Seasonal temperature fluctuation and snail adaptive behaviors yield insights into the dynamics and distribution of schistosomiasis in Africa

Research Square · 2025-03-26

Vertical climate velocity adds a critical dimension to species shifts

Nature Climate Change · 2025-05-21 · 4 citations

Commercial fishing influences the life histories of fish in the world's largest desert lake

Journal of Fish Biology · 2025-06-26 · 1 citations

Abstract Lake Turkana, the world's largest permanent desert lake, is an important source of fish for both local consumption and international trade. The growth of Lake Turkana's commercial fishery has increased the risk of overexploiting the lake's fish stocks. Selection pressure from overexploitation of fish stocks often drives shifts in fish life‐history traits, including mean length ( L mean ), maximum length ( L max ) and size at maturity ( L mat ). To assess the life‐history indicators of overexploitation in Lake Turkana, we compared the life‐history traits of six of Lake Turkana's major commercial fish species from three time periods (1930–1953, 1972–1975, 2010–2022) that represent distinct levels of fishing pressure. These focal species were the African butter catfish Schilbe uranoscopus Rüppell 1832, the elongate tigerfish Hydrocynus forskahlii (Cuvier 1819), Nile perch Lates niloticus (L. 1758), Nile tilapia Oreochromis niloticus (L. 1758), silversides Alestes baremose (Joannis 1835) and wahrindi Synodontis schall (Bloch and Schneider 1801). Heavily exploited species exhibited notable decreases in L mat as fishing pressure increased, and include A. baremose (29.7% decrease), H. forskahlii (16.4% decrease), L . niloticus (56.1% decrease) and O . niloticus (45.3% decrease). In contrast, lightly exploited species, including S. uranoscopus and S. schall , did not exhibit large declines in life‐history traits. Additionally, we used current catch length frequency data for L. niloticus to infer that L. niloticus are currently experiencing overfishing and exhibit signs of the depletion of large ‘mega‐spawners’. These results suggest that heavy commercial fishing likely drives the observed life‐history responses. We suggest that the management of sustainable fisheries in Lake Turkana should focus on gear size restrictions as well as on reducing fishing effort on commercial‐sized fish to decrease the probability of overfishing and potential declines of stocks.

Application of Causal Discovery of Factors Driving Dissolved Oxygen in Estuarine Environments

Journal of Environmental Sciences · 2025-11-01

LAKE TURKANA’S FISHERIES: NEW INSIGHTS FROM A CENTURY OF LIMNOLOGICAL RESEARCH

Abstracts with programs - Geological Society of America · 2024-01-01

Climate and urbanization drive changes in the habitat suitability of Schistosoma mansoni competent snails in Brazil

Nature Communications · 2024-06-19 · 19 citations

Schistosomiasis is a neglected tropical disease caused by Schistosoma parasites. Schistosoma are obligate parasites of freshwater Biomphalaria and Bulinus snails, thus controlling snail populations is critical to reducing transmission risk. As snails are sensitive to environmental conditions, we expect their distribution is significantly impacted by global change. Here, we used machine learning, remote sensing, and 30 years of snail occurrence records to map the historical and current distribution of forward-transmitting Biomphalaria hosts throughout Brazil. We identified key features influencing the distribution of suitable habitat and determined how Biomphalaria habitat has changed with climate and urbanization over the last three decades. Our models show that climate change has driven broad shifts in snail host range, whereas expansion of urban and peri-urban areas has driven localized increases in habitat suitability. Elucidating change in Biomphalaria distribution-while accounting for non-linearities that are difficult to detect from local case studies-can help inform schistosomiasis control strategies.

Climate and urbanization drive changes in the habitat suitability of <i>Schistosoma mansoni</i> competent snails in Brazil

bioRxiv (Cold Spring Harbor Laboratory) · 2024-01-04 · 1 citations

ABSTRACT Schistosomiasis is a neglected tropical disease caused by Schistosoma parasites. Schistosoma are obligate parasites of freshwater Biomphalaria snails, so controlling snail populations is critical to reducing transmission risk. As snails are sensitive to environmental conditions, we expect their distribution is significantly impacted by global change. Here, we leveraged machine learning, remote sensing, and 30 years of snail occurrence records to map the historical and current distribution of competent Biomphalaria throughout Brazil. We identified key features influencing the distribution of suitable habitat and determined how Biomphalaria habitat has changed with climate and urbanization over the last three decades. Our models show that climate change has driven broad shifts in snail host range, whereas expansion of urban and peri-urban areas has driven localized increases in habitat suitability. Elucidating change in Biomphalaria distribution – while accounting for non-linearities that are difficult to detect from local case studies – can help inform schistosomiasis control strategies.

