Development of a rapid and reliable surveillance method for Ornithodoros turicata americanus in gopher tortoise (Gopherus polyphemus) burrows in the southeastern United States.

The soft tick Ornithodoros turicata Duges (Acari: Argasidae) is a potential vector of African swine fever virus (ASFV). We evaluated the efficacy of two methods to collect soft ticks rapidly and efficiently from gopher tortoise (Gopherus polyphemus) burrows, which are ubiquitous throughout large regions of the southeastern United States and their burrows are a known microhabitat of O. turicata. Burrow vacuuming was an effective and efficient tick collection method; no tick was captured employing CO2 trapping. Using an occupancy modelling framework, we estimated that the probability of detecting ticks from an infested burrow each time a sample was taken with this method was 58% and increased with the average relative humidity. With the occupancy model, we estimated that 70% of the burrows in the study area were infested with O. turicata. Manual sifting of the burrow material yielded more ticks (6.6 individuals/sample) than using a set of three sieves (2.9 individuals/sample), yet the probability of detecting the species was not different between the two methods (Pval = 0.7). These methods can inform the development of ASF vector surveillance and outbreak response plans in areas of high risk for ASFV introduction in the region.

Applying MALDI-TOF MS to resolve morphologic and genetic similarities between two Dermacentor tick species of public health importance.

Hard ticks (Acari: Ixodidae) have been historically identified by morphological methods which require highly specialized expertise and more recently by DNA-based molecular assays that involve high costs. Although both approaches provide complementary data for tick identification, each method has limitations which restrict their use on large-scale settings such as regional or national tick surveillance programs. To overcome those obstacles, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been introduced as a cost-efficient method for the identification of various organisms, as it balances performance, speed, and high data output. Here we describe the use of this technology to validate the distinction of two closely related Dermacentor tick species based on the development of the first nationwide MALDI-TOF MS reference database described to date. The dataset obtained from this protein-based approach confirms that tick specimens collected from United States regions west of the Rocky Mountains and identified previously as Dermacentor variabilis are the recently described species, Dermacentor similis. Therefore, we propose that this integrative taxonomic tool can facilitate vector and vector-borne pathogen surveillance programs in the United States and elsewhere.

Novel Rickettsia and host records for argasid ticks, including Alveonasus cooleyi, on wild mammals in Baja California, Mexico.

We conducted surveillance of mammals to investigate their associations with argasid ticks and tick-borne pathogens. During 2021, a total of 20 wild carnivores and 57 lagomorphs were sampled, and 39 argasid ticks belonging to two species were collected. All mammals and ticks were tested by molecular assays to detect Borrelia and Rickettsia infections. Nine ticks identified as Otobius megnini were collected from two coyotes (Canis latrans) and 30 Alveonasus cooleyi (McIvor 1941) were collected from six bobcats (Lynx rufus) and one rabbit (Sylvilagus auduboni). We detected Rickettsia spp. DNA in 21 of the 27 (77.8%) tested Av. cooleyi and none of the O. megnini. No ticks were PCR-positive for borreliae and all mammals were PCR-negative for both pathogen genera. Phylogenetic analysis based on gltA, htrA, and 16 S rRNA targets revealed that all rickettsiae from Av. cooleyi clustered with ancestral group rickettsiae, likely representing a novel species of possibly endosymbiotic Rickettsia. The significance of Av. cooleyi and the newly identified Rickettsia sp. to the health of wildlife is unknown, and further work is indicated to determine whether they may be relevant to public health or carnivore conservation.

A new genus and new species of sucking louse (Phthiraptera: Anoplura: Enderleinellidae) from the particoloured flying squirrel (Hylopetes alboniger) in Laos, and an updated identification key to enderleinellid genera.

Hylophthirus spinosus, new genus and new species (Phthiraptera: Anoplura: Enderleinellidae), is described from specimens collected from the particoloured flying squirrel, Hylopetes alboniger in Khammouane Province, Laos (Lao Peoples Democratic Republic). Both sexes of the new louse are illustrated with stacked microphotographs, scanning electron micrographs and line drawings. An updated morphological identification key to the six genera (Atopophthirus, Enderleinellus, Hylophthirus, Microphthirus, Phthirunculus and Werneckia) now recognised within the family Enderleinellidae is presented. The new genus is unique within the Enderleinellidae in having massive spines (modified setae) on some abdominal sternites, partially bulbous 5th antennal segments, mesothoracic spiracles borne on protuberances and the morphology of the genitalia of both sexes. Tables showing all genera of sucking lice that include species parasitising sciurids (squirrels, chipmunks, susliks and marmots), and all known species of enderleinellids, with their known host associations and geographical distributions are included and briefly discussed in relation to the new genus and species.

