Thursday, September 30, 2010

Are Wild Rats Carrier of Rabies?

Moki is my fist ever wild rat raised from pinkie.

“Small mammals such as squirrels, rats, mice, hamsters, guinea pigs, gerbils, chipmunks, rabbits, and hares are almost never found to be infected with rabies and have not been known to cause rabies among humans in the United States. Bites by these animals are usually not considered a risk of rabies unless the animal was sick or behaving in any unusual manner and rabies is widespread in your area.” -Centers for Disease Control and Prevention


If you’re bitten by a wild rat, chances are… you DID NOT contract rabies. In the United States, the animals that most frequently tested positive for rabies are raccoons, skunks, bats, and foxes, cats, and dogs (in decreasing order of importance) (Krebs et al. 2002). Dogs, cats and cattle account for 90% of rabies cases in domestic animals. The remainder of these cases comes from horses, sheep, mules, goats and ferrets. 

It is extraordinarily unlikely that rats would carry and transmit rabies to humans and other animals. Some speculate that when they are bitten by larger rabid predators, they almost always end up outright dead from the fatal wounds.


Animals infected with rabies may not initially appear mad: drooling and attacking people. The virus may appear in the animal's saliva only days before serious symptoms begin. It may become restless and irritable at first; eventually, it suffers from hydrophobia (fear of water) and starts attacking people. In humans, the symptoms of rabies fall into three stages. Symptoms usually occur from 10 days to a year.
  1. The invasion stage: pain in the wound, fever, headache, rapid pulse, anxiety, restlessness, insomnia and phases of rushed speaking
  2. Excitation stage: mental excitement and the overproduction of saliva; difficulty swallowing and drinking, hydrophobia
  3. Paralysis stage: hemiplegia (meaning one side of the body is paralyzed) or paraplegia (the lower limbs of the body are affected). If the patient ever reaches this stage, he or she usually slips into a coma and dies.


Winkler (1973) found in several literature that there were only 18 reports of rabid rats from 1953-1970. And as the years progressed within this 18-year period, positives declined in numbers.

Rats and other small rodents have never caused any case of rabies infection in the US. About 2% of cases of animal rabies involve other wild animal species, including large rodents, rabbits and hares (Krebs et al. 1999). In the 368 human cases of rabies caused by large rodent bites (95%) and rabbit bites (5%) between 1985 and 1994 in the United States, 86% were caused by woodchucks (Childs et al. 1997).

In several surveys of the wild rat populations of Poland (2002), Sri Lanka (2003), and Thailand (2003) -- none were found to be infected with rabies. Only isolated cases of rats infecting humans with rabies were reported in countries such as Poland, Surinam, Israel and Thailand. 

In Poland, out of 9,998 cases of human rabies from 1990 to 1994, only four were caused by rats (0.04%), while the vast majority was caused by foxes (ZmudziƱski and Smreczak 1995, described in Wincewicz 2002).

In Israel, one case of human rabies was caused by a bite from a small rodent -- possibly a rat or mouse (Gdalevich et al. 2000).

In Thailand, out of 7,000 human rabies cases reported each year, 1% are caused by rat bites (Kamoltham et al. 2002). The majority of rabies cases in Thailand are caused by dogs (86.3%) (Pancharoen et al. 2001). An outbreak of paralytic rabies in children in Surinam was attributed to rat bites (Verlinde et al 1975).

Ukraine (2009), a taxi driver was attacked by a rat. It was killed and brought in for investigation, which tested positive for rabies. The driver was given anti-rabies shots and the neighborhood was given two-week quarantine. Valentina Stulova, head of the veterinary department, assures that it is not an emergency situation and is only standard practice to prevent further spread into the population.

A middle-aged woman in Jakarta died of rabies (2010), which was attributed to a rat bite two months prior to her death. Dr. Mahardika asserts that dogs are the main agents of transmitting the virus to humans. While pathology tests were pending, Dr. Sudiartha, (from the Rabies Center of the hospital), told that “90% of rabies cases in Indonesia were [massively] due to dog bites … cases linked to rats are unheard of.”


From my experience of handling wild rats, I've never seen any one with rabies and such cases are unheard of. They might probably need some de-worming and isolation first because they've been travelling everywhere. But definitely, rabies was never an issue.

“Wild rats have never caused rabies to humans in the United States, and only extremely rarely in other countries. Rats are therefore not considered a serious rabies risk. Rabies shots are not considered necessary after a rat bite (Jaffe 1983). Since 1969, the Public Health Service has advised that "bites of rabbits, squirrels, chipmunks, rats, and mice seldom, if ever, call for rabies prophylaxis" (CDC 1969).”

Further Reading:

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