Houseflies are a very common nuisance to human habitations across the globe. These flies are typically found around food sources and have become a part of human lives in many parts of the world. Apart from being a source of general irritation, houseflies are also carriers of various diseases. Many of the common human infections can be spread around by houseflies. Some of these diseasess can be very serious and potentially fatal. Therefore, limiting house flies from making contact with food and reducing housefly populations are integral steps in maintaining general hygiene.
The Life Cycle of Flies
A female housefly prefers to lay eggs on organic decaying materials such as manure or garbage. A single adult female housefly can lay up to 200 eggs at a time. Within a few hours, maggots or larvae hatch out of the eggs and burrow into the surrounding organic material. After reaching a suitable location, the maggots transform into pupae that have a protective covering known as the capsule. Within this capsule, a maggot develops into an adult fly within 2-10 days. The adult fly that emerges out of the pupa is able to reproduce again within a few days.
The adult housefly lives for about 2-3 weeks on an average. However, the life span of housefly depends a great deal on the ambient temperature. Depending on the ambient temperature, the developmental life cycle of a housefly may range from a week to 42 days. In a cold environment, a fly may be able to survive up to 3 months. An adult female housefly is capable of laying eggs up to five times in its entire lifespan. Although people typically find maggots more repulsive than adult flies, it is the adult fly that is the major carrier of diseases.
Types of Housefly Diseases
The housefly is a carrier of many infectious diseases. The infectious diseases spread by houseflies are caused by over a hundred different pathogens such as protozoa, bacteria, viruses and nematodes. Interestingly, the housefly does not play a critical role in the lifecycle of any of these pathogens. It is merely one of the many carriers of these pathogens. Viewed in this way, houseflies are indiscriminate carriers of multiple infectious diseases.
Therefore, controlling housefly populations can help in preventing the spread of multiple infectious diseases.The most common group of infectious diseases that are spread by houseflies are the diarrheal illnesses. These infectious diarrheal diseases are mostly caused by bacteria such as Enterococci, Campylobacter, Shigella and E.coli. Flies pick up these bacteria from the feces of infected individuals and transmit them to other people when they sit of food items.
Some of the common infectious diseases spread by houseflies include cholera, anthrax, dysentery, diphtheria, conjunctivitis, polio, gastroenteritis, typhoid fever, trachoma, yaws, leprosy and tuberculosis.
Read more on typhoid fever.
Spread of Diseases through Houseflies
Unlike other insect vectors such as mosquitoes, tsetse fly and horsefly, a housefly does not bite and inject pathogens into the bloodstream. Instead, it uses different non-invasive routes to spread the pathogens. For example, when a housefly sits on decaying organic matter such as garbage, rotting food and feces, the pathogens present in such substances cling to various parts of the body of the housefly.
When the housefly lands on food items that will be consumed by a healthy person, it inadvertently transmits the pathogens stuck on its body or present in its feces or vomitus. The pathogens tend to grow in such food, especially in food that is not refrigerated. Therefore, consumption of foods that have come in contact with houseflies is potentially harmful. The dose of pathogen that can cause disease in a human varies with the type of pathogen. In some cases, only a few pathogens are enough to cause serious illness.
Preventing Transmission of Fly Diseases
The most effective way to prevent transmission of diseases by houseflies is to control the population of houseflies around human dwellings. One does not need to spray strong insecticides in order to control the spread of diseases by flies.Some strategies outlined by the World Health Organization that can help in preventing the spread of infectious diseases by houseflies are as follows.
Reduction or elimination of breeding sites
Breeding sites for flies are not a major problem in most urban areas in developed countries. However, it is an ongoing problem in most rural areas and in developing countries. This is especially a problem in places where livestock are kept. Animal dung is a major attractant for flies. In cities, feces of pets and inadequate garbage disposal may pose a similar risk. Use of insecticides, regular cleaning of carpets inside homes that have pets, and proper and regular garbage disposal can help in reducing or eliminating breeding grounds for flies.
Preventing contact between pathogens and flies
Pathogens can stick to a fly’s body within a few seconds of contact. Therefore, it is imperative to prevent all contact of houseflies with sources of pathogens such as feces. In developed countries, modern toilet facilities have been successful in reducing contact between pathogens in feces and houseflies. However, soiled baby diapers that are not discarded properly still pose a risk in the developed nations.
Also, excreta from infirm or elderly patients may not get cleaned up promptly. This could be a source of pathogens that may spread by coming in contact with houseflies. Eye infections, sores, and open wounds are other potential places where pathogens may come in contact with houseflies. Slaughterhouses that are not cleaned regularly also attract flies.
Read more on food poisoning.
Preventing contact between food and flies
Preventing contact between houseflies and sources of pathogens is one way of dealing with the spread of infectious diseases. Another way is to prevent houseflies from coming into contact with food. It is very difficult to completely eradicate houseflies. But it is easy to prevent contact between houseflies and food by using nets, screens, self-closing doors and closing utensils that contain food. Fans can be used over doorways to prevent flies from entering the house. Fly traps that attract and kill flies can also be used inside homes.