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Comparison of tracheal and choanal cleft swabs and poultry dust samples for detection of Newcastle disease virus and infectious bronchitis virus genome in vaccinated meat chicken flocks.

ABSTRACT: This study assessed different methods (tracheal and choanal cleft swabs from individual birds, and poultry dust as a population level measure) to evaluate the shedding kinetics of infectious bronchitis virus (IBV) and Newcastle disease virus (NDV) genome in meat chicken flocks after spray vaccination at hatchery. Dust samples and tracheal and choanal cleft swabs were collected from four meat chicken flocks at 10, 14, 21 and 31 days post vaccination (dpv) and tested for IBV and NDV genome copies (GC) by reverse transcriptase (RT)-PCR. IBV and NDV GC were detected in all sample types throughout the study period. Detection rates for choanal cleft and tracheal swabs were comparable, with moderate and fair agreement between sample types for IBV (McNemar's = 0.27, kappa = 0.44) and NDV (McNemar's = 0.09; kappa = 0.31) GC respectively. There was no significant association for IBV GC in swabs and dust samples (R2 = 0.15, P = 0.13) but NDV detection rates and viral load in swabs were strongly associated with NDV GC in dust samples (R2 = 0.86 and R2 = 0.90, P<0.001). There was no difference in IBV and NDV GC in dust samples collected from different locations within a poultry house. In conclusion, dust samples collected from any location within poultry house show promise for monitoring IBV and NDV GC in meat chickens at a population level and choanal cleft swabs can be used for detection of IBV and NDV GC instead of tracheal swabs in individual birds.

SUBMITTER: Assen AM

PROVIDER: S-EPMC8051787 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Newcastle disease virus (NDV) belongs to genus Avulavirus and family Paramyxoviridae. There are thirteen serotypes named APMV-I (Avian Paramyxovirus-I) to APMV-13 of which NDV has been designated as APMV-1. The disease has been reported worldwide affecting both domestic and wild avian species. Morbidity and mortality rates up to 100% have been reported in cases of unvaccinated flocks. Stringent vaccination schedule is practiced in endemic/disease prone areas in order to prevent the disease. Despite this, NDV outbreaks have been reported even in cases of vaccinated populations. In this study we describe detailed pathological and molecular investigation that were undertaken in an organized poultry farm from Bareilly region, Uttar Pradesh, India, involving layer flocks which succumbed to ND outbreak in spite of following strict vaccination protocol. The mortality rate ranged from 76.80 to 84.41% in different flocks with an average mortality of 79.50%. Necropsied birds had gross lesions suggestive of viscerotropic ND including petechial hemorrhages on the proventricular tips, intestinal lumen with necrotic areas covered with hemorrhages, hemorrhagic cecal tonsils, para-tracheal edema and mottling of spleen. The characteristic histopathological lesions were mainly seen in the blood vessels and lymphoid tissues. Vascular changes characterized by congestion, edema, and hemorrhage were found in majority of the organs. Lymphocytolysis in spleen and cecal tonsils was evident. Immunohistochemical studies revealed positive signals mostly in macrophage and lymphocytes. PCR assay was done to confirm the NDV genome, which revealed an amplicon size of 356 bp. The phylogenetic analysis revealed the resemblance of the present isolate (ADS01) with class II genotype NDV XIIIA. The isolate belonged to velogenic NDV as the Minimum Lethal Dose (MLD) and Mean Death Time (MDT) for the present isolate were 10-8 and 41 h, respectively. Thus this study clearly demonstrates that in spite of strict vaccination regime and biosecurity procedures, ND continues to be rampant. Hence it is important to effectively administer the present vaccine in addition to strains matching to the field isolates to provide longer and optimal protection against spreading of virus by means of reducing the extent of viral shedding.

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Comparison of tracheal and choanal cleft swabs and poultry dust samples for detection of Newcastle disease virus and infectious bronchitis virus genome in vaccinated meat chicken flocks.

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