The phenomenon of attachment and feeding of unfed ticks (Ixodoidea) on fed and feeding specimens of the same or different species: biological and epidemiological issues

Abstract

Hyperparasitism, characterized by attachment and feeding of unfed ticks on engorged or feeding specimens of the same species (tick-to-tick attachment and feeding) has been extensively documented in laboratory colonies of ticks of the Ixodoidea superfamily. Existing literature generally assumes that hyperparasitism operates similarly across tick species in both main families, Argasidae and Ixodidae. However, a closer examination of the available data reveals distinct biological mechanisms underlying this phenomenon in different groups. In argasid ticks, hyperparasitism in laboratory colonies primarily involves unfed specimens stealing blood from their fed relatives, especially under stress of starvation or overcrowding. It remains uncertain whether this behavior of argasid ticks occurs under field conditions. If it does happen naturally, it may have originated as a consequence of the nidicolous lifestyle exhibited by soft ticks. In Ixodes ticks (Ixodinae or Prostriata), hyperparasitism of males on unfed or feeding females appears to be a side-effect in the male attempts to copulate while hyperparasitism in Amblyomminae (Metastriata) ticks is likely an aberration in feeding. This difference between Argasidae and Ixodidae may stem from independent adaptation to blood-feeding within the two Ixodoidea families. Experimental evidence of pathogen transmission between aggressor and victim during hyperparasitic feeding has only been demonstrated under laboratory conditions specifically in Ornithodoros species (Argasidae). The practical importance of this route of pathogen transmission is still unclear. Although there is an assumption in the literature that hyperparasitic pathogen transmission occurs in the taiga tick Ixodes persulcatus, it is important to know that no current data is available to support this presumption.