• Korean Journal of Veterinary Service
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• v.16 no.1
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• pp.76-81
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• 1993

To evaluate the pathogenesis of live infectious laryngotracheitis vaccine, virus, virus and E.coli were inoculated in 4-weeks old intraorbitally and intraorally. Their pathology and serology were studied. The results were as follows. 1. thicks Inoculated with ILT vaccine alone showed no clinical sign. 2. Some of chicks inoculated with ILT vaccine followed by E.coli after 1day showed nasal discharge and cough. 3. Some of chicks inoculated with E. coli followed by ILT vaccine after 1 day and inoculated ILT vaccine and E.coli concurrently, showed nasal discharge. 4. Serum neutralization titers of chicks inoculated with ILT vaccine increased 3 weeks after Inoculation, peaked at 7 to 8 weeks and decreased. 5. Antibiotic sensitivity of E.coli were higher in Enrofloxacin (Baytril) and chloramphenical.

• Korean Journal of Veterinary Research
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• v.42 no.2
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• pp.241-251
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• 2002

Modified-live (ML) infectious laryngotracheitis (ILT) vaccines have been widely used as a preventive measure in Korea since the first outbreak of ITL. Recently, it has been observed that chickens vaccinated with the commercially available ML ILT vaccine have sometimes exhibited adverse clinical signs. In this study, we evaluated the quality of the vaccines by comparing titer of each vaccine batch and testing the stability of ILT virus (ILTV) in vaccine diluents and compared the safety and efficacy of vaccines in specific pathogen free (SPF) chickens. The ratio of maximum titer to minimum titer of vaccine produced by most manufacturers was 2 to 15. However, 2 out of 11 manufacturers produced vaccines of which the ratio was 74 to 478. Most vaccines examined were maintained vaccine titers suitable for national regulations within expiry date. However, some vaccines did not keep the titer required for the national regulations. In the test for stability of ILTV in various diluents, ILTV was highly stable in lactose-phosphate-glutamine-gelatin solution, sucrose-phophate-glutamine-albumin solution and some vaccine diluents produced by manufacturers. The safety of ML ILT vaccines was assessed in 10-day-old SPF chicks. Mortality in SPF chicks inoculated intratracheally with one dose of vaccine varied depending on vaccines and some vaccines produced 50-85% mortality. Seven-week-old SPF chickens were vaccinated intraocularly with ML ILT vaccines and then challenged intratracheally with ILT challenge virus 14 days after vaccination. The protection rate was assessed by clinical signs and reisolation of the ILT challenge virus from tracheas taken at day 4 after challenge. There were slight respiratory reactions in some vaccinated chickens after vaccination but these reactions disappeared within 5 days after vaccination. No further clinical signs and death were observed. Protection rate determined by clinical signs and mortality was 100% in all vaccinated groups. However, the challenge virus was isolated from all tracheas of chickens vaccinated with vaccine B or control groups. The challenge virus was also isolated in the trachea of one in five chickens vaccinated with either vaccine F or K, but not in tracheas of chickens vaccinated with other vaccines. In the present study, the stability of vaccine diluents, pathogenicity and protection rate based on reisolation test of the challenge virus were different depending on vaccines produced by eleven manufacturers.