A complete veterinary pharmacy guide to the 25 most important diseases of poultry — respiratory, viral and bacterial — covering the clinical signs, transmission routes, treatment options and prevention strategies that matter on the farm.
01Respiratory disease in poultry
There are many common and important diseases which can affect the respiratory system (air passages, lungs, air sacs) of poultry. Poultry refers to birds that people keep for their use — generally including chicken, turkey, duck, goose, quail, pheasant, pigeon, guinea fowl, pea fowl, ostrich, emu and rhea. Due to modern systems of management, usually with high poultry densities, these diseases are able to readily spread.
The sections below cover the eleven most important respiratory diseases of poultry — from fowl pox and Newcastle disease to aspergillosis — along with their synonyms, species affected, clinical signs, transmission routes, treatment and prevention.
02Fowl pox
Synonyms
Chicken pox (not to be confused with chicken pox in humans; the human disease does not affect poultry and vice versa), sore head, avian diphtheria, bird pox.
Species affected
Most poultry — chickens, turkeys, pheasants, quail, ducks, psittacine and ratites of all ages are susceptible.
Clinical signs
There are two forms of fowl pox. The dry form is characterized by raised, wart-like lesions on unfeathered areas (head, legs, vent, etc.). The lesions heal in about 2 weeks. If the scab is removed before healing is complete, the surface beneath is raw and bleeds. Unthriftiness and retarded growth are typical symptoms. In laying hens, infection results in a transient decline in egg production.
In the wet form, there are canker-like lesions in the mouth, pharynx, larynx and trachea. The wet form may cause respiratory distress by obstructing upper air passages. Chickens may be affected with either or both forms of fowl pox at one time.
Transmission
Fowl pox is transmitted by direct contact between infected and susceptible birds or by mosquitoes. The virus can enter the blood stream through the eye, skin wounds or respiratory tract. Mosquitoes become infected from feeding on birds with fowl pox in their blood stream. Mosquitoes are the primary reservoir and spreaders of fowl pox on poultry ranges.
Treatment
No treatment is available. However, fowl pox is relatively slow-spreading, so it is possible to vaccinate to stop an outbreak.
Prevention
Fowl pox outbreaks in poultry confined to houses can be controlled by spraying insecticides to kill mosquitoes. However, if fowl pox is endemic in an area, vaccination is recommended.
03Newcastle disease
Synonyms
Pneumoencephalitis — caused by a paramyxovirus. Includes viscerotropic velogenic Newcastle disease, exotic Newcastle disease and Asiatic Newcastle disease.
Species affected
Newcastle disease affects all birds of all ages. Humans and other mammals are also susceptible. In such species, it causes a mild conjunctivitis.
Clinical signs
There are three forms of Newcastle disease — mildly pathogenic (lentogenic), moderately pathogenic (mesogenic) and highly pathogenic (velogenic). Newcastle disease is characterized by a sudden onset of clinical signs which include hoarse chirps (in chicks), watery discharge from nostrils, laboured breathing (gasping), facial swelling, paralysis, trembling, and twisting of the neck (a sign of central nervous system involvement).
Transmission
Newcastle virus can be transmitted via short distances by the airborne route or introduced on contaminated shoes, caretakers, feed deliverers, visitors, tires, dirty equipment, feed sacks, crates and wild birds. In live birds, the virus is shed in body fluids, secretions, excreta and breath.
Treatment
There is no specific treatment for Newcastle disease. Antibiotics can be given for 3–5 days to prevent secondary bacterial infections (particularly E. coli).
Prevention
Prevention programs should include vaccination, good sanitation and implementation of a comprehensive biosecurity program. Live lentogenic virus vaccines are widely used and typically administered to poultry by mass application in drinking water or by spray. Oil-adjuvanted inactivated virus vaccines are also used after live virus vaccine in breeders and layers. They may be used alone in situations where live virus may be contraindicated (e.g., in pigeons).
04Infectious bronchitis
Synonyms
Bronchitis, cold.
Species affected
Infectious bronchitis is a disease of chickens only. A similar disease occurs in bobwhite quail (quail bronchitis), but it is caused by a different virus.
