This fact sheet is designed to improve the understanding of Poultry Louse infections in poultry and the variety of treatment options available.
POULTRY LOUSE LIFECYCLE
In order to fully discuss treatment options for the treatment of lice, it is important to make the correct diagnosis and understand the life cycle.
Be confident to not confuse poultry lice infections with mite infections. Scaly Leg Mites infect legs and cause the well known knobbly scales. Other species of mites infect beak ceres in parrots. you generally only know if these mites are present from examining the symptoms. There are also mites which live off the bird and use poultry as a mobile cafeteria and suck blood during the nights, so they are not usually visible during the day time. These poultry mites are pin sized. Generally, lice are easily visible and live on the bird in a number of locations depending on the species.
Lice only have a life cycle on the bird and can be found easily. They lay eggs on the bird, and these leave tell tale signs present as fans of eggs (nits) on the base of the feather shafts. This information sheet will confine it’s comments to lice. The important message is to be able to identify which ectoparasite you are dealing with…
There are a number of lice species on birds, with the main group being classified as ‘Mallophaga’. Lice are light sensitive and scurry away when the feathers are parted. Young lice are pin head size and white, while adult lice are usually a brown colour. Areas to look for lice are under the wing, around the parsons nose and around the feathers below the cloaca. Lice are transmitted between birds by direct contact. There is no part of the life cycle away from the birds. Eggs hatch within a few days, and the eggs are usually visible in chronic infections as fans of eggs, particularly under the wing.
It is important to understand they key difference between mites and lice. The main reason is because the treatment options can be quite different.
Knemidocoptes species mites (also written as Cnemidocoptes) 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 leg mites of that of bumble foot, which is a larger area swelling, usually of the foot pad.
Lice lay eggs on the bird (not under the skin as with mites). The life cycle of a louse takes around 7 days from hatching to a visible louse which can be easily detected on a bird. The lice chomp down to the layer immediately under the main protective skin layer and in those areas of the bird where they are comfortable. A louse found on the back of a head can be a different species to one found under the tail feathers. The process of skin munching and foraging damages the underlying tissues. The result is an inflammatory response can result in dried, crusty fluid loss. Birds become irritated and preen and worry the areas where they are itching. This breaks the feather shafts and results in the typical symptoms – bald birds with rough feathers. These birds are unable to keep warm and production drops are inevitable in colder weather.
The lice are transmitted from bird to bird prolonged close or direct contact. Lice are most active in winter time. In summer, and especially when birds dust bathe, the lice escape up the feather shafts and hold on with special claws. They can be difficult to spot so, if looking for lice in summer, always check the feathers and do this in a well lit area. I have been fooled numerous times. The second message is to check birds regularly, and check a reasonable number in a flock. Lice never infect 100% of birds at the same time. They spread slowly.
Lice are 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. Infected flocks where there are always multi-aged birds are likely to remain infected. Lice are mainly transferred by physical contact. 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 is going to happen to the eggs. It is not uncommon to find birds which are heavily infected with ones which you can not find lice on. This is simply a result of the direct contact way lice are transmitted. It is a numbers game. The point here is always check at least 10 birds in a flock before you declare yourself louse free.
Choosing Louse Treatments
Dusting powders are favoured for small bird groups. A popular choice is diatomaceous earth (DE). There are some very bad videos on You-Tube using DE treatments, so read the following carefully. The rule is to apply the powder where the lice are, and never to randomly poof some powder under wings. Thorough coverage with powders is always indicated, as is rubbing the powder into the skin. This method ensures gently and thorough treatment of all birds, and is as easy as applying flea powder. If the application is not done thoroughly, the lice simply relocate and come back home when the powder residues have disappeared.
You can also add some treatment powders as dust baths, so the birds spread the dust over themselves. You need to keep this level of treatment up, so regular maintenance of baths is important. Place the baths in sunny spots where the birds will not be tempted to thing the powdery havens are for laying eggs. This method needs to be monitored, as not all birds will use the dust baths, and there needs to be enough of them to ensure that all birds take a bath. This method suits larger numbers birds numbers. Providing sulphur supplements has also been demonstrated to assist with louse number management.
