Cockroaches are persistent and troublesome pests of homes, restaurants, hospitals, warehouses, offices, and other structures with food handling areas. These insects contaminate food and utensils, destroy fabric and paper products, and impart stain and odor to surfaces they contact.
The medical importance of cockroaches is much greater than generally realized as they have been shown to carry diverse pathogenic and non-pathogenic bacterial flora, different protozoa, pathogenic helminths, fungi, and viruses. Like any biting or walking insects, such as bedbugs cockroaches can be very good transporters and thus can participate in spreading molds. It was reported that 98% of cockroaches found in medical facilities could carry pathogens on their integuments or digestive tracts. The mite (Pimeliaphilus cunliffei) is a parasite of cockroaches. It feeds on live individuals and has been linked to bites of humans living in households with cockroach infestations.6,7,9
Cockroaches are universally loathed. One of the primary reasons is because they are associated with any place where there are biological waste products such as sewers, septic tanks, garbage cans, chicken houses, and animal cages. Their attraction to human and animal feces, rotting food, secretions from corpses, sputum, pus, and the like gives them a well-earned "disgust factor" among the general public. All these moist, organic habitats contain staggering amounts of bacteria, protozoa, amoebae, fungi, and other microbial material.3
Photo attribution: Daniel R. Suiter, University of Georgia, Bugwood.org
Photo attribution: Gary Alpert, Harvard University
Cockroaches belong to the insect order Dictyoptera. Young and immature cockroaches resemble adults, that is, they undergo gradual metamorphosis. Adults of male species have wings, although many species do not fly. Although there are 70 described species of cockroaches in the United States, and over 4,000 worldwide, only a few are major pests. However, although the vast majority of cockroaches are presumed to be medically harmless, it is well to keep in mind that, should any of these change their habits and become followers of man, they too may become as potentially
dangerous as the known domiciliary species. Occasionally species that usually occur outdoors invade buildings. Domiciliary cockroaches include approximately 25 species from the families Blattellidae, Blattidae and Blaberidae. Two species, German cockroach (Blattella germanica) and American cockroach (Periplaneta americana) predominate in temperate and tropical areas, respectively, and have been the focus of allergy research.
Microbes are an essential influence in the nutrition, ecology, and evolution of all cockroaches. The main source of nourishment for cockroaches in mines and sewers, for example, is human feces, which can be 80% bacterial. German cockroaches have been observed feeding on mouth secretions of corpses riddled with lung disease; these secretions were almost 100% infectious bacteria.3
The makeup of the microbial population of the American cockroach gut, long the subject of numerous investigations, has been shown to include a variety of microorganisms, bacteria, protozoa, and nematodes. Cockroaches, especially species that come in contact with feces like German cockroaches may transmit bacteria responsible for food poisoning. Cockroaches act as mechanical vector in transmitting Salmonella, Shigella, and Cryptosporidium parvum bacteria that cause diarrheal diseases. Antibiotic resistant strain of Klebsiella pneumoniae bacteria that cause pneumonia has been found in patients and cockroaches in hospitals. In addition, evidence suggests that cockroaches spread typhoid, disentery, and leprosy organisms.2
Bacteria Carried By Cockroaches
At least 32 species of bacteria have been isolated from cockroaches in domestic environments. A total of 174 bacterial isolates were isolated from 39 German cockroach specimens in hospital environment.9 These may include:
- Aeromonas species cause wound and other infections, diarrhea.
- Alcaligenes faecalis causes of gastroenteritis, urinary tract infections.
- Bacillus cerreus causes food poisoning.
- Bacillus subtilis causes conjunctivitis.
- Campylobacter jejuni causes enteritis.
- Clostridium perfringens causes food poisoning, gas gangrene.
- Enterobacter species cause bacteremia (temporary presence of bacteria in the blood, which is commonly followed by the development of various infections including abscesses).
- Enterococcus species cause urinary tract and wound infections. Cockroaches in the confined swine production environment may act as vectors and/or reservoirs of antibiotic resistant enterococci.
