Species Guide
ðChickens Health Conditions
Layers, broilers, bantams, and heritage breeds
Chickens are the most commonly kept backyard poultry and also the most studied. Their conditions range from common parasitic infections and respiratory disease to reproductive disorders and neurological conditions. Many chicken illnesses progress quickly - early recognition matters.
75 vet-reviewed conditions documented for chickens.
Ascites (Water Belly) in Chickens
Ascites, commonly called water belly, is an accumulation of fluid in the abdominal cavity caused by right-sided heart failure and elevated pulmonary arterial pressure. It primarily affects fast-growing meat breeds (Cornish Cross) and high-altitude birds. The abdomen becomes visibly distended with yellow fluid. Prognosis is poor - most affected birds do not survive without drainage.
Aspergillosis (Brooder Pneumonia)
Aspergillosis is a fungal infection caused by Aspergillus fumigatus that primarily affects the respiratory system of young chicks (brooder pneumonia) and immunocompromised adult birds. It is not contagious bird-to-bird; instead, birds are infected individually by inhaling fungal spores from moldy bedding, feed, or hatchery equipment. There is no reliably effective treatment, making prevention through environmental management critical.
Avian Influenza
Avian influenza (AI) is caused by influenza A viruses and ranges from mild respiratory illness (LPAI) to sudden mass mortality (HPAI). Highly pathogenic avian influenza (HPAI) is a federally reportable disease in the United States. If you suspect HPAI, do not move birds or equipment, and call USDA APHIS immediately at 1-866-536-7593.
Avian Spirochetosis
Avian spirochetosis is caused by Borrelia anserina and transmitted by soft-bodied Argas persicus ticks (fowl tick). It causes fever, depression, diarrhea, and paralysis with high mortality in untreated flocks. It is most common in tropical and subtropical regions including the southern United States. Treatment with penicillin is highly effective if started early. Tick control is the primary prevention strategy.
Avian Tuberculosis
Avian tuberculosis (avian TB) is caused by Mycobacterium avium subspecies avium and produces a chronic wasting disease with nodular granulomas in the liver, spleen, intestines, and bone marrow. It primarily affects adult birds over 2 years old. There is no effective treatment. Infected birds should be culled, and the environment requires prolonged downtime because M. avium persists in soil for years. Zoonotic risk exists for immunocompromised individuals.
Blackhead Disease (Histomoniasis)
Blackhead disease (histomoniasis) is caused by the protozoan Histomonas meleagridis, transmitted through the eggs of cecal worms (Heterakis gallinarum). It causes severe liver necrosis and cecal inflammation with sulfur-yellow diarrhea. Turkeys are far more susceptible than chickens, but chickens serve as a carrier reservoir. Mortality in turkeys approaches 100% without treatment.
Botulism in Chickens (Limberneck)
Botulism in chickens is caused by Clostridium botulinum toxin ingested from rotting organic matter, dead animals, or spoiled feed. It causes progressive flaccid paralysis starting in the legs and working up to the neck, causing the characteristic 'limberneck' posture. It is often fatal but can be treated with antitoxin and supportive care if caught early.
Chicken Infectious Anemia
Chicken Infectious Anemia (CIA) is caused by Chicken Anemia Virus (CAV/Gyrovirus), a small DNA virus that destroys red blood cell precursors in the bone marrow and lymphocyte precursors in the thymus, causing profound anemia and immunosuppression in chicks 2-4 weeks of age. Breeder vaccination to produce maternal immunity in chicks is the primary control strategy.
Egg Binding
Egg binding in chickens occurs when a hen cannot pass an egg through the oviduct, often because of calcium deficiency, obesity, dehydration, an oversized egg, or weak muscle contractions. Affected hens strain, become lethargic, and may stand upright with a swollen abdomen. Warmth, humidity, and lubrication can help initially, but failure to pass the egg within a few hours requires emergency veterinary care.
Egg Yolk Peritonitis
Egg yolk peritonitis in chickens is inflammation and often bacterial infection within the abdomen after yolk material enters the body cavity. Hens develop a swollen fluid-filled abdomen, penguin posture, lethargy, breathing difficulty, and stopped egg production. Treatment requires veterinary antibiotics, pain control, and sometimes sterile drainage or hormonal suppression of laying.
