New Research Confirms in Utero CWD Transmission in Deer

By Scout Nelson

A recent study has confirmed that chronic wasting disease (CWD), a fatal prion disease in deer and elk, can be transmitted from does to their fawns during pregnancy. This discovery, published in Scientific Reports, marks the first clear evidence of in utero CWD transmission in free-ranging white-tailed deer.

Researchers from Colorado State University and collaborators examined reproductive tissues and fetal samples from naturally infected deer. They used highly sensitive tests, including real-time quaking induced conversion (RT-QuIC) and bioassays with transgenic mice, to confirm the presence of infectious prions. In total, 31% of CWD-positive did carry fetuses with prion deposition, and all mice inoculated with infected tissues developed disease symptoms.

The findings suggest that vertical transmission adds to previously known routes, such as saliva, blood, and environmental contamination. "We know that during gestation, lesions occur between the maternal and fetal interface, and that these lesions become blood filled," said Senior author Dr. Candace Mathiason. "And so, we also know that fetal-derived trophoblast cells are phagocytic [they can consume foreign particles, dead cells, or debris] and can transport themselves across the maternal-fetal interface."

Historical surveillance data from Arkansas, Tennessee, and West Virginia also revealed infected fawns younger than one year. Experts say this indicates earlier exposure than current testing methods typically detect. Traditionally, fawns under six months are excluded from surveillance because standard assays often fail to detect infections so early.

Wildlife biologists caution that while laboratory evidence is strong, impacts in the field may be harder to measure. Some argue that vertical transmission may not significantly alter management strategies unless it proves to cause higher fawn mortality. Others believe it raises important concerns about hidden disease spread, particularly as fawns establish new ranges and interact with other deer.

The study highlights potential gaps in current monitoring systems and raises questions about testing policies for both wild and farmed deer herds. Experts suggest expanded surveillance of fawns in hunter harvests could help identify infections earlier and strengthen disease control.

Photo Credit: pexels-jim-fawns