Occurrence of myocarditis in rodents infected with Schistosoma mansoni.

Myocarditis is a complication of Schistosoma mansoni infection, although the literature does not provide much information regarding the frequency of myocarditis. In order to analyze the relationship between myocarditis and S. mansoni infection, different laboratory animals were infected with different dose of cercariae. At different weeks of post infection the hearts of infected animals were collected and processed for histopathological examination. Myocarditis was characterized by interstitial inflammatory cell infiltration with or without granuloma. ddY and ICR infected mice showed eosinophilic egg-granuloma in the heart where as neither eosinophil nor egg-granuloma were observed in the heart of infected gerbils. Higher number of eosinophils and greater size of the granuloma were found in the ddY mice than ICR mice. The number of eosinophils was significantly higher in severe myocarditis. Incidence of myocarditis was higher in ddY mice (69% with 100) than ICR mice (35%) and gerbils (23%). The results indicate that ddY mice were more susceptible to S. mansoni infection in the development of myocarditis and myocardial severity was associated with greater eosinophil infiltration. These findings suggest that eosinophils might be involved in the development of myocarditis, although the involvement of immunological reaction can not be ruled out.

Immunization of laboratory animals with ultraviolet-attenuated larvae against homologous challenge infection with Trichinella britovi.

Immunogenicity of Trichinella britovi (Japanese isolate, cord ISS 408) muscle larvae irradiated with 5 mJ/cm2 of short wavelength ultraviolet (UV) was studied using homologous challenge infections. SCID mice vaccinated with UV-attenuated larvae showed no resistance, although its congenic CB-17 mice exhibited remarkable immunity. Following challenge vaccinated Mongolian gerbils, Meriones unguiculatus, did not show significant immunity. Use of these animal models vaccinated with UV-attenuated larvae will contribute to the investigation of immune mechanisms against Trichinella infection and also to the development of a vaccine of trichinellosis.

Features of Schistosoma mansoni infection in SCID mice.

Features of Schistosoma mansoni infection in SCID mice, which lack functional T- and B-lymphocytes, were investigated. The retarded development of parasites as well as reduction of liver egg recovery in SCID mice was significantly lower than those in congenic counterpart C.B-17 mice. Furthermore, the rate of parasite recovery from SCID mice with primary infection was always lower than that from C.B-17 mice by 20%, showing the innate resistance to S. mansoni infection. SCID mice vaccinated with UV-attenuated S. mansoni cercariae did not show protective immunity against a homologous challenge infection. The present innate resistance exhibited in SCID mice is discussed in relation to cell mediated immunity of macrophage activation by IFN-gamma which would not involve T-lymphocytes but is initiated by IL-12 and TNF-alpha cytokines. SCID mice may provide novel information on the host-parasite relationship in schistosome infections.

Schistosoma mansoni: relocation of parasites to lungs from hepatic portal system in rodents.

The prevalence and development of adult worms in the lungs of mice and gerbils infected with Schistosoma mansoni was investigated. All infected BALB/c mice harbored the schistosomes in their lungs at 10-12 weeks post-infection, showing the distinct relocation of adult worms to the lungs, from the hepatic portal system. The male and female flukes from lungs of BALB/c mice were significantly smaller than those from livers. The percentage of gravid females in lungs was considerably lower than that in the livers. The number of eggs recovered from lungs of BALB/c mice and gerbils having lung female worms, however, was higher than that from animals without lung females, indicating egg deposition of lung females. The number of eggs detected in the brains correlated well with the number of eggs from the lungs in BALB/c and ICR mice. Out of 119 infected gerbils at 8 weeks post-infection, only two animals had egg-emboli in the brain vessels, although many eggs embolized in the lungs of those animals. These data suggest that transfer of worms to the lungs from livers involves reduction of worm recovery from the portal circulation, and also pulmonary pathology of the disease.

Application of alcohol- or acetone-fixed Schistosoma eggs as an alternative to lyophilized eggs for the circumoval precipitin test.

Antigenicity of Schistosoma mansoni and S. japonicum eggs preserved in ethanol or acetone were assessed in a circumoval precipitin (COP) assay. The egg antigens were found to retain sufficiently their COP reactivity for the diagnosis of both schistosomiasis mansoni and japonica, although their reactivity became lower than that of lyophilized eggs. These alternative preparations for COP tests have advantages, such as keeping eggs directly in fixatives soon after the egg-purification process. Furthermore, evaporation-process may cause eggshell cleavages which facilitate the reaction. The possible usefulness of those eggs in COP assays in local endemic areas is discussed.

Gnathostoma malaysiae Miyazaki and Dunn, 1965 from Rattus surifer in Thailand.

Gnathostoma malaysiae Miyazaki and Dunn, 1965 was found in the stomach wall of Rattus surifer, captured in Phuket Island and Khao Yai National Park of Thailand. This is the first to be recorded in Thailand and the second discovery after the first description of Miyazaki and Dunn (1965). Pathological findings of infected animals were also described. Some new morphological descriptions were added to the original.

Circumoval precipitin (COP) test using air-dried eggs of Schistosoma japonicum and S. mansoni.

In an attempt to establish a simplified circumoval precipitin (COP) test for the diagnostic purpose of schistosomiasis, air-dried eggs of both Schistosoma japonicum and S. mansoni were tested as antigens for this assay. Twenty-six sera from mice infected with S. japonicum showed positive COP reactions as assessed by air-dried eggs. Among 36 serum samples from patients with schistosomiasis japonica, five exhibited false negative reaction when assessed with air-dried eggs and showed a minimum level of COP reaction when assessed with lyophilized eggs. Similarly, all of 30 serum samples from jirds (Meriones unguiculatus) infected with S. mansoni gave positive COP reaction when assessed using air-dried egg. Diagnostic sensitivity of air-dried egg-system was comparable to those of fresh egg-or lyophilized egg-systems. A simple COP technique employing air-dried eggs, instead of lyophilized or fresh ones, would be thus useful for the serodiagnosis of schistosomiasis in local endemic areas, where sophisticated laboratory facilities are not available.