The age of infection with varicella-zoster virus in St. Lucia, West Indies

Sera from an age-stratified sample of 1810 people from the Caribbean island of St. Lucia were tested for antibodies against varicella-zoster virus. The results indicate that very few infections occur in childhood which agrees with clinical survey data from other tropical countries, but contrasts with the observed high case rate in children in temperate countries. The alternative hypothesis which may explain these results are discussed, and it is suggested that high ambient tempertaures interfere with the transmission of the virus. Irrespective of the cause the pattern of varicella incidence observed has important implications for any vaccination policy adopted in tropical countries (AU)

Age-dependency of infection status and serum antibody levels in human whipworm (Trichuris trichiura) infection

This study examines the age-dependency of the relationships between human infection with whipworm (Trichuris trichiura) and parasite-specific antibody level measured by ELISA against an extract of adult worms after preincubation of the sera with Ascaris lumbricoides adult worm extract. The convex age-profile of parasite infection intensity is shown to be mirrored by age-dependent change in age-class mean levels of IgG (all subclasses except IgG3), IgA, IgM and IgE. Mean antibody levels rise with increasing acquisition of infection in childhood. Immunoblot analysis of selected sera from different age-classes indicates that antigen recognition is similarly dependent on infection intensity. In individual children, antibody levels correlate positively with acquisition of infection, consistent with a simple model of antigen dosage specifying the magnitude of the humoral immune response. In adults, IgG4 correlates positively and IgA negatively with intensity of infection, suggesting involvement of these isotypes in functional roles of immune blockade or effector mechanisms, respectively.(AU)

Infective arthritis due to Blastocystis hominis

A patient with rheumatoid arthritis taking prednisone developed Blastocystis hominis acute diarrhoea, which was associated with increased inflammation and effusion of the left knee. B. hominis organisms were found in synovial fluid from the left knee. The patient responded dramatically to metronidazole treatment. B. hominis may become disseminated in immunosuppressed patients with diarrhoea and may cause infective arthritis. (AU)

Aortic dissection: an autopsy experience

Aortic dissection was confirmed in 33 patients at autopsy at the University Hospital of the West Indies between 1975 and 1988. Twenty-five cases were acute and 8 chronic and the diagnosis was made antemortem in 5 cases overall. The high risk of rupture of proximal dissections involving the ascending aorta into the pericardial sac is clear, and the overriding importance of systemic hypertension is once again confirmed. An unusual finding was the higher proportion of females to males. A higher index of suspicion should permit and antemortem diagnosis and apropriate therapy in a larger proportion of patients (AU)

Seroepidemiological study of the transmission of mumps virus in St. Lucia, West Indies

A seroepidemiological study of the prevalence of mumps virus specific antibodies reveals a pattern of endemic persistence on the island of St. Lucia in the West Indies. In the unvaccinated population the proportion seropositive rose rapidly in the child age classes to attain a stable plateau close to unity in value in the teenage and adult age groups. The average age at infection was estimated to be between 3 and 4 years of age and the average duration of detactable levels of maternally derived antibodies was approximately 3 months. Analyses based on mathematical models of the transmission dynamics of the virus suggest that in excess of 75 percent of each cohort of 1-to 2-year-old children must be effectively immunized to eliminate mumps virus transmission. A mumps radial haemolysis test, developed for quantitive measurements of antibody, is discussed. (AU)

Disseminated infection caused by penicillin-resistant gonococci in two Jamaicans

Disseminated gonococcal infection due to penicillin-resistant organisms is very unusual. Two such cases occuring at the University Hospital of the West Indies are described. Implications for therapy are discussed (AU)

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 intiation 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. (Summary)

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 percent were harboured by the 2 to 15-year-old children. Of those individuals harbouring 100 worms or more, 87 percent 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.(AU)

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 (R. = 1-1.8) was similar to that recorded elsewhere and much lower than that of T. trichiura (R. = 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. Futher studies are required to determine the cause of these observations.(AU)