Cockroaches as well as other insects have come under suspicion as possible vectors of Mycobacterium leprae, causative agent of Hansen's disease or leprosy. The evidence for insect vectors in the transmission of leprosy is based on analogy, because leprosy is the poor man's disease and the vector should be an insect that is important in the homes of unhygienically living people. Mycobacterium leprae passes unharmed through the intestine of the cockroach and the German cockroach may excrete the bacterium in the feces 14 days after feeding on leprous nodules. These bacilli were recovered in large numbers from the guts (up to the nineteenth day after feeding) and from dried feces of the insects. The bacilli remained unchanged in dried feces for several months.
The bites or the feces of infected cockroaches are the real source of infection in leprosy. Contaminated cockroach feces may be rubbed or scratched into the skin. As mechanical vectors of leprosy, cockroaches could conceivably transport Mycobacterium leprae on their legs from leprous individuals to existing lesions in the skin of sleeping humans without either biting man or excreting the organism in the feces. There are many references to cockroaches climbing over the bodies and faces of sleeping children and adults.
Leprosy is not highly contagious and is acquired by infecting superficial abrasions of the skin. Although transmission is presumed to be from person to person, indirect transmission has not been disproved; in fact, in some cases leprosy developed after an injection of leprous blood, and two cases in which leprosy began in tattooed areas about three years after the tattooing.
The information above has been compiled from a source based on clinical data and research back in 1950s and may seem rather old. There are two main reasons for publishing this information: 1) A strong link between pathogenic organisms and the devlopment of cancer and many other debilitating diseases; 2) The need to increase public awareness of the health risks associated with pathogenic organisms spread by cockroaches.
- The medical and veterinary importance of cockroaches. Smithsonian miscellaneous collections (biodiversitylibrary.org)