Erysipelas in Chickens
Erysipelas is a bacterial disease of poultry caused by Erysipelothrix rhusiopathiae, a Gram-positive rod that affects turkeys most severely but also causes outbreaks in chickens. It presents as sudden death in apparently healthy birds, with comb and skin discoloration, septicemia, and cardiovascular involvement. It is zoonotic, causing erysipeloid skin infections in humans who handle infected carcasses. Penicillin is the treatment of choice.
Fowl Cholera
Fowl cholera is a bacterial disease caused by Pasteurella multocida that presents in two forms: peracute (sudden death with no prior signs) and chronic (swollen wattles, respiratory signs, joint infections). It is one of the most common infectious diseases of backyard and commercial poultry worldwide. Treatment with penicillin or oxytetracycline is effective, and vaccines are available for endemic operations.
Fowl Typhoid
Fowl typhoid is caused by Salmonella Gallinarum and differs from Pullorum disease (S. Pullorum) primarily in the age of birds affected: fowl typhoid kills adult chickens, while Pullorum kills chicks. Both are reportable under the NPIP. Signs include pale, anemic birds with green diarrhea and sudden death in adult laying flocks. Test-and-cull is the regulatory control approach.
Gangrenous Dermatitis
Gangrenous dermatitis is a rapidly progressive bacterial skin infection caused by Clostridium perfringens, C. septicum, and sometimes Staphylococcus aureus. It produces wet, dark necrosis of the skin and subcutaneous tissue, most commonly starting at the wing web, breast, or thigh. It is almost always associated with underlying immunosuppression from infectious bursal disease (IBD), chicken infectious anemia (CIA), or management failures. Mortality in affected birds is high without prompt antibiotic treatment.
Inclusion Body Hepatitis
Inclusion Body Hepatitis (IBH) is caused by Fowl Adenoviruses (FAdV), particularly serotypes FAdV-4 and FAdV-11, and produces sudden mortality of 3-6% in young broilers at 3-7 weeks of age from severe hepatitis. Pale, enlarged, fragile livers with petechial hemorrhages at necropsy are characteristic. Immunosuppression from co-infections (IBD, CIA) dramatically worsens outcomes. Breeder vaccination reduces vertical transmission.
Infectious Bronchitis
Infectious bronchitis (IB) is a highly contagious coronavirus that spreads through an entire flock within 24-48 hours. It causes respiratory signs in chicks, and sharp drops in egg production with watery whites and misshapen shells in laying hens. There is no curative treatment; vaccination and biosecurity are the primary control tools.
Infectious Laryngotracheitis
Infectious Laryngotracheitis (ILT) is caused by Gallid herpesvirus 1 and produces severe hemorrhagic tracheitis with gasping, blood-streaked mucus, and characteristic 'pump-handle' breathing as birds attempt to clear obstructed airways. Mortality can reach 70% in susceptible flocks without vaccination. Vaccination is available and effective, but vaccine virus can persist and cause disease in unvaccinated contacts.
Internal Laying
Internal laying (ectopic ovulation or reverse peristalsis) occurs when the ovulated yolk is deposited into the abdominal cavity instead of the oviduct. This leads to accumulation of egg material in the coelom, triggering an inflammatory response (egg yolk coelomitis/peritonitis) that is often fatal if untreated. It is distinct from but closely related to egg yolk peritonitis, which is the infectious complication of internal laying.
Lash Egg in Chickens (Salpingitis)
A lash egg is a mass of caseous (cheese-like) material expelled from the oviduct as a result of salpingitis - a bacterial infection of the oviduct. It is not a real egg but a layered mass of inflammatory material, pus, and sometimes yolk or albumen remnants. Finding a lash egg means the hen has an active reproductive tract infection that requires prompt veterinary evaluation.
Marek's Disease
Marek's disease in chickens is a contagious herpesvirus infection spread in feather dander that can cause paralysis, tumors, abnormal pupils, weight loss, and death. There is no cure once clinical disease develops, so care is supportive and severely affected birds may require humane euthanasia. Vaccination at hatch and protected brooding during early immunity are the primary controls.
