Diseases of small poultry flocks


Many diseases can affect your small poultry flock. Practicing biosecurity and proper management can help keep birds healthy. If you suspect disease in your flock, consult with a veterinarian or the University of Minnesota’s Veterinary Diagnostics Laboratory.


Staphylococcus aureus infection is a bacterial infection in the bloodstream. It’s marked by arthritis and swelling around the tendons. This infection is also known as staphylococcosis, which relates to bumblefoot or navel ill.


As the name implies, the bacteria staphylococcus is responsible for this infection. This bacteria naturally lives on the bird’s skin and in the environment. When given the opportunity, such as a skin injury, the bacteria enters the bird’s skin and infects the blood. Skin injuries can include the following:

  • Scratches
  • Excessively moist skin
  • Needle or claw punctures

The bacteria must enter the skin to cause infection and can’t be directly passed from bird to bird.

Swollen foot pad and joints of a chicken foot

Signs of illness

  • Yolk sac infection
  • Necrotic dermatitis
  • Necrotic skin lesions or abscesses
  • Arthritis and swollen tendons
  • Bone infection and swelling
  • Swollen joints or footpads (bumblefoot)
  • Breast blisters
  • Dead chicks with a swollen abdomen and crusted navel
  • Dead cell mass in bone growth plate

Prevention and treatment

The best way to prevent this infection is by reducing trauma in the coop.

  • Eliminate sharp objects
  • Trim beaks and toes
  • Avoid wet litter or leaking drinkers

Antibiotics (e.g. erythromycin) may be useful during a breakout.

The bacteria, Escherichia coli (E. coli), can cause infection in poultry. It can be the primary disease agent or a secondary invader causing the following:

  • Bloodstream infection
  • Swelling of the abdominal wall lining
  • Skin infection
  • Yolk sac infection
  • Fallopian tube swelling
  • Swollen air sacs


E. coli lives everywhere and can be found in the intestines of birds and mammals. Thus this bacteria usually spreads through feces. Often infection occurs due to poor management while treating the birds for another infection.

Birds can become infected with E. coli by direct contact with dirty litter and hatchers or contaminated eggshells. However, the infection doesn’t pass from bird to bird.

Signs of illness

  • Poor growth (ill-thrift)
  • Ruffled feathers
  • Enlarged or swollen navel
  • Decreased appetite
  • Depression
  • Diarrhea
  • Pasting of feathers around the vent


E. coli in commercial poultry is often resistant to many antibiotics. In addition, few antibiotics are available for poultry. Working with a veterinarian and taking a culture sample may help with treatment if more than one of your birds is sick.


  • Keep your facilities clean
  • Clean the eggs (fumigation)
  • Control dust in your poultry house
  • Routinely move dead birds from the house
  • Prevent stress on your birds

This chronic disease affects a variety of birds, especially chickens and turkeys. It’s marked by nasal discharge, coughing and weakness. The National Poultry Improvement Plan monitors this disease because it’s been a major problem in the poultry industry.


The bacteria, mycoplasma gallisepticum, causes chronic respiratory disease/ infectious sinusitis. This disease can pass from bird to bird in a couple of ways.

  • From breeder birds to offspring through the egg
  • Through the air

Chronic respiratory disease in chickens can occur with other diseases including E. coli infection.

Turkey head with swollen area between the eye and beak
Swelling below the turkeys eye from infectious sinusitis

Signs of illness

Adult laying hens

Signs in adult laying hens are rare but can include the following:

  • Decreased egg production
  • Decreased feed intake
  • Increased medication costs

Broiler chickens

Chronic respiratory disease is present in affected broiler chickens and includes:

  • Coughing
  • Sneezing
  • Discharge around the nose and eyes
  • Poor feed conversion
  • Air sac disapproval at processing


Infectious sinusitis is present in affected turkeys and includes:

  • Swelling on one or both sides of the head between the eyes and beak
  • Nasal discharge on wings
  • Air sac disapproval at processing


Treatment won’t stop infection or prevent disease spread in eggs.

