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

A simple method to obtain large numbers of viable infective larvae (L3) of the human filarial parasite Loa loa in an endemic country is described: wild vector flies (Chrysops silacea and C. dimidiata) were caught in large numbers, sealed into pockets of mosquito netting, gently crushed on a glass plate and incubated in a funnel with medium ("Baermann technique"). 91-94% of the L3 actively left the crushed flies and accumulated in the funnel tip after 15 (80%) to 45 minutes (95%). During 111 catching days over a 12 month period, a single fly collector provided approximately 13,000 flies and 23,500 L3. The method is also considered useful for assessing loiasis-transmission, for example before and after mass treatment campaigns.

Two antimalarial prophylactic regimens were compared in 17 healthy volunteers. Regimen A consisted of daily ingestion of a single capsule containing 100 mg base chloroquine (CQ) and 200 mg proguanil (PG). Regimen B consisted of daily ingestion of separate tablets of CQ (100 mg base) and PG (two 100 mg tablets). Both treatments lasted for 12 days. Effective chloroquine levels were reached after 72 hours with both regimens (49.9 ng/ml for treatment A and 36.7 ng/ml for treatment B). Proguanil and cycloguanil plasma levels were significantly lower on sampling obtained at H3 (three hours later) and H6 (six hours later) on day 1 in the regimen A (p < 0.002). Thereafter there were no significant difference between the two regimens. Both regimens were well tolerated, but regimen A using the capsule appeared better accepted and facilitates compliance.

A community based malaria control intervention using insecticide treated mosquito nets (IMN) has been implemented and tested in 13 villages of the Yombo Division, Bagamoyo District in the Coastal Region, Tanzania, an area holoendemic for P. falciparum malaria. Following extensive sociological research into local perceptions of malaria, the programme was implemented. It wa decided by consensus that village mosquito net committees would be the appropriate local level implementors. These were formed and provided with IMN's which were sold to villagers at subsidised cost. The income was invested for use by the committees for sustaining the activity. Use patterns were determined and high coverages were obtained among the community, particularly after promotions e.g. plays, school meetings etc. Malaria morbidity was measured among children 6-40 months of age in 7 index villages prior to the intervention in 1992 and in a comparison study between 3 villages using nets and 4 villages not using nets in 1993. Examination of the 7 cohorts of children was done from June to October each year covering the period of most severe transmission. The children using nets showed marked improvement in several malariometric indices. Following an initial clearance of parasitaemia with sulphadoxine/pyrimethamine, when compared with unprotected children, those with nets were slower to become re-infected (Relative Risk 0.45), had lower parasitaemias and showed marked improvement in anaemia (RR 0.47). Use of IMN's produced a 54% reduction in the prevalence of anaemia among young children. Attempts are being made to ensure that the programme is locally sustained.

Travellers to malarious areas are increasingly advised to carry an emergency medication for self-treatment of suspected malaria in absence of medical attention. However, no data are available so far how travellers cope with self-diagnosis and stand by treatment (SBT). We therefore investigated the frequency, circumstances and outcome of emergency self-treatment for suspected malaria in German travellers. 3434 travellers were recruited for an open prospective study by 28 different travel clinics in Germany. 2867 travellers (90.1%) who returned questionnaires after their journey were analyzed. 40 travellers (1.4%) reported about SBT during their journey. Significant Plasmodium falciparum antibody levels could be demonstrated in only 4 of 37 SBT users (10.4%). In another 127 travellers with febrile episodes but without SBT use, no malaria was indicated by follow-up and/or serology.

The genetic diversity of B. canis was investigated by restriction fragment length polymorphism analysis. For this purpose, we identified a Babesia canis specific DNA probe named pS8. This 1.2 kbp probe can detect as low as 20 pg of B. canis DNA. Results suggest that the pS8 probe is distributed in multiple copies throughout the genome though is probably not itself internally repetitious, i.e. not structured into blocks of tandem units. This probe reveals discrete hybridizing fragments in B. canis enzyme-digested genomic DNA. RFLP patterns obtained with the pS8 probe revealed a large genetic diversity between various isolates and led us to distinguish several clones derived from a single isolate. Results suggest that for a single isolate, the fingerprints obtained reflect those of a few quantitatively dominant clones. This technique can now be routinely applied and provides a convenient tool for the characterization and the identification of B. canis isolates, strains and clones.

