Chickens ill

Common Chicken Diseases – An Overview!

When your chickens are healthy, they cluck and scratch. They flap their wings enthusiastically, peck at food and run around in their run. Accordingly, you quickly notice when your animals are sick. Then they are apathetic and refuse to eat. Other symptoms can also occur. To be able to help your sick chickens quickly, you should know the signs of common or dangerous chicken diseases.

In our chicken guide we present you common diseases of chickens.

General signs of illness in chickens

If your chickens are unwell and suffering from one of the diseases listed below, you may recognize this by the following symptoms:

  • Decreased feed and water intake
  • Secretion of the affected animal
  • Decrease in laying performance
  • Blocked nostrils, difficulty breathing
  • Diarrhea
  • Apathy


When chickens are sick, you must check how they are doing several times a day. Contact your veterinarian in time! A quick diagnosis is important, because many chicken diseases have an acute course.

Typical diseases of the chicken

As with diseases of humans and other animals, parasites, bacteria or viruses are often the reason why chickens get sick. Fungi or metabolic problems can also be the cause of chicken diseases.

Parasitic diseases of the chicken


Coccidiosis is the most important parasitic disease in poultry – also because it is economically very important. It is caused by the so-called coccidia, parasitic protozoa. Particularly affected are the chicks, which become emaciated and suffer from diarrhea.

A distinction is made between appendiceal coccidiosis, small intestinal coccidiosis and rectal coccidiosis. Appendiceal coccidiosis is also known as “red chick dysentery” because the chicks defecate bloody feces due to damaged intestinal mucosa. It can be associated with an eighty percent mortality rate.

Red bird mite

You’ll have a hard time spotting the red bird mite. The mites hide during the day in the crevices of laying nests or the underside of perches, for example. When a flock is heavily infested, birds are restless and feather pecking and cannibalism may occur. Egg yolks are pale or blood splatter on egg shells occurs. Animals also become weak and their performance drops.


Red bird mite can transmit viruses and bacteria.

Foot scab mites (calcareous legs).

Certain mites cause what are called lime legs in chickens. These parasites burrow into the top horny layer of the skin on the legs of the birds. You can recognize the infestation with foot scabies mites by a thick bark. The affected animals can only walk with difficulty.

In any case, note that chalky legs are a highly contagious disease.


You can soften the bark and wash it off with a soft soap solution. Also, anti-mites will help your chickens recover. When controlling the mites, you must thoroughly clean and disinfect the animals’ environment.


Not all worms necessarily cause signs of disease in poultry. If the animals are healthy and immunocompromised, they can certainly keep the worms at bay. However, a worm infestation can also show itself in different symptoms.

Examples of worms in chickens include the following:

Young chickens often become emaciated due to roundworms and hairworms. The animals suffer from diarrhea. Their plumage is shaggy.
Tapeworms make chickens tired after prolonged infection and strain the immune system. Therefore, the animals become more susceptible to other diseases.
Tracheal worms lead to a lack of food as well as shortness of breath.
Important to know at this point is for you: Worms are transmitted through feces of diseased animals. This can be other chickens, but also wild animals. The animals are particularly often infected in the run. If you want to protect your flock from a worm infestation, you should perform a worming treatment at regular intervals.

Bacterial diseases of chickens

Contagious chicken cold

If your chickens suffer from contagious chicken cold, they have been infected with Avibacterium paragallinarum. They show nasal discharge and inflamed conjunctivae. You will then recognize the typical “owl’s head” that forms as a result of swollen sinuses. The animals sneeze and may show beak breathing and head shaking because the nostrils are congested. The entire flock is dull, eats poorly, and drinks little. Performance is reduced. The disease is very contagious.


The good news is that you can vaccinate against it and hygiene measures work well. Also, therapy with antibiotics is possible.


Mycoplasmosis of chickens is caused by mycoplasma and affects mainly preweakened animals. It is one of the factor diseases and occurs especially when hygiene on the farm is poor and other accompanying infections are common. Stress is also one of the factors for mycoplasmosis disease.

Four- to eight-week-old chicken chicks are the most likely to contract the disease. They first show inflamed conjunctivae and nasal and ocular discharge. Problems with breathing may be added. The birds eat less and their feathers appear unkempt.


To avoid the disease, you must feed the chickens properly, reduce the stocking density if necessary and also regularly disinfect and clean the chicken house. With hygiene measures you can effectively prevent mycoplasmosis.

Poultry tuberculosis

The pathogen Mycobacterium avium causes avian tuberculosis. The bacteria are very resistant, so they survive in the environment for years and remain infectious. This makes it a major problem not only for private chicken farmers.

Tuberculosis disease in chickens is difficult to detect because it is insidious. Despite their appetite, the animals lose weight and even their breast muscles shrink. The disease runs chronically and only in the advanced stage the affected chickens show clear indisposition. They die by emaciation or internal bleeding. If you, as a chicken keeper, want to permanently solve the problems surrounding the infection with the tubercle pathogens, the only option is usually to kill all the animals and build a new housing facility on a different property.


Tuberculosis in poultry is reportable. The responsible authorities should have an overview of how often the disease occurs.
Avian tuberculosis is transmissible to humans. Immunocompromised humans and children are at risk.

A tuberculin test of all birds will tell you if your flock is free of tuberculosis. Ask your veterinarian about this.


Colisepticemia, or colibacillosis, is caused by certain strains of Escherichia coli bacteria that are pathogenic specifically to birds. Basically, Escherichia coli bacteria are ubiquitously distributed and are part of the normal intestinal flora.