- Escherichia coli causes diarrhea, wound infections.
- Helicobacter hepaticus, animal and human pathogen associated with inflammation of gallbladder (cholecystitis), gallbladder stones and gallbladder cancer.14,15
- Klebsiella species cause pneumonia and urinary tract infections.
- Mycobacterium leprae causes leprosy.
- Morganella morganii causes wound infections.
- Nocardia species cause actinomycetoma (chronic infection of the skin and underlying tissues).
- Oligella urethralis, may cause bacteremia, septic arthritis that mimics gonococcal arthritis, and peritonitis.4
- Pantoea species cause wound infections.
- Proteus rettgeri causes wound infections.
- Proteus vulgaris causes wound infections.
- Proteus mirabilis causes wound infections, gastroenteritis.
- Pseudomonas species cause respiratory infections, gastroenteritis.
- Salmonella cause gastroenteritis, food poisoning
- Salmonella typhi causes typhoid.
- Salmonella pyogenes causes pneumonia.
- Serratia species cause food poisoning.
- Shigella dysenteriae causes disentery.
- Sphyngobacterium species cause sepsis (presence in the blood or other tissues of pathogenic microorganisms or their toxins).
- Staphylococcus aureus causes wound infections, skin infections, infections of internal organ.
- Staphylococcus epidermalis causes wound infections.
- Streptococcus faecalis and other species cause pneumonia.
- Chlamydia trachomatis causes trachoma, infectious eye disease, the leading cause of the world's infectious blindness. Globally, 41 million people suffer from active infection, and nearly 8 million people are visually impaired as a result of this disease.
- Yersinia pestis (isolated from oriental cockroach), causes plague.
Worms, Protozoa, Fungi, and Viruses Carried By Cockroaches
Cockroaches also have been found harboring eggs of seven species of helminths (hookworm, giant human roundworm, pinworm, tapeworm, and whipworm). The helminths harbored by cockroaches include Ascaris lumbricoides (giant roundworm of humans), Trichuris trichiura (human whipworm), Taenia species (tapeworms), and Strongyloides-like parasites (roundworms).8. Cockroaches harbor at least 17 fungal species, three protozoan species, and two strains of polymyelitis virus. Australian, American, and Madeira cockroaches become infected with the protozoan Toxoplasma gondii, the causative agent of toxoplasmosis, after feeding on feces of infected cats. This suggests the possibility of cockroach involvement in the maintenance and dissemination of this parasite, which infects humans and other animals.5 Human diseases associated with Toxoplasmosis
Cockroaches repeatedly have been recognized as a common source of indoor allergens. In the United States 63% homes have detectable levels of cockroach allergens. Low-income households and older homes are also among the factors frequently associated with U.S. residences having high concentrations of mouse and cockroach allergens. In some communities, more than 40% of the middle-class suburban population lives in homes with elevated levels of cockroach allergens.13 They flourish where sufficient food, moisture, and warmth are available (kitchens, bathrooms, and similar areas), and they can survive low humidity better than dust mites and, unlike mites, search actively for the water they need to survive. Allergenic proteins from cockroaches and mites are associated with particles that are 5 microns (μm) or greater and become airborne only when settled dust is disturbed.
Cockroach allergy is an important health problem associated with the development of asthma, as a consequence of chronic exposure to low levels of allergens in susceptible individuals. At least eleven proteins isolated from German and American cockroaches can cause allergic reactions and contribute to asthma in humans. The allergens are heat-stable and persistent in the environment even after the insect death. Cockroach allergen sensitization is one of the greatest risk factors for increased asthma-related poor health among the low-income population in the United States (referred to as the inner-city asthma problem in the US).10
Cockroaches can be found in aircraft, especially aircraft that spend time on the ground in tropical environments. Dust mites and cockroaches are the only arthropods that might habitually infest aircraft and possibly become sources of allergens in the cabin environment.