Schistosomiasis: an epidemiological update on Brazil's southernmost low endemic area in Esteio

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.

Mollusk microbiota shift during Angiostrongylus cantonensis infection in the freshwater snail Biomphalaria glabrata and the terrestrial slug Phillocaulis soleiformis

In the present work, we reported for the first time the microbiome from Phyllocaulis soleiformis and Biomphalaria glabrata assessed using high-throughput DNA sequencing pre- and post-infection with the helminth parasite Angiostrongylus cantonensis. B. glabrata and P. soleiformis were experimentally infected with A. cantonensis. Fecal DNAs from control and infected groups were extracted and subjected to 16S rRNA high-throughput sequencing survey. No significant differences were found in the alpha diversity indexes in Phyllocaulis and Biomphalaria experiments independently. PCoA analysis using the unweighted UniFrac measures showed that both microbiotas behaved differently depending on the host. In Biomphalaria microbiota, control and infected groups were significantly different (p = 0.0219), while Phyllocaulis samples were not (p = 0.5190). The microbiome of P. soleiformis infected with A. cantonensis showed a significant decrease of Sphingobacterium and a substantial increase of Cellvibrio when compared to a control group. The microbiome of B. glabrata infected with A. cantonensis showed a significant decline in the abundance of Flavobacterium, Fluviicola, Nitrospira, Vogesella and an OTU belonging to the family Comamonadaceae, and a significant increase of Uliginosibacterium and an OTU belonging to the family Weeksellaceae when compared to a control group. Overall, the microbiome data reported here provided valuable information with regard to the diversity of bacterial communities that comprise the gut microbiome of gastropods. Furthermore, we report here the effect of the infection of the helminth A. cantonensis in the ratio and distribution of the fecal microbiome of the snails. Further studies are highly valuable in order to better understand those interactions by comparing different microbiome profiles and mollusk models. By now, we anticipate that ecological studies will take significant advantage of these advances, particularly concerning improving our understanding of helminth-microbiome-host interactions.

Study of diagnostic accuracy of Helmintex, Kato-Katz, and POC-CCA methods for diagnosing intestinal schistosomiasis in Candeal, a low intensity transmission area in northeastern Brazil

Control initiatives have successfully reduced the prevalence and intensity of schistosomiasis transmission in several localities around the world. However, individuals that release low numbers of eggs in their feces may not be detected by classical methods that are limited by low sensitivity. Given that accurate estimates of prevalence are key to implementing planning control actions for the elimination of schistosomiasis, new diagnostic tools are needed to effectively monitor infections and confirm transmission interruption. The World Health Organization recommends the Kato-Katz (KK) thick smear as a parasitological test for epidemiological surveys, even though this method has been demonstrated to underestimate prevalence when egg burdens are low. The point-of-care immunodiagnostic for detecting schistosome cathodic circulating antigen (POC-CCA) method has been proposed as a more sensitive substitute for KK in prevalence estimations. An alternative diagnostic, the Helmintex (HTX) method, isolates eggs from fecal samples with the use of paramagnetic particles in a magnetic field. Here, a population-based study involving 461 individuals from Candeal, Sergipe State, Brazil, was conducted to evaluate these three methods comparatively by latent class analysis (LCA). The prevalence of schistosomiasis mansoni was determined to be 71% with POC-CCA, 40.% with HTX and 11% with KK. Most of the egg burdens of the individuals tested (70%) were < 1 epg, thereby revealing a dissociation between prevalence and intensity in this locality. Therefore, the present results confirm that the HTX method is a highly sensitive egg detection procedure and support its use as a reference method for diagnosing intestinal schistosomiasis and for comparative evaluation of other tests.