CHICAGO Rats, often hosts to diseases from the bubonic plague to tetanus, tend to bite sleeping victims and since younger children spend more time sleeping, they suffer the most bites. A study of Philadelphia neighborhoods from 1974 to 1996 examined 622 confirmed rat bites, primarily suffered by poor children younger than 5 years old bitten on the face or limbs. Most bites occurred between midnight and 8 a.m.

when the victims were sleeping, researchers the Philadelphia Department of Public Health wrote in the journal, Pediatrics. Analyzing census data just for victims under age five, the researchers found the rate of rat bites declined from 65 per 100,000 population from 1974 to 1984, to 16 incidents per 100,000 from 1985 to 1996. Children aged 5 to 9 were the next most likely victims, with susceptibility generally declining with age.

The Norway rat's usual urban habitat is sewers, but breaks in Philadelphia's ageing 2,900 miles (4,700 km) of sewer lines provides escape routes for the burrowing animals and they often end up living off garbage in and around the basements and kitchens of dilapidated homes. Apartment dwellers were less likely to suffer bites, as rats rarely ascended stairs, the researchers wrote.

Besides harboring the legendary scourges bubonic plague and typhus, rat urine can infect humans with leptospirosis, or infectious jaundice, and rat excrement can spread trichinosis and salmonellosis. Bacteria found on the gums and teeth of rats can cause various fevers and tetanus. Researchers Randall Hirschhorn and Robert Hodge recommended treating a rat bite like a surgical wound. (Reuter)