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

A new method for the quantification of helminth eggs in faeces was developed, in which 7.5% nigrosin in 10% formaldehyde mixed with 5% eosin yellow in 10% formaldehyde was substituted for the malachite green solution used in the standard Kato-Katz method. This modification revealed the eggs of parasites like Schistosoma mansoni, Ascaris lumbricoides, Trichuris trichiura and hookworms distinctly. The slides made with this new technique could be accurately read within one hour. Faecal smears from 100 pupils in Kigungu, Entebbe, Uganda, were studied with both methods. The egg counts of S. mansoni, A. lumbricoides and T. trichiura by both methods were equal. The modified method, however, showed significantly higher hookworm egg counts (p < 0.001). Hookworm eggs were equal one hour after preparation of the slides as 16 hours after preparation. The intensity of infection detected was higher with the modified method for both S. mansoni and hookworms.

Normal adult Dirofilaria immitis from a microfilaremic donor dog and D. immitis from donors rendered microfilaria (MF) negative by seven consecutive monthly doses of milbemycin oxime (500 micrograms/kg) were transplanted into three previously uninfected and untreated dogs. Two dogs received reciprocal combinations of treated and untreated D. immitis and the third received untreated adults of both sexes. A fourth dog served as an infected, milbemycin treated, non-transplanted control. Eleven weeks after pairing treated female with untreated male worms, a low-level microfilaremia developed in the recipient. Two of the three treated female worms recovered from this dog were non-fertile, and the third contained a small number of elongate and coiled embryos but no mature intrauterine (stretched) microfilariae (MFF). The dog receiving treated male and untreated female worms became microfilaremic after two weeks. Microfilaremia peaked at 37,000/ml 16 weeks after transplantation and declined over the next 20 weeks to 7,200/ml. Untreated females paired with treated males either became non-fertile or exhibited low numbers of developing embryos and MFF scattered throughout their reproductive tracts. Pairing of untreated male and female worms produced a mcirofilaremia during the second post-operative week, which plateaued around 15,000 MFF per ml. Females recovered after this pairing contained a normal pattern of embryonic development, including stretched MFF. There were no significant differences in the percentage composition or absolute numbers of developing and mature sperm in the reproductive tracts of treated and untreated male worms. However, the resumption of MF production in one milbemycin treated female worm after pairing with normal males and failure of treated males to sustain MF production in untreated female worms suggest that milbemycin oxime impairs the sexual competence of male D. immitis. This may explain the ability of this drug to bring about long term suppression of microfilaremia without immediate adulticidal activity.

The in vitro culture system is described in which Trypanosoma brucei rhodesiense (LOUTat.1) was grown with the human feed layer cell HL-60. The use of this system in determining the 50% growth Inhibitory Concentration (IC50) of unknown compounds for both the trypanosomes and the host cell was demonstrated. The data shows that several analogues of pentamidine have significantly reduced host cell toxicity but maintain or have increased typanocidal activity. The value of the trypanosome/HL-60 in vitro culture system as a rapid primary in vitro drug screen is discussed. Based upon the ability of this primary screen to predict potential drug efficacy, several analogues screened in vitro were then tested in vivo. The results of the in vivo tests confirmed the ability of the in vitro screen to predict drug efficacy, and also suggests that better analogues of pentamidine (less host toxicity and greater trypanocidal activity) can be obtained to treat human trypanosomiasis.

