Environmental Health Practitioner Manual: A resource manual for Environmental Health Practitioners working with Aboriginal and Torres Strait Islander Communities
3 Common pests
There are many different kinds of pests and only some of these create health problems in Indigenous communities. The control of these will be described in this chapter.
3.1 Living and breeding places of common pestsListed below are the pests which are commonly found in Indigenous communities, along with information about their living and breeding places and food sources.
FliesRubbish, food scraps, open septic tanks, open leach drains, under eaves, dirty benches and tables, lawn clippings and animal faeces.
CockroachesRubbish, food scraps, dirty benches and tables, drains, behind stoves and fridges, bathroom and kitchen cupboards, under floors of older houses, septic tanks and leach drains.
MosquitoesCool, dark and damp places such as rain water in discarded refrigerators, car tyres and tins, and in septic tanks/leach drains, water storage tanks, protected corners of effluent ponds and natural bodies of water.
FleasLike sandy areas. They need blood to breed. They will also bite humans when there are no animals around. Many fleas are brought into houses on peoples clothes, having jumped onto them from outside their house. Fleas are also transported on bedding.
Fleas are usually found on animals like cats and dogs, so it is important that these animals are kept outside the house to reduce the likelihood of fleas infesting houses.
MitesLive and breed on animals and people.
Rats and MiceRubbish, exposed food, storage places, kitchen cupboards and holes in walls. They are also found in pipes, insulation, under buildings, in ceilings and in trees and gardens.
Bed bugsAre transported from place to place in or on a persons luggage or their bedding. They hide in cracks and crevices during the day where people sleep and will seek a blood meal by biting a person in their bed during the night.
Bed bugs also need a blood meal to mature into adults. Bites can be very itchy and if scratched can become infected.
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3.2 FliesThere are many different kinds of flies. Three common types are shown below:
Fig. 5.2: Common types of flies.
Fly life cycleAdult flies lay their eggs in moist organic material, for example, food scraps, animal faeces (droppings), grass clippings or dead animals. After a few hours the eggs turn into larvae, called maggots.
The maggots feed on the organic material and grow quickly. After four or five days the maggots move to dry soil and burrow down into it and turn into pupae. A special hard protective covering called a pupal case encloses each of the pupae while they continue to develop. Pupae are brown to black in colour and can sometimes be mistaken for mice droppings.
After four or five days, pupae turn into adult flies. They break out of the pupal case, burrow up through the soil to the surface and fly away.
Flies are able to travel many kilometres from their breeding place. However, if there are lots of flies around, it usually means there is a good breeding place nearby.
Fig. 5.3: Life cycle of the fly.
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Flies and diseaseWhen flies land on things like food scraps, manure, faeces or dead animals they pick up disease-carrying germs and germs. The germs are carried on their hairy bodies and legs and in their stomachs.
When the flies land on things like food, cups, knives and plates, the germs can be passed on to these articles. If people then eat the food or use these articles when eating food, they will get the germs into their bodies and may become sick.
Flies feed by putting a special substance from its stomach onto the food through its long, hollow, tube-shaped mouth. This special type of mouth is called a proboscis. The special substance which comes from the fly's stomach makes the food liquid and the fly then sucks this up through its proboscis.
Germs from the fly’s legs and body, and from the liquid that comes from its stomach, get onto the food while it is eating. Some of these germs will be left behind on the food after the fly has gone.
This is a list of the diseases caused by germs and parasites which come from flies.
Diseases in Indigenous communities caused by germs carried by fliesBacterial diseases
- hepatitis A
Fig. 5.4: How flies spread germs which cause such diseases as food poisoning and hepatitis A.
When people have cuts and sores on their bodies, disease-carrying flies can land on them and cause them to become infected.
Fig. 5.5: Flies spread germs which cause cuts and sores to become infected.
Bush flies can carry a germ which causes a serious eye disease called trachoma. These flies are attracted to the salt in the tears (moisture) from people's eyes. As bush flies go from one person's eyes to another, they can pass on this disease from one person to the next. The common house fly is also attracted to the moisture around people's eyes. These flies can pass on germs which cause other kinds of eye infections, such as pus eyes.
Fig. 5.6: How flies spread germs which cause trachoma.
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Controlling fliesProbably the best method of fly control is to make sure the flies have no place where they can breed. Some of the ways of getting rid of breeding sites around the home are listed below.
