Abstract
Ticks are obligate hematophagous arthropods and act as vectors for a great variety of pathogens, including viruses, bacteria, protozoa, and helminths. Some tick-borne viruses, such as Powassan virus and tick-borne encephalitis virus, are transmissible within 15–60 min after tick attachment. However, a minimum of 3–24 h of tick attachment is necessary to effectively transmit bacterial agents such as Ehrlichia spp., Anaplasma spp., and Rickettsia spp. to a new host. Longer transmission periods were reported for Borrelia spp. and protozoans such as Babesia spp., which require a minimum duration of 24–48 h of tick attachment for maturation and migration of the pathogen. Laboratory observations indicate that the probability of transmission of tick-borne pathogens increases with the duration an infected tick is allowed to remain attached to the host. However, the transmission time may be shortened when partially fed infected ticks detach from their initial host and reattach to a new host, on which they complete their engorgement. For example, early transmission of tick-borne pathogens (e.g., Rickettsia rickettsii, Borrelia burgdorferi, and Babesia canis) and a significantly shorter transmission time were demonstrated in laboratory experiments by interrupted blood feeding. The relevance of such situations under field conditions remains poorly documented. In this review, we explore parameters of, and causes leading to, spontaneous interrupted feeding in nature, as well as the effects of this behavior on the minimum time required for transmission of tick-borne pathogens.
Highlights
Ticks are obligate hematophagous Acari that parasitize vertebrate animals and occasionally bite humans [1]
This interrupted feeding pattern, in which ticks continue to feed on a second host organism during the same feeding cycle, was demonstrated to result in reduced transmission times for the B. burgdorferi, Rickettsia rickettsii, and Babesia canis tick-borne pathogens (Table 1)
Before migrating between dogs, ticks were attached and presumably partially fed on the first dog for at least 48 h prior to changing hosts. This example could serve as a natural model for testing whether or not interrupted blood feeding might reduce the duration of attachment and accelerate the transmission of tick-borne pathogens [42]
Summary
Ticks are obligate hematophagous Acari that parasitize vertebrate animals and occasionally bite humans [1]. [21,22] These variations in the transmission time can be explained by the presence of pathogens in salivary glands of unfed ticks at the time of blood feeding as demonstrated in anterior studies on Anaplasma spp., Ehrlichia spp., and Rickettsia spp. Termed “interrupted feeding”, the ability of partially fed ticks to survive, reattach to a new host, and complete engorgement is supported by their ability to switch their salivary gland gene expression pattern as demonstrated in Rhipicephalus appendiculatus ticks [33] This interrupted feeding pattern, in which ticks continue to feed on a second host organism during the same feeding cycle, was demonstrated to result in reduced transmission times for the B. burgdorferi, Rickettsia rickettsii, and Babesia canis tick-borne pathogens (Table 1)
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