Crimean-Congo hemorrhagic fever virus in ticks collected from humans, livestock, and picnic sites in the hyperendemic region of Turkey

During June and July 2007, about 3125 adult ticks were collected from humans, animals, and vegetation in a hyperendemic region (Sivas and Tokat) of Turkey. A total of 2193 ticks were pooled in 225 pools and screened for the Crimean Congo hemorrhagic fever virus (CCHFV) presence by antigen-capture enzyme-linked immunosorbent assay. Infection rates were calculated as the maximum likelihood estimation with 95% confidence intervals (CI). The dominant tick species was found to be Hyalomma marginatum with the following infestation rates in human, cattle and sheep, respectively: 47.43%, 66.07%, and 30.12%. Maximum likelihood estimation values of CCHFV in H. marginatum ticks collected from human, cattle, and sheep were 0.91% (CI 0.05-4.42), 2.10% (CI 1.12-3.64), and 3.11% (CI 1.18-6.87), respectively. CCHFV antigens were also demonstrated in Hyalomma excavatum, Haemaphysalis parva, and Boophilus annulatus ticks collected from cattle and Rhipicephalus bursa ticks from sheep. Our results suggest that the studied area might maintain its endemic properties in the near future unless effective tick control measures are implemented.     

Seroprevalence of crimean congo hemorrhagic Fever virus in ijara district, kenya

Abstract Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease mainly affecting pastoralists who come in contact with animals infested with Hyalomma ticks, which are the key vectors of CCHF virus (CCHFV). CCHFV has been detected among these ticks in parts of North Eastern Kenya. This study aimed to identify acute cases of CCHF, and to determine the extent of previous exposure to CCHFV in an outpatient population attending Sangailu and Ijara health centers, Ijara District, North Eastern Kenya, presenting with acute febrile illnesses. A total of 517 human serum samples were collected from these patients. The samples were screened for the presence of IgM and IgG antibodies to CCHF using CCCHF-IgG and IgM ELISA test kits. A multivariable logistic regression model was used to investigate the risk factors associated with evidence of exposure to CCHFV. A single patient tested positive for anti-CCHF IgM, while 96 were positive for anti-CCHF IgG. The seroprevalence of CCHFV was 23% in Sangailu and 14% in Ijara. Most exposed persons were aged 40-49 years. The likelihood of exposure was highest among farmers (29%). Age, location, and contact with donkeys were significantly associated with exposure to CCHFV. Acute CCHFV infections could be occurring without being detected in this population. This study confirms human exposure to CCHF virus in Ijara District, Kenya, and identifies several significant risk factors associated with exposure to CCHFV.     

Viral RNA Metagenomics of Hyalomma Ticks Collected from Dromedary Camels in Makkah Province,Saudi Arabia

Arthropod-borne infections are a medical and economic threat to humans and livestock. Over the last three decades, several unprecedented viral outbreaks have been recorded in the Western part of the Arabian Peninsula. However, little is known about the circulation and diversity of arthropod-borne viruses in this region. To prepare for new outbreaks of vector-borne diseases, it is important to detect which viruses circulate in each vector population. In this study, we used a metagenomics approach to characterize the RNA virome of ticks infesting dromedary camels (Camelus dromedaries) in Makkah province, Saudi Arabia. Two hundred ticks of species Hyalomma dromedarii (n = 196) and Hyalomma impeltatum (n = 4) were collected from the Alkhurma district in Jeddah and Al-Taif city. Virome analysis showed the presence of several tick-specific viruses and tick-borne viruses associated with severe illness in humans. Some were identified for the first time in the Arabian Peninsula. The human disease-associated viruses detected included Crimean Congo Hemorrhagic fever virus and Tamdy virus (family Nairoviridae), Guertu virus (family Phenuiviridae), and a novel coltivirus that shares similarities with Tarumizu virus, Tai forest reovirus and Kundal virus (family Reoviridae). Furthermore, Alkhurma hemorrhagic virus (Flaviviridae) was detected in two tick pools by specific qPCR. In addition, tick-specific viruses in families Phenuiviridae (phleboviruses), Iflaviridae, Chuviridae, Totiviridae and Flaviviridae (Pestivirus) were detected. The presence of human pathogenetic viruses warrants further efforts in tick surveillance, xenosurveillence, vector control, and sero-epidemiological investigations in human and animal populations to predict, contain and mitigate future outbreaks in the region.     

