Indigenous harvesters detect climate-sensitive emerging disease in barren-ground caribou (Rangifer tarandus) threatening food security

We report a filarioid nematode outbreak in barren-ground caribou ( Rangifer tarandus ) from the Canadian Arctic that was identified by Inuit harvesters through a community-based surveillance program. Harvesters reported discolouration of tissues and presence of yellowish fluid across peritoneal and pleural surfaces, within subcutaneous tissues, and along fascial planes between muscles. Histopathology identified eosinophilic inflammation and occasionally nematode parasites. We identified DNA of Setaria yehi and Onchocerca sp. lineage 2 in submitted lesions. These are two filarioid nematode species that have been circulating in caribou since before 2015, but have only recently caused these emerging syndromes. These outbreaks raise concerns regarding the health and conservation of already-declining populations of caribou, an ecological and cultural keystone species in the Arctic, and regarding food safety for Indigenous Peoples. The emergence of clinical disease associated with these parasites may be linked to climate change, which is altering vector ecology and host susceptibility in the Arctic. Continued surveillance, led by and meeting the needs of Indigenous communities, is recommended to support food security, public health and caribou conservation. The solidity and trust underlying the surveillance program enabled rapid detection and management of the outbreak.