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Korean J Parasitol > Volume 27(2):1989 > Article

Original Article
Korean J Parasitol. 1989 Jun;27(2):119-130. Korean.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1989.27.2.119
Copyright © 1989 by The Korean Society for Parasitology
Effect of praziquantel treatment on pulmonary lesions of rats infected with Paragonimus iloktsuenensis
S H Lee,S Y Kim,Y C Han,*Y S Lee,**S T Hong,W M Sohn,†† and J Y Chai
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Seoul 110-460, Korea.
*Department of Internal Medicine, College of Medicine, Seoul National University, Seoul 110-460, Korea.
**Department of Legal Medicine, College of Medicine, Seoul National University, Seoul 110-460, Korea.
Department of Internal Medicine, College of Medicine, Chungnam National University, Daejon 301-764, Korea.
††Department of Parasitology, College of Medicine, Inje University, Pusan 614-112, Korea.

An experimental pathological study was performed to observe the effect of praziquantel treatment on the pulmonary lesions of the rat lung fluke, Paragonimus iloktsuenensis. The metacercariae were obtained from the freshwater crab, Sesarma dehaani, and 40 rats (wistar) were fed each with 10 metacercariae. On 20 rats praziquantel treatment (100mg/kg/day × 5 days) was done at 5 weeks after the infection while remaining 20 rats were kept untreated for use as controls. The drug-treated rats and the untreated ones were sacrificed 3, 7, 14, 21 or 28 days later for the observation of lung pathology. The rats infected with P. iloktsuenensis showed remarkable pulmonary changes; gross features of hemorrhagic and nodular worm capsules protruded on to the surface of the lung, and histologically local atelectasis, inflammatory cell infiltration, and egg granuloma around the worm capsules each containing one or two worms. Praziquantel treatment of the rats was shown to be highly effective in killing the worms and to lead them to degenerate, as early as in 3 days post-treatment. Almost all worms in the lung were dead and absorbed by the host cells in 21 days post-treatment, except a few living ones seen in a rat of 14-day post-treatment group. In most of the rats treated the pulmonary lesions showed the signs of resolution; regression of worm capsules with mummification of worms, decrease of inflammatory cell infiltration, improvement in the degree of atelectasis, and decreases in the frequency and size of the egg granuloma. From the results it is concluded that praziquantel is highly effective for the treatment of rat P. iloktsuenensis infection in the lung, not only by its direct killing effect of the worms but also due to the excellent resolution capacity of the pulmonary tissues.


Figs. 1-6
Fig. 1. Gross feature of a normal, uninfected rat lung. Scale: mm.

Fig. 2. A rat lung infected with P. iloktsuenensis, 6 weeks after infection. Untreated control group. Note two large worm capsules (arrows) protruded on to the surface of the lung.

Fig. 3. Another infected rat lung, 9 weeks after infection, showing persistent worm capsules.

Fig. 4. A rat lung, 7 days after treatment with praziquantel, which shows a regressing worm capsule (arrow).

Fig. 5. A rat lung, 21 days after treatment, which show two old worm capsules in healing process (arrows).

Fig. 6. A rat lung, 28 days after treatment, showing an almost healed lesion (arrow).

Figs. 7-12
Fig. 7. Section of a normal rat lung showing no abnormality except slight congestion. ×100.

Fig. 8. Section of a rat lung infected with P. iloktsuenensis, 5 weeks after infection. Untreated control group. Note 2 worms surrounded by a big worm capsule (arrows). ×40.

Fig. 9. Magnification of Fig. 8 showing worm tegument (T), vitelline follicles (V) and intestines (I). Eggs are also seen outside of the worm being embedded in the worm capsule. ×100.

Fig. 10. A 7-week post-infection group, untreated, showing two worms in a fibrotic worm capsule. ×40.

Fig. 11. The same rat as in Fig. 10, other part, showing an egg granuloma where many aggregated eggs and infiltration of inflammatory cells are seen. ×200.

Fig. 12. A 8-week post-infection group, untreated, showing numerous eggs around a worm capsule. ×100.

Figs. 13-18
Fig. 13. Section of a rat lung infected with P. iloktsuenensis, praziquantel treatment group, 14 days after the treatment. In this rat host, the worm is still alive in spite alive in spite of drug administration. ×100.

Fig. 14. Another praziquantel treatment group showing a remarkably destroyed worms (arrows) but still with a sucker, 3 days after the treatment. ×100.

Fig. 15. A praziquantel-treated rat lung, 7 days after the treatment. The worm (arrows) is in its autolyzing process showing its dark vitelline material. ×100.

Fig. 16. Another treatment group, 14 days after the treatment. The worm (OS: oral sucker) inside the worm capsule (Cap) is autolyzing or mummifying. ×100.

Fig. 17. Another rat of the same group as in Fig. 16, showing a living parasite (P. iloktsuenensis) retaining its intact tegument and spines, though they are surrounded by the host cells such as eosinophils and histiocytes. ×200.

Fig. 18. A treatment group, rat lung 7 days after the treatment. Note increased collagen fibers in the wall of the worm capsule. ×200.

Figs. 19-22
Fig. 19. A rat lung showing a worm capsule of P. iloktsuenensis that has remarkably regressed in size, 28 days after praziquantel treatment. A dead worm is seen to be absorbed by the surrounding host tissue cells. ×100.

Fig. 20. Magnification of other portion of the same rat lung as in Fig. 19, showing a degenerating worm and invading host cells into the worm tegument. ×200.

Fig. 21. A rat lung of praziquantel-treated group, 28 days after the treatment. A dead worm (arrows) has been entirely mummified and is only retaining egg shells. ×100.

Fig. 22. Another protion of the same group as in Fig. 21, showing normalized lung tissue (left side) and a healing worm capsule with two small egg granuloma (right side). ×100.


Table 1
Number of rats by experimental group

Table 2
Histopathological findings of the rat lung infected with P. iloktsuenensis

Table 3
Post-treatment histopathological finding of the rat lung infected with P. iloktsuenensis

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