Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ)最新文献

The intraerythrocytic stages of the human malaria parasite Plasmodium falciparum induce a variety of physiological changes of the host erythrocyte. Many proteins are secreted from the parasite and are subsequently found at specific locations within the host cell. To elucidate the importance of protein secretion for parasite survival, infected red blood cells (IRBC) were subjected to the fungal metabolite brefeldin A (BFA) and to incubation at 15 degrees C, treatments that inhibit protein secretion and parasite development. Evidence is provided that retardation of parasite development in the presence of BFA correlates with an inhibition of protein secretion. Incubation at 15 degrees C and BFA reversibly arrest parasite development at the ring stage. Arrested ring stages loose 50% of their competence to develop to trophozoites after 1.5 days of treatment with BFA and after approximately 4 days at 15 degrees C. BFA affects development of trophozoites at concentrations similar to those required to arrest rings. In contrast to rings, the viability of trophozoites cultured at 15 degrees C or in the presence of BFA is completely abolished within 24 h.

A total of 2193 people in 14 villages on 9 islands was examined for microfilaria (mf). The average mf rate of those examined was 2.6%. High mf rates of 7-10% were obtained in 3 villages on 3 islands. Analysed by sex and age, the highest mf rates were observed among males of age > or = 20 years (6-10%). A clinical study conducted on 466 adult males of age > or = 15 years showed that the average hydrocele rate was 3.4% and that of elephantiasis 0.4%. For the ages > or = 50 years the hydrocele rate was nearly 10%, indicating that filariasis is an important public health problem. Filariasis in Chuuk seems to be decreasing, but some endemic villages found in the study imply the existence of many unknown and thus unattended foci of filariasis in Pacific islands.

An enzyme linked immunoelectrotransfer blot technique (EITB) was developed and evaluated for the serodiagnosis of Chagas' disease. EITB strips were prepared using Trypansoma cruzi (Y strain) epimastigotes lysate. Evaluation was performed with 235 serum samples collected from individuals living in an endemic area for Chagas' disease. Among those samples, 160 were serological positive in three conventional tests for T. cruzi and 75 were negative. The specificity was determined using 37 serum samples from patients with other infectious diseases. The EITB test showed sensitivity of 99.3% and specificity of 100% when a positive reaction was defined as the presence of 3 bands from a group of 7 (14, 19, 27, 30, 34, 37 and 75), a negative reaction was defined as the absence of 6 of the 7 bands, and an indeterminate reaction as the presence of two of the 7 bands.

The cytotoxic effects of neutrophils co-cultured with infective third-stage larvae (L3) and autologous serum from three groups of individuals: infected (INF), non-patent endemic normals (EN) and non-endemic controls (NEC), were compared using a MTT (3-(4,5 dimethylthiazol-2yl)-2,5 diphenyl tetrazolium bromide) reduction assay as a biochemical parameter of larval viability. The MTT assay permitted the detection of L3 which had suffered varying levels of necrosis. The observations from this study indicate that infected individuals and endemic normals are capable of mounting a specific immune response against the infective L3. This is based on our findings of i) significantly greater numbers of L3 showed necrosis in neutrophil cultures of the INF and EN compared to those from the NEC, ii) a superior ability of cultures from these individuals to inhibit the molting of L3 to fourth-stage larvae, iii) IgG antibodies reactive with the surface of L3, detected by immunofluorescence in the serum of the INF and the EN and iv) recognition of specific antigens in extracts of L3 detected by Western blot analysis. The specific immune response directed against L3 is probably a significant immunological defense mechanism used to limit infection in endemic areas.

Culture forms of the potentially pathogenic Entamoeba histolytica were compared to those of the nonpathogenic species of E. dispar, E. hartmanni, E. coli, Endolimax nana, and E. moshkovskii regarding the sensitivity to lysis by human complement activated through the alternative pathway. E. dispar was found unique in its complement resistance; all other nonpathogenic isolates resembled E. histolytica in that they were complement sensitive. Thus, a state of complement sensitivity is not a particular property of potentially pathogenic amoebae.

