The rate of ingestion of Ascaris lumbricoides and Trichuris trichiura eggs in soil and its relationship to infection in two children's homes in Jamaica

The rate of exposure to geohelminth infection of children living in 2 institutions in Jamaica, West Indies, was estimated from the product of their rates of ingestion of soil and the density of parasite eggs in the environment. The estimated mean rate of egg ingestion was 9-20 Ascaris lumbricoides eggs and 6-60 Trichuris trichiura eggs per year, although the distribution was highly overdispersed so that some individuals had an estimated annual exposure of several hundred eggs. The estimated individual rates of exposure correlated significantly with the observed worm burdens in children at one of the homes, but not at the other. It is suggested that the susceptibilty of the children and the distribution of infective stages in the enviroment may be important in determining the relationship between exposure and the rate of acquisition of infection. (AU)

Quantitative assessment of contamination of soil by the eggs of Ascaris lumbricoides and Trichuris trichiura

This study used a method of retrieving eggs from soil to examine the spatial and temporal dynamics of soil contamination with geohelminth eggs. The level of soil contamination in two children's homes in Jamaica was determined before and after further soil contamination was prevented by chemotherapy. The home which had higher human infection levels also had a higher prevalence and density of eggs in soil. The spatial distribution of the eggs in soil was overdispersed in the home with higher levels of infection, and underdispersed in the other, perhaps due to the low density of eggs. At both localities, the proportion of soil samples containing eggs, and the density of eggs in soil declined over a two-month period. The results suggest that geohelminth eggs are rapidly depleted from the surface of tropical soils in the absence of continuing sources of contamination. (AU)

The use of eggs in the assessment of selenium status of a community - abstract

Selenium (Se) deficiency appears to play a part in the development of oedematous malnutrition. It occurs in regions where soil Se availability is low. This is likely in wet, tropical limestone-based regions, such as in much of Jamaica. In high Se regions in Venezuela, Se status of the inhabitants and Se concentrations in the locally produced eggs were high. The present study explored the potential use of egg Se concentrations as a monitor for low Se areas in Jamaica. Six areas were selected, three of which were expected to be low Se areas. Homes were visited and free range hens' eggs, soil samples and hair samples were collected. Se concentrations of the sample were measured. For each area, the mean concentrations in ppm dry weight were: Glengoffe, Haynes, E. St. Thomas, Porus, Mavis Bank, Lluidas Vale; YOLK - 1.3, 2.1, 2.2, 1.8, 1.2, 1.6 respectively Total mean is 1.8; WHITE - 1.5, 3.0, 4.4, 2.4, 1.6, 2.1 Total mean is 2.7; SOIL - 0.7, 0.6, 1.1, 1.8, 0.4, 1.9 respectively Total mean is 1.2; HAIR - 0.5, 0.6, 0.6, 0.8, 0.5, 0.5 respectively Total mean is 0.6. In many of the soil samples, the values found were lower than the accepted normal range. However, in egg and hair samples, they were mostly within the normal (literature) range. There were no very low values. There was a linear correlation between egg white and egg yolk concentrations (n=101, r=0.84, p<0.001) and between egg yolk and soil concentration (n=102, r=0.20, p<0.05). Overall, however, egg Se concentration did not reflect closely either soil or hair Se concentration, and therefore is unlikely to be a useful index of Se status of a community (AU)

Quantitative assessment of geophagous behaviour as a potential source of exposure to geohelminth infection

The common form of pica, geophagy, has direct adverse nutritional effects and also exposes children to soil-borne infection. Existing methods for assessing geophagy are either inappropriate for field use (radiology) or unreliable (reporting). A new method is described, based on the measurement of soil-derived silica in stools. More than 90 percent of silica is excreted within one gut transit period of ingestion. The amount excreted is proportional to the amount ingested. Faecal level of dietary silica (<2 percent dry wt stool) can be distinguished from levels due to geophagy (up to 25 percent dry wt stool). Studies in 2 children's homes in Jamaica showed that 33 percent and 66 percent of children were geophagous, ingesting up to 10g soil day-1. The geophagy of <20 percent of the children accounted for >60 percent of the total soil ingested. This overdispersion of exposure to soil-borne infection may contribute to the observed aggregation of geohelminth infection.(AU)

