Chicken Diseases: 5 Common Ailments

How to Prevent & Spot Poultry Ailments

by Erica Webb

Chicken diseases are not always top of mind when you first start raising chickens. Chickens are relatively easy to raise and, when cared for properly, will provide a plethora of backyard eggs. Understanding disease and health conditions and how to prevent them will help keep your birds healthy and laying for many years to come. Here are five common backyard poultry diseases to get to know.

Coccidiosis is a legitimate health issue for backyard chickenkeepers, especially in chicks.

Chicken Diseases: Coccidiosis

A protozoal parasite known as Eimeria, which infects multiple intestinal sites within the bird, causes this disease. Coccidia is almost universally present in all operations and occurs after ingesting an abundance of spores often found in infected feed or feces. This protozoon sets up shop in the intestinal lining, reducing the bird’s ability to absorb nutrients leading to diarrhea, lethargy, weight loss and, in extreme cases, death.

Although it can affect birds of all ages, young birds are often overrepresented due to their naïve immune system. Due to the nature of this disease, birds often pick up secondary bacterial infections because of their compromised state, making it difficult to diagnose based solely off gross observation. With the help of a veterinarian, a fecal float can be performed to help diagnose if coccidia is present.

Even with great management, coccidia can’t always be controlled. Reducing risk is key to preventing an outbreak in your flock. Always provide a clean and dry environment for your birds. Removal of feces frequently greatly reduces pathogen exposure and spread.

Given a healthy flock of birds, coccidia can be self-limiting under certain conditions; however, treatments are available to fast-track recovery. Coccidiastat medications are available on the market today that are highly recommended for growing birds. The most common, Amprolium, is often found in medicated feeds or given as a water additive. This medicated feed should be given at 1-day-old and continued until approximately 20 weeks of age, or right before the birds begin laying. Because most birds often recover from coccidia infections, vaccines aren’t usually given.

Bumblefoot is an infection caused by bacteria; it’s usually the result of an injury to the foot, such as a cut, scratch or puncture that then becomes infected.

Chicken Diseases: Bumblefoot

Bumblefoot is a common name for pododermatitis or infection affecting the bottom of the foot. This abscess-type lesion is caused by a bacteria known as Staphylococcus which is commonly found in the environment. This condition often presents with swelling of the foot, lameness and a hard, pus-filled pocket on the bottom of the foot covered by a round, dark-brown scab.

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Contributing factors that may lead to this condition include being overweight, long toenails or having a leg injury. Deformities or leg injuries can cause uneven weight distribution to the foot pads which stresses the soft tissue of the footpad leading to infection.

In many cases, bumblefoot can be managed at home if found early. Soaking the bird’s foot in warm Epson salt solution will help draw out and kill the bacteria causing the infection. After soaking, the area can be cleaned with a 2% chlorohexidine or betadine solution and wrapped to keep the foot clean and dry.

Ointments containing silver or other antibiotic properties may also be beneficial in clearing the infection.

If infection persists, surgical debridement by a veterinarian will help eliminate dead tissue and promote faster healing. Environmental management is a key contributor to reducing incidence of Bumblefoot. Prevent accumulation of mud and feces in loafing areas and provide soft bedding. Perches should be round or wide enough that they do not cause pressure sores when stood on for extended periods of time. Allowing birds to exhibit natural foraging behaviors such as free-ranging in grass has also been shown to decrease instances of infection.

Marek’s disease causes a wide range of symptoms including a splayed leg appearance.

Marek’s Disease

Marek’s disease is by far one of the most common viral infections in backyard birds and isn’t treatable once signs have begun. Marek’s disease is caused by a chicken herpes virus that is contracted from other birds by inhaling virus laden dander. Though birds of any age can contract Marek’s, it appears to be more common in young growing birds less than a year old.

This virus causes a wide range of symptoms varying in severity with an average mortality rate around 50%. Birds often show signs of depression early on which progresses to full body paralysis/ataxia and a splayed leg appearance. Upon necropsy, tumors are often found throughout many organ systems including the liver, heart, kidneys and spleen.

Though there is no treatment for Marek’s, vaccines are available to prevent infection. Vaccines should be given as chicks to build immunity before potential exposure. This is a lifelong disease, so those birds who survive infection will be carriers and can shed virus to other birds throughout their life.

