Scaly Leg Mite Information Sheet

This fact sheet is designed to improve understanding of Scaly Leg Mite infections in poultry and managing treatment. 
 

Scaly Leg Mite Lifecycle
In order to fully discuss treatment options for the treatment of Scaly Leg Mite, it is important to understand the life cycle. Although these mites can infect wattles and also ceres in parrots, this help sheet will confine its comments to poultry scaly leg mite.  There are a number of mite infections in poultry, so do not confuse the scaly leg mite with other types of mite. 

Knemidocoptes species mites (also written as Cnemidocoptes) – of which the scaly leg mite of poultry is C mutans – spend their entire three-week life cycle on their bird hosts (poultry, turkeys, pheasants). The females are viviparous – that is they lay live larvae which have developed in the body of the adult.  The infection can be confirmed by soaking off an infected scale and having this examined by a laboratory. The base of the scale needs to be carefully removed, as this is where the lab will find the mites. However, usually diagnosis on symptoms is very reliable. It is important to not confuse the swelling from legs mites with that of bumble foot, which is a larger area swelling, usually of the foot pad.

The larvae have three pairs of legs. After two nymphal stages, the mites mature into adults that have four pairs of legs. The mites burrow into the feather follicles and chomp down to the layer immediately under the main protective skin layer, primarily on the face, feet, and beak cere, where they feed on keratin. Most commonly, the unfeathered regions (beak, eyelids, legs, and vent) are affected. As the mites burrow, they form tunnels.  The process of keratin munching and burrowing damages the underlying tissues of the bird legs. The result is an inflammatory response, which results in dried, crusty fluid loss. The scales and legs swell in size. This results in the typical symptoms.

The mites are transmitted from bird to bird through prolonged close or direct contact. Although the mites are primarily transmitted from parent to unfeathered nestlings, Knemidocoptiasis appears to be more opportunistic than infectious. Unlike many parasitic infections in birds, clinical infestation with Knemidocoptes species occurs more frequently in older birds, however, when the thickened scales are noticed clinically, then this indicates that the mites have been munching away for many weeks to months.  Spread is slow and inexorable when left untreated.

Leg mites are only carried between batches on birds.  They do not tend to live in the environment for a long time. Birds which have hatched naturally under infected parents may be more likely to be infected during this time.  It is always interesting why it takes so long for the infections to get going, but there are many diseases which are quite non-symptomatic in animals until they reach the stress of production.  Infected flocks where there are always multi age birds are likely to remain infected.

Now that we know the life cycle, we can think about treatments.

Treatment Options

Mites can walk from bird to bird, and leg to leg, but only short distances. They are mainly transferred by physical contact. . Therefore, even when one leg looks normal and its mate looks infected; treatment should always assume both legs are infected.  One way in which the cycle commences in birds is through infected older birds contaminating the environment of the younger birds.

Treatment therefore needs to consider the size of the flock, and the severity of infection, and what’s going to happen to the eggs. 

A simple, no egg residues treatment is to apply a barrier cream bandage to impact the life cycle of the mites under the skin. An effective way to do this is to cover the infected zones and prevent air supply to the underlying tissues; like treating a human burn. Clean the area, and apply a barrier cream. Some people advocate products such as Vaseline. I would suggest the use of a poultry barrier butter, such as Allfarms Poultry Leg & Wattle Sealant.  Whatever you use, the principle is to keep the infected scales clean, and to repeat the application several times until the legs start to respond. Inflammation will decrease, and eventually the damaged scales will fall off and be replaced by clean fresh flexible leg scales. The birds should be kept in a clean shavings free area. Work the cream in well, with a soft bristle brush assisting.  Barrier butters have no residues or petrochemicals or insecticides. They rely on acting as a bandage and soaking the tissues with natural vegetable oils of the kind which have been used for many years to treat dry, irritated and damaged skin. If you have many birds infected, then you have a long slow thorough job to complete on each bird. Remember to treat each leg for the first few times. The minimum time for treatment will be three weeks, as any mites which were recently laid need to be treated.  The process of working on the barrier gels also massages the scales and leg circulation and encourages healing by doing so. The softening form the barrier butter oils also means the new scales are flexible. Leg butters are not petroleum based, and are very environmentally and human-user friendly. Preheating them to body temperature makes them easier to apply. Some people have advocated an Epsom salts soak of infected legs prior to treatment. This is a great idea, but the overall rule is to make sure the area is cleaned well.  Barrier products are easily repelled by water, and so if a pre-soak is used, the legs must be perfectly dried, or the barrier products will not adhere. The butter is attracted to dry and oily skin. A very useful supporting treatment is to apply some vitamin E cream, especially when the lesions start to heal.

A fast treatment for leg mites is to apply Ivermectin products – such as those found in a pour on drench. This product is absorbed through the skin, and effectively circulates through the entire bird, where it will diffuse out of the blood vessels and into the skin tissues the mites will be consuming.  The Ivermectin will also happily diffuse into eggs, and it also paralyses gut worms. The product uses solvent carriers to carry the Ivermectin through the skin. , and all three of them can also find themselves inside egg yolks and whites. There is no data on how long the eggs are safe and residue free after this treatment.  The products used are not registered for treatment of poultry producing food and eggs for human consumption.

Other products which can be applied to legs include products containing essential oils. These can be effective, but, the oils and solvents can be quite irritating to the delicate inflamed tissues under the scales.  They can also be quite caustic. Also, a single application will be inadequate.

Outrageous rocks in your head treatments

It is not uncommon to read out there in cyber land ‘treatment’ recommendations which include wiping legs with petrol, WD40, kerosine or other solvent products.  Come on there, would you treat a lesion on your leg with petrol? The base oils will be toxic to the skin, and as they are absorbed into the bird, have potential to be toxic to the liver and kidneys. This treatment is totally unacceptable from a welfare point of view, because it is cruel. This option is included here so that my opinion can be read!

The treatment of scaly leg mite can be done in a way which is kind and gentle to the bird and the skin.  At the same time, try and work out how many birds are infected, and treat the worst ones first. Remember that the more birds you can treat at once, the greater your chance of success.  Birds with both legs looking normal are probably not infected.

Written and Reproduced with permission Dr Grant Richards, Allfarm Animal Health.
Copyright 2018 – Grant Richards