Accuracy of commercial ELISA and ICT for screening schistosomiasis infections at a low endemicity area in Brazil.

BACKGROUND: Control interventions recommended by the World Health Organization have successfully resulted in low-intensity schistosomiasis transmission areas. To achieve elimination of transmission, new diagnostic screening tools are needed to overcome less than adequate sensitivity of the currently used Kato-Katz faecal thick smear method. Ideally, in-house serological tests should be avoided due to not having a continuous supply of kits as would be necessary for large population studies. Quality assurance provided by manufacturers and proper performance evaluations are also needed. We evaluated the accuracy of two commercially available serology tests as screening methods for detecting light schistosomiasis infections. METHODS: Serum samples were collected in 2015 from individuals living in a low-endemicity locality in northeastern Brazil and deposited in a biorepository. We evaluated immunoglobulin G (IgG) and IgM enzyme-linked immunosorbent assays (ELISAs) and an immunochromatographic test (ICT). The Helmintex method was used to define true-positive samples. RESULTS: Overall sensitivity was close to 90% for both the IgG ELISA and ICT, yet specificity was 28% and 18%, respectively. For the IgM ELISA, the values were estimated to be 55% and 43%, respectively. CONCLUSIONS: Poor specificity and positive predictive values prevent these tests from being recommended for screening populations in low-intensity schistosomiasis-endemic areas.

Schistosomiasis: an epidemiological update on Brazils southernmost low endemic area in Esteio

Abstract INTRODUCTION: Brazil's southernmost state, Rio Grande do Sul (RGS), was considered schistosomiasis-free until 1998 when a low endemic focus was identified in Esteio, a city located next to the capital of RGS. In the last two decades, the control interventions applied in the region have been apparently successful, and the absence of new cases indicated the possibility of interrupted schistosomiasis transmission. The objective of this study was to update the clinical and epidemiological data of schistosomiasis in Esteio. METHODS: We reviewed all 28 individuals diagnosed with the infection since 1997 and a survey was applied to a group of 29 school-aged children residing in Vila Pedreira, one of the most affected neighborhoods. RESULTS No eggs were detected in fecal samples using the Helmintex method, and all samples were negative for serum antibodies on examination by the western blot technique using the Schistosoma mansoni microsomal antigen (MAMA- WB). In contrast, 23 individuals (79%) tested positive for the cathodic circulating antigen with the point-of-care immunochromatographic test (POC-CCA) on urine samples. Of the 28 formerly infected individuals, only eight were located, of which four tested positive, and four tested negative for serum antibodies using the MAMA-WB technique. CONCLUSIONS: Current adverse conditions for S. mansoni transmission in Esteio and the absence of a confirmed diagnosis suggests that there is (i) a lack of specificity of the POC-CCA test in low endemic settings, and (ii) a high probability that interruption of schistosomiasis has been achieved in Esteio.

Risk factors for colistin-resistant Enterobacteriaceae in a low-endemicity setting for carbapenem resistance - a matched case-control study.

BackgroundEmergence of colistin resistance has been related to increased use in clinical settings, following global spread of carbapenem-resistant Gram-negative bacteria. Use of colistin in animal production may constitute a further source of spread of resistant strains to humans. We sought to determine risk factors for human colonisation or infection with colistin-resistant Escherichia coli and Klebsiella pneumoniae in a setting where colistin is mainly used for animal production. Methods: This retrospective matched case-control study was performed during a 5-year period at two university-affiliated hospitals in Basel, Switzerland. Conditional univariable logistic regression was used to calculate odds ratios (OR) for colistin resistance. All variables found to be significant in univariable analyses were included in the conditional multivariable regression model using stepwise forward and backward selection. Results: Forty-two cases (33 with colistin-resistant E. coli, 9 with colistin-resistant K. pneumoniae) and 126 matched controls were identified. Baseline characteristics, comorbidities, prior exposure to antibiotics and healthcare settings did not differ between cases and controls, except for prior exposure to carbapenems, hospitalisation and stay abroad during the prior 3 months. In multivariable analyses, only prior exposure to carbapenems remained associated with colistin resistance (OR: 5.00; 95% confidence interval (95% CI): 1.19-20.92; p = 0.028). Conclusion: In a low-endemicity setting for carbapenem resistance, prior exposure to carbapenems was the only risk factor for colonisation or infection with colistin-resistant E. coli or K. pneumoniae. Prior exposure to colistin was not significantly associated with detection of colistin resistance, which mainly occurred in the absence of concurrent carbapenem resistance.

"Alert-Audit-Act": assessment of surveillance and response strategy for malaria elimination in three low-endemic settings of Myanmar in 2016.

