Annales de la Societe belge de medecine tropicale最新文献

In a longitudinal study we have observed the fluctuation in density of two Anopheles populations responsible for malaria transmission in a village built on a brackish lake. The two A. gambiae complex species are A. melas and A. gambiae s.s. The former is the most abundant (88%). The brackish lake ecosystem gives to both species possibilities of adaptation. The salt water species of the A. gambiae complex, A. melas, was found to be tolerant to waters with very low salinity. On the other hand, A. gambiae s.s. was found to support relatively high salinity rates. Both specimens live together the whole year round but their frequencies vary with the inundation of the lake. During inundation the salt rate decreases and A. melas eventually disappears. Transmission is low, seasonal and short on the lake. It is perceptible between March and August. The inoculation rate (11 infected bites per man/year) is lower than what we have observed in other lagoon areas of Benin, or even in the city of Cotonou (33 infected bites per man/year). The low malaria transmission on the lake is probably due to the presence of an important population of A. melas with low infection rates and the widespread use of bed nets.

In this study, we compared four T. evansi detection tests (Direct examination, Card Agglutination mouse inoculation and Polymerase Chain Reaction (PCR) in a natural infection of dairy cattle in central Thailand. The samples for PCR amplification were collected either in microfuge tubes or on microscope slides and the amplification results were compared. Collecting the samples on slides was faster and more convenient than collection in tubes. Comparable results were obtained from PCR amplification of both tube- and slide collected samples, processed twelve to fourteen days after collection. PCR was the most sensitive of the methods under comparison, using the mouse inoculation test as golden standard. The specificity of the PCR test under study is further discussed in this paper.

An analysis was made of the mating scar pattern of female Glossina palpalis palpalis Robineau-Desvoidy and Glossina fuscipes fuscipes Newstead. Measurements on fifty permanent preparations of the mating scars of females reared in the laboratory revealed significant differences in the length, width and in the distance between the centers of the mating scars of the two species. Plotting the distance between the centers of the two mating scars against the ratio width/length resulted in a 93% separation of the two species. It is proposed that this technique could be used during field surveys to expose possible cross-breeding in nature or as a tool in the entomological evaluation of a tsetse eradication campaign where one species is released in the habitat of the other.

We report on the prevalence of schistosomiasis and geohelminth infections in Mali, Central West Africa, based on data from the National Schistosomiasis Control Programme of Mali (1982-1991) and from our recent surveys (1992-1993). Combined national figures and regional data are presented from both surveys. Schistosomiasis showed an overall prevalence of 30.1%, with lowest prevalence in Sikasso Region and highest prevalence in Segou Region. Ascaris lumbricoïdes (0.12%) and Trichuris trichiura (0.42%) were comparatively rare, but hookworm infections were more widespread (8.0%). No hookworm infections were detected in the arid northern Region and the highest prevalence (18.7%) was encountered in the humid south of the country. There was a significant positive relationship between the prevalence of hookworm infection and total annual rainfall per region. Overall the prevalence of concurrent infections with schistosomes and hookworms was significantly less than expected, although there were regional differences which were discussed in the light of local variations in climatic and other factors likely to affect transmission.

The authors describe the extension of an outbreak of bacillary dysentery among the Rwandese populations seeking refuge in the region of Goma, Zaire in august 1994. Analysis of the epidemiological surveillance data and of the bacteriological laboratory results of the Bioforce, show that this epidemic was probably facilitated by the preceding cholera outbreak. In such circumstances, rapid sterilization of the virus reservoir, by short course treatments, might be beneficial in limiting the extension of the epidemic.

