Western
Meeting of Poultry
Clinicians and Pathologists
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Clinicians and Pathologists
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FINDINGS AND PROBLEMS ASSOCIATED WITH AN IN-DEPTH LABORATORY INVESTIGATION INTO A BROILER RANCH
A. MazaheriA, B. R. CharltonA, M. C. BlandA, P. WoolcockB, G. L. CooperA and A. A. BickfordA
ACalifornia Animal Health and Food Safety Laboratory System - Turlock Branch, University of California, Davis
BCalifornia Animal Health and Food Safety Laboratory System - Fresno Branch, University of California, Davis This investigation was initiated based on a runting and stunting problem observed in the previous flocks on a broiler ranch. The farm under surveillance consisted of 6 houses with a total capacity of about 120,000 birds. Ten birds per house were selected each week during the growing period for laboratory examination. The initial focus was on virus isolation of liver, pancreas/cecal tonsil pool, tendon pool, and electron microscopy of intestine to document the possible virus involvement in the runting / stunting syndrome. In addition, serological and histological examinations were performed. Part-way through the growing period, it became apparent that a bursal problem was present. Although the birds had been vaccinated for infectious bursal disease virus (IBDV) at 7 and 17-days of age, damage was detected in the bursa from an early age up to the end of the grow-out period. An IBDV strain was detected by RT/PCR-RFLP which had sequences across the hypervariable VP2 region identical to the T1 strain except for one position. The T1 strain is designated as a hot strain which causes marked atrophy of the bursa in 3-4 days. It also breaks through maternal immunity to IBDV produced by conventional variant and classic strains (1). The average weight at the end of the run, and the weight gain records showed no indication of a runting and stunting problem. The significance of isolating reovirus in the first 3 weeks, and then later reovirus and adenovirus, is unknown. Since no inclusion bodies were found in the livers, and the reovirus was isolated primarily from healthy birds, the significance of these viruses is probably minimal. REFERENCES 1. Jackwood, D.J., S.E. Sommer and H. V. Knobich. Amino acid comparison of Infectious Bursal Disease Viruses placed in the same or different molecular groups by RT/PCR-RFLP. Avian Dis. 45: 330-339, 2001 |
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