Mycotoxicosis (Mold Toxins)
Mycotoxicosis results from consuming feed contaminated with fungal toxins (mycotoxins), primarily aflatoxins, ochratoxin A, T-2 toxin, fumonisin, and zearalenone. These toxins cause dose-dependent damage to the liver, kidneys, immune system, and reproductive organs. The condition is particularly insidious because feed may appear and smell normal despite significant mycotoxin contamination. Prevention through proper feed storage and quality sourcing is the primary control strategy.
Newcastle Disease in Chickens
Newcastle Disease (ND) is a highly contagious viral infection of poultry caused by Newcastle Disease Virus (NDV), a paramyxovirus with strains ranging from mild to rapidly fatal. Virulent strains (Velogenic NDV) are federally reportable in the United States and can kill an entire flock within days. Clinical signs include respiratory distress, neurological deficits, greenish diarrhea, and a sudden collapse in egg production. There is no cure; outbreak management relies on vaccination, biosecurity, and regulatory response.
Omphalitis (Navel Ill) in Chicks
Omphalitis, also called navel ill or mushy chick disease, is an infection of the navel and yolk sac in newly hatched chicks caused by bacterial contamination at or before hatch. It is a leading cause of mortality in chicks under 7 days old, responsible for up to 10% of hatchery deaths in poorly managed operations. The unhealed navel provides a direct bacterial entry point, and E. coli is the most common pathogen isolated.
Polymelia (Extra Limbs)
Polymelia in chickens is a rare congenital defect in which a chick develops one or more extra limbs during embryonic growth. The additional limb may be harmless or may impair walking, develop sores, or attract flock pecking. Management is based on quality of life, with veterinary surgical removal considered when the limb causes injury or disability.
Prolapsed Vent (Blowout)
Vent prolapse in chickens occurs when cloacal tissue protrudes through the vent after excessive straining, often during egg laying. It appears as a swollen red or pink mass and can rapidly worsen through drying, trauma, or flock pecking. Immediate isolation, gentle cleaning, swelling reduction, and careful replacement are needed, with veterinary help if the tissue cannot be reduced.
Pullorum Disease
Pullorum disease is caused by Salmonella Pullorum and primarily kills chicks in the first 2-3 weeks of life through bloody or white pasty diarrhea, weakness, and respiratory distress. It is a federally reportable condition in the United States under the National Poultry Improvement Plan (NPIP). Adult birds can be lifelong carriers without showing any signs. Test-and-cull is the regulatory control method.
Salpingitis in Chickens
Salpingitis is a bacterial infection of the oviduct, most commonly caused by Escherichia coli. It causes cessation of egg production, passage of caseous lash eggs, and penguin-like posture from abdominal distension. Without treatment, it progresses to egg yolk peritonitis and death. Treatment involves antibiotics and, for chronic cases, surgical spay (salpingohysterectomy).
Sudden Death Syndrome (Flip-Over Disease)
Sudden Death Syndrome (SDS), also called flip-over disease, is a metabolic cardiac condition in which otherwise healthy, fast-growing broiler chickens die suddenly. Birds are found on their backs with legs extended, having died during a cardiac arrhythmia. It most commonly affects males at 2-4 weeks of age. There is no treatment. Dietary and management strategies can reduce incidence.
Air Sacculitis
Air sacculitis is inflammation and infection of the air sacs, the large transparent membrane-lined spaces that connect to the lungs and allow air flow through the bird's respiratory system. It is almost always a secondary condition: Mycoplasma gallisepticum or infectious bronchitis virus damages the air sac lining, then E. coli or other bacteria colonize the compromised sacs. Treatment targets both the primary pathogen and the secondary bacterial infection.
Avian Metapneumovirus (Swollen Head Syndrome)
Avian metapneumovirus (aMPV) causes respiratory disease and, in chickens, Swollen Head Syndrome (SHS) when secondary E. coli infection spreads from the upper respiratory tract to the subcutaneous tissues of the head. In turkeys it causes Turkey Rhinotracheitis (TRT). There is no specific treatment; vaccination reduces severity and spread.