Tick cell lines for study of Crimean-Congo hemorrhagic fever virus and other arboviruses

Continuous cell lines derived from many of the vectors of tick-borne arboviruses of medical and veterinary importance are now available. Their role as tools in arbovirus research to date is reviewed and their potential application in studies of tick cell responses to virus infection is explored, by comparison with recent progress in understanding mosquito immunity to arbovirus infection. A preliminary study of propagation of the human pathogen Crimean-Congo hemorrhagic fever virus (CCHFV) in tick cell lines is reported; CCHFV replicated in seven cell lines derived from the ticks Hyalomma anatolicum (a known vector), Amblyomma variegatum, Rhipicephalus (Boophilus) decoloratus, Rhipicephalus (Boophilus) microplus, and Ixodes ricinus, but not in three cell lines derived from Rhipicephalus appendiculatus and Ornithodoros moubata. This indicates that tick cell lines can be used to study growth of CCHFV in arthropod cells and that there may be species-specific restriction in permissive CCHFV infection at the cellular level.     

Crimean-Congo hemorrhagic fever in European part of Turkey: genetic analysis of the virus strains from ticks and a seroepidemiological study in humans

A survey of ticks from domestic ruminants, together with a serosurvey in humans was conducted in Thrace (northwestern Turkey) to evaluate the prevalence of Crimean-Congo hemorrhagic fever virus (CCHFV) in ticks and humans. More prevalent ticks were Hyalomma marginatum, Hyalomma aegyptium, Rhipicephalus bursa, and Rhipicephalus (Boophilus) annulatus, with low numbers of Dermacentor marginatus, Rhipicephalus sanguineus group, and Ixodes ricinus. No differences in the tick faunal composition were found among surveyed provinces. CCHFV was detected using specific primers for strains belonging to both Europe 1 and Europe 2 clades in a total of 15 pools of ticks collected in nine localities. The maximum likelihood estimate of infection rate was calculated as 0.72/100 ticks (95% CI?=?0.42-1.16). Viral RNA was observed only in H. marginatum, R.(B.) annulatus, and R. bursa with overall maximum likelihood estimate infection rates being 0.93 (95% CI?=?0.35-2.05), 0.74 (95% CI?=?0.24-1.78), and 1.67 (95% CI?=?0.69-3.46), respectively. The surveyed region is the only place where both viral strains are circulating together in nature in Turkey. Results from serosurvey on 193 samples from three localities in the region showed that immunoglobulin M and immunoglobulin G rates are compatible with an epidemiological situation in which the virus has been present for a long time and is not the result of a recent invasive event from the main epidemic center in Anatolia (north-central Turkey). Seropositivity rates cannot be compared against the tick faunal composition, because of the homogeneity in the results about tick surveys. The high rate of seropositivity, and the prevalence of CCHFV in both Europe 1 and 2 clades among the ticks, but few clinical cases suggest that the circulation of both viral strains may confer protection against the CCHFV infection.     

新疆克拉玛依地区蜱媒病原体的调查

目的 调查新疆克拉玛依地区蜱种类及其携带病原体。方法 于克拉玛依市不同区采集游离蜱和寄生蜱,鉴定蜱种类,利用荧光定量PCR或套氏PCR/半套氏PCR检测发热伴血小板减少综合征布尼亚病毒、斑点热群立克次体、克里米亚-刚果出血热病毒、蜱传脑炎病毒、巴贝斯虫/泰勒虫、贝氏立克次体、查菲埃立克次体、恙虫病东方体和伯氏疏螺旋体等9种病原体。结果 共采集蜱683只,分3属3种,其中亚东璃眼蜱数量(n=362)最多,其次为银盾革蜱(n=311)、图兰扇头蜱(n=10)。银盾革蜱中斑点热群立克次体的阳性率为3.2%(10/311),巴贝斯虫的阳性率为1.0%(3/311);亚东璃眼蜱中巴贝斯虫的阳性率为0.8%(3/362),泰勒虫阳性率为0.3%(1/362);其他病原体检测结果均呈阴性。PCR扩增阳性基因序列分析显示银盾革蜱携斑点热群立克次体阳性与劳氏立克次体最相关,银盾革蜱和亚东璃眼蜱携带驽巴贝斯虫。结论 新疆克拉玛依地区优势蜱为亚东璃眼蜱和银盾革蜱,银盾革蜱携带劳氏立克次体,银盾革蜱和亚东璃眼蜱携带驽巴贝斯虫,提示该地区存在斑点热、巴贝斯虫病的自然疫源地,因此有必要加强对这些蜱携疾病的防控。     