In preparation for mass distribution of ivermectin to control onchocerciasis in the Thyolo highlands of Malawi a survey was conducted to determine knowledge and attitudes toward onchocerciasis which could assist in developing educational messages. Since onchocerciasis is not known by a specific name in the Thyolo highlands, information was sought about individual perceptions of common symptoms of infection. Itching, skin thickening, nodules, or depigmentation (leopard skin) were reported by 95% of those interviews. Effective treatment was often thought by the community to be available when actually it was not. Traditional healers were not thought to be an important source for treatment of lesions associated with onchocerciasis. None of those interviewed associated Simulium damnosum s.l. with any symptoms other those related to the actual bite. Based on the information gathered, various options for ivermectin educational messages are discussed.

The glycoprotein, gp30, is the major soluble cuticular antigen of the adult lymphatic fiarial worm Brugia pahangi (Maizels et al., 1983, Devaney, 1988). Cookson et al., 1992 suggested that gp30 may function as an antioxidant enzyme protecting B. pahangi from the vertebrate host defence mechanism. In this communication we report that the gp30 transcript is present in each of the life cycle stages, including mosquito derived L3's, and that there is a 50 fold increase in the transcription of gp30 in young adults (28 days post infection) compared to mature adults. These findings suggest that gp30 performs a general function relevant throughout the B. pahangi life cycle and in particular to young adults.

In many previous characterization studies of Trypanozoon, isolates have been subpassaged numerous times in laboratory rodents until a quantity of trypanosomes sufficient for analysis has been obtained. In addition to the numerous biochemical effects of such a process on the parasite, it appears probable that adaptation to an unnatural host may also serve to filter out less virulent populations from mixed infections, leading to an underestimate of the true level of genetic diversity. By the early cloning of trypanosomes from susceptible captive flies infected from the primary isolate--the midgut of a wild tsetse--the present study provides evidence of the range of genetically different Trypanosoma brucei populations which may coexist within the midgut of individual tsetse flies in nature. The three primary isolates from tsetse yielded one, five and nine genetically distinct populations. Cloned populations were confirmed as T. brucei using the polymerase chain reaction, and were characterized by karyotype analysis and multilocus isoenzyme electrophoresis. These data allowed a limited assessment of the level of genetic variability in natural populations of T. brucei.

Human- and snail-related aspects of transmission of urinary and intestinal schistosomiasis were studied in the Tono Irrigation Scheme in northern Ghana. The scheme became operational in 1977. In some schools, prevalences and intensities of both Schistosoma mansoni and S. haematobium infection were alarmingly high, pointing to human schistosomiasis being at least focally a health problem of major public health concern. Positive correlations between intensity of schistosome infection, as measured by egg output, with frequency of visible haematuria and history of haematuria point to opportunities for community-based assessment of morbidity and identification of high risk population subgroups. Bulinus globosus is the most important snail host for S. haematobium while Biomphalaria pfeifferi serves as host for S. mansoni. While transmission of S. mansoni is taking place only in the main canal, transmission of S. haematobium takes place in all parts of the irrigation system (lateral canal, night storage dam, main reservoir). Transmission of both S. mansoni and S. haematobium is rather focal and a seasonal pattern of transmission is indicated with peak transmission taking place during the beginning of the dry season. The high endemicity and the transmission patterns described in this study call for an integrated approach to schistosomiasis morbidity control in the area.

A 43 year old woman developed a painful tumor at the left buccal mucosa. Following local anti-inflammatory treatment a 35 mm long, living female adult worm of Gongylonema pulchrum was extracted from the affected side. No further treatment was needed and recovery was complete 5 days after extraction. Infection had occurred possibly 6 weeks before in Hungary with ingestion of contaminated water from an open draw well. Although commonly occurring as parasitic infection of domestic cattle and other vertebrates, gongylonemiasis is very rare in humans. Only 48 cases have been described in the literature since 1864. Life cycle and pathology of G. pulchrum are discussed.