Bumblefoot (Plantar Pododermatitis)
Bumblefoot in chickens is bacterial pododermatitis, usually caused when Staphylococcus aureus enters a cut or pressure injury in the footpad. Typical signs are footpad redness, swelling, limping, and a dark central scab. Mild cases need cleaning, topical antiseptic, and bandaging, while deep abscesses require veterinary debridement and sometimes systemic antibiotics.
Cage Layer Fatigue (Osteoporosis)
Cage layer fatigue (CLF) is a metabolic bone disease of high-producing laying hens caused by progressive calcium depletion from the skeleton to maintain eggshell production. Hens in peak production can lay eggs for months with declining bone density before sudden paralysis, fractures, or death from hypocalcemia occur. Adequate dietary calcium, vitamin D3, and exercise opportunities are the primary preventive measures.
Chicken Eye Infection (Conjunctivitis)
Eye infections in chickens range from bacterial conjunctivitis to viral disease and Mycoplasma. They present as swollen, watery, or crusty eyes and require prompt treatment to prevent blindness. The most common cause in backyard flocks is Mycoplasma gallisepticum, often triggered by respiratory illness.
Coccidiosis
Coccidiosis in chickens is an intestinal disease caused by Eimeria protozoa acquired from contaminated litter, feed, water, or soil. It commonly causes bloody or watery diarrhea, lethargy, pale combs, poor growth, and sudden death in chicks. Prompt treatment with amprolium in drinking water, plus hydration and dry litter, is the standard response.
Diarrhea in Chickens
Diarrhea in chickens is loose, watery, or discolored stool that persists beyond normal cecal droppings. It can stem from dietary changes, bacterial or viral infections, intestinal parasites, or stress. Mild cases often resolve with supportive care, while persistent or bloody diarrhea requires veterinary diagnosis to identify and treat the underlying cause.
Egg Drop Syndrome
Egg Drop Syndrome 76 (EDS-76) is caused by an avian adenovirus (Duck Adenovirus A) that produces a sudden drop in egg production with thin-shelled, soft-shelled, or shell-less eggs in otherwise healthy laying hens. Broiler breeders and brown egg-laying strains are most susceptible. The primary reservoir is waterfowl. There is no treatment; vaccination protects against production losses.
Egg Production Problems in Chickens
Egg production problems include a sudden stop, gradual decline, or consistently low output in laying hens. Common causes include insufficient daylight, nutritional deficiencies, molt, age, disease, and management stress. Identifying and correcting the primary trigger usually restores production within 2-6 weeks.
Fatty Liver Hemorrhagic Syndrome (FLHS)
Fatty liver syndrome in chickens is a metabolic disorder in which excessive fat makes the liver enlarged, fragile, and prone to fatal hemorrhage. It mainly affects high-producing, overweight hens fed energy-dense diets and may cause reduced laying, pale combs, weakness, or sudden death. Management focuses on balanced nutrition, weight control, exercise, and veterinary assessment of sick hens.
Feather Pecking and Cannibalism
Feather pecking in chickens is damaging behavior in which birds pull or eat flock mates' feathers, and severe cases can progress to skin injury and cannibalism. Common triggers include crowding, excessive light, boredom, stress, and inadequate dietary protein. Treatment removes injured birds, corrects the trigger, adds enrichment, and may use an anti-pecking spray to protect wounds.
Fowl Pox
Fowl pox in chickens is a mosquito-borne or contact-spread Avipoxvirus infection that causes crusted skin lesions or plaques in the mouth and throat. Dry pox usually causes scabs on unfeathered skin, while wet pox can obstruct eating or breathing. There is no antiviral cure, so treatment is supportive and vaccination is used to protect unaffected birds at risk.
Gapeworms
Gapeworm in chickens is a Syngamus trachea roundworm infestation of the trachea acquired by eating infective larvae or carrier hosts such as earthworms and slugs. Birds gape, cough, shake the head, stretch the neck, and may suffocate when worm burdens are heavy. Treatment requires a veterinary-directed anthelmintic such as fenbendazole plus repeat dosing and range management.
