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Table 1 Case study diseases, dynamics and poverty impacts and some modelling issues

From: Moving interdisciplinary science forward: integrating participatory modelling with mathematical modelling of zoonotic disease in Africa

Case study disease Key ecosystem-disease dynamics Poverty and wellbeing impacts Key modelling issues, most of which depend on human activities
Lassa fever in Sierra Leone. Lassa fever is a rodent-borne, viral haemorrhagic fever endemic in West Africa. The natural reservoir of Lassa is the ‘multimammate rat’ of the genus Mastomys. Mastomys often colonise houses, where Lassa may be transmitted to humans via contact with rodent excreta; human-to-human transmission is also possible. Changing land use and settlement patterns increasing transmission from Mastomys natalensis. Significant impacts in poor farming, peri-urban and mining settlements. High fatality rates, with pregnant women particularly vulnerable. Increasing exposure especially for poor people living in rapidly-growing crowded conditions with poorly-constructed houses. Estimates of 500,000 cases per year but significant under-diagnosis. Proportion of transmission due to human-to-human routes not fully assessed, only recently theoretical estimation provided [2]. Unclear disease dynamics in the reservoir (e.g. potential vertical transmission, role and extent of immunity). Unclear ecology of the reservoir (e.g. dispersal patterns). Route of transmission still unclear. Apparent seasonality in disease incidence but of unclear origin. Most life history and contact parameters unknown.
Henipavirus in Ghana. Henipaviruses in the family Paramyxoviridae comprise Hendra virus and Nipah virus. Pteropid bats are reservoir hosts for Nipah virus. Both Hendra and Nipah virus are zoonotic, causing encephalitic disease in humans with case fatality rates of around 75 %. The virus can spill over via infected pigs or directly from bats into people. Human-to-human transmission of the virus, with fatal consequences, has been documented. There are no pteropid bats in mainland Africa, but the closely-related straw-coloured fruit bat (Eidolon helvum) is widespread and populous and henipaviruses are maintained within this species across its geographic range. Agricultural land-use change affecting bat roosting and migration patterns; growing intensity of human interactions with bats including in urban areas. Spillover identified already between bats and pigs in Malaysia and Singapore in 1998 and 1999; particular vulnerability of smallholder pig farmers, bushmeat hunters and traders, and urban poor exposed to bat roosts. Suspected mis-reporting in humans; symptoms (high fever and encephalitis) often attributed to malaria. So far, no reported case of zoonotic spillover to humans in Ghana. Unclear disease dynamics in the reservoir. Unclear ecology of the reservoir (e.g. migratory patterns). Route of transmission still unclear. Life history and contact parameters unknown.
Rift Valley fever in Kenya. RVF has an interesting and imperfectly understood epidemiology. It is a zoonotic arbovirus affecting different species of livestock, wildlife and humans. It is transmitted mainly by different species of mosquitoes with different ecology and temporal patterns. The mosquito dynamics are driven essentially by the environmental dynamics of water bodies. Climate-driven and irrigation/standing water-driven dynamics linking wildlife, livestock and human populations in pastoral areas. Cyclical outbreaks with high impact including effects on human health, and disruption to livestock trade, with massive livelihood impact on often very poor populations. Many hosts affected by the disease with different degree of susceptibility which is only partially known. Potential existence of wildlife reservoir. Uncertainty in the role of Aedes mosquitoes in transmitting the disease to offspring. Limited information on mosquitoes feeding patterns. Lack of detailed information on irrigation patterns and water body dynamics. Unclear ecology of the mosquitoes (e.g. abundance, seasonality) and how this is affected by water abundance.
Trypanosomiasis in Zambia and Zimbabwe. Trypanosomiasis is a widely studied disease vectored by the tsetse fly. The human form of the disease is called Human African Trypanosomiasis (HAT) or sleeping sickness, while the animal form, is called Animal African Trypanosomiasis (AAT) or nagana. In west Africa T.b. Gambiense affects humans only, while in eastern and southern Africa, the zoonotic T.b. Rhodiesiense affects both humans and animals. T.b. brucei rarely affects humans. Circulates within wildlife populations via tsetse fly. Livestock can also act as a significant reservoir of disease. Interaction between humans, livestock and wildlife within ecosystems suitable for tsetse results in spillover. Massive impacts on poor farming and livestock-raising communities, including human health impact estimated by the Global Burden of Disease studies at WHO at 8721 DALYs in Africa. Huge underestimation of human and poverty impacts. Focus on trypanosomiasis in livestock, wildlife and humans. Aim to produce predictive distributions for tsetse presence/absence and for tsetse abundance within the study area. Aim to create an ABM simulation which incorporates individual agents allowing the ‘bottom-up’ modelling of a transmission network between humans, tsetse flies and animal agents over a detailed physical landscape. Areas of interest include the effects of seasonality, of changes in land cover and changes in population density.