Trace elements in the Jamaican diet - 1966,1970,1973

This study deals with the analysis of some Jamaican foods for essential elements and calculation of the mean intakes by the population in the years 1966, 1970 and 1973. A review of the importance of the elements iron, copper, manganese, zinc, cadmium, cobalt, calcium, magnesium, sodium, and potassium is conducted in chapter one. Special attention is paid to their function and to conditions caused by their deficiences. An outline of the purpose of the project is given in chapter two. It recognizes the scarcity of analytical data for Caribbean foods and that these could help in the establishment of Recommended Dietary Allowances and also help nutritionists to plan diets for certain conditions. Section A of chapter three, constitutes a report in investigations in methods of sample preparation. Dry ashing followed by dissolution in 3M hydrochloric acid was the method adopted for use. This method was tested with National Bureau of Standards reference material and recovery experiments. Section B is a study of a possible relationship between the concentration of elements in the food and in the soil. A study of the effect of cooking by boiling on the concentrations of the elements is also reported in this section. Green (unripe) bananas (Musa apientium) and yellow yams (Dioscorea) are the foods chosen for this study. In Section C, a comparison the elemental content obtained by analysis is made with data obtained from other sources for foods grown in other regions of the world. Two major drawbacks experienced are that none of the literature sources had data for all the elements being considered and not all the data obtained from the literature was original. The data obtained from the analyses along with literature data for foods that were not analysed are used together with data from the Food Balance Sheets to calculate mean intakes of the elements under study by the Jamaican population. This is outlined in chapter four. A computer programme, written in FORTRAN IV is used to compute average intakes per person per day for 1966, 1970, 1973. Comparison of the mean intakes with the Recommended Dietary Allowances suggested adequate intakes of zinc, magnesium and iron. The data also suggest that over the years the same food groups were major contributors of particular elements in the diet. A comparison of intakes of copper, zinc and manganese with population groups in other parts of the world was made. Data to satisfactorily assess the elemental intakes by various groups of the population was unavailable but the data contained in this work can be used as a basis for assessing trace element intake of groups in the population from future dietary surveys and to assess the effect of changing food intake patterns on the intake of the essential elements studied. Data used in the computations are given in Appendices. (AU)

A study of enteric parasites in three closed communities in Trinidad and Tobago

A study to determine the current status of enteric parasitic infections in children in three institutions of Trinidad and Tobago was initiated in 1977. The three institutions, represented distinct populations, namely the mentally retarded, the physically handicapped and the socio-economically deprived. A total of 450 children was involved in this study, which provided both qualitative and quantitative data. Faecal samples were collected from each participant, from which fifty (50) milligram portions were subjected to the formal-ether concentration technique and examined for ova, cysts and larvae, and these quantified. Cultures were also set up as a diagnostic aid and with regard to helminth larvae present in the faecal concentrates. The highest prevalence rate of intestinal parasites was found at the institution for the mentally retarded, and this was in agreement with data obtained by other workers throughout the world. The data showed that intestinal parasitism is common in this particular group, both in children and adult populations. Next in order of prevalence was the residents of the orphanage (48 percent) and then the physically handicapped group (23 percent). The intensity of infection was also highest in the mental retardates, which reflected on the ingestion of large numbers of embryonated ova and viable cysts. The drug mebendazole, a broad spectrum anthelmintic was used to treat the various helminth infections, the most prevalent being that caused by Trichuris trichiura, the intensity of those infections being monitored before and after mebendazole treatment. The pattern which emerged was that one month after drug therapy, most faecal samples were either completely negative or ova counts were extremely low. Four to six months after administration of the drug however, the ova counts had reverted to or exceeded their former levels, thus indicating that transmission had taken place. A change in the physical environment at this institution, appeared to have modified this situation by the elimination of embryonation sites, with a subsequent reduction in the intensity of infection. Unlike the mental retardates, the intensity of infection at the other two institutions was low, except for one heavy hookworm infection at the orphanage. These low intensity infections may be an indication of a low level of envionmental pollution, coupled with a higher level of personal hygeine and sanitation in these two populations. The helminths found in this study were Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis and Hookworm, the prevalence of these organisms varying from institution to institution. Amongst the protozoa the following organisms were found, Entamoeba coli, Entamoeba histolytica, Entamoeba hartmanni, Endolimaz nana and Iodamoeba buetschlii, representing the amoebae, whilst the only flagellate found was Giardia intestinalis. The intensity of these infections varied throughout the institutions, being highest at St. Ann's Hospital, where ova counts of 3 000 ova/50mgm of faecal sample were frequently encountered. With regard to the protozoal cysts these were graded on the number of cysts per high power field as being heavy, moderate, light and rare. Many heavy Giardia intestinalis, Entamoeba coli, Endolimax nana and Iodamoeba buetschlii infections were met. This study is of relevance in that it highlights areas often neglected by the medical authorities, attention being focussed in these areas only when some precipitating factor, such as the outbreak of diarrhoea occurs. Recommendations were made which at best could bring about total eradication or else reduce prevalence rates and intensity of infection to tolerable levels, that is to levels comparable to that of the community at large (AU)

Persistence of the molluscicide Bayluscide (clonitralide) emulsifiable concentrate on mud surfaces in the tropics

Clonitralide (the active ingredient of the molluscidide Bayluscide) is commonly regarded as non-persistent. It was importnt to determine if this assuption was correct during the development of a programme on St. Lucia to control the intermediate host of Schistosoma mansoni, the snail Biomphalaria glabrata. In 3 separate experiments, aqueous solutions of an emulsifiable concentrate of clonitralide were sprayed onto pans containing dried mud or mud covered with 2.5 cm of water. All snails present at the time of spraying were killed, whether or not water was present. Mortalities were high in similar, unsprayed pans but subsequent chemical and biological assays demonstrated that clonitralide remained active for over a year in tropical conditions, despite several cycles of wetting and drying. Clonitrlide residues from vegetation sprayed in an operational snail control programme remained toxic for 8 weeks exposed to full sunlight, heavy rainfall, temperatures of 20 to 30 degrees C and relative humidities of 70 percent to 95 percent. The implications of these findings for the control of aquatic and amphibious snails are discussed together with some possible mechanisms to explain the persitence of the molluscicide.(AU)