Heat Stress
Heat stress in chickens is dangerous overheating caused when environmental heat and humidity exceed a bird's ability to cool itself by panting. Signs progress from open-beak panting and lifted wings to lethargy, collapse, seizures, and death. Emergency treatment is immediate shade, airflow, cool water, and electrolytes, followed by veterinary care if the bird does not respond quickly.
Impacted Crop
Crop impaction in chickens is a blockage of compacted feed, grass, string, or other fibrous material that prevents the crop from emptying. The crop remains enlarged and firm after an overnight fast, and the bird may lose appetite, weight, and energy. Early care uses hydration and gentle massage, while persistent obstruction requires veterinary removal.
Infectious Coryza
Infectious coryza is a bacterial upper respiratory disease caused by Avibacterium paragallinarum. It is recognized by swelling around the face and sinuses, a foul-smelling sticky nasal discharge, and rapid spread through the flock within 1-2 days. Treatment with sulfonamides or other antibiotics is effective, but recovered birds remain permanent carriers.
Limping Chicken (Lameness)
Limping in chickens is a symptom with many possible causes including bumblefoot, Marek's disease, gout, injury, and infectious arthritis. Identifying the cause is essential because treatments differ significantly. Single-bird lameness with no other signs usually indicates a local injury or bumblefoot.
Mycoplasma in Chickens (MG and MS)
Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are the two most economically important mycoplasma infections in backyard and commercial poultry. MG causes chronic respiratory disease with rattling, nasal discharge, and eye swelling. MS causes infectious synovitis with swollen joints. Both establish lifelong carrier status in the flock.
Mycoplasma Synoviae
Mycoplasma synoviae (MS) causes two distinct syndromes in chickens: infectious synovitis (joint swelling and lameness from synovial membrane infection) and upper respiratory tract disease (mild, often subclinical). MS is also increasingly associated with eggshell apex abnormalities, reducing hatching egg quality. It is transmitted vertically through eggs and horizontally through respiratory secretions. Antibiotics manage but do not eliminate infection.
Northern Fowl Mites
Northern fowl mites in chickens are blood-feeding Ornithonyssus sylviarum parasites that live continuously on the bird, especially around the vent. They cause irritation, dark feather debris, anemia, pale combs, reduced laying, and weakness. Control requires treating every bird with an approved poultry product and repeating treatment after newly hatched mites emerge.
Pasty Butt in Chicks
Pasty butt (pasting up) is a condition in which soft droppings accumulate and harden over the vent of a young chick, blocking excretion. Left untreated, it is fatal within 24-48 hours. It is most common in chicks 1-7 days old and is triggered by temperature stress, shipping stress, or improper diet.
Pendulous Crop
Pendulous crop (also called flaccid or stretched crop) occurs when the crop loses its muscular tone and hangs abnormally low on the chest, failing to empty properly overnight. It is a mechanical problem distinct from sour crop (infection) and impacted crop (blockage). Mild cases are managed with dietary modification; severe cases may require surgical crop reduction.
Perosis (Slipped Tendon)
Perosis, commonly called slipped tendon, occurs when the gastrocnemius tendon slips from its groove at the hock joint due to abnormal cartilage development, leaving the bird unable to walk. It is primarily caused by manganese deficiency, though choline, biotin, folate, zinc, and niacin deficiencies can also contribute. Early cases may be corrected manually; advanced cases leave permanent deformity.
Poultry Mites
Poultry mites are blood-feeding external parasites, including northern fowl mites that remain on birds and red mites that hide in the coop by day. They cause irritation, dark debris near the vent, pale combs, anemia, reduced production, and weakness. Effective treatment targets every bird and the environment at the same time, then repeats on the product schedule.
Poultry Red Mite
Red mites in chickens are nocturnal blood-feeding parasites that hide in coop cracks and roost fittings during daylight. Infestations cause nighttime restlessness, anemia, pale combs, reduced production, and dark or red smears on nighttime inspections. Elimination requires simultaneous treatment of birds and the entire coop, repeated to break the mite life cycle.
