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1. FMRF‐NH₂‐related neuropeptides in Biomphalaria spp., intermediate hosts for schistosomiasis: Precursor organization and immunohistochemical localization

   https://doi.org/10.1002/cne.25195  

   Rolón‐Martínez, Solymar; Habib, Mohamed_R; Mansour, Tamer_A; Díaz‐Ríos, Manuel; Rosenthal, Joshua_J_C; Zhou, Xiao‐Nong; Croll, Roger_P; Miller, Mark_W (June 2021, Journal of Comparative Neurology)

   Abstract Freshwater snails of the genusBiomphalariaserve as intermediate hosts for the digenetic trematodeSchistosoma mansoni, the etiological agent for the most widespread form of intestinal schistosomiasis. As neuropeptide signaling in host snails can be altered by trematode infection, a neural transcriptomics approach was undertaken to identify peptide precursors inBiomphalaria glabrata, the major intermediate host forS.mansoniin the Western Hemisphere. Three transcripts that encode peptides belonging to the FMRF‐NH₂‐related peptide (FaRP) family were identified inB.glabrata. One transcript encoded a precursor polypeptide (Bgl‐FaRP1; 292 amino acids) that included eight copies of the tetrapeptide FMRF‐NH₂and single copies of FIRF‐NH₂, FLRF‐NH₂, and pQFYRI‐NH₂. The second transcript encoded a precursor (Bgl‐FaRP2;347amino acids) that comprised 14 copies of the heptapeptide GDPFLRF‐NH₂and 1 copy of SKPYMRF‐NH₂. The precursor encoded by the third transcript (Bgl‐FaRP3; 287 amino acids) recapitulatedBgl‐FaRP2but lacked the full SKPYMRF‐NH₂peptide. The three precursors shared a common signal peptide, suggesting a genomic organization described previously in gastropods. Immunohistochemical studies were performed on the nervous systems ofB.glabrataandB.alexandrina, a major intermediate host forS.mansoniin Egypt. FMRF‐NH₂‐like immunoreactive (FMRF‐NH₂‐li) neurons were located in regions of the central nervous system associated with reproduction, feeding, and cardiorespiration. Antisera raised against non‐FMRF‐NH₂peptides present in the tetrapeptide and heptapeptide precursors labeled independent subsets of the FMRF‐NH₂‐li neurons. This study supports the participation of FMRF‐NH₂‐related neuropeptides in the regulation of vital physiological and behavioral systems that are altered by parasitism inBiomphalaria. 

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2. Localization of Cholecystokinin/Sulfakinin Neuropeptides in Biomphalaria glabrata , an Intermediate Host for Schistosomiasis

   https://doi.org/10.1002/cne.70016  

   Rivera, Alana; Bracho‐Rincón, Dina; Miller, Mark_W (January 2025, Journal of Comparative Neurology)

   ABSTRACT Snails belonging to the genusBiomphalariaserve as obligatory intermediate hosts for the trematodeSchistosoma mansoni, the causative agent for the most widespread form of schistosomiasis. The simpler nervous systems of gastropod molluscs, such asBiomphalaria, provide advantageous models for investigating neural responses to infection at the cellular and network levels. The present study examined neuropeptides related to cholecystokinin (CCK), a major multifunctional regulator of central nervous system (CNS) function in mammals. A neural transcriptome generated from the CNS ofBiomphalaria alexandrinaincluded a transcript encoding two CCK‐related peptides, designatedBalex‐CCK1 (pEGEWSYDY_(SO3H)GLGGGRF‐NH₂) andBalex‐CCK2 (NYGDY_(SO3H)GIGGGRF‐NH₂). Peptide expression was examined inBiomphalaria glabrataat the mRNA level using the hybridization chain reaction (HCR) protocol and at the protein level using an antibody againstBalex‐CCK1. Expression was detected in 60–70 neurons distributed throughout the CNS, as well as in profuse fiber systems connecting the ganglia and projecting to the periphery. CCK‐like immunoreactive (CCK_li) fibers were also observed on organs associated with the cardiorespiratory (nephridium, mantle, gill) and male reproductive systems. A comparison of mRNA and peptide localization suggested that CCK expression could be regulated at the level of translation. A potential role of these peptides in mediating responses to infection by larval schistosomes is discussed. 

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3. Schistosome infection in Senegal is associated with different spatial extents of risk and ecological drivers for Schistosoma haematobium and S. mansoni

   https://doi.org/10.1371/journal.pntd.0009712  

   Jones, Isabel J.; Sokolow, Susanne H.; Chamberlin, Andrew J.; Lund, Andrea J.; Jouanard, Nicolas; Bandagny, Lydie; Ndione, Raphaël; Senghor, Simon; Schacht, Anne-Marie; Riveau, Gilles; et al (September 2021, PLOS Neglected Tropical Diseases)

   Secor, W. Evan (Ed.)

