Who's still worried about rabies?
Rabies has been a public health issue in the United States almost since the beginning of the nation itself. It appears that the disease originated in the Old World (i.e. Europe) with the first outbreak likely in Boston in the late 1700s. Since then, great strides have been made in the control and prevention of the disease as the mystery of the virus’s epidemiology has been illuminated. These days, post-exposure prophylaxis no longer includes removing the frenulum linguae (the mucous membrane that attaches the tongue) in an effort to remove the “tongue worm” or repeatedly submerging the patient in a pond or hot oil when a pond is not available.1 Thank goodness!
From “mad dogs” to wildlife
For centuries, it was clear that encounters with “mad dogs” were responsible for most transmissions to humans, even though little else was accurately understood for some time. In fact, up until as recently as the 1960s, dog bites were the most common cause of rabies in people in the United States.2
Since then wildlife reservoirs have become the predominant source of rabies outbreaks and subsequent human exposures in the United States. In the last four decades, domestic animals have been replaced by wildlife as the most commonly reported sources of human exposure, and true elimination of the disease in free-ranging wildlife seems unlikely. Skunks, foxes, raccoons and bats remain rabies reservoirs in carious regions of the United States.
Despite the fact that rabies continues to provide a public health threat, many veterinary practitioners fail to recognize its persistence. But practitioners aren't the only ones wearing rose-colored glasses and forgetting that vaccination alone is not the “silver bullet” for continued control of this nearly 100 percent fatal disease. If vaccination is the foundation of rabies control, then animal control is the cornerstone of that foundation. Indeed, the eventual elimination of the massive population of stray dogs contributed at least as much as vaccination campaigns to the elimination of canine rabies in the United States.1
The rise of the rabid cats
Thanks to significant programs for animal control, stray dogs no longer roam the streets in large packs ripe for disease maintenance and transmission. Dogs are no longer the most commonly reported rabid domestic animal—cats now have a firm hold on the title. Cats were reported rabid four times more than dogs in recent years.2 Despite the ready availability of an efficacious vaccine (several vaccines, in fact), why are cats standing atop the rabies leaderboard among their domestic peers? The cause is likely multifactorial.
Cats aren't routinely seen by veterinarians for preventive care. In fact, by some estimates, nearly 50 percent of owned cats aren't seen for vaccinations. Surely this miscalculation of the import of routine care by cat owners is significant and contributes to the increase in reported rabid cats. But many cat owners keep their cats indoors exclusively, thereby severely limiting their rabies exposure. Still, other owners complete the kitten vaccination series and simply fail to maintain preventive care in adult cats, likely providing some rabies immunity through initial vaccination.
An oft ignored, but increasingly more significant variable in the rise of felines in the rabies world is support for allowing large populations of stray cats to persist in urban areas. In an incredible show of “rabies amnesia,” some municipalities allow or encourage feeding of stray cats to support the populations. Many stray cat populations are maintained by charity groups or individuals at surprisingly significant financial cost. Such stray cats are trapped, neutered, vaccinated for rabies and then subsequently re-abandoned postoperatively. Setting aside the welfare implications of such treatment, these “TNR” programs do not effectively prevent or control rabies in these stray cat populations as originally posited.3
Where do we go from here?
Since stray dog population control was a cornerstone in the elimination of canine rabies in the United States and its subsequent persistent control, it stands to reason—and peer-review—that stray cat population control will be key in significantly decreasing rabies in cats as well. Despite the growing popularity of stray cats, it’s important to remember that rabies remains a real public health threat in the United States. Rabies has no consistently effective clinical treatment or cure to date. Our only response centers on the prevention of the onset of clinical signs with aggressive prophylaxis in people and exposed pets. People aren't reported as infected with rabies if appropriate postexposure prophylaxis (PEP) is completed. Thus, a great number of people are exposed each year in the United States, but the actual number of cases of human rabies reported in the United States is very low. These case numbers, or lack thereof, are misleading if one isn't careful and can present the rosy picture of a nation without rabies.
Alas, we have not yet eliminated the risk and should take care that animal control policies don't allow the threat to continue to grow in our communities. It's vital that veterinary practitioners get engaged with their local public health departments and with other municipal authorities to provide guidance when necessary for animal control decisions. Veterinary practitioners should also educate their clients on the risk of allowing pets (including cats!) to roam freely. Even a one-night adventure outside for a cat could be life-threatening for many reasons, including an encounter with a rabid skunk or raccoon. Keep your patients and their owners safe from rabies by educating folks about the risk of rabies that still exists in the United States.
1. Baer GM. The natural history of rabies. 2nd ed. Boca Raton, Florida: CRC Press, 1991;1-20.
2. CDC. Rabies in the U.S. and around the world. Available at: https://www.cdc.gov/rabies/location/index.html. Accessed on 7/22/17.
3. Roebling AD, Johnson D, Blanton JD, et al. Rabies prevention and management of cats in the context of trap, neuter, vaccinate, release programs. Zoonoses public health 2014;61(4):290-296.