不同蚊宿主体内马来丝虫微丝蚴黑化的实验比较

羽化1～2天的中华按蚊.致倦库蚊和白纹伊蚊分别胸内接种马来丝虫微丝蚴,在接种后的第3、4、5和9天,分头、胸、腹3部解剖计算各种蚊虫体内黑化微丝蚴及发育各期幼虫。结果表明:中华按蚊、致倦库蚊和白纹伊蚊的微丝蚴黑化率分别为51·6％、86·1％和69·5％,差异显著;3种蚊虫体内的感染期幼虫率及感染期幼虫阳性率分别为35.3％、1·6％、0％和83·9％、23·5％、0％。黑化微丝蚴较多地集中在蚊虫腹部,占黑化微丝蚴总数61·6％～78·4％。     

Assessment of vector microfilarial uptake as a comparatively non-invasive technique for monitoring onchocerciasis treatment campaigns in the Americas

Summary Since 1992, efforts have been made to combat onchocerciasis in Guatemala through mass distribution of ivermectin. The impact of the campaign is assessed by taking skin-snips from sentinel groups within selected communities. This method gives an estimate of the prevalence and intensity of infection, and thus the efficacy of the treatment. In some communities people are becoming reluctant to volunteer for skin-snipping, and so there is a need for an alternative technique that will give quantitative results. In most hyperendemic communities in Guatemala, biting blackflies are so ubiquitous that few people object to allowing 10 to 20 flies to engorge upon them. We examined data on the quantitative uptake of microfilariae by Simulium ochraceum before and after ivermectin distribution to see whether results similar to skin-snip data could be obtained. Counts of microfilariae ingested by S. ochraceum are compared to the numbers found in skin-snips from the same volunteers. In a group of 31 untreated infected persons, a skin-snip survey detected 64.5% positive, while feeding flies (vector microfilarial uptake, VmfU) detected 96.8%. Post-treatment, in a sample of 58 of whom 52 (89.7%) had a history of infection, both skin-snips and VmfU detected 54.2%. Vector blood meals contained more microfilariae than a mg of skin before treatment, but both recorded about equal numbers after treatment. When the data set was subdivided to compare samples taken at 2–3, 6–8 and 14–17 months post-treatment, the effect of ivermectin was still apparent at 6–8 months, but had virtually disappeared by 14 months post-treatment. A surprising observation was that the flies ingested fewer microfilariae from treated persons than was expected from the skin densities as estimated by skin-snip. This effect lasted for over 8 months, and could indicate that ivermectin has a greater effect on transmission than previously suspected. We conclude that VmfU could be used as an alternative to skin-snipping, and discuss the ethical implications.     

Filarial infection is resisted differentially by subjects having different blood group phenotypes

This study was aimed to elucidate the relationship between major blood group antigens (BGAs) and susceptibility or resistance to human lymphatic filariasis. A total of 492 human subjects, living in Raipur city of Chhattisgarh, endemic for bancroftian filariasis in Central India, were screened for the presence of Wuchereria bancrofti microfilariae and disease manifestations. The frequency of BGAs was tabulated as a function of the status of filariasis, namely normal (no infection), mf carrier (presence of microfilariae in blood), and elephantiasis (confirmed clinical manifestations). The comparison of ABO phenotype distributions among all the three groups clearly indicated that disease status has a significant relationship with the blood group attributes. The result of χ² analysis of the frequencies of ABO phenotypes observed in microfilaraemic and elephantiasis groups (observed frequency vs. expected frequency computed based on the distribution of the normal population) revealed that there has been a significant alteration in the distribution of ABO phenotypes in microfilaraemic, but not in elephantiasis, group. The susceptibility to filarial infection was computed as a function of blood group phenotypes in the population. The susceptibility and conditional susceptibility for elephantiasis were the least among the subjects with AB phenotypes. The mechanism of association between filariasis and ABO antigens needs to be further explored to understand how the distribution of BGAs affects susceptibility/resistance to infection. J. Clin. Lab. Anal. 23:186–191, 2009. © 2009 Wiley‐Liss, Inc.     

