Vertical transmission of chronic wasting disease in free-ranging white-tailed deer populations

 Published: 05 August 2025

Vertical transmission of chronic wasting disease in free-ranging white-tailed deer populations

Abstract Chronic wasting disease (CWD) is a fatal neurodegenerative disease affecting cervids across North America, Northern Europe, and Asia. Disease transmission among cervids has historically been attributed to direct animal-to-animal contact with ‘secreta’ (saliva, blood, urine, and feces) containing the infectious agent, and indirect contact with the agent shed to the environment in these bodily components. Mounting evidence provides another mechanism of CWD transmission, that from mother-to-offspring, including during pregnancy (vertical transmission). Here we describe the detection of the infectious CWD agent and prion seeding in fetal and reproductive tissues collected from healthy-appearing free-ranging white-tailed deer (Odocoileus virginianus) from multiple U.S. states by mouse bioassay and in vitro prion amplification assays. This is the first report of the infectious agent in multiple in utero derived fetal and maternal-fetal reproductive tissues, providing evidence that CWD infections are propagated within gestational fetal tissues of white-tailed deer populations. This work confirms previous experimental and field findings in several cervid species supporting vertical transmission as an additional mechanism of CWD transmission and may help to further explain the facile dissemination of this disease among captive and free-ranging cervid populations.

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We report infectious prions in the reproductive and fetal tissue of naturally exposed free-ranging white-tailed deer suggesting that in utero maternal transmission is likely an underappreciated mode of CWD transmission. Our study shows that vertical transmission is indeed a viable route of infection within the southeastern U.S. and is another potential factor contributing to the relentless spread of chronic wasting disease.

https://www.nature.com/articles/s41598-025-12727-8

14 Protein misfolding cyclic amplification (PMCA) as an ultra-sensitive technique for the screening of CWD prions in different sample types.

Francisca Bravo-Risi1,2, Paulina Soto1,2, Rebeca Benavente1, Hunter Reed3, Mitch Lockwood3, Tracy A. Nichols4, Rodrigo Morales1,5 1Department of Neurology, The University of Texas Health Science Center at Houston, Houston, USA. 2Universidad Bernardo O’Higgins, Doctorado en Ciencias con Mención en Materiales Funcionales, Santiago, Chile. 3Texas Park and Wildlife Department, Austin, USA. 4Veterinary Services Cervid Health Program, United States Department of Agriculture, Animal and Plant Health Inspection Service, Fort Collins, USA. 5Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O’Higgins, Santiago, Chile

Abstract

Chronic wasting disease (CWD) is a prion disease that affects farmed and free-ranging cervids. Currently, CWD status is ultimately confirmed in the brain and lymphoid tissues by immunohistochemistry (IHC). One limitation of IHC is its relatively poor sensitivity making it difficult to detect this disease early in the incubation period which can extend 1-3 years. Protein misfolding cyclic amplification (PMCA) and real-time quaking-induced conversion (RT-QuIC) are ultra-sensitive techniques that provide a means to detect CWD in early stages of the disease. PMCA mimics the self-propagation of infectious prions in vitro through multiple incubation-sonication cycles, increasing the number of prion particles present in a given sample. The detection of proteinase K (PK)-resistant PrPSc by PMCA has been performed in experimental and natural samples that may otherwise go undetected using traditional diagnostic techniques.

In this study, we highlight recent advances and contributions that our group has made detecting CWD-prions in animal and environmental samples collected from deer breeding and taxidermy facilities. Additionally, CWD-prions were detected in samples from hunter-harvested, free-ranging animals.

PMCA successfully detected CWD-prions in a diverse array of samples including blood, semen, feces, obex, retropharyngeal lymph node, fetuses (neural and peripheral tissues) and gestational tissues, parasites-insects, plants, compost-soil mixtures, and swabs from trash containers.

Importantly, our findings identified CWD in areas previously considered to be free of CWD. Overall, our findings demonstrate that PMCA is a powerful technique for the screening of biological and environmental samples, and it may prove useful as a CWD management and surveillance tool.

https://intcwdsympo.files.wordpress.com/2023/06/final-agenda-with-abstracts.pdf?force_download=true

RESEARCH ARTICLE

In Vitro detection of Chronic Wasting Disease (CWD) prions in semen and reproductive tissues of white tailed deer bucks (Odocoileus virginianus)

Carlos Kramm,Ruben Gomez-Gutierrez,Claudio Soto,Glenn Telling,Tracy Nichols,Rodrigo Morales Published: December 30, 2019https://doi.org/10.1371/journal.pone.0226560

Abstract

Chronic Wasting Disease (CWD) is a prion disease affecting several cervid species. Among them, white-tailed deer (WTD) are of relevance due to their value in farming and game hunting. The exact events involved in CWD transmission in captive and wild animals are still unclear. An unexplored mechanism of CWD spread involves transmissions through germplasm, such as semen. Surprisingly, the presence and load of CWD prions in semen and male sexual tissues from WTD has not been explored. Here, we described the detection of CWD prions in semen and sexual tissues of WTD bucks utilizing the Protein Misfolding Cyclic Amplification (PMCA) technology. Samples were obtained post-mortem from farmed pre-clinical, CWD positive WTD bucks possessing polymorphisms at position 96 of the PRNP gene. Our results show that overall CWD detection in these samples had a sensitivity of 59.3%, with a specificity of 97.2%. The data indicate that the presence of CWD prions in male sexual organs and fluids is prevalent in late stage, pre-clinical, CWD-infected WTD (80%-100% of the animals depending on the sample type analyzed). Our findings reveal the presence of CWD prions in semen and sexual tissues of prion infected WTD bucks. Future studies will be necessary to determine whether sexual contact and/or artificial inseminations are plausible means of CWD transmission in susceptible animal species.

