INTERACTION OF CHICKEN ANEMIA VIRUS AND CRYPTOSPORIDIUM-BAILEYI IN EXPERIMENTALLY INFECTED CHICKENS

The natural occurrence of concomitant chicken anaemia virus (CAV) and Cryptosporidium baileyi infection was described earlier. In this exper iment, 1-day-old chickens were infected with cav alone (anaemia virus infected, Al) or followed by inoculation with 8x10(5) C. baileyi oocys ts orally at 1 wk of age (anaemia virus and Cryptosporidium infected, ACI). Another group of chickens received the same dose of C. baileyi o ocysts without previous virus infection (Cryptosporidium infected, CI) , and two groups of uninfected chickens served as controls. Except one group (uninfected control, UC), all groups - including the other cont rol group (challenged control, CC) - were challenged with an oral inoc ulum of 8 x 10(5) C. baileyi oocysts at the age of 4 wk. Haematologica l, serological, immunohistochemical and pathological findings confirme d the effect of the virus agent. The individual C., baileyi oocyst she dding did not show significant difference between group CI and ACI, ho wever, after challenge infection the AI chickens shed approximately th ree times more C. baileyi oocysts than those in group CC. Mortality an d the percentage of birds that developed anaemia was significantly hig her among ACI than AI chickens, while haematocrit values at 2 wk of ag e and relative bursal weights at 4 wk of age were moderately lower in the ACI group. The results presented here suggest that concurrent CAV infection increases the reproductive potential of C. baileyi in chicke ns, and both pathogens have synergistic effect on each other. (C) 1998 Elsevier Science B.V.