Characterization of the allergen filarial tropomyosin with an invertebrate specific monoclonal antibody

Tropomyosins of invertebrates are pan-allergens responsible for wide spread allergic reactions against seafood and arthropods. As invertebrate tropomyosins are highly conserved, helminth tropomyosins are likely to show properties similar to these medically important allergens. Studies with a monoclonal antibody, NR1, raised against tropomyosin of the rodent filarial nematode Acanthocheilonema viteae revealed a B cell epitope common to helminths and marine mollusks, which does not occur in vertebrate tropomyosin. This antibody detected tropomyosin of A. viteae, other filariids, nematodes, trematodes and a cestode, and recognized as well tropomyosin of oyster, squid and octopus, but not of arthropods and vertebrates. Immunohistological analyses of A. viteae, Onchocerca volvulus and other nematodes using NR1 showed that tropomyosin is located in the fibrillar part of the body wall muscles and the uterus, and is also conspicuous in muscles of the pharynx, the vagina and other organs of the nematodes. The abundance of a pan-allergen like tropomyosin in parasitic worms and the counterintuitive, but well documented protection against allergic reactivity by some chronic helminth infections is discussed.     

Alterations in blood eosinophil morphology, binding capacity for complexed IgG and kinetics in patients with tropical (filarial) eosinophilia

As the significance of the eosinophilia which is found in some patients with chronic filarial infections is unknown, blood eosinophils were studied in seven patients with tropical (filarial) eosinophilia who had blood eosinophil counts between 5·2 and 56·6 × 10⁹/1. In six of these patients over 20% of the eosinophils were vacuolated, and degranulated eosinophils were found in the three patients with the most severe illness. In four patients serum eosinophil cationic protein levels were raised, and serial studies in two showed that they returned to normal after treatment with diethylcarbamazine. In addition, an increased proportion of eosinophils in these patients were able to bind to complexed IgG suggesting that they were responding to stimuli in the blood, and in one patient the blood eosinophil half-time clearance was prolonged. Labelled cells were cleared into the spleen, liver and bone marrow. These findings support the hypothesis that in patients with tropical (filarial) eosinophilia, blood eosinophils are induced to release their granule constituents into the circulation. It is suggested that these secretion products may interact with microfilariae, and may give rise to some of the clinical features of chronic filarial infections.     

In vitro antibody-mediated macrophage activity on Breinlia macropi microfilariae. I. Adherence and cytotoxicity

Intense adherence accompanied by cytotoxicity, which initially occurred at 4 h of interaction was observed when the microfilariae of Breinlia macropi were introduced to cultures of quokka peritoneal macrophages previously sensitized in 20% immune serum. No significant difference in the adherence or cytotoxic effects was observed among macrophages from normal, microfilaraemic and amicrofilaraemic quokkas. However, the serum component mediating these effects was found only in microfilaraemic and seropositive amicrofilaraemic quokkas. This mediator was heat-labile and its mediation of the adherence and cytotoxic effects was independent of complement. Because of its apparent dissociation from IgG and its heat lability, the possibility that the mediator resides in the previously-described reaginic antibody of the quokkas was discussed.     

Macrofilaricidal effect of 4 weeks of treatment with doxycycline on Wuchereria bancrofti

Objective To evaluate the efficacy of doxycycline as a macrofilaricidal agent against Wuchereria bancrofti. Method In the Western Region of Ghana, 18 patients infected with W. bancrofti were recruited and treated with 200 mg doxycycline per day for 4 weeks. Seven untreated patients served as controls. Four months after doxycycline treatment, all patients received 150 μg/kg ivermectin. Patients were monitored for Wolbachia and microfilaria loads, antigenaemia and filarial dance sign (FDS). Results Four months after doxycycline treatment, cases had a significantly lower Wolbachia load than controls; and 24 months after treatment, microfilaraemia, antigenaemia and frequency of FDS were significantly lower in cases than controls. Most importantly, 4 weeks of doxycycline killed 80% of macrofilariae, which is comparable with the results of a 6‐week regimen. Circulating filarial antigenaemia and FDS were strongly correlated. Conclusion A 4‐week regimen of doxycycline seems sufficient to kill adult W. bancrofti and could be advantageous for the treatment of individual patients, e.g. in outpatient clinics.     