In small breeder flocks, you may want to blood test for infection and remove the infected breeders from your flock.

Injectable tylosin can limit the clinical signs of chronic respiratory disease/ infectious sinusitis. Tylosin is not approved for birds used for eggs or meat.


You can vaccinate chickens for chronic respiratory infection, but not turkeys. Due to vaccine reactions, it’s best to purchase chicks and poults from NPIP Mycoplasma certified-free breeder flocks. Avoid swap meets and “exceptional deals.”

Marek’s Disease is a cancer-causing disease in poultry. Tumors may occur in various areas including:

  • Nerves
  • Ovaries
  • Testes
  • The main body cavity
  • Eye
  • Muscle
  • Skin


Herpes virus infection is responsible for causing Marek’s Disease in poultry. The virus is produced in the feather follicles of infected birds. Thus direct or indirect contact between birds can spread the disease. Molted feathers or dander from infected birds can contaminate areas around the bird. Other birds that inhale contaminated dust can catch the disease. Contaminated dust can remain infectious for a few months.

Birds that appear healthy can carry and spread the disease. Some birds can shed the virus from their skin for up to 18 months.

Darkling beetles may also spread disease between houses.

Pullet with splay-legs from disease
Marek’s disease causes nerve damage, which can affect a chicken’s posture (e.g. splayed legs) or ability to move.

Signs of illness

Usually, signs of disease don’t appear until three to four weeks after the birds are infected. In sudden breakouts, you may see the following signs.

  • Severe depression
  • Anorexia
  • Poor coordination
  • Paralysis of the legs and wings

Many birds become dehydrated, weak and thin and eventually die. Death gradually builds in flocks and lasts for 4 to 10 weeks. Suppressed immune systems can be a long-term effect in flocks affected by Marek’s disease.

In Ocular Marek’s disease, the bird’s pupil size decreases and has an abnormal diameter.


There are no specific treatments for chickens with Marek’s disease. You should focus on preventing disease in your flock.


Vaccinating against Marek’s disease is an effective control. This vaccine is usually given on day one or injected into the embryo three days before hatch. Marek’s disease vaccines achieve over 90 percent protection in commercial conditions.

Infectious laryngotracheitis is an acute, highly infectious viral disease. It’s marked by swelling of the inner eyelid, loud gasping, blocked airways and bloody discharge when coughing.


Herpes virus causes ILT in poultry flocks. The virus grows in the throat and lungs of infected birds.

Birds can become infected if the virus enters their respiratory system or eyes. Caretakers are often the root problem in spreading ILT. ILT spreads from the use of contaminated equipment, clothing, shoes and litter between flocks. Common disinfectants can easily kill this virus.

Birds that recover from infection can still carry the virus for up to 16 months and sometimes shed the virus.

Adult chicken with ILT extending its neck to breathe
Chickens with ILT will try to improve their breathing by extending their necks.

Signs of illness

Acute infections are marked by the following:

  • Nasal discharge
  • Moist, abnormal lung sounds
  • Coughing
  • Gasping
  • Extended neck, sometimes
  • Red eyelids and runny eyes, sometimes

In severe cases, birds may have labored breathing and cough blood-stained mucus. Often the mucus covers the bird’s feathers due to the bird shaking its head while coughing. Blood and yellow mucus in the throat can suffocate the birds.

In mild cases, birds have poor growth; red, swollen eyelids and nasal discharge.

Death can vary from five to 70 percent of the flock depending on the severity of the disease. Most chickens recover in two weeks.


The virus spreads slowly so vaccinating the flock early on in an outbreak can limit the number of deaths. Giving broad-spectrum antibiotics may reduce secondary infections.


  • Vaccinate all breeder and layer birds at the proper time
  • Limit visitors going into the poultry house


There are two common types of ILT vaccines 1.) an eyedrop vaccine at one day of age and 2.) a drinking water or spray vaccine. Vaccinate layers before they start producing eggs. Commercial layers are usually vaccinated by eyedrop or spray at 7 to 8 weeks old and again by spray or drinking water at 12 to 14 weeks.

