Insight into what Peru's second-largest city may be missing in its efforts to track rabies could provide insight to the rest of the world on a disease that still kills 70,000 people per year. A team led by researchers from the Perelman School of Medicine at the University of Pennsylvania found that efforts to track dog-related rabies in poorer areas were lacking even though more dogs were found to have the disease there than in wealthier neighborhoods.
"The people most at risk were also the least 'seen' by the surveillance system for this," said Ricardo Castillo, PhD, DVM, MSPH, an assistant professor of Epidemiology, senior author of a new report in The Lancet Regional Health - Americas.
Castillo hopes that the work he and his colleagues have done will help promote better methods for control over rabies and animal-borne diseases, overall, and prompt public health officials to evaluate their methods for equity.
Tracking rabies in canines once again
Rabies in dogs was eradicated from Peru for many years but has recently re-emerged, which is a significant concern for the people living there: Dogs cause 99 percent of recorded rabies cases worldwide. So, tracking cases in them is vital to prevent outbreaks of the disease among humans.
In Arequipa, Peru, where the researchers based their study, surveillance of rabies is largely tied to a "passive" strategy that relies on people to report dead dogs they see to local health facilities for sample collection and testing. However, that passive system can be a particular problem disadvantaged neighborhoods.
"These areas often lack nearby facilities and residents may have informal jobs, limited time, and less awareness of rabies," Castillo explained. "There are also fewer veterinary and public health personnel in these areas. So, there are structural barriers and geographic inequity. When dog rabies re-emerged, I realized that it was these social and spatial differences that allowed rabies to persist."
Knowing this, Castillo and his team set up an "active" surveillance system that began in 2021 in partnership with Cayetano Heredia University in Lima, Peru. This system used regular patrols of dry water channels in Arequipa (areas where dog bodies are often found) to supplement the passive reporting system. The study showed that in 2021 and 2022, the active system accounted for about a third of all samples collected.
Zeroing in on the right spots
To assess whether surveillance efforts were actually focused on the right spots, the researchers evaluated data from 2015 through 2022. They tracked where samples were taken from, assigning them to the blocks they were closest to.
At the same time, they calculated a block's socioeconomic status by assessing the estimated average household incomes, then assigning them a letter from A to E. Blocks with A status were considered to have the highest socioeconomic, with E being the lowest.
They found that samples from the D and E level blocks accounted for 67 and 58 percent of the total samples taken via passive surveillance in 2021 and 2022, respectively. However, when it came to active surveillance, which looked for samples in the likeliest areas, 81 percent and 78 percent of the samples came from these areas in 2021 and 2022, respectively.
"We were finding striking differences between risk and surveillance, and it seems clearly tied to equitable use and access to resources," Castillo said.
Worldwide application
While the research was based in one city in Peru, its lessons are far-reaching. Rabies remains a significant concern in wide swaths of the world, including the Carribean, Africa, and Asia.
Federal funding from the United States was key here in forming the surveillance system the study team employed and its collection and analysis of data. The United States is not immune to potential rabies outbreaks: Castillo related that raccoons in the Northeast, skunks in the South, and bats across the country all are at significant risk for rabies. And American cities share some real similarities with Arequipa—featuring block-by-block inequities and some neglected animal populations.
"Learning from endemic settings like Peru can inform preparedness and elimination strategies in the United States and worldwide, especially as climate and migration alter the dynamics of infectious diseases in animals—and how they transfer to humans," Castillo said. "Ultimately, rabies control is a shared health challenge: If it persists in one place, it remains a risk everywhere."
This study was supported by the National Institute of Allergy and Infectious Diseases (grant numbers K01AI139284 and R01AI168291) and the National Institutes of Health-Fogarty International Center (D43TW012741).
