Parasitology

Research Article

Characteristics of granuloma formation and liver fibrosis in murine schistosomiasis mekongi: a morphological comparison between Schistosoma mekongi and S. japonicum infection

M. SHIMADAa1a2, M. KIRINOKIa1, K. SHIMIZUa3, N. KATO-HAYASHIa1, Y. CHIGUSAa1 c1, V. KITIKOONa4, P. PONGSASAKULCHOTIa4 and H. MATSUDAa5

a1 Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Mibu, Shimotsuga, Tochigi 321-0293, Japan

a2 Department of Internal Medicine, Ashikaga Red Cross Hospital, Ashikaga, Tochigi 326-0808, Japan

a3 Department of Pathology, Ashikaga Red Cross Hospital, Ashikaga, Tochigi 326-0808, Japan

a4 Department of Social and Environmental Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok 10400, Thailand

a5 Institute of International Education and Research, Dokkyo Medical University, Mibu, Shimotsuga, Tochigi 321-0293, Japan

SUMMARY

A histopathological study was performed to clarify the characteristics of granuloma formation and liver fibrosis in Schistosoma mekongi infection in comparison with S. japonicum infection. Mice were exposed to S. mekongi (Laotian strain) and S. japonicum (Japanese strain) cercariae, and were dissected at 6, 8, 12, 16, and 20 weeks post-exposure. In the liver, granulomas in S. mekongi infection were cellular, initially organized with foam cells, and continuously appeared in the intralobular area, while granulomas in S. japonicum infection were fibrous and did not continuously appear in the intralobular area. Portal fibrosis was not seen in S. mekongi infection, but was commonly seen in S. japonicum infection in the later weeks. Granulomas in the small intestine were seen mainly in the submucosa with foam cells in S. mekongi infection and without foam cells in S. japonicum infection. The lung granulomas contained mainly histiocytes in both S. mekongi and S. japonicum infection. The absence of portal fibrosis in S. mekongi infection allows schistosome eggs to infiltrate into the intralobular area continuously, which can be what lies behind the ultrasonographic differences; the echogenic network pattern as was seen in S. japonicum infection, has not been noted in S. mekongi infection.

(Received January 17 2010)

(Revised March 15 2010)

(Revised March 27 2010)

(Accepted March 29 2010)

(Online publication June 21 2010)

Correspondence:

c1 Corresponding author: Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, 880 Kitakobayashi, Mibu, Shimotsuga, Tochigi 321-0293, Japan. Tel: +81 282 87 2134. Fax: +81 282 86 6431. E-mail: ychigusa@dokkyomed.ac.jp

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