Take care while giving vaccines to help avoid any bad reactions. Make sure all the birds get the vaccine. The virus in the vaccine may cause disease in unvaccinated birds as it passes from bird to bird. For this reason, we rarely recommend ILT vaccinations in small flocks.

Gout commonly occurs in older laying flocks and relates to kidney failure. Sometimes gout can cause high death rates (up to 0.5 percent per week). Losses tend to be chronic with the number of birds affected and depends on the severity of kidney damage.


Kidney damage and gout can occur from the following:

  • Low phosphorus in the diet
  • Lack of water at housing
  • High vitamin D3 in the diet
  • Too much calcium before 15 to 16 weeks of age
  • Infectious bronchitis

Birds with gout have a build-up of urates (salts common in urine) on their internal organs or in their joints.

Signs of illness

Birds with gout usually show no signs of illness before death. Sometimes these birds are thin.


You can add ammonium sulfate or ammonium chloride to your birds’ diet to help treat gout. This treatment may cause wet droppings and poor shell quality. The success of this treatment does vary between cases.


  • Make sure your birds’ ration contains one percent calcium and 0.45 to 0.50 percent available phosphorus throughout growing.
  • Start layer levels of calcium feeding one week before the first egg.

Make sure the birds have free access to water at housing.

Poultry with fatty liver syndrome have an excessive build-up of fat around the liver or abdomen. Fatty liver is most common in caged layers but sometimes occurs in breeder turkey hens.


Fatty liver results from an imbalance of energy and protein intake. Caged layers are most prone to fatty liver because they receive little exercise and eat a high-calorie diet.

Cases of fatal fatty liver have been increasing in backyard birds. Usually, these affected birds are large, obese hens that likely control the feeder.

Bursting and bleeding of the fatty liver is a common cause of death in laying hens.


Make sure your flock’s diet has the proper energy and protein levels. You can reduce these levels in the feed to prevent obesity in your hens.

Normal vent
Normal vent (cloaca)

Cloacal prolapse is when the vent of laying hens turns outwards when a hen lays her egg. The vent can remain out permanently and swollen if pecked by other hens or while laying a large egg. Affected birds may die from pecking by other birds.


In small flocks, you may see cloacal prolapse in hens with small bodies relative to their egg size (e.g. bantam chickens). A few factors affect the severity and occurrence of cloacal prolapse including:

  • The strain of bird
  • Diet quality
  • Amount of floor, feeder and drinker space
  • High light intensity
  • Large egg size
  • Age of laying bird
    Cloacal prolapse
    Cloacal prolapse
    • Young birds early in lay are more prone to cloacal prolapse

Treatment and prevention [H3]

Low-intensity lighting and good floor, drinker and feeder space can reduce flock aggression.

You can limit vent trauma and cloacal prolapse in floor-raised chickens by offering perches or obstacles such as straw bales or plastic drinking jugs. These will help protect the hens and maintain good nest to hen ratios (1 nest to 4 hens).

Cage layer fatigue is a nutritional disease that causes soft, pliable bones including:

  • The beak
  • Curved keel bone
  • Beading of the ribs


Chickens have about 200 grams of calcium in their bodies. They use about 2 grams of calcium daily to produce an eggshell. High calcium use for egg production and little calcium replacement causes cage layer fatigue. Little exercise in caged birds may make them more prone to this disease.

Turkey poult that can’t walk due to osteomalacia
Soft, pliable bones can hinder a bird’s ability to walk

Signs of illness

Laying hens kept in cages may show paralysis during peak egg production. The birds may lay on their sides in the back of the cage. Even at the start of paralysis, the birds will seem healthy and have a shelled egg in the oviduct.

Birds may die from a lack of water or feed if they become unable to reach it.


