Basic 7 · Science · Life Cycles of Organisms
The Housefly as a Menace and Its Control
In this topic you will discuss why the housefly is a menace to humans, explain how it spreads diseases, and describe ways of reducing its harmful effects.
By the end of these notes you should be able to:
- Explain why the housefly is considered a menace
- Describe how houseflies spread diseases
- Describe measures to control houseflies and prevent disease
What you already know
- The life cycle of the housefly
Copy everything that has a blue line on its left into your notebook. The other parts are for reading.
Lesson 1
- Strand
- Cycles
- Sub-strand
- Life Cycles of Organisms
- Indicator
- B7.2.2.1.2 – Discuss the activities of the housefly as a menace to humans and show how to reduce the effects of those activities
Introduction
A single fly landing on your food may seem harmless, but it may have just come from a toilet or a refuse heap. Houseflies are one of the most dangerous insects in our homes.
1. Meaning of Menace
Menace: Something that causes harm, danger or nuisance.
2. Diseases Spread by Houseflies
| Disease | Main signs |
|---|---|
| cholera | severe watery diarrhoea and vomiting; can kill quickly |
| typhoid fever | high fever, headache, stomach pain |
| dysentery | diarrhoea with blood and mucus |
| diarrhoea | frequent loose stools, causing dehydration |
| trachoma | eye infection that can cause blindness |
| worm infections | eggs of intestinal worms carried to food |
3. Other Nuisances
Besides spreading disease, houseflies disturb people while eating and sleeping, spoil food, stain walls and furniture with their droppings, and annoy livestock, reducing milk and meat production. In markets, flies on meat and fish discourage buyers and reduce traders' income.
4. Who Is Most at Risk?
Young children, the elderly and people living near refuse dumps or open latrines are most at risk. Diarrhoea caused partly by flies is a major cause of illness among children under five in Ghana. Cholera outbreaks in crowded areas of cities such as Accra have often been linked to poor sanitation and flies.
5. The Cost of Fly-Borne Diseases
Fly-borne diseases cost families and the nation a lot of money. Sick learners miss school, and sick workers cannot earn. Families spend money on hospital bills and medicine, and the government spends heavily on treating cholera and diarrhoea outbreaks. Preventing these diseases through cleanliness is far cheaper than curing them.
New words
- menace
- Something that causes harm or danger.
- cholera
- A serious disease causing severe watery diarrhoea.
- dehydration
- Loss of too much water from the body.
- trachoma
- An eye infection that can cause blindness.
Summary
- The housefly is a menace because it spreads diseases such as cholera, typhoid and dysentery.
- It also spoils food, annoys people and livestock, and stains surfaces.
- Children and people living near poor sanitation are most at risk.
Class activity: Fly Danger Poster
- List diseases spread by houseflies and their signs.
- Make a poster warning your community about the danger of flies.
- Display it in the school.
You need: Sealed housefly specimen, Printed housefly life-cycle diagram, Covered food container
Exercises
Answer in your exercise book first, then check your answers.
1. Which disease is spread by houseflies?
- A. cholera
- B. malaria
- C. measles
- D. asthma
Show answer
Answer: choleraFood contamination.2. Trachoma affects the…
- A. eyes
- B. lungs
- C. heart
- D. bones
Show answer
Answer: eyesEye infection.3. Houseflies can spoil food.
- A. True
- B. False
Show answer
Answer: TrueThey contaminate it.4. Loss of too much water from the body is ______.
Show answer
Answer: dehydrationFrom diarrhoea.5. Name three diseases spread by houseflies.
Show answer
Answer: Cholera, typhoid, dysentery (or diarrhoea, trachoma).Any three.6. Why are children under five most at risk from fly-borne diarrhoea?
Show answer
Answer: Their bodies dehydrate quickly and their immunity is weaker.Vulnerability.
Lesson 2
- Strand
- Cycles
- Sub-strand
- Life Cycles of Organisms
- Indicator
- B7.2.2.1.2 – Discuss the activities of the housefly as a menace to humans and show how to reduce the effects of those activities
Introduction
Houseflies do not bite to spread disease like mosquitoes. Instead, they carry germs on their bodies and in their mouths from dirty places to our food.
1. Mechanical Transmission
Houseflies spread disease by mechanical transmission: they pick up germs on their bodies and carry them from place to place. A fly that lands on faeces or rotting refuse picks up bacteria, viruses and worm eggs.
2. How the Germs Reach Us
| Way | How it happens |
|---|---|
| hairy legs and body | germs stick to the hairs and are dropped on food |
| sticky foot pads | germs stick to the pads and are left on surfaces |
| vomiting on food | the fly vomits digestive juices, which may contain germs, onto food |
| droppings | flies defecate frequently on food and surfaces |
3. The Chain of Infection
Trace the chain
Show how cholera can spread from an open latrine to a family.
- A sick person's faeces in an open latrine contain cholera germs.
- A housefly lands on the faeces and picks up germs on its legs and mouth.
- The fly flies into a kitchen and lands on uncovered rice.
- It vomits and leaves droppings on the rice.
- The family eats the rice and becomes infected.
Answer: Open latrine → fly → uncovered food → family; breaking any link stops the spread.