The disease occurs most frequently during the first eight to ten weeks of life. However, laying hens also fall ill. In young animals, the virulence of the germs still plays a major role, while in older animals the disease becomes increasingly important as a factor disease.

Clinical signs include inflammation of the air sacs, yolk sac, pericardium, serous membranes, and oviduct, in addition to early mortality.


With an antibiotic, which is selected after an antibiogram, you can fight the infection. There is a vaccine for older animals.
Prophylactic measures like stable hygiene and optimal stable climate help you to reduce the infection pressure. Also, your animals will not get sick as quickly from E. coli bacteria if you consistently treat them for other diseases and deworm them regularly.
Viral diseases in chickens
Newcastle Disease or Atypical Avian Influenza
Newcastle disease or Atypical Avian Influenza has the following characteristics:

Highly contagious

Subject to compulsory vaccination

Newcastle disease virus, a member of the Paramyxoviridae family, causes Atypical Avian Influenza. It is transmitted through chicken droppings, body fluids, and respiratory air. If even one animal in a flock becomes ill, all chickens that have come into contact with it must be killed. One reason for this is the highly contagious nature of Newcastle disease. It can also be transmitted to other bird species.

Symptoms of Newcastle disease include high fever and a severe decline in laying performance. The birds are apathetic and lack appetite. They also show diarrhea and respiratory distress. Often the comb is dark in color. Many birds die within the first five days.


So be sure to adhere to the vaccination requirement! If you disregard this requirement and Newcastle disease breaks out, all animals will be killed. It is therefore important that you have a reliable veterinarian who will advise you and vaccinate the animals. Keep in mind that vaccinations are among the most important preventive measures for animal health!

Avian Influenza (Bird Flu, Avian Influenza)

Avian influenza is a highly contagious viral disease of chickens and turkeys. It is caused by avian influenza viruses. Other birds are also susceptible. Wild fowl often transmit the virus but do not contract it themselves.

The disease is rapid and ends in death in almost all affected birds. The birds are highly febrile, listless, and lack appetite. They may also show respiratory distress and their laying performance decreases.


Avian influenza is one of the notifiable animal diseases. A suspicion must be reported immediately to the competent authority. Then veterinarians take samples, which special official laboratories examine. If the samples are positive, the flock is killed in accordance with animal welfare regulations. Other measures are also taken. For example, a protection zone is established around the site of the outbreak.

Marek’s disease

The causative agent of Marek’s disease, also known as poultry paralysis, belongs to the herpes viruses. Young animals in particular become ill, and morbidity decreases from the 13th week.

In the classic form of Marek’s disease, paralysis is seen in animals 12 to 16 weeks old. However, this form occurs only sporadically. The mortality rate here is less than ten percent.

The acute form, on the other hand, occurs epidemically. Here, chicks up to eight weeks of age are affected. In particular, 18 to 22-week-old animals die. The mortality rate here is up to fifty percent.

In the acute form, skin changes appear in the form of elevations. The animals lose a lot of weight and die as cancerous growths form in the internal organs.


Marek’s disease is one of the notifiable animal diseases. A therapy of the viral disease is not possible. However, a vaccine exists and is usually administered on the first day of life.

Infectious laryngotracheitis

Infectious laryngotracheitis (ILT) is a contagious inflammation of the larynx and trachea in chicken birds. It is caused by a herpes virus.

You can recognize the disease by your chickens’ coughing, wheezing and shortness of breath. If applicable, the regurgitated mucus is discolored with blood. If the viral strains that occur are less virulent, the birds may just develop sinusitis or conjunctivitis.


The disease is one of the reportable animal diseases. To prevent it, implement strict hygienic measures. You can also have your animals vaccinated against ILT.

Infectious Bronchitis (IB)

The causative agent of infectious bronchitis of domestic chicken and pheasant is infectious bronchitis virus (IBV), a coronavirus. The virus is transmitted via droplet infection, so the disease spreads rapidly. Young animals are particularly affected. Up to 25 percent of the animals may die.

Signs of the disease include shortness of breath, nasal discharge and conjunctivitis. In addition, the general condition is disturbed. The animals eat poorly. In laying hens, infections of the fallopian tubes lead to laying disorders. Eggs are thin-shelled and wind eggs occur.


Control of IB is by vaccination beginning at three weeks of age. If you keep your animals in an area at risk, it is recommended to repeat the vaccination every three to four weeks.

Checklist: Measures that prevent an outbreak of many chicken diseases.
In addition to keeping chickens in an animal-friendly manner, regular vaccinations protect against common diseases. Therefore, consult a veterinarian to focus on preventative protection for your fowl!

You can also take daily steps to help keep your flock healthy. These include:

  • Create and ensure animal-friendly housing conditions!
  • Avoid frost, summer heat and humidity in chicken coops as well as in the run!
  • Quarantine new, injured and already sick chickens!
  • Avoid stress by keeping your chicken flock sufficiently large and appropriate!
  • Ensure access to clean drinking water and feed for each chicken!
  • Clean and disinfect the chicken-friendly coop regularly!
  • Protect your chickens from wild animals around the clock. Think also of the free run!
  • If necessary, enrich the drinking water and feed with high-quality multivitamins and minerals!

Furthermore, if possible, check every day whether your animals are doing well. If this is not possible for you, you should assign another person with it. This person must have the necessary expertise. After all, the most common chicken diseases are often the result of carelessness, poor husbandry or ignorance about possible vaccinations. Many diseases can be avoided, which in turn will save you time, nerves and money.

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