Sunday, August 12, 2018

Answer to Case 506

Answer: Hard tick, Hyalomma sp.

As many of you noted, this is one of the "Old World" ticks found in many parts of North Africa, South Africa, the Middle East, Asia, and Europe.

Here are a few important facts about this tick :

  1. They are one of the most medically important ticks in the Old World. 
  2. Important species include Hyalomma marginatum (Mediterranean Hyalomma), H. trucantum, H. asiaticum, H. excavatum, H. aegyptium, H. scupense and H. rufipes. 
  3. They are vectors for several important disease agents, including Crimean-Congo hemorrhagic fever virus, several Rickettsia spp., Anaplasma phagocytophilum, Coxiella burnetii, and possibly Rift Valley Fever virus. 
  4. They have also been implicated in human tick paralysis. 
  5. Both female and male ticks bite humans and can transmit pathogens.
  6. Compared to Ixodes ticks which climb vegetation and wait for a host to walk by, Hyalomma actively seek out their hosts (similar to Amblyommma spp.).
  7. The tick is not endemic to North America, but there have been a series of case reports detailing imported Hyalomma species on humans, animals, and animal products. Check out the report that Blaine Mathison and I recently published HERE.
This is the second case of imported Hyalomma that has been brought to my attention in just the past 3 years, and the 3rd that Blaine has seen (!) highlighting the important of appropriate recognition and tick identification. 

As Blaine and I mention in our manuscript, Hyalomma spp. might be misidentified as Amblyomma when using keys for North American ticks. We state that "Hyalomma can best be separated from Amblyomma by having festoons of varying size, an inornate dorsal shield (scutum), and spurs on the coxae I roughly equal in length." Of note, many (but not all) Hyalomma spp. also have a striking band pattern on their legs as seen in this case.
Check out our manuscript for links to various regional-specific Hyalomma identification keys. Identifying the species can be tricky due to genetic variation and morphological variations.

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