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Fowler PD, Nguyentran S, Quatroche L, Porter ML, Kobbekaduwa V, Tippin S, Miller G, Dinh E, Foster E, Tsao JI. Northward Expansion of Amblyomma americanum (Acari: Ixodidae) into Southwestern Michigan. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1646-1659. [PMID: 35776508 PMCID: PMC9989843 DOI: 10.1093/jme/tjac082] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Indexed: 05/28/2023]
Abstract
Amblyomma americanum (Linnaeus) (Acari: Ixodidae) (lone star tick) is an aggressive, generalist parasite that vectors numerous important human and animal pathogens. In recent decades its geographic range has expanded northwards from endemic regions in the southeastern and southcentral United States. In 2019 five questing A. americanum ticks, comprising two life stages were detected at one site in southwestern Michigan, satisfying one CDC criterium for an established population for the first time in recent history in the state. To better characterize the extent of emerging A. americanum, we conducted active surveillance (i.e., drag sampling) in summer 2020 throughout Michigan's southern counties and detected one adult A. americanum from each of six widespread sites, including where they had been detected in 2019. A larger established population was identified at another site in Berrien County, which yielded 691 A. americanum comprising three life stages, and questing phenologies here were similar to that reported for other endemic regions. Statewide surveillance in 2021 revealed no A. americanum outside of Berrien County, but establishment criteria were met again at the two sites where established populations were first detected respectively in 2019 and 2020. These observations may represent the successful invasion of A. americanum into Michigan. Data from passive (1999-2020) and active surveillance (2004-2021) efforts, including a domestic animal sentinel program (2015-2018), are reported to provide context for this nascent invasion. Continued active surveillance is needed to help inform the public, medical professionals, and public health officials of the health risks associated with this vector.
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Polsomboon Nelson S, Bourke BP, Badr R, Tarpey J, Caicedo-Quiroga L, Leiva D, Pott M, Cruz A, Chao CC, Achee NL, Grieco JP, Jiang L, Jiang J, Farris CM, Linton YM. Ticks (Acari: Ixodidae) and Associated Pathoge Collected From Domestic Animals and Vegetation in Stann Creek District, Southeastern Belize, Central America. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1749-1755. [PMID: 35904108 PMCID: PMC9473654 DOI: 10.1093/jme/tjac112] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Indexed: 06/01/2023]
Abstract
Data on the prevalence and distribution of ticks and tick-borne diseases in Belize are lacking. Ticks (n = 564) collected from dogs, horses, and vegetation in two villages in Stann Creek District in southeastern Belize in 2018, were molecularly identified and screened for tick-borne nonviral human pathogens. The identity of 417 ticks was molecularly confirmed by DNA barcoding as Rhipicephalus sanguineus (Latreille) (66.43%), Amblyomma ovale Koch (15.59%), Dermacentor nitens Neumann (11.51%), Amblyomma sp. ADB0528 (3.6%), and the remainder being small records (2.87%) of Amblyomma coelebs Neumann, Amblyomma imitator Kohls, Amblyomma tapirellum Dunn, Amblyomma auricularium Conil, and Amblyomma maculatum Koch. Individual tick extracts were screened for the presence of Rickettsia spp., Babesia spp., Babesia microti, Borrelia spp., Ehrlichia spp., and Anaplasma spp. using available conventional polymerase chain reaction (PCR) assays. Rickettsia parkeri strain Atlantic Rainforest was identified in five specimens of A. ovale, and one other unidentified tick, all collected from dogs. Another unidentified tick-also collected from a dog-tested positive for an undefined but previously detected Ehrlichia sp. With the exception of D. nitens, all eight other tick species identified in this study were collected on dogs, suggesting that dogs could be usefully employed as sentinel animals for tick surveillance in Belize.
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Webb GK. Problematic White-Tailed Deer Information in Rochlin et al. (2022) Regarding Past and Future Tick ( Amblyomma americanum, Acari: Ixodidae) Distributions. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1489-1491. [PMID: 35802006 PMCID: PMC9473651 DOI: 10.1093/jme/tjac090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Indexed: 06/15/2023]
Abstract
Figure 3 in this Journal of Medical Entomology article is central to the authors' warning about an exploding white-tailed deer population but conflicts in important aspects with the relevant deer research. Among other problems, it shows a 60% increase in the white-tailed deer density from 1500 to 2020 when the research consensus is that the population is about the same. It shows an exploding population from 2000 to 2020 without supporting data when the population peaked around the year 2000 according to evidence-based research.
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Arroyave E, Quade B, Mendell NL, Blanton LS, Bouyer DH. Genetic characterization of a novel Ehrlichia chaffeensis genotype from an Amblyomma tenellum tick from South Texas, USA. Ticks Tick Borne Dis 2022; 13:101990. [PMID: 35763959 PMCID: PMC9940300 DOI: 10.1016/j.ttbdis.2022.101990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 06/07/2022] [Accepted: 06/13/2022] [Indexed: 12/15/2022]
Abstract
Ehrlichia chaffeensis is the causative agent of human monocytotropic ehrlichiosis (HME), a disease that ranges in severity from mild to fatal infection. Ehrlichia chaffeensis is maintained in a zoonotic cycle involving white-tailed deer (Odocoileus virginianus) as the main vertebrate reservoir and lone star ticks (Amblyomma americanum) as its principal vector. Through complete genomic analysis from human ehrlichial isolates and DNA sequences obtained from deer and tick specimens, nine strains of E. chaffeensis have been characterized. Few studies have examined the genetic diversity of E. chaffeensis in ticks, and some of these investigations have identified that the genetic sequences coincide with the circulating strains reported so far. Here, we report the first evidence of E. chaffeensis DNA from an unfed Amblyomma tenellum (formerly Amblyomma imitator) collected in South Texas. We characterized the genetic variation of this E. chaffeensis genotype using conserved gene markers such as rRNA, dsb, and groEL. We also used gene targets useful to distinguish genotypes, such as the variable length PCR target gene (VLPT) and 120-kDa gene, encoding the tandem-repeat proteins TRP32 and TRP120, respectively. Our results suggest a novel E. chaffeensis genotype that exhibited greater variability than other genotypes of E. chaffeensis and highlights the role for A. tenellum as a potential vector of E. chaffeensis.
