Hookworm burdens and faecal egg counts: an analysis of the biological basis of variation
| Autor: | G.A. Schad, Roy M. Anderson |
|---|---|
| Rok vydání: | 1985 |
| Předmět: |
Adult
Male Tetrachloroethylene Adolescent media_common.quotation_subject Helminthiasis Zoology Fertility Necator americanus Ancylostomiasis Necatoriasis Feces Sex Factors Thiabendazole parasitic diseases Per capita medicine Humans Helminths Parasite hosting Child Parasite Egg Count Aged media_common biology Ecology Public Health Environmental and Occupational Health General Medicine Middle Aged Fecundity biology.organism_classification medicine.disease Circadian Rhythm Bephenium Compounds Infectious Diseases Ancylostoma duodenale Female Parasitology |
| Zdroj: | Transactions of the Royal Society of Tropical Medicine and Hygiene. 79:812-825 |
| ISSN: | 0035-9203 |
| DOI: | 10.1016/0035-9203(85)90128-2 |
| Popis: | The relationships between various measures of faecal egg output and hookworm burdens were investigated in 84 villagers from West Bengal with mixed Necator americanus and Ancylostoma duodenale infections. The pattern of day to day variability in egg counts from individuals can be characterized by the linear relationship between the logarithms of the variances and means. Egg output is shown to be non-periodic in long runs of day-to-day records. The distribution of worm numbers per host is well described by the negative binomial probability model, and the relationship between per capita egg output and worm burden is non-linear where egg output declines as parasite burden rises. Density-dependent effects on fecundity are shown to act at comparatively low worm burdens in relation to the range of observed parasite loads. Egg output measures are shown to be qualitative as opposed to quantitative measures of worm burdens as a consequence of inherent sampling heterogeneity and variability induced by biological processes, such as density-dependent depression of parasite fecundity. The analyses suggest that it is possible, on the basis of egg counts, to discriminate between individuals with low and high hookworm burdens. The intrinsic per capita fecundities of the two species of hookworms are shown to be similar, but density-dependent constraints on egg production by N. americanus appear to be more severe than those acting on A. duodenale. This observation may help explain why A. duodenale appears to produce larger numbers of eggs per unit of time than N. americanus. The regulatory role of density-dependent fecundity and aggregated distributions of worm numbers per person are discussed in relation to the over-all transmission dynamics of hookworm parasites. |
| Databáze: | OpenAIRE |
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