COMMON RESPIRATORY DISEASES OF 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 and generally includes the 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.
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 bleeding. Unthriftiness and retarded growth are typical symptoms of fowl pox. 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 the 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 mosquitos. Virus-containing scabs also can be sloughed from affected birds and serve as a source of infection. The virus can enter the blood stream through the eye, skin wounds, or respiratory tract. Mosquitos become infected from feeding on birds with fowl pox in their blood stream. There is some evidence that the mosquito remains infective for life. Mosquitos are the primary reservoir and spreaders of fowl pox on poultry ranges. Several species of mosquito can transmit fowl pox. Often mosquitos winter-over in poultry houses so, outbreaks can occur during winter and early spring.
Treatment: No treatment is available. However, fowl pox is relatively slow-spreading. Thus, it is possible to vaccinate to stop an outbreak. The wing-web vaccination method is used for chickens and the thigh-stick method for turkeys older than 8 weeks.
Prevention: Fowl pox outbreaks in poultry confined to houses can be controlled by spraying to kill mosquitos. However, if fowl pox is endemic in the area, vaccination is recommended. Do not vaccinate unless the disease becomes a problem on a farm or in the area. Refer to the publication PS-36 (Vaccination of Small Poultry Flocks) for more information on fowl pox vaccinations.
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The highly contagious and lethal form of Newcastle disease is known as viscerotropic (attacks the internal organs) velogenic Newcastle disease, VVND, exotic Newcastle disease, or Asiatic Newcastle disease. VVND is not present in the United States poultry industry at this time.
Species affected: Newcastle disease affects all birds of all ages. Humans and other mammals are also susceptible to Newcastle. 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, labored breathing (gasping), facial swelling, paralysis, trembling, and twisting of the neck (sign of central nervous system involvement). Mortality ranges from 10 to 80 percent depending on the pathogenicity. In adult laying birds, symptoms can include decreased feed and water consumption and a dramatic drop in egg production (see Table 1).
Transmission: The Newcastle virus can be transmitted short distances by the airborne route or introduced on contaminated shoes, caretakers, feed deliverers, visitors, tires, dirty equipment, feed sacks, crates, and wild birds. Newcastle virus can be passed in the egg, but Newcastle-infected embryos die before hatching. 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 ). For chicks, increasing the brooding temperature 5°F may help reduce losses.
Prevention: Prevention programs should include vaccination (see publication PS-36, Vaccination of Small Poultry Flocks), good sanitation, and implementation of a comprehensive biosecurity program.
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Synonyms: IB, 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. Feed and water consumption declines. Affected chickens will be chirping, with a watery discharge from the eyes and nostrils, and labored breathing with some gasping in young chickens. Breathing noises are more noticeable at night while the birds rest. Egg production drops dramatically. Production will recover in 5 or 6 weeks, but at a lower rate. 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. The virus can be egg-transmitted, however, affected embryos usually will not hatch.
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. Baby chicks can be encouraged to eat by using a warm, moist mash.
Prevention: Establish and enforce a biosecurity program. Vaccinations are available.
Species affected: Bobwhite quail are affected. Japanese corturnix quail are resistant. The disease is prevalent in the southern states where bobwhite quail are common. Quail bronchitis occurs seasonally as new hatches and broods come along each year.
Clinical signs: Respiratory distress occurs with tracheal rales (rattles), sneezing, and coughing. Feed and water consumption declines dramatically. There can also be conjunctivitis (inflammation of the eye). Loose watery feces are seen in older and sub-acutely affected birds. Nasal discharges are not seen, differentiating quail bronchitis from similar diseases in other poultry.
Transmission: 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. Add tylosin (500g/ton) to the feed for 10 days, withhold the medication for 5 days, and then repeat medication for 5 days. Alternate medication regimens are tylosin (Tylan) or erythromycin (Gallimycin) in the drinking water for the same period of time.
Prevention: There is no commercial vaccine on 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.
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Synonyms: AI, 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, diarrhea, transient drops in egg production, and low mortality. 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. Sudden exertion adds to the total mortality. Egg production and hatchability decreases. There can be an increase in production of soft-shelled and shell-less eggs (see Table 1).
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. Vaccines may only be used with special permit.
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. If you suspect you may have Avian Influenza in your flock, even the mild form, you must report it to the state veterinarian’s office. A proper diagnosis of avian influenza is essential. Aggressive action is recommended even for milder infections as this virus has the ability to readily mutate to a more pathogenic form.
