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Soto P, Bravo-Risi F, Kramm C, Gamez N, Benavente R, Bonilla DL, Reed JH, Lockwood M, Spraker TR, Nichols T, Morales R. Nasal bots carry relevant titers of CWD prions in naturally infected white-tailed deer. EMBO Rep 2024; 25:334-350. [PMID: 38191872 PMCID: PMC10883265 DOI: 10.1038/s44319-023-00003-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 10/31/2023] [Accepted: 11/07/2023] [Indexed: 01/10/2024] Open
Abstract
Chronic wasting disease (CWD) is a prion disease affecting farmed and free-ranging cervids. CWD is rapidly expanding across North America and its mechanisms of transmission are not completely understood. Considering that cervids are commonly afflicted by nasal bot flies, we tested the potential of these parasites to transmit CWD. Parasites collected from naturally infected white-tailed deer were evaluated for their prion content using the protein misfolding cyclic amplification (PMCA) technology and bioassays. Here, we describe PMCA seeding activity in nasal bot larvae collected from naturally infected, nonclinical deer. These parasites efficiently infect CWD-susceptible mice in ways suggestive of high infectivity titers. To further mimic environmental transmission, bot larvae homogenates were mixed with soils, and plants were grown on them. We show that both soils and plants exposed to CWD-infected bot homogenates displayed seeding activity by PMCA. This is the first report describing prion infectivity in a naturally occurring deer parasite. Our data also demonstrate that CWD prions contained in nasal bots interact with environmental components and may be relevant for disease transmission.
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Affiliation(s)
- Paulina Soto
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O'Higgins, Santiago, Chile
| | - Francisca Bravo-Risi
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O'Higgins, Santiago, Chile
| | - Carlos Kramm
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Nazaret Gamez
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Rebeca Benavente
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Denise L Bonilla
- United States Department of Agriculture, Animal Plant Health Inspection Service, Veterinary Services, Fort Collins, CO, USA
| | - J Hunter Reed
- Texas Parks and Wildlife Department, Kerrville, TX, USA
| | | | - Terry R Spraker
- Colorado State University Diagnostic Medical Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Tracy Nichols
- United States Department of Agriculture, Animal Plant Health Inspection Service, Veterinary Services, Fort Collins, CO, USA
| | - Rodrigo Morales
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA.
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O'Higgins, Santiago, Chile.
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Inzalaco HN, Bravo-Risi F, Morales R, Walsh DP, Storm DJ, Pedersen JA, Turner WC, Lichtenberg SS. Ticks harbor and excrete chronic wasting disease prions. Sci Rep 2023; 13:7838. [PMID: 37188858 DOI: 10.1038/s41598-023-34308-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 04/27/2023] [Indexed: 05/17/2023] Open
Abstract
Chronic wasting disease (CWD) is a fatal neurodegenerative disease caused by infectious prions (PrPCWD) affecting cervids. Circulating PrPCWD in blood may pose a risk for indirect transmission by way of hematophagous ectoparasites acting as mechanical vectors. Cervids can carry high tick infestations and exhibit allogrooming, a common tick defense strategy between conspecifics. Ingestion of ticks during allogrooming may expose naïve animals to CWD, if ticks harbor PrPCWD. This study investigates whether ticks can harbor transmission-relevant quantities of PrPCWD by combining experimental tick feeding trials and evaluation of ticks from free-ranging white-tailed deer (Odocoileus virginianus). Using the real-time quaking-induced conversion (RT-QuIC) assay, we show that black-legged ticks (Ixodes scapularis) fed PrPCWD-spiked blood using artificial membranes ingest and excrete PrPCWD. Combining results of RT-QuIC and protein misfolding cyclic amplification, we detected seeding activity from 6 of 15 (40%) pooled tick samples collected from wild CWD-infected white-tailed deer. Seeding activities in ticks were analogous to 10-1000 ng of CWD-positive retropharyngeal lymph node collected from deer upon which they were feeding. Estimates revealed a median infectious dose range of 0.3-42.4 per tick, suggesting that ticks can take up transmission-relevant amounts of PrPCWD and may pose a CWD risk to cervids.
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Affiliation(s)
- H N Inzalaco
- Wisconsin Cooperative Wildlife Research Unit, Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Madison, WI, 53706, USA.
| | - F Bravo-Risi
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O'Higgins, Santiago, Chile
| | - R Morales
- Department of Neurology, The University of Texas Health Science Center at Houston, Houston, TX, USA
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O'Higgins, Santiago, Chile
| | - D P Walsh
- U.S. Geological Survey, Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT, USA
| | - D J Storm
- Wisconsin Department of Natural Resources, Eau Claire, WI, USA
| | - J A Pedersen
- Environmental Health and Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - W C Turner
- Wisconsin Cooperative Wildlife Research Unit, Department of Forest and Wildlife Ecology, U.S. Geological Survey, University of Wisconsin - Madison, Madison, WI, 53706, USA
| | - S S Lichtenberg
- Department of Soil Science, University of Wisconsin, Madison, Madison, WI, USA
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Evaluation of Winter Ticks (Dermacentor albipictus) Collected from North American Elk (Cervus canadensis) in an Area of Chronic Wasting Disease Endemicity for Evidence of PrP CWD Amplification Using Real-Time Quaking-Induced Conversion Assay. mSphere 2021; 6:e0051521. [PMID: 34346708 PMCID: PMC8386475 DOI: 10.1128/msphere.00515-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Chronic wasting disease (CWD) is a progressive and fatal spongiform encephalopathy of deer and elk species, caused by a misfolded variant of the normal prion protein. Horizontal transmission of the misfolded CWD prion between animals is thought to occur through shedding in saliva and other forms of excreta. The role of blood in CWD transmission is less clear, though infectivity has been demonstrated in various blood fractions. Blood-feeding insects, including ticks, are known vectors for a range of bacterial and viral infections in animals and humans, though to date, there has been no evidence for their involvement in prion disease transmission. In the present study, we evaluated winter ticks (Dermacentor albipictus) collected from 136 North American elk (Cervus canadensis) in an area where CWD is endemic for evidence of CWD prion amplification using the real-time quaking-induced conversion assay (RT-QuIC). Although 30 elk were found to be CWD positive (22%) postmortem, amplifiable prions were found in just a single tick collected from an elk in advanced stages of CWD infection, with some evidence for prions in ticks collected from elk in mid-stage infection. These findings suggest that further investigation of ticks as reservoirs for prion disease may be warranted. IMPORTANCE This study reports the first finding of detectable levels of prions linked to chronic wasting disease in a tick collected from a clinically infected elk. Using the real-time quaking-induced conversion assay (RT-QuIC), “suspect” samples were also identified; these suspect ticks were more likely to have been collected from CWD-positive elk, though suspect amplification was also observed in ticks collected from CWD-negative elk. Observed levels were at the lower end of our detection limits, though our findings suggest that additional research evaluating ticks collected from animals in late-stage disease may be warranted to further evaluate the role of ticks as potential vectors of chronic wasting disease.
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