Rabies historical perspective

Transport of pet animals between countries

Sign at a UK port showing rabies prevention measures aimed at merchant seamen

Rabies is endemic to many parts of the world, and one of the reasons given for quarantine periods in international animal transport has been to try to keep the disease out of uninfected regions. However, most developed countries, pioneered by Sweden, now allow unencumbered travel between their territories for pet animals that have demonstrated an adequate immune response to rabies vaccination.

Such countries may limit movement to animals from countries where rabies is considered to be under control in pet animals. There are various lists of such countries. The United Kingdom has developed a list, and France has a rather different list, said to be based on a list of the Office International des Epizooties (OIE). The European Union has a harmonised list. No list of rabies-free countries is readily available from OIE.

However, the recent spread of rabies in the northeastern United States and further may cause a restrengthening of precautions against movement of possibly rabid animals between countries.

Rabies and dogs

Rabies has a long history of association with dogs. The first written record of rabies is in the Codex of Eshnunna (ca. 1930 BC) (written prior to the Code of Hammurabi), which dictates that the owner of a dog showing symptoms of rabies should take preventative measure against bites. If a person is bitten by a rabid dog and later died, the owner was fined heavily.

Three stages of rabies are recognized in dogs. The first stage is a one to three day period characterized by behavioral changes and is known as the prodromal stage. The second stage is the excitative stage, which lasts three to four days. It is this stage that is often known as furious rabies due to the tendency of the affected dog to be hyperreactive to external stimuli and bite at anything near. The third stage is the paralytic stage and is caused by damage to motor neurons. Incoordination is seen due to rear limb paralysis and drooling and difficulty swallowing is caused by paralysis of facial and throat muscles. Death is usually caused by respiratory arrest.

Rabies and opossums

Experimental studies of rabies infection in the Virginia opossum have shown the importance of the mode of transmission. Opossums became infected when exposed to air-borne virus but were found to be fairly resistant to intramuscular inoculations .The aerosol transmission of rabies in opossum was investigated following the death from rabies of two men who had visited the Frio Caves, Texas, and did not remember any direct contact with bats.

The spatial and temporal distribution of opossum rabies

Rabies cases in the Virginia opossum are spillover cases from other wildlife species such as bats,skunks and the raccoon epizootic in the eastern United States. Cases have been reported across the United States from California to New York . In New York state, the Wadsworth Center lists laboratory confirmed cases in opossums 5 years out of 10 from 1989 to 1998.

Rabies and domestic skunks in the United States

There is currently no USDA-approved vaccine for the strain of rabies that afflicts skunks. When cases are reported of pet skunks biting a human, the animals are frequently killed in order to be tested for rabies. or Humans exposed to the rabies virus must begin post-exposure prophylaxis before the disease can progress to the central nervous system. For this reason, it is necessary to determine whether the animal, in fact, has rabies as quickly as possible. Without a definitive quarantine period in place for skunks, quarantining the animals is not advised as there is no way of knowing how long it may take the animal to show symptoms. Destruction of the skunk is recommended and the brain is then tested for presence of rabies virus.

Skunk owners have recently organized to campaign for USDA approval of both a vaccine and an officially recommended quarantine period for skunks in the United States.

Rabies and bats

The problem of bat-transmitted rabies is found over most of North and South America but was first closely studied in Trinidad in the West Indies which had a dreadful reputation for bat rabies, which took a significant toll of livestock and humans alike. In the 10 years from 1925 and 1935, 89 people and thousands of livestock had died from it - "the highest human mortality from rabies-infected bats thus far recorded anywhere.".

In early 1931, Dr. H. Metivier, a Veterinary surgeon, established the connection between the bites of bats and paralytic rabies. In September 1931, Dr. J. L. Pawan, a Government Bacteriologist found Negri bodies in the brain of a bat with unusual habits. In 1934 the Trinidad and Tobago Government began a program of vampire bat control, shooting, netting, trapping and poisoning, while encouraging the screening off of livestock buildings and free vaccination programs for exposed livestock.