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In terms of disease transmission, the presence of prions in semen begs the question on whether sexual contact is plausible route of CWD transmission. A previous report showed that semen collected from rams at pre-clinical and clinical stages of prion disease did not infect scrapie-susceptible mice [34]. Our previous results in Syrian hamsters showed that sexual exposure of naïve females to 263K infected males was ineffective in transmitting disease [35]. Maternal transmission has also be presented as a viable mode of CWD transmission to offspring. Evidence derived from scrapie-infected sheep and experimentally infected muntjac deer provides direct evidence that offspring from infected dams and ewes are at higher risk of developing prion disease [16,36]. Considering the results presented in this article, the risk of CWD transmission via semen cannot be dismiss without further inquiry. It is important to note that some semen samples tested in the current report showed PrPSc presence after only one PMCA round, suggesting that PrPSc content in semen of some animals may be relatively high. This is particularly relevant considering that tissues from male sexual organs inhibited PMCA performance. It remains unclear if vaginal exposure to CWD prions in semen is an effective route of transmission.

In summary, our results confirm the presence of CWD prions in semen and male sexual tissues in CWD-infected WTD. Future experiments in actual deer will determine whether CWD can be transmitted by breeding practices including sexual contacts or artificial inseminations. Infectivity studies in transgenic mice underway in our laboratory will determine the infectivity titers of some of the samples described in this study.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0226560

VETERINARY RESEARCH

Researchers Find CWD Proteins in Deer Semen

Mechanisms for transmission of CWD prions among captive or wild cervids are not fully understood. Mechanisms for transmission of CWD prions among captive or wild cervids are not fully understood. (John Maday)

By JOHN MADAY January 14, 2020

In research with potential implications for cervid breeders and wild herds, scientists have detected the presence of chronic wasting disease (CWD) prions in semen and sexual tissues of prion-infected whitetail deer bucks.

The team of researchers, from the University of Texas Health Science Center at Houston, Colorado State University and USDA/APHIS Veterinary Services published their findings in a report titled “In Vitro detection of Chronic Wasting Disease (CWD) prions in semen and reproductive tissues of white tailed deer bucks (Odocoileus virginianus),” in the online journal PLOS ONE.

In their report, the researchers note that mechanisms for transmission of CWD prions are not fully understood, and previous research has not explored the presence of the prions in semen or sexual tissues in deer.

The team collected post-mortem samples from farmed pre-clinical, CWD positive WTD bucks, and analyzed them using Protein Misfolding Cyclic Amplification (PMCA) technology.

Overall CWD detection in these samples had a sensitivity of 59.3%, with a specificity of 97.2%. Results indicate high prevalence, 80 to 100% depending on the sample type, of CWD prions in male sexual organs and fluids in late stage, pre-clinical, CWD-infected deer. Improved PCMA technology with ultra-high sensitivity helped the researchers detect low levels of CWD prions in brain and lymph tissues, allowing them to identify animals with pre-clinical infections, and detect the prions in semen and sexual tissues.

Previous studies have shown that infected animals can shed CWD prions into the environment through urine, feces and saliva. The researchers note that progressive accumulation of prions in the environment by shedding, carcasses decomposition and other tissue sources over time, coupled with the prion’s environmental persistence and resistance to degradation “make a compelling argument as to the role of the environment contamination in CWD transmission in both natural and captive settings.” They suspect though, that other mechanisms are involved, including sporadic CWD cases, translocation of the infectious agent by scavengers, vertical transmission from mother to offspring, and potentially, transmission through sexual contact.

Based on their results, the researchers confirmed the presence of CWD prions in semen and male sexual tissues in CWD-infected deer. They note a need for additional experiments in live deer to determine whether CWD can be transmitted by breeding practices including sexual contacts or artificial insemination. Managers of captive cervid herds commonly exchange semen between herds for use in their breeding programs.

Read the full report from the peer-reviewed, open-access journal PLOS ONE.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0226560#sec007

For more on CWD research, see these articles from BovineVetOnline

https://www.bovinevetonline.com/news/veterinary-research/researchers-find-cwd-proteins-deer-semen

SUNDAY, AUGUST 02, 2015

TEXAS CWD, Have you been ThunderStruck, deer semen, straw bred bucks, super ovulation, and the potential TSE Prion connection, what if?

http://chronic-wasting-disease.blogspot.com/2015/08/texas-cwd-have-you-been-thunderstruck.html

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