Clinical signs
The severity of infectious bronchitis infection is influenced by the age and immune status of the flock, by environmental conditions, and by the presence of other diseases. Affected chickens will be chirping, with a watery discharge from the eyes and nostrils, and laboured breathing with some gasping in young chickens. Breathing noises are more noticeable at night while the birds rest. The infectious bronchitis virus infects many tissues of the body, including the reproductive tract. Eggshells become rough and the egg white becomes watery.
Transmission
Infectious bronchitis is a very contagious poultry disease. It is spread by air, feed bags, infected dead birds, infected houses and rodents.
Treatment
There is no specific treatment for infectious bronchitis. Antibiotics for 3–5 days may aid in combating secondary bacterial infections. Raise the room temperature 5°F for brooding-age chickens until symptoms subside.
Prevention
Establish and enforce a biosecurity program. Vaccinations are available.
05Quail bronchitis
Synonyms
None.
Species affected
Bobwhite quail are affected; Japanese coturnix quail are resistant.
Clinical signs
Respiratory distress occurs with tracheal rales (rattles), sneezing and coughing. Feed and water consumption declines dramatically. There can be conjunctivitis (inflammation of the eye). Loose watery faeces are seen in older and sub-acutely affected birds. Nasal discharges are not seen, differentiating quail bronchitis from similar diseases.
Transmission
Bronchitis is highly contagious and can spread quickly. The virus spreads through the air and on feed bags, infected dead birds and rodents. The virus can also be transmitted through the egg to developing embryos, but an affected embryo typically does not hatch. Once infected, quail bronchitis remains on the farm for the duration of the breeding season, infecting each successive brood.
Treatment
There is no specific treatment against quail bronchitis. Quail bronchitis infections are often complicated by concurrent mycoplasma infections. Antibiotics can be used to combat secondary infections.
Prevention
There is no commercial vaccine in the market. It is necessary to break the cycle by depopulating and thoroughly cleaning and disinfecting pens and equipment, followed by a 30–90 day quarantine of the facilities.
06Avian influenza
Synonyms
Flu, influenza, fowl plague.
Species affected
Avian influenza can occur in most, if not all, species of birds.
Clinical signs
Avian influenza is categorized as mild or highly pathogenic. The mild form produces listlessness, loss of appetite, respiratory distress and diarrhoea. The highly pathogenic form produces facial swelling, blue comb and wattles, and dehydration with respiratory distress. Dark red/white spots develop in the legs and combs of chickens. There can be blood-tinged discharge from the nostrils. Mortality can range from low to near 100 percent.
Transmission
The avian influenza virus can remain viable for long periods of time at moderate temperatures and can live indefinitely in frozen material. As a result, the disease can be spread through improper disposal of infected carcasses and manure. Avian influenza can be spread by contaminated shoes, clothing, crates and other equipment. Insects and rodents may mechanically carry the virus from infected to susceptible poultry.
Treatment
There is no effective treatment for avian influenza. With the mild form of the disease, good husbandry, proper nutrition and broad spectrum antibiotics may reduce losses from secondary infections. Recovered flocks continue to shed the virus.
Prevention
A vaccination program used in conjunction with a strict quarantine has been used to control mild forms of the disease. With the more lethal forms, strict quarantine and rapid destruction of all infected flocks remains the only effective method of stopping an avian influenza outbreak.
Avian influenza is a notifiable zoonosis. Suspected outbreaks must be reported to veterinary authorities immediately. Do not attempt to treat or cull birds without official guidance.
07Infectious coryza
Synonyms
Roup, cold, coryza.
Species affected
Chickens, pheasants and guinea fowl.
Clinical signs
Swelling around the face, foul-smelling thick sticky discharge from the nostrils and eyes, laboured breathing and rales (rattles — an abnormal breathing sound) are common clinical signs. The eyelids are irritated and may stick together. The birds may have diarrhoea and growing birds may become stunted. Mortality from coryza is usually low, but infections can decrease egg production and increase the incidence and/or severity of other diseases.
Transmission
Coryza is primarily transmitted by direct bird-to-bird contact. This can be from infected birds brought into the flock as well as from birds which recover from the disease and remain carriers of the organism — they may shed intermittently throughout their lives. Birds risk exposure at poultry shows, bird swaps and live-bird sales. Within a flock, inhalation of airborne respiratory droplets and contamination of feed and/or water are common modes of spread.
