Pathogenicity of novel variant infectious bursal disease virus in specific pathogen free chickens

Be, Tein Hock (2023) Pathogenicity of novel variant infectious bursal disease virus in specific pathogen free chickens. [Project Paper] (Submitted)

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Abstract

In 2017, a new strain of infectious bursal disease virus (IBDV) known as novel variant infectious bursal disease virus (nVarIBDV) emerged in China. This strain has become widely prevalent in poultry farms despite vaccination. Recently, the first case of nVarIBDV was reported in Malaysia in 2019. Although this new strain does not typically result in high mortality, it can leads to significant morbidity and severe bursal atrophy in affected chickens causing remarkable immunosuppression and subsequent economic loss. Therefore, the need for understanding the pathogenicity of nVarIBDV in Malaysia is crucially important to contribute in the diagnostic process, disease prevention and control, as well as vaccine production. The objective of this study was to determine the pathogenicity of nVarIBDV in specific pathogen free (SPF) chickens in terms of clinical signs, body weight, bursa and spleen parameters, gross and histological lesions, antibody titer, and viral loads. A total of 60 21-day-old SPF chickens were divided into two groups (Group A and Group B). Birds in Group A were inoculated with 106.75 EID50/mL of nVarIBDV while Group B served as control. At 0 days post inoculation (dpi), four birds from group B were sacrificed for pre-test examination. Four birds from each group were sacrificed at 1, 3, 5, 7, 10, 14, and 21 dpi for pathogenicity examination. The results showed abnormal clinical signs such as watery diarrhea and ruffled feather in Group A. However, there was no significant difference (p>0.05) between the body weight of both groups. From the bursa and spleen parameters, bursal atrophy and splenomegaly were verified in the inoculated chickens. In bursa, other gross lesions such as yellowish stained bursa, decreased bursal folds, and firm consistency of bursa were recorded. Histological lesions of bursa showed severe follicular atrophy and large cysts formation which hits the highest bursal lesion score of 5. Antibody titer of group A was significantly higher (p<0.05) than group B since 5 dpi. The viral loads in bursa was the highest whereas it was the lowest in bone marrow throughout the trial. Thus, the findings suggested that nVarIBDV causes significant clinical infection in SPF chickens with the signs of watery diarrhea and ruffled feather accompanied by severe bursal atrophy and splenomegaly. Besides, the inoculated chickens showed positive antibody response from 5 dpi and the bursa hosted the highest amount of virus, but this strain does not cause mortality.

Item Type:	Project Paper
Faculty:	Faculty of Veterinary Medicine
Depositing User:	Ms Nurhaznita Mahmood
Date Deposited:	19 Nov 2024 03:18
Last Modified:	19 Nov 2024 03:18
URI:	http://psaspb.upm.edu.my/id/eprint/2172

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