Red mite infestation is now one of the main problems of commercial layer production affecting cage, barn and free range flocks.
The problem is with us throughout the year but in the summer months when environmental temperatures are high mite numbers can increase very rapidly indeed and control becomes a nightmare.
The two main parasitic mites of commercial poultry in the UK are the Red Mite - Dermanyssus gallinae and the Northern Fowl Mite – Liponyssus sylviarum. Red mite is the more common of the two. Both mites are bloodsucking, the female mite requiring a meal of blood from the chicken in order to lay her eggs. Heavy mite infestation in a flock may cause:
Physical irritation of the birds which may lead to depressed feed intake, feather or vent pecking and depressed egg production.
Reluctance to use heavily infested nests – leading to a potential increase in floor eggs and sometimes peritonitis.
Anaemia due to blood loss – affected birds are dull and weak with pale combs.
Pale yolks and stained eggs – eggs may be marked with mite faeces/squashed mites.
Skin irritation in egg collectors.
Spread of disease organisms such as Pasteurella from bird to bird within an infected flock.
Severely affected flocks can show increased mortality due mainly to blood loss. The total blood volume of a chicken is around 120ml and although each individual mite only takes a small amount of blood, once you have a situation where thousands of mites are feeding night after night then it is easy to understand how birds quickly become debilitated.
Once a hen is anaemic everything becomes an effort and even moving about within the shed or getting from litter to slats is difficult for her. Many severely anaemic hens die when trying to lay as the extra exertion required is too much for them.
As well as increased mortality affected flocks often show depressed production and even if the mites are removed it can take the flock some time to fully recover.
Solutions?
Control of red mite is very difficult due to the limited number of products available and the practical difficulties of applying products within poultry houses. The mites are tiny and can easily hide up and evade treatment. Control measures fall into three main categories:
Physical removal – eg vacuuming, brushing, blow torching
Chemical treatment with insecticides of house and/or birds.
Abrasive or dessicant products which damage the mite exoskeleton.
Red mite feed on the bird (usually at night, or in the nestboxes) but spend much of their time off the bird and lay their eggs in the shed. Northern Fowl mite on the other hand tend to spend most of their time on the bird and lay eggs on the bird. The treatment approach is thus different as if Northern Fowl mite is involved it is necessary to spray the birds to treat the mite whereas with the Red mite, treatment of the house environment can remove most of the mite burden.
It is unlikely that many producers will achieve complete freedom from red mite in poultry houses but keeping the mites at a very low level will minimise the adverse effects on birds and staff.
Houses should be treated thoroughly when a flock goes out and the chosen control product copiously applied. Once the new flock is in, early detection of mite problems is essential so that treatment can be instigated as soon as mites are seen. Regular checking of nestboxes and other high risk areas should be in place. If birds are handled or dead birds picked up these should be checked for mite (best places to look include under the wings and in the feathered area of the leg just above the shank).
If on a site, particularly multi-age, where there is a known mite burden regular treatment may need to be in place as a pre-emptive strike.
When treating do not skimp on the product applied – unless products are applied as recommended by the manufacturer and applied to all areas where mites may lurk then they will not be effective.
It is also important to have the right equipment to apply the chosen products - seek the manufacturer’s advice on this. Effective treatment is very expensive both in terms of time and money but ineffective treatment costs more as you may be left with a poorly performing flock.
At present we do not seem to have the weapons of mite destruction we ‘might’ like – we hope that the ongoing research into a vaccine may one day provide a better solution.