Newcastle disease virus vaccination enhanced severity of Escherichia coli infection in chicken

The present study emphasizes the effect of LaSota vaccination on the experimental E. coli infection in chickens. 160 chicks, 7 day old were divided into four groups of 45 birds each in groups A and group B and 35 birds each in groups C and D. The chicks of groups B and C were given LaSota vaccine by intranasal route @ 106 EID 50 per bird at the age of 7 days. At 15 days age, the chicks of groups A and B were injected with 107 CFU of E. coli O78/chick, intraperitoneally. The chicks of group D were kept as control. The clinical signs such as loss of body weight, anorexia and respiratory distress were more severe in group B. The percent mortality was more in group B (37.7%) as compared to group A (20%). The protective HI (> log24 with 4HA units) titre against New castle disease in both the vaccinated groups was noticed from 15th day post vaccination. The highest HI antibody titre (log2 6.80±0.37) was noticed in group B at 29 DPV. An overall increase in serum antibody titre against E. coli infection was observed in group B as compared to group A. The severity of gross and histopathological changes such as fibrinous pericarditis and perihepatitis was of higher magnitude in group B as compared to group A. It is concluded that administration of NDV LaSota vaccines enhanced the severity of colibacillosis in chickens as evidenced by clinical signs, mortality, immunological response and pathological changes.