Treatment
Water-soluble antibiotics or antibacterials can be used. Sulfadimethoxine is the preferred treatment. If it is not available, or not effective, sulfamethazine, erythromycin or tetracycline can be used as alternative treatments.
Prevention
Good management and sanitation are the best ways to avoid infectious coryza. Most outbreaks occur as a result of mixing flocks. All replacement birds on "coryza-endemic" farms should be vaccinated. Each chicken should be vaccinated four times, starting at 5 weeks of age with at least 4 weeks between injections. Vaccinate again at 10 months of age and twice yearly thereafter.
08Infectious laryngotracheitis (LT)
Species affected
Chickens and pheasants are affected by LT. Chickens 14 weeks and older are more susceptible than young chickens. Most LT outbreaks occur in mature hens.
Clinical signs
The clinical sign usually first noticed is watery eye. Affected birds remain quiet because breathing is difficult. Coughing, sneezing and shaking of the head to dislodge exudate plugs in the windpipe follow. Birds extend their head and neck to facilitate breathing (commonly referred to as "pump handle respiration"). Inhalation produces a wheezing and gurgling sound.
Transmission
LT is spread by the respiratory route. LT is also spread from flock to flock by contaminated clothing, shoes, tires, etc. Birds that recover should be considered carriers for life.
Treatment
Incinerate dead birds, administer antibiotics to control secondary infection, and vaccinate the flock.
Prevention
Vaccinate replacement birds for outbreak farms. Vaccination for LT is not as successful as for other diseases, but is an excellent preventive measure for use in outbreaks and in epidemic areas.
09Turkey rhinotracheitis
Species affected
Turkeys of all ages are susceptible, but the disease is most severe in young poults. Chickens are susceptible to the virus, but waterfowl and pigeons are resistant.
Clinical signs
Respiratory signs in poults include snicking, rales, sneezing, nasal exudates, foamy conjunctivitis and sinusitis.
Transmission
Spread is primarily by contact with contaminated environments, feed and water, recovered birds, equipment and personnel.
Treatment
No drugs are available to combat the virus. Antibiotic therapy is recommended to control secondary bacterial infections.
Prevention
No vaccines are currently available. Prevention is dependent on a comprehensive biosecurity program.
10Chlamydiosis
Synonyms
Ornithosis, psittacosis, parrot fever. The disease was called psittacosis or parrot fever when diagnosed in psittacine (curve-beaked) birds, and called ornithosis when diagnosed in all other birds or in humans.
Species affected
Affected species include turkeys, pigeons, ducks, psittacine (curve-beaked) birds, captive and aviary birds. Chickens are not commonly affected.
Clinical signs
Clinical signs in most birds include nasal-ocular discharge, conjunctivitis, sinusitis, diarrhoea, weakness, loss of body weight and a reduction in feed consumption. In turkeys there is also respiratory distress and loose yellow to greenish-yellow coloured droppings.
Transmission
The primary means of transmission is through inhalation of faecal dust and respiratory tract secretions. It can also be transmitted through contaminated clothing and equipment. Recovered birds remain carriers and will continue to intermittently shed the infective agent for long periods after clinical signs have subsided.
Treatment
Chlortetracycline can be given in the feed (200–400 g/ton) for 3 weeks. Other antibiotics are usually ineffective.
Prevention
There is no vaccine. Have a good biosecurity program, excluding wild birds as much as possible.
Chlamydiosis is transmissible to humans (parrot fever). Wear protective equipment when handling suspect birds, and consult a physician if flu-like symptoms develop after exposure.
11Swollen head syndrome (SHS)
Species affected
Chickens and turkeys are the known natural hosts, but pigeons, ducks and geese are resistant to the infection.
Clinical signs
In chicks and poults, there is initial sneezing, followed by reddening and swelling of the tear ducts and eye tissue. Facial swelling will extend over the head and down the jaw and wattles. Adult chickens have mild respiratory disease followed by a few birds having swollen heads. Other signs include disorientation, twisting of the neck and a significant drop in egg production.
Transmission
The infection spreads by direct contact with infected birds or indirectly by exposure to infectious material.
