Possible Link Between Cockroaches and SARS Good Enough Reason to Treat the Home

Auburn, May 2, 2003 --- Is it possible cockroaches are spreading the potentially deadly SARS virus?

Scientists aren’t sure. But whatever is ultimately decided, one expert says it is still a good idea to keep living spaces free of cockroaches.

(Photo Courtesy of the University of Rhode Island Landscape Horticulture Program.)

“What we do know is that cockroaches are known carriers of many different diseases,” says Dr. Xing Ping Hu, an Alabama Cooperative Extension System entomologist and Auburn University assistant professor of entomology. “That includes 32 bacterial- and 17 fungal-related diseases, three protozoa-related illnesses and two viruses.”

Most health experts adamantly maintain there is no clear evidence linking cockroaches to SARS. The most likely culprits, they believe, are people who spread the disease through sneezing and coughing and touching doorknobs, elevator buttons and telephones.

Nevertheless, a huge outbreak of the disease that occurred in a large, crowded Hong Kong apartment complex where tenants share the same sewage system left many experts speculating whether roaches were the culprit.

“It’s one of those things that are within the realm of possibility,” says Dr. Art Appel, Auburn University alumni professor of entomology.

“Like the common cold, the disease is most likely spread through sneezing and other aerial secretions or by handshaking, but the link to cockroaches is not entirely outrageous.”

Cockroaches, Appel says, are believed to be “mechanical vectors” of some disease organisms.

“What this means is that they can carry disease from one place to another. For example, if they come up from the sewer and walk across a slice of bread, it’s possible that whatever pathogen that is on the cockroach can be transferred to the bread and ultimately to the person who eats it.”

Curiously, a clear link between cockroaches and disease has never been established, though history abounds with circumstantial evidence. And in cases where cockroaches are linked with major disease outbreaks, the conditions are always the same: large numbers of humans and cockroaches sharing the same confined living space.

One of the most serious outbreaks associated with roaches occurred between 1956 and 1962 in a crowded Southern California apartment complex where cockroach populations were exceptionally high, Hu says.

Twenty years later, halfway across the world, a dysentery outbreak in Northern Ireland was linked with the very same factors – large numbers of people sharing cramped living spaces with large cockroach populations.

In both cases, the illnesses began dropping off when cockroach populations declined. Circumstantial evidence? Yes. But the correlation between the two simply cannot be ignored.

“When the cockroach populations went down, diseases began to disappear,” Hu observes. “And that’s a very strong indicator that cockroaches may serve as a vector of diseases.”

Recently, the most baffling outbreak of SARS occurred in a sprawling, aging apartment complex in Hong Kong – baffling because the disease apparently was not spread by a single person as had previously been the case with other outbreaks.

Some scientists have speculated that the outbreak may stem from a large population of cockroaches that were foraging around the apartment complex’s common sewage system. Even so, testing of the cockroaches has turned up no evidence that the roaches are carriers of the virus.

Even if cockroaches are not found to be SARS carriers, the circumstantial evidence that already has been uncovered is reason enough for people to spare no effort reducing cockroach populations throughout personal living spaces, Hu says.

Fortunately for consumers, a wide array of cockroach-related products released within the last few years is making that job much easier.

“Only a decade ago, cockroaches were considered the No. 1 household pest,” Hu says. “But in the last three years, new technologies and products, especially baits, have been made available that work really well with cockroaches.

“They not only do a good job targeting the roaches but also provide excellent residual control in many cases.”

Along with using chemical control methods, Hu also says it’s wise to adopt a non-chemical approach to insect control known as integrated pest management. For homeowners, this involves identifying sources of food and habitat around the home that may harbor cockroaches.

The two most important points to remember, she says, are “mulch and moisture.” Mulch located close to the home provides an excellent hiding place for cockroaches and a launching pad into the interior of the home. Water or sprinkling systems also provide the roaches with a source of water.

“Eliminate these two sources,” Hu says, “and there’s no place around the home for the roaches to hide.”

(Sources:  Dr. Xing Ping Hu, Extension Entomologist and Auburn University Assistant Professor of Entomology, 334-844-6392; and Dr. Art Appel, Alumni Professor of Entomology and Alabama Agricultural Experiment Station Researcher.)

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