A Columbian patient presented with a rare type of onychomycosis caused by Microsporum gypseum. Oral treatment with itraconazole formulation (Funazol) available in Columbia failed to improve the nail alteration. The fungitoxic effect of itraconazole was assessed on the M. gypseum strain cultured from the nail of the patient by using the method of culture of fungi on cyanoacrylate skin surface strippings (CSSS). In addition, a comparative evaluation of the oral bioavailability of itraconazole was made in volunteers after intake of Funazol and Sporanox. In the ex vivo bioassay on CSSS, topical itraconazole proved to be highly active against M. gypseum. After oral intake, however, the itraconazole bioavailability of Funazol relative to Sporanox averaged only 3.5%. Antifungal pulse therapy with Sporanox, 400 mg daily for 1 week per month for 4 months, cured the patient. This study shows that itraconazole is hardly or not absorbed from the oral formulation Funazol. Both the oral bioavailability and consequently therapeutic efficacy of the genuine drug (Sporanox) are highly superior.

The various stages of Plasmodium falciparum (sporozoites and liver stages, asexual blood stages and gametocytes) each interact in a particular way with the human immune system. Specific immunity against the liver stages is achieved through a coordinated action of CD8 T cells and specific antibodies, the latter in collaboration with NK cells and macrophages. In this reaction, interferon-gamma plays an essential role. A non-specific "concomitant" immunity against sporozoites is based on a cytokine reaction, elicited by the blood stages. In practice, the high variability in the immunogenic structures of the sporozoite precludes completely protection against recurrent infections. The spleen macrophages have a pivotal role in the immune defense against the asexual blood stages. The elimination of merozoites and parasitized red blood cells (RBC) is facilitated by specific antibodies, produced under the control of CD4 T cells. There are, however, multiple mechanisms of immune deviation, suppression and evolutionary adaptation, which inhibit a sterilizing immunity against the blood stages. Nevertheless, symptoms may be absent in exposed adults, even when parasitemia persists. This clinical resistance, however, is relatively short-lived, once exposition is interrupted. The observation that HIV infection has no adverse effect on malaria also is a remarkable but consistent finding. All these data indicate that a strong T cell-mediated immune memory is absent in human P. falciparum infections. Cerebral malaria and some other serious complications are the consequence of insufficient elimination of parasitized erythrocytes by the spleen, presumably in combination with parasite factors (particular variant surface structures) and with human host genetics (HLA type, blood group etc.). Parasitized RBC massively stick to the endothelium of the micro-vessels and non-parasitized RBC roset around the parasitized ones. Eventually, serious problems in the micro-perfusion and in the local metabolism occur and organ failure may finally ensue. The immune reaction against the surface-antigens of the sexual stage is limited and insufficient, most probably for similar reasons as in the asexual stages. Internal structures of the gametocytes, however, are highly immunogenic, but, unfortunately. Normally cannot be reached by the immune system. Based on these fundamental data, some of the perspectives of vaccination and new therapeutic tools are critically discussed.

This community based survey was undertaken to assess the prevalence, characteristics and risk factors of diarrhoea in children < 5 years of age in an urban zone, at Kinshasa, Zaire. 155 community cases selected by cluster sampling, 155 age-matched controls, and 18 children with diarrhoea seen at a health centre (HC) were examined. The diarrhoea prevalence rate was 6.5%. The highest risk of persistent diarrhoea was in children of 2 to 3 years, non breast-fed, with more than one enteric agent in their stools and living in households without electricity. The rates of detection of Strongyloides stercoralis, Entamoeba histolytica and Salmonella, and heavy infections of Trichuris trichiura and Trichomonas hominis were significantly higher in cases (p < 0.05). The rate of detection of Cryptosporidium was rather high, specially in HC cases (22.2%). It was also found in both diarrhoeal (14.8%) and non-diarrhoeal specimens (12.9%). There was a lack of association between the presence of faecal white blood cells and enteric bacteria, and also between the presence of faecal red blood cells and E. histolytica, which might be due to the frequent practice of rectal injections and suppositories. A mother's perception of fever and stool aspect was fairly in agreement (respectively 70% and 53%) with that of the investigators. The high rate of dehydrated children (50.9%) may be due to the dehydration definition applied at the HC. The survey's results were used to improve the local case management flow chart and to adjust educational activities directed at mothers.