House Fly

Disease Transmission

The housefly is well adapted by structure and behaviour to transmit disease-causing organisms. Fine hairs and bristles that easily pick up particles cover its body. At the base of each leg (the foot) is a cushion like structure that is covered with glandular hairs. The sticky secretions from these glandular hairs gather bacteria and other organisms.

The housefly excretes and regurgitates whenever it comes to rest. Regurgitation is the process of digestion during which food is brought up from the crop and mixed with saliva before being passed onto the digestive tract.

Housefly larvae breed in accumulations of waste, rubbish and manure. Adult flies, which often use buildings for shelter, feed on human and animal food and waste material. They also land on the exposed skin of people and animals.

While houseflies are not necessary for the transmission of several important diseases and are only rarely the most important vector, the housefly is one means of transmission of the following intestinal diseases:

Shigellosis. Bacillary dysentery and other diarrheal diseases.

Salmonellosis. Typhoid, paratyphoid, enteritis, food poisoning. Flies play a role in inoculating food with Salmonellosis type microorganisms but are generally less important in the transmission of this group when compared to shigellosis.

Cholera. Transmission by flies is possible but probably rare.

Amoebic dysentery. Flies can transmit the cysts.

Parasitic worms. Flies can carry the eggs and cysts of many intestinal worms including pinworm, roundworms, whipworms, hookworms and tapeworms.

Polio. Flies are able to transmit viruses such as poliomyelitis and related viruses to human food in sufficient quantities to cause infection in some people.

Eye Diseases. Eye diseases such as Trachoma (viral) and epidemic conjunctivitis (bacterial) can be spread by houseflies.

Control

Minimising exposed rubbish and pet excrement should limit fly breeding habitats. Cleanliness overall is an important part of controlling houseflies. Adult flies can be excluded from structures by proper building design and the use of screening on doors and windows.