Accuracy of diagnosis of urinary schistosomiasis: Comparison of parasitological and a monoclonal antibody-based dipstick method

Immunolocalization of the 29 kDa Schistosoma haematobium species-specific antigen: a potential diagnostic marker for urinary schistosomiasis

BACKGROUND

The 29 kDa Schistosoma haematobium species-specific antigen (ShSSA) is of remarkable interest in the diagnosis of urinary schistosomiasis although it had not been fully characterized.

METHOD

To determine the biological importance of ShSSA in S. haematobium and pathogenesis of the disease, we immunolocalized ShSSA in schistosome eggshells, miracidia and adult worm sections using indirect fluorescent antibody test (IFAT).

RESULTS

ShSSA was strongly immunolocalized in the schistosome eggshells, selective regions of the miracidia body and walls of internal organs such as oviduct, ovary, vitelline duct and gut of the adult worm.

CONCLUSION

The strong immunolocalization of ShSSA in schistosome eggshells and adult worm internal organs suggests that the antigens involved in the pathogenesis of urinary schistosomiasis could have originated from the eggs and adult worms of the parasite. The findings also indicate that ShSSA may play a mechanical protective role in the survival of the parasite.

Diagnostic accuracy of urine filtration and dipstick tests for Schistosoma haematobium infection in a lightly infected population of Ghanaian schoolchildren

Two screening methods, reagent dipsticks for hematuria and urine filtration for Schistosoma haematobium eggs, were evaluated for their sensitivity and specificity in diagnosing infection with S. haematobium in lightly infected Ghanaian children. Schoolchildren aged 8-18 years (n=255) provided urine samples on three occasions. Overall, 36.4% of girls and 50.7% of boys presented with eggs at least once; 3.3% of girls and 7.5% of boys presented with both eggs and hematuria three times. Many children presented with eggs but without hematuria, or with hematuria but without eggs. When each child was screened three times, the sensitivity of each test method improved by at least 22.9% as compared with single screening, but previously unidentified infections were detected at the third screening, indicating that even three screenings is insufficient. Nearly half of lightly infected children (<50 eggs/10 ml urine, by maximum egg count) were egg-positive during only one of three screenings. Thus, data presented here indicate that when individuals are screened repeatedly, infection status can be assessed more accurately, control programs can be properly evaluated, and population estimates of S. haematobium infection may be made with increased confidence, as compared with single screening.

Genitourinary schistosomiasis among pre-primary schoolchildren in a rural community within the Cross River Basin, Nigeria

In Africa, most schistosomiasis control programmes defined the age 5-19 years as the target population for nationwide control through the school systems, excluding the under fives. A study was therefore undertaken to determine the prevalence and intensity of genitourinary schistosomiasis in children aged 0-5 years (pre-primary) in Adim, a rural and endemic community within the Cross River Basin, Nigeria. Of the 126 children examined, 25 (19.8%) were infected with Schistosoma haematobium, with no significant difference (P > 0.05) in infection rates between boys (21.1%) and girls (18.2%). Both prevalence and intensity of infection increased significantly (P 0.05) between intensity in boys (6.2 eggs/10 ml urine) and girls (5.6 eggs/10 ml urine). A total of 32.5 and 27.8% of the children had haematuria and proteinuria, respectively; it was not gender specific (P > 0.05). Six species of snail were encountered, with Bulinus globosus being the most abundant and widespread. The results of this study have shown that pre-primary schoolchildren are a source of transmission of schistosomiasis in endemic communities and should be integrated into any control intervention.

Applicability of a monoclonal antibody-based dipstick in diagnosis of urinary schistosomiasis in the Central Region of Ghana

Summary We tested a rapid visually read monoclonal antibody (MoAb) based dipstick assay for specific diagnosis of urinary schistosomiasis against microscopy and the use of haematuria and proteinuria in a schistosomiasis haematobia endemic area in the Central Region of Ghana. The study group consisted of 141 school children (83 males, 58 females) aged 8-19 years. A total of 129 of 141 (91.5%) submitted stool samples, and 7.8% had Schistosoma mansoni, 55% had hookworms and 6.2% had tapeworms. The presence of S. mansoni and intestinal parasites did not appear to influence the results of the MoAb-dipstick assay. The urinary schistosomiasis prevalence by MoAb-dipstick (78%) was higher (P < 0.05) than the estimate by microscopy (60.3%), microhaematuria (27%) and proteinuria (30.5%). The MoAb-dipstick correctly identified 98.8% of microscopically confirmed cases and missed one (1.3%). The dipstick was also positive for 26 of 56 (46.4%) egg-negative individuals, thereby giving a sensitivity of 98.8% and a specificity of 53.6%. On the other hand, microhaematuria and proteinuria were 38.8% and 30.6% sensitive, and 91.1% and 69.6% specific, respectively. Microhaematuria and proteinuria were less sensitive (P < 0.05) than both microscopy and MoAb-dipstick.

Infant schistosomiasis in Ghana: a survey in an irrigation community

We used a rapid, visually read, field applicable monoclonal antibody (MoAb)-dipstick assay for specific diagnosis of urinary schistosomiasis together with microscopy to determine the prevalence of infant schistosomiasis in a community in the Awutu-Efutu Senya District in the Central Region of Ghana. The study group consisted of 97 infants (51 males and 46 females) aged 2 months to 5 years. A total of 75 of 97 (77.3%) subjects submitted stool samples; none had Schistosoma mansoni. Three individuals (3.1%) had hookworms but there were no other intestinal helminths. The urinary schistosomiasis prevalence by MoAb-dipstick (30%) was higher (P < 0.05) than that estimated by microscopy (11.2%). However, three of nine (33.3%) microscopically confirmed cases tested MoAb-dipstick positive after pre-treatment of the urine specimen with heat. The youngest infant to be found infected with S. haematobium microscopically was 4 months old. Fifteen of 71 S. haematobium egg negative individuals tested dipstick positive, giving a dipstick specificity of 78.9% as compared with microscopy as gold standard test. The relative sensitivity of the dipstick was 100%.