Syndromic surveillance of infectious bursal disease in chickens using lesion indicators: Analysis of clinical records (2008–2018)
Infectious bursal disease (IBD) outbreaks significantly undermine chicken production. Syndromic surveillance based on lesion indicators is an established tool for monitoring the disease following reports of morbidity and mortality. This study aimed to develop an epidemiological profile of the IBD burden, including syndromic outbreak prevalence rates, yearly trends, mortality rates, and lesion patterns, used for surveillance. Records of IBD outbreaks from two veterinary hospitals in Maiduguri, Nigeria, were extracted from all reported disease outbreaks in chicken flocks between 2008 and 2018. IBD outbreaks accounted for 493 cases (7.6%; 95% confidence interval [CI]: 7.0–8.3%) of 6,486 recorded disease outbreaks. Annual prevalence ranged from 1.6% (95% CI: 0.9–2.3%) to 17.3% (95% CI: 12.9–21.7%) and showed a linear trend (r = −0.73; p < 0.01), with a significant association across years (p < 0.001). Prevalence varied significantly with chicken type (p < 0.05), with the highest rate observed in Noilers (25.0%), followed by cockerels (17.5%), local chickens (9.1%), broilers (7.2%), and layers (7.1%). Affected chickens were aged 2–27 weeks, with a modal age of 4–5 weeks and a mean age of 5.0 ± 1.7 weeks. The overall mortality rate was 12.6% (95% CI: 12.3–12.9) based on a total flock size of 38,485 from 2015 to 2018, the period for which flock size and mortality records were available. Key lesions used for syndromic detection of acute IBD included inflammatory swelling of the bursa of Fabricius (90.9%), hemorrhages in thigh, leg, and/or breast muscles (72.2%), mucosal hemorrhages at the proventriculus–ventriculus junction, with and without enteritis (24.9%), and kidney lesions (7.7%). This syndromic surveillance system enables outbreak monitoring and can inform the planning of control measures to reduce disease-associated production losses.
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