Red mite, once thought to be a disease of the past, is now a cause of increasing problems in the free range layer and in other sectors of the poultry industry. It is particularly severe in the summer months when the weather is warm and mites are able to multiply quickly.
WHAT DOES RED MITE INFECTION DO TO A FLOCK?
· Mites irritate the birds and can make the flock unsettled and nervy.
· The incidence of peritonitis may increase and there may be increased vent pecking.
· Feed intake may be depressed.
· Heavy mite infestation can depress egg production by up to 5%.
· Heavy infestation will make birds anaemic due to loss of blood. Birds will be evident in the flock with pale combs and, if severely affected, mortality may increase.
· There may be loss of shell or yolk colour and, with heavy infestations, there will be evidence of mites and mite faeces on eggs and egg belts which may lead to downgrading of speckled eggs.
· There may be an increase in floor eggs as birds will be reluctant to use heavily infested nests.
· Where there is a big problem with mite, there may be problems for egg collectors with skin irritation.
THE LIFE CYCLE OF THE MITE
The life cycle of the mite from egg to adult lasts 9-12 days. Each female mite can lay up to 40 eggs in her lifetime. Adult mites can survive up to 10 months in an empty building without needing to feed. The red mite tends to feed on birds mainly at night. During the day, the mite often retreats to cracks and crevices in the building and often accumulates in large numbers in nest boxes. The Northern Fowl mite can also cause problems in chickens but, unlike the red mite, the Northern Fowl mite tends to spend most of its time on the bird, thus control of these two different types of mite may require a slightly different approach because of their different lifecycle. Mites may be introduced onto a site with point of lay pullets, from wild birds or brought in on contaminated equipment, e.g. egg trays or clothing.
HOW DO YOU CONTROL RED MITE IN FLOCKS?
Biosecurity. With any site, but particularly with new sites, it is very important to try and avoid or delay the introduction of red mite onto the site. Point of lay pullets should be free of mite, buildings should be proofed against wild birds as far as possible. Care should be taken that no contaminated equipment is used. All visitors should wear protective clothing provided on the site.
· Monitoring. Careful monitoring with frequent examination of areas such as nest boxes, legs and lips of feed tracks or areas under feed tracks should be checked for any early signs of mite infestation. There are various techniques suggested for checking areas, e.g. holding a sheet of white paper underneath feed track and tapping the track gently so that any mites there will fall onto the paper and be easily visible. Careful monitoring allows you to treat the problem as early as possible. It is vital to treat affected areas as soon as the first sign of mites is detected and not to wait until the problem has escalated. Once you see mite staining on eggs or egg collectors are complaining of mites, then you already have a very high level of infestation in the house.
· Use of insecticides. Carbaryl was one of the more effective insecticides to control mite but this has now been withdrawn. A variety of products are now used including Cypermethrin, Fenitrothion and Diclorvos. In addition, other compounds are used, some of which are not licensed for use in animal accommodation. Because of the small market for this type of product, it is unlikely that many new formulations will become available.
· Because mites are so small and can be present in such large numbers, effective control while the flock is housed is very difficult. Insecticides can be applied with a knapsack sprayer to slats, nest boxes and other affected areas. The use of a crevice nozzle will enable insecticide to be targeted into cracks where mites may be lurking. Unfortunately, mites are able to detect insecticides and can retreat away from the product and re-emerge later.
· Breaking the cycle of reinfection when the house is empty is the most effective approach. As soon as birds are removed, a "knock down" type insecticide should be used before the house cools and mites retreat into the woodwork. Following this, equipment and house furniture should be removed and dismantled as far as possible and physically cleaned. The inside and outside of the building should receive a very thorough wet cleaning. Once the building and the cleaned equipment is dry, the surfaces can be sprayed with a residual insecticide before the next flock is housed.
· Creosote treatment of woodwork where possible will be helpful in repelling mite. However, this cannot be used where there is any risk of tainting eggs.
· Where possible, look at design of houses and equipment to try and provide impervious and easy to clean surfaces, to reduce the use of wood in the house, design of feed tracks and other pieces of equipment to reduce the number of areas where mites may congregate.
· Where possible, change the type of insecticide used between flocks to reduce the likelihood of resistance as there does appear to be a fair bit of resistance to some products.
CONCLUSION
There is no simple answer to red mite control. Effective control is very time consuming as it requires a great deal of time and effort to clean and treat houses but it is vital to carry out this work between flocks to prevent problems in subsequent flocks. Control relies on first of all physical cleaning to remove mites, coupled with careful and meticulous application of an appropriate insecticide to all affected areas. There is a limited amount of research going on into alternative methods of red mite control such as the use of tracks where a sticky surface may physically trap the mites. Another product suggested is inert braided silicone balls, which can damage the mite exoskeleton leading to dehydration and death. When attacking the mite problem, you should remember that many of the insecticide products used can be toxic and you should ensure that all health and safety recommendations are carefully followed and that there is no risk of contamination of, for example, ground water or risk to non target species as some of these products are very toxic to fish and bees. It is important to use all products as recommended and, in particular, to avoid spraying hens or eggs with products intended for environmental use only to avoid the risk of residues in eggs.
