Chicken Parasites: Worms, Mites, and Lice

Author: Elliott Garber, DVM

Most chicken parasites fall into two camps: external ones that live on the skin and feathers (mites and lice), and internal ones that live in the gut or airway (worms). The external parasites are the ones you can catch yourself by parting the feathers and looking, and a dry dust bathing spot is the flock’s own first line of defense against them. Worms are harder to see and are best managed with a fecal test from your vet rather than blind calendar deworming, because dewormer resistance and egg withdrawal both matter. Here is how to find each problem early and what to do about it.

External parasites: what lives on the bird

External parasites are the ones you have the best chance of catching yourself, because they live right on the skin and feathers. On a healthy chicken you should be able to part the feathers and see clean skin. The two spots that fill up first are the vent (the feathered area just below the tail) and under the wings, both warm and sheltered. According to Poultry Extension, northern fowl mites show up as tiny dark specks moving quickly on the skin, often with black, crusty debris on the feathers around the vent.

Northern fowl mite

The northern fowl mite is one of the most common external parasites of backyard flocks in North America, and unlike the red mite it lives on the bird full time, so you can find it in daylight. It feeds on blood, and a heavy load causes anemia (a pale comb and wattles), poor feather quality, reduced feed intake, and a noticeable drop in egg production, per Poultry Extension. It will also bite you and cause itchy skin while you handle infested birds. Because it stays on the host, checking the vent by day is the reliable way to catch it.

Red mite (chicken mite)

The red or roost mite is sneakier. It does not stay on the bird. During the day it hides in cracks and crevices of the coop, in the seams of nest boxes, and under the roosts, then comes out at night to feed, notes the Merck Veterinary Manual. That is why a daytime feather check can come up empty while the birds are still being drained. Signs to watch are pale combs and wattles, listless or restless birds that do not want to go into the coop, weight loss in young birds, and falling egg numbers. To confirm it, go out after dark with a flashlight and inspect the underside of the roosts and the cracks near where the birds sleep. Red mites are hardy and can survive a long time off the bird without feeding, so treating only the birds and not the coop rarely works.

Lice

Poultry lice are chewing lice, not blood feeders, and they spend their whole life on the bird eating skin scales and feather debris. Larger than mites, they may scurry when you part the feathers, alongside clusters of pale eggs (nits) cemented in a hard mass at the base of the feather shaft, often near the vent. Signs include damaged, ragged feathers, agitated birds, and reduced growth or laying in a heavy infestation. Because louse eggs are shielded and resist the first treatment, any louse control has to be repeated a couple of weeks later to catch newly hatched lice, as Poultry Extension describes.

Scaly leg mite

The scaly leg mite is different again. It is a microscopic mite that burrows under the scales of the legs and feet and tunnels in the tissue there. You will not see the mite; you see its damage. Healthy chicken legs have flat, smooth, tidy scales. With scaly leg mite the scales lift, thicken, and crust, so the legs look raised, rough, and swollen. It is rare in commercial houses but not uncommon in backyard and show flocks, and severe, long-standing cases can permanently deform the feet, so catch it early. Because the mite is buried under the scales, treatment usually means smothering it (for example coating the legs thoroughly with petroleum jelly) rather than a feather dust, with the coop and roosts cleaned too. If the legs are badly affected or you are unsure, ask a vet before you start, and never pull at the crusts.

Finding them: the hands-on check

The single most useful habit is a routine hands-on inspection, because most of these problems are invisible from across the run and obvious once you have a bird in hand. In good light, part the feathers around the vent and under the wings and check the skin, the feather bases, and the legs. Watch for the whole cluster of signs together: a pale comb, ragged or damaged feathers, birds that seem restless or reluctant to roost, an unexplained drop in laying, and tiny specks that move. If you suspect red mite and the daytime check is clean, repeat it at night at the roost, the only time red mites are on the bird.

Any check is also a good moment to jot the finding down. Logging it on the bird’s health and medical records in its Creatures profile, or on the whole flock, means you can see patterns over time (which coop, which season, whether the same bird keeps flaring) instead of relying on memory. If you add a record after a treatment, you can set a reminder for the repeat treatment two to three weeks later so the follow-up dose does not slip.

The dust bath: the flock’s own defense

Chickens have a built-in way of keeping external parasites down, and it costs nothing to provide. Given a patch of loose, dry, fine material, a chicken works it deep into its feathers and skin and then shakes it out, and this dusting smothers and dislodges mites and lice. A dry dust bathing area is a genuine first line of prevention, not a nice extra. Birds that cannot dust bathe, because the only loose ground is wet or there is not enough dry space, tend to carry heavier loads.

Give them a dry, sheltered spot with loose soil, sand, or a mix, kept out of the rain. Many keepers add a little food-grade diatomaceous earth to the dust; Poultry Extension notes it can help by damaging the mite’s protective waxy coating, though it does not kill eggs and is not a complete fix on its own. Keep any dusty product away from your and the birds’ airways. The dust bath pairs with the rest of coop hygiene: dry bedding, regular cleanouts, and clearing the cracks and crevices where red mites hide. Your coop setup and cleaning routine does a lot of the parasite prevention work for you.

Internal parasites: worms

Worms live inside the bird, so you almost never see them directly, and this is exactly why they should be managed with a test rather than by guessing.

