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1. RABIES

ESSENTIALS OF DIAGNOSIS

  • History of animal bite.

  • Paresthesias, hydrophobia, rage alternating with calm.

  • Convulsions, paralysis, thick tenacious saliva.

General Considerations

Rabies is a viral (rhabdovirus) encephalitis transmitted by infected saliva that enters the body by an animal bite or an open wound. Worldwide, over 17 million cases of animal bites are reported every year, and it is estimated that about 60,000 deaths annually are attributable to rabies. Rabies is endemic in over 150 countries; on the basis of interviews, it is estimated that over 40% of the world’s population lives in areas without rabies surveillance. Most cases of rabies occur in rural areas of Africa and Asia. India has the highest incidence, accounting for 36% of global deaths (http://www.who.int/rabies/epidemiology/en/). In developing countries, more than 90% of human cases and 99% of human deaths from rabies are secondary to bites from infected dogs. Rabies among travelers to rabies-endemic areas is usually associated with animal injuries (including dogs in North Africa and India, cats in the Middle East, and nonhuman primates in sub-Saharan Africa and Asia), with most travel-associated cases occurring within 10 days of arrival. Rare but related viruses are the Australian lyssavirus, transmitted by bats including one referred to as the black flying fox, and which has caused 3 deaths over the last 20 years, and the European lyssavirus, with cases from Germany and the United Kingdom.

In the United States, domestically acquired rabies cases are rare (approximately 92% of cases are associated with wildlife) but probably underreported. Reports largely from the East Coast show an increase in rabies among cats, with about 1% of tested cats showing rabies seropositivity. The annual caseload in the United States is 1–3 cases (https://www.cdc.gov/rabies/location/usa/surveillance/human_rabies.html). Surveillance for animal rabies in 2015 showed 5508 cases occurring in 49 states and Puerto Rico. Wildlife reservoirs, with each species having its own rabies variant(s), follow a unique geographic distribution in the United States: raccoons on the East Coast; skunks in the Midwest, Southwest, and California; and foxes in the Southwest and in Alaska. However, some areas have all three wildlife reservoirs (eg, the hill country of Texas) (eFigure 32–2). Hawaii is the only rabies-free state to date. Most of Western Europe and much of Oceania is rabies-free.

eFigure 32–2.

Map for rabies: Vector ecology associated with risk of rabies in the United States. (https://www.cdc.gov/rabies/exposure/animals/wildlife_reservoirs.html)

Raccoons, bats, and skunks account for 84% of the rabid animals found in the United States; other rabid animals include foxes, cats, cattle, and dogs. Rodents and lagomorphs (eg, rabbits) are unlikely to spread rabies because they cannot survive the disease long enough to transmit it (woodchucks and groundhogs are exceptions). Wildlife epizootics present a constant public health threat in addition to the danger of reintroducing rabies to ...

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