Interactive Resources for Schools
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Biology
Houseflies are everywhere – and wherever they go, bacteria and viruses go too. The average lifespan of an adult housefly is around one month. During that time they feed and breed on garbage, sewage, rotting food and other sources of filth. They can only take in liquid food, so they vomit up digestive juices onto their food and suck up the liquid which is produced by the digestive enzymes. They suck up lots of bacteria and viruses too. The pathogens which cover their food are carried away on the mouthparts, feet and other body parts of the fly. Then, through their vomit, faeces and contaminated external body parts, the flies transfer bacteria and viruses to human and animal food or directly onto our skin.
The best way to prevent the spread of the many diseases carried by flies is to control the numbers of the vectors themselves. If you can remove the materials that flies need to feed on and to lay their eggs, you will reduce the number of flies and reduce the spread of disease. One of diseases carried by flies is the form of dysentery caused by the Shigella bacteria.
Houseflies spread more diseases than almost any other vector
(Image courtesy of Mike Murray)
Houseflies are everywhere – and wherever they go, bacteria and viruses go too. The average lifespan of an adult housefly is around one month. During that time they feed and breed on garbage, sewage, rotting food and other sources of filth. They can only take in liquid food, so they vomit up digestive juices onto their food and suck up the liquid which is produced by the digestive enzymes. They suck up lots of bacteria and viruses too. The pathogens which cover their food are carried away on the mouthparts, feet and other body parts of the fly. Then, through their vomit, faeces and contaminated external body parts, the flies transfer bacteria and viruses to human and animal food or directly onto our skin.
The best way to prevent the spread of the many diseases carried by flies is to control the numbers of the vectors themselves. If you can remove the materials that flies need to feed on and to lay their eggs, you will reduce the number of flies and reduce the spread of disease. One of diseases carried by flies is the form of dysentery caused by the Shigella bacteria.
Dysentery causes diarrhoea which may be mild and go without problems after a couple of days. However if the infection is severe it causes bloody diarrhoea and very painful stomach cramps. It is transmitted directly from one person to another through poor hygiene – not washing hand after using the toilet. Worldwide it is also widely carried by flies which have access to human faeces.
Like most other diseases causing diarrhoea the biggest problem is dehydration. If it also causes bleeding the patient may become anaemic too. The most important thing is to keep the patient hydrated using rehydration drinks and an intravenous fluid drip if necessary. Antibiotics may be used but only in very severe cases.