Ascariasis in Nigeria

Socio-environmental factors and ascariasis infection among school-aged children in Ilobu, Osun State, Nigeria

The risk factors predisposing children to ascariasis transmission in a rural community of Osun State, Nigeria were investigated from November 2005 to April 2006. Children below 16 years of age were examined at the household level after information on biodata, access to water supply and sanitation, socio-economic status of their parents and degree of cohabitation with their parents was collected using a questionnaire. Of 440 children examined, overall prevalence was 60% and median intensity was 1548 eggs per gram (epg) (min. 48 epg; max. 55464 epg). Infection patterns were gender comparable and age dependent, with peak prevalence (67.8%) occurring in children aged 5-9 years and peak median intensity (4368 epg) in children aged >or=15 years. Logistic regression analysis revealed that prevalence was influenced by patterns of water supply and sanitation, parents' educational background, number of biological parents living with a child and number of playmates a child has. These findings suggest that socio-environmental risk factors which play a role in disease transmission need to be taken into account when formulating sustainable control strategies for ascariasis and other intestinal parasites in Nigeria and elsewhere.

A school-based schistosomiasis and intestinal helminthiasis control programme in Nigeria: acceptability to community members

In a population with high prevalences in schoolchildren of infection with hookworm (32.4%), Ascaris (22.9%) and Trichuris (2.5%), visible haematuria (17.9%), micro-haematuria (17%) and proteinuria (47.3%), the knowledge about transmission of schistosomiasis and acceptability of a school-based control programme were assessed. The community perceived schistosomiasis (80.6%) and intestinal helminthiasis (66.5%) as important health problems in school-age children and most people would prefer placement of the control programme in school because it would eliminate transportation cost to the health facility. They welcomed the idea of using teachers for detection of infection and drug administration. The health staff, on the other hand, were willing to work with teachers, but emphasized that teachers should be limited to organizational and supervisory roles while they do tests and administer the drug. This view was also shared by the officials in the state ministries of health and education.

Analysis of the prevalence of infection and associations between human gastrointestinal nematodes among different age classes living in the urban and suburban communities of Port Harcourt, Nigeria

Fresh stool samples from 300 subjects presenting at out-patient clinics in two major hospitals in Port Harcourt were analysed for the prevalence and intensity of gastrointestinal (GI) nematode infections and 85.3% were found to carry at least one of the four species of GI nematodes recognized during the study. The most common species was Ascaris lumbricoides (54%), followed by Trichuris trichiura (43.7%) and Necator americanus (42.7%) and lastly Strongyloides stercoralis (33%). Peak prevalence for A. lumbricoides was among the < or = 9 years age cohorts, whilst those for the remaining species all coincided among the 15-19 years age cohort. The frequencies of single, double and triple-species infection categories, across the species and within most of the specific combinations were lower than the expected frequencies calculated from overall prevalence data for each species. Observed cases of non-infected individuals and those carrying all four species were higher than expected, suggesting that a greater than expected subset of the population was free from infection, particularly among subjects > or = 30 years old and another subset more prone to infection by all four species, predominantly among the age cohorts < or = 29 years. N. americanus and T. trichiura were more commonly encountered among multiple species infection combinations than expected, but the intensity of the former declined as the number of other concurrently infecting species increased. In contrast, the intensity of infection with S. stercoralis increased as the number of other species increased. Positive associations between A. lumbricoides and T. trichiura, N. americanus and S. stercoralis, and T. trichiura and N. americanus were identified in respect of greater than expected co-occurrence of these combinations and significant positive correlations between their respective intensities of infection. These were related to specific age cohorts which were identified as particularly prone to multiple infections.

Relationship between the degree of poverty and the IgE response to Ascaris infection in slum children

We examined a group of urban slum children in Caracas, Venezuela, and demonstrated the relationship that exists between poverty, conditions of hygiene and the prevalence of helminth infection. Concordant with the high prevalence of helminth infection in these children, the total serum levels of immunoglobulin E (IgE) and blood eosinophilia were elevated and were directly related to the degree of poverty and lack of sanitary facilities. However, in contrast, the reverse pattern was observed for the specific allergic response to these parasites. Thus, the immediate hypersensitivity skin test reactivity to Ascaris antigens, and the serum levels of specific anti-Ascaris IgE antibody, were lowest in the poorest children, who had the highest prevalence of helminth infection and the highest total IgE levels. As allergic-type reactions may participate in protective mechanisms against helminths, these results suggest that poverty and poor sanitary conditions may, by influencing the IgE response, compromise the resistance of such children to parasitic infections.

The prevalence and intensity of soil-transmitted helminthiases in rural communities in southern Nigeria

An investigation of the prevalence and intensity of soil-transmitted helminthiases was undertaken in four villages in Oyo state, Nigeria. Diagnosis was based on examination of stool samples for the presence of helminth ova in all age classes. The prevalence of Ascaris lumbriocoides ranged from 61.5-72.2%, of Trichuris trichiura from 65-74%, and of hookworm from 52.4-63% depending on the village concerned. Intensity, assessed indirectly as the mean eggs per gram of faeces (epg), varied with regard to the four villages. The mean egg count of A. lumbricoides varied from 6815-10,823 per gram, of T. trichiura from 127-246, and of hookworm from 122-267. Host age, sex and household size were found to be significant factors influencing faecal egg output, and indirect measure of the intensity of the helminth infections.

Community control of Ascaris lumbricoides in rural Oyo State, Nigeria: mass, targeted and selective treatment with levamisole

A study to compare effects of mass, targeted and selective chemotherapy with levamisole (Ketrax) as an action for the control of Ascaris lumbricoides was carried out in three communities in rural Oyo State, Nigeria. Selective treatment was applied in one village by treating the most heavily infected 20% of the inhabitants, targeted treatment in the second village involved children aged 2-15 years, while mass treatment was offered to all inhabitants excluding infants under 1 year and pregnant women in the third village. Recommended doses of levamisole were given in the villages, as described above, at 3-monthly intervals during a period of 1 year. Prevalence and intensity (epg) of A. lumbricoides infection were determined immediately before and 3 months after the period of intervention using a modified Kato-Katz technique. In the selective treatment village, no significant differences were found between the pre- and post-treatment egg counts (mean (+/- S.D.) epg 6776 +/- 10,791 versus 4259 +/- 10,909 respectively) of A. lumbricoides in the total population. In the targeted treatment village, significant differences were recorded in pre- and post-treatment egg counts for the total population (9057 +/- 15,797 versus 2579 +/- 6529) among the children alone (10,935 +/- 20,094 versus 992 +/- 3175) and among the untreated adults (7742 +/- 9782 versus 4561 +/- 8798). In the mass treatment village, significant differences in pre- and post-treatment egg count values were also recorded (11,907 +/- 17,220 versus 1489 +/- 5165). The intensity of Trichuris trichiura and hookworm infections among the villagers before and after intervention were not observed to have changed significantly regardless of selective, targeted or mass treatment.

Prevalência e intensidade de infecção por Ascaris lumbricoides em amostra populacional urbana (São Paulo, SP)

Pesquisaram-se ovos de Ascaris lumbricoides em amostras fecais de 407 moradores (8,87% do total) de uma favela da cidade de São Paulo. Realizaram-se exames qualitativos (sedimentação por gravidade) e quantitativos (técnica de Kato & Miura adaptada a contagens). Discutem-se aspectos diferenciais da epidemiologia da ascaríase em áreas urbanas e rurais, com base em dados deste estudo e da literatura. Salienta-se a importância, em epidemiologia, da quantificação de exames de fezes.