Last summer, reports emerged that a massive outbreak of anthrax was affecting reindeer populations in Russia’s once-frozen Siberian tundra, infecting thousands of animals as well as several dozen of the region’s nomadic herders—including the death of one child. A record heatwave swept across the region, resulting in widespread melting of permafrost that uncovered a reindeer carcass—believed to be the source of the outbreak. Russian officials have initiated a campaign aimed at administering mass immunization to the entire 800,000 strong regional reindeer population and their herders and are conducting extensive environmental decontamination efforts to remediate the affected feeding grounds.
Bacillus anthracis, the causative bacterium for anthrax disease, is not a particularly hardy bacterium; however, when faced with inhospitable environmental conditions, it can form spores that are capable of surviving for decades and then reactivating—and once again becoming infectious—when presented with more favorable conditions (eg, in a human or animal body). In the case of the Russian reindeer, it is believed a reindeer that died of anthrax more than 70 years ago thawed during the heatwave, allowing B. anthracis spores to spread across the tundra. The reindeer likely became infected when they ingested contaminated grass.
In late 2016, Russian officials announced that they intended to cull more than 250,000 reindeer—before Christmas, no less—in order to stop the spread of infection. They ultimately culled 100,000 reindeer, despite calls from scientists to double that number. Anthrax is not, in and of itself, directly communicable, but B. anthracis spores caught in animal fur can infect other animals and humans if inhaled, ingested, or if they come into contact with open wounds. Humans can also be infected by ingesting the meat of sick animals or contaminated water, and they are commonly exposed to B. anthracis through handling hair or hides from infected animals. Similar to human outbreaks, densely populated animal populations provide conditions conducive to the rapid spread of communicable diseases, and officials ordered the culling over concerns that the region was overpopulated.
This outbreak arose from the nexus of two prominent themes in global health security, One Health and climate change. Humans, animals, and the environment must coexist in a symbiotic relationship, otherwise we risk causing harm to one or more of them. In this case, reindeer herds are critical to the livelihood of nomadic populations in Siberia, but officials warn that the current reindeer population exceeds the environment’s capacity to sustain them. Densely populated areas result in overfeeding, and reindeer herds, and their herders, may be forced to relocate to find new grazing areas—in this case, restricted areas with higher risk of anthrax contamination. Additionally, climate change has been widely attributed to cumulative human activity over the past several centuries, which has resulted in effects ranging from rising temperatures to more frequent and more severe natural disasters (eg, hurricanes, floods and droughts, earthquakes). Record high temperatures in Siberia resulted in the melting of permafrost, which exposed the carcass of a reindeer that led to the release of anthrax spores into the environment. This release not only affected the reindeer that grazed nearby, it also infected humans, necessitated the culling of tens of thousands of reindeer, and contaminated critical reindeer grazing areas. The loss of the contaminated areas may result in further crowding of reindeer populations and further increase the risk of disease spread in these populations.
As climate change continues, it will have profound effects on the human-animal interface around the globe. Scientists warn that melting permafrost could potentially lead to the release of other viable dangerous pathogens that have been frozen and preserved in ice, the likes of which humanity may not have faced in centuries or even millennia, if ever. Similarly, rising temperatures and increased rainfall—or hurricanes and monsoons—will increase the viable range of mosquitoes that transmit malaria, dengue, Zika, and other diseases as well as bats that carry Ebola, Hendra, and Nipah viruses. Furthermore, growing human populations will inevitably push beyond current population boundaries and infringe on animal habitats, increasing the risk for exposure and transmission of zoonotic infections. And increased demand for food and other animal products could result in further increases in the density of agricultural animal populations. These high-density animal populations will provide ideal conditions for rapid spread of animal diseases, including those with potential for zoonotic transmission—as we have already seen with sizable avian influenza outbreaks in the United States and China. The demand for animal protein can also result in humans searching for new sources of food, which can lead to exposure to animal species that may be host to a myriad of potentially zoonotic pathogens.
Considering the impact of these changes, the One Health approach is increasingly important as a means of detecting and controlling disease outbreaks. Human, animal, and environmental health and epidemiology need to work closely at all levels—local, state/regional, national, and global—to develop and implement programs to effectively conduct surveillance across animal and human populations and implement necessary interventions. Efforts like the International Health Regulations and the Global Health Security Agenda have identified the importance of multi-sectoral engagement between animal and human health, but these regimes do not fully embrace the role of environmental health. Further effort is needed to better incorporate environmental health into the One Health concept and to identify best practices and develop concrete proposals for meaningful collaboration and integration across all three sectors.
Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly in near-real time to allow others to learn from these experiences in order to improve global outbreak response capabilities.