Ed Cooper

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.

Parasitic Helminth Infection and Cognitive Function in School Children

The study examines the effect of moderate to high worm burdens of Trichuris trichiura infection on the cognitive functions of 159 school children (age 9–12 years) in Jamaica, using a double-blind placebo-controlled protocol. Results were evaluated by using a forward-stepwise multiple linear regression. Removal of worms led to a significant improvement in tests of auditory short-term memory (p < 0.017; p < 0.013), and scanning and retrieval of long-term memory (p < 0.001). Nine weeks after treatment, there were no longer significant differences between the treated children and an uninfected Control group in these three tests of cognitive function. It is concluded that whipworm infection has an adverse effect on certain cognitive functions which is reversible by therapy.

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.

Immediate hypersensitivity in colon of children with chronic Trichuris trichiura dysentery

There are few data on mucosal immune responses to intestinal helminths in human beings, especially those involving the IgE system, which is thought to be important in parasite expulsion. We sought evidence of an immediate hypersensitivity reaction in the colon of children with chronic dysentery due to Trichuris trichiura. 28 children with Trichuris dysentery syndrome (TDS) were compared with 16 control children (with no TDS or worms visible on colonoscopy). All children were aged 1-11 years. Rectal biopsy samples were taken before and after expulsion of the worms by means of mebendazole treatment. Children with TDS had significantly greater numbers than controls of mast cells (mean [SD] 10.9 [1.3] vs 3.9 [0.6]% of all cells; p less than 0.0003) and of cells with surface IgE (median [range] 11.1 [7.5-11.6] vs 1.0 [0-1.5]%; p less than 0.001) in the subepithelial region of the mucosa. On electronmicroscopy, degranulating mast cells were prominent in parasitised children. In culture, rectal biopsy samples from parasitised children showed high rates of spontaneous histamine release, but only low rates of antigen-specific release. After treatment, spontaneous histamine release was significantly reduced and antigen-specific histamine release could be provoked. Thus, an IgE-mediated immune mucosal response to a helminth infection does occur in human beings but is not sufficient to cause appreciable parasite expulsion.

Humoral immune responses in human infection with the whipworm Trichuris trichiura

Summary The humoral immune response to infection with Trichuris trichiura was investigated by ELISA and immunoblotting using human sera from the Caribbean island of St Lucia. Immunoblot analysis of the degree of cross‐reactivity with the related trichuroid Trichinella spiralis and with the other commonly co‐existent nematodes. Ascaris lumbricoides and Toxocara canis, was carried out using selected sera. The IgM, IgA, IgE, and IgG subclass antibody levels were measured in ELISA using a detergent solubilized extract of adult T. trichiura. The IgG and IgE responses were highly Trichuris specific. Anti‐T. trichiura IgM responses were totally cross‐reactive with A. lumbricoides and were completely ablated by pre‐incubation of sera with Ascaris antigen. The IgG response was predominantly of the IgG1 subclass with a minimal IgG3 response. Only 1 person out of 130 tested had a delectable IgG3 response. The IgG2 response appeared to be directed primarily against carbohydrate or polysaccharide antigens as pre‐treatment of the ELISA plates with poly‐L‐lysine was necessary before a response could be detected. These data are the first demonstration of human isotypic responses to infection with T. trichiura.

Tuberculin testing before BCG vaccination

May not be necessary BCG vaccination is effective against forms of tuberculosis that occur commonly in childhood that have a high morbidity and mortality, such as tuberculous meningitis.1 2 Current guidelines for the United Kingdom recommend tuberculin skin testing before BCG vaccination for all children older than 3 months.3 The evidence base for this recommendation is unclear—no randomised controlled trials have been conducted to compare outcome of BCG vaccination with and without prior tuberculin skin testing, and the resulting two or three stage procedure seriously compromises uptake. The BCG vaccine was not available in the United Kingdom from 9 August 2002—when all stocks from the monopoly supplier, Evans Vaccines, were declared potentially ineffective by the Medicines Control Agency and the Department of Health—until supplies from Denmarks State Serum Institute became accessible during December 2002. The currently available BCG vaccine is for intradermal use only. From November 1998 to July 2001 a similar loss of supply of percutaneous BCG vaccine, which is …

Marriage, like income and education, fails to provide shelter for women against HIV infection in sub-Saharan Africa: widowhood and divorce increase the risk

Since HIV infection and its consequence, AIDS, were first described, many initial assumptions have proven to be wrong. In Africa, it is women who bear the greater burden of the disease. In many ways they are less visible than men, although at least as much at risk, often even more so. Marriage is no protection against infection, and widowhood and divorce leave them still more vulnerable. This is reflected in higher proportions of infection for bereaved and separated wives. Programmes of control, which depend on education, testing and access to treatment should be visible and accessible to all women in sub-Saharan Africa.