Genomic Characterization of Yogue,Kasokero, Issyk-Kul,Keterah, Gossas,and Thiafora Viruses: Nairoviruses Naturally Infecting Bats,Shrews, and Ticks

The genus Nairovirus of arthropod-borne bunyaviruses includes the important emerging human pathogen, Crimean–Congo hemorrhagic fever virus (CCHFV), as well as Nairobi sheep disease virus and many other poorly described viruses isolated from mammals, birds, and ticks. Here, we report genome sequence analysis of six nairoviruses: Thiafora virus (TFAV) that was isolated from a shrew in Senegal; Yogue (YOGV), Kasokero (KKOV), and Gossas (GOSV) viruses isolated from bats in Senegal and Uganda; Issyk-Kul virus (IKV) isolated from bats in Kyrgyzstan; and Keterah virus (KTRV) isolated from ticks infesting a bat in Malaysia. The S, M, and L genome segments of each virus were found to encode proteins corresponding to the nucleoprotein, polyglycoprotein, and polymerase protein of CCHFV. However, as observed in Leopards Hill virus (LPHV) and Erve virus (ERVV), polyglycoproteins encoded in the M segment lack sequences encoding the double-membrane-spanning CCHFV NSm protein. Amino acid sequence identities, complement-fixation tests, and phylogenetic analysis indicated that these viruses cluster into three groups comprising KKOV, YOGV, and LPHV from bats of the suborder Yingochiroptera; KTRV, IKV, and GOSV from bats of the suborder Yangochiroptera; and TFAV and ERVV from shrews (Soricomorpha: Soricidae). This reflects clade-specific host and vector associations that extend across the genus.     

Serological evaluation of crimean-congo hemorrhagic Fever in humans with high-risk professions living in enzootic regions of isfahan province of iran and genetic analysis of circulating strains

Abstract Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic viral disease that is asymptomatic in infected livestock, but causes a serious threat to humans with a mortality rate up to 50%. Although the CCHF virus (CCHFV) is often transmitted by ticks, livestock-to-human and human-to-human transmission also occurs. In the current study, we focused on CCHF in the province of Isfahan, located in the center of Iran and deemed to be the second most infected province. Human and livestock sera and resident ticks in the livestock are collected from different regions of the province and analyzed with specific IgG ELISA and RT-PCR tests. Overall, 12% and 12.7% of studied human and livestock populations were IgG positive, respectively. The genome of CCHFV was detected in 9% of ticks resident in livestock involved in this survey. The CCHFV isolates from infected ticks were genetically examined. Nucleotide sequence of the S-segment revealed that the different isolates were closely related to each other, with nucleotide sequence identities higher than 98%. Phylogenetic analysis demonstrated that a variant isolate clustered with the Iraq strain. This high proportion of IgG-positive sera and nearly high proportion of infected ticks increases the risk of CCHF outbreaks in the province and probably posits a great danger to other provinces.     

Epidemiology of ixodid ticks in cattle population of various agro-climatic zones of Punjab,India

ObjectiveTo determine the epidemiology of ixodid ticks in bovines of different agro-climatic zones of Punjab state, India.MethodsA total of 4 459 cattle of all age groups and sex were examined from eighteen districts of five major agro-climatic zones of Punjab state, India.ResultsThe overall prevalence of ixodid ticks, Rhipicephalus microplus (R. microplus), Hyalomma anatolicum anatolicum (H. a. anatolicum) and mixed infestation were 58.06%, 50.16%, 11.34% and 3.45%, respectively. Among the various agro-climatic zones highest prevalence rate of R. microplus and H. a. anatolicum were recorded in submountain undulating region (79.36%) and western region (20.40%), respectively indicating that R. microplus prefers a hot and humid environment whereas, arid and semi arid conditions suit better for H. a. anatolicum. The overall prevalence of ixodid ticks was highest in monsoon season (83.74%), followed by summer (69.01%) and least in winters (31.64%) and a significant variation (P<0.01) was also observed; whereas, maximum prevalence of R. microplus and H. a. anatolicum were recorded in monsoon (72.42%) and summers (18.06%), respectively. Among the various age groups maximum tick infestation was recorded in calves <6 months of age (72.59%), followed by 6 months -1 year age group (61.74%) and least in >1year age group (55.02%) and the difference was statistically significant (P<0.01). Also a significantly higher (P<0.01) infestation rates of ixodid ticks was observed in males.ConclusionsThe findings of the current study would provide a basis for evolving effective control strategy for the management of ticks in bovines of the region.     

