Infectious Laryngotracheitis

O. L. OSTEEN.

INFECTIOUS laryngotracheitis is an acute, highly contagious respiratory disease of chickens.

The cause is a filterable virus, which can remain alive and infective in the trachea windpipe of dead birds for 60 days at 4 to 6 C. It dies within 48 hours at 37 C. It is readily destroyed by a 3-percent cresol solution or a 1-percent lye solution in 1 to 3 minutes.

Pheasants are the only other fowl that are susceptible to laryngotracheitis under natural or experimental conditions. Embryonating - turkey and chicken eggs are experimentally susceptible to the virus.

Susceptible birds get the disease 6 to 12 days after being in contact with sick birds. Transmission of the disease by contaminated crates and other equipment is possible but is of minor importance in its spread.

The virus is not carried through the egg to the hatched chick. Recovered birds can be carriers of the virus for long periods up to 16 months and are the usual means by which the disease is spread. A person can act as a mechanical carrier and should not go from sick to healthy flocks without washing and changing to clean clothes and shoes.

Laryngotracheitis is seldom observed in chickens younger than the brooding age, although they are fully susceptible. The disease spreads rapidly to all the birds in an infected flock.

A symptom is difficult breathing, which causes the birds to extend the head and open the mouth for each respiration. A usual rattling sound is caused by obstruction of the windpipe with mucus, which often is tinged with blood. The bird may throw its head from side to side as it tries to dislodge the mucus. Coughing and a watery discharge from the eyes also occur.

A sudden drop in laying flocks of 10 to 30 percent in egg production occurs. As the disease progresses, the accumulation of excessive amounts of the thick, bloody mucus in the back of the mouth and windpipe causes death by asphyxiation. Death losses in most outbreaks is about 10 percent but may be up to 85 percent. The disease usually lasts 2 to 4 weeks. Egg production in layers stays down for about a month.

Postmortem examination of dead birds shows an inflammation of the respiratory tract. The highly inflamed windpipe with bits of blood in the mucus is significant of infectious laryngotracheitis.

Because the symptoms are so similar to Newcastle disease and infectious bronchitis, it is most advantageous to rely on a positive diagnosis made in a poultry diagnostic laboratory.

No known medicine is effective against the disease.

Preventive measures include the rigid application of sound management and sanitary practices. Hatching eggs or day-old chicks should be obtained from flocks known to be free of the disease. Clean equipment should be used and the flock kept in isolation.

An effective live-virus vaccine is available. It should be used only in areas where the disease is known to be prevalent year after year and not as a substitute for isolation and good management where outbreaks occur in widely separated areas. As the vaccine is a living virus, it is best used only after a diagnosis by qualified laboratory technicians and under their supervision.

O. L. OSTEEN received the degree of doctor of veterinary medicine from the University of Georgia in 1928. He has been employed in the Department of Agriculture since 1932.

Tapeworms of Chickens and Turkeys

J. L. GARDINER.

AT LEAST ten different species of tapeworms may exist in chickens in the United States. About a dozen species are found in turkeys and a half dozen in ducks. Geese, guinea fowl, peafowl, and pigeons also harbor a few species.

The total number of kinds of tapeworms infesting American poultry is smaller than the figures might indicate, however, because in most instances a given species lives in more than one kind of host. Tapeworms of poultry are less important than roundworms or protozoans. Nevertheless, should any of them be present in sufficient numbers, particularly in young birds, they will make their presence felt to the detriment of both the bird and its owner.