BACKGROUND: Myanmar, a malaria endemic country of Southeast Asia, adopted surveillance and response strategy similar to "1-3-7" Chinese strategy to achieve sub-national elimination in six low-endemic region/states of the country. Among these, Yangon, Bago-East, and Mon region/states have implemented this malaria surveillance and response strategy with modification in 2016. The current study was conducted to assess the case notification, investigation, classification, and response strategy (NICR) in these three states. METHODS: This was a retrospective cohort study using routine program data of all patients with malaria diagnosed and reported under the National Malaria Control Programme in 2016 from the above three states. As per the program, all malaria cases need to be notified within 1 day and investigated within 3 days of diagnosis and response to control (active case detection and control) should be taken for all indigenous malaria cases within 7 days of diagnosis. RESULTS: A total of 959 malaria cases were diagnosed from the study area in 2016. Of these, the case NICR details were available only for 312 (32.5%) malaria cases. Of 312 cases, the case notification, investigation, and classification were carried out within 3 days of malaria diagnosis in 95.5% cases (298/312). Of 208 indigenous malaria cases (66.7%, 208/312), response to control was taken in 96.6% (201/208) within 7 days of diagnosis. CONCLUSION: The timeline at each stage of the strategy namely case notification, investigation, classification, and response to control was followed, and response action was taken in nearly all indigenous malaria cases for the available case information. Strengthening of health information and monitoring system is needed to avoid missing information. Future research on feasibility of mobile/tablet-based surveillance system and providing response to all cases including imported malaria can be further studied.

Evaluating a point-of-care circulating cathodic antigen test (POC-CCA) to detect Schistosoma mansoni infections in a low endemic area in north-eastern Brazil.

Schistosomiasis is still a public health problem in Brazil. The Kato-Katz test is the most frequently used diagnostic method for Schistosoma mansoni infection. However, it lacks sensitivity in areas of low prevalence. We have assessed the positivity rate of S. mansoni infection in Bananeiras, a village on Capistrano, Ceara, Brazil by performing a point-of-care test in urine to determine the circulating cathodic antigens (POC-CCA), and we compared the findings with those of the Kato-Katz technique for egg detection in stool and an enzyme-linked immunosorbent assay for specific antibodies against adult worms (SWAP-ELISA) in serum before treatment (baseline). Additionally, the POC-CCA and Kato-Katz test results were compared at one and two years post-treatment, and only POC-CCA strips were utilised for follow-up testing on urine samples at 3-6 weeks. Only one sample of stool and urine was collected per event. Overall, 258 individuals were investigated at the baseline. The POC-CCA test detected 10 (3.9%) positive cases; however, this amount increased to 30 (11.6%) when considering trace readings as positive (t + ), whereas the Kato-Katz method found only 4 (1.6%) positive cases and the SWAP-ELISA detected 105 (40.7%) positive cases. The consistency observed between a single POC-CCA (t + ) or (t-) and the Kato-Katz (three slides) was poor (Kappa indexes <0.20). The highest positivity rate as determined by CCA and Kato-Katz was found in adults. At the baseline, a praziquantel treatment was administered to all individuals regardless of their infection status. According to the POC-CCA test, 93% of the previous positive cases became negative by the third week after the treatment; this rate reached 100% at the sixth week assessment. The follow-up showed that of the 175 individuals evaluated at one year post-treatment, only one (0.6%) showed 'trace' results, and all the individuals were negative for eggs in the stool. At two years, all 185 examined individuals were negative by the Kato-Katz method, and 11 (5.9%) presented traces by POC-CCA. Our results indicate that a single POC-CCA test reveals a significantly higher number of positive cases than the Kato-Katz technique for diagnosing S. mansoni in a low endemic setting, when trace results are considered as positive cases. Nevertheless, the true significance of the trace is not clear. These findings reinforce the need to associate different tools for improved schistosomiasis diagnosis in individuals with low parasite burdens.

The affinity of magnetic microspheres for Schistosoma eggs.

Schistosomiasis is a chronic parasitic disease of humans, with two species primarily causing the intestinal infection: Schistosoma mansoni and Schistosoma japonicum. Traditionally, diagnosis of schistosomiasis is achieved through direct visualisation of eggs in faeces using techniques that lack the sensitivity required to detect all infections, especially in areas of low endemicity. A recently developed method termed Helmintex™ is a very sensitive technique for detection of Schistosoma eggs and exhibits 100% sensitivity at 1.3 eggs per gram of faeces, enough to detect even low-level infections. The Helminthex™ method is based on the interaction of magnetic microspheres and schistosome eggs. Further understanding the underlying egg-microsphere interactions would enable a targeted optimisation of egg-particle binding and may thus enable a significant improvement of the Helmintex™ method and diagnostic sensitivity in areas with low infection rates. We investigated the magnetic properties of S. mansoni and S. japonicum eggs and their interactions with microspheres with different magnetic properties and surface functionalization. Eggs of both species exhibited higher binding affinity to the magnetic microspheres than the non-magnetic microspheres. Binding efficiency was further enhanced if the particles were coated with streptavidin. Schistosoma japonicum eggs bound more microspheres compared with S. mansoni. However, distinct differences within eggs of each species were also observed when the distribution of the number of microspheres bound per egg was modelled with double Poisson distributions. Using this approach, both S. japonicum and S. mansoni eggs fell into two groups, one having greater affinity for magnetic microspheres than the other, indicating that not all eggs of a species exhibit the same binding affinity. Our observations suggest that interaction between the microspheres and eggs is more likely to be related to surface charge-based electrostatic interactions between eggs and magnetic iron oxide rather than through a direct magnetic interaction.

