Assessment of dual schistosome infection prevalence from urine in an endemic community of Ghana by molecular diagnostic approach

Schistosomiasis is an important Neglected Tropical Disease caused by blood parasites called schistosomes. In sub-Saharan Africa, two major human schistosomes, namely Schistosoma mansoni and S. haematobium, often occur sympatrically and is responsible for almost 90% of the affected 290 million people worldwide. We have utilized a highly sensitive and specific assay by amplifying species-specific cell-free repeat DNA fragments by polymerase chain reaction to detect either single or dual schistosome infection from a single urine sample from a broad age group. In this study, we have tested filtered urine samples collected from 163 individuals aged 3–63 years, mostly children (median age 10), to evaluate the prevalence of single and dual infections for S. mansoni and S. haematobium in Tomefa community in the Greater Accra region of Ghana. 40–50 mL of urine was filtered through a 12.5 cm Whatman # 3 filter paper in the field. The filter papers were dried, packed individually in sealable plastic bags with a desiccant, and shipped to Marquette University, where DNA was isolated and PCR amplification was carried out with species-specific primers. Disease prevalence was found to be 46.6% for S. mansoni and 48.5% for S. haematobium. Most importantly, 23.3% of participants had dual infections. All of the samples were detected without any cross amplification. The data was evaluated for four age groups and infection rate was highest for the age group of 3–12 years, with more S. haematobium infections than S. mansoni infections. We found a high prevalence of both S. haematobium and S. mansoni infection and a significant proportion of dual infection for the Tomefa community, which in most cases would be missed by traditional parasitological examination of urine or stool. Our highly sensitive and specific approach for detecting underlying multiple schistosome infections is an effective means to detect low intensity infections and would enhance the effectiveness of surveillance and Mass Drug Administration control programs of schistosomiasis.

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WHO recommended gold-standard tests misses low-level schistosomiasis infection.

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Cell-free repeat DNA detection can identify significant number of such infection.

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Both schistosome species can be detected effectively from a single urine sample.

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Infection rate is higher for younger age group.

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Dual infection rate is higher in Tomefa community of Ghana.

Detection of parasite-specific DNA in urine sediment obtained by filtration differentiates between single and mixed infections of Schistosoma mansoni and S. haematobium from endemic areas in Ghana

Differential diagnosis of Schistosoma mansoni and S. haematobium, which often occur sympatrically in Africa, requires both urine and stool and the procedures are low in sensitivity. The standard diagnostic tests, such as Kato-Katz (KK) for S. mansoni eggs and presence of haematuria for S. haematobium both lack sensitivity, produce false-negative results and show reduced accuracy with decreasing intensity of infection. The need for a single diagnostic test with high sensitivity and specificity for both parasites is important as many African countries are implementing Mass Drug Administration (MDA) following recommendations of the World Health Organization (WHO). Eighty-six samples of urine sediment obtained by filtration were collected from a group of 5–23 years old people from an endemic area of southern Ghana. DNA was extracted from the urine sediment on filter paper from which a species-specific repeat fragment was amplified by polymerase chain reaction (PCR) with specific primers for S. mansoni and for S. haematobium. Additionally, all participants were tested by KK (stool) and dipstick for haematuria. Diagnostic parameters for all three tests were analyzed statistically. Amplification of species-specific DNA by PCR showed much higher sensitivity (99%–100%) and specificity (100%) compared to KK and haematuria (sensitivity: 76% and 30% respectively) for both schistosome species. The same pattern was observed when the data were stratified for age group and sex specific analysis. In addition PCR amplification detected DNA from 11 individuals infected with both parasites who were negative by KK and haematuria. This approach of detecting parasite specific DNA from either or both species in a single urine specimen is a practical advantage that avoids the need for two specimens and is more effective than standard tests including those based on serology. This promises to improve the effectiveness of surveillance of MDA control programs of schistosomiasis.

Hypermethylation of genes detected in urine from Ghanaian adults with bladder pathology associated with Schistosoma haematobium infection

PURPOSE

Schistosoma haematobium is associated with chronic bladder damage and may subsequently induce bladder cancer in humans, thus posing a serious threat where the parasite is endemic. Here we evaluated aberrant promoter DNA methylation as a potential biomarker to detect severe bladder damage that is associated with schistosomiasis by analyzing urine specimens.

MATERIALS AND METHODS

A quantitative methylation-specific PCR (QMSP) assay was used to examine the methylation status of seven genes (RASSF1A, RARβ2, RUNX3, TIMP3, MGMT, P16, ARF) in 57 urine samples obtained from volunteers that include infected and uninfected by S. haematobium from an endemic region. The Fishers Exact Test and Logistic Regression analysis were used to evaluate the methylation status with bladder damage (as assessed by ultrasound examination) in subjects with S. haematobium infection.

RESULTS

RASSF1A and TIMP3 were significant to predict severe bladder damage both in univariate (p = 0.015 and 0.023 respectively) and in multivariate (p = 0.022 and 0.032 respectively) logistic regression analysis. Area under the receiver operator characteristic curves (AUC-ROC) for RASSF1A and TIMP3 to predict severe bladder damage were 67.84% and 63.73% respectively. The combined model, which used both RASSF1A and TIMP3 promoter methylation, resulted in significant increase in AUC-ROC compared to that of TIMP3 (77.55% vs. 63.73%.29; p = 0.023).

CONCLUSIONS

In this pilot study, we showed that aberrant promoter methylation of RASSF1A and TIMP3 are present in urine sediments of patients with severe bladder damage associated with S. haematobium infection and that may be used to develop non-invasive biomarker of S. haematobium exposure and early molecular risk assessmentof neoplastic transformation.

Schistosoma mansoni: cercaricidal effects of cedarwood oil and various of its components

Cercariae of Schistosoma mansoni exposed to cedarwood oil show early phases of the penetration response before they succumb to the toxic effects of the oil. The toxic effect is also seen when cercariae are exposed to certain components of the oil followed by exposure to a known penetration stimulant, linolenic acid, which accelerates the inactivation of the organism. It is postulated that the process of penetration which results in the disruption of the cercarial glycocalyx alters physiological processes related to osmoregulation. This may increase the absorption of the toxic substances in cedarwood oil by the organisms.

Effects of anethole dithiolthione and 2(3)-tert-butyl-4-hydroxyanisole on schistosome granuloma formation

Administration of the antioxidants 2(3)-tert-butyl-4-hydroxyanisole (BHA) or 5-(P-methoxyphenyl)-3H-1,2-dithiol-3-thione (ADT) to female CD-1 mice starting 4 weeks after infection with 70 cercariae of Schistosoma mansoni resulted in a decrease in the size of the inner fibrotic region of the hepatic granuloma. The cellular composition of the granuloma was not altered by treatment with these two compounds. The administration of the specific superoxide scavenger copper diisopropylsalicylate (CuDIPS) resulted in a similar decrease in granuloma size, suggesting a role of superoxide radicals in the granulomatous response.