Growth and development four years after treatment for the Trichuris dysentery syndrome.

A follow-up study is reported of 18 children 4 y after treatment for the Trichuris dysentery syndrome (TDS) and matched control children. The TDS children were initially severely stunted and had extremely low developmental levels. They showed catch-up in height of 1.9 z-scores even though they remained in very poor environments. Their intelligence quotients, school achievement and cognitive function remained significantly lower than those of the controls. Controlling for their earlier developmental levels, the TDS children showed a small improvement in mental development relative to the controls.

Trends in admission and case fatality for acute malnutrition (Kingston 1982-1991).

The case fatality ratio (CFR) in acute protein-energy malnutrition (PEM) achieved in the Tropical Metabolism Research Unit (TMRU) was compared with that of other tertiary care facilities in Kingston. Trends in admission and fatality rates, case severity and complications were also examined. From ward admission registers for Bustamante Hospital for Children (BHC), the University Hospital of the West Indies (UHWI), children's wards and the TMRU all cases of PEM admitted from 1982 through 1991 were enumerated and there was a docket search for random subsamples. Ten-year mean CFR% for BHC was 8.8 (n = 1948); for UHWI wards 5.5 (n = 658); for TMRU 7.1 (n = 662). BHC has the least restrictions on admission and showed most clearly that the peak time in Kingston for admission of PEM was around 1985, falling to a minimum in 1988-1990 and rising again in 1991; however, the other sites also showed similar trends. BHC had a range of CFR% p.a. of 20.0 to 3.0, with a striking fall in the second half of the decade. There was no temporal CFR trend for the UHWI or TMRU. The latter institution had the highest proportion of admissions with marasmic-kwashiorkor and the lowest proportion with recorded infection. The annual variation in numbers of PEM deaths at BHC was best accounted for by (a) percentage change in consumer price index and (b) percentage change in the US$ value of the Jamaican $, in the preceding year, and (c) annual number of admissions, together. Generally, our findings suggest a minor role for expert in-patient management in reducing deaths from PEM.

Treatment effects in Trichuris dysentery syndrome.

Heavy infection with the geohelminth Trichuris trichiura causes the Trichuris dysentery syndrome (TDS). Growth retardation and anaemia are characteristic of TDS and both are associated with poor development. We have examined the growth and developmental responses to treatment in 19 children aged 27-84 months with TDS. Developmental levels (DQ) were measured with the Griffiths mental development scales. Compared with a control group matched for age, gender and neighbourhood, the TDS children initially had serious deficits in DQ (24 points, p < 0.001). After a year of anthelmintic treatment, the TDS children showed improvement in locomotor development (p < 0.001) compared with the controls. The TDS children also had initial deficits in height-for-age, weight-for-height, mid-upper arm circumference and haemoglobin levels. They caught up rapidly in indices of wasting (weight-for-height and mid-upper arm circumference) and showed steady improvement in height-for-age and haemoglobin levels. Catch-up in height was comparable to that of children recovering from coeliac disease. The importance of continuing prevention after initial treatment is highlighted.

Immunoepidemiologic studies of Strongyloides stercoralis and human T lymphotropic virus type I infections in Jamaica.

Epidemiologic investigations of Strongyloides stercoralis and human T lymphotropic virus type I (HTLV-I) infections were conducted. Of 312 persons contacted, 209 (67%) provided blood and stool samples. Prevalences of S. stercoralis and HTLV-I antibodies were 26.8% and 8.1% (n = 198), respectively, and S. stercoralis larvae were detected in 4%. HTLV-I antibodies were significantly more common in persons positive for S. stercoralis larvae (10 [58.8%] of 17) compared with seropositive larva-negative (4 [8.9%] of 45) or seronegative persons (9 [6.2%] of 145) (P < .002). IgE levels increased with age in S. stercoralis-seropositive persons who were HTLV-I negative (P < .002). However, there was an age-related depression of serum IgE in HTLV-I-positive positive persons (P < .003) that was sufficient to annul the IgE level-raising effect of S. stercoralis seropositivity. The data provide evidence that HTLV-I infection is associated with increased frequency of larvae in the stool of S. stercoralis-infected persons and suggest that the mechanism may involve suppression of the IgE response.

Neural tube defects in Jamaica following Hurricane Gilbert.