Respiratory Infections
Respiratory infections in chickens are diseases of the airways caused by organisms such as Mycoplasma, infectious bronchitis virus, Newcastle disease virus, or Aspergillus fungi. Common signs include sneezing, wheezing, nasal discharge, swollen eyes, reduced laying, and open-mouth breathing. Treatment depends on the cause, with supportive care for viral disease, targeted antibiotics for susceptible bacterial disease, and urgent reporting when Newcastle disease is suspected.
Rickets in Chickens
Rickets in chickens is a metabolic bone disease caused by deficiency of vitamin D3, calcium, or phosphorus, or an incorrect calcium-to-phosphorus ratio. It primarily affects growing chicks and causes soft, rubbery bones, leg deformities, and poor feathering. Treatment is supplementation with the deficient nutrient, and most birds recover if caught before permanent deformity sets in.
Salmonella in Chickens
Salmonella encompasses hundreds of serovars with different impacts on chickens and humans. Most paratyphoid serovars (S. Enteritidis, S. Typhimurium) colonize chickens silently but cause foodborne gastroenteritis in humans through contaminated eggs and meat. Salmonella Pullorum and Gallinarum cause reportable poultry diseases under the National Poultry Improvement Plan (NPIP). Backyard flock owners need to understand both the flock health and food safety dimensions.
Sinusitis in Chickens
Sinusitis in chickens is an infection of the infraorbital sinus, the large air-filled cavity located below and slightly in front of each eye. The most common cause is Mycoplasma gallisepticum (MG), often in combination with secondary bacterial pathogens. It produces visible swelling of the face below the eye, nasal discharge, and rattling breathing. Treatment requires antibiotics targeting Mycoplasma and, in chronic cases, manual removal or flushing of accumulated caseous material.
Soft Shell Eggs in Chickens
Soft shell or shell-less eggs occur when the oviduct cannot deposit sufficient calcium carbonate around the developing egg. The most common cause is calcium deficiency or poor calcium-to-vitamin D ratio in the diet. Infectious causes including Infectious Bronchitis and Newcastle Disease also damage the shell gland and produce characteristic abnormal shells.
Sour Crop (Candidal Ingluvitis)
Sour crop in chickens is delayed crop emptying with yeast or bacterial overgrowth, often involving Candida after diet disruption, antibiotics, or another crop disorder. The crop remains soft and fluid-filled in the morning, and the bird may have sour breath, poor appetite, and weight loss. Treatment corrects the underlying stasis, restores hydration and gut flora, and uses veterinary antifungal medication when candidiasis is confirmed.
Spraddle Leg in Chicks
Spraddle leg (also called splay leg) is a developmental deformity in newly hatched chicks in which one or both legs slide outward and cannot be held under the body for walking. It results from slippery incubation or brooder surfaces, nutritional deficiencies in the breeding flock, or incubation errors. Most mild to moderate cases can be corrected within 24-72 hours using a simple leg brace made from medical tape or a bandage.
Swollen Eye in Chickens
A swollen eye in a chicken can result from Mycoplasma gallisepticum (MG), Chronic Respiratory Disease (CRD), a peck injury, Infectious Coryza, vitamin A deficiency, or sinus infection. The pattern of involvement (one eye vs. both, with or without respiratory signs, degree of pus) guides the diagnosis. Most causes respond well to treatment if started within the first few days of signs.
Tibial Dyschondroplasia
Tibial dyschondroplasia (TD) is a skeletal disorder of young, fast-growing chickens in which abnormal cartilage accumulates in the growth plate of the proximal tibiotarsus, forming a plug of avascular, non-calcifying cartilage that cannot convert to bone. This weakens the leg, causing bowing, twisting, or fracture. It is strongly associated with rapid growth, nutritional imbalances, and certain feed acidifiers.
Vent Gleet
Vent Gleet is chronic cloacal dysbiosis - a persistent imbalance of the microbial environment in the cloaca and vent area. It presents as foul-smelling discharge, pasty feathers around the vent, and progressive weight loss. Most online resources treat it as a hygiene problem. It isn't. It's a systemic imbalance that requires addressing the root cause.
