Immunosuppressive effect of Cryptosporidium baileyi infection on vaccination against Newcastle disease in chicks

摘要

Hemagglutination-inhibition titers (log₂) to Newcastle disease (ND) virus were chronologically observed in chicks, which were orally inoculated with 5 × 105 oocysts of Cryptosporidium baileyi at 2 days of age and subsequently vaccinated with inactivated ND virus at 4 and 21 days postinoculation. In general, the titers were considerably lower in the infected chicks than those in the uninfected control throughout the experimental period (p 0.01), and rapid negative seroconversions were observed in the infected chicks. The titers reached a peak on weeks 2 and 4 post-booster-vaccination in the control and infected chicks, respectively. Thus, C. baileyi infection was shown to have an immunosuppressive effect on ND vaccination when the agent was given to 2-day-old chicks. It is suggested that C. baileyi infection in chicks may increase the host susceptibility to ND virus.