Mites are the most damaging external parasites (ectoparasites) of poultry. There are two major groups of poultry mites, those that suck blood, and those that don't suck blood.
Bloodsucking poultry mites behave rather like soft ticks. The most important species are:
- Dermanyssus gallinae, the red fowl mite: worldwide in all climatic regions.
- Ornithonyssus sylviarum, the northern fowl mite: especially in the Northern hemisphere.
- Ornithonyssus bursa, the tropical fowl mite: worldwide in tropical and subtropical regions.
Non-bloodsucking poultry mites behave rather like mange mites. The most relevant species are:
- Cnemidocoptes gallinae, the depluming mite, the itch mite: worldwide.
- Cnemidocoptes mutans, the scaly leg mite: worldwide.
- Epidermoptes bilobatus, the scaly skin mite: worldwide.
Regional incidence and prevalence can be quite different, e.g. the northern fowl mite,Ornithonyssus sylviarum, seems to be the most common in North America. Globally, the red fowl mite, Dermanyssus gallinae, is the most frequent and damaging species, among other reasons because resistance to acaricides is very frequent, which makes it particularly difficult to control.
Bloodsucking mites are vectors of various poultry pathogens, i.e. thy can transmit several microbial bird diseases. Non-bloodsucking mites are not vectors of bird pathogens.
Infestations with mites are technically called acariosis or acariasis, both on animals and humans.
Click here to learn more about the general biology of mites.
Biology and life cycle of poultry mites
The red fowl mite (also called red poultry mite, roost mite, chicken mite, etc.) is a parasite that occurs worldwide and can infest numerous domestic and wild bird species. Occasionally it can also attack humans, and there is new evidence that it can complete its life-cycle on humans as well. It is an obligate bloodsucking parasite, i.e. it can neither survive nor develop without blood.
Dermanyssus gallinae is the most damaging species among the poultry mites. It affects mainly laying hens, and can be a serious problem in industrial operations as well as in traditional, backyard and hobby farming.
Adult females lay eggs off the birds in their hiding places, which hatch 2 to 3 days later. They lay 4 to 8 eggs at a time, a total of about 25 eggs during her lifetime. A blood meal is required after each egg laying. Hatched larvae do not feed and molt to nymphs 1 to 2 days later. Nymphs suck blood and after various molts they become adults in about 4 to 5 days.
Under favorable conditions (hot and humid weather) they can complete their life cycle as shortly as in 7 days: Huge mite populations can build-up in a few weeks. Adult mites live for about 8 weeks, but they can survive up to 5 months without feeding. Development slows down with low temperatures and is almost interrupted below 9°C. For this reason infestation of birds kept outdoors often are only a summer problem in many regions.
Adult mites are 0.6 to 1 mm long, and have a dark reddish, or a whitish to grayish color, depending on whether they have sucked blood or not. Adults and nymphs usually attack the birds at night and suck blood. Each blood meal lasts for 1 to 2 hours. Mites leave the host during the day to hide in cracks, crevices and hollow places (e.g. in troughs and feeders, walls, floors, etc) close to the birds (also in the birds nests), where they can be often found in clustered by the hundreds or thousands. In very high populations the mites may feed on their hosts also during the day. Mites on the birds are found especially around the beak and the ears, on the breast, back and legs.
Harm to birds can be considerable. The mite's bite is itching and causes skin inflammation. The leg's skin may become thickened, crusty and scaly. The birds are considerably stressed. They scratch and bite themselves intensively. This can produce injuries and feather loss. Blood loss, i.e. anemia can be severe and even fatal, considering that hundreds and even thousands of mites may be sucking blood at the same time on a single bird. Young birds are particularly susceptible. Decreased egg production in laying houses can be substantial. Stress and anemia make the birds more susceptible for other diseases.
On top of this, Dermanyssus mites transmit several diseases, e.g. avian spirochaetosis, Salmonella gallinarum (fowl typhoid) and Erysipelothrix rhusiopathiae, even after months without contact with infected birds.
Dermanyssus mites can infest poultry operations through numerous routes. Wild birds that visit poultry houses can introduce mites. Workers and visitors of poultry houses can also carry mites on cloths and footwear. Mites make be transported from one poultry house to another one within egg baskets and flats, barrows and many other items.
Diagnosis of is made examining mites collected in the poultry house. Mites can be collected by putting dead birds in plastic bags, covering the cages with a white cloth during the night, putting double stick tape on perches or in cages during the night, etc. The mites can be than examined under a magnifying glass or under a microscope. Eggs with blood spots indicate infestation of the bird's cloaca. Anemic birds may show paleness of wattle and comb.
