The mechanism by which ticks get into the subcutaneous tissue is still unexplained. Several tick-related factors such as the species or the sex were incriminated as favoring factors. According to currently available literature, a more common presence under the skin was noted for ticks with a long rostrum (i.e. Ixodes spp.) or ticks feeding for longer periods (adults in general and females in particular), which seem to be predisposing factors [7, 8]. Although it is evident that the vast majority of reports of subcutaneous ticks are from red foxes (Table 1), it is not clear if also host-related factors are involved. It is also unclear if the lack of reports from other hosts is related to the absence of subcutaneous ticks or the lack of studies or incomplete necropsies in other hosts. To understand the full host spectrum of this unusual occurrence, negative reports are also useful. However, with the exception of one study in roe deer [9], no other negative reports are known.
Table 1. Review of reports of ticks in subcutaneous tissues of various hosts
Host
|
Species
|
Country
|
Reference
|
Red fox
Vulpes vulpes
|
Ixodes ricinus
Ixodes hexagonus
|
UK
|
[12]
|
Ixodes ricinus
|
Poland
|
[13]
|
Ixodes ricinus
|
Austria
|
[14]
|
Ixodes ricinus
|
Slovakia
|
[15]
|
Ixodes ricinus
|
Slovakia
|
[16]
|
Amblyomma americanum
|
USA
|
[17]
|
Ixodes ricinus
Ixodes hexagonus
Ixodes crenulatus
Dermacentor reticulatus
|
Czech Republic
|
[7]
|
Ixodes ricinus
|
Romania
|
[7]
|
Ixodes ricinus
|
Slovakia
|
[18]
|
Ixodes ricinus
|
Sweden
|
[19]
|
Ixodes ricinus
Dermacentor reticulatus
|
Poland
|
[20]
|
Ixodes ricinus
Ixodes hexagonus
Ixodes canisuga
|
Germany
|
[8]
|
Raccoon dog
Nyctereutes procyonoides
|
Ixodes ricinus
|
Poland
|
[21]
|
Domestic dog
Canis familiaris
|
Ixodes ricinus
|
Sweden
|
[19]
|
Human
Homo sapiens
|
not identified Ixodidae
|
South Korea
|
[22]
|
Golden jackal
Canis aureus
|
Ixodes ricinus
|
Romania
|
current study
|
We report here for the first time the presence of a subcutaneous tick in golden jackals (frequency 1/57; 95% CI 0.04-9.39%) and the absence in 11 other carnivore host species. However, with the exception of few hosts, such as Eurasian badgers, beech martens and wild cats, the number of samples from other carnivore species is too low to draw a stronger conclusion.
What is clear at the moment is that so far, with the exception of one human case, all other reports originate from canids, with high local prevalence in red foxes [7, 8]. The vast majority of these reports refer to ticks of genus Ixodes (Table 1) but this may also be related to the more common occurrence of these ticks in red foxes [10, 11].