Retrospective Studies of Marek's Disease Diagnosed in Some Towns in Nigeria, 2000 - 2009.

Abstract

A retrospective study of Marek\'s disease (MD) outbreaks diagnosed from 2000 to 2009 by veterinary clinics and hospitals at Zaria, Ibadan, Nsukka and Bukuru, Nigeria was conducted. Of the 1,970 viral cases recorded, the prevalent rate of Marek’s disease was 60.6% (1,193/1,970 at 95% CI: 58.4 – 62.7). The year 2002 experienced the highest prevalent rate of Marek’s disease with p value = 0.0129. The prevalence of MD was significantly higher (p < 0.05) among flocks aged 18 weeks and above (85.5%) compared to those aged 9 – 18 weeks (71.4%) and those aged 5 - 8 weeks (25.3%) but, least among chicks aged 1-4 weeks (14.7%). On age of birds that experienced MD, 319 outbreaks in broilers with mean age of 7.8 weeks (95% CI: 6.7 – 8.9), 77 cockerels at 15.0 weeks (95% CI: 11.2 – 18.8), 952 pullets at 12.9 (95% CI: 12.7 – 13.3) and 602 layers at 29.9 weeks of age (95% CI: 29.1 – 30.9). Layers had prevalence of 86.7%, followed by pullets with 62.1%. An MD prevalence of 63.6% was recorded during the rainy season while 55.4% was recorded during the dry. It was observed that the risk factors for MD using odds ratio analysis to test for association on year, age, type, region of the country where farm is located and season, showed statistically significant associations. The outbreaks of MD decreased in 2006 (OR 0.7; 95% CI: 0.5–0.9) and 2007 (OR 0.7; 95% CI: 0.5–1.0) compared to 2000 but increased in 2008 (OR 1.5; 95% CI: 1.1–2.2) and 2009 (OR 2.0; 95% CI: 1.2–3.4). Flocks aged 18 weeks and above were 34.3 (95% CI: 22.5–52.1) times more at risk of infection compared to 1–5 weeks. High risk of MD were also observed in flock aged 9–18 weeks (OR 14.5; 95% CI: 9.8–21.5) and 5–8 weeks (OR 2.0; 95% CI: 1.3–3.0) compared to 1–5 weeks. On the type and species of birds when compared to broilers, layers had highest chances of coming down with the disease (OR 31.3; 95% CI: 21.6–45.5) followed by pullets (OR 7.9; 95% CI: 5.7–10.8) and turkeys (OR 3.2; 95% CI: 0.9–11.7). On season, the risk of having MD was higher during the rainy season (OR 1.4; 95% CI: 1.2–1.7) compared to dry. On locations, the chances of having the disease were significantly higher in the south (OR 7.8; 95% CI: 4.5–13.7) compared to the northern part of the country. The prevalence of MD was higher which has increased over the years and it is endemic in Nigeria. Due to frequent outbreaks of MD, the importance of diagnostic surveillance of the disease and good management practices by farmers should be encouraged.