The northern fowl mite is also an obligate bloodsucking parasite. It occurs worldwide in regions with temperate climate. It is a major pest in intensive poultry operations, especially in layers but also in breeder-broiler operations as well as in free ranging and backyard chicken. In the USA it is even more abundant than the red fowl mite. It attacks many domestic and wild bird species, but also rodents such as rats and mice, which can significantly contribute to its transmission. Northern fowl mites can also infest and bite humans.
Adult mites are 0.6 to 1 mm long. Unlike red fowl mites that visit their hosts only for feeding, northern fowl mites spend their whole life on the host. All development stages (i.e. larvae, nymphs and adults) can be found on the birds, mostly on the skin around the base of the feathers. Infestations often start around the vent and then spread towards the tail, the legs and the back. Since the mites spend their whole life on the birds, the feathers become progressively soiled with excrements, dead mites, dried blood, etc. This cumulated dark dirt on the base of the feathers, particularly around the vent is often a clinical symptom for diagnosis.
Adult females lay 3 to 5 eggs at a time. A blood meal is required after each egg laying. Larvae hatch about 2 days later. Larvae do not feed and molt to nymphs 1 to 2 days later. Nymphs suck blood and after various molts become adults in about 4 to 5 days. Under favorable conditions they can complete their life cycle as shortly as in 7 days: Huge mite populations can build-up in a few weeks. Individual mites can survive off-the host for about 3 weeks without feeding.
In breeding operations roosters tend to be more heavily infested than hens. In regions with a cold winter mite populations increase as the weather gets colder, peak in late winter and spring, and diminish progressively as the weather becomes hotter.
Northern fowl mites can infest poultry operations through numerous routes. Wild birds that visit or nest in poultry houses can introduce mites. Rats and mice can transmit mites from one poultry house to another one. And also workers and visitors of poultry houses can disseminate mites on cloths and footwear. Mites make also be transported from one poultry house to another one within egg baskets and flats, barrows and many other items.
Harm to the birds can be substantial, especially for young birds. The mite's bite is itching and causes skin inflammation. The birds are considerably stressed. They scratch and bite themselves intensively. This can produce injuries and feather loss. Blood loss, i.e. anemia can be severe, however deaths are uncommon. Young birds are particularly susceptible. However, individual birds may show significantly different susceptibility. Whereas one bird in a cage can be infested, other birds in the same cage may be not. And individual birds may support several thousand mites without major harm. By heavy very heavy infestations egg production in laying hens can decrease by up to 25%.
In addition, northern fowl mites transmit several diseases, e.g. Pasteurella multocida that causes avian cholera, the Newcastle disease virus.
Northern fowl mites can also bite workers in the poultry houses, and particles of mite feces in the air can cause allergic reactions. This problem can become a serious issue: workers may refuse to work under such unsafe conditions.
Diagnosis is usually done inspecting the vents of the birds for presence of mites and subsequent examination of the mites under microscope. The presence of abundant dirt at the base of the feathers is also a typical symptom of northern fowl mite infestation.
The tropical fowl mite infests chicken as well as other domestic and wild birds in most tropical and subtropical regions of the world. In certain regions it occurs together with the northern fowl mite. The behave very much like the northern fowl mite, have a similar life-cycle and are as harmful to poultry as northern fowl mites.
A particular feature of tropical fowl mites is that they can cumulate in the nests of wild birds in and around human dwellings. When the wild birds leave their nests, hungry mites move into the buildings searching a prey, and they will attack any human they find.
Cnemidocoptes gallinae = Knemidocoptes Gallinae = Neocnemidocoptes gallinae
The depluming itch mite is another quite small (~0.5 mm) that infests domestic birds such as chicken, pheasant, pigeon and goose. However, it is not as frequent as other mite species and prefers warmer climates. It does not suck blood, but burrows into the skin along the shafts of the feathers, which easily break. Affected birds bite themselves vigorously and may pull out their own feathers. It can also cause cannibalism among the birds.
The lifecycle can be completed in about one month. Transmission is by direct contact between the birds. Infestations in modern operations are rare, more frequent on free ranging and backyard birds. For diagnosis a a few feathers close to a lesion can be pulled out and examined under the microscope.
