Flock health

Worms in Backyard Chickens: Types, Signs, Fecal Tests and Egg Withdrawal

Field guide · Updated October 28, 2026 · about 8 min read

Hens that scratch outdoors meet worms sooner or later: Maryland Extension's FS-999 says free-range birds will likely encounter parasites at some point. Penn State notes that a few worms typically cause no clinical problems; heavy burdens do. This page covers the five worms extension services name, how to confirm them, how to cut reinfection and what the label rules mean for your eggs.

Short version: the usual suspects are large roundworms, cecal worms, capillaria (hair or crop worms), gapeworms and tapeworms. Their signs are not specific, so have a vet or lab examine fresh droppings before treating. Keep litter dry and birds off worn ground. Use any dewormer exactly as labeled; anything else needs a vet's prescription and a withdrawal time set by that vet. HenClass gives no doses.

The five worms extension services name

Housing matters for tapeworms: Jacob notes that birds on litter mainly get termite- and beetle-borne ones, and free-range birds snail- and earthworm-borne ones. Coccidia, the other common gut parasites, are protozoa rather than worms (Jacob); see the glossary.

Signs, and why they are not enough

Penn State lists diarrhea, depression, reduced weight gain, weight loss, anemia, worms in eggs and fewer eggs as signs of a high worm burden, and stresses that these signs are not specific to worms. LSU AgCenter adds worms visible in droppings, poor appetite and feather loss.

• Gapeworm: open-mouth breathing, neck stretching, head shaking and gasping (LSU); coughing and wheezing (Maine). Breathing trouble has other causes; see the hen health check for signs to report.
• A worm inside an egg: roundworms can migrate up the oviduct into an egg. Merck calls it an aesthetic problem that candling catches; FS-999 says it is rare and that avian internal parasites pose no risk to people.

Confirming worms: a fecal test through a vet or lab

Penn State says a definitive diagnosis takes a microscopic exam of the droppings for worm eggs or larvae, which a veterinary clinic or diagnostic lab can do. Merck adds the limits: flotation or sedimentation shows that worms are present but usually not which species, and a negative result does not rule them out, because eggs are shed intermittently. For gapeworms, Maine Extension also suggests shining a flashlight through the thin skin of the neck in a dark room to see the worms in the trachea.

The Maryland Department of Agriculture's Animal Health Laboratory offers three tests and suggests asking a vet which fits:

Collecting a sample

1. Call first and ask which test to request and how much sample to send; Maryland's lab asks for at least 8 grams.
2. Collect fresh droppings right after they are passed; eggs can hatch within hours or days (Maryland).
3. Use a spill-proof container. Maryland may reject samples sent in gloves or zip-lock bags.
4. Refrigerate at once; do not freeze. Ship with ice packs (Maryland).
5. Label and fill in the form with the test requested, then deliver it as soon as possible (Maryland).

Treatment: what the label rules say

Work out the worm before choosing a product: Maine Extension reminds owners that "not all wormers kill all worms." Approved options for chickens are few:

• One approved active ingredient. Penn State (2026) says fenbendazole is the only product currently approved in the US for roundworms and cecal worms in chickens and turkeys; Merck also names only fenbendazole for chickens. Its approval for backyard flocks, laying hens included, was announced in November 2024 (dvm360).
• No approved product for tapeworms (Penn State; FS-999), and FS-999 says no drug is approved for commercial use against gapeworms.
• Older guides are out of date. FS-999 (2014) names piperazine; Penn State says it is no longer available for poultry in the US.
• Off-label means a prescription. Penn State says any use that differs from the label, whether another species, dose or duration, needs a prescription from a licensed veterinarian.

Eggs during and after treatment

A FARAD review in JAVMA (2015) says FDA "considers all chickens to be food-producing animals, regardless of whether owners consider their chickens pets," and explains that drugs given to a hen reach the developing yolks and stay sequestered there.

FS-999 notes that a product's withdrawal time can differ for eggs and meat. FDA's T.A.L.K. reminder sums up the routine: talk to your veterinarian, ask whether the drug is FDA-approved, look at the label, and keep complete treatment records.

Prevention checklist

• Keep litter dry and clean, along with feeders and waterers (LSU). Poorly managed built-up litter favors intermediate hosts and infective eggs (Merck); see coop bedding and litter.
• Move birds off worn ground. Birds on the same ground face more worms than birds rotated to fresh ground several times a year (LSU), though Merck says the benefit is short-lived.
• Avoid bare, muddy runs. Maine suggests a sand or concrete layer in the henyard, and moving a chicken tractor often enough that birds never stand on bare or muddy ground.
• Feed from feeders, not scattered on the ground, and avoid wet, muddy areas (LSU).
• Keep wild birds out with netting and overhead covers (Maine).
• Target intermediate hosts. Tapeworm control depends on the right host (Jacob). Merck describes approved insecticides applied to soil and litter while the house is empty.
• Keep turkeys apart. Do not house or range turkeys with chickens or where chickens recently were (Jacob), because cecal worms carry blackhead.
• Don't overcrowd, and quarantine newcomers; see adding new chickens.

Worm eggs persist for long periods and resist common disinfectants (Penn State).

Routine deworming or test first?

Penn State describes two approaches, deworming on a schedule or only when the burden is high, depending on flock size, coop or pasture housing and the flock's history. Merck advises limiting treatment to birds with severe infestations and clinical signs, to slow resistance. A fecal test gives you and your vet the evidence. For external parasites such as lice and mites, see mites and lice.

HenClass summarizes official guidance and does not give veterinary advice or doses. Follow your veterinarian and the label on any product used on poultry.