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Grostieta E, Zazueta-Islas HM, Cruz-Valdez T, Ballados-González GG, Álvarez-Castillo L, García-Esparza SM, Cruz-Romero A, Romero-Salas D, Aguilar-Domínguez M, Becker I, Sánchez-Montes S. Molecular detection of Coxiella-like endosymbionts and absence of Coxiella burnetii in Amblyomma mixtum from Veracruz, Mexico. EXPERIMENTAL & APPLIED ACAROLOGY 2022; 88:113-125. [PMID: 36244047 DOI: 10.1007/s10493-022-00748-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 10/03/2022] [Indexed: 06/16/2023]
Abstract
Ticks are obligate ectoparasites associated with a wide range of vertebrate hosts, including domestic animals. Moreover, ticks are capable of transmitting many pathogens such as Coxiella. To date, Coxiella burnetii, the etiological agent of coxiellosis or Q fever, is the only valid species of the genera. Nevertheless, a wide range of agents denominated Coxiella-like have been detected in recent studies, mainly associated with ticks. The pathogenicity of these Coxiella-like agents is controversial as some of them can infect both birds and humans. In Mexico, knowledge about Q fever is scarce and limited to historical serological records, and there is an overall lack of molecular proof of any agent of the genus Coxiella circulating in the country. Therefore, the aim of this study was to detect the presence of Coxiella in ticks associated with cattle in all 10 regions of Veracruz, Mexico. To accomplish this objective, first, we identified ticks collected from cattle and horses in Veracruz. Then, for Coxiella detection, DNA extraction from ticks and PCR amplification of the 16S-rDNA of Coxiella was performed. Finally, we performed a phylogenetic reconstruction to determine the Coxiella lineages detected. From the 10 regions sampled we collected 888 ticks grouped in 180 pools, and only five Amblyomma mixtum from the locality of Castán, and one from Los Angeles from Tuxpan were found positive, which represents a frequency of 20% for each locality. This study represents the first attempt at molecular detection of Coxiella in ticks associated with cattle in the state of Veracruz, the major livestock producer in the country. The findings of the present study are relevant as they establish a precedent regarding the circulation of Coxiella-like agents, as well as the absence in three municipalities of the state of Veracruz of C. burnetii, an abortive agent of livestock importance.
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Che Lah EF, George E, Apanaskevich D, Ahmad M, Yaakop S. First Record of the Tortoise Tick, Amblyomma geoemydae (Cantor, 1847) (Acari: Ixodidae) Parasitizing a Tree Shrew, Tupaia glis (Scandentia: Tupaiidae) in West Malaysia. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1473-1478. [PMID: 35482611 DOI: 10.1093/jme/tjac042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Indexed: 06/14/2023]
Abstract
The tick genus Amblyomma Koch, 1844 (Acari: Ixodidae) has received little attention in Malaysia; therefore, its associated hosts and distribution records are poorly known. In this study, we collected six Amblyomma sp. individuals (two larvae and four adults) that infested a common treeshrew, Tupaia glis (Diard, 1820) (Scandentia: Tupaiidae) caught in a recreational area in Sungai Lembing, Pahang (West Malaysia). The adult female ticks were morphologically identified according to taxonomic keys prior to molecular identification using cytochrome oxidase subunit I (COI) and 16S rDNA genes. The ticks were genetically verified as Amblyomma geoemydae (Cantor, 1847) with 98%-99% similarity to the available GenBank sequences. Neighbor-joining (NJ) trees indicated that A. geoemydae was clearly distinguished from other Amblyomma ticks and this was supported with high bootstrap values. This paper is the first to report A. geoemydae ticks infesting T. glis and provides a new tick-host record from West Malaysia. This information is significant for further investigation, specifically on this tick species as potential vector of tick-borne disease (TBD) agents.
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Bajwa WI, Tsynman L, Egizi AM, Tokarz R, Maestas LP, Fonseca DM. The Gulf Coast Tick, Amblyomma maculatum (Ixodida: Ixodidae), and Spotted Fever Group Rickettsia in the Highly Urbanized Northeastern United States. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1434-1442. [PMID: 35639921 DOI: 10.1093/jme/tjac053] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Indexed: 06/15/2023]
Abstract
We report the multi-year collection of the Gulf Coast tick, Amblyomma maculatum Koch (Acaridae: Ixodida: Ixodidae) in Staten Island, New York City (NYC) as well as their detection in Brooklyn, NYC, and in Atlantic and Cumberland counties in southern New Jersey, USA. The first and most common detections were of adults, however in Freshkills Park on Staten Island larvae were also collected in a following year. The presence of larvae indicates that adults are successfully finding hosts in Staten Island. While it is still unknown how A. americanum reached Staten Island, immatures of this species often parasitize migratory birds, which are now often seen in Freshkills Park. We describe the landscape features of the area in Staten Island where populations were highest and larvae were detected, which could have facilitated the establishment of A. maculatum. Notably, we also report the presence of human pathogens Rickettsia parkeri in 5/10 (50%) of adults tested and R. felis in 1/24 (4.17%) of larvae tested. In addition to established populations in Staten Island we found evidence of A. maculatum in NJ and other NYC boroughs, suggesting current or future establishment is possible. The failure thus far to detect established populations in these areas may be due to inherent difficulties in detecting low density, spatially heterogeneous incipient populations, which could require targeted surveillance efforts for this species. We discuss the consequences to public health of the establishment of A. maculatum and detection of two additional rickettsial pathogens in the densely populated northeastern United States.
