Prevalence, intensity and risk factors for soil-transmitted helminth infection in a South Indian fishing village

A study of the prevalence, intensity and risk factors for soil-transmitted helminth infection was undertaken among school children aged 5-9 years attending a primary school in the fishing village in Peda Jalaripet, Visakhapatnam, South India. One hundred and eighty nine (92.6%) of 204 children were infected with one or more soil transmitted helminth parasites. The predominant parasite was Ascaris lumbricoides (prevalence of 91%), followed by Trichuris trichiura (72%) and hookworm (54%). Study of age-specific prevalence and intensity of infection revealed that the prevalence and intensity of A. lumbricoides infection was higher among younger children than older children. While aggregation of parasite infection was observed, hookworm infection was more highly aggregated than either A. lumbricoides or T. trichiura. Multivariate analysis identified parental occupation, child's age and mother's education as the potential risk factors contributing to the high intensity of A. lumbricoides infection. Children from fishing families with low levels of education of the mother had the highest intensity of A. lumbricoides infection. As the outcome of chemotherapy programs to control soil transmitted helminth infection is dependant on the dynamics of their transmission, there is a need for further studies to better define the role of specific factors that determine their prevalence, intensity and aggregation in different epidemiological settings. (C) 2004 Elsevier B.V. All rights reserved.

Testing the energetic equivalence rule with helminth endoparasites of vertebrates

As a general test of the energetic equivalence rule, we examined macroecological relationships among abundance, density and host body mass in a comparative analysis of the assemblages of trophically transmitted endoparasitic helminths of 131 species of vertebrate hosts. Both the numbers and total volume of parasites per gram of host decreased allometrically with host body mass, with slopes roughly consistent with those expected from the allometric relationship between host basal metabolic rate and body mass. From an evolutionary perspective, large body size may therefore allow hosts to escape from the deleterious effects of parasitism.

Environmental influences on helminthiasis and nutritional status among Pacific schoolchildren

This paper describes a study undertaken to: (1) determine the prevalence of Ascaris lumbricoides, Trichuris trichiura and hookworm infections and nutritional status among Pacific Island school children; (2) identify factors influencing helminthiasis; (3) identify interventions to improve school health. A total of 3,683 children aged 5-12 years attending 27 primary schools in 13 Pacific Island countries were surveyed along with school environmental data. Stool samples were collected from 1996 children (54.2%) and analysed for ova and helminths. Total prevalence of helminthiasis was 32.8%. Anaemia prevalence was 12.4%. Children with helminthiasis and anaemia were found to be 8.7 times more likely to be stunted and 4.3 times more likely to be underweight than non-anaemic and non-infected children. Four significant environmental influences on helminthiasis were identified: (1) an inadequate water supply; (2); availability of a school canteen; (3) regular water/sanitation maintenance regimes; and (4) overcrowded classrooms. Helminthiasis was found to be strongly associated with anaemia, stunting and underweight and environmental influences identified. Although mass anti-helminthic drug administrations (MDA) have been taking place, reinfection is common as drug therapy alone is not enough. Programme effectiveness depends upon upgrading school environments to include an adequate water supply, controlled food preparation/provision, well-maintained water/sanitation facilities and class sizes of 30 students or less.

Infracommunity structure of parasites of Hemigymnus melapterus (Pisces : Labridae) from Lizard Island, Australia: The importance of habitat and parasite body size

This Study describes the community of all metazoan parasites from 14 individuals of thicklip wrasse, Hemigymnus melapterus, from Lizard Island, Australia. All fish were parasitized, and 4,649 parasite individuals were found. Twenty-six parasite species were identified although only 6 species were abundant and prevalent: gnathiid isopods, the copepod Hatschekia hemigymni, the digenean Callohelmis pichelinae, and 3 morphotypes of tetraphyllidean cestode larvae. We analyzed whether the body size and microhabitat of the parasites and size of the host affected understanding of the structure of the parasite community. We related the abundance, biovolume, and density of parasites with the host body size and analyzed the abundances and volumetric densities of some parasite species within microhabitats. Although the 2 most abundant species comprised 75% of all parasite individuals, 4 species, each in similar proportion, comprised 85% of the total biovolume. Although larger host individuals had higher richness, abundance, and biovolume of parasites than smaller individuals, overall parasite volumetric density actually decreased with the host body size. Moreover. parasites exhibited abundances and densities significantly different among microhabitats; some parasite species depended on the area available, whereas others selected a specific microhabitat. Parasite and habitat size exhibited interesting relationships that should be considered more frequently. Considerations of these parameters improve understanding of parasite community structure and how the parasites use their habitats.

Morbidity due to Schistosoma mansoni: an epidemiological assessment of distended abdomen syndrome in Ugandan school children with observations before and 1-year after anthelminthic chemotherapy

The objectives of this study were to determine the prevalence and distribution of distended abdomens among Ugandan school children across a range of eco-epidemiological settings and to investigate the relationship between distended abdomens and helminth infections, in particular Schistosoma mansoni, before and 1-year after anthelminthic treatment. A cross-sectional survey was conducted on 4354 school children across eight districts, with a longitudinal 1-year follow-up of 2644 children (60.7%). On both occasions, parasitological, biometrical and clinical data were collected for each child. Baseline prevalence of S. mansoni and hookworms was 44.3% and 51.8%, respectively. Distended abdomens, defined as an abdominal circumference ratio (ACR) >1.05, were observed in 2.5% of the sampled children, several of whom presented with particularly severe distensions necessitating hospital referral. ACR scores were highly overdispersed between districts and schools. Multivariate regression analysis revealed that S. mansoni infection accounted for only a small fraction of ACR variation, suggesting that either single point prevalence and intensity measures failed to reflect this more chronically evolved morbidity and/or that other interacting factors were involved, e.g. malnutrition and malaria. At 1-year follow-up, ACR scores showed an overall trend of regression towards the mean, potentially indicative of amelioration following chemotherapy, but geographic overdispersion still remained. © 2006 Royal Society of Tropical Medicine and Hygiene.

Species accumulation curves and their applications in parasite ecology

Species accumulation curves (SACs) chart the increase in recovery of new species as a function of some measure of sampling effort. Studies of parasite diversity can benefit from the application of SACs, both as empirical tools to guide sampling efforts and predict richness, and because their properties are informative about community patterns and the structure of parasite diversity. SACs can be used to infer interactivity in parasite infra-communities, to partition species richness into contributions from different spatial scales and different levels of the host hierarchy (individuals, populations and communities) or to identify modes of community assembly (niche versus dispersal). A historical tendency to treat individual hosts as statistically equivalent replicates (quadrats) seemingly satisfies the sample-based subgroup of SACs but care is required in this because of the inequality of hosts as sampling units. Knowledge of the true distribution of parasite richness over multiple host-derived and spatial scales is far from complete but SACs can improve the understanding of diversity patterns in parasite assemblages.