The mobility and behavior of individual rabid dogs helps ensure that rabies virus dispersal and circulation persist despite low virus prevalence, according to a new study. The findings, based on tracing the fatal 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 mostly affecting 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 across Africa and Asia. How the virus persists at such low prevalence – even in largely unvaccinated dog populations – remains a mystery.

To understand the virus’ dynamics, Rebecca Mancy and 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.

Findings

According to the findings, the processes that underpin the persistence and prevalence of rabies operate on scales much smaller than those typically modeled for the disease. Mancy et al. discovered that individual dog behavior was a key factor in modulating the persistence of the virus. Although rabies prevalence never exceeded 0.15%, some infected dogs act as super spreaders and travel long distances, bringing new rabies lineages into neighboring communities and starting new local outbreaks. Also, some infected dogs bite other dogs more often, spreading the virus more widely before dying. The authors suggest that these mechanisms likely also operate in other pathogens that circulate in spatially structured populations.

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Rabies shows how scale of transmission can enable acute infections to persist at low prevalence