Low worm burdens are common in birds with outdoor access and usually cause no visible problem. It is high burdens that matter, and the signs are non-specific: poor condition, weight loss, pale comb from anemia, loose droppings, and reduced laying, per the Merck Veterinary Manual. Those same signs come from many other problems, which is another reason to test rather than assume worms. The three worth knowing are:

• Large roundworm (Ascaridia). The most significant roundworm of backyard flocks, roughly the thickness of a pencil lead and up to several inches long, living in the small intestine. Heavy loads reduce nutrient absorption and, at the extreme, can block the gut, according to Poultry Extension. Eggs pass in the droppings and infect other birds through contaminated ground, feed, or water.
• Cecal worm (Heterakis). Lives in the ceca and usually does little direct harm to the chicken itself. Its importance is indirect: it can carry the organism that causes blackhead (histomoniasis), which is severe in turkeys, so it matters most in mixed chicken and turkey flocks, notes Poultry Extension.
• Gapeworm (Syngamus trachea). Different from the others because it lives in the windpipe and airway, not the gut. It causes gaping: open-mouthed breathing, gasping, head-shaking, and a stretched-out neck as the bird tries to clear the airway, per the Merck Veterinary Manual. Because those are respiratory signs, gapeworm can be mistaken for respiratory disease. If a bird is struggling to breathe, that is a call-the-vet situation regardless of the cause.

Test first, do not deworm blindly

The dependable way to know whether worms are actually a problem is a fecal test. Many veterinary clinics run a fecal exam that looks for worm eggs under the microscope and gives a rough measure of the burden, which tells you whether treatment is even warranted. Penn State Extension lays out two approaches: deworm on a fixed calendar, or deworm only when a test shows a high burden. For most small flocks the test-guided approach is the better default.

There are two reasons routine calendar deworming has fallen out of favor. First, resistance: worms exposed to the same dewormer over and over can stop responding to it, and unnecessary treatment speeds that up, which is why a fecal egg count reduction test (a count before treatment and a second one one to two weeks after) checks whether a dewormer still works. Second, egg withdrawal: many dewormers require you to discard eggs for a set period after treatment because residue can pass into the eggs, and approvals for laying hens are limited. In the United States, per Penn State Extension, fenbendazole (a water-soluble product for chickens) is the FDA-approved dewormer for roundworms and cecal worms, with its egg withdrawal defined by the label. Any other product, or off-label use, is a decision for your vet, who will tell you the correct withdrawal period.

The practical rule: do not reach for a dewormer just because the calendar says so. Get a fecal test, treat only if warranted, use the right product at the right dose (your vet’s call, not a home guess), and follow the egg withdrawal to the day. Log the treatment and the withdrawal end date on the bird’s profile records so you know exactly when eggs are safe to eat again.

What about coccidiosis?

Coccidiosis is caused by a single-celled intestinal parasite (Eimeria), not a worm or a mite, and it hits young birds hardest. It is primarily a chick and grower issue, showing up as lethargy, huddling, poor growth, and sometimes bloody droppings, and it can move fast in a brooder. Because it belongs to the early rearing stage, it is covered in the raising baby chicks guide rather than here. Young birds going downhill quickly with bloody droppings are an urgent, call-the-vet situation.

When to call a vet

Parasites shade into other illness quickly, so know the line. Call a vet if a bird is struggling to breathe or gaping, if you see blood in the droppings, if a bird is severely anemic (very pale, weak, collapsed), if worming does not resolve the signs, or if you are unsure what you are looking at. A vet can run the fecal test, confirm the parasite, prescribe the right product, and give you the correct dosing and egg withdrawal, none of which should be guessed at home. For the wider picture of what else these signs can mean, see the chicken illnesses guide.

Frequently asked questions

How do I check my chickens for mites?

Pick the bird up in good light and part the feathers around the vent and under the wings to look at the skin. Watch for tiny fast-moving specks, black crusty debris on the feathers, and clusters of pale eggs cemented at the base of the feather shafts. For red mite, which hides in the coop by day, do the check at night at the roost when the mites come out to feed.

What are the signs of parasites in chickens?

Common signs include a pale comb and wattles, ragged or damaged feathers, restlessness and reluctance to roost, an unexplained drop in laying, and visible specks moving on the skin. Raised, crusty leg scales point to scaly leg mite. Open-mouthed gasping and head-shaking can indicate gapeworm and needs a vet.

Should I deworm my chickens on a schedule?

Usually not blindly. The better default for most small flocks is a fecal test to see whether worms are actually present in numbers worth treating. Routine calendar deworming can drive dewormer resistance and ignores egg withdrawal. Test first, treat only if warranted, and follow the label or your vet on the egg withdrawal period.

Is diatomaceous earth enough to control mites?

It can help as part of a dust bath by damaging the mite’s waxy coating, but it does not kill eggs and is not a complete treatment on its own. Pair it with a good dry dust bathing area, coop hygiene that clears the cracks where red mites hide, and a proper insecticide treatment (repeated to catch newly hatched parasites) for an active infestation.

Do I have to throw out eggs after deworming?

Often yes. Many dewormers require an egg withdrawal period during which eggs must be discarded, and approvals for laying hens are limited. The exact period depends on the product and how it is used, so follow the product label or your vet, and note the date eggs become safe again so you do not lose track.

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