. “There are few reports on how often people move animals who are infected with rabies virus variants, or what the impact of such movement is. This recently published report details the risks, the level of response necessary to mitigate spread and the likely impact preventing raccoon rabies virus expansion has on human health.”
The kitten, which was approximately 6 weeks old, died with neurologic signs and having bitten and scratched its caretakers. On Sept. 28, 2023, tests conducted by the Nebraska Veterinary Diagnostic Center were positive for rabies. Variant-typing subsequently confirmed RRVV.
On Oct. 14, 2023, the Nebraska Department of Health and Human Services, Douglas County Health Department, CDC, and USDA initiated extensive field activities. While the activities were unable to confirm any information regarding the kitten’s origin, no further exposures were identified.
“Detailed surveillance, and in this case, an intensive vaccination campaign, in Nebraska wildlife ensured this variant did not become established in the Midwest,” Dr. Wallace said. “This surveillance helps public health officials understand if new forms of rabies have moved into new geographic areas, which could result in large outbreaks in animals, expensive medical costs for people and human deaths from rabies.”
The response was aided by new techniques that allowed for such a prompt investigation.
“Due to the long and variable incubation period of rabies virus, it can take months or longer before routine surveillance systems detect spread within wildlife populations,” Dr. Wallace said. “If this response were to have relied on these routine surveillance methods, the virus would likely have been too established for mitigation efforts to eliminate rabies from Nebraska wildlife to be successful. We used new methodology to determine a statistically significant sample size of ACTIVE surveillance sampling, which turned out to be critical to intervening quickly.”
Additionally, a CDC grant aided Nebraska in their surveillance efforts, highlighting the importance of funding.
“Rabies is an endemic disease in the U.S., and federal support for states to operate rapid and effective laboratory-based surveillance systems has declined in the last decade,” Dr. Wallace said. “This case was detected rapidly only through a very small grant CDC provided to the state to offer selective rabies virus variant typing. Without this small grant, the case likely would not have been identified as raccoon variant, significantly delaying any field-level response.
“This report emphasizes the importance of adequate local and state rabies funding, and the importance of having a national reference laboratory to inform large-scale public health and animal health actions,” he continued. “This report highlights the use of a new, experimental, field-based rabies test and the distribution of oral rabies vaccines for wildlife. Both the test and the oral rabies vaccine are relatively new, and more research into improving their performance and reducing their costs would have broad benefits for rabies control and wildlife health.”
Dr. Wallace reported no relevant financial disclosures.