Rickettsia species identified in adult, host-seeking Dermacentor occidentalis (Acari: Ixodidae) from Baja California, Mexico, and Oregon and Washington, United States.

The Pacific Coast tick (Dermacentor occidentalis Marx, 1892) is a frequently encountered and commonly reported human-biting tick species that has been recorded from most of California and parts of southwestern Oregon, southcentral Washington, and northwestern Mexico. Although previous investigators have surveyed populations of D. occidentalis for the presence of Rickettsia species across several regions of California, populations of this tick have not been surveyed heretofore for rickettsiae from Baja California, Oregon, or Washington. We evaluated 1,367 host-seeking, D. occidentalis adults collected from 2015 to 2022 by flagging vegetation at multiple sites in Baja California, Mexico, and Oregon and Washington, United States, using genus- and species-specific assays for spotted fever group rickettsiae. DNA of Rickettsia 364D, R. bellii, and R. tillamookensis was not detected in specimens from these regions. DNA of R. rhipicephali was detected in D. occidentalis specimens obtained from Ensenada Municipality in Baja California and southwestern Oregon, but not from Washington. All ompA sequences of R. rhipichephali that were amplified from individual ticks in southwestern Oregon were represented by a single genotype. DNA of the Ixodes pacificus rickettsial endosymbiont was amplified from specimens collected in southwestern Oregon and Klickitat County, Washington; to the best of our knowledge, this Rickettsia species has never been identified in D. occidentalis. Collectively, these data are consistent with a relatively recent introduction of Pacific Coast ticks in the northernmost extension of its recognized range.

Ticks without borders: Microbial communities of immature Neotropical tick species parasitizing migratory landbirds along northern Gulf of Mexico.

The long-distance, seasonal migrations of birds make them an effective ecological bridge for the movement of ticks. The introduction of exotic tick species to new geographical regions can lead to the emergence of novel tick-borne pathogens or the re-emergence of previously eradicated ones. This study assessed the prevalence of exotic tick species parasitizing resident, short-distance, and long-distance songbirds during spring and autumn at stopover sites in the northern Gulf of Mexico using the mitochondrial 12S rDNA gene. Birds were captured for tick collection from six different sites from late August to early November in both 2018 and 2019. The highest number of ticks were collected in the 2019 season. Most ticks were collected off the Yellow-breasted Chat (Icteria virens) and Common Yellowthroat (Geothlypis trichas), and 54% of the total ticks collected were from Grand Chenier, LA. A high throughput 16S ribosomal RNA sequencing approach was followed to characterize the microbial communities and identify pathogenic microbes in all tick samples. Tick microbial communities, diversity, and community structure were determined using quantitative insight into microbial ecology (QIIME). The sparse correlations for compositional data (SparCC) approach was then used to construct microbial network maps and infer microbial correlations. A total of 421 individual ticks in the genera Amblyomma, Haemaphysalis, and Ixodes were recorded from 28 songbird species, of which Amblyomma and Amblyomma longirostre was the most abundant tick genus and species, respectively. Microbial profiles showed that Proteobacteria was the most abundant phylum. The most abundant bacteria include the pathogenic Rickettsia and endosymbiont Francisella, Candidatus Midichloria, and Spiroplasma. BLAST analysis and phylogenetic reconstruction of the Rickettsia sequences revealed the highest similarities to pathogenic spotted and non-spotted fever groups, including R. buchneri, R. conorii, R. prowazekii, R. bellii, R. australis, R. parkeri, R. monacensis, and R. monteiroi. Permutation multivariate analysis of variance revealed that the relative abundance of Francisella and Rickettsia drives microbial patterns across the tick genera. We also observed a higher percentage of positive correlations in microbe-microbe interactions among members of the microbial communities. Network analysis suggested a negative correlation between a) Francisella and Rickettsia and, b) Francisella and Cutibacterium. Lastly, mapping the distributions of bird species parasitized during spring migrations highlighted geographic hotspots where migratory songbirds could disperse ticks and their pathogens at stopover sites or upon arrival to their breeding grounds, the latter showing means dispersal distances from 421-5003 kilometers. These findings strongly highlight the potential role of migratory birds in the epidemiology of tick-borne pathogens.