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Maldonado-Ruiz LP, Urban J, Davis BN, Park JJ, Zurek L, Park Y. Dermal secretion physiology and thermoregulation in the lone star tick, Amblyomma americanum. Ticks Tick Borne Dis 2022; 13:101962. [PMID: 35525214 DOI: 10.1016/j.ttbdis.2022.101962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 03/21/2022] [Accepted: 04/24/2022] [Indexed: 11/29/2022]
Abstract
Ticks are hematophagous ectoparasites that transmit a wide range of pathogens. The lone star tick, Amblyomma americanum, is one of the most widely distributed ticks in the Midwest and Eastern United States. Lone star ticks, as other three-host ixodid ticks, can survive in harsh environments for extended periods without a blood meal. Physiological mechanisms that allow them to survive during hot and dry seasons include thermal tolerance and water homeostasis. Dermal fluid secretions have been described in metastriate ticks including A. americanum. We hypothesized that tick dermal secretion in the unfed tick plays a role in thermoregulation, as described in other hematophagous arthropods during blood feeding. In this study, we found that physical contact with a heat probe at 45 °C or high environmental temperature at ∼50 °C can trigger dermal secretion in A. americanum and other metastriate ticks in the off-host period. We demonstrated that dermal secretion plays a role in evaporative cooling when ticks are exposed to high temperatures. We find that type II dermal glands, having paired two cells and forming large glandular structures, are the source of dermal secretion. The secretion was triggered by an injection of serotonin, and the serotonin-mediated secretion was suppressed by a pretreatment with ouabain, a Na/K-ATPase blocker, implying that the secretion is controlled by serotonin and the downstream Na/K-ATPase.
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Prado RFS, Araújo IM, Cordeiro MD, Baêta BDA, da Silva JB, da Fonseca AH. Diversity of tick species (Acari: Ixodidae) in military training areas in Southeastern Brazil. REVISTA BRASILEIRA DE PARASITOLOGIA VETERINARIA = BRAZILIAN JOURNAL OF VETERINARY PARASITOLOGY : ORGAO OFICIAL DO COLEGIO BRASILEIRO DE PARASITOLOGIA VETERINARIA 2022; 31:e001322. [PMID: 35648978 PMCID: PMC9901875 DOI: 10.1590/s1984-29612022027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 04/04/2022] [Indexed: 11/22/2022]
Abstract
Tick-borne pathogens belong to one of the two main groups of occupational biohazards, and occupational exposure to such agents puts soldiers at risk of zoonotic infections, such as those caused by rickettsiae. There are few studies on acarological fauna and occupational risk in military areas in Brazil. Thus, the present study aimed to analyze the diversity of ticks present in the military training areas of municipalities in the Southeast Region of Brazil. The ticks were collected from the selected areas using the dragging and flagging techniques as well as by visual detection on the operators' clothing, and environmental information was also recorded. A total of ten species were collected from the 66 surveyed areas, belonging to five genera and nine species: Amblyomma sculptum, Amblyomma dubitatum, Amblyomma brasiliense, Amblyomma longirostre, Amblyomma aureolatum, Dermacentor nitens, Rhipicephalus spp., Ixodes spp. and Haemaphysalis spp. The frequent presence of tick species in military training areas along with traces and sightings of wild animals, most commonly capybaras (Hydrochoerus hydrochaeris), in most of the studied areas, indicates high levels of exposure of the military to tick vectors of spotted fever group rickettsiae and the possible occurrence of infections among the troops.
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Noden BH, Dubie TR, Henriquez BE, Gilliland M, Talley JL. Seasonality of Ticks and Prevalence of Rickettsiae Species in Dermacentor variabilis and Amblyomma maculatum Across Oklahoma Pastures. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1033-1041. [PMID: 35289851 DOI: 10.1093/jme/tjac028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Tick-borne diseases are an increasing concern for people and companion animals in the United States, but there is a need for continued vigilance regarding livestock in pasture systems. The south-central United States has some of the highest incidences of tick-borne diseases, and there is a need to re-examine the ecology of tick vectors in relation to pasture systems and livestock. The objective of this study was to establish a baseline of seasonal activity for tick species in diverse regional Oklahoma pastures and screen for important pathogens in Dermacentor variabilis (Say) and Amblyomma maculatum Koch group that may impact livestock and human health. Between 2015 and 2017, transects in five pastures across Oklahoma were visited each month. DNA extracted from adult D. variabilis and A. maculatum group was tested for the presence of bacterial pathogens. We found that tick communities in pastures across Oklahoma differ by season, abundance, and bacterial presence and prevalence. The peak abundance of Amblyomma americanum (L.) adults and nymphs occurred a month earlier over the 2 yr of the study compared with historical studies in the same regions. Additionally, we observed notable differences in peak activity between A. americanum adults and nymphs collected in pastures in central Oklahoma (April) versus pastures in northern part of the state (May). We detected Rickettsia parkeri, R. bellii, and Anaplasma sp. DNA in D. variabilis from pastures across the state. These results potentially have important ramifications for human and livestock risk of encountering infected ticks in pastures across the southern Great Plains.