Treatment
There is no proven medication for swollen head syndrome.
Prevention
A commercial vaccine is available. Swollen head syndrome is considered an exotic disease and a live vaccine is not approved for use in the United States.
12Aspergillosis
Synonyms
Brooder pneumonia, mycotic pneumonia, fungal pneumonia, Aspergillus. When the source of the disease is the hatchery, the disease is called brooder pneumonia. In older birds, the disease is called aspergillosis.
Species affected
All birds (domestic poultry, pigeons, canary and zoo bird species).
Clinical signs
Aspergillosis occurs as an acute disease of young birds and a chronic disease in matured birds. Young birds have trouble breathing and gasp for air. Characteristically, there are no rales or respiratory sounds associated with aspergillosis. Occasionally there is paralysis or convulsions caused by the fungal toxin. Matured birds also have respiratory distress, reduced feed consumption, and may have a bluish and dark colour of the skin (cyanosis). Nervous disorders, such as twisted necks, may occur in a few birds.
Transmission
Aspergillosis is caused by a fungus. The fungus grows well at room temperature and higher. All litter and nest materials (peat moss, peanut hulls, sawdust, peat, bark, straw) have been known to have been contaminated with Aspergillus. Feed and water should be examined when attempting to identify the source of contamination.
Treatment
There is no cure for infected birds. The spread can be controlled by improving ventilation, eliminating the source of the infection, and adding a fungistat (mycostatin, mold curb, sodium or calcium propionate, or gentian violet) to the feed and/or copper sulfate or acidified copper in the drinking water for 3 days.
Prevention
It is important to thoroughly clean and disinfect the brooding area between broods.
13Viral diseases (non-respiratory)
Not all poultry viruses target the respiratory tract. The seven diseases below affect the nervous system, immune system, reproductive system or the joints — and several are among the most economically damaging conditions in commercial poultry.
14Marek's disease
Species affected
Chickens between 12 and 25 weeks of age are most commonly infected. Occasionally pheasants, quail, game fowl and turkeys can be infected.
Clinical signs
Marek's disease is a type of avian cancer. Tumours in nerves cause lameness and paralysis. Tumours can occur in the eyes and cause irregularly shaped pupils and blindness. Tumours of the liver, kidney, spleen, gonads, pancreas, proventriculus, lungs, muscles and skin can cause incoordination, unthriftiness, paleness, weak laboured breathing and enlarged feather follicles. In terminal stages, the birds are emaciated with pale, scaly combs and greenish diarrhoea.
Transmission
Marek's virus is transmitted by air within the poultry house. It is in feather dander, chicken house dust, faeces and saliva. Infected birds carry the virus in their blood for life and are a source of infection for susceptible birds.
Treatment
None.
Prevention
Chicks can be vaccinated at the hatchery. While the vaccination prevents tumour formation, it does not prevent infection by the virus.
15Lymphoid leukosis
Species affected
Primarily a disease of chickens.
Clinical signs
The virus involved has a long incubation period (4 months or longer). As a result, clinical signs are not noticeable until the birds are 16 weeks or older. Affected birds become progressively weaker and emaciated. There is regression of the comb. The abdomen becomes enlarged. Greenish diarrhoea develops in terminal stages.
Transmission
The virus is transmitted through the egg to offspring. Within a flock, it is spread by bird-to-bird contact and by contact with contaminated environments. The virus is not spread by air. Infected chickens are carriers for life.
Treatment
None.
Prevention
The virus is present in the yolk and egg white of eggs from infected hens. Most national and international layer breeders have eradicated lymphoid leukosis from their flocks. Most commercial chicks are lymphoid leukosis negative because they are hatched from LL-free breeders. The disease is still common in broiler breeder flocks.
16Infectious bursal disease (Gumboro)
Synonyms
Gumboro, IBD, infectious bursitis, infectious avian nephrosis.
Species affected
Chickens.
Clinical signs
In affected chickens greater than 3 weeks of age, watery droppings lead to soiling of feathers around the vent, and vent pecking. Feathers appear ruffled. Chicks are listless and sit in hunched positions. Chickens infected when less than 3 weeks of age do not develop clinical disease, but become severely and permanently immunosuppressed.