There are popular dusting powders which contain active insecticides, such as rotenone. Pestene powder is a good example. Rotenone (the active ingredient, also known as Derris Dust) has been banned in some countries. Generally insecticides kill very quickly.
New Generation Louse Powders
One recently patented new generation powder uses elemental sulphur and rhizome unextracted essential oil combination. Research has shown this to be highly effective in killing over 95% of lice within 48 hours when applied thoroughly to a heavily infested bird. Safe to use on birds of all ages, there are no known impact from residues. A repeat application is really important. Be sure that any organic products you use are backed up by research data and they are not detrimental to the bird.
Liquid Louse Sprays
These often contain insecticides (eg. malathion) or extracted or distilled essential oils. As a choice you should use louse sprays that kill. Some essential oils can be caustic to skin when used at concentrations which inhibit the lice. The oils, usually purchased as a concentrate, and carriers can be severe on nostrils and eyes. They can also only be louse repellents and the lice use the relocation principle and return quickly. Never use sprays when wet birds can be easily chilled post treatment as this will trigger respiratory diseases – which are far worse than lice infections! Spraying products onto bird feather surfaces is usually quite ineffective and will usually only give a knock down. They are generally not effective against the lice eggs (nits). Sprays are often short acting. There are also washes that can be used to immerse the total bird. Once again the penetration of the active ingredient needs to be thorough and the bird must not be chilled whilst drying.
Longer term single treatments for lice
Generally these are ivermectin products – essentially a low volume liquid louse treatment, usually present as 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 lice (and also mites) will be consuming. The ivermectin will also happily diffuse into eggs and 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 egg whites. There is no data on how long the eggs are safe and residue free after this period. The products used are not registered for treatment of poultry producing food and eggs for human consumption. These drenches are registered only for birds which do not produce products for human consumption. Off label use can only be prescribed by a veterinarian. These options are attractive because they reduce the need to re-treat as the produce remains active for longer than it takes for eggs to hatch, meaning there is sufficient active ingredient remaining in the bird skin (food source for lice) to kill the lice.
Whatever product you use, the principle is to repeat the application several times until the population declines. Have a check and re-treat policy. You also need to be aware that most treatments do not stop the nits from hatching. The incubation time for eggs is about a week, so it is a very good idea to repeat applications at this time limit. A single knock down can never be relied on. As the lice numbers decrease, inflammation will decrease and eventually the damaged skin will heal. When the adult population is controlled, there is reduced scratching. Some formulations assist healing. As an aside, if you can see signs of scaly leg mite, use an organic wax and oil barrier butter (Allfarm Barrier Butter – Poultry Leg & Wattle Sealant) to treat at the same time.Use the same product to improve wattle skin lustre and reverse dryness.
If you have many birds infected, then you have a long, slow and thorough job to complete on each bird. The minimum time for treatment will be two applications over three weeks, as any lice eggs which were recently laid need to be treated. Lice treatments 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. Always monitor the success of your treamtnent. Remember that the more birds you can treat at once, the greater your chance of success. Remember that the total site depopulation and suitable hygiene measures will eliminate lice and mites. However, incoming birds need to be louse free. Free range birds can be exposed to wild birds, which can carry lice and mites which can infect all poultry. Therefore, early detection by regular inspection is an important factor for control. Lice are not serious but can exert a significant impact on bird health longer term.
I cringe when I easily see lice in show birds, knowing that it is an easy to give birds a louse reduction treatment prior to showing. The opposite to this is that when showing birds, your own birds can be in the position to pick up fresh lice infections.
Efficient louse management and control is an important factor in all ectoparasite programs. Given that this parasite is quite easy to eliminate or reduce to low levels, they should be difficult to find in any well managed flock.
Written and Reproduced with permission Dr Grant Richards, Allfarm Animal Health.
Copyright 2018 – Grant Richards