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Kaplan ZD, Richardson EA, Taylor CE, Kaufman PE, Weeks ENI. Determination of the Discriminating Concentration Towards Permethrin for Surveying Resistance in Amblyomma americanum. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:922-929. [PMID: 35323944 PMCID: PMC9113138 DOI: 10.1093/jme/tjac029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Indexed: 06/14/2023]
Abstract
Amblyomma americanum Linnaeus (Ixodida: Ixodidae) is ubiquitously present throughout the southeastern United States and is capable of vectoring several pathogens. White-tailed deer are the main host for adult A. americanum. However, this tick species is a generalist that will feed on most vertebrates, including humans, deer, livestock, and pets. Management of this species can be challenging due to a lack of cost-effective strategies. Acaricides are often utilized, however, this may lead to pesticide resistance. The Food and Agriculture Organization of the United Nations (FAO) larval packet test (LPT) was performed on susceptible A. americanum to determine the lethal concentration (LC) and discriminating concentration (DC) values for permethrin. The FAO LPT was used at these pre-established values to compare levels of resistance in ticks collected from a captive deer farm and wild areas representing high and low permethrin exposure settings, respectively. Resistance ratios (RR) calculated from the LC values for the ticks collected from farmed and wild deer ranged between 1 and 2. A. americanum collected from farmed and wild deer were not found to be resistant, however, some samples had slightly elevated RRs as compared to the susceptible laboratory strain, which may suggest tolerance development. Although the A. americanum sampled in this study were not resistant to permethrin, the DC calculated in this study will allow for rapid evaluation of resistance in a permethrin resistance monitoring program such that alternate management strategies can be adopted if resistance is detected.
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Gonçalves ES, Cordeiro MD, Dos Santos LMR, Araújo IM, da Fonseca AH, Labruna MB, Guedes E. Research of Rickettsia spp. and Borrelia spp. in dogs in Southeast Brazil. Vet Parasitol Reg Stud Reports 2022; 30:100706. [PMID: 35431064 DOI: 10.1016/j.vprsr.2022.100706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 12/01/2021] [Accepted: 02/12/2022] [Indexed: 06/14/2023]
Abstract
Dogs are important in the epidemiology of tick-borne diseases, playing a significant role mainly in endemic areas of rickettsiosis and borreliosis, and serving as sentinels in epidemiological surveys. We analyzed the distribution of Rickettsia and Borrelia spp. in dogs and their ticks in the municipalities of Guaxupé, Minas Gerais, and Tapiratiba, São Paulo, Brazil, two areas non-endemic for Baggio-Yoshinari Syndrome (BYS) and rickettsiosis. Serum from 242 dogs of different ages (>12 months) and breeds were tested by the Indirect Immunofluorescence Assay (IFA) using specific antigens for Rickettsia rickettsii, Rickettsia parkeri, Rickettsia amblyommatis, Rickettsia rhipicephali, and Rickettsia bellii, and by an indirect Enzyme Linked Immunosorbent Assay (ELISA) for the detection of homologous IgG antibodies against Borrelia burgdorferi American strain G39/40. Ticks were collected from the animals and subjected to PCR and nested PCR for detection of Rickettsia spp. (synthase citrate gene) and Borrelia spp. (flagellin gene). Serological data showed that 7.85% (19/242) of the analyzed dogs were seropositive for at least one of the five Rickettsia antigens tested; one (0.41%) was considered seropositive for R. parkeri (1:64) and one (0.41%) for R. rickettsii (1:256). Nine (3.72%) were considered seropositive for R. bellii and one (0.41%) for R. amblyommatis; a seroprevalence of 13.64% (33/242) for IgG class immunoreactive antibodies against B. burgdorferi was observed. A total of 148 ticks were collected from the dogs; among these 3.40% were identified as larvae of the genus Rhipicephalus and 0.70% of the genus Amblyomma; 89.8% were identified as Rhipicephalus sanguineus, 4.70% Amblyomma sculptum and 1.40% Amblyomma ovale; all negative for PCR of Rickettsia spp. and nested PCR for Borrelia spp.. The serological findings of this study suggest the circulation of Rickettsiae associated with the spotted fever group and vector ticks, just like Borrelia spp. in a non-endemic Brazilian area, drawing attention to the possibility of a zoonotic cycle in the region.