Do parapatric populations of the ticks Amblyomma tonelliae Nava, Beati & Labruna, 2014 and Amblyomma sculptum Berlese, 1888 (Acari: Ixodidae) hybridize?

This work aimed to determine if the tick species, Amblyomma sculptum and Amblyomma tonelliae, hybridize along their contact zones in Argentina. Free-living adults and nymphs of A. sculptum and A. tonelliae were collected in seven sampling locations of northern Argentina. In four of them, the two species occur in parapatry (possible hybrid zone) whereas in the other three sites, only one species is known to occur. A total of 65 A. sculptum and 65 A. tonelliae from both, allopatric and parapatric populations, were analysed. The nuclear (ITS2) and mitochondrial (COI and 12SrDNA) gene sequences of each tick were amplified and analysed to verify whether or not they could reveal the presence of hybrids among the parapatric samples. No morphological and molecular evidence was found to support the hypothesis of ongoing natural hybridization. Intrinsic postzygotic barriers may be the cause of lack of gene flow between the two species in areas of co-ocurrence. The results can be explained by the length of time the two lineages spent in allopatry since the middle of the Miocene and before their respective distribution range expanded again reaching a narrow secondary contact zone.

Description of two new species in the Ixodes ricinus complex from the New World (Acari: Ixodidae), and redescription of Ixodes affinis Neumann, 1899.

Ixodes chacoensis n. sp. is described based on males, females, nymphs and larvae collected from vegetation, ungulates and passerine birds in northeastern Argentina. Ixodes affinis Neumann, 1899 is redescribed based on the original type specimens (females) from Leopardus pardalis, and from recently collected specimens from Costa Rica. Ixodes keiransi n. sp., previously treated as North American populations of Ixodes affinis, is described based on males and females from carnivores and ungulates from the southeastern United States. Concatenated total evidence phylogenetics based on combined DNA sequence analyses from mitochondrial genes (12SrDNA, 16SrDNA and COI) and a nuclear gene (ITS2) corroborate the recognition of these species.

A new species of tick, Ixodes (Ixodes) mojavensis (Acari: Ixodidae), from the Amargosa Valley of California.

Ixodes (Ixodes) mojavensis, n. sp. (Acari: Ixodidae), is described from all parasitic stages collected from the endangered vole Microtus californicus scirpensis Bailey, 1900 (Rodentia: Cricetidae), Mus musculus L. 1758 (Rodentia: Muridae), and Reithrodontomys megalotis (Baird; 1857) (Rodentia: Cricetidae) in the Amargosa Valley of California. When first collected in 2014, this tick was tentatively identified as Ixodes minor Neumann, 1902 because the nucleotide similarity between its 16S rDNA sequence and a homologous GenBank sequence from an I. minor from the eastern U.S. was 99.51%. Nevertheless, adults of I. mojavensis differ morphologically from I. minor by hypostomal dentition, absence of a spur on palpal segment I, and punctation patterns; nymphs by the shapes of basis capituli, auriculae, cervical grooves and external files of hypostomal denticles; and larvae by the length of idiosomal setae and hypostomal dentition. DNA sequencing of fragments of 4 different genes, 12S rDNA, 16S rDNA, cytochrome c oxidase subunit I (COI), and intergenic transcribed spacer 2 (ITS2) of I. mojavensis and of closely related species of Ixodes shows that the mitochondrial gene sequences of the new tick species are almost identical to the I. minor homologous genes. Phylogenetically, the two species do not cluster in mutually exclusive monophyletic clades. However, ITS2 sequences of I. mojavensis and I. minor diverge deeply (≥ 5.74% maximum likelihood divergence) and are as different as homologous genes from other recognized species. The discrepancy between the two sets of genes is suggestive of past mitochondrial introgression or incomplete mitochondrial lineage sorting.

Variable Effects of Temperature and Relative Humidity on Rhipicephalus sanguineus s.l. (Acari: Ixodidae) Development.

