Comparison of Kato-Katz, PCR and coproantigen for the diagnosis of Taenia solium taeniasis

Four methods were compared for the diagnosis of human taeniasis caused by Taenia solium. Fecal samples from persons living in a T. solium endemic region of Madagascar were examined for taeniid eggs by the Kato–Katz method. Subsequently, samples positive (n = 16) and negative (n = 200) for T. solium eggs were examined by (i) amplification of the fragment of small subunit of the mitochondrial ribosomal RNA (rrnS) gene using conventional polymerase chain reaction (PCR) and (ii) a nested PCR of a fragment of the T. solium Tso31 gene. Additionally, 12 egg-positive and all egg-negative samples were tested for coproantigen detection. A further 9 egg-positive fecal samples were examined using both PCRs. Of the 12 egg-positive samples tested by PCRs and coproantigen methods, 9 (75%) were positive by rrnS PCR, 3 (25%) using Tso31-nested PCR and 9 (75%) by coproantigen testing. None of the 200 egg-negative fecal samples was positive in either rrnS or Tso31-nested PCR. Twenty of the 25 egg-positive samples (80%) were positive in rrnS PCR, and DNA sequencing of PCR amplicons was obtained from 18 samples, all confirmed to be T. solium. Twelve of the 25 egg-positive samples (48%) were positive in the Tso31-nested PCR, all of which were also positive by rrnS PCR. It is suggested that species-specific diagnosis of T. solium taeniasis may be achieved by either coprological examination to detect eggs or coproantigen testing, followed by rrnS PCR and DNA sequencing to confirm the tapeworm species in egg-positive or coproantigen-positive samples.

Comparison of direct wet mount, Kato-Katz and formol ether sedimentation technique for the diagnosis of hookworm infection in Debre Elias Woreda, Northwest Ethiopia

Hookworm infection is a neglected parasitic disease. Direct wet mount is the usual method for the diagnosis of hookworm in Ethiopia, but its sensitivity is unsatisfactory. A cross-sectional study was therefore conducted from January to February 2018 among 192 study participants in Debre Elias district. Stool samples were processed by three methods: the prevalence of hookworm was 77.6%, 68.2% and 49.0% by Kato-Katz, formol ether sedimentation technique and direct wet mount, respectively. Direct wet mount had relatively low sensitivity (61.4%) compared to formol ether sedimentation technique (85.6%) and Kato-Katz (97.4%). The latter two compared well with the gold standard method with kappa values of κ = 0.94, κ = 0.71 and κ = 0.39, respectively, and are therefore recommended over against the direct wet mount technique in detecting hookworm.

A study on positive school children as indicators of schistosomiasis status in their families

This study aimed to evaluate schistosomiasis positive school children as indicators of infection in their families. Four hundred and sixteen stool samples of children from two primary schools were examined microscopically for Schistosoma mansoni (S. mansoni) after Kato-Katz. Equal numbers from families of schistosomiasis positive and negative school children were examined by Kato-Katz. Circulating cathodic antigen (CCA) cassette test was performed on 100 Kato-Katz negative children to detect missed S. mansoni cases if any. S. mansoni infection rates among the primary school children were 15.3% and 1.6% in high and low prevalence schools respectively. Sixty five percent of school children had light intensity infection. Family members were either negative or exhibited a prevalence rate as low as 5-6% whether related to positive or negative children. A higher infection rate of S. mansoni was detected by the CCA test compared to the Kato-Katz. Conclusively, children can be good indicators of their particular families in areas of limited resources and low endemicity. Efforts are required to permit large scale use of CCA cassette test.

Development and evaluation of a loop-mediated isothermal amplification (LAMP) diagnostic test for detection of whipworm, Trichuris trichiura, in faecal samples

Whipworm infection or trichuriasis caused by Trichuris trichiura is of major public health concern in sub-Saharan Africa, particularly among pre-school and school-going children. It is among the neglected tropical diseases targeted for elimination through mass drug administration (MDA). One of the outcomes of MDA is a rapid decline in levels of infection intensity, making it difficult to monitor effectiveness of control measures using the conventional Kato-Katz procedure, which relies on the microscopic detection of parasite ova in faecal samples. In the present study, a loop-mediated isothermal amplification (LAMP) test was developed for the detection of T. trichiura infection in faecal samples. LAMP technology offers greater sensitivity and specificity than the microscopy-based tests. A set of four specific primers targeting the internal transcribed spacer 2 region of the ribosomal DNA were designed using Primer Explorer software. DNA was extracted from faecal samples using the alkaline lysis method (HotSHOT) and the LAMP reaction performed at 63°C for 1 h. The amplicons were visualized by both gel electrophoresis and with the naked eye following staining with SYBR green dye. Sensitivity and specificity tests were determined using the standard Kato-Katz diagnostic procedure as a reference test. The developed LAMP assay reliably detected T. trichiura DNA in faecal samples, with a specificity and sensitivity of 88% and 77%, respectively. No cross-reactivity was observed with several common helminth parasites. The developed LAMP assay is an appropriate diagnostic method for the detection of T. trichiura DNA in human faecal samples due to its simplicity, low cost, high sensitivity and specificity.