Provide pullets a high calcium diet (at least 3.5 percent calcium) at least two weeks before first egg laying.

Right ventricular failure is a form of heart failure that causes ascites. Ascites refers to a build-up of fluid in the bird’s abdomen. This is a metabolic disease of broiler chickens and ducklings. It’s seen in some broilers at processing and can cause one to two percent death in some flocks.


Birds are prone to right ventricular failure because a muscular flap forms part of their heart valve. Respiratory problems and poor air quality can worsen this disease.

Other factors that make birds prone to this disease include:

  • Breeding for high feed efficiency with rapid rate of growth and muscle
  • Low ratio of total lung volume to body weight
  • Free access to high energy and high quality feeds

If deaths exceed one to two percent from ascites, look for other possible factors such as:

  • High sodium levels in feed or water
  • Vitamin E or selenium deficiency
  • Respiratory infection
  • Furazolidone or coal tar toxicity

Signs of illness

  • Sudden death at three to five weeks of age of previously healthy birds with good rates of gain
  • Live birds are smaller than normal, don’t want to move, have respiratory distress and a bloated abdomen
  • Combs and wattles are pale to bluish in color


  • Decrease energy level in feed to slow down growth rate.
    • Try limiting feed during the grow-out or turning off house lights at night
    • Adjust birds to dark-out periods at an early age to limit stress
  • Maintain good air quality with adequate ventilation, especially during winter


Small poultry flocks may be affected by a multitude of parasites. It is important to determine which one your flock has and design your response plan specifically for that parasite.


Coccidiosis refers to a parasite invasion in the bird’s gut. It remains one of the most common and costly diseases in poultry. These infections are most common in poultry raised on the ground versus caged.


Birds eat the parasite’s eggs from their environment. These parasites live and reproduce inside the bird’s gut and cause damage to the gut tissues. The parasite’s eggs pass in the bird’s feces and once outside, they mature and become infectious. Moist, warm litter can help the eggs mature faster.

Coccidiosis usually occurs in turkeys and broilers. Range, cage-free layers are at higher risk of infection than other poultry.

Signs of illness

  • Ruffled feathers
  • Depression
  • Blood in droppings
  • Shivering
  • Increased death in the flock, especially caged pullets
  • Decreased egg production in birds at reproductive age

Treatment and prevention

  • You can use anticoccidial drugs to kill (coccidiocidal) or decrease the growth rate (coccidiostat) of the parasite at 1 to 4 days of infection.
    • To prevent parasite resistance, change the coccidiostat within the grow-out period of your flock. Use a different product in the starter ration than in the grower ration. Make sure to change products up to twice a year.
  • Vaccinate birds, especially layer breeders and floor- or range-raised layers.
  • Kill parasite eggs in your flock’s environment or prevent parasite exposure.

Roundworms are a parasite that invades and lives in the upper and small intestines of turkeys and chickens. These worms can cause great damage to the bird’s intestines.


Birds pick up this parasite from their environment. As the worms mature inside the bird, they start to produce eggs about a month after infection. These eggs pass in the bird’s feces and remain infective in the environment for over three years. The eggs are resistant to low temperatures but do better in warm, moist litter.

Poultry roundworms and intestinal content
Intestinal roundworms found in a floor-raised pullet

Signs of illness

  • Depression
  • Weight loss
  • Diarrhea
  • Decreased growth
  • Lowered egg production in severe infections

Treatment and prevention

  • Confining or caging birds can reduce problems with intestinal parasites
  • Provide deep litter (4 to 6 inches of wood shavings)
  • Clean out your hut and equipment between flocks
  • Treat pullets before transferring them to the laying house
  • Treat infected birds with piperazine
Adult mite
Adult mite

Northern fowl mite

The Northern fowl mite can be costly for the following reasons:

  • Decreased egg production
  • Increased feed intake
  • Reduced weight gains
  • Reduced semen in roosters

Roosters tend to be more heavily infested with these mites than hens. Northern fowl mites are worse during the cold months of the year when the birds have close contact.