Transmission
The virus is spread by bird-to-bird contact, as well as by contact with contaminated people and equipment. The virus is shed in the bird droppings and can be spread by air on dust particles.
Treatment
There is no specific treatment. Antibiotics, sulfonamides and nitrofurans have little or no effect. Vitamin-electrolyte therapy is helpful. High levels of tetracyclines are contraindicated because they tie up calcium, thereby producing rickets. Surviving chicks remain unthrifty and more susceptible to secondary infections because of immunosuppression.
Prevention
A vaccine is commercially available.
17Equine encephalitis
Species affected
Equine encephalitis is a contagious disease of birds (especially pheasants), mammals (especially horses) and people. Birds are the major source of the virus.
Clinical signs
Two forms affect birds: Eastern equine encephalitis (EEE) and western equine encephalitis (WEE). The clinical signs are identical and include staggering and paralysis. Surviving birds may be blind, have muscle paralysis, and have difficulty holding their head up. Damage to the bird's nervous system varies with species.
Transmission
Infected mosquitoes are the primary source of the virus. Culiseta melanura is the primary transmitter of the virus to poultry. Other mosquito species transmit the disease too, but feed mostly on other animals.
Treatment
None.
Prevention
Remove the source of infection by establishing mosquito control: keep weeds mowed in a 50-foot strip around bird pens. This removes cover and resting areas for mosquitoes. Eliminate mosquito breeding areas.
18Avian encephalomyelitis (AE)
Synonyms
Epidemic tremor.
Species affected
The disease is most prevalent in chickens less than 6 weeks of age. Pheasants, coturnix quail and turkeys are natural hosts as well, but less susceptible than chickens.
Clinical signs
Signs commonly appear during the first week of life and between the second and third weeks. Affected chicks may first show a dull expression of the eyes, followed by progressive incoordination, sitting on hocks, tremors of the head and neck, and finally paralysis or prostration. Some may refuse to walk or will walk on their hocks. In advanced cases, many chicks will lie with both feet out to one side (prostrate) and die. All stages (dullness, tremors, prostration) can usually be seen in an affected flock.
Transmission
The virus can be transmitted through the egg from infected hen to chick, accounting for disease during the first week of life. The disease can also be spread through a flock by direct contact of susceptible hatchlings with infected birds, accounting for the disease at 2–3 weeks of age. Indirect spread can occur through faecal contamination of feed and water. Recovered birds are immune and do not spread the virus.
Treatment
There is no treatment for outbreaks. Infected birds should be removed, killed and incinerated.
Prevention
A vaccine is available.
19Egg drop syndrome (EDS)
Synonyms
Egg drop.
Species affected
The natural hosts for Egg Drop Syndrome (EDS) virus are ducks and geese. Chickens of all ages and breeds are susceptible. The disease is most severe in broiler-breeders and brown-egg layer strains.
Clinical signs
There are no reliable signs other than the effects on egg production and egg quality. Healthy-appearing hens start laying thin-shelled and shell-less eggs. Once established, the condition results in a failure to achieve egg production targets. Transient diarrhoea and dullness occur prior to egg shell changes.
Transmission
It is believed that the syndrome was first introduced into chickens from contaminated vaccine. Vertical transmission occurs from infected breeders to chicks. Newly hatched chicks excrete the virus in the faeces.
Treatment
There is no successful treatment. Induced moulting will restore egg production.
Prevention
Prevention involves a good biosecurity program.
20Infectious tenosynovitis
Species affected
Turkeys and chickens.
Clinical signs
Some are localised in the joints (tenosynovitis) while others target respiratory or intestinal tissues (septicemic form). The principal sign of tenosynovitis is lameness with swelling of the tendon sheaths of the shank and area extending above the hock. Affected birds are lame, sit on their hocks and are reluctant to move. Infection can also play a part in broiler stunting, the result of malabsorption syndrome.
Transmission
The infection spreads rapidly through broiler flocks, but less rapidly in caged layers. Spread is by respiratory and digestive tract routes. The virus is shed in the faeces.
Treatment
There is no satisfactory treatment available. With hens, tetracycline, molasses and oyster shell therapy is helpful.
Prevention
A vaccine is available for use in endemic areas or on endemic farms.
