Abstract
Read the full article for the answer.
KEYWORDS: soft tick, spinose ear tick, Otobius, arthropods, parasitology, ectoparasite
ANSWER TO PHOTO QUIZ
The organisms were identified as nymphs of the spinose ear tick, Otobius megnini, a soft tick in the family Argasidae. Natural hosts for O. megnini are ungulates, such as cattle, goats, sheep, and deer, but other mammals can be parasitized, including dogs and humans. The tick is native to western North America where its natural host is the pronghorn antelope and has been introduced nearly worldwide where livestock are raised (1, 2). Otobius megnini has four life cycle stages, egg, larva, nymph, and adult, and is adapted to complete its life cycle on a single host. Larvae and nymphs feed in the ear of their host for several days to months; however, adults are not parasitic (3). Humans usually become infested due to prolonged or regular contact with parasitized livestock or pets. In this case, the dogs may have become attached with ticks while on walks, thus introducing the ticks into the household where it could then infest the human. Otobius are not known to vector any infectious diseases to humans, although secondary bacterial infections can occur.
Unlike many other soft ticks that feed on their vertebrate hosts for short periods of time, O. megnini spends prolonged time in the ear of its host. As such, zoonotic infections are likely to lead to specimens being submitted to the clinical laboratory for identification. As a member of Argasidae, nymphs are characterized by the lack of a dorsal shield (scutum), and their mouthparts may not be visible from above. Their body is often panduriform (violin shaped), and their dorsal setae are modified into strong spines on the dorsal surface (2, 4).
Contributor Information
Marc Roger Couturier, Email: marc.couturier@aruplab.com.
Bobbi S. Pritt, Mayo Clinic Minnesota, Rochester, Minnesota, USA
REFERENCES
- 1. Mathison BA, Pritt BS. 2022. Parasites of the ear, p 279–286. In Rezaei N (ed), Encyclopedia of infection and immunity. Elsevier, Oxford. [Google Scholar]
- 2. Barker SC, Walker AR. 2014. Ticks of Australia. The species that infest domestic animals and humans. Zootaxa 3816:1–144. doi: 10.11646/zootaxa.3816.1.1 [DOI] [PubMed] [Google Scholar]
- 3. Diyes GCP, Rajakaruna RS. 2017. Life cycle of Spinose ear tick, Otobius megnini (Acari: Argasidae) infesting the race horses in Nuwara Eliya, Sri Lanka. Acta Trop 166:164–176. doi: 10.1016/j.actatropica.2016.11.026 [DOI] [PubMed] [Google Scholar]
- 4. Mathison BA, Pritt BS. 2014. Laboratory identification of arthropod ectoparasites. Clin Microbiol Rev 27:48–67. doi: 10.1128/CMR.00008-13 [DOI] [PMC free article] [PubMed] [Google Scholar]