药物控制六年后人宿主中盘尾丝虫微丝蚴的种群动态

Population dynamics of onchocerca volvulus microfilariae in human host after six years of drug control.

作者信息

Opara K N, Fagbemi B O

机构信息

Department of Zoology, University of Uyo, Uyo, Akwa Ibom State, Nigeria.

出版信息

J Vector Borne Dis. 2008 Mar;45(1):29-37.

PMID:18399314

Abstract

BACKGROUND & OBJECTIVES: Mass administration of ivermectin drug was carried out annually between 1995 and 2001 in three villages that were endemic for onchocerciasis in the Lower Cross River Basin, Nigeria. The aim of this study was to evaluate the population dynamics (dispersion patterns, distribution, prevalence and intensity) of Onchocerca volvulus microfilariae in their human host after six years of ivermectin treatment.

METHODS

A total of 1014 subjects from three rural areas in Etung Local Government Area of Cross River State, Nigeria were screened for skin microfilariae using standard parasitological method of diagnosis.

RESULTS

Ivermectin drug intervention had significantly reduced the prevalence of skin microfilariae (PMF) from 69.3% pre-control to 39.3% and community microfilarial load (CMFL) from 7.11 to 2.31 microfilariae per skin snip. Males (45%) were significantly (p <0.05) more infected than females (34%). Both microfilarial prevalence and intensity increased with age. Pearson correlation test between intensity and age was not significant (r = 0.37; p >0.05). The correlation between age-dependent parasite prevalence and mean abundance was also not significant (r = 0.42; p >0.05). The degree of dispersion as measured by variance to mean ratio (VMR), coefficient of variation (CV) and exponent 'K' of the negative binomial model of distribution showed that the parasite aggregated, clumped and overdispersed in their human host. The relative index of potential infection of each age group showed that adults between the age of 21 and 50 yr accounted for 52.7% of microfilariae positive cases.

INTERPRETATION & CONCLUSION: Aggregated and overdispersion of O. volvulus observed in this study showed that active transmission could still be going on, because the tendency of the vector, Simulium damnosum ingesting more microfilariae was high due to the aggregated and overdispersed nature of the parasite with its host.

摘要

背景与目的

1995年至2001年期间，每年都在尼日利亚下克罗斯河流域3个盘尾丝虫病流行村庄大规模施用伊维菌素。本研究旨在评估伊维菌素治疗6年后，人体宿主中盘尾丝虫微丝蚴的种群动态（分布模式、分布、患病率和感染强度）。

方法

采用标准寄生虫学诊断方法，对尼日利亚克罗斯河州埃通地方政府辖区3个农村地区的1014名受试者进行皮肤微丝蚴筛查。

结果

伊维菌素药物干预使皮肤微丝蚴患病率（PMF）从干预前的69.3%显著降至39.3%，社区微丝蚴负荷（CMFL）从每皮肤切片7.11条微丝蚴降至2.31条。男性感染率（45%）显著高于女性（34%）（p<0.05）。微丝蚴患病率和感染强度均随年龄增长而增加。感染强度与年龄之间的Pearson相关性检验不显著（r = 0.37；p>0.05）。年龄依赖性寄生虫患病率与平均丰度之间的相关性也不显著（r = 0.42；p>0.05）。通过方差与均值比（VMR）、变异系数（CV）以及负二项分布模型的指数“K”衡量的离散程度表明，寄生虫在人体宿主中呈聚集、结块和过度分散状态。各年龄组潜在感染的相对指数显示，21至50岁的成年人占微丝蚴阳性病例的52.7%。