The report for the month of January of this year from the United States National Wildlife Health Center on zombie deer disease is not encouraging at all. Technically known as chronic wasting disease (CWD) has already been detected in wild cervids (deer, elk, reindeer and similar) in 32 states of the United States and four provinces of Canada. This relationship includes cases of animals living in captivity in 18 US states and three Canadian provinces.
The authorities have not provided a balance of victims but, based on the data released so far, it is estimated that all the animals affected by this transmissible spongiform encephalopathy (similar to bovine spongiform encephalopathy, known as mad cow disease) have died after a process of brain degeneration of which at the moment there is very little scientific knowledge and no treatment.
The expansion of CWD in Texas, where 90 dead cervids were recorded in November 2023, is an example of the complexity in studying and fighting this rare infection.
On November 20, they killed all of the herd’s approximately 90 deer, depopulating the Texas Parks and Wildlife Department’s only deer research center.
One of the unknowns is how an infectious disease, which causes the death of infected animals, can continue to spread to areas far from the sources of infection. Furthermore, since these are infections in wild animals, surveillance is much more complex and it is not ruled out that animals may spread the disease for many years before showing symptoms.
In the case of Texas, the disease first appeared in free-ranging deer in 2012, near the western border with New Mexico. Cases increased slowly in the following years, concentrating mainly in the original area and the peninsula. In both regions, the disease likely spread from free-ranging deer in neighboring states.
The number of cases has grown significantly in this state since 2021, when the disease appeared in two different breeding areas. Until now, experts have not been able to clearly determine how the disease progresses and do not rule out that birds that feed on carrion, such as vultures, may collect remains of dead animals with prions (the agent that causes the disease) and involuntarily transport them to other areas, where they would come into contact – through water or vegetation – with other deer.
It has not been proven, at the moment, that CWD can infect humans, but in 2018 a first study was published indicating that this possibility cannot be ruled out. For the moment, and with a history such as mad cow disease, authorities in the United States and Canada have disseminated advice to prevent infections from game meat.