In vitro antibody-mediated macrophage activity on Breinlia macropi microfilariae. II. Ultrastructural and video recording investigations of adherence and cytotoxicity

Video recordings and ultrastructural studies have revealed an intricate sequence of antibody-mediated cytotoxic activity by quokka peritoneal macrophages on Breinlia macropi microfilariae. The microfilaricidal activity was effected by at least two types of macrophages measuring 17 micrometers and 8 micrometers in diameter respectively. The relatively large macrophages were responsible for trapping, encircling and eventually degrading the highly motile microfilariae in a sequence of events in which the participating macrophages may interdigitate. The smaller macrophages adhered transiently to a number of adjacent sites on the surface of a trapped microfilaria, resulting in a series of damaged spots. This activity of the small macrophages was interpreted as responsible for killing the microfilaria. Thus the microfilaricidal activity was interpreted to be accomplished by the co-operative functions of the relatively large and small macrophages.     

四川省青神县基本消除丝虫病后巩固措施远期效果观察

目的 了解青神县基本消除丝虫病后实施巩固措施的远期效果,评价消除丝虫病后的流行趋势和慢性丝虫病患者的变化.方法 采用单纯反复查治残存传染源的防治措施;采取复查补查、复治补治、集体服药和以重点人群与防治薄弱村组为主要监测对象的巩固措施;开展后期慢性丝虫病调查和复查及横向人群监测.结果 青神县1983年基本消除丝虫病,1984年在疫点人群587人和横向人群1 100人监测中分别新检出微丝蚴血症者3、3例,微丝蚴密度为1～8条/120μl、2～13条/120μl;1985年横向人群监测检出复阳1例,微丝蚴密度19条/1 201.随着巩固措施实施,1986年以来已连续26年未检出微丝蚴血症者.原慢性丝虫病患者由基本消除丝虫病前的37例,减少至2010年的12例,1988年以来无新发慢性丝虫病发生.遗留的慢性丝虫病患者表现为高龄化、病程长的特点.结论 青神县消除丝虫病后监测,未发现内源性传染源,显示实施巩固措施后远期效果显著,原流行区1988年以后出生人群得到了有效保护.后期工作重点应放在对输入性传染源的监测和原慢性丝虫病患者给予关怀与照料.     

OCULAR CHANGES IN PATIENTS INFECTED WITH THE FILARIAL NEMATODE ONCHOCERCA VOLVULUS IN SOUTHWESTERN SUDAN

Ophthalmological examination of 417 patients with onchocerciasis in southwestern Sudan, a woodland savannah region, showed that ocular disease is a major health problem in these patients. Visual acuity was severely impaired in approximately 6% of patients and was reduced to finger counting in some individuals as young as 16 years. Pathological changes seen in the cornea ranged from punctate opacification to more severe sclerosing keratitis; the punctate lesions were more common in juveniles than adults. These punctate lesions were often associated with degenerating microfilariae, and a hypothetical sequence of their development is presented. Posterior segment lesions varied from mild focal retinal pigment changes, visible as dots, to widespread chorioretinal atrophy. Optic atrophy and vascular sheathing were also seen and were found exclusively in adults. These ocular changes are consistent with the findings of workers in other endemic areas who attributed them to onchocerciasis. Additional changes seen in this study included dispersal of pigment in the anterior chamber, iritis with seclusion of the pupil, and cataracts. These findings are discussed in the light of current knowledge of the pathogenesis of the disease and the need for further research into its immunopathology.