Abstract
An infectious disease hitherto unobserved in Palestine was reported among chicks from different poultry farms. Symptomatology resembled infectious laryngotracheitis 1 ; it differed from this infection by its mild course, absence of fatalities and of any noticeable effect on development. The disease is milder in young than in old chicks.
Mucus from the trachea of infected chickens was triturated with sand, diluted with nine parts saline and divided into two parts: one was used for inoculation, the other was passed through Seitz filter and the filtrate inoculated in the same manner as the unfiltered material. The results demonstrated that the causative agent was a filterable virus. Cultures of the filtrate in a variety of media remained sterile. The virus was recovered from the lung, but not from the liver, ovary or uterus.
Infection was most readily produced by dropping infected material into the trachea, also by intraperitoneal or intrathoracic inoculation. The incubation period varied with the age of chicks and the concentration of virus. One-week-old chicks showed the first symptoms of infection after 5 days; in chicks 2 weeks old, the incubation period was 9 to 24 days; in 6-8-week chicks the incubation period varied from 11 to 42 days. The infection spread quickly by contact. The time of exposure before appearance of symptoms (8-10-week chicks) ranged from 22 to 64 days. The virus could be demonstrated in the tracheal secretion in 1:1,000,000 in unfiltered and in 1:10,000 in filtered fluid.
Experiments demonstrated that the virus was transmitted on the surface of the egg shell.
1. Eggs were obtained from the infected farm and incubated.
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