infectiontracing of H120 vaccine virus produced in razi insetu in on and 14 day old chickens inoculated by eye-drop route in compassion with imported one.

The present study was design to understand the distribution and residual of two commercial H120 vaccine viruses which available in Iranian market in tissues of SPF chickens. 90 chickens of both sex was randomly divided to 3 equal groups as imported vaccine, native produced vaccine and control group. Vaccination of respected groups was done as recommended by producers by using eye drop route at one and 14 days of arrival. Then beside clinical observation samples required to histopathology, virus isolation and RT-PCR tests from tissues of trachea, lung, kidney, bursa of fabricius of randomly selected 5 birds from each groups after humanly cervical euthinisation was taken. Sampling days was scheduled as 3, 7, 14, 16, 21 and 28 post vaccination days (pvd). Watery eyes in chickens of only imported vaccine group was seen on clinical examination for 3 to 4, pvd with no any sign in others groups of chickens. Tracheal section shows inflammatory response in one out of 5 samples in native vaccinated group at 3, pvd and also in one sample of lung from imported vaccine group at 7 pvd. RT-PCR test using primer for partial N protein gene amplification, detect virus on days of 3 and 16, pvd in pooled extract of trachea tissues and lung tissue extract on 7 pvd for imported vaccine group. The sample of other tissues remained negative during all sampling days for all 3 groups. Interestingly virus isolation attempts using embryonated SPF chickens egg because of low replication of inoculated vaccines virus was unsuccessful for all 3 groups of chickens. In conclusion despite of observed vaccination reaction in clinical examination in imported vaccine group and also with consideration of sensitivity of RT-PCR test, virus distribution and residual in tissues of trachea, lung, kidney, bursa of fabricius for two vaccine viruses was the same. But more studies about transmission of vaccine viruses to contact bird which is the important factor in uniform immunity of vaccinated flocks and quality of induced mucosal immunity needed to be evaluated for substantial quality assaying of native produced Massachusetts H120 vaccine.