21Non-respiratory bacterial diseases
Bacterial infections remain a major source of economic loss in poultry production. Most are preventable through hygiene, biosecurity and appropriate vaccination — and where treatment is needed, antibiotic choice matters. The seven conditions below are the most clinically significant.
22Fowl cholera
Species affected
Domestic fowl of all species (primarily turkeys and chickens), game birds (especially pheasants and ducks), cage birds, wild birds and birds in zoological collections and aviaries are susceptible.
Clinical signs
Fowl cholera usually strikes birds older than 6 weeks of age. In acute outbreaks, dead birds may be the first sign. Fever, mucoid discharge from the mouth, ruffled feathers, diarrhoea and laboured breathing may be seen. As the disease progresses birds lose weight, become lame from joint infections, and develop rattling noises from exudate in air passages. As fowl cholera becomes chronic, chickens develop abscessed wattles and swollen joints and foot pads. Caseous exudate may form in the sinuses around the eyes. Turkeys may have twisted necks.
Transmission
Multiple means of transmission have been demonstrated. Flock additions, free-flying birds, infected premises, predators and rodents are all possibilities.
Treatment
A flock can be medicated with a sulfa drug (sulfonamides, especially sulfadimethoxine, sulfaquinoxaline, sulfamethazine and sulfaquinoxalene) or vaccinated, or both, to stop mortality associated with an outbreak. It must be noted, however, that sulfa drugs could leave residues in meat and eggs. Antibiotics can be used, but require higher levels and long-term medication to stop the outbreak.
Prevention
On fowl cholera endemic farms, vaccination is advisable. Do not vaccinate for fowl cholera unless you have a problem on the farm. Rodent control is essential to prevent future outbreaks.
23Omphalitis
Synonyms
Navel ill, mushy chick disease.
Species affected
Chickens.
Clinical signs
Affected chicks may have external navel infection, large unabsorbed yolk sacs, peritonitis with fetid odour, exudates adhering to the navel, oedema of the skin of the ventral body area, septicemia and dehydration.
Transmission
Infection occurs at the time of hatching or shortly thereafter, before navels are healed. Chicks from dirty hatching eggs or eggs with poor quality shells, or newly hatched chicks placed in dirty holding boxes, are most susceptible. Chicks removed prior to complete healing of the navel due to improper temperature and/or humidity are also more susceptible. Eggs that explode in the hatching tray contaminate other eggs in the tray and increase the incidence.
Treatment
There is no specific treatment for omphalitis. Most affected birds die in the first few days of life. Unaffected birds need no medication.
Prevention
Control is by prevention through effective hatchery sanitation, hatchery procedures, breeder flock surveillance, and proper pre-incubation handling of eggs.
24Pullorum
Synonyms
Bacillary white diarrhoea.
Species affected
Chickens and turkeys are most susceptible, although other species of birds can become infected. Pullorum has never been a problem in commercially grown game birds such as pheasant, chukar partridge and quail.
Clinical signs
Clinical signs include huddling, droopiness, diarrhoea, weakness, pasted vent, gasping and chalk-white faeces, sometimes stained with green bile. Affected birds are unthrifty and stunted because they do not eat. Survivors become asymptomatic carriers with localised infection in the ovary.
Transmission
Pullorum is spread primarily through the egg, from hen to chick. It can spread further by contaminated incubators, hatchers, chick boxes, houses, equipment, poultry by-product feedstuffs and carrier birds.
Treatment
Several sulfonamides, antibiotics and antibacterials are effective in reducing mortality, but none eradicates the disease from the flock. Pullorum eradication is required by law. Eradication requires destroying the entire flock.
Prevention
Pullorum outbreaks are handled, on an eradication basis.
Pullorum is subject to statutory control in most countries. Do not attempt to treat or sell from an infected flock — contact your veterinary authority immediately.
25Necrotic enteritis
Synonyms
Enterotoxemia, rot gut.
Species affected
Rapidly growing young birds, especially chickens and turkeys 2–12 weeks of age, are most susceptible. Necrotic enteritis is a disease associated with domestication and is unlikely to threaten wild bird populations. Necrotic enteritis is primarily a disease of broilers, roasters and turkeys. Ulcerative enteritis, on the other hand, commonly affects pullets and quail.
