According to a new study, the mobility and behavior of each rabid dog helps to ensure that the dispersal and circulation of the rabies virus persists despite low virus prevalence. The findings, based on tracing the deadly disease in a population of more than 50,000 dogs over more than a decade, offer new insight into the processes that regulate endemic disease dynamics and the mechanisms that allow pathogens to persist. in populations at low levels.
Most often transmitted to humans by dogs, rabies is a deadly zoonotic virus responsible for tens of thousands of deaths each year, particularly in low- and middle-income countries and affecting mostly children. However, despite its very low rate of transmission and despite control efforts, including the culling of dog populations and vaccination programs, canine rabies remains endemic in Africa and Asia. How the virus persists at such a low prevalence — even in largely unvaccinated dog populations — remains a mystery.
To understand the dynamics of the virus, Rebecca Mancy and her colleagues tracked rabies transmissions, population densities, disease incidence and vaccination campaigns in a large population of domestic dogs in Serengeti, Tanzania, from 2002 to 2016. They used the spatially detailed data to model the scale and dynamics of rabies transmission.
According to the results, the processes underlying the persistence and prevalence of rabies operate at much smaller scales than those typically modeled for the disease. Mancy et al. found that individual dog behavior was a key factor in modulating virus persistence. Although the prevalence of rabies has never exceeded 0.15%, some infected dogs act as super spreaders and travel long distances, introducing new strains of rabies to neighboring communities and triggering new local epidemics. Additionally, some infected dogs bite other dogs more often, spreading the virus more widely before dying. The authors suggest that these mechanisms probably also operate in other pathogens that circulate in spatially structured populations.
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Rabies shows how the scale of transmission can allow acute infections to persist at low prevalence