One Health

The world is intricately and increasingly interconnected; human health often reflects environmental health. Two recent newsworthy items underscore the theme of One Health — the interdependence of human, animal, plant, and ecosystem health. Moreover, these both touched a nerve with my Wisconsin heritage and the intersectionality accross people, deer, and dairy cows — as Wisconsin is the dairy state and has a long tradition of deer hunting.

An abstract in Neurology has garnered a fair amount of attention in recent days.¹ This very brief report, pertaining to a pair of rare Creutzfeldt-Jakob disease (CJD) cases, calls attention to the possibility of prion spillover from deer with chronic wasting disease (CWD) to humans. Prions are essentially self-replicating proteins that play havoc with the brain; an abomination of protein chemistry. This abstract offers no proof of transmissibility, only an observation of the overlap of regions of CWD abundance, venison consumption, and human CJD. Experts from the CDC have opined that these cases were "part of the normal number of cases of CJD (Creutzfeldt-Jakob disease) we see in the U.S.”²  My home is just east of ground zero for CWD in Wisconsin, a disease that had rapidly spread across our white-tailed deer population. Careful consideration and detailed history-taking is of critical importance when cases of CJD are encountered. 

The CDC’s National Center on Immunization and Respiratory Diseases released an update on human infection with highly pathogenic avian influenza (HPAI).³ On April 1, 2024, a dairy worker in Texas became the first known case of cow-to-human influenza A(H5N1) transmission. This individual’s only symptom was that of conjunctivitis; no human-to-human transmission occurred. I have previously commented on the significance of HPAI’s jump into mammalian populations.⁴ This new case illustrates the tremendous potential for interspecies leaps of influenza viruses. I grew up visiting my uncles’ dairy farms. The 40-to 60-cow herds of those days are long gone, supplanted by 500- to 7000-head major dairy operations. Such concentrations of agricultural animals create enormous potential for virus transmission and amplification events. As past influenza A(H5N1) cases in humans have had overall high mortality rates (>50%), ascertainment of exposure history, again, is of paramount importance when dealing with any atypical influenza infection.

The risks for prion disease and HPAI are incredibly low for most individuals. High levels of vigilance and a One Health perspective, however, are needed for early detection of potentially big problems.