- Wrap all food scraps tightly
- Make sure the rubbish bin has an undamaged, tight-fitting lid that stops flies from getting in
- Empty the rubbish bin regularly (at least weekly and more frequently if there are many people visiting or there is a house with a large family)
- Make sure rubbish is disposed of properly at the rubbish tip and covered regularly
- Make sure the toilet is clean and working properly
- Make sure the toilet vent pipes are fly-proofed
- Make sure that septic tanks and leach drains are not damaged and have proper sealed lids
- Remove dog and other animal faeces daily if possible
- Dispose of faeces and dead animals to the rubbish tip as quickly as possible
3.3 CockroachesThere are many different types of cockroaches and most of them can spread disease. The three main types of cockroach in Australia are the German Cockroach, Australian Cockroach and the American Cockroach.
The German Cockroach is one of the smallest of the cockroaches and is probably the most commonly found species inside buildings. Adults are 12 to 15 mm long, have a light amber/brown colour with two dark stripes on the head.
Fig. 5.7: The German Cockroach
German Cockroaches are mostly found in and around kitchens, pantries, storerooms and other food handling areas. They prefer to be near food, moisture and warmth. They do not fly.
The Australian Cockroach is larger (30 to 35 mm) and is able to fly. It is dark brown with clearly defined yellow markings on the head and the front wings. This cockroach prefers plant food and is usually found outdoors. For example, under the bark of trees and among woodpiles.
The American Cockroach is one of the largest of the cockroaches (30 to 45 mm). It is red brown in colour with a pale yellow border around the head and it can fly. The American Cockroach prefers warm and moist conditions. It is a very widespread pest which lives in wall and roof cavities, sewers, drains, cellars, grease traps and rubbish dumps. It can be found around any food preparation area.
Cockroach life cycleAfter mating, the female cockroach produces an egg case. This egg case can be either carried by the cockroach or left in a secure place until the young are due to hatch. When she is ready, the female cockroach leaves the egg case in a quiet, dark, warm location.
The eggs then hatch, these are called nymphs, they look much like a small version of an the adult. Cockroaches do not undergo a series of marked changes like flies and some other insects. Cockroach nymphs grow to adult size by a series of moulting processes.
In each of these, the nymph sheds its hard outer covering for a new, larger one. Depending on the type of cockroach it may take from one to twelve months for a nymph to grow to adult size.
Note: When cockroaches moult, they will be white in colour, after a day or so they will return to their original colour of brown to dark brown, depending on the species).
Fig. 5.8: Life cycle of the cockroach.
Cockroaches and disease
Like flies, cockroaches can carry many disease-causing germs on and in their bodies. Because their natural homes include rubbish, dirt and filth they readily pick up germs from these areas. They then walk over food, cutlery, crockery and cooking equipment, benches, tables and other places in the home and pass the germs on to people.
Diseases in Indigenous communities caused by germs carried by cockroaches.
- hepatitis A
Controlling CockroachesAll of the suggestions listed to control flies will also help control cockroaches. However, there are other kinds of actions which can be taken to keep cockroaches away from living areas. For example:
- keep food in containers which have tightly fitting lids
- store food handling equipment and containers up off the floor
- where possible, fill in small cracks and crevices (holes), in which cockroaches could hide. It is especially important to fill in cracks and crevices around pipes in walls
- clean shelves and inside and underneath cupboards regularly. This will reduce the build-up of food particles
- when required, apply a low toxicity liquid or gel insecticide to those areas where cockroaches may hide, especially cracks and crevices inside and around the outside of buildings, behind stoves and fridges and underneath the shelves of cupboards. There are many suitable insecticides that can be used to effectively control cockroaches. Before insecticides are used, people should be encouraged to regularly clean in and around their houses to reduce the cockroaches’ food source.
3.4 MosquitoesThe adult mosquito has a proboscis similar to a fly except that it has a needle-sharp end which is used for piercing the skin of a person or other animal to suck blood.
When mosquitoes pierce the skin to suck blood, this can result in the transmission of many serious diseases among humans and other animals. However, most mosquitoes do not carry disease-causing germs, but only annoy people with the itchy ‘bites’ they cause. If people scratch their mosquito bites this can break the skin and lead to secondary infections.
Fig. 5.9: The mosquito.
Mosquito life cycleMosquitoes, like flies, undergo a complete change in appearance as they develop from the egg to the adult. Mosquitoes need water to complete their life cycle, and this water must remain until the adult mosquito is able to fly. If the water should drain away or dry up, the larvae or pupae will die.
Female mosquitoes often lay their eggs on a water surface. After a few days the larvae (which are called wrigglers) hatch from the egg and begin to feed on organic matter in the water. The wrigglers stay in calm, protected water as they cannot breathe properly in rough water. The wrigglers breathe through a siphon (tube), the opening of which is pushed above the water surface. Rough water will stop them from being able to breathe.
