十二指肠钩虫不同蚴龄感染小白鼠的实验研究

用蚴龄20d、40d 和60d 的幼虫,分别感染了3～4个月的小白鼠,每鼠经左腹部感染幼虫300条。在感染24h,3组幼虫均移行至肺脏,但在70d 后肺部仍有幼虫;自感染9d 后蚴龄20d 先移行至小肠,于11d 后蚴龄40d 和蚴龄60d 亦达小肠;感染24h 至70d 各部位组织均可检出未发育的Ⅲ期幼虫。     

The effect of soil type and climate on hookworm (Necator americanus) distribution in KwaZulu-Natal,South Africa

We investigated environmental factors influencing the distribution of hookworm infection in KwaZulu-Natal, South Africa. Prevalence data were sourced from previous studies and additional surveys carried out to supplement the database. When geo-referenced the data revealed that higher prevalences are limited to areas below 150 m above sea level, and low prevalences to areas above this altitude. Using univariate analysis we investigated the differences in environmental factors in the two areas. The relationship between hookworm prevalence, altitude and climate-derived variables was assessed using Pearson correlation coefficient, and that of soil type using the t-test. Multivariate analysis was used to determine environmental factors that combine best to provide favourable conditions for hookworm distribution. The results revealed that areas 150 m above sea level, i.e. inland, supported low mean hookworm prevalences (x = 6, n = 21), and were characterized by soils with a clay content of more than 45%, variable temperatures and moderate rainfall. Hookworm prevalence also decreased southwards as temperatures became slightly cooler, rainfall remained more-or-less constant and the coastal plain narrowed. In the multivariate model prevalence was most significantly correlated with the mean daily minimum temperature for January followed by the mean number of rainy days for January. This indicates the importance of summer conditions in the transmission of hookworm infection in KwaZulu-Natal and suggests that transmission may be seasonal.     

Effects of multimicronutrient supplementation on helminth reinfection: a randomized,controlled trial in Kenyan schoolchildren

A randomized, placebo-controlled, double-blind, two-by-two factorial trial was carried out among 977 schoolchildren from 19 primary schools in Nyanza Province, Kenya from February 1995 to February 1996. The interventions were multimicronutrient supplementation (vitamin A, 1000 micrograms; vitamin B1, 1.4 mg; vitamin B2, 1.6 mg; vitamin B6, 1.7 mg; vitamin B12, 2.0 micrograms; folate, 150 micrograms; niacin, 16 mg; vitamin C, 50 mg; vitamin D, 5 micrograms; vitamin E, 8 mg; iron, 18 mg; zinc, 20 mg; copper, 2.0 mg; iodine, 150 micrograms; selenium, 40 micrograms) and multihelminth chemotherapy (albendazole 600 mg in a single dose and/or praziquantel 40 mg/kg in a single dose). This paper reports the effects of the supplementation given on all school days on reinfection with hookworm, Ascaris lumbricoides, Trichuris trichiura and Schistosoma mansoni after 11 months. Baseline prevalence and geometric mean intensity for hookworm, A. lumbricoides, T. trichiura and S. mansoni in all children investigated were 54.7%, 13.8%, 45.6% and 70.0%, respectively and 8.6, 2.7, 5.9 and 19.4 eggs per gram (epg), respectively. Children received a mean of 2.3 multimicronutrient/placebo tablets per school week, giving a compliance rate of 46%. Children given multimicronutrients had a slightly, but significantly, lower intensity of S. mansoni reinfection compared with children given placebo (5.5 epg vs. 7.7 epg, P = 0.047). Multiple linear regression analyses controlling for baseline infection status confirmed this, as children who received micronutrients were reinfected with S. mansoni at only 69% of the intensity of those who received placebo. Multiple logistic regression analyses revealed that micronutrient supplementation was associated with a lower S. mansoni reinfection rate (odds ratio = 0.7) although this was only of borderline significance (P = 0.090). There were no significant differences in reinfection rates or intensities of hookworm, A. lumbricoides and T. trichiura. The effect on S. mansoni infection intensity is particularly interesting given the low compliance, suggesting that full micronutrient supplementation might have a role to play in S. mansoni control programmes.     

Case of creeping disease treated with ivermectin

We report a case of creeping disease treated successfully with ivermectin. A 46-year-old man presented with a 1-month history of pruriginous linear erythema on his right thigh after a visit to Indonesia. Although he had no history of eating raw fish or meat, he walked along the river and in the jungle without wearing shoes. Creeping disease caused by animal hookworm was strongly suspected. The presence of parasite larvae was not confirmed in biopsied skin specimens. In enzyme-linked immunosorbent assay, serum samples were negative for binding to hookworm antigens, including Ancylostoma canium , Necator americanus and Gnathostoma doloresi . He was treated with a single 12 mg oral dose (200 µg/kg) of ivermectin. The eruption and pruritus resolved within a few days after the administration and did not relapse.     