Clinical signs
Often blood-stained faeces and diarrhoea. Chronically affected birds become emaciated. The bird, intestines and faeces emit a fetid odour.
Transmission
Necrotic enteritis does not spread directly from bird to bird. Bacteria are ingested along with infected soil, faeces or other infected materials. The bacteria then grow in the intestinal tract. Infection commonly occurs in crowded flocks, immunosuppressed flocks, and flocks maintained in poor sanitary conditions.
Treatment
Clostridia bacteria involved in necrotic enteritis are sensitive to bacitracin, neomycin and tetracycline. However, antibiotics such as penicillin and streptomycin are also effective.
Prevention
Prevention should be directed toward sanitation, husbandry and management.
26Ulcerative enteritis
Synonyms
Quail disease.
Species affected
Captive quails are extremely susceptible and must be maintained on wire-bottom pens or on preventive medications. Chickens, turkeys, partridges, grouse and other species are occasionally affected.
Clinical signs
In quail, the disease is acute with high mortality. In chickens, signs are less dramatic. Acute signs are extreme depression and reduction in feed consumption. Affected birds sit humped with eyes closed. Other signs include emaciation, watery droppings streaked with urates, and dull ruffled feathers.
Transmission
Birds become infected by direct contact with carrier birds, infected droppings or contaminated pens, feed and water. Bacteria is passed in the droppings of sick and carrier birds. Infection can be spread mechanically on shoes, feed bags and equipment.
Treatment
Bacitracin and neomycin can be used singly or in combination. Other antimicrobial agents such as tetracyclines, penicillin and lincomycin are also effective.
Prevention
Ulcerative enteritis is difficult to prevent in quails. When quails have access to their own droppings, this disease commonly occurs. To eradicate, depopulate stock, thoroughly clean and disinfect, and start over with young and clean stock.
27Botulism
Species affected
All fowl of any age, humans and other animals are highly susceptible.
Clinical signs
Botulism is a poisoning caused by eating spoiled food containing a neurotoxin produced by the bacterium Clostridium botulinum. Paralysis, the most common clinical sign, occurs within a few hours after poisoned food is eaten. Pheasants with botulism remain alert, but paralysed. Legs and wings become paralysed, and then the neck becomes limp. Neck feathers become loose in the follicle and can be pulled easily.
Transmission
Botulism is common in wild ducks and is a frequent killer of waterfowl because the organisms multiply in dead fish and decaying vegetation along shorelines. Decaying bird carcasses on poultry ranges, wet litter or other organic matter, and fly maggots from decaying substances may harbour botulism. There is no spread from bird to bird.
Treatment
Remove spoiled feed or decaying matter. Flush the flock with Epsom salts in water or in wet mash. It has been reported that potassium permanganate in the drinking water is helpful. Affected birds can be treated with botulism antitoxin injections.
Prevention
Incinerate or bury dead birds promptly. Do not feed spoiled canned vegetables. Control flies. Replace suspected feeds.
28Staphylococcus
Synonyms
Staph infection, staph septicemia, staph arthritis, bumble foot.
Species affected
All fowl, especially turkeys, chickens, game birds and waterfowl, are susceptible.
Clinical signs
Staphylococcal infections appear in three forms — septicaemia (acute), arthritic (chronic) and bumble-foot. The septicaemia form appears similar to fowl cholera in that the birds are listless, without appetite, feverish and show pain during movement. Black rot may show up in eggs (the organism is passed in the egg). Infected birds pass fetid watery diarrhoea. Many will have swollen joints (arthritis) and production drops.
Transmission
Staphylococcus aureus is soil-borne and outbreaks in flocks often occur after storms when birds on range drink from stagnant rain pools.
Treatment
It can be treated with erythromycin and penicillin.
Prevention
Remove objects that cause injury. Isolate chronically affected birds. Provide nutritionally balanced feed.