Wry Neck (Torticollis)
Wry neck in chickens is torticollis, a neurological sign in which the head twists sideways or backward because of nutritional deficiency, injury, toxin exposure, or disease. Birds may stargaze, lose balance, and struggle to eat or drink. Treatment addresses the cause, commonly with carefully dosed vitamin E and selenium support plus protected feeding and veterinary evaluation.
Breast Blister (Keel Bursitis)
Breast blister is a contact bursitis causing a fluid-filled or fibrous swelling over the keel (sternum) bone of chickens from pressure on hard, wet, or abrasive litter. It ranges from a small, clear fluid blister (Grade 1) to large, fibrous, discolored masses (Grade 3). The condition is primarily a welfare and meat quality issue in broilers and a management concern in backyard flocks.
Broody Hen
Broodiness is a normal hormonal state in which a hen stops laying and sits persistently on a nest to incubate eggs. It is triggered by prolactin and shortened daylength, and is not a disease. Management ranges from breaking the broody cycle to allowing her to hatch eggs.
Campylobacter in Chickens
Campylobacter jejuni and C. coli are the leading bacterial causes of gastroenteritis in humans worldwide, and chickens are the primary reservoir. Most chickens carry Campylobacter in their intestines without showing any signs of illness. The primary risk is to humans who handle birds or consume undercooked poultry. Backyard flock owners must understand hygiene protocols to prevent transmission.
Chicken Fleas (Sticktight Fleas)
Chicken fleas, primarily the sticktight flea (Echidnophaga gallinacea), embed their mouthparts into bare skin around the eyes, comb, wattles, and vent of chickens and remain attached for days to weeks. Unlike most fleas, they do not jump. Heavy infestations cause anemia, ulcerative wound formation, secondary bacterial infection, and death in chicks. Treatment involves manual removal and permethrin application.
Chicken Lice
Chicken lice are host-specific chewing insects that live on poultry and feed on feathers, skin scales, and debris. Infested birds scratch, lose feather quality, and carry fast-moving tan insects or pale egg clusters near feather bases. Treatment requires an approved poultry insecticide on every bird, repeated after eggs hatch, along with cleaning of nest and dust-bath areas.
Depluming Mites
Depluming mites (Knemidocoptes laevis) burrow into the skin at the base of feathers, causing intense irritation that leads to self-plucking and feather loss. Unlike scaly leg mites (K. mutans), depluming mites affect the feathered body surface rather than the legs. Ivermectin or lime sulfur dips are the primary treatments. Affected birds must be isolated from the flock to prevent spread.
Frostbite
Frostbite in chickens is freezing injury to exposed tissue, most often the comb, wattles, toes, and feet in cold, damp conditions. Tissue first appears pale or gray, then becomes swollen and may turn black as it dies. Treatment uses gradual warming and protection from refreezing, while blackened or infected tissue requires veterinary assessment.
Internal Parasites (Worms)
Worms in chickens are internal helminth parasites acquired from contaminated ground or intermediate hosts such as insects, earthworms, and slugs. Heavy burdens can cause weight loss, diarrhea, pale combs, reduced laying, visible worms, or respiratory gaping. Fecal testing identifies the parasite, and treatment uses a veterinary-selected dewormer with flock-wide environmental control.
Molting (Feather Loss)
Molting in chickens is the normal replacement of old feathers with new plumage, usually triggered by shorter daylight in late summer or fall. Birds lose feathers in a recognizable pattern, stop or reduce laying, and need extra dietary protein while feathers regrow. It requires supportive nutrition and low stress, not medical treatment, unless feather loss is caused by parasites or disease.
Scaly Leg Mites
Scaly leg mites in chickens are Knemidocoptes mites that burrow beneath leg and foot scales. Infested legs become raised, crusty, thickened, painful, and sometimes deformed. Treatment smothers or kills the mites over repeated applications, with veterinary ivermectin guidance for heavy cases and cleaning to limit spread.
Why Did My Chicken Stop Laying?
A chicken stops laying eggs when her body redirects resources away from reproduction in response to reduced light, molt, nutritional gaps, stress, aging, or disease. Most causes are correctable. Identifying whether the stoppage is flock-wide or individual and whether it coincides with seasonal or management changes points to the cause within minutes of observation.