Some mosquitoes, however, will lay their eggs in moist areas just above the water level, for example, on leaves, blades of grass or on mud next to a waterhole. These eggs will lay dormant (asleep) for a period of time when the conditions are not right for them to hatch, for example, if it is too dry. When the conditions are right, such as when the rains come, the area floods, or there are high tides, the water will cover the eggs and they will hatch within 1 to 2 days.
After several days the wrigglers change body form and become pupae which are also called tumblers. The tumblers do not feed but they do move around.
After 1 to 4 days the adult mosquito comes out of the pupal case. It stays on the surface of the water until it dries out and then flies off. This drying off time is dangerous for the mosquito because it is easy for it to be attacked and eaten by other insects, frogs or birds.
The length of the life cycle will vary from one type of mosquito to another, but usually takes between 5 and 10 days at temperatures above 30°C and up to 3 weeks at temperatures lower than 20°C. A rise in the temperature of the water may speed up life cycle.
Adult female mosquitoes may live for several weeks.
Fig. 5.10: Life cycle of the mosquito.
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Mosquitoes and diseaseBefore the female can lay her eggs, she must have a blood meal. She gets this blood by sticking her proboscis into the person or animal’s skin and sucking out the blood, often called a mosquito ‘bite’. The time when biting is most likely is at dawn and dusk.
Fig. 5.11: Mosquito piercing skin with its proboscis to suck blood.
If a mosquito takes a blood meal from a person or animal that is infected with these virus germs then the virus will grow inside the mosquito. If it later bites another person or animal, it may pass on some of the virus germs, and that person or animal may catch the disease. This cycle can go on and on, infecting lots of people and animals and causing a disease outbreak with lots of sick people.
Many people all over the world have died as a result of diseases transmitted by mosquitoes.
Fig. 5.12: Mosquitoes carry disease.
Diseases in Indigenous communities caused by germs and carried by mosquitoes
Ross River virus diseaseThe mosquitoes likely to carry Ross River virus breed in salt marshes, tidal flats, shallow freshwater swamps, poorly maintained sewage lagoons and containers such as old tyres and drums.
Murray Valley encephalitis (also called MVE)The mosquitoes likely to carry Murray Valley encephalitis virus breed in open, shallow freshwater swamps and poorly maintained sewage lagoons.
Barmah Forest virus diseaseThe mosquitoes likely to carry Barmah Forest virus breed in salt marshes, tidal flats, shallow freshwater swamps, poorly maintained sewage lagoons and containers such as old tyres and drums.
Kunjin virus diseaseThe mosquitoes likely to carry Kunjin virus breed in open, shallow freshwater swamps and poorly maintained sewage lagoons.
To keep an eye on whether Murray Valley and Kunjin viruses are around, sometimes there are ‘sentinel chicken flocks’ in communities. Chickens will get these diseases before people do so blood samples are taken from the chickens to see if there is any of the virus around that might affect people living in the community. The EHP may be able to help by caring for (feeding and watering) the chooks and taking blood samples that are sent to a laboratory for testing. Sentinel chickens are no good for knowing if Ross River or Barmah Forest virus are around.
Dengue feverAt the moment, dengue fever is only a problem in north Queensland because it’s currently the only part of Australia where the dengue fever mosquito breeds. The dengue mosquito breeds in water-holding containers, including rubbish left lying around people’s yards. This mosquito will bite indoors and during the day. The risk of dengue in north Queensland can be reduced by regularly emptying water if it has collected in containers in the yard or by removing these containers altogether.
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Controlling mosquitoesAs with most insect pests, the best way to control mosquitoes is to get rid of their breeding sites. This means making sure that water is not allowed to collect in unwanted equipment and containers which are left lying around.
These containers might include:
- car bodies and panels, engine blocks and tyres
- tin cans, plastic containers, drums, lids and jars
- water which has collected in blocked gutters and drains
- water tanks, septic tanks and leach drains which do not have lids
- still areas of water in sewage lagoons
- pools of water lying under leaking taps
Fig. 5.13: Common mosquito breeding places.
It is important to make sure that there are always lids on water tanks, septic tanks and leach drains and that sewage ponds are kept free of grass and other vegetation around the edges.
For those mosquitoes which do manage to breed somewhere and become a pest in the community, it is important to keep them out of houses.
Putting up flywire on all door openings and windows is a good way of keeping mosquitoes out. Wearing cover-up clothes and using insect repellent on exposed skin reduces the risk of being bitten when outside during the biting times. Loose clothes are best because mosquitoes can bite through clothing which is tight against the skin, even jeans. Sleeping children and babies should be protected with mosquito nets. Insect repellent should never be used on babies – cover them with a net instead.
