Two experiments were conducted to determine the persistence and tissue distribution of serotypes 1 and 2 of infectious bursal disease virus (IBDV) in specific-pathogen-free and vaccinated turkeys. In Experiment 1, three groups of 2-wk-old turkey poults, including a negative control group, were used. In groups 1 and 2, 13 poults in each group were challenged with either serotype 1 (STC) or serotype 2 (OH) strains using an inoculum of 104 50% embryo infectious dose (EID50)/0.2 ml/bird. Thymus, bursa, spleen, kidney, lungs, liver, pancreas, caecum, and breast and thigh muscles were sampled at predetermined intervals. The bursal tissues from birds inoculated with either serotype were reverse transcriptase–PCR (RT-PCR) positive up to 21 days postinoculation (DPI). In both groups virus isolation from bursas was possible up to 14 DPI. Except for the bursas and spleens in birds inoculated with serotype 1 and bursas in birds inoculated with serotype 2, all other tissues were RT-PCR negative. In Experiment 2, five groups of turkey poults were used. At 4 wk of age, group 1 was challenged with a serotype 1 STC strain and group 2 with serotype 2 OH strain using an inoculum size of 102 EID50/0.2 ml for both serotypes. Groups 3 and 4 were vaccinated at 2 wk of age using an inactivated serotype 1 IBDV vaccine. At 2 wk postvaccination, groups 3 and 4 were challenged with STC and OH strains respectively. From group 1, bursal, spleen, and liver tissues were RT-PCR positive up to 14 DPI; breast muscle and kidney tissues were positive up to 7 DPI; and lungs and pancreatic tissues were positive up to 3 DPI. From group 2, bursal tissues were RT-PCR positive up to 14 DPI and lung tissues up to 3 DPI. All of the tissue samples collected from groups 3, 4, and 5 were RT-PCR negative. Virus could not be isolated from RT-PCR positive bursal homogenate. In this work, it was confirmed that the virus persisted in the bursa longer than in any other tissues. The difference in the results between Experiments 1 and 2 could be due to the age of poults at vaccination and the higher inoculum size used in Experiment 1. This study indicates that turkeys are more resistant to IBDV as compared to chickens. Viruses of serotypes 1 and 2 infect turkeys and persist in bursal tissue for 14 days and RNA was detected up to 21 days.
Nota de investigación- Persistencia y distribución tisular en pavos de los serotipos 1 y 2 del virus de la enfermedad infecciosa de la bolsa.
Se realizaron dos experimentos para determinar la persistencia y la distribución en tejidos de los serotipos 1 y 2 del virus de la enfermedad infecciosa de la bolsa (IBDV) en pavos libres de patógenos específicos y en pavos vacunados. En el experimento 1, se utilizaron tres grupos de pavitos de dos semanas de edad, incluyendo un grupo control negativo. En los grupos uno y dos, trece pavipollos en cada grupo fueron desafiados ya sea con una cepa del serotipo 1 (STC) o con una cepa del serotipo 2 (OH) utilizando un inóculo de 104 dosis infecciosas para embrión de pollo50% (EID50)/0.2 ml/ave. Se recolectaron en intervalos predeterminados, muestras de timo, bolsa de Fabricio, bazo, riñones, pulmones, hígado, páncreas, ciego y de músculos de la pechuga y muslos. Los tejidos de la bolsa de Fabricio de aves inoculadas con cualquiera de los dos serotipos fueron positivos mediante transcripción reversa y PCR (RT-PCR) hasta 21 días después de la inoculación. En ambos grupos, el aislamiento viral a partir de bolsas fue posible hasta los catorce días después de la inoculación. Con excepción de las bolsas y bazos de aves inoculadas con el serotipo 1 y de bolsas en las aves inoculadas con el serotipo 2, todos los demás tejidos fueron negativos por RT-PCR. En el experimento 2, se utilizaron cinco grupos de pavos. A las 4 semanas de edad, el grupo 1 fue desafiado con una cepa del serotipo 1