Cnemidocoptes mutans = Knemidocoptes mutans = Neocnemidocoptes mutans
The scaly leg mite is another small (~0.5 mm) mite that infests chicken, turkey and other domestic and wild birds worldwide. It does not suck blood but burrows into the skin tissues under the leg scales, causing inflammation and exudation. It is more common in old birds whose legs become thickened, crusty and deformed.
The life cycle can be completed in 10 to 14 days and occurs entirely on the host. It is quite contagious and the birds often get the mites from the ground. It is uncommon in industrial operations but can be a problem in traditional and backyard chicken. Diagnosis is done based on the typical leg deformations and after identification of mites of skin scrappings of the legs.
The scaly skin mite is another very small mite (0,2 mm long) that attacks chicken and other birds worldwide. It does not suck blood but lives on the birds skin. It can cause dermatitis with appearance of scabs that can be infected with secondary bacteria. Predilection sites are the breast, the neck and the head. Infestations are infrequent, but heavy ones can cause considerable harm, including fatalities.
Prevention and control of poultry mites
For the time being there are no vaccines that will protect chicken or other domestic birds by making them immune to the mites. There are no repellents, natural or synthetic that will keep mites away from poultry.
There are so far no biological control means for controlling poultry mites (or any other mites of livestock and pets). Learn more about biological control of ticks and mites.
Non-chemical control and prevention
Dermanyssus gallinae is a serious problem worldwide, particularly in laying and breeding operations. Most premises offer numberless hiding places for the mites: slatted floors, hollow places in tubes, posts, troughs, feeders, transport chains, perches, cracks and crevices in floor and walls, etc.
A first measure to prevent or reduce Dermanyssus populations is to eliminate the hiding places as much as possible. However, this may require a significant investment in remodeling the facilities. Modern premises designed to minimize the mite harborages are in fact less likely to become infected.
Since wild birds can transmit mites, their nests in or around the poultry houses must be systematically eliminated, and access of wild birds to the poultry houses must be prevented through grills, screens, nets, etc.
Whatever items and equipment used for transport between poultry houses, e.g. egg baskets, flats or boxes, barrows, etc. must be disinfected at high temperature before going from poultry house to poultry house.
Sticky traps can catch a lot of mites but are usually insufficient to control severe infestations. Nevertheless they can be useful to monitor the mite population.
Silica gel dusts cause dessication of the mites and can reduce their populations in poutry houses. However they are not sufficient to eliminate them.
Search for a non-chemical control has shown promising results with a vaccine consisting in soluble mite extract that provided up tp 78% control of mites in field trials. However, a cocktail containing bacterially-expressed versions of several immunogenic SME proteins was used no efficacy was achieved.
Good results for controlling these mites has been obtained through heating layer hen houses between consecutive laying cycles. Heating at 45°C for 48 hours killed all adults, nymphs and eggs at different locations in such laying houses, including under the floor and in the manure.
Dermanyssus mites spend most of their time off the birds. Therefore chemical treatment must target the hiding places. This is best done when the poultry houses are empty between to cycles and must be preceded by exhaustively cleaning and disinfecting of the whole poultry house and its equipment. Dipping, spraying or dusting the birds is mostly inefficient.
There are a number of old parasiticides for the treatment of the hiding places against Dermanyssus mites. They contain mainly veteran active active ingredients such as organophosphates (e.g. coumaphos, chlorpyrifos), carbamates (e.g. carbaryl) and synthetic pyrethroids (e.g. cypermethrin, deltamethrin, flumethrin). The problem with most such product for Dermanyssus control is that mite resistance to most of them is widespread and very high, particularly resistance to synthetic pyrethroids. In fact, it is not rare that the only option left for solving the problem is demolishing the old poultry house and building a new one better designed to prevent mite infestation.
To reach the hiding places power spraying is highly recommended. Dusting is not adequate for controlling Dermanyssus, since dusts do not adequately reach the hiding places. It is important to remember that many parasiticides approved for off-animal use on poultry houses are not approved for directly treating the birds.
An alternative to spraying can be in placing acaricide-impregnated self-made mite traps inside de poultry houses close to the birds (cages, perches, etc.). Such traps can consist in anything where mites can hide in, e.g. rolls or pieces of corrugated cardboard, plastic or metal tubes, etc. Impregnation can be done with the same acaricides used for power spraying. However, most commercial products have no use recommendations for this usage. Nevertheless, since the birds are not exposed to the chemicals, the risk of poisoning or illegal residues in eggs or meat should be quite low.
The good news is the introduction in the 2010s of two new products without cross resistance.
