Rabies: The Bites That Kill

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Dr. David J. Holcombe
Dr. David J. Holcombe

September 28th happens to be World Rabies Day, and a good time to discuss that affliction.  Rabies is a disease of animals caused by a virus of the genus Lyssavirus.  Although it is present in many species of wild animals—notably skunks, raccoons, bats, foxes and others—it can also affect dogs, cats and even deer and cattle.  The reservoir species, those in which the disease occurs regularly, can transmit the disease to any warm-blooded animal—including humans—through saliva from a bite.

 

Although the number of cases of rabies in humans in the United States is very small (4 cases in 2009 and 2 in 2010), untreated rabies is almost always fatal.  Worldwide, it is estimated that 55,000 people are killed by rabies each year.  Since the initiation of regular vaccination among dogs and cats in the United States, the number of cases in domestic animals has dropped dramatically and is now largely exceeded by cases in wildlife (92% in 2010).

 

Within wildlife populations, there are rabies virus variants typical of the host animal, but communicable to other species.  Of the over 6,000 rabies cases reported in the United States in 2010, the percentages varied as follows:  raccoons (36.5%), skunks (23.5%), bats (23.2%), foxes (6.9%), cats (4.9%), cattle (1.1%) and dogs (1.1%).  The distribution of infected wild animals varies significantly, with raccoon being infected on the East Coast, foxes in the Southwest (and Alaska), and skunks scattered around the West, Southwest, Central and Southern U.S.  Bats have a much wider, scattered distribution, and rabid bats can occur in almost any state, with a special concentration in Southeast Texas.

 

Once bitten, the onset of symptoms from rabies varies with the site of the inoculation.  Since the virus travels up the nerves to the brain, bites in the extremities are much slower to manifest themselves then bites to the face (where the distance to the brain is much shorter).  Early signs include headache and fever, followed eventually (in weeks or months) by confusion, hallucinations, hyper-salivation, hydrophobia (fear of water), and ultimately, death.  Timely delivery of prophylactic medications, which includes Rabies Immune Globulin at the site of the bite and Rabies Vaccine by injection at days 0, 3, 7 and 14, will stop the progression of the disease.  Deaths in humans result from delays in seeking medical assistance, usually because the victim is unaware of the initial bite (as might occur from a bat).

 

Despite the few cases of rabid domestic animals, dog and cat bites still occur very frequently, somewhere between 1.5 and 3.5 million a year.  Almost 1% of animal bites treated in emergency rooms require hospitalization.  If the dog, cat or other animal cannot be located, or has no documented history of up-to-date rabies vaccination, then rabies prophylaxis (immune globulin and vaccine) should always be recommended, despite the cost of over $1,000.  An alternative is to quarantine the animal for ten days and if any signs of rabies develop, to sacrifice the animal and have its brain examined at the State Laboratory of the Office of Public Health.  All wild animals should be considered rabid and prophylaxis initiated unless they can be captured, euthanized and tested.

 

A terrible dilemma occurs when the animal is a beloved pet that has bitten a child on the face, and prophylaxis should not be delayed.  The owner must make the painful decision of inflicting medical treatment on the child or sacrificing the animal for a more rapid answer to the question of rabies infection.  Up-to-date vaccinations in all pets would make such a heartbreaking choice unnecessary.

 

To prevent rabies from killing animals or people, always vaccinate your pets, keep them from wild animals, report strays and enjoy wildlife from a distance.  For children, “Love your own pets, leave others alone” should be the rule.  If you travel, remember that rabies is still very common worldwide and you should never pet stray dogs on the roadside in some distant village.  Getting correctly treated for rabies prophylaxis in such circumstances could prove difficult or impossible.

For more information, visit: www.worldrabiesday.org, www.cdc.gov/rabies, and www.dhh.louisiana.gov/assets/oph/Center-PHCH/Center-CH/infectious-epi/Annuals/LaIDAnnual_Rabies.pdf