Stoy Hedges, an entomologist and Director of Technical Services at Terminix International, says, "There has been some research with cockroaches. There are probably more than 50 disease causing organisms that have been isolated from cockroach bodies. Although there is no scientific study that has shown there has been direct transmission of these diseases to people, there is always that risk. So that's one of the primary reasons that health officials don't want cockroaches in restaurants. They don't want cockroaches in hospitals because they have diseased organisms. They also have a potential for mechanical transmission. You don't want them crawling or crossing something, and then, they leave their bacteria behind."
Dr. Xing Ping Hu, an assistant professor of entomology at Auburn University spoke to the possibilities of cockroaches spreading disease in an online article on the Alabama Cooperative Extension System website at http://www.aces.edu/dept/extcomm/newspaper/may2c03.html, "What we do know is that cockroaches are known carriers of many different diseases. That includes 32 bacterial and 17 fungal-related diseases, three protozoa- related illnesses and two viruses."
How do cockroaches possibly infect humans with diseases and illnesses? In the same article on the Alabama Extension System website, Dr. Art Appel, alumni professor of entomology at Auburn University explains. "Cockroaches 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 that eats it."
Both Appel and Hu point out plenty of anecdotal or circumstantial evidence to implicate cockroaches in widespread outbreaks of illness and disease, but no hard data. They refer to cases in which illnesses broke out in crowded apartment buildings, where cockroaches and people were living together in great numbers. It's not backed up by scientific studies but as Hu remarks, "When the cockroach populations went down, diseases began to disappear. And that's a very strong indicator that cockroaches may serve as a vector of diseases."
However, not everyone sees cockroaches as a great danger. According to the website for the Woodland Park Zoo in Seattle, Washington (http://www.zoo.org/educate/fact_sheets/roach/roach.htm), "For humans, cockroaches pose little threat; practically all species of cockroaches are beneficial to their environment, and they are an invaluable aid in recycling a large majority of the Earth's dead or decaying plant and animal matter. Many people associate cockroaches with the spread of disease. Unlike mosquitoes or fleas, cockroaches do not spread disease via direct transmission (i.e. through the blood as the result of a bite). Instead, cockroaches inhabit unsanitary areas of food storage, bringing with them microbacterial agents of decay. In turn, these agents contaminate our food supplies with pathogenic organisms. It is these "hitchhikers" that spread disease, not cockroaches."
So while cockroaches may not directly infect humans with illnesses or disease, they are drawn to unsanitary areas where disease lurks. Keeping areas clean of dark, dirty food sources for the insects will go a long way to protecting humans from any diseases.