Synonyms: roup, cold, coryza
Species affected: chickens, pheasants, and guinea fowl. Common in game chicken flocks.
Clinical signs: Swelling around the face, foul smelling, thick, sticky discharge from the nostrils and eyes, labored breathing, and rales (rattles—an abnormal breathing sound) are common clinical signs. The eyelids are irritated and may stick together. The birds may have diarrhea 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. Mortality can be as high as 50 percent, but is usually no more than 20 percent. The clinical disease can last from a few days to 2–3 months, depending on the virulence of the pathogen and the existence of other infections such as mycoplasmosis.
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 which remain carriers of the organism and may shed intermittently throughout their lives. Birds risk exposure at poultry shows, bird swaps, and live-bird sales. Inapparent infected adult birds added into a flock are a common source for outbreaks. 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 (Albon®, Di-Methox™) is the preferred treatment. If it is not available, or not effective, sulfamethazine (Sulfa-Max®, SulfaSure™), erythromycin (gallimycin®), or tetracycline (Aureomycin®) can be used as alternative treatments. Sulfa drugs are not FDA approved for pullets older than 14 weeks of age or for commercial layer hens. While antibiotics can be effective in reducing clinical disease, they do not eliminate carrier birds.
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. The vaccine (Coryza-Vac) is administered subcutaneously (under the skin) on the back of the neck. 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.
Synonyms: LT, ILT, trach, laryngo
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. In recent years, LT has also caused significant respiratory problems in broilers greater than 3 weeks of age, especially during the cooler seasons of the year. This is believed to be due to unwanted spread of LT vaccines between poultry flocks.
Clinical signs: The clinical sign usually first noticed is watery eyes. 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. Blood-tinged exudates and serum clots are expelled from the trachea of affected birds. Many birds die from asphyxiation due to a blockage of the trachea when the tracheal plug is freed.
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. LT may be harbored in speciality poultry such as exhibition birds and game fowl.
Treatment: Incinerate dead birds, administer antibiotics to control secondary infection, and vaccinate the flock. Mass vaccination by spray or drinking water method is not recommended for large commercial or caged flocks. Individual bird administration by the eye-drop route is suggested. Follow manufacturers instructions. In small poultry flocks, use a swab to remove plug from gasping birds, and vaccinate by eye-drop method.
Prevention: Vaccinate replacement birds for outbreak farms. Vaccination for LT is not as successful as for other disease, but is an excellent preventive measure for use in outbreaks and in epidemic areas. Refer to the publication PS-36 (Vaccination of Small Poultry Flocks) for more information on LT vaccinations.
Synonyms: TRT, rhino tracheitis
Species affected: Turkeys of all ages are susceptible, but the disease is most severe in young poults. Chickens are susceptible to the virus. Experimentally, guinea fowl and pheasants are susceptible, but waterfowl and pigeons are resistant.
Clinical signs: Respiratory signs in poults include snicking, rales, sneezing, nasal exudates (often frothy), foamy conjunctivitis, and sinusitis. Drops in egg production can be as much as 70 percent.
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.
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. Currently, the term chlamydiosis is used to describe infections in any animal.
Species affected: Affected species include turkeys, pigeons, ducks, psittacine (curve-beaked) birds, captive and aviary birds, many other bird species, and other animals. Chickens are not commonly affected. Humans are susceptible, especially older and immunosuppressed individuals who are at a higher risk. Chlamydiosis in humans is an occupational disease of turkey growers, haulers, and processing workers in the live-bird areas and of workers in pet-bird aviaries although the incidence is rare. For more information, refer to publication PS-23 (Avian Diseases Transmissible to Humans).
Clinical signs: Clinical signs in most birds include nasal-ocular discharge, conjunctivitis, sinusitis, diarrhea, weakness, loss of body weight, and a reduction in feed consumption. In turkeys there is also respiratory distress and loose yellow to greenish-yellow colored droppings. Chylamydiosis runs rather slowly through turkey flocks, with a maximum incidence of around 50 percent.
Transmission: The primary means of transmission is through inhalation of fecal dust and respiratory tract secretions. It can also be transmitted on 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. Environmental stress may provoke a reoccurrence of the disease.
Treatment: Chlorotetracycline can be given in the feed (200–400 g/ton) for 3 weeks. Other antibiotics are usually ineffective. Recovered birds are safe for processing. Permanent lesions on the heart and liver are not infectious. FDA withdrawal periods for medications used must be strictly observed to avoid residual chemicals in the tissues.
Prevention: There is no vaccine. Have a good biosecurity program, excluding wild birds as much as possible.
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