Infection of chicks with infectious bursal disease and its effect on the carrier state with Newcastle disease virus
Pattison, M.; Allan, W.H.
Veterinary Record 95(3): 65-66
1974
ISSN/ISBN: 0042-4900 PMID: 4374792 Document Number: 73925
Two groups (A and D), each of ten one-day-old SPF chicks, were given by eye drop 105 CID50 homogenized infected bursae. At 5 weeks of age, group C (SPF chicks having received no IBA) and D were given eye drops containing 106.7 ELD50 of the mesogenic strain of NDV. Swabs were taken from the trachea and posterior nares twice a week, and incubated in peptone broth before being inoculated into eggs. HI levels in chick bloood were estimated 11 and 21 days after NDV infection. 21 days after NDV infection, groups B (SPF chicks having received no IBA or NDV), A, C and D were challenged with an aerosol dose of 1010.7 ELD50 of the virulent Essex 70 strain of NDV. Results are tabulated. Birds in groups A and B showed no HI titre and died on challenge with virulent virus. Of the 10 birds in group C, all yielded virus on day 4 after receiving mesogenic virus, and 6 on day 7, but thereafter swabs were negative. HI titres on days 11 and 21 after infection with mesogenic virus were 28 and 28.5 respectively, and all birds survived the challenge with virulent virus. Of the birds in group D, all yielded virus on days 4 and 7 after infection with mesogenic NDV, and 5 yielded virus on day 11. Thereafter the reaction took three forms: three birds died, 5 developed negligible HI titres and persistently excreted virus (though the immune response was increasing by 21 days after infection), and 2 developed comparable HI titres to those birds which had received no IBA, and subsequently eliminated the virus. Hence early inoculation with IBA appears to suppress the immune response to NDV in some birds, delay the immune response to NDV in others, and to have no effect on the immune response to NDV in the remainder. IBA infection early in life would thus tend to increase the disease rate and prolong the period of virus excretion after NDV infection.