Re-assessing thermal response of schistosomiasis transmission risk: evidence for a higher thermal optimum than previously predicted

medRxiv · 2024-01-07

Abstract The geographical range of schistosomiasis is affected by the ecology of schistosome parasites and their obligate host snails, including their response to temperature. Previous models predicted schistosomiasis’ thermal optimum at 21.7 °C, which is not compatible with the temperature in sub-Saharan Africa (SSA) regions where schistosomiasis is hyperendemic. We performed an extensive literature search for empirical data on the effect of temperature on physiological and epidemiological parameters regulating the free-living stages of S. mansoni and S. haematobium and their obligate host snails, i.e., Biomphalaria spp. and Bulinus spp., respectively. We derived nonlinear thermal responses fitted on these data to parameterize a mechanistic, process-based model of schistosomiasis. We then re-cast the basic reproduction number and the prevalence of schistosome infection as functions of temperature. We found that the thermal optima for transmission of S. mansoni and S. haematobium range between 23.1-27.3 °C and 23.6-27.9 °C (95 % CI) respectively. We also found that the thermal optimum shifts toward higher temperatures as the human water contact rate increases with temperature. Our findings align with an extensive dataset of schistosomiasis prevalence in SSA. The refined nonlinear thermal-response model developed here suggests a more suitable current climate and a greater risk of increased transmission with future warming for more than half of the schistosomiasis suitable regions with mean annual temperature below the thermal optimum. Authors’ summary In this research, we explored the complex interplay between temperature and the transmission risk of schistosomiasis, a parasitic disease currently affecting over two hundred million people, predominantly in SSA. We developed a novel mathematical model accounting for the multiple positive and negative ways temperature affects the free-living stages of the parasite and its obligate, non-human host, i.e., specific species of freshwater snails. Our models show that schistosomiasis transmission risk peaks at temperatures 1-6°C higher than previously estimated. This indicates that the impact of climate change on schistosomiasis transmission might be more extensive than previously thought, affecting a wide geographic range where mean annual temperatures are currently below the optimal temperature. Our model projections are consistent with the observed temperatures in locations of SSA where schistosomiasis is endemic and data on infection prevalence in the human population are available. These findings suggest that the current climate is conducive to schistosomiasis transmission, and future warming could escalate the risk further, emphasizing the need for targeted interventions in these regions.

Re-assessing thermal response of schistosomiasis transmission risk: Evidence for a higher thermal optimum than previously predicted

PLoS neglected tropical diseases · 2024-06-10 · 7 citations

The geographical range of schistosomiasis is affected by the ecology of schistosome parasites and their obligate host snails, including their response to temperature. Previous models predicted schistosomiasis' thermal optimum at 21.7°C, which is not compatible with the temperature in sub-Saharan Africa (SSA) regions where schistosomiasis is hyperendemic. We performed an extensive literature search for empirical data on the effect of temperature on physiological and epidemiological parameters regulating the free-living stages of S. mansoni and S. haematobium and their obligate host snails, i.e., Biomphalaria spp. and Bulinus spp., respectively. We derived nonlinear thermal responses fitted on these data to parameterize a mechanistic, process-based model of schistosomiasis. We then re-cast the basic reproduction number and the prevalence of schistosome infection as functions of temperature. We found that the thermal optima for transmission of S. mansoni and S. haematobium range between 23.1-27.3°C and 23.6-27.9°C (95% CI) respectively. We also found that the thermal optimum shifts toward higher temperatures as the human water contact rate increases with temperature. Our findings align with an extensive dataset of schistosomiasis prevalence in SSA. The refined nonlinear thermal-response model developed here suggests a more suitable current climate and a greater risk of increased transmission with future warming for more than half of the schistosomiasis suitable regions with mean annual temperature below the thermal optimum.

Behavioral and physiological effects of ocean acidification and warming on larvae of a continental shelf bivalve

Marine Pollution Bulletin · 2023 · 18 citations

• Oceanography
• Environmental science
• Ecology