What is chronic wasting disease? What does it do? And can you catch it? These are all questions we are here to answer in our public service announcement on this strange and sometimes scary subject.
Chronic wasting disease (also called CWD) is a fatal neurodegenerative illness affecting members of the the deer family, or cervids. This family includes mule deer, white-tailed deer, elk, moose, and red deer. The disease is characterized by an infectious protein called a prion, the prions disrupt normal protein conformation, converting healthy cellular proteins into abnormal, mis-folded aggregated protein forms. Unlike conventional infectious agents, prions lack DNA or RNA, distinguishing them from other pathogens (Bartz et al., 2024).
CWD's impact extends beyond individual animals to entire ecosystems and economies. The disease poses significant threats to cervid populations, leading to increased mortality and behavioural changes. The prions responsible for CWD replicate through mechanisms that remain poorly understood and currently have no cure (Bartz et al., 2024). While CWD is invariably fatal for infected cervids, it poses a low risk to humans. Adult male deer are more frequently affected than younger individuals (Fischer et al., 2023). Infected animals, weakened by the disease, become easy prey, potentially allowing the prions to propagate through the food chain (Bhattarai et al., 2024).
Diagnostic methods for CWD include histopathological examination of tissue samples, laboratory testing of cotton swabs, and observation of clinical signs. Notable symptoms in cervids include lack of coordination, weight loss, decreased alertness, excessive drooling, head drooping, excessive drinking or urination, and difficulty swallowing. Symptoms may take two to four years to manifest (Bartz et al., 2024).
Methods for diagnosis of CWD:
1.Histopathological Examination: This involves examining cellular tissues under a microscope to identify characteristic changes associated with prion diseases.
2.Laboratory Testing: Secure cotton swab samples can be sent to laboratories for analysis, capable of detecting prions in both living and deceased animals.
3.Observation of Clinical Signs: Physical symptoms and behavioral changes can assist in indicating CWD, though these signs may take years to appear.
Environmental contamination facilitates transmission. Transmission routes include direct contact with infected animals' urine, feces, and saliva, as well as indirect environmental exposure through contaminated soil and vegetation. Ingesting contaminated soil or vegetation introduces the prions to new hosts, perpetuating environmental transmission (Bhattarai et al., 2024). This complex transmission dynamic poses a significant challenge to managing CWD spread.
Methods for transmission of CWD:
1.Direct Transmission: Occurs through contact with bodily fluids of infected animals.
2.Indirect Transmission: Occurs via environmental contamination, where prions persist in soil, open water and vegetation, infecting new hosts through ingestion.
The ecological and economic ramifications of CWD are profound. The disease destabilizes cervid populations, disrupting predator-prey dynamics and altering the balance of ecosystems. Economically, CWD affects hunting industries, wildlife management efforts, and potentially livestock farming.
Despite extensive research, much about CWD remains unknown, and no cure has been found. Collaborative efforts among scientists, hunters, and the general public offer hope for future advancements. Ongoing research focuses on understanding prion replication mechanisms, improving diagnostic methods, and developing potential treatments or preventive measures.
Chronic wasting disease is a complex and devastating condition that poses significant challenges to wildlife management and conservation efforts. Through continued research and cooperation, there is hope for mitigating the impact of this disease on cervid populations and preventing its potential spread. If you suspect you've encountered an infected animal, contact local wildlife authorities immediately.
References
Bartz, J. C., Benavente, R., Caughey, B., Christensen, S., Herbst, A., Hoover, E. A., (2024) North American Interdisciplinary Chronic Wasting Disease Research Consortium Members.. Chronic Wasting Disease: State of the Science. Pathogens, 13(2), 138.
Bhattarai, S., Grala, R. K., Poudyal, N. C., Tanger, S. M., & Adhikari, R. K. (2024). Where We Stand on Chronic Wasting Disease: A Systematic Literature Review of Its Prevalence Patterns, Impacts, and Management Interventions. Heliyon.
Fischer W. J., Phillips E. G., Nichols A. T., VerCauteren C. K., (July, 2013). Could avian scavengers translocate infectious prions to disease-free areas initiating new foci of chronic wasting disease?. https://www.tandfonline.com/doi/full/10.4161/pri.25621