Of Rats & Men

"Some of your best friends are rats," declares the American Cancer Society in ads that hail the research variety's services to medical science. But the wild Rattus norvegicus is man's worst animal enemy. It bites his babies, inflicting deforming and infected wounds; it cuts down his food supply, and it spreads disease. It was used as an instrument of torture in the Middle Ages, and now it is torturing the Johnson Administration, which is trying to get Congress to enact a $40 million rat-control bill (see THE NATION).

The female rat is capable of breeding at four months, and usually produces four litters, each of six or more young, in her reproductive year. If all lived, one pair would have millions of descendants in two or three years, but the attrition is high enough to keep the numbers fairly constant. Estimates of the U.S. rat population (largely guesswork) range from 90 million to 100 million, or about half as many rats as people. For New York City, the estimates run as high as 8,000,000, or one rat per person. The U.S. Department of the Interior figures that a rat eats 40 Ibs. of food a year, and spoils twice as much. The nation's total rat damage is roughly $1 billion a year.

Sewer to Kitchen. Rats' appetites are a cause of human starvation. The World Health Organization puts the worldwide loss of stored cereals at 33 million tons a year--enough to feed some 200 million people. Rats in a silo may eat only a few bushels of grain, but their droppings and hair make a far greater quantity unfit for human consumption.

Despite doubts about the role of rats in long-ago typhus epidemics, there is no doubt that they and their fleas transmit what doctors call murine typhus, a milder but perennial and widespread form of the disease. In their travels from sewers to trash cans to kitchens, rats may carry the germs of epidemic jaundice, tularemia, typhoid fever and severe food poisoning, the parasites of trichinosis, and even rabies virus.

The rat's most distinctive contribution to human ill health comes from its bite. There are credible stories of men, exhausted and sleeping, or trapped in a mine shaft, being bitten to death by rats. Far more common today is the case of the city mother, awakened by a cry in the middle of the night, who finds her infant in his crib bleeding from rat bites on the nose, lips or ears. The rat usually flees on her approach and escapes. The child may suffer from either of two types of rat-bite fever or from many common infections.

Estimates of how many people are bitten each year in the U.S. run to 50,000 or more. New York City averages 600 reported cases a year. As in the rest of the U.S., 90% of the victims are young children.

Pets & Poisons. For all their misdeeds, rats are not really to blame. It is man who is at fault. "If we could only get people to keep the lids tight on metal garbage containers," says Clarence W. Travis of the District of Colum bia's Health Department, "we could wipe out the rats in six months. We put poison down in the alleys and distribute free poison to people in blighted areas, but they leave so much juicy, greasy garbage around that the rats pay no attention to the poison."

Travis complains that most people simply do not realize what attracts rats. Rich-smelling fried food left in an empty room is bait. So are dishes in the sink. So is the feeding of dogs, cats, squirrels and birds in the backyard. Among the worst offenders are construction workmen who throw away luncheon leftovers. "There hasn't been a building put up in Washington in 15 years that the rats didn't move into before the people," says Travis. "You have the exterminator working on the first floor by the time they're laying concrete on the second."

Since rats will eat anything, they should be easy to poison. But they are not. Psychologists explain that rats have two contradictory traits: along with a willingness to sample anything potable or edible, they have a deep suspicion of whatever is new. So exterminators give the rats time to get used to the sight and smell of their traps and baits before they expect results. Dogs and cats, despite their reputation, are not very effective as rat exterminators.

Arsenic, strychnine, phosphorus and thallium salts are effective rat poisons, but far too dangerous where there are children or pets. Probably the oldest of rat poisons is about the most effective and also the safest: red squill, from the ground root of a European plant. Mixed with freshly ground meat or fish baits, it is harmless to children, cats, dogs and even squirrels.

Perhaps still more potent, and still relatively safe, is the anticoagulant drug warfarin. Less than 1/500th of an ounce is enough to make an adult rat die of internal bleeding. Ironically, the brown rats' white kin in laboratories helped University of Wisconsin researchers develop warfarin anticoagulants as lifesavers for men and killers for rats.

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