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Kumar D, Sharma SR, Adegoke A, Kennedy A, Tuten HC, Li AY, Karim S. Recently Evolved Francisella-Like Endosymbiont Outcompetes an Ancient and Evolutionarily Associated Coxiella-Like Endosymbiont in the Lone Star Tick ( Amblyomma americanum) Linked to the Alpha-Gal Syndrome. Front Cell Infect Microbiol 2022; 12:787209. [PMID: 35493735 PMCID: PMC9039623 DOI: 10.3389/fcimb.2022.787209] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 03/18/2022] [Indexed: 12/04/2022] Open
Abstract
Background Ticks are hematophagous arthropods that transmit various bacterial, viral, and protozoan pathogens of public health significance. The lone star tick (Amblyomma americanum) is an aggressive human-biting tick that transmits bacterial and viral pathogens, and its bites are suspected of eliciting the alpha-gal syndrome, a newly emerged delayed hypersensitivity following consumption of red meat in the United States. While ongoing studies have attempted to investigate the contribution of different tick-inherent factors to the induction of alpha-gal syndrome, an otherwise understudied aspect is the contribution of the tick microbiome and specifically obligate endosymbionts to the establishment of the alpha-gal syndrome in humans. Materials and Methods Here we utilized a high-throughput metagenomic sequencing approach to cataloging the entire microbial communities residing within different developmental stages and tissues of unfed and blood-fed ticks from laboratory-maintained ticks and three new geographical locations in the United States. The Quantitative Insights Into Microbial Ecology (QIIME2) pipeline was used to perform data analysis and taxonomic classification. Moreover, using a SparCC (Sparse Correlations for Compositional data) network construction model, we investigated potential interactions between members of the microbial communities from laboratory-maintained and field-collected ticks. Results Overall, Francisellaceae was the most dominant bacteria identified in the microbiome of both laboratory-raised and field-collected Am. americanum across all tissues and developmental stages. Likewise, microbial diversity was seen to be significantly higher in field-collected ticks compared with laboratory-maintained ticks as seen with a higher number of both Operational Taxonomic Units and measures of species richness. Several potential positive and negative correlations were identified from our network analysis. We observed a strong positive correlation between Francisellaceae, Rickettsiaceae, and Midichloriaceae in both developmental stages and tissues from laboratory-maintained ticks, whereas ovarian tissues had a strong positive correlation of bacteria in the family Xanthobacteraceae and Rhizobiaceae. A negative interaction was observed between Coxiellaceae and Francisellaceae in Illinois, and all the bacteria detected from ticks from Delaware were negatively correlated. Conclusion This study is the first to catalog the microbiome of Am. americanum throughout its developmental stages and different tissue niches and report the potential replacement of Coxiellaceae by Francisellaceae across developmental stages and tissues tested except in ovarian tissues. These unique and significant findings advance our knowledge and open a new avenue of research to further understand the role of tick microbiome in tick-borne diseases and develop a holistic strategy to control alpha-gal syndrome.
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Forero-Becerra E, Acosta A, Benavides E, Martínez-Díaz HC, Hidalgo M. Amblyomma mixtum free-living stages: Inferences on dry and wet seasons use, preference, and niche width in an agroecosystem (Yopal, Casanare, Colombia). PLoS One 2022; 17:e0245109. [PMID: 35385470 PMCID: PMC8986011 DOI: 10.1371/journal.pone.0245109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/02/2022] [Indexed: 12/03/2022] Open
Abstract
The formulation of effective control strategies for any pest species generally involves the study of habitat use and preference and niche width in anthropogenically transformed natural landscapes. We evaluated whether the use, habitat preference, and niche range of the Amblyomma mixtum tick changed between stages, habitats, and seasonality (dry-wet seasons 2019) on a farm in Yopal (Casanare, Colombia). The presence and relative abundance of free-living larvae, nymphs, and adults was quantified in four different habitats according to the type of vegetation cover (Riparian Forest, Cocoa Crop, King Grass Crop, and Star Grass Paddock). Habitat availability was estimated, environmental variables were analyzed, and various indices of habitat use and preference, and niche width were calculated. A. mixtum's habitat use and preference, and niche width changed between stages, habitat types, and time of the year. The total abundance of A. mixtum was an order of magnitude greater in the dry season than the wet season. In the dry season, all stages used all habitats, while A. mixtum adults used all the habitats in both seasons. In the dry season, nymphs and larvae preferred three out of the four habitats, while adults preferred the King Grass Crop. In the wet season, nymphs and larvae preferred two habitats, whereas the adults preferred the King Grass Crop. The value of the niche width index was high for larvae, nymphs, and adults in the dry season, while it was high only for adults in the wet season. Thus, A. mixtum's vast environmental tolerance and niche breadth allows the species to use and colonize changing habitats (unstable or temporary) with fluctuating environmental conditions (e.g., King Grass Crop), potentially keeping a stable population over time and making it an extremely resistant species. However, the wet flooding season in Yopal may exceed A. mixtum's stages' tolerances.
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Romer Y, Adcock K, Wei Z, Mead DG, Kirstein O, Bellman S, Piantadosi A, Kitron U, Vazquez-Prokopec GM. Isolation of Heartland Virus from Lone Star Ticks, Georgia, USA, 2019. Emerg Infect Dis 2022; 28:786-792. [PMID: 35318917 PMCID: PMC8962890 DOI: 10.3201/eid2804.211540] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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91
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Bacon EA, Kopsco H, Gronemeyer P, Mateus-Pinilla N, Smith RL. Effects of Climate on the Variation in Abundance of Three Tick Species in Illinois. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:700-709. [PMID: 34875079 PMCID: PMC8924963 DOI: 10.1093/jme/tjab189] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Indexed: 06/01/2023]
Abstract
The range of ticks in North America has been steadily increasing likely, in part, due to climate change. Along with it, there has been a rise in cases of tick-borne disease. Among those medically important tick species of particular concern are Ixodes scapularis Say (Acari: Ixodidae), Dermacentor variabilis Say (Acari: Ixodidae), and Amblyomma americanum Linneaus (Acari: Ixodidae). The aim of this study was to determine if climate factors explain existing differences in abundance of the three aforementioned tick species between two climatically different regions of Illinois (Central and Southern), and if climate variables impact each species differently. We used both zero-inflated regression approaches and Bayesian network analyses to assess relationships among environmental variables and tick abundance. Results suggested that the maximum average temperature and total precipitation are associated with differential impact on species abundance and that this difference varied by region. Results also reinforced a differential level of resistance to desiccation among these tick species. Our findings help to further define risk periods of tick exposure for the general public, and reinforce the importance of responding to each tick species differently.