An increased incidence of obvious live-birth neural tube defects (i.e., spina bifida cystica and encephalocele) occurred in Jamaica 11 to 18 months after Hurricane Gilbert. The conceptions of the affected babies coincided with a rise in megaloblastic change in sickle cell patients, suggesting a wide-spread drop in dietary folate intake. A detailed history was taken from each of the 17 affected mothers (case subjects) and 51 unaffected mothers (matched control subjects). The case subjects reported a significantly lower mean intake of dietary folate in the periconceptional period (154 micrograms/day) than did the control subjects (254 micrograms/day). The temporary increase in neural tube defects was associated with a diet comparatively low in folate in the periconceptional period, suggesting the dietary level of folate that fails to protect against neural tube defects under natural conditions.

Moderate to heavy infections of Trichuris trichiura affect cognitive function in Jamaican school children.

A double-blind placebo trial was conducted to determine the effect of moderate to high loads of Trichuris trichiura (whipworm) infection on the cognitive functions of 159 school children (age 9-12 years) in Jamaica. Infected children were randomly assigned to Treatment or Placebo groups. A third group of randomly selected uninfected children were assigned to a Control for comparative purposes. The improvement in cognitive function was evaluated using a stepwise multiple linear regression, designed to control for any confounding variables. The expulsion of worms led to a significant improvement in tests of auditory short-term memory (P less than 0.02; P less than 0.01), and a highly significant improvement in the scanning and retrieval of long-term memory (P less than 0.001). After 9 weeks, treated children were no longer significantly different from an uninfected Control group in these three tests of cognitive function. The removal of T. trichiura was more important than Ascaris lumbricoides in determining this improvement. The results suggest that whipworm infection has an adverse effect on certain cognitive functions which is reversible by therapy.

Intestinal nematode infections in children: the pathophysiological price paid.

The mechanism by which small animals such as rodents resist or eliminate nematode parasites requires mucosal inflammation as the final effector of the immune response. The resulting freedom from chronic infection may be worth the price of short-term illness. Putative vaccines which attempt to enhance the natural effect will have to take into account the inflammatory cost to the host. Human helminthiases involve a more stable equilibrium between host and parasite. The medical literature on hookworm disease and clinical ascariasis describes, for the former, some chronic inflammatory effects correlated with worm burden, but for the latter a less quantified or predictable set of detrimental effects. We describe a current, systematic study of the inflammatory response to whipworm infection, in which anaemia, growth retardation and intestinal leakiness are viewed as predictable consequences related to infection intensity. There is evidence for the absence of cell-mediated immunopathology. However, a specific, IgE-mediated local anaphylaxis may, at least partly, mediate the deleterious effects. Increased numbers of mucosal macrophages may also contribute to the chronic, systemic effects through their output of cytokines. Similar attempts to show the mechanisms of pathogenesis and quantify the effects of hookworm disease should be undertaken.

Growth suppression in the Trichuris dysentery syndrome.

The Trichuris Dysentery Syndrome (Ramsey, 1962) is an insidious, chronic condition which has clinical features similar to Crohn's ileocolitis and ulcerative colitis, diseases similarly associated with growth retardation. The attained heights and weights of 19 children at the time of diagnosis of intens, -2.4 Standard Deviation (Z) scores from the Tanner-Whitehouse median with weight, adjusted for height-age, -1.3 Z. We present data on the growth velocities of 11 of the children in the half-year following worm expulsion by mebendazole. These children returned to their home environments without food supplementation or close follow-up, but showed an average height velocity of +5.5 Z and weight velocity (for height-age) of +2.4 Z. Of 8 children with unequivocal height spurts only 3 had any weight spurt. We suggest that the pattern of catch-up growth points to the existence of some specific link between allergy or inflammation in the lower intestinal tract and suppression of linear growth, rather than to stunting due to general deprivation and undernutrition.

The evidence for predisposition to trichuriasis in humans: comparison of institutional and community studies.

