Ticks harbor and excrete chronic wasting disease prions

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.

Nasal bots carry relevant titers of CWD prions in naturally infected white-tailed deer

“…In comparison, another report described the presence of real-time quaking-induced conversion (RT-QuIC) seeding activity in winter ticks ( Dermacentor albipictus ) collected from naturally affected North American elk (Haley et al, 2021 ). More recently, prion seeding activity has been found in lab fed and naturally occurring black-legged ticks ( Ixodes scapularis ) (Inzalaco et al, 2023 ). Regardless of these positive findings in relevant samples, the specific infectivity titers contained in these parasites is unknown.…”

Detection of Chronic Wasting Disease Prions in Prairie Soils from Endemic Regions

“…The CWD minimum infectious dose approximates to 100–300 ng of CWD-positive brain, and that amount could be a threshold for the detection in the environmental samples. There are sensitive methods and techniques that allow for detection of low amounts of PrP CWD in different materials: real-time quaking-induced conversion (RT-QuIC) for saliva, urine, and spiked environmental surfaces; and serial protein misfolding amplification (PMCA) for feces, muscle tissue, spiked soils, − invertebrates, or vegetation grown in the laboratory . These techniques result in an increase of the detection limit of CWD prions by 4 orders of magnitude.…”

Genetic characterization of the prion protein gene in camels (Camelus) with comments on the evolutionary history of prion disease in Cetartiodactyla

“…Additionally, dietary intake may influence transmission of prion diseases through consumption of infected animal products (meat, milk, etc .) or through infectious prions on or within plants and other biotic and abiotic material in the environment ( Bartelt-Hunt, Bartz & Yuan, 2023 ; Gough & Maddison, 2010 ; Inzalaco et al, 2023 ; Johnson et al, 2011 ; Konold et al, 2008 ; Kuznetsova et al, 2023 ; Lacroux et al, 2008 ; Prusiner, 1997 ).…”