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Schulze TL, Jordan RA. Daily Variation in Sampled Densities of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) Nymphs at a Single Site-Implications for Assessing Acarological Risk. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:741-751. [PMID: 34994380 DOI: 10.1093/jme/tjab213] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Indexed: 06/14/2023]
Abstract
The public health challenge posed by tick-borne disease (TBD) has increased efforts to characterize the spatial and temporal distribution of ticks and associated pathogens to better focus tick control strategies and personal protection measures. We describe variability in nymphal Ixodes scapularis Say and Amblyomma americanum (L.) density derived from daily drag sampling at a single location in New Jersey over 4 yr and explore how observed differences in daily collections might affect the estimation of acarological risk. We found significant variability in the density of host-seeking nymphs that could suggest substantially different rates of human-tick encounters depending on sampling date, habitat, and ambient weather conditions. The spatial and temporal variability in the distribution of 2 sympatric tick species with different host preferences and questing strategies, suggests that to produce results that are comparable among sites across the area sampled, surveillance efforts may be limited to shorter collection seasons, fewer sites or less sampling effort (fewer plots or fewer visits) per site, and a geographic scope that minimizes the potential temporal and spatial biases indicated here. Our results illustrate that evaluation of models of tick distribution or relative acarological risk based on surveillance data requires a full description of the diversity of habitats sampled and the conditions under which sampling is performed. The array of factors that affect tick host-seeking and that could bias interpretation of sampling results emphasizes the need to standardize sampling protocols and for more caution when interpreting tick sampling data collected over large temporal and spatial scales.
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93
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Rochlin I, Egizi A, Lindström A. The Original Scientific Description of the Lone Star Tick ( Amblyomma americanum, Acari: Ixodidae) and Implications for the Species' Past and Future Geographic Distributions. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:412-420. [PMID: 35024845 DOI: 10.1093/jme/tjab215] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Indexed: 06/14/2023]
Abstract
Amblyomma americanum L. is an important vector in North America originally described by Linnaeus based on Pehr Kalm's 1754 report. While Kalm's 'Travels into North America' is well known, his 1754 report remains obscure. Some authors were skeptical that Kalm referred to A. americanum because he encountered them at sites farther north outside of the species' range. However, the details in 1754 report leave no doubt that Kalm described lone star ticks. In this historical review, we provide support for Kalm's identification using a modern translation of his 1754 report and other sources. We also delineate distributional changes of lone star ticks from the pre-colonization era to the present and interpret them in the context of large-scale anthropogenic changes in the landscape. In this framework, the lone star tick's current northward expansion is a recolonization of their former range. Extensive deforestation and extirpation of their principal host species, white-tailed deer, led to A. americanum's disappearance from the northern parts of its range by the 20th century. Subsequent recolonization by second-growth forest and increases in white-tailed deer populations by the mid-20th century is now allowing A. americanum to reclaim its former range. These changes in the land appear to be the driving force behind A. americanum's present expansion. Understanding this species' history and the factors contributing to its current expansion will enable better predictions about its future distribution and potential to transmit human pathogens.
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Dowling APG, Young SG, Loftin K. Collaborating With Community Scientists Across Arkansas to Update Tick Distributions and Pathogen Prevalence of Spotted Fever Group Rickettsia and Ehrlichia. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:565-575. [PMID: 34850921 DOI: 10.1093/jme/tjab196] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Indexed: 06/13/2023]
Abstract
Tick-borne diseases (TBD) in humans have dramatically increased over recent years and although the bulk of cases are attributable to Lyme Disease in the Northeastern US, TBDs like spotted fever rickettsiosis and ehrlichiosis heavily impact other parts of the country, namely the mid-south. Understanding tick and pathogen distributions and prevalence traditionally requires active surveillance, which quickly becomes logistically and financially unrealistic as the geographic area of focus increases. We report on a community science effort to survey ticks across Arkansas to obtain updated data on tick distributions and prevalence of human tick-borne disease-causing pathogens in the most commonly encountered ticks. During a 20-mo period, Arkansans submitted 9,002 ticks from 71 of the 75 counties in the state. Amblyomma americanum was the most common tick species received, accounting for 76% of total tick submissions. Nearly 6,000 samples were screened for spotted fever group Rickettsia (SFGR) and Ehrlichia, resulting in general prevalence rates of 37.4 and 5.1%, respectively. In addition, 145 ticks (2.5%) were infected with both SFGR and Ehrlichia. Arkansas Department of Health reported 2,281 spotted fever and 380 ehrlichiosis cases during the same period as our tick collections. Since known SFGR vectors Dermacentor variabilis and Amblyomma maculatum were not the most common ticks submitted, nor did they have the highest prevalence rates of SFGR, it appears that other tick species play the primary role in infecting humans with SFGR. Our investigation demonstrated the utility of community science to efficiently and economically survey ticks and identify vector-borne disease risk in Arkansas.