Mite life cycle

The full life cycle of Northern fowl mites takes five days. The adult mite can then live on the bird for three to four weeks. Often, mites stay on a single bird during their lifetime.

Dark stains and mites on white vent feathers of a chicken
Mites present in the vent feathers of an infected chicken

Red chicken mite

Red chicken mites feed on blood and are most active at night. During the day, the will leave the birds and live in the nest boxes and the cracks and crevices of perches in the poultry house.

Signs of mites
  • Rough, scaly feathers
  • Dark, stained feathers around the vent from mite eggs, scabs and feces
  • Anemia, low red blood cells
  • Decreased egg production

You can check for mites around the vent on hens or over the entire body on roosters. Check a few birds. Not all birds will be infested with mites. It’s best to check for mites at night when they return to the birds.


Mites on chicken’s wing feathers
Mites pepper the wing feathers of a leghorn chicken

It may be most economical to use a commercial five percent carbaryl dust in small flocks. Place 2.5 pounds in one dust box per fifty birds. Carefully dust the product on the vent region. Sprinkle the dust around nest boxes and along cracks and crevices in the hen house.


You can use insecticide sprays for heavy mite infestations. You must apply these sprays at about 100 to 125 PSI with one gallon of water per 100 birds. Always follow the instructions and pertinent information stated on the insecticide label.

For the best results, spray caged birds from underneath and spray floor raised birds at night while resting on the slats. Since the mites don’t live on the birds during the day, you should also spray or dust insecticides around the nest area.

Mite-infested chicken
Mites live on the bird’s skin and feathers


  • Clean, disinfect and check the house for mites before introducing new birds
  • Check new birds for mites before they enter your flock
  • Check equipment, clothing and egg flats for mites to prevent spreading mites to other flocks
  • Use washable egg flats and steam clean or power wash equipment you move into a new house
  • Maintain biosecurity to keep rodents and wild birds out of the poultry house
Crusty chicken legs from scaly-leg mites
Scaly-leg mites cause skin growth and crusts on the bird’s legs

There are a few species of scaly-leg mite that exist on a variety of birds including:

  • Chickens
  • Turkeys
  • Pheasants
  • Partridges
  • Many passerine birds

Knemidocoptes mutans is the mite most often found on older birds. It spends its entire life cycle on the bird’s skin.

Birds can spread mites through direct contact with other birds.

Mite life cycle

Female mites burrow into nonfeathered areas of the body, especially the scales of the legs but also the comb and wattles. Then they lay eggs for two months following burrowing. These eggs hatch and the mites mature.

Signs of mites

Feet of a scaly-leg mite infested chicken
Feet of a scaly-leg mite infested chicken
  • Skin growth and crusts on the legs
  • Lameness from heavy crusting on the leg
  • Toe loss
  • Decreased feed intake
  • Decreased egg production


You can treat your flock for scaly-leg mites by dipping the bird’s legs in dilute insecticide solution.

If you don’t use birds for eggs or meat, you can treat them with a drop of ivermectin solution on the comb or wattle. Repeat this treatment two weeks later.

Feather lice
White leghorn with feather lice with eggs along the feather shaft

Body lice are larger than mites and can build up in large numbers on affected birds, especially caged layers. Lice complete their full life cycle on the bird and can live for a few months. The lice that infect birds are chewing lice, not blood feeders.

Signs of lice

  • Decreased egg production
  • Decreased feed intake
  • Reduced body weights
  • Birds are uncomfortable
  • Ragged feathers

Treatment and prevention

Lice removed from chicken
Two types of lice found on a floor-raised laying hen

You can treat lice similar to Northern fowl mites but lice eggs are resistant to insecticides. Thus you must treat the birds again after two weeks to kill the lice that recently hatched. Be sure to treat the bird’s full body. In heavy lice infestations, the lice tend to spread from the vent to the neck.

Robert Porter, Extension poultry specialist