Abstract
Acquired resistance against adult Echinococcus multilocularis infection was studies using golden hamsters harboring adult worms less than 25 days post-infection (PI). Sixteen, male 4-week-old golden hamsters were divided into 3 groups. Group A was orally inoculated with 20,000 viable protoscoleces followed by oral treatment with praziquantel at 23 and 25 days PI and then challenged orally with 20,000 viable protoscoleces at 40 days PI. Group B was intraperitoneally inoculated with 20,000 viable protoscoleces, then treated with praziquantel and challenged as described for group A. Group C served as control group without previous inoculation of protoscoleces, but was given praziquantenl and then challenged with similar infection dose as described for group A. All hamsters were killed at 5 days after challenged inoculation. The mean numbers and standard deviation (SD) of adult worms recovered in groups A, B and C were 30.2±17.9, 103.7±45.1 and 594.6±71.2, respectively. Significant differences were recognized between groups A and C, and between groups B and C using ScheffeÕs test (p<0.001). Specific serum IgG measured by an indirect ELISA using E. multilocularis somatic antigen was clearly elevated in group A and B. These findings indicate that hamsters with previously established infection acquired resistance and the level of specific IgG was also increased in their sera. This study suggests that the alternative definitive host model using hamsters could be useful for immunological studies related to assessment of vaccines.
Key words: Echinococcus multilocularis; golden hamster; acquired resistance; antibody response; experimental model.