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Maldonado-Ruiz LP, Boorgula GD, Kim D, Fleming SD, Park Y. Tick Intrastadial Feeding and Its Role on IgE Production in the Murine Model of Alpha-gal Syndrome: The Tick "Transmission" Hypothesis. Front Immunol 2022; 13:844262. [PMID: 35309294 PMCID: PMC8930817 DOI: 10.3389/fimmu.2022.844262] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 02/10/2022] [Indexed: 11/13/2022] Open
Abstract
Recent studies have provided strong evidence indicating that lone star tick bites are a cause of AGS (alpha-gal syndrome, also known as red meat allergy RMA) in humans. AGS is characterized by an increase in IgE antibody production against galactose-alpha-1,3-galactose (aGal), which is a common glycan found in mammalian tissue, except in Old World monkeys and humans. The main causative factor of AGS, the lone star tick (Amblyomma americanum), is broadly distributed throughout the east and midwest of the United States and is a vector of a wide range of human and animal pathogens. Our earlier glycomics study of the salivary glands of partially fed male and female ticks revealed relatively high levels of aGal epitopes. In this study, we found that partially fed males of A. americanum on bovine blood, which engage in multiple intrastadial feedings, carry a large amount of aGal in the salivary glands. In our current work, we aimed to test whether ticks mediate the transmission of the aGal sensitizer acquired from nonhuman blood to humans in the intrastadial host switch (referred to as the "transmission" hypothesis). To test this hypothesis, we used an alpha-galactosyltransferase knockout mutant mouse (aGT-KO) model system infested with ticks that were unfed or partially fed on bovine blood. Based on the levels of total IgE and specific IgG and IgE antibodies against aGal after tick feedings, aGT-KO mice significantly responded to tick feeding and injection of aGal (Galα1-3Galβ1-4GlcNAc) conjugated to human serum albumin or mouse serum albumin (aGal-HSA or aGal-MSA) by increasing total IgE and aGal-specific IgE levels compared to those in C57BL/6 control mice. All of the treatments of aGT-KO mice involving the feeding of partially fed and unfed ticks functioned as sensitizers that increased the levels of specific IgE against aGal, with large individual variations. The data in this study do not support the "transmission" component of AGS, although they confirmed that aGT-KO mice can be used as a model for RMA studies.
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Suzin A, da Silva Rodrigues V, Nascimento Ramos VD, Szabó MPJ. Comparing scapular morphology of Amblyomma sculptum and Amblyomma dubitatum nymphs allows a fast and practical differential diagnosis of ticks in highly infested areas with dominance of these two species. EXPERIMENTAL & APPLIED ACAROLOGY 2022; 86:455-463. [PMID: 35235094 DOI: 10.1007/s10493-022-00702-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 02/15/2022] [Indexed: 06/14/2023]
Abstract
Rickettsia rickettsii infection causes the highest human fatality rate among all Rickettsia species of the world and is endemic in Southeast Brazil. In this part of the country most human spotted fever cases are related to unnaturally high populations of ticks, usually a mix of two species, Amblyomma dubitatum Neumann and Amblyomma sculptum Berlese and their local host, capybara (Hydrochoerus hydrochaeris). At the same time, an increase in the number of SF notifications as well as its urbanization was observed, and a better characterization of disease epidemiology is mandatory for control measures and to halt its expansion. It was recently noticed in southeast Brazil that SF endemic areas were characterized by overgrowth populations of A. sculptum and decreased populations of A. dubitatum. Hence, characterization of areas with potential to endemicity, eco-epidemiological studies and control measures may rely on the evaluation of A. sculptum/A. dubitatum rate. However, in potentially endemic scenarios, discriminating the two tick species, particularly the nymphs considered the main vector stage, is a challenge in face of several hundreds to thousands of ticks that should be examined for quantitative studies. We herein present additional morphological features to an existing identification key for Amblyomma nymphs that considerably diminishes the labor to distinguish nymphs of these two tick species. Specifically, the oval-shaped scutum of A. dubitatum and a conspicuous scapula of A. sculptum are prominent discriminating features.
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Whitlow AM, Cumbie AN, Eastwood G. Pathogen prevalence in Amblyomma americanum and Ixodes scapularis ticks from central Appalachian Virginia, U.S.A. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2022; 47:51-60. [PMID: 35366679 DOI: 10.52707/1081-1710-47.1.51] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 01/25/2022] [Indexed: 06/14/2023]
Abstract
Ticks are known vectors of several viral, bacterial, and protozoal pathogens that cause disease in both humans and animals. While pathogen prevalence has been studied extensively in other portions of the United States, pathogen surveillance studies within tick populations in the central Appalachian region of Virginia is almost nonexistent. Two prominent species in this region are Ixodes scapularis (the blacklegged tick) and Amblyomma americanum (the lone star tick). In this study, we collected ticks biweekly from three habitat types (forest, urban, and pasture) across eight counties in southwest Virginia from June, 2019-November, 2020. Ixodes scapularis and A. americanum captures were screened for evidence of associated tick-borne pathogens. In this region, Borrelia burgdorferi sensu stricto (15.3% in nymphs and 37.6% in adults), Anaplasma phagocytophilum (1.9% in nymphs and 12.2% in adults), and Borrelia miyamotoi (2.97% in nymphs and 2.33% in adults) were detected in I. scapularis ticks. Aside from two previously reported Powassan-positive I. scapularis ticks from Floyd County, VA, no additional Powassan-positive ticks are reported here. No evidence of Ehrlichia chaffeensis, Heartland virus (HRTV), or Bourbon virus (BRBV) was detected in collected A. americanum. Detection and confirmation of multiple emerging tick-borne pathogens in this region raises an increased concern for public health risk, calling for heightened awareness of tick-borne pathogen transmission and increased tick surveillance in understudied areas.