- One contains spinosad (ELECTOR PSP ) approved in several countries (e.g, USA, EU) for premise mite control, which is effective against mites resistant to the veteran acaricides and can even be used on premises in the presence of the laying hens. Hopefully it will soon become available worldwide.
- Another new product (EXZOLT) introduced in the EU in 2017 contains fluralaner, an isoxazoline, and is highly effective against red fowl mites, included those resistant to old acaricides. It is approved for oral administration mixed with the drinking water and has a systemic mode of action, i.e. it acts through the blood of the treated birds. It has a NIL withholding period for eggs.
Macrocyclic lactones (e.g. ivermectin, moxidectin), whether for oral delivery or as injectables do not control fowl mites: the effective dose would be very close to the dose that is toxic for the birds. Moreover, in most countries macrocyclic lactones are no approved for use on poultry.
Ornithonyssus sylviarum & O. bursa
Non-chemical control and prevention
To prevent the infestation of mite-free poultry houses it is essential to keep wild birds away. Their nests in or around the poultry houses must be systematically eliminated, and access of wild birds to the poultry houses must be prevented through grills, screens, nets, etc.
Since rats and mice can transmit these mites as well, adequate rodent control is also an important preventive measure.
Whatever items and equipment used for transport between poultry houses, e.g. egg baskets, flats or boxes, barrows, etc. must be disinfected at high temperature before going from poultry house to pouktry house.
Silica gel dusts cause dissication of the mites and can reduce mite populations in poultry houses. However they are not sufficient to eliminate them.
There are reports on effective control of northern fowl mites using thuringiensin (the exotoxin of Bacillus thuringiensis) sprayed directly to the birds.
Unlike red fowl mites, northern and tropical fowl mites spend their whole life on the birds. Consequently chemical control of the mites requires treating the birds directly. There are a number of parasiticides for this purpose, either for dipping, spraying or dusting the birds. They contain mainly veteran active ingredients such as organophosphates (e.g. coumaphos, chlorpyrifos), carbamates (e.g. carbaryl) and synthetic pyrethroids (e.g. cypermethrin, deltamethrin, flumethrin). However, there are also northern and tropical fowl mite populations resistant to such veteran acaricides, although the problem is not as acute as with red fowl mites.
Insecticide-impregnated plastic strips suspended inside birdcages have also been used successfully against northern fowl mites.
As for red fowl mites, there are no feed additives or whatever products for oral delivery that adequately control northern fowl mites.
Macrocyclic lactones (e.g. ivermectin, moxidectin), whether for oral delivery or as injectables do not control northern or tropical fowl mites: the effective dose would be very close to the dose that is toxic for the birds. Moreover, in most countries macrocyclic lactones are no approved for use on poultry.
Other poultry mites that do no suck blood (Cnemidocoptes, Epidermoptes, etc.)
Epidermoptes and Cnemidocoptes mites spend their whole life on the birds. Consequently chemical control of the mites requires treating the birds directly. The products that control blood-sucking mites, either for dipping, spraying or dusting the birds will control these mites as well. They contain mainly veteranactive ingredients such as organophosphates (e.g. coumaphos, chlorpyrifos), carbamates (e.g. carbaryl) and synthetic pyrethroids (e.g. cypermethrin, deltamethrin, flumethrin).
For the control of scaly leg mites the legs can also be treated with Vaseline, or dipped twice in mineral oil, kerosene, linseed oil or any of the previously mentioned parasiticides. Since these mites are highly contagious all the birds in a herd must be treated.
Disinfecting the birds' quarters is highly recommended as well.
|If available, follow more specific national or regional recommendations or regulations for mite control.|
Click here to learn more about the general features of parasiticides.
Resistance of poultry mites to parasiticides
Resistance of the red fowl mite, Dermanyssus gallinae to veteran acaricides is worldwide a very serious problem. There are populations highly resistant to organophosphates, carbamates and synthetic pyrethroids, sometime even multi-resistant, i.e., resistant to two or more chemical classes with different modes of action. Resistance factors can be so high that even undiluted acaricides will not kill the mites.
This means that if a product with and active ingredient belonging to the previously mentioned chemical classes fails to achieve the expected efficacy, it is quite likely that there is already a resistance problem in the farm. In this case another product should be tried, ensuring that it has a different mode of action than the one that failed.
There are also reports on northern fowl mite populations resistant to acaricides. However, the problem seems to be so far less acute and widespread than with red fowl mites.
There are no reports on resistance of non-bloodsucking mites to parasiticides.