Nematode intestinal parasites of children in rural Guinea, Africa: prevalence and relationship to geophagia.

BACKGROUND: Intestinal parasitism is common among children in developing countries, but the risk factors for infection are not well characterized. METHODS: A stool examination was performed on 286 randomly selected children aged 1-18 years from three rural villages in Guinea, Africa. Information collected by questionnaire was used to examine the relationship between geophagia and infection with intestinal nematodes acquired by ingestion versus skin penetration. RESULTS: Fifty-three per cent of children were infected by at least one type of soil-transmitted nematode. Geophagia was reported by parents to occur in 57%, 53%, and 43%, of children ages 1-5, 6-10, and 11-18 years, respectively. The pattern of geophagia by age and gender of the children more closely resembled the infection pattern for the two orally acquired and soil-transmitted nematodes (Ascaris lumbricoides, Trichuris trichiura) than it did the infection pattern for the two soil-transmitted nematodes that infect by skin penetration (hookworm, Strongyloides stercoralis). CONCLUSIONS: These findings demonstrate that geophagia is an important risk factor for orally acquired nematode infections in African children. Education regarding geophagia prevention should be an integral component of any soil-transmitted parasite control programme.

PIP: Intestinal parasites are routinely found among children in developing countries, but the risk factors of such infection are poorly characterized. The stools of 286 randomly selected children aged 1-18 years from 3 rural villages in Guinea were examined. Data collected via questionnaire were then analyzed to assess the relationship between geophagia, the regular ingestion of soil, and infection with intestinal nematodes acquired through ingestion rather than through skin penetration. 53% of children were infected with at least 1 type of soil-transmitted nematode, and geophagia was reported by parents to occur in 57%, 53%, and 43% of children aged 1-5, 6-10, and 11-18 years, respectively. The pattern of geophagia by age and gender of the children more closely resembled the infection pattern for the 2 orally acquired and soil-transmitted nematodes Ascaris lumbricoides and Trichuris trichiura than it did the infection pattern for the 2 soil-transmitted nematodes which infect by penetrating the skin, hookworm and Strongyloides stercoralis. Geophagia is therefore an important risk factor for orally acquired nematode infections among African children, and education on geophagia prevention should be an integral component of all soil-transmitted parasite control programs.

The role of environmental and host behavioural factors in determining exposure to infection with Ascaris lumbricoides and Trichuris trichiura

This study examines the contribution of environmental and host behavioural factors to the rate of reinfection with geohelminths in children. Preceeding the field study, two practical procedures for estimating these factors were developed and standardised: first, a method, based on existing procedures, for extracting parasite eggs from soil samples; and second, an original method, based on the assessment of soil-derived silica from faeces, for quantifying the rate of soil ingestion (geophagia) by the study children In the field study, exposure of Ascaris lumbricoides and Trichuris trichiura was examined longitudinally at two Places-of-Safety (childrens' homes) in urban Kingston, Jamaica. At the start of the study, existing helminth infections were chemotherapeutically removed from the study populations who then naturally reacquired infection during a three month exposure period. At the end of this period the infection intensity was determined. Exposure to infection was quantified by estimating the rate of ingestion of geohelminth eggs throughout the study period. This was achieved by determining the density of eggs in the soil and the rate of soil ingestion. The eggs of both geohelminths were recovered from the soil at both localities. The mean egg densities ranged from 0.05 to 4.0 epg-soil. The eggs were overdispersed at the other. The estimated rate of egg ingestion (of each species) was overdispersed among the two populations. At the home with young children of relatively uniform age, there was a significant correlation between the rate of egg ingestion and the reacquired infection intensity: subjects who have a high rate of egg ingestion have high worm burdens. This correlation was not significant for the population of older children who were heterogeneous in age. It is suggested that the older subjects may have shown more restrained geophagic behaviour. Additionally, those who were more homogeneous in age, and perhaps susceptible to infection, tended to show a more direct relationship between the rates of egg ingestion and parasite establishment. The study demonstrated that the number of parasites established in the host was of the same order of magnitude as the number of eggs ingested from soil. This implies that for the study populations, soil ingestion is a major source of geohelminth infection (AU)

Human cases of infection with canine whipworms, Trichuris vulpis (Froelich, 1789), in Japan.

The eggs of Trichuris, detected in the feces of 19 persons who had stayed in institutions for mentally retarded and/or multi-handicapped patients, were identified as those of T. vulpis (Froelich, 1789) on the basis of morphological features. This is the first record of human infection with the canine whipworm in Japan.

Pica patterns, toxocariasis, and elevated blood lead in children.

Blood samples were obtained during a lead screening program from 100 children aged 1-6 years in Allegheny County, Pennsylvania, to determine whether there was any association between specific forms of pica and infection with Toxocara canis, the principal cause of visceral larva migrans in the United States, or elevated blood lead levels. Significant associations were found between: 1) feces, soil, or grass pica and Toxocara infection; 2) paint or plaster pica and elevated blood lead; and 3) dog ownership and Toxocara infection. These findings suggest that an accurate pica history may be useful in identifying potential health problems in children.