LABOUTE Mathilde1, ALBARIC Olivier2, CAZABAN Christophe3, PALYA Vilmos4, ALVA Branko3, JACQUINET Claire3, RAMON Gema3, GARDIN Yannick3
1 70 avenue de la Libération, 72000 Le Mans, France
2 Oniris, Atlanpole La Chantrerie, 44307 Nantes, France
3 CEVA Sante Animale, 10 avenue de la Ballastiere, 33500 Libourne, France
4 Ceva Phylaxia, Szallas u. 5, 1107 Budapest, Hungary
An infectious bursal disease virus (IBDV) immune-complex vaccine was administered by the in ovo route to commercial broilers under field conditions to prevent infectious bursal disease (IBD). The aim of this study was to design a detailed standard using several biological parameters to monitor the onset and development of immunity induced by this vaccine. Such educational standards are needed by field veterinarians and diagnostic laboratories for a more accurate assessment of any bursal lesions in a vaccinated flock that could first suggest a field infection. At 15, 18, 20, 22, 24, 26, 28, 30, 32, 34 and 40 days after hatch, ten chickens were randomly chosen, weighed and euthanatized. Antibody titers to IBDV were
assayed in the sera. Bursas of Fabricius were collected, macroscopically assessed, weighed, and submitted for histopathological examination: the observed lesions were scored according to the European Pharmacopoeia. RT-PCR was used to confirm the type of the IBDV present in the bursa.
Serological analysis confirmed the decay of maternal immunity and the onset of active immunity to IBDV.
Gross appearance, weight, and histopathology of the bursa of Fabricius were in accordance with the kinetics of the onset of immunity that was elicited by this vaccine. As expected, the replication of the vaccine virus in the bursa was characterized by inflammatory lesions from 3 weeks of age onwards, as evidenced by increased histological lesion scores. Molecular analysis for IBDV did confirm that the observed lesions were due to the vaccine virus and correlated with the subsequent detection of antibodies to IBDV by ELISA. At study completion at 40 days of age, histological signs of bursal regeneration were obvious.
The results of this study enable the monitoring of the development of immunity in the IBDV immunecomplex vaccinated broiler flocks.
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