A two years study has been carried out in Alloukoukro, a traditional wet savannah village in the central region of Côte d'Ivoire. The productive breeding sites of malaria vectors are natural puddles and some man-made shelters around the village. 576 man-nights of capture have identified Anopheles gambiae s.l. and An. funestus as vectors of malaria in the study area. The low densities of An. phaorensis and An coustani implies that their possible role in transmission is very negligible. An. gambiae s.l. was the predominant species throughout the year with a mean of 19.2 b/m/n in 1991 and 13.6 b/m/n in 1992. The densities of An. funestus increased gradually during the rainy season and reached its peak values towards the end of the season. An. gambiae s.l. assures transmission throughout the year. An. funestus maintains a seasonal transmission which is spread over seven months. In 1991, each person would have received an average of 264.5 infected bites altogether with 204.5 infected bites from An. gambiae s.l. and 62 infected bites from An. funestus. In 1992, there would have been 196.5 infected bites per man with 160 and 36.5 infected bites respectively from An. gambiae s.l. and An. funestus. This study has shown that in wet savannah areas, the rainy season spreading almost all over the year, allows the breeding sites to retain water much longer and thus, to keep alive a more important residual vector populations capable to ensure malaria transmission even during the dry season. The great majority of infected glands (96.7%) were observed between 11 p.m. and 04 a.m. So, the large scale use of treated bednets has been therefore strongly recommended as key measure against malaria transmission in this area.

In vitro Plasmodium falciparum drug sensitivity was investigated in 115 brazzavillians children, between 1 year and 10 years of age. On the basis of clinical aspects, four groups were constituted: Group 1: 39 asymptomatic school children, Group 2: 16 children with uncomplicated malaria, Group 3: 40 with severe but not pernicious malaria and Group 4: 20 with pernicious malaria. The drugs tested were chloroquine (CQ), quinine (QN) and mefloquine (MQ). The sensitivity level was assessed by a 48-hour in vitro maturation test involving the uptake of tritiated hypoxanthine, the initial blood level of parasite being > or = 0.1% in all cases. For QN and MQ, the median IC50 values showed no significant difference related to clinical status, age or parasitaemia levels. For CQ, the proportion of resistant strains and the 50 inhibitory concentration (IC50) values were greater in the cases of children hospitalised for malaria but there were no differences related to clinical severity of these hospitalised children nor, within each group, to the age or parasitaemia levels. The percentage of subjects with an IC50 value greater than the 90 percentile of the IC50 of the asymptomatic group, which we propose as the severity index related to chemoresistance, was 15% for uncomplicated malaria, 38% for severe but non-pernicious forms and 35% for pernicious malaria. The IC50 for QN was significantly higher in CQ-resistant strains and there was a positive correlation for CQ vs QN and for QN vs MQ.

The in vitro cultivation of the filarial nematode Brugia malayi from the infective stage to the fourth and the young adult stage is described. Different culture conditions including cell-free systems and co-culture with different human lymphatic cell lines were compared. Cell-free systems reported by others to promote the in vitro development of the parasites to the adult stage failed to work, i.e. the parasite development stopped at the L4 stage and the larvae died after approximately 3 weeks. Cocultivation with each of the cell lines used enhanced the survival of the parasites. The best results were obtained employing the human T cell leukemia line Jurkat and human dermal fibroblasts as feeder cells in RPMI 1640 supplemented with 10% heat-inactivated human serum. This culture system allowed the cultivation of B. malayi for more than 7 weeks with an average growth of the larvae by factor 6.4 (0.77 +/- 0.035 cm) and a maximum growth by factor 10 (1.2 cm). 69% of the initially cultivated larvae (which corresponded to 100% larvae alive at that time) reached the fourth larval stage after 14 days, and 2.6% of the initially cultivated larvae (which corresponded to 17% of the parasites alive at that day) had reached the young adult stage by day 37 of culture. Parasites remained alive up to 52 days. During the first four weeks of culture, both the length and the periods of moulting of the in vitro cultivated filariae closely resembled those observed with B. malayi in vivo in rodent hosts.

In this paper, we report on the histochemical localization of prostaglandin synthase (E. C. 1.14.99.1) in mouse muscles following infection with Trichinella spiralis and the dynamics of their changes at different stages of disease. Our studies suggest that increased level of prostaglandin synthase activity in infected muscles of mice may be correlated with the degree of muscle injury by larvae and, perhaps, that increased level of enzyme ameliorates the functioning of muscle. The dynamics of prostaglandin synthase changes corresponds to the dynamic of the studied so far biochemical, histological and immunological indices.