Investigation of Borrelia spp. in ticks (Acari: Ixodidae) at the border crossings between China and Russia in Heilongjiang Province, China

ObjectiveTo investigate the precise species of tick vector and the Borrelia spirochete pathogen at the Heilongjiang Province international border with Russia.MethodsIn this study, ticks were collected from 12 Heilongjiang border crossings (including grasslands, shrublands, forests, and plantantions) to determine the rate and species type of spirochete-infected ticks and the most prevalent spirochete genotypes.ResultsThe ticks represented three genera and four species of the Ixodidae family [Ixodes persulcatus, Dermacentor silvarum, Haemaphysalis concinna and Haemaphysalis japonica]. Ixodes persulcatus had the highest amount of Borrelia burgdorferi sensu lato infection of 25.6% and the most common species of Borrelia isolated from Ixodes persulcatus was Borrelia garinii, strain PD91.ConclusionsOur results suggest that Borrelia garinii PD91-infected Ixodes persulcatus may be the principal cause of Lyme disease in the border crossing areas of Heilongjiang Province.     

Ixodidae ticks in Bishkek

The fauna of Ixodidae ticks was studied in Bishkek in 1998-2004. The city is situated in the center of the Chuisk valley, at the foot of the Kirghiz ridge, at the boundary of a submountain-plain-arid region and a plain-piedmont-semiarid one with steppe fragments. The ticks were gathered on a flag from small mammalians caught by Gero traps, from birds, domestic and agricultural animals. A total of 648 animals of 13 species were examined. The bites of ticks were registered in 98 persons in the city. A total of 1085 ticks of all developmental phases were gathered. The faunal complex of Ixodidae ticks was represented by the following species: Ixodes persulcatus Sch (domination index (DI) = 0.45), Haemaphysalis punctata Can. Et Fanz (DI = 21.93), Haemaphysalis erinacei Paves (DI = 1.0), Dermacentor marginatus Sulter (DI = 0.27), Rhipicephaluspumilio Sch. (DI = 0.84), Rhipicephalus sanguineus Latr. (DI = 0.56), Rhipicephalus turanicus Pom (DI = 74.85), Hyalomma anatolicum Koch (DI = 0.87). The regional and climatic conditions of Bishkek and the presence of profeeders in the private sector (domestic and agricultural animals, synanthropic rodents, and birds) favor the existence of the R. turanicus population. The mosaic pattern of a cultural region in the center of the city permits small populations of several species of ticks to exist.     

Laboratory Biosafety: Sentinel surveillance of Lyme disease risk in Canada, 2019: Results from the first year of the Canadian Lyme Sentinel Network (CaLSeN)

BackgroundLyme disease is an emerging vector-borne zoonotic disease of increasing public health importance in Canada. As part of its mandate, the Canadian Lyme Disease Research Network (CLyDRN) launched a pan-Canadian sentinel surveillance initiative, the Canadian Lyme Sentinel Network (CaLSeN), in 2019.ObjectivesTo create a standardized, national sentinel surveillance network providing a real-time portrait of the evolving environmental risk of Lyme disease in each province.MethodsA multicriteria decision analysis (MCDA) approach was used in the selection of sentinel regions. Within each sentinel region, a systematic drag sampling protocol was performed in selected sampling sites. Ticks collected during these active surveillance visits were identified to species, and Ixodes spp. ticks were tested for infection with Borrelia burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, Babesia microti and Powassan virus.ResultsIn 2019, a total of 567 Ixodes spp. ticks (I. scapularis [n=550]; I. pacificus [n=10]; and I. angustus [n=7]) were collected in seven provinces: British Columbia, Manitoba, Ontario, Québec, New Brunswick, Nova Scotia and Prince Edward Island. The highest mean tick densities (nymphs/100 m²) were found in sentinel regions of Lunenburg (0.45), Montréal (0.43) and Granby (0.38). Overall, the Borrelia burgdorferi prevalence in ticks was 25.2% (0%–45.0%). One I. angustus nymph from British Columbia was positive for Babesia microti, a first for the province. The deer tick lineage of Powassan virus was detected in one adult I. scapularis in Nova Scotia.ConclusionCaLSeN provides the first coordinated national active surveillance initiative for tick-borne disease in Canada. Through multidisciplinary collaborations between experts in each province, the pilot year was successful in establishing a baseline for Lyme disease risk across the country, allowing future trends to be detected and studied.     

