STUDIES ON THE INFLUENCE OF AGE IN THE INFECTION OF CAGED CHICKENS BYRAILLIETINA-LATICANALIS AND ON THE SUSCEPTIBILITY TO REINFECTION

The aim of the experiments was to explain the high number of worms fou nd in chickens from a poultry facility. Infections by Raillietina lati canalis were achieved in chickens kept in the laboratory. Thirty cysti cercoids obtained from beetles (Dermestes ater) caught at the poultry facility were administered by pipette to each chicken. The rate of rec overed worms was employed to evaluate the persistence of the infection , the influence of bird age on susceptibility to infection, and the po ssibility of reinfection. To verify the persistence of the infection, a group of ten chickens was infected. At each of five different interv als, two chickens were necropsied. Tapeworms were recovered up to the 46th day. To verify the influence of bird age on susceptibility to inf ection, three different age groups were used in the experimental desig n: 3-4 weeks, 6-9 weeks, and 17-20 weeks. There was no difference in s usceptibility to the infections across the groups. To investigate the possibility of reinfection, a group of birds received an additional do se of cysticercoids a few days after the first doses. Another group re ceived the second dose only after the worms had already been establish ed. There was a significant increase in the number of recovered worms in both groups when compared with the control. The short worms found i n some experiments may be due to natural destrobilisation. Thus, the h igh number of worms found in chickens from the poultry facility could result from both infections being acquired earlier and infections acqu ired at the laying stage, since we demonstrated the possibility of rei nfection and the long lifespan of the worm. If destrobilisation occurs in the same manner in chickens from the poultry facility, the longer worms found in them must be younger than the short ones.