Landscape attributes governing local transmission of an endemic zoonosis: Rabies virus in domestic dogs

Abstract

Landscape heterogeneity plays an important role in disease spread and persistence, but quantifying landscape influences and their scale dependence is challenging. Studies have focused on how environmental features or global transport networks influence pathogen invasion and spread, but their influence on local transmission dynamics that underpin the persistence of endemic diseases remains unexplored. Bayesian phylogeographic frameworks that incorporate spatial heterogeneities are promising tools for analysing linked epidemiological, environmental and genetic data. Here, we extend these methodological approaches to decipher the relative contribution and scale‐dependent effects of landscape influences on the transmission of endemic rabies virus in Serengeti district, Tanzania (area ~4,900 km2). Utilizing detailed epidemiological data and 152 complete viral genomes collected between 2004 and 2013, we show that the localized presence of dogs but not their density is the most important determinant of diffusion, implying that culling will be ineffective for rabies control. Rivers and roads acted as barriers and facilitators to viral spread, respectively, and vaccination impeded diffusion despite variable annual coverage. Notably, we found that landscape effects were scale‐dependent: rivers were barriers and roads facilitators on larger scales, whereas the distribution of dogs was important for rabies dispersal across multiple scales. This nuanced understanding of the spatial processes that underpin rabies transmission can be exploited for targeted control at the scale where it will have the greatest impact. Moreover, this research demonstrates how current phylogeographic frameworks can be adapted to improve our understanding of endemic disease dynamics at different spatial scales.

Using phylogeographic approaches to analyse the dispersal history, velocity and direction of viral lineages — Application to rabies virus spread in Iran

“…Further, the analysis of metadata associated with these Iranian clades suggests frequent RABV transmissions between dog and wildlife animal populations, and vice versa. Such a complex transmission pattern has already been identified in other regions such as Tanzania (Brunker et al, ) and in close countries such as Turkey (Horton et al, ; Marston et al, ). From an epidemiological point of view, the identification of this transmission pattern underlines the importance of the wildlife reservoir in the maintenance and circulation of the virus.…”

“…Tanzania (Brunker et al, 2018) and in close countries such as Turkey (Horton et al, 2015;Marston et al, 2017). From an epidemiological point of view, the identification of this transmission pattern underlines the importance of the wildlife reservoir in the maintenance and circulation of the virus.…”

The spread of a wild plant pathogen is driven by the road network

“…In general, a natural assumption is that the movement of pathogens and hosts and the intensity and amount of contacts between them always plays a role and should be incorporated into epidemiological analyses. For example, studies have shown the significant impact of the social network among giraffes coinciding with the patterns of direct transmission of E.coli among them [8], the global air-traffic volumes to be an important factor explaining the pandemic spread of influenza strains [9], and the road networks to explain the prevalence of measles cases in Niger [10] and the spread of rabies in Tanzanian dogs [11]. Spatial epidemiological analyses have utilized a diverse set of modeling tools, spanning from lattice, diffusion and metapopulation models to network models [12].…”

A systemic approach to assess the potential and risks of wildlife culling for infectious disease control

“…Numerous methods, models, and tools have been developed by ecologists to estimate population density or abundance by taking into account observation probability and its variation according to factors, such as time of day or season 132 rabies diffusion, and not their density. This implies that culling is ineffective for rabies control 67 .…”