肠线虫感染病原检查优化方案的研究

目的　探究肠线虫感染人群病原检查优化方案。方法　比较分析定量透明法、饱和盐水浮聚法和钩蚴试管滤纸培养法对不同感染率、感染度肠线虫卵检出效果。应用指数曲线拟合法分析定量透明法的检漏规律。结果　定量透明法检查蛔、钩、鞭虫卵存在检漏 ,且检查钩、鞭虫卵的检漏率 (EPG <2 5时 ,检漏率分别达 80 8%和 64 5 % )与感染度成反比。结论　在低感染度人群普查或防治效果考核中应选用定量透明法并用饱和盐水浮聚法     

漳州市芗城区浦南村人群钩虫病调查

目的了解芗城区浦南村钩虫人群感染及流行情况。方法采用改良加藤氏厚涂片法检查钩虫卵;对部分重度感染者进行驱虫导泻治疗,并收集虫体进行虫种鉴定;对部分环境类型土壤的钩蚴进行分离培养与鉴定。结果检查4812人,钩虫感染者1601人,感染率为33.27%。感染程度以轻度感染为主;女性感染率（18.37%）高于男性（14.90%）（χ2=7.74,P〈0.05）;人群分布以〈15岁年龄段的感染率最低（9.31%）,55～年龄段的老年人最高（47.43%）,呈年龄增长而升高趋势（χ2=300.00,P〈0.01）;文化程度以高中以上者感染率最低（8.06%）,与文盲半文盲（31.89%）、小学（37.83%）、初中（31.35%）文化程度者比较差异有统计学意义（χ2=7.74,P〈0.05）。驱虫导泻20人,收集钩虫成虫326条,均鉴定为美洲钩虫;分离培养土壤20份,分离阳性钩蚴12份,均鉴定为美洲钩蚴。结论芗城区浦南村为严重的钩虫流行区,人群钩虫感染率高,且为单纯的美洲钩虫;因此,加强健康教育,开展防治措施具有重要意义。     

Wheeze, allergic sensitization and geohelminth infection in Butajira, Ethiopia

BACKGROUND: The effect of geohelminth infection on wheeze and allergen sensitization is inconsistent across different epidemiological studies. OBJECTIVE: To investigate the association between self-reported wheeze, self-reported asthma, allergic sensitization and geohelminth infection in urban and rural areas of Butajira, southern Ethiopia. METHODS: Questionnaire data on wheeze, asthma and a range of confounding variables was gathered in a cross-sectional study of 7649 people aged 5 years or more from the Butajira Rural Health Project database. Allergic skin sensitization to Dermatophagoides pteronyssinus and cockroach was measured, and a stool sample collected for qualitative and quantitative geohelminth analysis. RESULTS: Wheeze was weakly associated with allergic sensitization to D. pteronyssinus and cockroach (odds ratios (OR) 1.21, 95% confidence interval (CI) 0.98-1.51, and 1.27, 95% CI 1.00-1.62, respectively). Self-reported asthma was related to sensitization to D. pteronyssinus only (OR 4.09, 95% CI 2.86-5.84). Geohelminths were present in 33.8% of participants, and the median egg load in infested individuals was 6 eggs/g. Overall, presence of any geohelminths was associated with a diminished risk of cockroach sensitization (adjusted OR 0.82, 95% CI 0.68-0.99) but there were no significant protective effects of any geohelminth infection against wheeze or asthma. CONCLUSION: In a developing country community with relatively low geohelminth prevalence and intensity, we found weak association between allergic sensitization and wheeze, but no evidence of a protective effect of geohelminths against wheeze or asthma.     

Expression of acquired immunity to the hookworm Ancylostoma ceylanicum in hamsters

Four experiments are described in which hamsters, initially exposed to primary infection with Ancylostoma ceylanicum , were given a homologous challenge and components of the secondary response were quantified and compared to relevant control groups. The initial establishment of the L3 larvae was not prevented in immunized hamsters but their growth was slowed and virtually all larvae were lost within a week of challenge, when the majority were still at the L4 stage of development. The loss of worms was associated with an accelerated mucosal mastocytosis and increased systemic antibody. Thus acquired immunity to hookworm larvae in this system acted on L3 and L4 stages, thereby preventing larvae from maturing in immunized animals. In contrast to primary infections, immunized hamsters responding to a challenge infection did not lose weight nor did they experience significant anaemia, because of the lack of adult worms. The secondary immune responses therefore prevented manifestation of hookworm disease among immunized-challenged animals .