Abstract

In order to understand the tissue responses of albino rat host against Paragonimus iloktsuenensis infection, the histopathological changes of the spleen and the lungs in 6 experimental groups of rats were observed in relation with the growth, maturation and migration of this lung fluke. Rats of the experimental groups, each group consisted of 5 rats, were infected with the metacercariae of P. iloktsuenensis which were isolated from brackish water crab, Sesarma dehaani, and were kept for 3 days, 3 weeks, 4 weeks, 7 weeks, 10 weeks and 14 weeks of infection period. Peripheral blood smear slides for the differential leukocyte count were prepared and also worm collection was completed immediately after the infection period. Paraffin sections of the spleen and the lung tissue were stained with hematoxylin-eosin and methyl-green-pyronin (MGP) stain. Those materials from the experimental groups were examined in comparison with the materials obtained from control group, with special reference to immunologic aspects of host response. The results obtained were as follows: The counts of large pyroninophilic cell (LPC) in the periarterial sheath of spleen were rapidly increased in earlier period of infection, and those of peribronchial lymphatic tissue started to increase after the penetration of lungfluke into the lungs. The LPC counts of both the spleen and the lungs were on the decrease in conjunction with the necrosis of the lung fluke in 14th week of infection. On observing differential leukocyte count of peripheral blood smear, the fluctuation of lymphocyte count was proportional to that of LPC count, and the lymphocyte count was consistently higher than that of normal rats. On the other hand, neutrophil count of experimental group showed reciprocal relation to the LPC counts. The nature and characteristics of pulmonary lesion produced by the P. iloktsuenensis were just the same as those produced by P. westermani. The lesions were represented by thick and fibrosclerotic cavern, granuloma due to eggs, pneumonic process and cellular infiltrations.