Marek’s is exceptionally hardy in the environment and lives in poultry dander for months to years. Because of this, new birds brought in should always be quarantined prior to introduction into a flock. Previous outbreaks will require intense disinfection of coops, feeders and waterers prior to new birds inhabiting them.

Careful consideration should be taken when attending poultry shows or sales, as this virus is easily carried to and from farms on clothing and shoes. The combination of vaccination and good biosecurity make this an extremely preventable disease.

Chicken keepers shouldn’t invite other birds to their property. Wild birds can bring avian flu to your flock.

Avian Influenza

Avian influenza or bird flu is caused by an influenza type A virus. There are two types of bird flu which vary in severity of disease. Low-pathogenic avian influenza naturally occurs in migratory birds and can affect domestic chickens without causing much illness.

High pathogenic avian influenza is extremely contagious and causes severe illness with high mortality rates in all poultry birds. HPAI is a major concern for the U.S. poultry industry. Outbreaks of HPAI have huge economic impacts in the meat and egg markets by easily wiping out huge flocks in a short time. This affects farmers and consumers by reducing food supply and international trade.

Those with backyard flocks may be more susceptible to avian influenza due to birds being in proximity to wildlife birds. Because of this, be sure to have a good understanding of biosecurity to keep domestic backyard birds, production birds and wild birds safe.

Symptoms of avian influenza vary but include purple discoloration of the wattle, combs or legs, nasal discharge, sneezing, diarrhea, incoordination or even sudden death without any clinical signs. If these symptoms are noted, caution should be taken when handling sick or deceased birds to prevent zoonosis or transfer of disease to humans.

Currently, the U.S. Fish and Wildlife Services conducts yearly surveillance to identify risk factors among wildlife for avian influenza to prevent devastating outbreaks. If flock owners suspect an outbreak of avian flu, reach out to your local veterinarian or state agriculture department to ensure proper testing and diagnostics are performed to prevent the spread of this disease.

Currently, no approved vaccines are available for avian influenza. Although vaccines exist, often they aren’t congruent to the high-path strains that are seen during an outbreak. The best method of control is to maintain biosecurity by quarantining birds coming in from outside sources such as bird auctions and trade shows, and being aware that wild birds living amongst your flock can harbor this disease.

Mobile chicken coops are a great way to promote healthy birds and soil. Rotating through areas is great for soil health and prevents fecal matter buildup.


Mycoplasmosis is a common respiratory infection found in backyard poultry caused by a group of mycoplasma bacteria. Apart from the typical respiratory signs of wheezing, watery eyes and coughing, mycoplasma also causes a reduction in egg production followed by weight loss, joint disease and overall loss of thriftiness. Although the disease is more severe in turkeys, mortality rates of mycoplasma are relatively low. In chickens, subclinical infections may exist, showing no outward signs of sickness apart from a decrease in egg production. Over time, impaired immune function caused by infection of mycoplasma can lead to secondary opportunistic respiratory disease, such as bronchitis, which often leads to more severe sickness and death.

Diagnostic testing is needed to confirm presence of the pathogen and verify strain. This is done by collecting tracheal swabs and sending samples off to a diagnostic lab for testing.

Mycoplasma can be vertically transmitted through egg production meaning that an infected hen can transmit disease to their chicks through the formation of her egg.

Because of this, breeding hens carrying mycoplasma should be treated aggressively with antibiotics or culled as breeders.

The most effective control of mycoplasma is to maintain good biosecurity by responsibly introducing new birds to the flock and monitoring mycoplasma by testing the flock frequently. Some vaccines are commercially available although thorough monitoring and biosecurity have proven to be more efficacious.

Backyard birds can be a fun venture for many hobbyists. As a common theme, biosecurity and a well-managed environment seem to be the best way to prevent outbreaks of chicken diseases. Should chicken diseases persist, having a good relationship with a poultry veterinarian will be helpful in providing diagnostics and determining the best route for treatment of the disease or pathogen. If there is concern about human health or severe disease, always contact your state agricultural department or state veterinarian for further information. By being proactive about poultry health, we can avoid many chicken diseases and spend more time enjoying the pleasures of backyard poultry.

This article about chicken diseases was written for the January/February 2024 issue of Hobby Farms magazine. Click here to subscribe.

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