Rhipicephalus sanguineus s.l. (Latreille, 1806) can establish populations in residences and may lead to severe domestic and peridomestic infestations. Detection in the early infestation stage is challenging because of their small body size and the lack of visibility when ticks stay in sheltered refugia. The residents may believe that the infestation has been eliminated when no ticks are observed until ticks reappear when seeking hosts. Thus, it is necessary to improve our understanding of tick phenology to achieve more effective infestation management. In this study, the relationships between environmental conditions and tick development were explored in laboratory and using linear and nonlinear models. Three R. sanguineus s.l. strains, from one colony of the temperate lineage and two of the tropical lineage, were evaluated for the development of all life stages and conversion efficiency index (CEI) under five temperatures and four relative humidities (RHs). The development times differed between the three tick strains across stages and were primarily dependent on temperature. The CEIs had little variance explained by temperature, RH, or strains. Compared with the linear and exponential models with temperature as the only variable, the Brière-1 model was the best approximating model for most of the developmental rates. The developmental temperature thresholds for R. sanguineus s.l. development estimated by the Brière-1 model varied inconsistently across strains and life stages. We developed a more predictive relationship between environmental factors and R. sanguineus s.l. development, which can be utilized to predict tick development using temperature and develop appropriate control strategies.

Correction: Why Lyme disease is common in the northern US, but rare in the south: The roles of host choice, host-seeking behavior, and tick density.

[This corrects the article DOI: 10.1371/journal.pbio.3001066.].

Survey of Ticks and Tick-Borne Rickettsial and Protozoan Pathogens in Eswatini.

Ticks are widespread parasites of vertebrates and major vectors of pathogens to humans, domestic animals, and wildlife. In southern Africa, numerous tick species transmit diseases of economic and health importance. This study aimed to describe the occurrence of ticks and tick-borne pathogens in multiple land-use types and the possible role of ticks in the transmission of pathogen species. Using molecular techniques, we screened 1716 ticks for infection by rickettsial bacteria and protozoans. To characterize pathogen identity, we sequenced multiple loci from positive samples and analyzed sequences within a phylogenetic framework. Across the seven tick species collected as nymphs or adults, we detected Rickettsia, Anaplasma, Ehrlichia, Babesia, Hepatozoon, and Theileira species. We found that some tick species and tick-borne pathogens differed according to land use. For example, we found a higher density of Haemaphysalis elliptica and higher prevalence of Rickettsia in H. elliptica collected from savanna grasses used for livestock grazing near human settlements than savanna grasses in conservation areas. These findings highlight the importance of comprehensive surveillance to achieve a full understanding of the diversity and ecology of the tick-borne pathogens that can infect humans, domestic animals, and wildlife.

Why Lyme disease is common in the northern US, but rare in the south: The roles of host choice, host-seeking behavior, and tick density.

Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks must acquire Lyme spirochetes from infected vertebrate hosts, the role of wildlife species composition on Lyme disease risk has been a topic of lively academic discussion. We compared tick-vertebrate host interactions using standardized sampling methods among 8 sites scattered throughout the eastern US. Geographical trends in diversity of tick hosts are gradual and do not match the sharp decline in prevalence at southern sites, but tick-host associations show a clear shift from mammals in the north to reptiles in the south. Tick infection prevalence declines north to south largely because of high tick infestation of efficient spirochete reservoir hosts (rodents and shrews) in the north but not in the south. Minimal infestation of small mammals in the south results from strong selective attachment to lizards such as skinks (which are inefficient reservoirs for Lyme spirochetes) in the southern states. Selective host choice, along with latitudinal differences in tick host-seeking behavior and variations in tick densities, explains the geographic pattern of Lyme disease in the eastern US.

Ixodes silvanus n. sp. (Acari: Ixodidae), a new member of the subgenus Trichotoixodes Reznik, 1961 from northwestern Argentina.

Females, nymphs, and larvae of Ixodes silvanus n. sp. collected from birds and from the vegetation in northwestern Argentina (Yungas Phytogeographic Province) are described herein. The new species belongs to the subgenus Trichotoixodes (Acari: Ixodidae). The female is diagnosed by a combination of the following characters: scutum with setae moderately long and more numerous in central field, fewer and moderately long setae on lateral fields, and inconspicuous setae in anterior field; basis capituli subtriangular dorsally; porose areas large and irregular in shape, lacking distinct margins; auriculae with straight edges diverging posterolaterally and ending with small blunt processes; hypostome narrow and pointed with dental formula 4/4 in the anterior third, then 3/3 and 2/2 near the base; coxae I with two spurs, sub-equal in size, internal slightly slimmer than external. The nymph is diagnosed by notum with numerous and long setae, ventral surface covered by numerous whitish setae, scutum with short scapulae and few and shallow punctations, setae on scutum few, short and irregularly distributed, basis capituli sub-triangular dorsally with posterior margin straight, cornua large and directed postero-laterally, auriculae large and projected laterally, lateral margin of basis capituli above auriculae with a lateral and triangular projection, hypostome pointed with dental formula 3/3 in the anterior third and then 2/2, and coxa I with two short, sub-equal, triangular spurs. The diagnostic characters of the larva are: basis capituli dorsally sub-triangular with lateral angles acute and posterior margin straight, auriculae as large triangular lateral projections, hypostome with apex bluntly pointed and dental formula 3/3 in the anterior third and then 2/2, coxa I with two short, sub-equal, triangular spurs, and pattern of dorsal and ventral body setae. This new species is phylogenetically related to Ixodes brunneus, Ixodes turdus and Ixodes frontalis, and the principal hosts for all its parasitic stages are birds.

