Chicken Roundworms: Ascarid Infection Symptoms and Treatment
- Chicken roundworms usually refers to Ascaridia galli, the most common intestinal roundworm in chickens. It lives in the small intestine and spreads when birds swallow infective eggs from contaminated litter, soil, feed, or water.
- Mild infections may cause no obvious signs. Heavier burdens can lead to poor growth, weight loss, diarrhea, dull feathers, reduced appetite, lower egg production, and in severe cases intestinal blockage or death.
- Diagnosis is usually made with a fecal exam for parasite eggs, although your vet may also recommend necropsy of a deceased bird or flock-level testing if several birds are affected.
- Treatment often involves a vet-guided deworming plan plus coop sanitation and repeat monitoring, because birds can become reinfected from the environment.
- Typical 2025-2026 U.S. cost range for exam, fecal testing, and basic deworming guidance is about $80-$250 for a backyard chicken case, with higher costs if multiple birds, lab work, or complications are involved.
What Is Chicken Roundworms?
Chicken roundworms are intestinal parasites, most commonly Ascaridia galli, that live in the small intestine of chickens. This is the most common helminth infection reported in poultry and is seen in backyard flocks as well as larger operations. Birds pick up infection by swallowing parasite eggs from contaminated droppings, litter, soil, feeders, or water sources.
Some chickens carry a light worm burden with few outward signs. Others, especially young birds or flocks with repeated exposure, can become thin, slow-growing, less active, and less productive. Heavy infections can irritate the gut and, in severe cases, physically block the intestine.
Roundworms are frustrating because the environment can stay contaminated for a long time. Even after treatment, birds may be reinfected if bedding, run conditions, and manure management are not addressed. That is why your vet will usually think about the whole flock and the housing setup, not only one chicken.
Symptoms of Chicken Roundworms
- Poor growth or failure to gain weight
- Weight loss or thin body condition
- Reduced appetite or depressed activity
- Diarrhea or loose droppings
- Decreased egg production
- Visible worms or worms found in eggs
- Weakness, marked depression, or sudden decline
- Signs of intestinal blockage
Roundworm signs are often vague at first, so a chicken may look "off" before the problem is obvious. Weight loss, poor growth, and lower egg production are common clues, but they can also happen with coccidiosis, bacterial disease, nutrition problems, or other parasites.
See your vet immediately if your chicken is very weak, stops eating, has severe diarrhea, seems painful or bloated, or if multiple birds are declining at once. Those signs can mean a heavy parasite burden or another serious flock problem that needs prompt diagnosis.
What Causes Chicken Roundworms?
Roundworms spread through the fecal-oral route. Infected chickens pass parasite eggs in their droppings, and other birds become infected when they peck at contaminated litter, soil, feed, water, or surfaces. Ascaridia galli has a direct life cycle, so it does not need another animal host to keep spreading in a flock.
Backyard settings can make reinfection easier. Dirt runs, damp bedding, crowding, mixed-age flocks, and poor manure cleanup all increase exposure. Young birds are often hit harder because they have less immunity and may carry heavier worm burdens.
Wild birds, new flock additions, and shared equipment can also bring parasite eggs onto the property. Even a well-loved flock can develop worms over time, especially if birds spend a lot of time on the same ground. That is why prevention focuses on both parasite control and day-to-day flock hygiene.
How Is Chicken Roundworms Diagnosed?
Diagnosis usually starts with a physical exam and a review of flock history. Your vet may ask about age of the birds, housing, recent additions to the flock, egg production changes, weight loss, and whether birds are kept on litter or dirt. Because roundworm signs are not specific, testing matters.
The most common test is a fecal flotation or fecal parasite exam to look for roundworm eggs. This can be done on an individual bird or as a pooled flock sample, depending on the situation. A negative test does not always rule worms out, especially early in infection or with intermittent shedding, so your vet may recommend repeat testing if suspicion stays high.
If a bird dies, necropsy can be very helpful. Adult Ascaridia galli may be seen in the small intestine, and that can confirm the diagnosis while also checking for other diseases affecting the flock. Your vet may also consider coccidiosis, capillaria, bacterial enteritis, nutrition issues, or reproductive disease if the signs overlap.
Treatment Options for Chicken Roundworms
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Office or farm-call consultation focused on the affected bird or small flock
- Fecal flotation or pooled fecal parasite testing
- Vet-guided deworming plan using an FDA-approved poultry option when appropriate
- Basic coop sanitation plan: manure removal, dry bedding, feeder and waterer cleaning
- Instructions for monitoring appetite, weight, droppings, and egg production
Recommended Standard Treatment
- Full veterinary exam and flock history review
- Individual or pooled fecal testing, with repeat testing if needed
- Targeted deworming plan, commonly using fenbendazole products labeled for poultry when appropriate and used according to your vet's guidance
- Written flock-level control plan for bedding, stocking density, rotation, and quarantine of new birds
- Follow-up recheck or repeat fecal exam to confirm response
Advanced / Critical Care
- Expanded diagnostics for birds with severe illness, poor response, or multiple flock losses
- Necropsy and laboratory submission for deceased birds
- Supportive care for dehydrated or debilitated chickens, such as fluids, nutritional support, and hospitalization when available
- Evaluation for concurrent disease such as coccidiosis, bacterial enteritis, or management-related illness
- Detailed flock outbreak plan with staged retesting and biosecurity changes
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Chicken Roundworms
Bring these questions to your vet appointment to get the most out of your visit.
- Does my chicken need an individual fecal test, or would a pooled flock sample make more sense?
- Based on my flock setup, how likely is reinfection after treatment?
- Which deworming option is appropriate for my chickens, and are there egg or meat withdrawal instructions I need to follow?
- Should I treat one bird, several birds, or the whole flock?
- What other conditions could look like roundworms in chickens?
- When should we repeat fecal testing to make sure the treatment plan worked?
- What coop cleaning steps matter most for reducing parasite eggs in my setup?
- Do my young birds, new additions, or birds on dirt runs need a different prevention plan?
How to Prevent Chicken Roundworms
Prevention starts with reducing contact between chickens and contaminated droppings. Clean manure often, keep bedding dry, and scrub feeders and waterers regularly so birds are less likely to swallow infective eggs. If possible, avoid overcrowding and give birds access to clean, well-managed ground rather than wet, heavily soiled areas.
Quarantine new birds before adding them to the flock, and talk with your vet about whether screening fecal samples makes sense for your setup. Mixed-age flocks can increase parasite pressure, because older birds may shed eggs while younger birds are more vulnerable to illness.
Routine deworming without a diagnosis is not always the best plan. A better long-term approach is monitoring plus management: watch body condition, growth, droppings, and egg production, then use fecal testing and treatment when your vet recommends it. That approach helps match care to the flock's real risk while supporting responsible drug use.
If your chickens produce eggs for your household, always ask your vet about product labeling and any withdrawal guidance before treatment. In the U.S., fenbendazole is the FDA-approved deworming option commonly referenced for treatment and control of roundworms in chickens when used according to label directions.