title: Can Subclinical Infestation by Paralyzing Dermacentor andersoni (Acari: Ixodidae) Induce Immunity to Tick Paralysis in Sheep?
abstract: Cattle and sheep can develop immunity to paralysis caused by Dermacentor andersoni Stiles; however, this has been reported only in animals that were initially challenged with a high dose of ticks and exhibited clear symptoms of paralysis. Paralysis in sheep occurs in a dose-dependent fashion, with no paralysis occurring in sheep exposed to <0.2 ticks per kilogram sheep weight, and 100% paralysis in sheep exposed to >0.8 ticks per kilogram. This experiment was conducted to determine if sheep exposed to a low dose of ticks would also develop immunity to paralysis. Sheep were exposed to either a low (0.2 ticks per kilogram) or high dose of ticks (0.8 ticks per kilogram), then re-exposed to a second challenge of a paralyzing dose of ticks. All naïve sheep (eight of the eight) were paralyzed, while paralysis occurred in only four of the eight sheep previously exposed to a low dose, and one of the eight sheep previously exposed to a high dose. Results indicate that immunity can develop when sheep are exposed to a subclinical dose of paralyzing ticks, but in a smaller percentage of animals than those exposed to a high dose of ticks. Vaccine development perhaps remains the best option for nonacaricidal control of tick paralysis.
authors.affiliation: Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB, Canada T1J 4B1 (timlysyk@gmail.com; Shaun.Dergousoff@AGR.GC.CA), timlysyk@gmail.com.|Retired, and.
authors.forename: T J
authors.initials: TJ
authors.lastname: Lysyk
authors.affiliation: Research and Development Centre, Agriculture and Agri-Food Canada, 5403 1st Avenue South, Lethbridge, AB, Canada T1J 4B1 (timlysyk@gmail.com; Shaun.Dergousoff@AGR.GC.CA).
authors.forename: S J
authors.initials: SJ
authors.lastname: Dergousoff
mesh_terms: D000818:Animals; D005260:Female; D026863:Ixodidae / Q000502:physiology*; D008297:Male; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology* / Q000469:parasitology / Q000473:pathology; D013985:Tick Paralysis / Q000276:immunology / Q000469:parasitology / Q000473:pathology / Q000662:veterinary*
keywords: Rocky Mountain wood tick; dose-dependent; immunity; sheep; tick paralysis