The effect of various natural host odours on Glossina longipalpis, G. medicorum and G. tachinoides from catches in odour-baited biconical traps was analysed. Substances tested were ox urine, and the eight components of its phenolic fraction, as well as acetone and 1-octen-3-ol, both of which are present in ox breath. Ox urine increased the catch of G. tachinoides significantly by 1.2 times. Its phenolic fraction gave increases of up to 1.6 for G. longipalpis and 1.4 for G. tachinoides (significant in both cases). Adding acetone and/or 1-octen-3-ol to the phenolic fraction increased attraction of G. longipalpis and G. tachinoides significantly by up to 1.8 and 1.3 times, respectively. Octenol on its own increased the catch of all three species significantly by up to 2.2 times. Acetone alone, in combination with octenol or with the phenolic fraction reduced the catch of G. medicorum significantly to a level of 0.2. 3-Methylphenol and 4-methylphenol are those components of the phenolic fraction which showed the highest attractiveness on tsetse flies in the experiments. Several mixtures of both methylphenols and/or 1-octen-3-ol were tested as attractants for all three tsetse species.

A study on dengue control was undertaken in a poor urban area in Cúcuta, Colombia. The first objective was to describe people's knowledge, attitudes and practices regarding dengue fever, the transmission of the disease and possible preventive measures. The second objective was to analyse the infestation of the community with Aedes aegypti larvae, and the third objective to test the efficacy of Bti (Bacillus thuringiensis israelensis) with respect to the level and duration of reduction of Ae. aegypti larvae in water tanks. It was found that people had a very fragmentary knowledge about dengue and about the necessary protective measures which did not lead them to any action. The infestation of water containers, particularly the larger tanks, was very high (house index = 61; Breteau index = 96). The application of Bti in water tanks led to satisfactory results: For one month and longer, the water tanks treated with Bti were free of mosquito larvae. The effect was reduced by a lower dose, washing the tanks and a less potent formulation. People's acceptance of Bti was higher than that of temephos. Further studies are necessary to confirm the utility of Bti in dengue control.

Seventeen male and 39 female Liberian patients, one third of them children, were diagnosed as having hyperreactive onchodermatitis (sowda). They presented with itching (98%), asymmetric (98%), chronic onchodermatitis (median 5 years), and swelling of femoral lymph nodes (89%). The geometric means of the microfilaria (mf) densities were 1.0 mf/mg in children and 0.7 mf/mg in adults. These patients not only suffered from their skin lesions, and severe itching resulting in disturbance of sleep but also from social stigmata. They urgently needed treatment. Ivermectin was administered as a single oral dose of 150 micrograms/kg body weight. The following adverse effects were observed in 30 patients within the first 72 hours after ivermectin treatment: increase of pruritus (93%), aggravation of dermatitis (73%), fever (25%), headache (20%), myalgia (20%), painful swelling of lymph nodes (13%) and severe swelling of arm or leg (10%). Symptomatic therapy was sufficient. No dangerous or life-threatening side effects were observed. At follow-up examinations 1-2 months after ivermectin treatment, the prevalence of mf carriers had decreased from 100% to 19%. Seventeen out of 18 patients felt their dermatitis had improved. Evaluation of the dermatitis by a physician using a score from 0 (no dermatitis) to 9 (severe dermatitis) revealed a reduction of the score from 4.3 before treatment to 0.7 (84%) after ivermectin. In contrary, at the follow-up examination of 16 patients 6-12 months after ivermectin some recrudescences were observed. In this group the prevalence of mf carriers was 47%, 13 out of the 16 patients felt their skin lesions had improved and the score had decreased from 2.2 to 0.5 (77%). Consequently, it is recommended to administer ivermectin to patients with hyperreactive onchodermatitis every 3-4 months.