Trypanosoma brucei rhodesiense isolates from South East Uganda were characterized for susceptibility to the drugs suramin, nifurtimox, melarsoprol and DL-alpha-difluoromethylornithine (DFMO). Two different assays were used to determine the drug susceptibility of the field isolates: the [3H]hypoxanthine incorporation assay (24 hours) and the long term viability assay (10 days). All trypanosome stocks were susceptible to suramin and nifurtimox. Differences in the susceptibility to melarsoprol were observed in the [3H]hypoxanthine incorporation assay, but could not be confirmed in the long term viability assay. All T. b. rhodesiense stocks were found in vitro to have innate tolerance to DFMO, under conditions where T. b. gambiense stocks from West Africa were susceptible to the drug. Ugandan T. b. rhodesiense stocks did respond to 25-100 micrograms/ml after 10 days of drug exposure, but the DFMO level reached in cerebrospinal fluid during treatment is only 16.3 +/- 7.8 micrograms/ml. Therefore, DFMO is not an appropriate alternative or backup drug for treatment of Rhodesian sleeping sickness in Uganda.

Five Paraguayan Trypanosoma cruzi strains, isolated from acute chagasic patients, were studied by their behavior in BALB/c mice, metacyelogenesis, bio-metry of metacyclic forms and lectin agglutination. Early and intermediate parasitemic peaks were observed and the strains did not show high virulence. Metacyclogenesis capacity was not higher than 50% in all cases and there were no considerable differences in the biometry. They all belong to WGA-type strains according to the lectin agglutination assays except for one strain that agglutinated with WGA and PNA lectins. Although previous schizodeme analysis of these strains showed rather homogeneous profiles, biological features were quite heterogeneous.

We report the first study of gonotrophic cycle duration, survival rates, pre-gravid rates, vectorial capacity and chromosomal polymorphism of Anopheles gambiae s.s. in Sierra Leone. In the village of Bayama in the Southern Province, An. gambiae was the only species found to be naturally infected with Plasmodium falciparum and it constituted 99.7% of 22,541 anopheline mosquitoes caught. Chromosomal studies revealed only An. gambiae s.s. out of 66 females examined for chromosomal polymorphism, 61 (92.4%) had the 2LA inversion in the standard arrangement. Other inversions observed in low frequencies included 2Rcu and 2Ru. We estimated a gonotrophic cycle length of three days and survival rate per gonotrophic cycle of 0.59 for this species. The mean daily survival rate of An. gambiae was 0.85 and the entomological inoculation rate was 1,235 infective bites/person/year. Blood-meal ELISA tests showed that the species was very anthropophagic and that there were an estimated 35.4 daily inoculations per infective case. The epidemiological significance of these entomological parameters is discussed in the light of parasitological results for nearby villages.

The objective of this investigation was to collect data concerning CS-antibody levels and duration of the immunological response to exposure of non-immune persons to a single malaria infection. For this purpose 156 specimens from 98 patients with confirmed falciparum malaria, 76 specimen derived from 64 patients with vivax malaria and sera from 32 patients who had not been previously to malarious areas were investigated by use of a commercially available ELISA testkit. All specimens from patients with falciparum malaria were also tested for merozoite-antibodies by an indirect fluorescence antibody test (IFAT). Positive levels of merozoite-antibodies were detectable in 89.1% of the specimen in this panel during the period between days 8 and 90 after onset of symptoms and decreased steadily thereafter. The test results were positive for CS-antibodies in 36.4% of the specimens from patients with falciparum malaria during the first 7 days after onset of symptoms. This figure increased to 55.8% during days 8-90 after onset and decreased to 38.9% in specimens which were tested later (91-1898 days). 11 specimens reacted positively to CS-antibody testing but negative in the IFAT. Therefore, the percentage of specimen detected by either IFAT or CS-ELISA was at 51.9% during days 0 and 7 (p < 0.001), 95.3% during days 8 and 90 (p = 0.039) and 44.4% for testing performed later (p < 0.001). CS-antibodies could also be detected in 5.3% of specimen from patients with vivax malaria while none of the sera from the malaria-negative control-group tested positive for CS-antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

The chemotherapeutic efficacy of diminazene aceturate (Berenil) and lithium chloride (LiCl) in relapse infection of trypanosomiasis was investigated in rats experimentally infected with Trypanosoma brucei brucei. The study showed that the combination of diminazene aceturate at (7 mg/kg) and LiCl (10 micrograms/kg) appeared more effective therapeutically than diminazene aceturate, or diminazene aceturate and LiCl and dexamethasone group, as more of the rats in the diminazene aceturate and LiCl treated-group remained aparasitaemic for longer days (60 days). Relapse parasitaemia occurred on days 10 and 12 in diminazene aceturate (7 mg/kg); diminazene aceturate (7 mg/kg) and LiCl (10 micrograms/kg) plus dexamethasone (1 mg/kg) treated group respectively, while relapse parasitaemia did not occur in the diminazene aceturate and LiCl treated group until day 20. Histopathological examination of the brain did not show any signs of inflammatory reaction in the diminazene aceturate and LiCl and dexamethasone treated group. However lesions associated with meningoencephalitis, such as cellular infiltration of mononuclear cells, perivascular cuffings and perivascular congestion and oedema were observed in the diminazene aceturate; diminazene aceturate and LiCl treated groups.