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98
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Mazhetese E, Lukanji Z, Byaruhanga C, Neves L, Morar-Leather D. Rickettsia africae infection rates and transovarial transmission in Amblyomma hebraeum ticks in Mnisi, Bushbuckridge, South Africa. EXPERIMENTAL & APPLIED ACAROLOGY 2022; 86:407-418. [PMID: 35212871 DOI: 10.1007/s10493-022-00696-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Accepted: 01/25/2022] [Indexed: 06/14/2023]
Abstract
Rickettsia africae is a gram-negative bacterium, which causes African tick bite fever (ATBF) in humans. ATBF is a febrile disease mainly affecting travellers to southern Africa. This bacterium is known to be transmitted by Amblyomma hebraeum and Amblyomma variegatum ticks. In southern Africa, the principal vector is A. hebraeum. Febrile disease is a serious issue in the study area. There is a high prevalence of non-malaria illness caused by Rickettsia, so there is a need to have more knowledge on these species. Infection rates and transovarial transmission efficiency of R. africae in A. hebraeum ticks were investigated in a rural area of Mpumalanga province, South Africa. Adult and engorged A. hebraeum female ticks were collected from cattle. Larvae were collected by dragging a cloth at ground level using 100 steps, equivalent to an area of 100 m2. Tick identification was performed according to standard taxonomic keys using a microscope. Engorged ticks were incubated to oviposit and egg masses were collected. DNA was extracted from the ticks, larvae and egg masses, and screened for gltA and ompA genes, using quantitative real-time PCR and conventional PCR, respectively. Positive ompA amplicons were sequenced and phylogenetic analysis showed 99.8-100% identity with R. africae. Infection rates were 13.7 and 12.7% for adults and larvae, respectively. Transovarial transmission of R. africae in A. hebraeum from this study was 85.7%. The results provide a clear indication that people living in the study area and travellers that visit the area are at risk of contracting ATBF.
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Wojan C, Thrasher T, Lacey E, Clay K. Distribution, Dynamics, and Diversity of Questing Ticks in the Lower Midwest. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:273-282. [PMID: 34516648 DOI: 10.1093/jme/tjab155] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Indexed: 06/13/2023]
Abstract
We investigated the spatiotemporal patterns of medically important tick species in southcentral Indiana in 2018 and 2019. In recent decades, both Amblyomma americanum (Acari: Ixodidae) (Linnaeus) and Ixodes scapularis (Acari: Ixodidae) (Say) have been expanding their ranges into the Midwest. We report updates to the status of A. americanum, I. scapularis, and Dermacentor variabilis (Acari: Ixodidae) (Say) across 13 counties in southern and south-central Indiana. We found more northerly establishment of A. americanum and more widespread establishment of I. scapularis than previously reported in the literature. We also provide the first report of Amblyomma maculatum (Acari: Ixodidae) (Koch) in Indiana. Using negative binomial regression, we observed significant spatial variation among sampling sites in A. americanum adults and nymphs, D. variabilis adults, and I. scapularis nymphs. Further, we found higher densities of A. americanum nymphs and I. scapularis adults in more forested areas as opposed to less forested, more developed areas. We did not find significant interannual variation in tick densities for any species. More southern sites featured higher densities of A. americanum adults and nymphs, D. variabilis adults, and I. scapularis nymphs than more northern sites. Seasonally, we observed the highest peaks in tick activity in the spring and early summer, but I. scapularis adults were most common in the early spring and fall. Average adult A. americanum and adult D. variabilis densities were positively correlated at our sites. Our results reflect the northward expansion of A. americanum in the Lower Midwest, as well as the increasing geographic prevalence of I. scapularis in the region.
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Yang TS, Reichard MV, Marr HS, Cohn LA, Nafe L, Whitehurst N, Birkenheuer AJ. Direct injection of Amblyomma americanum ticks with Cytauxzoon felis. Ticks Tick Borne Dis 2022; 13:101847. [PMID: 34673404 PMCID: PMC10658644 DOI: 10.1016/j.ttbdis.2021.101847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 09/02/2021] [Accepted: 10/03/2021] [Indexed: 10/20/2022]
Abstract
Cytauxzoon felis is a tick-borne hemoprotozoan parasite that causes life-threatening disease in domestic cats in the United States. Currently, the platforms for C. felis research are limited to natural or experimental infection of domestic cats. This study aims to develop an alternative model by infecting Amblyomma americanum ticks with C. felis via direct injection. Amblyomma americanum adults were injected with C. felis-infected feline erythrocytes through two routes: directly into the digestive tract through the anal pore (IA injection), or percutaneously into the tick hemocoel (IH injection). RNAscope® in situ hybridization (ISH) was used to visualize the parasites within the ticks at different time points after injection. Four months after injection, ticks were divided into 3 infestation groups based on injection methods and inoculum type and fed on 3 naïve cats to assess the ticks' ability to transmit C. felis. Prior to the transmission challenge, selected ticks from each infestation group were tested for C. felis RNA via reverse transcription-PCR (RT-PCR). In both IA- and IH-injected ticks, ISH signals were observed in ticks up to 3 weeks after injection. The number of hybridization signals notably decreased over time, and no signals were detected by 4 months after injection. Prior to the transmission challenge, 37-57% of the sampled ticks were positive for C. felis RNA via RT-PCR. While the majority of injected ticks successfully attached and fed to repletion on all 3 cats during the transmission challenge, none of the cats became infected with C. felis. These results suggest that injected C. felis remained alive in ticks but was unable to progress to infective sporozoites after injection. It is unclear why this infection technique had been successful for other closely related tick-borne hemoprotozoa and not for C. felis. This outcome may be associated with uncharacterized differences in the C. felis life cycle, the lack of the feeding or molting in our model or absence of gametocytes in the inoculum. Nonetheless, our study demonstrated the potential of using ticks as an alternative model to study C. felis. Future improvement of a tick model for C. felis should consider other tick species for the injection model or utilize infection methods that more closely emulate the natural infection process.
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