There are about 10 species that have exploited the dwellings of humans.

Why are they considered a pest?

Cockroaches may contaminate food products, utensils and various areas with droppings, cast skins, empty egg cases, dead cockroaches, and vomit marks on surfaces.

Annoyance or Fear
Many people are annoyed or scared by the sight of cockroaches. This may be related to their fast, unpredictable movements and perhaps their very spiky legs.

Where a substantial cockroach infestation exists, an unpleasant odour may develop, owing to the secretion from the mouth and cuticle.

Allergic reactions
Some people are allergic to cockroaches. Extracts of cockroaches and bring out positive skin reactions in sensitive people, and may cause asthma attack in asthmatics. The allergen can be ingested where foods are contaminated with faeces, or inhaled when dried faeces becomes a part of house dust.

Cockroaches have been known to bite people, although such instances are rare. In ships where cockroach populations was exceedingly high, sailors have suffered bites and gnawing of the fingernails, toenails, calloused parts and occasionally softer skin.

Disease transmission
Cockroaches carry diseases of humans. Although cockroaches have never been irrefutably proved to have transmitted pathogenic diseases to humans, several factors point to the likelihood that they play an important role in such disease transmission:

  • Cockroaches often dwell in environments that support the growth of organisms causing disease harmful to humans (i.e. sewers, grease traps, other sources of polluted water)
  • The same cockroaches may contact various surfaces (including food) in kitchen and food processing or handling facilities
  • Cockroaches are known to carry, on their cuticle and in their gut and faeces, disease organisms of humans. Each cockroach may typically carry several million bacteria on and inside its body. A variety of disease organisms may be carried including Salmonella, and other organisms causing gastroenteritis, dysentery, tuberculosis, hepatitis, typhoid fever an many other human disorders. Organisms that have been found naturally contaminating cockroaches include:
  • Forty species of bacteria pathogenic to humans
  • The eggs of seven species of worms parasitic to humans
  • A variety of viruses potentially harmful to humans, and
  • Several pathogenic protozoa