Guest Commentary: What diseases do rats carry?

Posted by Big Rat on Campus on Aug 4, 2017 in Rat News | Subscribe

There have been many reports in The Westerly Sun in recent days about rats. There is much public and private concern about some obvious infestations. Nevertheless, we should remember that rats are present less apparently elsewhere in our communities on both sides of the river.

Most of us are familiar with the history of the Black Death, an epidemic of plague caused by the bacterium Yersinia pestis that led to the death of millions of people during the 14th century. Rats have a long history, are not native to North America and traveled in ships to settle here with us. New York City has budgeted $32 million to combat its rat problem. Rat infestations have made the news in Rhode Island in 2016 and 2017 in North Providence, Warwick and Providence.

About 15 or 20 years ago a friend gave me as a birthday present a beautiful handmade wooden bird feeder for my office on East Avenue. I put up the feeder outside and added some seeds. The next morning when I came in early to the office I looked out the window to see if there were any birds present. No birds were to be seen, but there were two brown rats at the bird seed already! There must have been a nest of rats somewhere in the neighborhood that had not been noticed. Needless to say, I removed the feeder immediately. On one occasion I saw a rat running in front of my headlights in Dixon Square before dawn after an all-nighter in the hospital. Rats become more apparent from time to time and then are the subject of public anxiety and subsequent extermination campaigns, which are often quite effective. They are always around waiting for an opportunity and I will describe some of the diseases that they are known to carry.

Leptospirosis is an acute disease characterized by fever, muscle aches and headache, and can be initially confused with other febrile illnesses. It is caused by Leptospira bacteria that chronically colonize rats’ kidneys; rat urine wet or dry is then infectious for long periods of time. The most important source of human infection is the brown rat. These bacteria, contaminating surfaces or soil or water wherever rats have been, can infect us through contact with eye, oral surfaces, cuts or abrasions. Lack of sanitation in housing increases the risk of exposure. The incidence of Leptospirosis appears to increase after storms or floods as well. When managing patients, clinical suspicion is important; there are diagnostic blood tests, but prevention is best. Leptospirosis is a quite rare disease in the United States and we should keep it that way. It was described about a hundred years ago and research has yielded new information about leptosperes and the disease is now known to be an increasing problem in the world.

Rats’ droppings are known to be a source of contamination of food or water with Salmonella bacteria. Symptoms start one to three days after oral ingestion. The patient suffers diarrhea, fever and severe crampy abdominal pain. Patients with this disease are seen from time to time by local physicians.

Rat bite fever is caused by a germ with the imposing name Streptobacillus moniliformis and is characterized by intermittent fevers, rash, migratory arthritis and a 10 percent mortality rate when untreated. Traditionally the typical case was that of a child under the age of 5 living in poverty and bitten by a wild rat. Rats that carry the disease often do not appear to be sick. Not all of the cases have had a specific history of bite but have been exposed in other ways — for example by a scratch from an infected animal. Pet rats have also been reported as a source of this disease. Rat bite fever is also uncommon and requires careful diagnostic efforts.

Rats are the source and fleas are the transmission agent for the small bacteria that cause murine typhus. This disease is mostly seen in southern Texas and southern California. There are other rat-borne illnesses such as rat tapeworm but these are usually not seen in the United States. The website of the Centers for Disease Control and Prevention indicates that rats cause 35 different diseases worldwide. The plague mentioned previously exists currently in the United States. There have been 7 to 17 cases reported annually in recent years. It occurs usually in the Southwest, and chipmunks and squirrels are involved as well as rats.

Rhode Island state law 23-7.1 states that it shall be the responsibility of local communities to institute rodent control programs and requires the state Department of Health to cooperate with local communities in developing and carrying out such programs. Section 23-7.1-5 allows the director of public health to contribute to local communities for comprehensive rodent control programs. These documents can be found on the internet. I believe that it is a good idea to be proactive when it comes to rats.

Tobias Goodman, M.D., is a retired Westerly physician and the former health coordinator for the Town of Westerly.

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