Sometimes when the mosquitoes are really bad or if there is lots of mosquito disease around, the mosquitoes might need to be controlled using pesticides. There are two types of pesticides – one that kills the wrigglers in the water and one that kills the adult mosquitoes that are flying around. A properly trained person who has a special pesticide license will need to do this work.
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3.5 Rodents (rats and mice)Rodents comprise a group of furred, warm blooded animals which include rats and mice. In Australia, there are a number of introduced (feral) rodents which are pests around homes, shops and warehouses. These are:
- the ground rat (also called the Norway rat)
- the roof rat (also called the climbing or black Rat)
- the house mouse (also called the field mouse)
Fig. 5.14: Rodents show picture of a typical house mouse
Rats and mice differ in size, mice being much smaller than rats. Ground and Roof Rats are similar in size. However, they differ in some ways.
Fig. 5.15: Differences between Ground and Roof Rats.
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Rodents and diseaseRats and mice, like other animals which live in rubbish tips, drains, sewers and other unhygienic places, pick up disease-causing germs from their environment. They then become carriers of these germs and can spread dangerous diseases by entering our houses. Six hundred years ago, roof rats and their fleas were responsible for spreading the bacteria which caused bubonic plague (the Black Death) throughout Europe. Twenty-five million people died in this plague.
Rats and mice may pass disease-causing germs to humans in several ways, such as:
- carrying disease-causing germs from sewers, drains and rubbish tips to food, kitchen benches, storage areas and utensils
- depositing infected urine or faeces on food utensils
- depositing infected urine or faeces in places where people can come in contact with it
- biting people
- passing the germs to household pets, which then pass them on to humans.
Fig. 5.16: Rats spread germs which cause disease.
Diseases in Indigenous communities caused by germs carried by rodents
- rat-bite fever
- they can destroy large amounts of stored grain in bulk stores and silos by contaminating it with their urine and faeces
- their habit of constantly gnawing (chewing) causes much damage to doors, skirtings, upholstery, books, food and other packaging, wires, cables and pipes.
Controlling rodentsAll of the good hygiene practices listed for other pests will also help to keep rodent numbers low. It is also possible to design a building that makes it difficult for rats or mice to enter, although as long as people have access to buildings, these rodents will often also find a way to gain entry.
Flywire doors and window screens also help to keep rodents out of houses.
Other methods of controlling rats and mice are to use traps and poison baits. Ensure that baits are placed well out of the reach of children and pets, such as cats and dogs.
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3.6 Bed bugsBed bugs are small insects about 4-6mm in length. They are flat in shape and when they hatch are cream in colour, turning reddish brown as they mature. When they have a blood meal they turn dark brown. There is no evidence to date that these insects transmit disease. They are often brought into a house by people who may have recently travelled interstate, overseas or visited relatives in a nearby town or community. Bed bugs attached themselves to luggage, bedding, furniture and so on. Then when any of these items are brought into a house, the insects run off and hide and wait for a person to bite. They often bite while a person is sleeping.
Bed bugs can quickly infest most areas of a house, particularly bedrooms and are difficult and very expensive to treat/eradicate. Often people have to throw away their mattresses and start again. Simply buying a new mattress will not get rid of bed bugs, as rooms have to be treated with insecticides and where possible steam or a combination of both.
The life cycle is as follows:
- Eggs – clusters of three or more stuck together, they are white in colour
- Eggs hatch in 6-17 days and form nymphs, (nymphs shed their outer skin, 5 times)
- Nymphs turn into adults after 5-12 weeks
- Adults are very mobile as they are good walkers and can run
Controlling Bed Bugs
- Thoroughly inspect used bedding (including mattresses and bed frames) before it is brought into a house.
- Inspect luggage before it is brought into a house and never put your luggage or that of others onto your bed, as bed bugs attached to the outside of the luggage will jump off and infest your bed.
- If bed bugs are found, a combination of treatments is likely to be necessary for all rooms of the house, particularly bedrooms. It is likely that both insecticides and steam will have to be used. Insecticides alone will not kill the eggs, whereas steam will kill all growth stages. It is recommended that only a properly trained person is brought into treat for bed bugs. Two or more treatments might be required to eradicate these insects costing many hundreds of dollars, so preventing them infesting a house in the first place is important. Educating a community on the ways bed bugs can travel and where they could be found in a house is important. There are brochures available from the Dept of Health, the local government or council or from the Dept of Health web site. There is also a national Code of Practice developed for the control of these insects.