The fractions, functions, methods of isolation and the significance for transmission of causative agents of the saliva of ixodid ticks

The authors present a review on the structure and functions of salivary glands of the Ixodidae ticks, attaching to the host's skin by means of a cement fraction: current ideas on the neurohormonal regulation of salivary function are presented. The method of obtaining various saliva fractions--cement-containing and liquid--from unfed infected ticks belonging to 3 genera (Hyalomma, Dermacentor and Ixodes)--by parenteral administration of secretotropic substances is described. The first portions of saliva, both liquid and cement-forming, are shown to contain tick-borne encephalitis viruses in amounts sufficient for the infection of animals. Epidemiological value of the presence of viruses in the cement cork formed in the host's skin and in the first portion of liquid saliva is discussed.     

Occurrence and Genotyping of Coxiella burnetii in Ixodid Ticks in Oromia,Ethiopia

This study was conducted from September 2011 to March 2014 to address the occurrence and genotypes of Coxiella burnetii using molecular methods in ticks collected from domestic animals in Ethiopia. Ticks were tested for C. burnetii by quantitative real-time polymerase chain reaction (qPCR) targeting two different genes followed by multispacer sequence typing (MST). An overall prevalence of 6.4% (54/842) of C. burnetii was recorded. C. burnetii was detected in 28.6% (14/49) of Amblyomma gemma, 25% (31/124) of Rhipicephalus pulchellus, 7.1% (1/14) of Hyalomma marginatum rufipes, 3.2% (2/62) of Am. variegatum, 3.1% (4/128) of Am. cohaerens, 1.6% (1/63) of Rh. praetextatus, and 0.6% (1/153) of Rhipicephalus (Boophilus) decoloratus. Significantly higher overall frequencies of C. burnetii DNA were observed in Am. gemma and Rh. pulchellus than in other tick species (Mantel–Haenszel [MH], P < 0.0001). The overall frequency of C. burnetii was significantly higher (MH, P < 0.0001) in ticks from southeastern districts (Arero, Moyale, and Yabelo) than that from other districts. This study demonstrated the presence of C. burnetii genotype MST 18 in ticks in southeastern districts and genotype MST 20 in ticks in central districts. This study highlights the importance of ticks in the epidemiology of C. burnetii in Ethiopia.     

Survey of tick species parasiting domestic ruminants in Ghaemshahr county,Mazandaran province,Iran

ObjectiveTo determine the tick species parasitizing domestic ruminants in Ghaemshahr county in Mazandaran, a Caspian province in the north of Iran.MethodsAbout 361 sheep, 54 goats and 10 cattle of 18 herds in several villages in Ghaemshahr were inspected for tick infestation. Separated ticks were preserved in 70% alcohol and identified.ResultsAbout 323 ticks (207 female, 116 male) were collected, the occurrence of ticks on sheep, goats and cattle were 28.3%, 22.2% and 20.0% respectively. The mean number of ticks on each animal was low (3-5 ticks per animal). Rhipicephalus sanguineus, Rhipicephalus bursa, Ixodes ricinus, Boophilus annulatus, Haemaphysalis punctata and Haemaphysalis numidiana were the tick species we found. Rhipicephalus sanguineus were the most abundant species in the study area. The largest number of ticks were generally present from April to July, mostly in animal ears and tails. Ixodes, Boophilus and Haemaphysalis occurred in mountainous areas of Ghaemshahr, whereas Rhipicephalus were present in both mountains and plains of the study area.ConclusionsThe result of this study is a survey of tick species from domestic animals in Iran and implication of possible prevention measures for diseases transmitted by ticks.     