Seeding experiments demonstrate poor performance of the hatching test for detecting small numbers of Schistosoma mansoni eggs in feces.

Parasitological methods for the evaluation of schistosomiasis tend to be limited when parasitic burdens are low, which is a major characteristic of low intensity transmission areas. While the hatching test (HT) method has been considered to be "very sensitive", reports of its capacity to detect low numbers of eggs remain scarce in the published literature. Our main hypothesis is that HT has limitations and cannot be recommended for diagnosing light infections or as a control of cure. Hence, this study aims to describe the performance of HT in detail, with respect to seeding experiments for egg numbers in the range of 4 to 24 eggs per gram (epg) of feces. Different numbers of eggs of Schistosoma mansoni were seeded in normal human feces. The first set of experiments evaluated the amount of feces (higher than 0.5 g prevented hatching), the proximity of the light source (50 cm was preferred), and the observation time required for the detection of miracidia (more than 3h did not add to sensitivity). HT was subsequently performed with 12, 10, 8, 6, 4, and 2 eggs in 0.5 g of feces. The final set of experiments was performed to analyze the initial filtration step, in which surgical gauze versus a 500 µm nylon mesh was compared and demonstrated losses of eggs that occurred with washing and gauze (better with nylon) sieving steps. The proposed method was found to produce 100% positivity for up to 12 epg, with a sharp decrease to 33% for 8 epg and less. In conclusion, HT is not recommended for diagnosing intestinal schistosomiasis in populations with light infections, considering the complexity of the procedure and its lack of effectiveness with fecal amounts higher than 0.5 g even at optimized conditions.

Polymerase chain reaction for the evaluation of Schistosoma mansoni infection in two low endemicity areas of Minas Gerais, Brazil

This study aimed to evaluate the occurrence of schistosomiasis in areas with low endemicity using polymerase chain reaction (PCR) as a diagnostic method. We analysed faecal samples from 219 individuals residing in Piau and Coronel Pacheco, state of Minas Gerais, Brazil, using a single faecal sample from each individual and two slides of the Kato-Katz technique as a gold standard. Fifteen out of the 219 samples were positive with both methods of diagnosis. One sample was diagnosed as positive by the Kato-Katz technique only and 61 were diagnosed only by PCR. The positivity rates were 7.3% with the Kato-Katz method and 34.7% with PCR. When both techniques were assumed to have 100% specificity and positive individuals were identified by both methods, the sensitivity of the Kato-Katz method was 20.8% and the PCR sensitivity was 98.7%. The Kappa index between the two techniques was 0.234, suggesting weak agreement. The assessment of a single faecal sample by PCR detected more cases of infection than the analysis of one sample with two slides using the Kato-Katz technique, suggesting that PCR can be a useful diagnostic tool, particularly in areas with low endemicity.

Comparison of the Kato-Katz and Helmintex methods for the diagnosis of schistosomiasis in a low-intensity transmission focus in Bandeirantes, Paraná, southern Brazil

The diagnosis of schistosomiasis is problematic in low-intensity transmission areas because parasitological methods lack sensitivity and molecular methods are neither widely available nor extensively validated. Helmintex is a method for isolating eggs from large faecal samples. We report preliminary results of a comparative evaluation of the Helmintex and Kato-Katz (KK) methods for the diagnosis of schistosomiasis in a low-intensity transmission area in Bandeirantes, Paraná, southern Brazil. Eggs were detected by both methods in seven patients, whereas only Helmintex yielded positive results in four individuals. The results confirm the previously demonstrated higher sensitivity of the Helmintex method compared with the KK method.

Evidences for clustering of schistosoma mansoni eggs in the sediment produced by helmintex

O diagnóstico da esquistossomose em áreas de baixa intensidade de transmissão exige o aprimoramento dos métodos para superar a pouca sensibilidade dos métodos coproparasitológicos clássicos. Helmintex é um método novo, baseadona interação dos ovos de Schistosoma mansoni com partículas paramagnéticas em um campo magnético. Um estudo preliminar de semeadura confirmou a impressão obtida durante exames de rotina com Helmintex, de que os ovos são geralmente encontrados na metade inferior e não na metade superior da coluna de sedimento sob exame. Nove réplicas de 100 ovos foram semeados em fezes não infectadas e cada réplica foi submetida ao Helmintex. Alíquotas de 40 (Miu)L foram retiradas do topo e sequencialmente examinadas ao microscópio óptico, para contagem dos ovos. Em 6 replicas, a maioria dos ovos foram encontrados na metade inferior. Estes achados interessantes podem levar ao aprimoramento da etapa final de isolamento dos ovos e maior sensibilidade no diagnóstico coproscópico da esquistossomose.