   Schistosome parasites infect more than 200 million people annually, mostly in sub-Saharan Africa, where people may be co-infected with more than one species of the parasite. Infection risk for any single species is determined, in part, by the distribution of its obligate intermediate host snail. As the World Health Organization reprioritizes snail control to reduce the global burden of schistosomiasis, there is renewed importance in knowing when and where to target those efforts, which could vary by schistosome species. This study estimates factors associated with schistosomiasis risk in 16 villages located in the Senegal River Basin, a region hyperendemic for Schistosoma haematobium and S . mansoni . We first analyzed the spatial distributions of the two schistosomes’ intermediate host snails ( Bulinus spp. and Biomphalaria pfeifferi , respectively) at village water access sites. Then, we separately evaluated the relationships between human S . haematobium and S . mansoni infections and (i) the area of remotely-sensed snail habitat across spatial extents ranging from 1 to 120 m from shorelines, and (ii) water access site size and shape characteristics. We compared the influence of snail habitat across spatial extents because, while snail sampling is traditionally done near shorelines, we hypothesized that snails further from shore also contribute to infection risk. We found that, controlling for demographic variables, human risk for S . haematobium infection was positively correlated with snail habitat when snail habitat was measured over a much greater radius from shore (45 m to 120 m) than usual. S . haematobium risk was also associated with large, open water access sites. However, S . mansoni infection risk was associated with small, sheltered water access sites, and was not positively correlated with snail habitat at any spatial sampling radius. Our findings highlight the need to consider different ecological and environmental factors driving the transmission of each schistosome species in co-endemic landscapes. 

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4. Interventions can shift the thermal optimum for parasitic disease transmission

   https://doi.org/10.1073/pnas.2017537118  

   Nguyen, Karena H.; Boersch-Supan, Philipp H.; Hartman, Rachel B.; Mendiola, Sandra Y.; Harwood, Valerie J.; Civitello, David J.; Rohr, Jason R. (March 2021, Proceedings of the National Academy of Sciences)

   Temperature constrains the transmission of many pathogens. Interventions that target temperature-sensitive life stages, such as vector control measures that kill intermediate hosts, could shift the thermal optimum of transmission, thereby altering seasonal disease dynamics and rendering interventions less effective at certain times of the year and with global climate change. To test these hypotheses, we integrated an epidemiological model of schistosomiasis with empirically determined temperature-dependent traits of the human parasiteSchistosoma mansoniand its intermediate snail host (Biomphalariaspp.). We show that transmission risk peaks at 21.7 °C (T_opt), and simulated interventions targeting snails and free-living parasite larvae increasedT_optby up to 1.3 °C because intervention-related mortality overrode thermal constraints on transmission. ThisT_optshift suggests that snail control is more effective at lower temperatures, and global climate change will increase schistosomiasis risk in regions that move closer toT_opt. Considering regional transmission phenologies and timing of interventions when local conditions approachT_optwill maximize human health outcomes. 

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5. Identification of Snails and Schistosoma of Medical Importance via Convolutional Neural Networks: A Proof-of-Concept Application for Human Schistosomiasis

   https://doi.org/10.3389/fpubh.2021.642895  

   Tallam, Krti; Liu, Zac Yung-Chun; Chamberlin, Andrew J.; Jones, Isabel J.; Shome, Pretom; Riveau, Gilles; Ndione, Raphael A.; Bandagny, Lydie; Jouanard, Nicolas; Eck, Paul Van; et al (July 2021, Frontiers in Public Health)

   null (Ed.)

   In recent decades, computer vision has proven remarkably effective in addressing diverse issues in public health, from determining the diagnosis, prognosis, and treatment of diseases in humans to predicting infectious disease outbreaks. Here, we investigate whether convolutional neural networks (CNNs) can also demonstrate effectiveness in classifying the environmental stages of parasites of public health importance and their invertebrate hosts. We used schistosomiasis as a reference model. Schistosomiasis is a debilitating parasitic disease transmitted to humans via snail intermediate hosts. The parasite affects more than 200 million people in tropical and subtropical regions. We trained our CNN, a feed-forward neural network, on a limited dataset of 5,500 images of snails and 5,100 images of cercariae obtained from schistosomiasis transmission sites in the Senegal River Basin, a region in western Africa that is hyper-endemic for the disease. The image set included both images of two snail genera that are relevant to schistosomiasis transmission – that is, Bulinus spp. and Biomphalaria pfeifferi – as well as snail images that are non-component hosts for human schistosomiasis. Cercariae shed from Bi. pfeifferi and Bulinus spp. snails were classified into 11 categories, of which only two, S. haematobium and S. mansoni , are major etiological agents of human schistosomiasis. The algorithms, trained on 80% of the snail and parasite dataset, achieved 99% and 91% accuracy for snail and parasite classification, respectively, when used on the hold-out validation dataset – a performance comparable to that of experienced parasitologists. The promising results of this proof-of-concept study suggests that this CNN model, and potentially similar replicable models, have the potential to support the classification of snails and parasite of medical importance. In remote field settings where machine learning algorithms can be deployed on cost-effective and widely used mobile devices, such as smartphones, these models can be a valuable complement to laboratory identification by trained technicians. Future efforts must be dedicated to increasing dataset sizes for model training and validation, as well as testing these algorithms in diverse transmission settings and geographies. 

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