Seasonality of acarological risk of exposure to Borrelia miyamotoi from questing life stages of Ixodes scapularis collected from Wisconsin and Massachusetts, USA.

Measures of acarological risk of exposure to Ixodes scapularis-borne disease agents typically focus on nymphs; however, the relapsing fever group spirochete Borrelia miyamotoi can be passed transovarially, and I. scapularis larvae are capable of transmitting B. miyamotoi to their hosts. To quantify the larval contribution to acarological risk, relative to nymphs and adults, we collected questing I. scapularis for 3 yr at Fort McCoy, Wisconsin (WI, n = 23,367 ticks), and Cape Cod, Massachusetts (MA, n = 4190) in the United States. Borrelia miyamotoi infection prevalence was estimated for I. scapularis larvae, nymphs, females, and males, respectively, as 0.88, 2.05, 0.63, and 1.22 % from the WI site and 0.33, 2.32, 2.83, and 2.11 % from the MA site. Densities of B. miyamotoi-infected ticks (DIT, per 1000 m2) were estimated for larvae, nymphs, females, and males, respectively, as 0.36, 0.14, 0.01, and 0.03 from the WI site and 0.05, 0.06, 0.03, and 0.02 from the MA site. Thus, although larval infection prevalence with B. miyamotoi was significantly lower than that of nymphs and similar to that of adults, because of their higher abundance, the larval contribution to the overall DIT was similar to that of nymphs and trended towards a greater contribution than adults. Assuming homogenous contact rates with humans, these results suggest that eco-epidemiological investigations of B. miyamotoi disease in North America should include larvae. A fuller appreciation of the epidemiological implications of these results, therefore, requires an examination of the heterogeneity in contact rates with humans among life stages.

Detection of Rickettsia asembonensis in Fleas (Siphonaptera: Pulicidae, Ceratophyllidae) Collected in Five Counties in Georgia, United States.

We conducted a molecular survey of Rickettsia in fleas collected from opossums, road-killed and live-trapped in peridomestic and rural settings, state parks, and from pet cats and dogs in Georgia, United States during 1992-2014. The cat flea, Ctenocephalides felis (Bouché) was the predominant species collected from cats and among the archival specimens from opossums found in peridomestic settings. Polygenis gwyni (Fox) was more prevalent on opossums and a single cotton rat trapped in sylvatic settings. Trapped animals were infested infrequently with the squirrel flea, Orchopeas howardi (Baker) and C. felis. TaqMan assays targeting the BioB gene of Rickettsia felis and the OmpB gene of Rickettsia typhi were used to test 291 flea DNAs for Rickettsia. A subset of 53 C. felis collected from a cat in 2011 was tested in 18 pools which were all bioB TaqMan positive (34% minimum infection prevalence). Of 238 fleas tested individually, 140 (58.8%, 95% confidence interval [CI]: 52.5-64.9%) DNAs were bioB positive. Detection of bioB was more prevalent in individual C. felis (91%) compared to P. gwyni (13.4%). Twenty-one (7.2%) were ompB TaqMan positive, including 18 C. felis (9.5%) and 3 P. gwyni (3.2%). Most of these fleas were also positive with bioB TaqMan; however, sequencing of gltA amplicons detected only DNA of Rickettsia asembonensis. Furthermore, only the R. asembonensis genotype was identified based on NlaIV restriction analysis of a larger ompB fragment. These findings contribute to understanding the diversity of Rickettsia associated with fleas in Georgia and emphasize the need for development of more specific molecular tools for detection and field research on rickettsial pathogens.

