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  Barbara Loveless

Poultry Diseases

LT - Laryngotracheitis

This disease is characterized by respiratory distress, gasping, and expectoration of bloody exudate.   The virus is readily destroyed by most common disinfectants when outside the host environment. ·  

Birds usually become infected by inhalation of the virus.  Bird to bird transmission occurs in acute outbreaks.  Birds that recover may act as carriers and shed the virus intermittently.

Lesions are seen in the trachea and larynx.  The trachea may also contain clotted blood and the mucosa will be inflamed and hemorrhagic.

There is no available treatment against LT virus under field conditions.  If the disease is diagnosed early, vaccination of the flock may help unaffected birds before they become exposed  to the field virus.  The use of broad spectrum antibiotics may help reduce secondary infection.

To prevent LT, keep unauthorized personnel out of the poultry house.  Vaccinate all breeder/layer birds at the proper time.  Broilers are not routinely vaccinated for LT unless there is an outbreak in close proximity.


Pullorum Disease is a bacterial infectious disease of primarily young avian species characterized by white diarrhea, pinpoint necrosis of organs, and mortality. It usually occurs in an acute systemic form in chicks and poults, but in adults is more localized and chronic. Birds often remain carriers after being infected. Due to eradication programs, this disease has been practically eliminated from the U.S. poultry industry. 

Pullorum Disease is caused by a bacterium, Samonella pullorum. This organism is non-motile and highly adaptive to chickens and turkeys. S.pullorum may survive for years in a favorable environment, but is less resistant to heat, cold, and most disinfectants.

Transmission is primarily from infected hen to egg. However, the organism can penetrate to eggshell and infect the embryo. It can also be spread to uninfected chicks during hatching. Cannibalism of infected birds or eggs can also allow new infections to develop.

Chicks from infected eggs are weak and often die within several days. Affected birds tend to huddle under brooders and are depressed. They frequently give out a shrill cry when voiding droppings. Gasping may also be observed as the lungs are often infected. Adult birds usually don't show clinical signs, however, there may be a reduction in egg production and fertility.

Diagnosis can be made from clinical signs and gross lesions. A positive diagnosis requires isolation and identification of the organism. Serologic testing alone is not considered adequate for a positive diagnosis. Pullorum disease can be slowed by antibiotics, but no drug is capable of eliminating Pullorum from a flock. Participation in the National Poultry Improvement Plan has nearly eradicated Pullorum disease from the U.S. poultry industry.


MG is a disease of chickens and turkeys characterized by nasal discharge, respiratory rales, coughing, sinusitis, and air sacculitis. This disease is often referred to as chronic respiratory disease. · 

MG is spread by direct contact with infected carrier chickens or turkeys. It also is spread by dust, droplets, and equipment. This organism is also often transmitted through the egg, causing infection in the offspring.

Gross lesions consist mainly of thick, sticky mucous in the nose, sinuses, trachea, and air sacs.

Various antibiotics may be used to treat MG infections. If possible, sensitivity testing should be done to determine the best antibiotic to use since some strains of MG have become resistant to some antibiotics. Egg dipping is an acceptable way of getting antibiotic into eggs!

To keep flocks free of MG requires obtaining replacement flocks that are know to be free of MG and rearing them in a strict isolation to avoid introduction of the disease. The National Poultry Improvement Plan has adopted MG control programs for breeders. On farms with MG infection, complete depopulation and disinfection of the facilities is required to eliminate MG. However, pullets may be vaccinated with an inactive MG bacterian or the live F-strain MG vaccine.


MS is an infectious disease of chickens and turkeys which affects the synovial membranes of joints and tendon sheaths producing an exudative synovitis or bursitis. It often occurs as a sub-clinical upper respiratory infection which may lead to air sac infection.

The organism responsible for MS is light sensitive and also to most commonly used disinfectants. In many respects, the spread of MS is similar to MG. It is spread laterally through a flock by direct contact with infected birds, inhalation, or contaminated equipment and clothing. Vertical transmission plays a major role in the spread of MS in chickens and turkeys.

Often, the infection will be present without clinical signs. In chickens, there may be lameness, ruffled feathers, retarded growth, pale comb, and swollen joints. Breast blisters are also a common finding. Frequently, a greenish coloring of droppings, which contains high amounts of uric acid, is observed. Air sacculitis may be observed in birds of any age, but is usually not seen in turkeys.

Diagnosis may be made upon clinical signs, but isolation of the organism is most helpful in diagnosis of MS. Serologic testing is useful in determining previous exposure to the organism. Treatment is best administered by injectable antibiotic. The only way to prevent MS is to select birds from MS-free flocks and to adhere to good biosecurity practices.