gms | German Medical Science

It was shown that Tissue Tolerable Plasma (TTP) generated by the KINPen09 was able to inactivate and/or kill the human-relevant parasite Demodex follicularum, which belongs to the subclass of acari [1]. Therefore, testing the efficacy of TTP against ticks on their main representative Ixodes ricinus is justifiable, because ticks are characterized by their broad range of hosts and they are responsible for the transmission of several infectious diseases, such as the animal and human pathogens causing Lyme disease, ehrlichiosis, and babesiosis. The inactivation of ticks by plasma is convenient, where mechanical removal is often problematic in cases of difficult access to certain anatomic structures, e.g., the auditory canal or interdigital space of dogs or cats, or if the tick is too small to be pulled out with tweezers etc. In the latter case, one should not wait for the tick to enlarge by aspiring enough to blood to be seized, because it is likely that the transmission of pathogens increases with time.

For the study, 24 vital sheep ticks (Ixodes ricinus) in different stages of aspiration were mechanically removed from cats and dogs by twisting the ticks out after fixation with plastic forceps.

The KINPen09 was used as the plasma source [2]. The argon (Ar) gas flow was set to 5 slm (standard liters per minute). The application times were 1 min, 3 min and 5 min. To apply the plasma, the visible tip of the plasma jet was placed at the tick’s chelicerae (mouthparts).

The observation period for all ticks was 5–7 days. The endpoint of observation was determined as fetor of beginning decay or visible shrinkage as a sign of desiccation. Both criteria were considered as signs of the tick’s death.

A treatment time of 1 min led to a reversible inactivation of the ticks (n=6). After initial immobilization, however, the ticks resumed motility after 0.5 to 5 h. A post-treatment of another 3 min led to a constant immobilized state.

An initial treatment time of 3 min led to persistant inactivation for some of the ticks (n=5). However, other ticks (n=4) became mobile again within 24 h.

A treatment time of 5 min led to persistant inactivation of all ticks (n=9) within the observation period.

With the KINPen09, an irreversible inactivation of Ixodes ricinus was reached with a treatment time of 5 min. Even if the host’s adjacent skin is accidentally exposed to the plasma, there is no risk of damage, because the much more sensitive chorioallantois membrane of a fertilized, incubated chicken egg tolerates the same plasma source up to 40 s [3], [4]. Furthermore, the treatment of chronic wounds with the KINPen09 [5], [6] has been shown to be successful until complete healing is attained, without any side effects [7].

The results demonstrate the acaricidal effect of plasma and introduce a whole new treatment strategy for tick-infested pets.

The authors declare that they have no competing interests.

This work was realized within the framework of the multidisciplinary research cooperation “Campus PlasmaMed”, particularly within the project “PlasmaDent”. The authors acknowledge that this work was supported by a grant from the German Ministry of Education and Research (BMBF, grant no. 13N9779).