The Ixodes ricinus complex (Acari: Ixodidae) in the Southern Cone of America: Ixodes pararicinus, Ixodes aragaoi, and Ixodes sp. cf. I. affinis.

The goal of this study was to clarify the taxonomic status of the Ixodes ricinus complex in the Southern Cone of America, by using morphological characters and molecular markers (mitochondrial 16SrDNA and cox1 genes). The morphological analysis indicates that three different taxa of the I. ricinus complex occur in this region: Ixodes pararicinus, Ixodes aragaoi, and Ixodes sp. cf. I. affinis. The most prominent diagnostic character among them is the size of scutal punctations in both male and female ticks. In the males of Ixodes sp. cf. I. affinis, the punctations on the central field and along the median marginal groove of the scutum are clearly larger than in the males of I. aragaoi and I. pararicinus, while the punctations of I. aragaoi are larger but less numerous than in I. pararicinus. The punctations in Ixodes sp. cf. I. affinis females are larger and deeper than in females of I. aragaoi and I. pararicinus, and those of I. aragaoi are slightly larger than in I. pararicinus. The length of the lateral posterior denticles of the male hypostome is comparatively longer in I. aragaoi than in the other two species, and longer in Ixodes sp. cf. I. affinis than in I. pararicinus. In the 16S analysis, I. pararicinus and I. aragaoi are monophyletic (99% and 98% bootstrap support, respectively), while Ixodes cf. I. affinis does not represent a single lineage. In the cox1 analysis, both I. pararicinus and I. aragaoi are well-defined taxa, but the bootstrap support for Ixodes sp. cf. I. affinis is low (67%). In general, there are considerable 16SrRNA differences among lineages of Ixodes sp. cf. I. affinis from different geographical areas. These results may be indicative of the existence of different species. The populations morphologically compatible with I. affinis from Argentina, Colombia, Panama, Belize, and USA should be provisionally named as Ixodes sp. cf. I. affinis until an integrative taxonomic work with further evidence redefines whether or not this taxon actually represents a species complex.

Reported County-Level Distribution of the American Dog Tick (Acari: Ixodidae) in the Contiguous United States.

In the United States, tick-borne diseases are increasing in incidence and cases are reported over an expanding geographical area. Avoiding tick bites is a key strategy in tick-borne disease prevention, and this requires current and accurate information on where humans are at risk for exposure to ticks. Based on a review of published literature and records in the U.S. National Tick Collection and National Ecological Observatory Network databases, we compiled an updated county-level map showing the reported distribution of the American dog tick, Dermacentor variabilis (Say). We show that this vector of the bacterial agents causing Rocky Mountain spotted fever and tularemia is widely distributed, with records derived from 45 states across the contiguous United States. However, within these states, county-level records of established tick populations are limited. Relative to the range of suitable habitat for this tick, our data imply that D. variabilis is currently underreported in the peer-reviewed literature, highlighting a need for improved surveillance and documentation of existing tick records.

Rickettsia parkeri and Candidatus Rickettsia andeanae in Tick of the Amblyomma maculatum Group, Mexico.

We report Rickettsia parkeri and Candidatus Rickettsia andeanae in ticks of the Amblyomma maculatum group collected from dogs in Sonora, Mexico. Molecular characterization of these bacteria was accomplished by DNA amplification and sequence analysis of portions of the rickettsial genes gltA, htrA, ompA, and ompB.

A pictorial key to differentiate the recently detected exotic Haemaphysalislongicornis Neumann, 1901 (Acari, Ixodidae) from native congeners in North America.

Until recently, only two haemaphysaline species, Haemaphysalischordeilis (Packard, 1869) and Haemaphysalisleporispalustris (Packard, 1869), were known to occur in the United States, and neither was considered to be of significant medical or veterinary importance. In 2017-2018 established populations of the Asian longhorned tick, Haemaphysalislongicornis Neumann, 1901, were detected in the eastern US for the first time. Haemaphysalislongicornis has the potential to be a significant threat to human and animal health, and the urgent need to determine the full extent of its distribution and host range requires availability of a straightforward and practical guide to differentiate it from native species. We created a pictorial dichotomous key to all stages of Haemaphysalis spp. known to occur in North America with scanning electron photomicrographs of all H.longicornis life stages, including rarely seen males, to aid researchers in differentiating these species. The largely Neotropical species Haemaphysalisjuxtakochi Cooley, 1946, with established populations in Mexico and sporadic detections in the US on migrating birds is also included.