The GSA Blog

Research highlights for the first half of 2017!

A plethora of research outputs were published and shared in the early part of 2017, advancing our knowledge of schistosomiasis and equipping us to better diagnose, treat and control the disease thereby edging us closer to schistosomiasis control and elimination goals. Here are 10 research articles that caught our eye:

1.       Biomphalaria Genome: “Whole genome analysis of a schistosomiasis-transmitting freshwater snail”.  A mammoth job to describe the complex genome of one of the main snail vectors of intestinal schistosomiasis. This exciting publication and the availability of the Biomphalaria genome has opened a whole new era of vector and transmission research which has the very real potential to uncover novel tools for schistosomiasis transmission prevention and control!

2.       Praziquantel in preschool children: “Efficacy and safety of praziquantel in preschool-aged and school-aged children infected with Schistosoma mansoni: a randomized controlled, parallel-group, dose-ranging, phase 2 trial”. We are all keenly awaiting the new pediatric formulation of Praziquantel but safety is paramount and this trial is one of the very necessary steps to achieving a safe and effective pediatric treatment for schistosomiasis in preschool aged children.

3.       Epigenetics research on the schistosome - snail system: “The Biomphalaria glabrata DNA methylation machinery displays spatial tissue expression, is differentially active in distinct snail populations and is modulated by interactions with Schistosoma mansoni”.  Epigenetics, the study of how and why some genes are expressed whilst others are not, is a buzz word in today’s genome era. This study documents how schistosome infections can modify gene expression in snails, and how this may lead to infection success or failure. Advancing our knowledge in this area may again lead to effective transmission control tools. Whilst application is a huge driving force of scientific research, the more research-focused reader will just think this is cool!

4.       Community-wide preventative chemotherapy: “Evaluating the variation in the projected benefit of community-wide mass treatment for schistosomiasis: Implications for future economic evaluations”. The debate of community-wide (CW) v.s. school-based (SB) mass treatment campaigns rages on but the authors of this study demonstrate that the choice of mass treatment strategy should depend on the epidemiological and social settings of the target area. Using defined schistosomiasis transmission models the authors show that in areas of low school enrollment CW-MDA might benefit the area more than SB-MDA.

5.       The impact of Schistosoma hybrids: “Hybridizations within the Genus Schistosoma: implications for evolution, epidemiology and control” The causative agent of urogenital schistosomiasis, S. haematobium, is known to be able to hybridize with several domestic animal schistosome species, particularly the cattle species, S. bovis. Recently a perceived increase in the occurrence of hybrid schistosome infections has caused some consternation to those battling to control the disease in West Africa. Researchers are working to determine just how wide-spread the problem is and what the implications could be for treatment programmes and schistosomiasis control and elimination goals.

6.       Praziquantel treatment efficacy for intestinal schistosomiasis: “Praziquantel decreases fecundity in Schistosoma mansoni adult worms that survive treatment: evidence from a laboratory life-history trade-offs selection study”. Looking at the schistosome parasites adaptive flexibility can give us crucial insight on praziquantel treatment success and sustainability. This research looked at what happens to schistosomes that survive treatment events in lab settings. The authors report reduced egg output in the survivors even after further drug treatment. This has implications for monitoring and surveillance activities based on egg-detection in stool. The stool may be coming out schisto-free but the worms could very much still be there even after repeated treatments! A worrying observation considering our reliance on the one-drug for all infections, Praziquantel.

7.       Schistosomiasis diagnosis in an elimination setting: “Selecting accurate post-elimination monitoring tools to prevent reemergence of urogenital schistosomiasis in Morocco: a pilot study”. With regions and countries looking towards elimination for schistosomiasis what diagnostic tests are out there to monitor and test for new or imported light infections? This study compares antibody tests that detect exposure and the CAA antigen test that detects active infection.

8.       Schistosomiasis outbreak or endemic transmission? “Large outbreak of urogenital schistosomiasis acquired in Southern Corsica: monitoring the early signs of the endemicization?”. The 2014 outbreak of schistosomiasis in Corsica, France raised a lot of alarms. Especially since a snail species known to be a vector of schistosomiasis is well established in parts of southern Europe. Researchers are now asking, was this a new outbreak or has transmission been occurring at a low level? And how we monitor for the switch from “outbreak” to “endemic”?

9.       Schistosoma mansoni and HIV infection: “Effects of schistosomiasis on susceptibility to HIV-1 infection and HIV-1 viral load at HIV-1 seroconversion: A nested case-control study”. The link between HIV and schistosomiasis becomes stronger and stronger as evidence of causal effect increases. The higher risk of HIV acquisition when infected with S. haemabotium is known but this study also shows that women infected with S. mansoni are not only far more susceptible to HIV but also that their viral load is higher at sero-conversion if they have S. mansoni.

10.   Schistosoma mekongi in Cambodia and Lao PDR: “Comparison of novel and standard diagnostic tools for the detection of Schistosoma mekongi infection in Lao People’s Democratic Republic and Cambodia”. S. mekongi has been recommended for elimination in endemic areas and this requires far more sensitive diagnostics techniques than the traditional Kato-katz used. This article looks at the use and applicability of Kato-Katz, ELISA, POC-CCA and CAA in diagnosing S. mekongi. The resulting recommendation is to plan wider testing with a more sensitive diagnostic to identify the true geographical extent of S. mekongi in Lap PDR and Cambodia.