4. Breaking the Chain
The chain can be broken at many points: using covered, clean toilets so flies cannot reach faeces; disposing of refuse properly so flies cannot breed; covering food so flies cannot land on it; and washing hands and fruits before eating.
New words
- mechanical transmission
- Spreading germs by carrying them on the body.
- germs
- Tiny organisms that cause disease.
- contaminate
- To make something dirty or harmful.
- chain of infection
- The steps by which disease spreads.
Summary
- Houseflies spread germs mechanically on their hairy legs, sticky pads, vomit and droppings.
- Germs travel from faeces and refuse to food.
- Breaking the chain at any point prevents disease.
Class activity: Chain of Infection Drama
- Act out how a fly carries germs from a refuse dump to food.
- Show how covering food or using a clean toilet breaks the chain.
- Explain your drama to the class.
You need: Sealed housefly specimen, Printed housefly life-cycle diagram, Covered food container
Exercises
Answer in your exercise book first, then check your answers.
1. Houseflies carry germs mainly on their…
- A. hairy legs and body
- B. teeth
- C. stings
- D. feathers
Show answer
Answer: hairy legs and bodyMechanical transmission.2. Which action breaks the chain of infection?
- A. covering food
- B. leaving food open
- C. open defecation
- D. dumping refuse anywhere
Show answer
Answer: covering foodPrevention.3. Houseflies spread disease by biting.
- A. True
- B. False
Show answer
Answer: FalseThey carry germs mechanically.4. To make something dirty or harmful is to ______ it.
Show answer
Answer: contaminateSpoil.5. State three ways houseflies transfer germs to food.
Show answer
Answer: On their legs and hairs, by vomiting on food, through droppings.Any three.6. Explain how cholera can spread from an open latrine to a family.
Show answer
Answer: Flies pick up germs from faeces, land on uncovered food and leave germs, and the family eats it.Chain.
Lesson 3
- Strand
- Cycles
- Sub-strand
- Life Cycles of Organisms
- Indicator
- B7.2.2.1.2 – Discuss the activities of the housefly as a menace to humans and show how to reduce the effects of those activities
Introduction
We cannot remove every fly from the world, but we can greatly reduce their numbers and protect our health through good hygiene and sanitation.
1. Destroying Breeding Places
- Dispose of refuse in covered bins and empty them regularly.
- Bury or compost kitchen waste properly.
- Use covered, clean toilets; avoid open defecation.
- Remove animal dung regularly from pens.
- Keep gutters and surroundings clean.
2. Protecting Food and People
| Measure | How it helps |
|---|---|
| cover food and water | flies cannot land on them |
| wash fruits and vegetables | removes germs |
| wash hands with soap | removes germs before eating |
| fit nets on windows and doors | keeps flies out of houses |
| keep kitchens clean | removes food that attracts flies |
3. Killing Flies
Flies can be killed with fly swatters, sticky fly traps and safe insecticide sprays. Insecticides must be used carefully according to instructions, kept away from food and children, and not overused because flies can become resistant. Some farms use natural methods, such as introducing tiny wasps that attack fly pupae.
4. Community Action
Control works best when the whole community acts. National Sanitation Day clean-ups, school health clubs, environmental health officers who inspect markets and food vendors, and public education on radio all help reduce flies and the diseases they spread.
5. Traditional and Simple Methods
Some homes use folk methods, such as hanging clear bags of water near doorways, burning dried orange peel or neem leaves, or growing basil and lemongrass near the kitchen. There is little scientific evidence that these work well, so the most reliable methods remain cleanliness, covering food and removing breeding places. Learners can test a folk method in a fair experiment to see whether it really works.
New words
- sanitation
- Keeping the environment clean and disposing of waste safely.
- insecticide
- A chemical that kills insects.
- fly trap
- A device that catches flies.
- resistant
- No longer killed by a chemical.
Summary
- Destroy breeding places by proper refuse and toilet management.
- Protect food and people by covering food, washing hands and using nets.
- Kill flies safely and act as a community to keep the environment clean.
Class activity: School Fly Control Plan
- Survey the school for fly breeding places.
- Write a plan to remove them and protect food.
- Present the plan to the school health club.
You need: Sealed housefly specimen, Printed housefly life-cycle diagram, Covered food container
Exercises
Answer in your exercise book first, then check your answers.
1. Which is a good way to protect food from flies?
- A. covering it
- B. leaving it open
- C. putting it near refuse
- D. spraying it with insecticide
Show answer
Answer: covering itPrevention.2. Removing animal dung from pens helps because dung is a…
- A. breeding place for flies
- B. food for people
- C. fertiliser only
- D. type of insecticide
Show answer
Answer: breeding place for fliesBreeding site.3. Insecticides should be kept away from food and children.
- A. True
- B. False
Show answer
Answer: TrueSafety.4. Keeping the environment clean and disposing of waste safely is ______.
Show answer
Answer: sanitationHygiene.5. State four ways of controlling houseflies.
Show answer
Answer: Covered bins, clean toilets, covering food, using nets (or fly traps, swatters).Any four.6. Why should insecticides not be overused?
Show answer
Answer: Flies can become resistant, and the chemicals can harm people and the environment.Resistance and safety.
Homework
- Inspect your home for fly breeding places and write how to remove them.