6 Chicken Illnesses Every Backyard Keeper Should Know About

6 Chicken Illnesses Every Backyard Keeper Should Know About

One of the harder parts of keeping backyard chickens is that they're really good at hiding when something is wrong. By the time a chicken is visibly sick, sitting puffed up in the corner, not eating, not moving- things have usually been off for a while. Chickens instinctively mask illness because in the wild, showing weakness attracts predators.

That's why knowing what to look for before things get serious is one of the most valuable things you can do as a keeper. You don't need a veterinary degree. You just need to know the most common problems, what they look like early, and what to do when you spot them.

Here are six illnesses that come up again and again in backyard flocks from what causes them, what to watch for, and how to handle them.

1. Coccidiosis (Cocci) — Treated with Corid

Coccidiosis is one of the most common illnesses in backyard chickens, especially in young birds and new chicks. It's caused by a microscopic intestinal parasite called coccidia that lives in the soil. Chickens pick it up by pecking at contaminated ground, and in small amounts, exposure actually helps them build immunity over time. The problem is when they're overwhelmed by it — usually when young birds encounter a heavy load before their immune systems are ready, or when wet, overcrowded conditions let the parasite multiply out of control.

What causes it:

  • Wet or damp coop conditions that allow coccidia to thrive in the bedding and soil
  • Young chicks being exposed before they've built immunity
  • Overcrowding or poor ventilation
  • New birds introduced without quarantine

What to watch for:

  • Bloody or very watery diarrhea — this is the most telling sign
  • Lethargy and hunched posture
  • Pale comb and wattles
  • Sudden weight loss or stunted growth in young birds
  • Loss of appetite

What to do: Corid (amprolium) is the go-to treatment and it's available at most feed stores without a prescription. Mix it into the flock's drinking water at the dosage listed on the label and treat all birds in the coop — not just the ones that look sick, because cocci spreads fast and others are likely already exposed. Treatment typically runs five to seven days. While birds are sick, keep the coop as dry as possible, replace wet bedding immediately, and clean and disinfect waterers daily. After treatment, a probiotic in the water can help restore gut health.

Prevention is straightforward: keep moisture out of the coop, don't overcrowd birds, and if you're starting with baby chicks, using medicated chick starter feed gives them built-in protection during the most vulnerable weeks.

2. Mites and Lice

Mites and lice are external parasites, and nearly every backyard flock deals with them at some point. They're not a sign of neglect — they can come in on wild birds, on new chickens you've introduced, or even on your shoes and clothing. The difference between the two: lice live on the bird's skin and feathers full-time, while certain mites (like the red roost mite) actually live in the coop and only get on birds at night to feed.

What causes it:

  • Wild birds landing in or near the coop
  • New birds added without quarantine or inspection
  • Cluttered coop with lots of hiding places for roost mites
  • Warm, humid weather, which accelerates reproduction

What to watch for:

  • Feathers that look raggedy, broken, or missing — especially around the vent area, neck, and under wings
  • Restless behavior at night, birds not wanting to go into the coop
  • Pale comb and reduced egg production in laying hens
  • Small brown or red specks in the coop or on roosts (mites)
  • Actual lice visible at the base of feathers near the vent

What to do: Check the base of feathers near the vent regularly — that's where both lice and mites like to congregate. For treatment, pyrethrin-based poultry dust or spray applied directly to the birds is effective and safe. Pay special attention to under the wings and around the vent. For red roost mites specifically, treat the birds AND the coop — scrub roosts, replace bedding, and apply mite powder or spray to every crack and corner since that's where they hide during the day.

Diatomaceous earth (food-grade) sprinkled into dust bathing areas can help prevent and manage mild infestations — chickens that have access to a regular dust bath naturally keep their external parasite load lower.

3. Internal Worms (Intestinal Parasites)

Worms are a common reality of ground-based chicken keeping. Chickens peck around in the soil all day, and soil is where most internal parasites live and cycle. Roundworms and tapeworms are the most common. A small worm burden is normal and manageable — it becomes a health problem when the load gets heavy enough to interfere with nutrient absorption and cause real decline.

What causes it:

  • Foraging in soil contaminated by fecal matter
  • Earthworms and insects acting as intermediate hosts (especially for tapeworms)
  • Wet, poorly draining areas where worm eggs persist in the ground
  • Overcrowded runs that don't allow soil to rest and recover

What to watch for:

  • Weight loss despite eating normally
  • Diarrhea or loose, pale droppings
  • Dull, unkempt feathers
  • Drop in egg production
  • Lethargy or general unthriftiness that doesn't respond to other treatments

What to do: The most reliable approach is a fecal float test done by your vet — it identifies what type of parasite you're dealing with and how heavy the burden is. For treatment, fenbendazole (often sold as Safeguard goat wormer) is the most widely used option for backyard flocks, but check with your vet on dosing since it's used off-label in chickens. Give your run a rest periodically if possible — moving a portable run to fresh ground or leaving a section untreated for a season allows parasite eggs to die off naturally.

4. Sour Crop

The crop is the first part of a chicken's digestive system — a small pouch in the chest that stores food before it moves into the digestive tract. Sour crop happens when the crop doesn't empty properly and the food inside starts to ferment, allowing yeast and bacteria to grow. You'll know it when you feel it — the crop will be soft and squishy (like a water balloon), and if you gently smell near the bird's beak, there's often a distinctly sour or yeasty odor.

