Introduction

Classification

Taxonomy

• Class: Arachnida ; subclass: Acari
• Order: Metastigmata or Ixodida
• Family: Ixodidae
• Genus: Hyalomma
• Species: approximately 25 species including H. lusitanicum, H. marginatum, H. truncatum.

Active Forms

Resting Forms

Clinical Effects

Epidemiology

Habitat

• Hosts for the adult stages are large animals including ruminants, camelids, deer, ostrich, horses, but much depends on the species in question; eg H. dromedarii has camels as the principal host.
• Nymphs and larvae rarely parasitize rodents but prefer other small mammals such as lagamorphs and insectivores as well as birds.
• Regions with low to moderate levels of humidity and a long dry season during the summer months are natural habitats. These include savannah and scrubland hills and valleys. They are not found in  deciduous woodland and mixed forests.

Lifecycle

• Most Hyalomma spp ticks are 2 host ticks including H. marginatum. Engorged larvae remain on the same host to moult and feed again as nymphs.
• Nymphs that drop off from the host in the spring will moult and overwinter as an adult. Those that detach in Autumn will overwinter as nymphs. 
• Life cycle (egg to adult) can be completed in 3-4 months but a year may be necessary in less favorable areas. Unfed adults may survive up to two years.

Seasonal activity levels

• Adult ticks appear on preferred hosts in Spring.
• Main activity period for the adults is March-June with a secondary peak in Autumn (August-November).
• Immature stages active between June and October with peak numbers in July and August. Timings may be affected by dry season in arid regions.

Pathological effects

• Pruritus in susceptible dogs, local hypersensitivity with tick-bite site ulceration.
• Paralysis caused by H. truncatum bites.
• Transmission of Babesia, Theileria and Anaplasma spp.
• Hyalomma spp ticks are also vectors for Crimean-Congo hemorrhagic fever (CCHF) virus which can infect a wide range of mammals and is zoonotic. H. marginatum is the main vector in Europe Focal epidemics can have case fatality rates as high as 40%. CCHF is distributed across South Western Europe, Africa and Asia.
  • CCHF virus is a sub clinical infection in most mammalian hosts but in humans can cause fever, shock, hemorrhage and death.
• Several other viral pathogens and Rickettsia aeschlimannii.

Control

Control via chemotherapies

• There are several safe, very effective acaricides with long-duration of activity across multiple tick species for use on dogs using tablets containing isoxazolines (afoxolaner Afoxolaner, fluralaner Fluralaner, lotilaner, sarolaner Sarolaner) or topical formulations (spot-ons, collars, sprays) containing:
  • Amitrax Amitraz.
  • Fipronil Fipronil
  • Synthetic pyrethroids (permethrin Permethrin, deltamethrin or flumethrin) that have repellent activity as well.
• Pyriprole.

Control via environment

• Largely impractical except where infestation is confined to a limited space such as kennels.
• Outdoor premises control of ticks includes use of carbamates and synthetic pyrethroids. Older insecticides have efficacy but their use is controlled by regulatory approval.
• Synthetic pyrethroids for indoor control (and for use in cars, kennels and cages). Older drugs under regulatory control but may be used by commercial pest exterminators.

Vaccination

• None available for tick control. See control of tick-borne diseases Tick control.

Other countermeasures

• Mechanical tick removal to help reduce transmission of pathogens.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Hansford K M, Pietzsch M E, Cull B et al (2018) Potential risk posed by the importation of ticks into the UK on animals: records from the Tick Surveillance Scheme. Vet Rec 182 (4), 107 PubMed.
• Hansford K M, Medlock J M, Atkinson B et al (2016) Importation of a Hyalomma lusitanicum tick into the UK on a dog. Vet Rec 179 (16), 415 PubMed.
• Movila A, Alekseev A N, Dubinina H V et al (2013) Detection of tick-borne pathogens in ticks from migratory birds in the Baltic region of Russia. Med Vet Entomol 27 (1), 113-117 PubMed.
• Estrada-Peña A, Jameson L, Medlock J et al (2012) Unravelling the ecological complexities of tick-associated Crimean-Congo hemorrhagic fever virus transmission: a gap analysis for the western Palearctic. Vector Borne Zoonotic Dis 12 (9), 743-752 VetMedResource.
• Jameson L J, Morgan P J, Medlock J M et al (2012) Importation of Hyalomma marginatum, vector of Crimean-Congo haemorrhagic fever virus, into the United Kingdom by migratory birds. Ticks Tick Borne Dis 3 (2), 95-99 PubMed.
• Estrada-Peña A, Martínez Avilés M, Muñoz Reoyo M J (2011) A population model to describe the distribution and seasonal dynamics of the tick Hyalomma marginatum in the Mediterranean Basin. Transbound Emerg Dis 58 (3), 213-223 PubMed.

Other sources of information

• World Health Organisation (2013) Crimean-Congo haemorrhagic fever: www.who.int/news-room/fact-sheets/detail/crimean-congo-haemorrhagic-fever.
• Wall R and Shearer D S (Editors) (2008) Veterinary Ectoparasites: Biology, Pathology and Control , Edition 2, Blackwell Science Ltd, London, pp 71-74.
• Vatansever Z, Uzun R, Estrada-Pena A, Ergonul O (2007) Crimean-Congo hemorrhagic fever in Turkey. In: Ergonul O, Whitehouse C A (eds) Crimean-Congo hemorrhagic fever: a global perspective. Dordrecht: Springer. pp 59-74.
• Baker A S (1990) Mite and ticks of domestic animals: An identication and information source. The Natural History Museum, The Stationary Office, London, pp 176-179.