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Environmental Health
~ Ratonga Tiaki Taiao

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Rats And Mice

The presence of rodents is most often noted by their droppings rather than actual sighting as they are nocturnal. Damage caused by the gnawing of rodents may also be seen, either on structures or food containers themselves. Rats tend to develop specific pathways and may leave behind greasy rub marks along the walls against which they travel. Sometimes their odours may be detected.

Rats will have 3 - 5 litters of 7 - 8 young per year. Mice can have about 6 litters of around 10 young per year. These young will of course breed quickly themselves.

Rodents are hazardous both because of damage they cause and they are excellent vehicle of infection. They breed prolifically, they are very clever, have no fear and cover a fairly large territory. They spoil far more than they eat simply because they live in such unhygienic environments. For example; rats often use our sewers as travel routes from one place to another. They contaminate foods and surfaces simply by touching them and are known to harbour numerous bacteria harmful to humans.

Traps can be used to catch them but poisoning works better as it exposes more rodents at a time. The most commonly used poisons are warfarin based, which kills by causing internal bleeding. This usually means the rodents go back to their lairs and die without the need for you to dispose of them.

Poison must be laid so that it cannot be accessed by any other creature. Inspect the bait station for chew marks and continue to replace the poison until it hasn't been touched for a week. Vigilance is required for repeat infestations. The poison is best secured into the bait station in some way so that it can be easily monitored for evidence of taking.

Flies

Flies also carry diseases mechanically and internally like rodents do. Their presence is much easier to determine as they aren't nocturnal. Their dirt can be seen on any surface. If food has been left out, especially meat, their eggs can be seen and later the maggots then pupae, before more flies hatch. Maggots can appear within hours of eggs being laid. Their breeding cycle is especially efficient in hot humid weather. Flies don't digest solid food but regurgitate acidic stomach contents to dissolve the current meal.

Insecticides and electronic insect killers are the most commonly used control methods. Insecticides can be contact or residual but contamination of food by these chemicals must also be avoided. Placement of electro blitz machines must consider where the blitzed fly carcasses may fall. These are most efficient out of direct sunlight.

Cockroaches

Cockroaches like rodents tend to be nocturnal. They can be found in the warm motor compartments of fridges and behind ovens and hot water cylinders. Indications of their presence are a characteristic musty odour, stains from their droppings and shed exoskeletons. Expert extermination is best as different life stage require different types of controls. Cockroaches have wings but seldom fly. They can live up to a year and produce 500 young in that time. They are also known to carry diseases harmful to humans.

Others

Ants, silverfish, moths, weevils and beetles and spiders aren't necessarily carriers of disease but are sill troublesome, offensive and can cause extensive damage for food supplies. They are a sign that cleaning is not sufficient, stock rotation is too slow and can become contamination by their very presence.

If they don't behave themselves, other humans can be pests too. Keep anyone who isn't directly involved in food preparation or cleaning, out of the kitchen or they may contaminate food or freshly sanitised surfaces. Have deliveries left in another room or made while someone is there to supervise it (and put things away immediately).

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