Diagnostic performance of parasitological, immunological and molecular tests for the diagnosis of Schistosoma mansoni infection in a community of low transmission in Venezuela

In Venezuela, areas endemic for schistosomiasis are of low transmission, with low parasite loads. Immunological tests often lack specificity and cannot differentiate past from present infections. Molecular tests are an alternative, although validation studies in endemic areas are needed. The aim of this study was to determine the performance of parasitological, immunological and molecular tests for the diagnosis of Schistosoma mansoni infection in low-transmission settings. A cross-sectional study was carried out in a rural community located in a schistosomiasis-endemic area of Venezuela to determine the prevalence and diagnostic performance of the Kato-Katz (KK) technique, Circumoval Precipitin Test (COPT), ELISA based on soluble egg antigen (ELISA-SEA) with and without treatment with sodium metaperiodate (ELISA-SEA-SMP), and PCR for amplification of the 121 bp highly repeated sequence of Schistosoma mansoni in faeces, urine and serum samples. The highest prevalence rates were obtained with ELISA-SEA (38.7%), COPT (33.3%), ELISA-SEA-SMP (31.5%), PCR on faeces (21.6%), and KK (17.1%), whereas PCR-based prevalence in urine was 6.2% and no positivity was detected in serum samples. Results showed that ELISA-SEA is the best method for the diagnosis of both current and former infections and that PCR on faeces is the best method for detecting recent transmission. The use of different tests that complement one another also allowed for a better diagnosis of Schistosoma mansoni infection, revealing a relatively high prevalence (33.8%) of schistosomiasis in a community of low transmission.

Kato-Katz thick smears as a DNA source of soil-transmitted helminths

Despite the reduction in the prevalence of soil-transmitted helminthiases in many regions of the world, morbidity rates remain high in some rural regions. The Kato-Katz technique is a simple, inexpensive and field-applicable tool commonly used for the diagnosis and worm-burden characterization of these infections. Molecular studies have revolutionized our understanding of the epidemiology and evolutionary genetics of parasites. In this study we recovered helminthic DNA from Kato-Katz slides (n = 93) prepared in 2011 in the Brazilian Amazon. We achieved DNA recovery by polymerase chain reaction (PCR) in 84% of cases for Ascaris sp. and 75% of cases for hookworms. The sequencing confirmed the specific species of the amplicons. The slides stored for a few years could be analysed using this methodology, allowing access to DNA from a large collection of samples. We must consider the Kato-Katz thick smears as a source of helminth DNA. This can significantly reduce logistical difficulties in the field in terms of obtaining, preserving, transporting and initial processing of samples.

Soil-transmitted helminth infections, anemia and undernutrition among schoolchildren in Yirgacheffee, South Ethiopia

Objective

Current data on soil-transmitted helminth infections, anemia and malnutrition that are largely neglected is vital to the control and management of them in a specific setting. This study was, therefore, aimed at determining the status of the three health concerns in one of the high-risk groups, schoolchildren, in South Ethiopia.

Results

Among the 443 sampled schoolchildren, 54% were infected with soil-transmitted helminths (STHs) and 15.4% of them had anaemia, while the prevalence rate of undernutrition was 28.9%. Species-wise, prevalence of STH infections was 21.7, 16.7, 7.2 and 8.4% for Ascaris lumbricoides, the hookworms, Trichuris trichiura and mixed infections, respectively. Untreated drinking water, high frequency of sucking fingernails and open defecation were significantly associated with risk of getting STH infections. Child positivity for STH infection didn’t show any significant association with undernutrition of the children. Anaemia was significantly correlated with hookworm (adjusted odds ratio (AOR) = 2.96, 95% confidence interval (CI) = 2.15, 4.86), A. lumbricoides (AOR = 1.93, 95% CI = 1.13, 3.01) and polyparasitism (AOR = 1.54, 95% CI = 1.04, 2.64). In addition, children with heavy intensities of hookworm infections and those undernourished were more likely to suffer from anaemia with P = 0.001 and P = 0.007, respectively.