Biochemical characteristics of ticks of the families Argasidae and Ixodidae

Polyacrylamide gel electrophoresis was used to study homogenate supernatants from the bloodsucking ticks (Argasidae and Ixodidae) belonging to 8 different genera and species. Differences were found in the electrophoretic mobility of protein fractions in adult ticks of these two different families and between several genera of Ixodes ticks (such as Haemaphysalis, Hyalomma, Dermacentor, Rhipicephalus and Ixodes). Argasidae ticks were found to have generic and even species-specific differences at the nymphal stage of development. A. lahorensis nymph-3 contained 5 protein fractions; O. papillipes had 2 fractions, and O. moubata had 3 fractions. Electrophoretic protein separation showed the equal number of protein fractions within one genus of ticks. At the larval stage, the tick homogenates were always found to have one protein fraction. The hemolymph of O. papillipes and O. moubata ticks displayed differences between the imago and nymph-3. A new biochemical marker was proposed to establish a species affinity.     

Biology of Dermacentor marginatus (Acari: Ixodidae) under laboratory conditions

ObjectiveTo investigate and survey the biology of Dermacentor marginatus (D. marginatus) under laboratory conditions.MethodsIn this investigation, D. marginatus adult ticks were collected from sheep in Semnan province. Then various developmental stages of D. marginatus including larvae, nymphs and adult males and females under laboratory condition were bred and their biology was scrutinized.ResultsThe requisite time to complete the life cycle of D. marginatus under controlled laboratory conditions for larvae (26 °C, 75% relative humidity) and nymph (26 °C, 95% relative humidity) moulting, was on average 92 d (range 75–104 d), including preoviposition and egg incubation (22.5 d), larvae incubation (20.5 d), nymphal stage (28 d) along with male maturation (21 d). The index of conversion efficiency and the index of reproduction efficiency in females were 0.397 and 8.300, respectively.ConclusionsAlthough in this investigation, there was no meaningful correlation between preoviposition period and the weight of female ticks which were laid successfully. The significant linear relationship was fully observed between the weight of engorged female of D. marginatus and the number of eggs laid. The mean of preoviposition period from 5.4 d in autumn to 34.2 d in spring increased. The minimum weight of ticks with laying capacity was 69 mg and lighter ticks (21 mg) either did not lay or if they did their eggs did not hatch.     

广西地区家畜牛、羊体表硬蜱情况调查及种类鉴定

目的 掌握广西地区牛羊场硬蜱种类及其分子特征,了解该地区蜱类的分类地位,为养殖户防控硬蜱及蜱媒传染病提供参考依据。方法 本实验于2019年1月至2021年11月,采用动物体表法采集寄生的蜱类;提取蜱基因组,PCR扩增3种硬蜱的线粒体16S rDNA和COI基因片段,并进行同源性分析。基于邻接法,用MEGA6.0软件分别构建系统发生树,进行遗传进化分析。结果 牛羊体表上共采集蜱2 030只,隶属1科2属3种,其中微小扇头蜱1 968只,长角血蜱49只,具角血蜱13只。PCR扩增微小扇头蜱、长角血蜱和具角血蜱16S rDNA和COI基因片段长度分别是460 bp和710 bp左右,分别与GenBank中已登录的相应种类相似较高且在一个进化分支上。结论 广西地区牛羊场优势蜱种是微小扇头蜱且存在长角血蜱和具角血蜱。三蜱种16S rDNA和COI序列存在多样性和地域差异性。     

Phylogeny of hard- and soft-tick taxa (Acari: Ixodida) based on mitochondrial 16S rDNA sequences.

Ticks are parasitiform mites that are obligate hematophagous ectoparasites of amphibians, reptiles, birds, and mammals. A phylogeny for tick families, subfamilies, and genera has been described based on morphological characters, life histories, and host associations. To test the existing phylogeny, we sequenced approximately 460 bp from the 3' end of the mitochondrial 16S rRNA gene (rDNA) in 36 hard- and soft-tick species; a mesostigmatid mite, Dermanyssus gallinae, was used as an outgroup. Phylogenies derived using distance, maximum-parsimony, or maximum-likelihood methods were congruent. The existing phylogeny was largely supported with four exceptions. In hard ticks (Ixodidae), members of Haemaphysalinae were monophyletic with the primitive Amblyomminae and members of Hyalomminae grouped within the Rhipicephalinae. In soft ticks (Argasidae), the derived phylogeny failed to support a monophyletic relationship among members of Ornithodorinae and supported placement of Argasinae as basal to the Ixodidae, suggesting that hard ticks may have originated from an Argas-like ancestor. Because most Argas species are obligate bird octoparasites, this result supports earlier suggestions that hard ticks did not evolve until the late Cretaceous.