No abstract

Since chronic wasting disease (CWD) was first identified nearly 50 years ago in a captive mule deer herd in the Rocky Mountains of the United States, it has slowly spread across North America through the natural and anthropogenic movement of cervids and their carcasses. As the endemic areas have expanded, so has the need for rapid, sensitive, and cost effective diagnostic tests -especially those which take advantage of samples collected antemortem. Over the past two decades, strategies have evolved from the recognition of microscopic spongiform pathology and associated immunohistochemical staining of the misfolded prion protein to enzyme-linked immunoassays capable of detecting the abnormal prion conformer in postmortem samples. In a history that parallels the diagnosis of more conventional infectious agents, both qualitative and real-time amplification assays have recently been developed to detect minute quantities of misfolded prions in a range of biological and environmental samples. With these more sensitive and semi-quantitative approaches has come a greater understanding of the pathogenesis and epidemiology of this disease in the native host. Because the molecular pathogenesis of prion Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted:

20 21 22 higher diversity with regard to indigenous combined with exotic breeds led to reduced numbers of infected 40 cattle compared to more homogenous cattle populations. 41 42 Rift Valley fever (RVF) is a zoonotic mosquito-borne disease caused by Rift Valley fever virus (RVFV;43 Phlebovirus: Bunyaviridae) that severely affects ungulate livestock and wildlife but can also affect humans in 44 RVF-endemic regions of sub-Saharan Africa and parts of the Arabian Peninsula [1,2]. The potential extreme 45 economic, and public and veterinary health burdens of epizootics/epidemics of RVF have been described 46 extensively [3]. Heavy rainfall and flooding are the most prominent precursors of RVF epizootics in savanna mosquitoes during blood feeding [2,4,5]. However, areas outside the recognized RVF epizootic regions, 50 especially in central Africa, may not experience transmissions linked to elevated rainfall [6]. In these areas, 51RVFV is most likely spread via movements of infected livestock from endemic areas with elevated rainfall: 52 livestock trading across different market areas may include infectious cattle that could disperse the virus and, 53 in the presence of suitable mosquito vectors, accelerate and expand the transmission of RVFV, especially when 54 cattle operations are distributed across large distances but linked by trade [7]. Patterns of recent RVF activity in 55 Uganda first described on 9 March 2016 support this hypothesis of RVFV spread linked to the cattle trade [8] 56 and underscore the need to develop effective operational surveillance and mitigation strategies to reduce 57 transmission and prevent spread among cattle operations. In this study we designed a network-based epidemic 58 transmission model to run simulations to quantitatively investigate the patterns of spread of RVFV across cattle 59 operations in Kabale District, Uganda, providing an opportunity to thus quantitatively investigate the potential 60 impact of various mitigation methods. 61 Scoglio et al. [9] recently published an individual-level RVF epidemic transmission model for cattle in Riley 62 County, Kansas, USA, structured on the susceptible-exposed-infected-recovered (SEIR) framework applied to 63 a cattle movement network. They used two separate kernel functions -exponential and power-law models -to 64 model cattle movement between and among farms in Riley County. Simulations with these kernel functions 65 revealed that more widespread epizootics resulted from the power law model, most likely because cattle were 66 allowed to move to distant farms. In contrast, the exponential model greatly restricted cattle movement to more 67 proximal farms, reducing spread of the virus. The message from the Scoglio et al. study is that restricting cattle 68 movement substantially reduces RVFV transmission and spread across the landscape of cattle operations. 69 Secondarily, they found that partitioning each farm into several clusters also results in less widespread RVF 70 epizootics. 71 In the present study, we built upon the Scoglio et al...