Abstract
Tick-borne diseases have a complex epidemiology that depends on different ecological communities, associating several species of vertebrate hosts, vectors and pathogens. While most studies in Europe are focused on Ixodes ricinus, other Ixodes species may also be involved in the transmission or maintenance of pathogens. This is the case of Ixodes frontalis, a poorly known species associated with different bird species such as blackbirds, thrushes and robins, with a wide distribution covering most European countries.In a previous study, high densities of questing I. frontalis larvae were found during autumn-winter at a site close to Nantes (western France) where a long-term survey focused on I. ricinus was conducted. These I. frontalis were mostly observed under bamboo bushes. In the present study, we investigated the presence of I. frontalis under bamboo bushes at various locations. With that aim in mind, a systematic search for questing I. frontalis was undertaken by the flagging method in public urban parks and private gardens presenting bamboo bushes (32 sites). This survey was carried out during autumn-winter to maximize the probability of finding the most abundant stage, i.e. larvae. We searched for I. frontalis first in the area of Nantes (10 sites), then in other regions of France (21 sites) and at one site in northern Italy. A single visit to each site revealed the presence of I. frontalis at 29 out of 32 sites: larvae were always present, nymphs were frequent (59 % of the positive sites), while adults were found at only 14 % of the sites. Questing stages of this understudied species are thus easy to find, by dragging or flagging under bamboo bushes in autumn or winter. We make the assumption that bamboo offers a favourable place for birds to roost overnight outside their breeding period (i.e. spring), sheltered from both predators and wind. This would explain higher densities of I. frontalis under bamboo, relative to other biotopes.As I. frontalis is known to harbour zoonotic pathogens, the consequences of this discovery on the epidemiology of tick-borne diseases are discussed.
Highlights
While most studies of tick-borne diseases including field sampling usually focus on widespread tick species known to have a strong impact on animal and public health, it is crucial to keep in mind that the ecoepidemiology of those diseases is related to the occurrence of other tick species, even if they are considered to be rare
Particular strains of Ana plasma phagocytophilum have been reported to be associated with Ixodes ventalloi, a nidicolous specialist tick parasitizing rabbits (Jaarsma et al, 2019), or to Ixodes trianguliceps, a nidicolous specialist tick infesting small rodents (Bown et al, 2006), while those hosts are used by I. ricinus for its blood meals
As birds have often been quoted as potential reservoirs of Borrelia that can be transmitted to humans by I. ricinus bites (Coipan and Sprong, 2016; Hanincovaet al., 2003), the implication of specialist ticks asso ciated with birds, such as I. frontalis, in the maintenance of zoonotic pathogens within bird populations can be suspected
Summary
While most studies of tick-borne diseases including field sampling usually focus on widespread tick species known to have a strong impact on animal and public health, it is crucial to keep in mind that the ecoepidemiology of those diseases is related to the occurrence of other tick species, even if they are considered to be rare. Particular strains of Ana plasma phagocytophilum have been reported to be associated with Ixodes ventalloi, a nidicolous specialist tick parasitizing rabbits (Jaarsma et al, 2019), or to Ixodes trianguliceps, a nidicolous specialist tick infesting small rodents (Bown et al, 2006), while those hosts are used by I. ricinus for its blood meals Another example involves birds, notably blackbirds and other species of the Turdus genus, that are frequently parasitized by the tick Ixodes frontalis, an exclusively ornithophilic species (Drehmann et al, 2019; Martyn, 1988; Remesar et al, 2019a, b). Ticks and Tick-borne Diseases 12 (2021) 101625 description of a particular habitat, that could help to find this tick spe cies elsewhere than on its host, has yet been provided, except by Agoulon et al (2019) These authors discovered thousands of I. frontalis larvae under bamboo bushes, collected by the dragging method in autumn and winter, even revealing a higher frequency of the larval stage of this species relative to I. ricinus during those seasons. To investigate if this finding can be generalised, tick samplings were carried out under bamboo bushes at several locations in France and Italy to search for I. frontalis questing stages
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