Informing One Health Anthrax Surveillance and Vaccination Strategy from Spatial Analysis of Anthrax in Humans and Livestock in Ha Giang Province, Vietnam (1999–2020)

Abstract

Anthrax, caused by Bacillus anthracis, has a nearly global distribution but is understudied in Southeast Asia, including Vietnam. Here, we used historical data from 1999 to 2020 in Ha Giang, a province in northern Vietnam. The objectives were to describe the spatiotemporal patterns and epidemiology of human and livestock anthrax in the province and compare livestock vaccine coverage with human and livestock anthrax incidence. Annual incidence rates (per 10,000) for humans, buffalo/cattle, and goats were used to explore anthrax patterns and for comparison with livestock annual vaccine variations. A data subset describes anthrax epidemiology in humans by gender, age, source of infection, type of anthrax, admission site, and season. Zonal statistics and SaTScan were used to identify spatial and space-time clusters of human anthrax. SaTScan revealed space-time clusters in 1999, 2004, and 2007–2008 in the province, including in the northeastern, eastern, and western areas. Most human anthrax was reported between July and October. Most patients were male, aged 15–59 years, who had handled sick animals and/or consumed contaminated meat. High case-fatality rates were reported with gastrointestinal or respiratory cases. Our data suggest that vaccination in buffalo and cattle reduces the disease burden in humans and vaccinated animals but does not reduce the incidence in unvaccinated animals (goats). This study identified spatial areas of high risk for anthrax and can inform One Health surveillance and livestock vaccination planning in contextual settings similar to Ha Giang province.

Spatial epidemiology of human anthrax in Son La province, Vietnam, 2003–2022

“…The pattern in which males predominantly got infected was not uncommon in other studies in Vietnam or globally (Luong et al, 2022(Luong et al, , 2023Migisha et al, 2021;Mwenye et al, 1996;Parlak & Parlak, 2016). Most of the cases aged from 15 to 54 years old (86.4%) with zero cases under 5 years of age.…”

“…Most of the cases aged from 15 to 54 years old (86.4%) with zero cases under 5 years of age. This result differs from other provinces in Vietnam such as Dien Bien and Ha Giang where 3.1% and 15.8% cases were under 5 years old, respectively (Luong et al, 2022(Luong et al, , 2023. Additional investigations into the cultural factors associated with the involvement of males and adults in handling sick or dead animals in Son La as well as other provinces in the region are needed.…”

“…When combined human and animal anthrax cases were available from 2003 to 2022. Here, anthrax cases were reported using criteria for Vietnam's national disease surveillance and are described in previous studies from neighbouring provinces (Luong et al., 2022, 2023). Briefly, any case with clinical signs (humans or livestock) and/or reported symptoms (humans) were defined as anthrax.…”

“…It is common that the patients in Vietnam would seek care at traditional medicines or pharmacies and visit the public health facilities only in case the infection is not healed (Ha et al, 2019). Furthermore, a vast majority of patients were reported by district hospitals, which differs from Ha Giang province where patients were mainly notified by commune health centres (Luong et al, 2023), again highlighting different contexts for anthrax across provinces. Future studies are recommended to investigate the effectiveness of involving private pharmacies in zoonosis disease surveillance and training for commune health staff in order to capture missing cases that do not seek care at district public hospitals.…”

JMM Profile: Bacillus anthracis

“…Transmission occurs principally via spores. In endemic areas, which include (for example) certain pastoral parts of southern Africa and Southeast Asia, human cases remain heavily associated with livestock or butchery [5,[37][38][39]. There remains a human risk (albeit low) in non-endemic territories from imported animal tissues [40], or occasionally from live animals [41] or accidental contamination of illegal drugs [10].…”