This article compares the results of two studies of Trichuris trichiura infection, one conducted in a children's home and the other in a village. In both, the intensity of infection of a cohort of children was determined by antihelminthic expulsion initially, and again after a period of re-infection. The cohort of village children showed a predisposition to a particular intensity of infection. An individual with a heavy infection initially was likely to re-acquire a heavier than average worm burden. No such correlation was observed for the cohort of institutionalized children. It is suggested that the causation of predisposition is multifactorial, and that the contrasting results of the two studies may be due in part to differing levels of heterogeneity in exposure to infection, the village children being exposed to dissimilar domestic environments and the institutionalized children to only one.

Age-relationships of Toxocara canis seropositivity and geohelminth infection prevalence in two communities in St. Lucia, West Indies.

Sera were examined from an age-stratified sample of two Caribbean communities using the Toxocara-ELISA with larval ES antigen. Seropositivity was markedly age dependent, attaining maximal values (40 and 60%) in 5-15 year olds and declining in adults. The rate of acquisition of infection with Toxocara canis and the age-prevalence profile are similar to those of Ascaris lumbricoides and Trichuris trichiura. It is suggested that toxocariasis is likely to be prevalent in tropical areas with endemic geohelminthiasis.

Predisposition to Trichuris trichiura infection in humans.

The study examines the distribution of Trichuris trichiura infection in a village community in St Lucia, West Indies. The infection intensity of the same age-stratified population was assessed (by drug expelled worm burden and faecal egg count) at the initiation of the study, and after 17 months of reinfection following treatment. The frequency distribution of worm numbers per person was similar at both periods of sampling. There was a significant correlation between the initial infection intensity of an individual, and the intensity acquired by the same individual following the 17 month period of reinfection. This relationship was observed in a broad range of host age classes. The study provides firm evidence that individuals are predisposed to heavy (or light) T. trichiura infection.

Epidemiology and population dynamics of Ascaris lumbricoides and Trichuris trichiura infection in the same community.

The gastrointestinal helminth infection status of an age-stratified sample from a single Caribbean community was assessed using anthelmintic expulsion techniques. The same sample was re-assessed in a similar manner after a 17 month period of re-infection. The age-prevalence profile of Ascaris lumbricoides was convex while that of Trichuris trichiura was asymptotic. The age-intensity profiles of both species were convex. These differing patterns are attributed to differences in the absolute worm burdens of the 2 species. The frequency distributions of infection intensity were similar for both species, and largely independent of host age. The basic reproductive rate of A. lumbricoides (Ro = 1-1.8) was similar to that recorded elsewhere and much lower than that of T. trichiura (Ro = 4-6), implying that the latter is intrinsically more resistant to control. Individual hosts were predisposed to high (or low) intensity infection with either species, although predisposition to both species simultaneously was not conclusively demonstrated. Further studies are required to determine the cause of these observations.

Age-related prevalence and intensity of Trichuris trichiura infection in a St. Lucian community.

Age-related changes in the average worm burden and the prevalence of Trichuris trichiura infection, in a village community in St. Lucia, were examined by field studies based on worm expulsion techniques. Horizontal age-intensity profiles were convex in form with peak parasite loads occurring in the 2 to 15-year-old children. Prevalence is shown to be a poor indicator of changes in average worm load with age. Faecal egg counts (epg and epd) provide a qualitative measure of worm burdens since fecundity is shown to be approximately independent of worm load. The parasites were highly aggregated within the study community, with most people harbouring low burdens while a few individuals harboured very heavy burdens. Of the total parasite populations in the study sample, 84% were harboured by the 2 to 15-year-old children. Of those individuals harbouring 100 worms or more, 87% were in the 2 to 10-year-old age range. Crude estimates of population parameters (basic reproductive rate, 4-5; rate of reinfection, 90 year-1) suggest that the rate of reinfection is higher than for other helminth parasites of man. The control of morbidity and parasite transmission is discussed in the context of targeting drug treatment at the child segment of the study population.

Epidemiological characteristics of Toxocara canis zoonotic infection of children in a Caribbean community.

The study reports the results of a summary of the prevalence and symptomatology of paediatric toxocariasis in Anse-la-Raye, St. Lucia. The seroprevalence of Toxocara canis among the children, as determined by ELISA, was 86%, the highest level recorded to date. In contrast, the prevalence of infection in dogs was not abnormally high, although the canine population was large and unconstrained compared to that in industrial countries. The presence of infective ova in peridomestic areas and the widespread practice of pica among children in the village probably combine to enhance exposure to infection.

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 children's 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.

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.