Dr. Chester Kalinda

One of the most deadly neglected tropical diseases known to man is schistosomiasis. Understanding how the disease spreads and evaluating the relevant control strategies are key steps in predicting its spread. We propose a mathematical model to evaluate the potential impact of four strategies: chemotherapy, awareness programs, the mechanical removal of snails and molluscicides, and the impact of a change in temperature on different molluscicide performances based on their half-lives and the length of time they persist in contact with target species. The results show that the recruitment rate of humans and the presence of cercaria and miracidia parasites are crucial factors in disease transmission. However, schistosomiasis can be entirely eradicated by combining all of the four strategies. In the face of climate change and molluscicide degradation, the results show that increasing the temperatures and the number of days a molluscicide persists in the environment before it completely degrades decreases the chemically induced mortality rate of snails while increasing the half-life of different molluscicides increases the death rate of snails. Therefore, eradicating schistosomiasis effectively necessitates a comprehensive integration of all preventative measures. Moreover, regions with different weather patterns and seasonal climates need strategies that have been adapted in terms of the appropriate molluscicide and time intervals for reapplication and effective schistosomiasis control.

Lake Kivu is one of the great lakes in the western branch of the East African Rift System and it is infamous as a dangerous “explosive” lake because of its limnological peculiarities and history of lacustrine volcanic eruptions (Jones, 2021). The lake hosts very substantial fisheries and other natural resources that support the livelihoods of millions of people in the two riparian countries, the Democratic Republic of Congo (DRC) and Republic of Rwanda (Rwanda) (Amisi et al., 2022). Lake Kivu is ancient, as it has existed since the middle Pleistocene, when it formed by uplift of the Virunga Mountains to the north (Degens et al., 1973). Previously, Lake Kivu drained to the north into Lake Edward. However, ∼20,000 years ago, volcanic eruptions and resulting lava flows in the Virunga Volcanic Province (VVP) impounded this outlet (Hecky and Degens, 1973, Ross et al., 2014). This barrier led to a lake level rise and a new outlet, the Ruzizi River, was formed in the South which drains to Lake Tanganyika (Degens et al., 1973, Ross et al., 2014). Since its formation, Lake Kivu has been heavily influenced by volcanic activity, particularly that within the VVP (e.g. Smets et al., 2010, d’Oreye et al., 2011, Ross et al., 2014). Lava flows from Nyiragongo and Nyamulagira, the two active volcanoes located north of Lake Kivu in the Virunga Mountains, have repeatedly entered Kabuno Bay and the main basin of Lake Kivu, particularly during the 1938–40 Nyamulagira and 2002 Nyiragongo eruptions (Balagizi et al., 2018). Beyond volcanic eruptions, Lake Kivu is exposed to earthquakes and degassing events, which may result in limnic overturns (Balagizi et al., 2018). The methane reservoir in Lake Kivu is a valuable energy resource for neighboring Rwanda and DRC, but also a looming threat to millions of people in the surrounding area if the stability of the lake is disrupted and the gasses are released into the atmosphere. Several researchers have suggested that methane gas exploitation could reduce the risks of dangerous limnetic eruptions due to supersaturation or subaqueous volcanic eruption (Balagizi et al., 2018, Ross et al., 2014, Schmid et al., 2021, Schmid et al., 2005).

Schistosomiasis, a neglected tropical disease caused by parasitic worms, poses a major public health challenge in economically disadvantaged regions, especially in Sub-Saharan Africa. Climate factors, such as temperature and rainfall patterns, play a crucial role in the transmission dynamics of the disease. This study presents a deterministic model that aims to evaluate the temporal and seasonal transmission dynamics of schistosomiasis by examining the influence of temperature and rainfall over time. Equilibrium states are examined to ascertain their existence and stability employing the center manifold theory, while the basic reproduction number is calculated using the next-generation technique. To validate the model's applicability, demographic and climatological data from Uganda, Kenya, and Tanzania, which are endemic East African countries situated in the tropical region, are utilized as a case study region. The findings of this study provide evidence that the transmission of schistosomiasis in human populations is significantly influenced by seasonal and monthly variations, with incidence rates varying across countries depending on the frequency of temperature and rainfall. Consequently, the region is marked by both schistosomiasis emergencies and re-emergences. Specifically, it is observed that monthly mean temperatures within the range of 22e27 C create favorable conditions for the development of schistosomiasis and have a positive impact on the reproduction numbers. On the other hand, monthly maximum temperatures ranging from 27 to 33 C have an adverse effect on transmission. Furthermore, through sensitivity analysis, it is projected that by the year 2050, factors such as the recruitment rate of snails, the presence of parasite egg-containing stools, and the rate of miracidia shedding per parasite egg will contribute significantly to the occurrence and control of schistosomiasis infections. This study highlights the significant influence of seasonal and monthly variations, driven by temperature and rainfall patterns, on the transmission dynamics of schistosomiasis. These findings underscore the importance of considering climate factors in the control and prevention strategies of schistosomiasis. Additionally, the projected impact of various factors on schistosomiasis infections by 2050 emphasizes the need for proactive measures to mitigate the disease's impact on vulnerable populations. Overall, this research provides valuable insights to anticipate future challenges and devise adaptive measures to address schistosomiasis transmission patterns.