After the opening of the Trinidad Regional Virus Laboratory in 1953, basic research on bats and rabies progressed rapidly under the able direction of Arthur Greenhall, who demonstrated that at least 8 species of bats in Trinidad had been infected with rabies - particularly the Common Vampire Bat, Desmodus rotundus (which "will attack any warm blooded creature"), the rare White-winged Vampire Bat, Diaemus youngi, (which "appears to have a special preference for birds and goats"), as well as two abundant species of Fruit Bats: the Seba's Short-tailed Bat or Short-tailed Fruit Bat, Carollia perspicillata, which commonly roosts with Vampires, and the Jamaican Fruit Bat, Artibeus jamaicensis.

Non-bite transmission of rabies to susceptible animals placed in bat-proof cages in a cave with bat colonies was demonstrated by Constantine in Frio Cave, Texas, as early as 1960. In 1967, rabies virus was isolated from the air in the same cave, presumably passed by the bats urinating, potentially forming a source for infection of other susceptible animals, and presenting a hazard to researchers and spelunkers. While the risks may be low, they are deserving of further study and monitoring.

The United Kingdom, which has stringent regulations on the importation of animals, had also been believed to be entirely free from rabies until 1996 when a single Daubenton's bat was found to be infected with a rabies-like virus usually found only in bats – European Bat Lyssavirus 2 (EBL2). There were no more known cases in the British Isles until September 2002 when another Daubenton's bat tested positive for EBL2 in Lancashire. A bat conservationist who was bitten by the infected bat received post-exposure treatment and did not develop rabies.

Then in November 2002 David McRae, a Scottish bat conservationist from Guthrie, Angus who was believed to have been bitten by a bat, became the first human to contract rabies in the United Kingdom since 1902. He died from the disease on November 24 2002.

In November 2004, Jeanna Giese, a fifteen-year old girl from Fond du Lac, Wisconsin, became one of only six humans known to have survived rabies after the onset of symptoms, and the first known instance of a human surviving rabies without vaccine treatment. Giese's disease was already too far progressed for the vaccine to help, and she was considered too weak to tolerate it. Doctors at the Children's Hospital of Wisconsin in Wauwatosa a suburb of Milwaukee, Wisconsin, achieved her survival with an experimental treatment that involved putting the girl into a drug-induced coma, and administering a cocktail of antiviral drugs. Giese had symptoms of full-blown rabies when she sought medical help, thirty-seven days after being bitten by a bat. Her family did not seek treatment at the time because the bat seemed healthy. Jeanna regained her weight, strength, and coordination while in the hospital. She was released from the Children's Hospital of Wisconsin on January 1, 2005.

On May 12, 2006 Harris County Texas. U.S.A. Health Department officials reported that a teenage boy, Zachary Jones of Humble, Texas, had died of rabies at Texas Children's Hospital in Houston, Texas. Zachary had contracted the disease after a bat flew in his bedroom and bit him in his sleep. He was unaware he had been bitten and was not hospitalized until he developed symptoms several weeks later. He died at Texas Children's Hospital after an attempt to cure the disease through a drug-induced coma, similar to that of Jeanna Giese.

On November 2, 2006 a 10 year old girl in Bourbon, Indiana, U.S.A. died of rabies. The Indianapolis Star reports that she was bitten by a bat in June 2006.

In August of 2006, a 73 year old rural resident located east of Edmonton, Alberta, Canada was bitten by a bat while he slept. He ignored the bite and became symptomatic in January 2007. Diagnosed with rabies in March of 2007, he was treated with the Milwaukee protocol, but died April 26, 2007.

On August 6, 2006, 950 Girl Scouts were urged to receive rabies shots by the Girl Scouts of America. The nine hundred and fifty girls had attended a camp in Virginia, U.S.A. in July, and had reported seeing bats in their cabins. Even though infections were relatively unlikely, the G.S.A. offered to pay for the shots, at a cost of nearly two million dollars. The Centers for Disease Control reports 27 cases of human rabies caused by the bat variant rabies virus in the United States from 1990 to 2002.

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