29Quick-reference summary table
The table below summarises the treatment and prevention approaches for the diseases covered in this guide.
| Disease | Category | Treatment | Prevention |
|---|---|---|---|
| Fowl pox | Respiratory | None — support care only | Insecticide spray; vaccination in endemic areas |
| Newcastle disease | Respiratory | Antibiotics for 3–5 days (secondary infection) | Vaccination + biosecurity |
| Infectious bronchitis | Respiratory | Antibiotics 3–5 days; raise brooder temp 5°F | Biosecurity; vaccines available |
| Quail bronchitis | Respiratory | Antibiotics for secondary infections | Depopulate, clean, 30–90 day quarantine |
| Avian influenza | Respiratory | None effective; antibiotics for secondary | Quarantine; destruction of infected flocks |
| Infectious coryza | Respiratory | Sulfadimethoxine (preferred); sulfamethazine, erythromycin or tetracycline | Vaccination; avoid mixing flocks |
| Laryngotracheitis (LT) | Respiratory | Antibiotics; incinerate dead birds | Vaccinate replacement birds |
| Turkey rhinotracheitis | Respiratory | Antibiotics for secondary infections | Biosecurity; no vaccine |
| Chlamydiosis | Respiratory | Chlortetracycline 200–400 g/ton × 3 weeks | Biosecurity; exclude wild birds |
| Swollen head syndrome | Respiratory | None proven | Commercial vaccine available (not in US) |
| Aspergillosis | Respiratory (fungal) | Fungistat in feed; copper sulfate in water | Clean/disinfect brooding area |
| Marek's disease | Viral | None | Hatchery vaccination |
| Lymphoid leukosis | Viral | None | LL-free breeder flocks |
| Infectious bursal disease | Viral | Vitamin-electrolyte therapy (no specific treatment) | Commercial vaccine |
| Equine encephalitis | Viral | None | Mosquito control |
| Avian encephalomyelitis | Viral | None — cull & incinerate | Vaccine available |
| Egg drop syndrome | Viral | None; induced moulting restores production | Biosecurity |
| Infectious tenosynovitis | Viral | Tetracycline, molasses, oyster shell (in hens) | Vaccine (endemic areas) |
| Fowl cholera | Bacterial | Sulfonamides (sulfadimethoxine etc.); antibiotics | Vaccination on endemic farms; rodent control |
| Omphalitis | Bacterial | None specific | Hatchery sanitation |
| Pullorum | Bacterial | Sulfonamides/antibiotics reduce mortality, do not eradicate | Eradication by destroying flock (legally required) |
| Necrotic enteritis | Bacterial | Bacitracin, neomycin, tetracycline, penicillin, streptomycin | Sanitation, husbandry, management |
| Ulcerative enteritis | Bacterial | Bacitracin, neomycin, tetracyclines, penicillin, lincomycin | Depopulate, clean, disinfect, restock |
| Botulism | Bacterial (toxin) | Epsom salts flush; potassium permanganate; botulism antitoxin | Remove carcasses, control flies, replace feed |
| Staphylococcus | Bacterial | Erythromycin, penicillin | Remove injury sources; balanced feed |
30Key takeaways for poultry health
Poultry diseases — whether respiratory, viral or bacterial — remain the biggest threat to flock productivity and, in several cases, to human health. Avian influenza, chlamydiosis and pullorum all carry public-health or regulatory significance.
Across all 25 diseases covered in this guide, three principles dominate:
- Biosecurity is non-negotiable. Most outbreaks trace back to contaminated equipment, personnel, wild birds or rodents. A comprehensive biosecurity program is the single most effective control measure.
- Vaccination prevents what treatment cannot cure. For Newcastle disease, Marek's disease, IBD, coryza, LT and several others, vaccination is the only realistic way to keep flocks protected.
- Antibiotics are for secondary infections — not for viruses. In viral diseases, antibiotics only address secondary bacterial infections. Their use must be judicious to preserve efficacy and avoid residues in meat and eggs.
Early recognition, prompt reporting of notifiable diseases, correct use of antimicrobials, and strict biosecurity save more flocks than any single drug can. When in doubt, contact a licensed veterinarian.
31Authoritative resources
For diagnostic confirmation, notifiable disease reporting or treatment protocols, consult authoritative veterinary sources.
32About this guide
This guide is an educational compilation for pharmacy students, veterinary learners and poultry producers. It does not replace institutional teaching, professional formularies, official regulatory guidance or consultation with a qualified veterinarian.
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