He says they are more likely to pick up germs from us than the other way around. Every time we cough or touch anything, we leave behind viruses and bacteria. If a roach crosses our path, it collects our germs.
But because roaches aren't skilled fliers, they tend to limit their travels to a fairly small area. "In that sense, you are more likely to bring a disease into your home," said Dr. Kunkel. "You travel by boat, car and plane from all over the world, bringing the diseases you collected back with you.''
In theory, a roach could pick up your germs and spread them in your home and nearby areas. But humans are more likely to catch something from another human than a roach. "In this way the cockroach is not a major vector of disease, in a public health sense,'' he said. "The mosquito and house fly are still the champions.''
Dr. Kunkel once encountered a roach at a restaurant, and his four-year-old son blurted "Daddy, there is a Blatella germanica!'' The other diners didn't make the connection, he recalled, and he finished his meal.
All this doesn't mean we shouldn't try to eradicate roach infestations. Cockroaches pose a bigger risk for transmitting disease in close quarters like dorms, hospitals and barracks. In urban areas, cockroach infestations have been linked to asthma, points out Tara Parker-Pope, a New York Times columnist.
The main risk is that a cockroach crawling over food or kitchen surfaces may defecate, and the bacteria left behind will cause food to spoil.
When asked what is the best, non-toxic way to kill cockroaches, Dr.Kunkel responds, saying, "I often tell people that I am not interested in killing cockroaches but rather learning about their life style and physiology. I realize however that most people are more interested in killing them since they are pests in their houses and can contribute to spreading disease in hospitals and childhood asthma in the home.
Beware of most commercial preparations, even those that depend upon the 'natural' insect juvenile hormone. Since these are relatively slow acting, the manufacturers often add a 'knock-down' additive poison which gratifies the user since it provides visual proof that the treatment works when it comes in direct contact with the pest. Read the label of whatever poison you use.
I have come across several methods of killing cockroaches that are non-toxic to humans:
(1) Boric Acid. The crystals of boric acid are sharp and get between the joints of an insect's exoskeleton. The sharp crystals abrade the cuticle and make the cockroach lose water and die of dehydration. This is a simple and cheap method. Dust the boric acid (which is relatively non-toxic) around the corners of rooms and in hiding places frequented by the roaches. A more expensive industrial version of this method is called Permadust. It is finely ground ruby dust which performs the same function as boric acid crystals but is more permanent. Boric acid washes away when you want to get rid of it.
You will find the dried carcasses of cockroaches in various hiding places as well as out in the open where they marched their last step searching for water.
(2) Live Traps. Take a bowl or wide mouth bottle with steep sides; lightly Vaseline the inside wall up to the lip so that a cockroach can not climb up the slippery surface; place the bowl in a typical hiding place such as under your kitchen sink; place some food (bread, carrots, etc.) in the bowl as well as some toweling dampened with water; build some ramps up to the lip on the outside with paper toweling to encourage the cockroaches to easily enter the bowl. This trap will quickly overnight accumulate a good sample of your household cockroach population. Flush them down the toilet each morning for sanitary disposal. Soon the cockroach population will be quite low and perhaps undetectable by you.
This later method would also provide your pet rat a non-toxic feeding station and your son a place to learn about the local fauna. I would not be suprised if the pet rat ate some of the captives which are good sources of protein and vitamins.
Dr. Kunkel has compiled a list of frequently asked questions about roaches.