Evaluating measures to control intestinal parasitic infections.

摘要: Intestinal parasitic infections are among the most common of humans in developing countries, but resources available for their control severely limited. Careful evaluation measures is essential to ensure that they cost-effective. The effects on intestinal helminths and protozoa requires an understanding different epidemiological patterns these two groups parasites. transmission dynamics morbidity associated with major helminth (Ascaris lumbricoides, Trichuris trichiura hookworms) dependent size worm burdens. Thus important parameter evaluating impact intensity infection, which can be assessed by determining mean density parasite eggs faecal specimens. Estimation subject systematic errors, however, due complex pattern burden distributions. frequency distribution burdens highly overdispersed, individuals exhibit predisposition particular levels infection. Furthermore, age-dependent, a species-specific manner, clustered spatially within families. These imply estimation exceptionally sensitive demographic structure population sample selected assessment. They also have effect prevalence estimates, commonly used infection communities, seriously mislead. Paradoxically, least useful where because relationship between markedly non-linear when high. areas needed, using might suggest had failed while would, correctly, show measure success. With protozoan (Entamoeba histolytica, Giardia duodenalis Cryptosporidium parvum) estimate little value central prevalence. Prevalence does age spatial heterogeneity, may species-specific, so there remains need consistent structure, although this less critical than helminths. constraint identify pathogenic species and, some cases, strains. Harmless commensal protozoans ubiquitous often morphologically very similar pathogens, both unnecessary impracticable. Species such E. histolytica appear exist as strains differing pathogenicity, thus will cost-effective only if focus Effective diagnosis therefore infections.(ABSTRACT TRUNCATED AT 400 WORDS)