There are two types of parasite – the ones that live on the birds’ skin and feathers (ectoparasites - mites, lice and fleas), and the ones that live inside (endoparasites - worms).
Mites are commonest in hot weather, but will also linger in smaller numbers through the winter. Signs of infestation include feather loss, poor egg production, and restless hens scratching and feather-ruffling. If left untreated, a mite infestation can result in anemia due to blood loss. One mite is tiny, but thousands of them together can suck a lot of blood from a hen! An anemic bird can be told by her pale comb and general listlessness.
The mites themselves are very small, and not immediately obvious to the naked eye. They are nocturnal, which adds to their stealth. An individual mite lives no longer than 10 days, but during that time a female can produce 100,000 eggs, and they hatch in 10 to 12 days.
Roosting poles are a favorite hiding place of Red Mite
Note: if the hens are being treated with an anti-parasite spray or powder, the eggs they lay over the next seven days should not be eaten.
Red Mite (also known as Chicken Mite) (Dermanyssus gallinae)
These are grey and red creatures up to 0.7mm. They will infest the chicken from head to toe, with concentrations around the vent. They often arrive on wild birds and take up residence in nooks and crannies, and on the underside of roosting poles.
Unfortunately there is no effective natural remedy. The mites are taking advantage of what is essentially an artificial set up – a bunch of birds living in a house together! There are various anti-mite powders and liquids available. These should be applied in the coop at the first sign of the creatures, or in spring (and once a month after that) as a preventative measure. Infested birds should be treated individually, according to the instructions on the product.
During treatment the birds’ water should be supplemented with a multivitamin preparation to assist their full recovery.
A disinfectant may be necessary if the infestation has been severe. Always throw way bedding and scrub the hen house thoroughly.
Northern Fowl Mite (Ornithonyssus bursae)
At 1mm in length, this is slightly bigger than the Red mite, but still tiny nonetheless. These mites are pale grey or black/brown (depending on how much blood they have sucked). They cluster around the base of the chicken's feathers, mainly around the vent.
Unlike Red Mites, Northern Fowl Mites live on the birds, and don’t hide in dark corners during the day. Treatment consists of applying remedy preparations to the bird itself.
Mite infested hens
Scaly Leg Mite (Knemidocoptes mutans)
This is commoner on older hens. It burrows beneath the scales of the bird’s leg, causing raised scales, crusting and tissue fluid seepage. These areas can easily become infected.
The problem only becomes visible after several weeks of infestation. An antibacterial scaly-leg treatment will clear up the problem, but the symptoms take several months (up to a year) to disappear.
Rubbing Vaseline onto the treated legs will help soften the scales and suffocate any surviving mites. The treatment needs to be repeated every few weeks.
Depluming Mite (Knemidocoptes gallinae)
A close relative of the Scaly Leg Mite, this one burrows into a chicken’s feather shafts. It tends to cluster around the head, neck, back, belly and upper legs.
Affected birds will show signs of general discomfort. The affected areas will ooze tissue fluid, upon which the mites feed. The hens will start to pluck feathers in an attempt to relieve the discomfort.
The mites spread via contact with other birds. Their young are born live, so one treatment with an appropriate preparation will destroy all the mites. The hen house and the bird should be treated.
Lice (Menophon gallinae)
Lice are yellow-brown, and can reach 3mm (1/10”) in length. The creatures and their tiny eggs (nits) cluster around the vent, under the wings and at the base of feathers. They only live a few days, but spread very quickly from bird to bird.
Louse numbers peak in Fall and Winter. Chickens and coop alike should be treated with an appropriate preparation.
There are two types of flea that can infest chickens - European Chicken Flea (aka Hen Flea or Sticktight Flea, Ceratophyllus gallinae), and the Western Chicken Flea (or Black Hen Flea, Ceratophyllus niger). Although not as common as mites and lice, once they’ve moved into your coop, their numbers explode (and the ones you see are just 5% of the true numbers, with the other 95% still inside their tiny eggs). The biggest danger of an outbreak is in the Summer. Hundreds of flea bites can cause anemia in chickens, manifesting in lethargy, irritability, restlessness, and skin-pecking/scratching. Egg production will also drop.
Fleas can be treated with chemical sprays; but there are more organic solutions too. A garlic or cider vinegar spray may help, applied to chicken coops and litter. Some owners put whole cloves in the water supply to deter the pests too. Mint is another deterrent, and can be grown easily in the places where your chickens roam. Application of Food Grade Diatomaceous Earth (a natural, silica-rich algae powder), according to instructions, will also help.
Fowl Tick (Argas persicus)
Ticks proliferate in warm, dry weather, and will eagerly attach themselves to any passing poultry, given a chance. There is not much you can do to eliminate them in the wilder parts of the garden. However, the presence of chickens is a good start as hens will forage for any creep-crawly, and a fat tick is a delicacy they will relish. But once one is attached, your birds are in danger of becoming diseased.
A hen infected by a tick (and they are carriers of various diseases) will show all the usual symptoms of avian illness - listlessness, a drooping posture, pale crown and wattles, and a drop in egg production. A hand examination of the bird will usually spot the culprit, which can be prised off using special tick-removal tweezers.
If ticks have been spotted, the walls, ceilings, nooks and crannies of a hen coop should be treated with a suitable tick-deterrent. All cracks and crevices should be checked and, if possible, filled in to prevent the beasties hiding away. Although huge and very visible once they've swollen up with blood, the ticks are surprisingly small and hard to spot pre-suck. But if you carry out prevention indoors, and let the hens mop up the blood-suckers outdoors, you will have done the best you can.