What causes it:

  • Long grass or fibrous material that gets impacted and slows crop emptying
  • Disrupted gut flora (often after antibiotic treatment)
  • Eating moldy or spoiled feed
  • Stress or sudden diet changes

What to watch for:

  • A soft, squishy, fluid-filled crop that doesn't empty overnight (a normal crop should be empty or nearly empty first thing in the morning)
  • Sour smell coming from the bird's mouth
  • Lethargy and loss of appetite
  • Weight loss over time if left untreated

What to do:

A word first on a method that circulates online: holding the chicken upside down and massaging the crop to force the contents out. This is actually dangerous and shouldn't be done. Chickens don't have a gag reflex and can't vomit — attempting to force material out this way can cause them to aspirate fluid into their lungs and choke.

Here's a treatment approach that works (from personal experience):

  1. Isolate the bird in a quiet, cool, dry space away from the rest of the flock
  2. Restrict food and water for 24 hours — this gives the crop time to empty naturally on its own schedule
  3. After 24 hours, offer plain whole-milk Greek yogurt and fresh water with a small splash of raw apple cider vinegar (about a teaspoon per cup of water). The probiotics in the yogurt help rebalance the yeast overgrowth, and the ACV creates a slightly acidic environment that discourages further yeast growth. Feed this for the next 24 hours
  4. On day three, begin mixing a small amount of her regular feed back in with the yogurt. Keep the water with ACV going
  5. Let her rest and recover before returning her to the flock — give it 72 to 96 hours total before reintroduction so she has fully stabilized

Most birds respond well to this approach within the first 48 hours. If the crop remains full and squishy after 48 to 72 hours with no improvement, a vet visit is warranted. Severe cases can require antifungal treatment.

5. Bumblefoot

Bumblefoot is a bacterial infection of the foot pad, and it's one of those things that can go from minor to serious without a lot of visible warning. It starts as a small cut, scrape, or splinter entry point on the bottom of the foot. Bacteria enter, an infection develops, and the foot begins to form a hard, black scab over an abscess. Left untreated, it can spread into the bone and become life-threatening.

A personal example: I had a hen who liked to roost on the very top of the coop instead of inside with the others. There were no predator threats in the yard, so over time I stopped fighting it and let her be. A month or two later, she dropped dead with no warning — no limping, no visible signs of distress beforehand. When I went to pick her up, the bottoms of both feet had bumblefoot. She'd been cutting herself on the chicken wire edge every time she jumped up to the roof, and the infection had been building silently for weeks.

What causes it:

  • Small cuts or punctures from rough surfaces, wire, or sharp debris
  • Hard landings from roosting at significant heights
  • Wet or dirty bedding that keeps feet perpetually damp and creates easy entry points for bacteria
  • Obese birds that put more pressure on foot pads

What to watch for:

  • A dark, hard scab or black plug on the bottom of the foot pad
  • Swelling around the foot pad
  • Limping — though some birds, as the story above shows, hide it remarkably well
  • Birds that are reluctant to move or stand

What to do: Mild cases (small scab, minimal swelling) can be treated at home. Soak the foot in warm Epsom salt water for 10 to 15 minutes to soften the area. Gently remove the scab and any visible core of infection with clean tools, apply Vetericyn wound spray or Betadine to the area, and wrap the foot securely with a bandage and vet wrap to keep it clean. Repeat daily until healed. Keep the bird on clean, soft bedding during recovery.

More advanced cases with significant swelling, deep infection, or birds that aren't improving after a week of home treatment need a vet — in serious cases, surgery and antibiotics are required.

Prevention: Regularly check your birds' feet, especially if they roost at height or on rough surfaces. Keep bedding dry and watch for any sharp wire edges or rough roost surfaces that could cause injury.

6. Respiratory Illness (Mycoplasma / CRD)

Respiratory illness is one of the most common problems in backyard flocks, and it can show up after introducing new birds, during periods of stress, or following damp, cold weather. The most common culprit is Mycoplasma gallisepticum, also called chronic respiratory disease (CRD). It spreads through direct contact with infected birds and through the air — which is why new birds introduced to an established flock are one of the most frequent triggers for an outbreak.

What causes it:

  • Introducing asymptomatic birds that are carriers of mycoplasma
  • Stress from crowding, weather changes, or shipping
  • Damp, poorly ventilated coops
  • Other illnesses weakening the immune system

What to watch for:

  • Coughing, sneezing, or gurgling sounds
  • Nasal discharge or runny eyes
  • Swollen sinuses (the face may look puffy)
  • Reduced egg production
  • Rattling breathing sounds — this is a sign things have progressed

What to do: Mycoplasma is treatable with antibiotics — tylosin and oxytetracycline are the most commonly used in backyard flocks and are available at feed stores. Isolate affected birds immediately to slow spread through the flock. Improve ventilation in the coop — fresh air flow matters, but avoid drafts at roost level. Birds that recover from mycoplasma can become lifetime carriers, so a strict 30-day quarantine for any new birds before introducing them to your flock is one of the best preventive steps you can take.

Bonus: Marek's Disease — Know the Signs

Marek's disease is a highly contagious herpes virus that primarily affects young chickens between 10 and 25 weeks old. There is no treatment, but there is a vaccine — and if you're ordering day-old chicks, requesting the Marek's vaccine at the hatchery is one of the most important things you can do. The virus spreads through dander, feathers, and dust from infected birds and can remain alive in the environment for months.

Signs: Leg or wing paralysis, irregular pupil shape, tumors, sudden unexplained death in young birds.

If Marek's is suspected in your flock, contact your state veterinarian or local extension office. Birds that survive often remain carriers.

The Most Important Habit: Daily Observation

None of these illnesses announce themselves loudly. The best thing you can do for your flock is spend five minutes a day just watching them. Active, curious behavior, bright eyes, red combs, and normal droppings are your baseline. When something is off — even slightly — you'll notice it faster if you know what "normal" looks like.

Catch things early, isolate quickly, treat consistently, and your birds have a much better chance of full recovery.

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