José M V, Ruiz A, Bobadilla J R
Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, D.F.
Arch Med Res. 1997 Spring;28(1):121-7.
Theoretical predictions of disease prevalence due to helminth infections based upon a simple probabilistic model which considers the infection prevalence, the mean worm burden and the degree of worm aggregation are presented. A numerical reappraisal of the likely estimates of the degree of aggregation based upon maximum likelihood estimates of the negative binomial distribution is presented. The prevalence of disease shows a positive relationship with the mean worm burden. This association is hyperbolic when helminth parasites are severely aggregated but is s-shaped when helminth parasites tend to be overdispersed. The prevalence of disease decreases with the degree of worm aggregation when the values of the mean intensity are low; as the mean intensity increases this association becomes positive. The relationship between prevalence of disease and prevalence of infection is hyperbolic for severe degrees of parasite aggregation and is s-shaped for intermediate degrees of aggregation. However, if the mean intensity is low and the degree of aggregation is high there could be a negative relationship between the prevalence of disease and the prevalence of infection. The presence of disease due to helminth parasites is feasible for determined ranges of values of the infection prevalence, mean intensity and the degree of worm clumping.
本文基于一个简单的概率模型，给出了因蠕虫感染导致的疾病流行率的理论预测，该模型考虑了感染流行率、平均蠕虫负荷和蠕虫聚集程度。基于负二项分布的最大似然估计，对聚集程度的可能估计值进行了数值重新评估。疾病流行率与平均蠕虫负荷呈正相关。当蠕虫寄生虫严重聚集时，这种关联是双曲线的；而当蠕虫寄生虫趋于过度分散时，这种关联是S形的。当平均强度值较低时，疾病流行率随蠕虫聚集程度的增加而降低；随着平均强度的增加，这种关联变为正相关。对于严重程度的寄生虫聚集，疾病流行率与感染流行率之间的关系是双曲线的；对于中等程度的聚集，这种关系是S形的。然而，如果平均强度较低且聚集程度较高，疾病流行率与感染流行率之间可能存在负相关。对于感染流行率、平均强度和蠕虫聚集程度的特定取值范围，由蠕虫寄生虫导致疾病的情况是可能存在的。
