Donald A. P Bundy

Population distribution of Trichuris trichiura in a community of Jamaican children

The Trichuris trichiura worm burdens of 23 children living in a Place-of-Safety in Kingston, Jamaica, were assessed by stool collection for more than five days after treatment with mebendazole. This procedure was repeated after a seven-month period of natural re-infection. For both collections the maximum rate of worm expulsion was achieved on the fourth day after starting treatment. The worm population distributions were overdispersed and well described by the negative binomial probability model (k = 0.29) in each case. For any one individual, the number of worms passed on the first expulsion was unrelated, absolutely or relatively, to the number passed on the second. These data suggest that: knowledge of the time dependency of helminth expulsion is essential for the accurate estimation of worm burdens by this method; populations of Trichuris are more highly aggregated than those of Ascaris and may thus be more susceptible to control by selective rather than random chemotherapy; and the inherent predisposition of hosts to infection may be of minor importance in determining the distribution of worms in the population-heavily infected hosts appear no more or less likely to acquire large worm burdens on subsequent exposures.

Helminth parasites of Jamaican anoles (Reptilia: Iguanidae): a comparison of the helminth fauna of 6 Anolis species

Prevalence and intensity of helminth parasites are described for a sample of 102 Jamaican anole lizards representing 6 species ( Anolis lineatopus lineatopus, A. I. neckeri, A. grahami, A. valencienni, A.opalinus, A. sagrei, A. garmani ). Fifty nine per cent of lizards were infected with 5 species of nematodes, 16% with one acanthocephalan, 7% with two digeneans, and 4% with a single cestode species. Infection intensity was generally low (intensity range 1–5) although two species of nematode occurred in very large numbers (intensity range 1–436). Helminth prevalence patterns and species composition reflected differences in anole habitats rather than ecomorphs, and were uncorrelated with the genetic relatedness of indigenous versus introduced anole species.

Population dynamics and chemotherapeutic control of Trichuris trichiura infection of children in Jamaica and St. Lucia

Population dynamical parameters of Trichuris trichiura infections in children were estimated from longitudinal intensity and prevalence data from a population (n = 23) in a childrens home in Jamaica. The theoretical predictions of a deterministic model incorporating these parameters were approximated to observed horizontal-age prevalence data from a naturally infected population (n = 203) of children in a St. Lucian village, and a rough estimate of the basic reproductive rate (Ro = 8-10) of T. trichiura obtained. The findings suggest that T. trichiura populations are intrinsically more difficult to control by traditional mass-treatment chemotherapy (eradication requires greater than 91% of the population to be treated every 6 months for greater than 5 years) than are populations of Ascaris, but may be more susceptible to selective chemotherapy programmes which aim to treat only the most heavily infected individuals.

Rate of expulsion of Trichuris trichiura with multiple and single dose regimens of albendazole

The efficacy of multiple and single dose regimens of albendazole on Trichuris trichiura infection was evaluated by counting the number of worms expelled/day from two pair-matched groups of children, for nine days following therapy. The temporal patterns of worm expulsion were similar whether the children received a single 400 mg dose or two consecutive doses: no worms were passed before the second day, or after the sixth day, after intervention, and the maximum worm expulsion rate was attained on the fourth day. A second treatment six days after the first expelled no more worms. The results obtained here resemble those obtained previously with a three-day (600 mg) regimen of mebendazole in a study of heavily infected children. We conclude: that irrespective of dose, benzimidazole carbamates require the gut transit time plus 48 hours to immobilize T. trichiura; and that a single dose of albendazole is effective against light infections of T. trichiura but requires further evaluation with high intensity infections.

Sodium azide preservation of faecal specimens for Kato analysis

The modified Kato technique has the advantages of reproducibility, simplicity and economy: the disadvantage is that it cannot be used in conjunction with traditional faecal preservatives. Sodium azide has been evaluated as a preservative for human faeces for subsequent Kato analysis. More than 400 faecal samples (from normal and malnourished children, and from mixed-age participants in a field survey of the Turks and Caicos Islands) were each mixed with 2-5 mg of sodium azide powder and stored in 2 or 4 ml autoanalyser cups at ambient tropical temperature. At intervals up to 30 weeks, aliquots were prepared for Kato analysis. Trichuris trichiura, Ascaris lumbricoides and Necator americanus eggs were well preserved without degenerative or developmental changes in morphology. Quantitative analyses of 18 samples indicated that the mean egg count/sample did not change significantly after storage for 1, 2, 4, 8, 12 and 16 weeks in preservative. The use of azide preservative extends the applications of the Kato technique to field and clinical studies in which delays may occur between specimen collection and examination. The direct costs of azide preservation are substantially lower than for traditional methods and the preserved specimens are more compact and resistant to leakage.

Differences in composition between Fasciola hepatica spines and cestode hooks

Abstract 1. 1. The tegumental spines of Fasciola hepatica have been isolated. 2. 2. Acid hydrolysates of total spines revealed a lack of detectable cystine and 3-methylhistidine. 3. 3. SDS completely solubilized the spines, the subsequent gel-electrophoresis resolved several minor polypeptide components and a major one of approx. 50,000 mol. wt. 4. 4. These results suggest an infrastructural difference between digenean spines and their counterparts in the con-phyletic cestodes. 5. 5. The results do not support the view that digenean spines are largely composed of actin.