First Record of Carios kelleyi (Acari: Ixodida: Argasidae) in New Jersey, United States and Implications for Public Health

Bats and ectoparasites: exploring a hidden link in zoonotic disease transmission

Bats are increasingly in the focus of disease surveillance studies as they harbor pathogens that can cause severe human disease. In other host groups, ectoparasitic arthropods play an important role in transmitting pathogens to humans. Nevertheless, we currently know little about the role of bat-associated ectoparasites in pathogen transmission, not only between bats but also to humans and other species, even though some of these parasites occasionally feed on humans and harbor potentially zoonotic organisms. In this work, we summarize current knowledge on the zoonotic risks linked to bat-associated ectoparasites and provide novel risk assessment guidelines to improve targeted surveillance efforts. Additionally, we suggest research directions to help adjust surveillance strategies and to better understand the eco-epidemiological role of these parasites.

Bat-associated ticks as a potential link for vector-borne pathogen transmission between bats and other animals

BACKGROUND

Potentially zoonotic pathogens have been previously detected in bat-associated ticks, but their role in disease transmission and their frequency of feeding on non-bat hosts is poorly known.

METHODOLOGY/PRINCIPAL FINDINGS

We used molecular blood meal analysis to reveal feeding patterns of the bat-associated tick species Ixodes ariadnae, I. simplex, and I. vespertilionis collected from cave and mine walls in Central and Southeastern Europe. Vertebrate DNA, predominantly from bats, was detected in 43.5% of the samples (70 of 161 ticks) but in these ticks we also detected the DNA of non-chiropteran hosts, such as dog, Canis lupus familiaris, wild boar, Sus scrofa, and horse, Equus caballus, suggesting that bat-associated ticks may exhibit a much broader host range than previously thought, including domestic and wild mammals. Furthermore, we detected the zoonotic bacteria Neoehrlichia mikurensis in bat ticks for the first time, and other bacteria, such as Bartonella and Wolbachia.

CONCLUSIONS/SIGNIFICANCE

In the light of these findings, the role of bat ticks as disease vectors should be urgently re-evaluated in more diverse host systems, as they may contribute to pathogen transmission between bats and non-chiropteran hosts.

Rickettsia and relapsing fever Borrelia in Alectorobius kelleyi (Ixodida: Argasidae) from peri domestic bats in the northeastern United States

The soft ticks (Argasidae) are known vectors of human and animal pathogens around the globe and are relatively understudied. Our aim was to assess the presence of Rickettsia and Borrelia bacteria in Alectorobius kelleyi (Argasidae) parasitizing synanthropic bats in the highly urbanized northeastern United States. By collaborating with parasitologists, bat scientists and wildlife rehabilitators we were successful in obtaining A. kelleyi from five states. Since Argasid larvae will attach to their hosts for many days, most A. kelleyi examined (92%) were larvae collected from sick or injured big brown bats, Eptesicus fuscus, undergoing care at rehabilitation centers. In addition, we obtained adult A. kelleyi captured in residential living areas and trapped in attics. An in-depth analysis of a A. kelleyi found to be infected with a spotted fever group Rickettsia (SFGR) revealed a dual infection with a R. belli-like taxon (ancestral group) as well as an SFGR closely related to R. peacockii, likely the same previously found in A. kelleyi from Iowa and Kansas. We found that 36% of the A. kelleyi tested carried the SFGR. Furthermore, we detected a relapsing fever spirochete, likely Candidatus Borrelia johnsonii, in 25% of the A. kelleyi from Pennsylvania. While it is unclear if these bacteria constitute a health risk to either bats or humans, our study indicates that human exposure to ectoparasites infesting peridomestic wildlife should be considered in the epidemiology of tick-borne diseases.

First Report of the Bat Tick Carios kelleyi (Acari: Ixodida: Argasidae) From Vermont, United States

The soft tick Carios kelleyi (Cooley and Kohls, 1941) is an ectoparasite of bats that can harbor bacteria known to cause disease in humans, such as Rickettsia spp., Bartonella spp., and relapsing fever Borrelia spp. Human-tick encounters may occur when bats occupy attics or similar dwellings with access points to human-inhabited areas. During May 2021, a partially engorged adult female C. kelleyi was collected from a Vermont home with an attic that was being used as a roost by big brown bats, Eptesicus fuscus (Chiroptera: Vespertilionidae). The source of the blood in the tick was the domestic dog, Canis lupus familiaris. Subsequently, eight C. kelleyi larvae were collected from a rescued E. fuscus adult. This is the first report of a soft tick species from Vermont and it is unknown how long C. kelleyi has been present in this state. Reports of C. kelleyi are on the rise across the northeastern United States but the implications for the health of humans, domestic animals, and bats in northern New England remain unclear. Bat management plans should consider the importance of bat exclusion in preventing tick encounters with members of the household and should include a tick monitoring component if bats are evicted.

Ixodes scapularis (Ixodida: Ixodidae) Parasitizing an Unlikely Host: Big Brown Bats, Eptesicus fuscus (Chiroptera: Vespertilionidae), in New York State, USA

Ixodes scapularis Say is a three-host tick that has been recorded feeding on over 150 different species of terrestrial vertebrates (mammals, birds, and reptiles). This tick is found throughout the northeastern, coastal southeastern, and upper midwestern United States and is considered the most significant vector of tick-borne pathogens to humans in North America. Despite its ubiquity and broad host range, I. scapularis previously has not been reported feeding on bats (Chiroptera). However, during 2019 and 2020, larvae and nymphs of I. scapularis were recovered from big brown bats, Eptesicus fuscus (Palisot de Beauvois), at four locations in rural New York State, USA. All Ixodes infested bats were injured and found on the ground; therefore, parasitism by I. scapularis was likely opportunistic. Nonetheless, the large number of pathogens known to be associated with bats and the frequency with which I. scapularis bites people suggest that this host-tick relationship is of at least potential epidemiological significance.

Carios kelleyi (Acari: Ixodida: Argasidae) Infected With Rickettsial Agents Documented Infesting Housing in Kansas, United States

During September-December 2018, 25 live ticks were collected on-post at Fort Leavenworth, Kansas, in a home with a history of bat occupancy. Nine ticks were sent to the Army Public Health Center Tick-Borne Disease Laboratory and were identified as Carios kelleyi (Cooley and Kohls, 1941), a species that seldom bites humans but that may search for other sources of blood meals, including humans, when bats are removed from human dwellings. The ticks were tested for numerous agents of human disease. Rickettsia lusitaniae was identified by multilocus sequence typing to be present in two ticks, marking the first detection of this Rickettsia agent in the United States and in this species of tick. Two other Rickettsia spp. were also detected, including an endosymbiont previously associated with C. kelleyi and a possible novel Rickettsia species. The potential roles of C. kelleyi and bats in peridomestic Rickettsia transmission cycles warrant further investigation.