Studies on the epidemiology, diagnosis and immunopathology of angiostrongyliasis costaricensis

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We performed epidemiological and seroepidemiological surveys of Angiostrongylus costaricensis infections in southern Brazil, and also we carried out experimental studies on the diagnosis and immunopathology of the disease. The results obtained are as follows:1. In southern Brazil, both slugs, Sarasinula linguaeformis and Phyllocaulis variegatus, are an important intermediate host for the parasite. We firstly revealed that another slug, Deroceras laeve, serves as an intermediate host. The prevalence rate of these slugs showed a distinct seasonal fluctuation and the actual prevalence rate of S. linguaeformis was 1.5% in August and 24% in December. A seroepidemiological study using ELISA assays indicated that the prevalence rate of local people in Nova Itaberaba, Santa Catalina, was 22% in August, 35% in December and 53% in April. The incidence rate every four months during this period ranged from 24 to 30%. Our verbal questionnaires to the people suggested that their infections would be … More caused by eating raw vegetables, possibly contaminated with mucus from infected slugs, or by using slugs as a bait for fishing and so on.2. Gelatin particle indirect agglutination test with crude A. costaricensis adult worm antigen was found to be useful for the immunodiagnosis of murine infections but not for the infections in other experimental animals and humans, since false positive reactions and a weak cross-reaction to A. cantonensis infection were noted. An improvement will be necessary for purifying antigens for the test. A monoclonal antibody recognizing a 162 kD antigen in excretory and secretory products by adult worms ofA. costaricensis was established. A dot-ELISA test with the monoclonal antibody successfully detected a circulating antigen in the sera from infected jirds and humans. However, some improvements will be necessary for increasing the sensitivity of the test and also for eliminating a weak cross-reaction to angiostrongyliasis cantonensis. To develop a genetic diagnostic method, a subtraction technique was applied to detect worm-derived DNA fragment(s) that would be possibly involved in the blood of infected animals. We have obtained several subtracted bands but not succeeded in detecting the worm-derived DNA yet. Differential screening was now in progress.3. Our studies using IL-5 transgenic and non-transgenic C3H/HeN mice demonstrated that eosinophils were possibly associated with host resistance to A. costaricensis, fecundity and intestinal pathology. Our studies with various strains of inbred mice and B1O congenic strains revealed that three strains with a low fecundity, i.e., BALB/c, DBA/2 and B10.D2, were resistant to A. costaricensis whereas two strains with a high fecundity, i.e., C57BL6 and C3H/HeN, were susceptible. The former three strains will be useful for developing a human model of abdominal angiostrongyliasis in the mouse. Less