Evaluation of Cathodic Antigen Urine Tests for Diagnosis of Schistosoma mansoni Infection in Sudan

Background:

Kato–Katz is the preferred method for the detection of Schistosoma mansoni eggs in stool. However, the sensitivity of this method is low and affected by day-to-day variation in egg excretion. Cathodic antigen urine tests have been proven to be sensitive for the diagnosis of S. mansoni infection in limited studies.

Aim:

To evaluate the accuracy and sensitivity of cathodic antigen urine tests for the diagnosis of S. mansoni infection.

Setting and Design:

This study was conducted in the Gezira Irrigation Scheme in the Gezira State, Sudan. Both S. mansoni and Schistosoma haematobium are endemic in the Gezira State. Kab-Algidad Village situated in Al Kamleen locality was selected for the study. This is a school-based, cross-sectional, comparative study.

Subjects and Methods:

Female school children, aged between 11 and 14 years who consented to participate, were enrolled in the study. Stool samples were examined using Kato–Katz technique and sodium dodecyl sulfate (SDS) digestion method. Urine samples were tested using the circulating cathodic antigen assays for the diagnosis of S. mansoni, and by centrifugation for S. haematobium.

Statistical Analysis Used:

Data were analyzed using the Scientific Package for Social Sciences version 15.

Results:

Cathodic antigen urine tests showed similar sensitivity to SDS and higher sensitivity compared to six Kato–Katz (reference diagnostic test).

Conclusion:

Cathodic antigen urine tests is a useful tool for mapping S. mansoni and may be used to evaluate the interruption of transmission.

New diagnostic tools in schistosomiasis

Schistosomiasis is a water-based parasitic disease that affects over 250 million people. Control efforts have long been in vain, which is one reason why schistosomiasis is considered a neglected tropical disease. However, since the new millennium, interventions against schistosomiasis are escalating. The initial impetus stems from a 2001 World Health Assembly resolution, urging member states to scale-up deworming of school-aged children with the anthelminthic drug praziquantel. Because praziquantel is safe, efficacious and inexpensive when delivered through the school platform, diagnosis before drug intervention was deemed unnecessary and not cost-effective. Hence, there was little interest in research and development of novel diagnostic tools. With the recent publication of the World Health Organization (WHO) Roadmap to overcome the impact of neglected tropical diseases in 2020, we have entered a new era. Elimination of schistosomiasis has become the buzzword and this has important ramifications for diagnostic tools. Indeed, measuring progress towards the WHO Roadmap and whether local elimination has been achieved requires highly accurate diagnostic assays. Here, we introduce target product profiles for diagnostic tools that are required for different stages of a schistosomiasis control programme. We provide an update of the latest developments in schistosomiasis diagnosis, including microscopic techniques, rapid diagnostic tests for antigen detection, polymerase chain reaction (PCR) assays and proxy markers for morbidity assessments. Particular emphasis is placed on challenges and solutions for new technologies to enter clinical practice.

Comparison of three copromicroscopic methods to assess albendazole efficacy against soil-transmitted helminth infections in school-aged children on Pemba Island

BACKGROUND

The diagnostic accuracy of three faecal egg count techniques (Kato-Katz, McMaster and FLOTAC) to assess albendazole efficacy against soil-transmitted helminth (STH) infections was compared.

METHODS

The study is registered with Current Controlled Trials [identifier: ISRCTN90088840]. During September-November 2009, 304 school-aged children on Pemba Island, Tanzania, were screened and those infected with Ascaris lumbricoides, hookworm or Trichuris trichiura were treated with a single dose of albendazole (400 mg). Twenty-one days post-treatment, children provided a single stool sample which was examined using the same diagnostic methods. All stool samples were divided into two aliquots and one was fixed in 5% formalin and examined using FLOTAC and McMaster approximately 6 months after collection.

RESULTS

Using fresh stool samples, comparable prevalences were demonstrated for the three methods at baseline (90-92.2% for T. trichiura, 41.1-52.8% for hookworm, 32.9-37.2% for A. lumbricoides); FLOTAC was the most sensitive method at baseline and follow-up. Albendazole showed high cure rate (CR) against A. lumbricoides (90-97%), moderate CR against hookworm (63-72%) and very low CR against T. trichiura (6-9%), regardless of the technique used. Egg counts (eggs per gram) at baseline were similar for A. lumbricoides and for hookworm among the three methods, and higher using McMaster and Kato-Katz compared with FLOTAC for T. trichiura. All methods were similar for hookworm and A. lumbricoides egg reduction rate (ERR) estimation, but Kato-Katz indicated a significantly higher ERR than McMaster and FLOTAC for T. trichiura. Preserved stool samples revealed consistently lower FECs at baseline and follow-up for all STHs.

CONCLUSION

Further development and validation of standard protocols for anthelminthic drug efficacy evaluation must be pursued.