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PubMed1993

Experimental vector incompetence of a soft tick, Ornithodoros sonrai (Acari: Argasidae), for Crimean-Congo hemorrhagic fever virus.

Adults and nymphs of a soft tick, Ornithodoros sonrai Sautet & Witkowski, were allowed to feed on suckling mice that had been experimentally infected with Crimean-Congo hemorrhagic fever (CCHF) virus (IbAr 10200 strain). The mean viral titer of mouse blood at the time of tick feeding was 10(3.2) plaque-forming units (PFU) per ml. Samples of ticks were assayed on 12 occasions between days 0 and 31 after the viremic blood meal. Mean CCHF viral titers were 10(2.1) PFU per tick immediately after the viremic meal but declined to 10(1.2) PFU per tick after 2 d, and no virus was detected beyond 8 d. The percentage of ticks with detectable virus was 92% (22/24) immediately after the viremic meal, but then declined to 20% (2/10) after 4 d and to 0% (0/44) after 11 or more days. Ticks were allowed to feed on sets of three naive suckling mice on days 0, 2, 5, 8, 11, 14, 21, and 28 after the viremic blood meal, but CCHF viral transmission did not occur. Similarly, no transovarial transmission of virus from CCHF virus-exposed O. sonrai to their progeny was observed. These results strongly indicate that O. sonrai is not a vector of CCHF virus.

Animals↗

PubMed1994

Attempted transovarial and venereal transmission of African swine fever virus by the Iberian soft tick Ornithodoros (Pavlovskyella) marocanus (Acari: Ixodoidea: Argasidae).

Transovarial transmission experiments were conducted with three groups of Ornithodoros (Pavlovskyella) marocanus Velu; one group consisted of 27 pairs of adults that had been fed as larvae on a pig with a viremia of 10(7.4) HAd50/ml of African swine fever virus (ASFV). The second and third groups each consisted of 100 pairs of adults fed on a viremic pig (10(4.5) HAd50/ml) as adults. The first group underwent five gonotrophic cycles over a 554-d period. The second and third groups underwent three and two gonotrophic cycles, respectively. All larvae were fed in individual cohorts on naive pigs and the resulting nymphs were assayed by cohort for ASFV. None of the larvae transmitted ASFV to naive pigs by bite and ASFV was not isolated in swine buffy coat cultures from any cohort of nymphs. Therefore, O. marocanus does not exhibit transovarial transmission of ASFV. Venereal transmission experiments were conducted with pairs of O. marocanus in which either the female (100 pairs) or the male (100 pairs), respectively, had fed on a viremic pig (10(4.5) HAd50/ml). Both groups underwent at least two gonotrophic cycles over a 470-d period, were sampled periodically for the presence of ASFV, and the progeny were tested for the presence of ASFV. Venereal transmission from male to female occurred in 10% (1/10) of O. marocanus after the first gonotrophic cycle, but not after the second or third gonotrophic cycle, and transovarian transmission in these groups was not observed. Venereal transmission from infected females to uninfected males did not occur. ASFV persisted through five gonotrophic cycles over a 554-d period in 30% of adults fed on a viremic pig as larvae. ASFV was cleared during three gonotrophic cycles within a year from nearly all ticks fed on a viremic pig as adults. Virus-induced mortality rats of 12-80% occurred among ticks fed on viremic animals, whereas, no mortality was seen in ticks fed on uninfected animals. ASFV infection in ticks did not effect feeding frequency, egg-hatch rate, or the oviposition rate among females fed on a viremic pig as adults. The oviposition rate for females fed on a viremic pig as larvae was reduced by 63.4%. Parthenogenesis was not observed among O. marocanus. The mean gonotrophic cycle duration for pig-fed O. marocanus at 27 degree C was 19.8 d and the mean fecundity was 88.3 +/- 17.9 eggs/female/gonotrophic cycle.

African Swine Fever↗

PubMed1994

Correlation between ecdysteroids and cuticulogenesis in nymphs of the tick Ornithodoros parkeri (Acari: Argasidae).

Ecdysteroids and cuticulogenesis were studied in third-instar nymphs of the tick Ornithodoros parkeri Cooley. Ecdysteroid titer increases slightly during the postfeeding intermolt period, which correlates with the deposition of additional procuticle lamellae. The titer increases at the time of apolysis, peaks at the time of epicuticle deposition, and then drops to a low but detectable level from the time of procuticle deposition until after ecdysis. Ecdysone and 20-hydroxyecdysone are the two major ecdysteroids present during the postfeeding intermolt period and the period of epicuticle deposition. After ecdysis, the ecdysteroid immunoreactive material is composed principally of an unknown compound more polar than 20,26-dihydroxyecdysone and is found only in the midgut. This compound is possibly a metabolite of ecdysteroids left over from the previous instar.

Animals↗

PubMed1995

Life cycle of Ornithodoros (Alectorobius) talaje (Acari: Argasidae) in laboratory.

Specimens of Ornithodoros (Alectorobius) talaje (Guérin-Mèneville) collected in the state of Minas Gerais, Brazil, were used to start a laboratory colony. Larvae were fed on chicks and nymphs and adults were fed on adult chickens. From the specimens that emerged after the third molt, 97.6% were nymphs and 2.4% were males. After the fourth molt, 41.6% were nymphs, 37.6% were males, and 20.8% were females. After the fifth molt, 24% were males and 60% were females; the remainder were nymphs. The number of eggs per female per gonotrophic cycle and the mean duration of preoviposition, oviposition, and incubation periods were recorded. At the first gonotrophic cycle, duration of preoviposition period was longer and the number of eggs was smaller than any other studied gonotrophic cycle. The life cycle was completed within 849 d (maximum). The O. (A.) talaje first-instar nymphal population failed to molt without having a blood meal, which differs from other Alectorobius species. Parthenogenesis was not observed. Larval morphology was studied by optical microscopy. Unengorged specimens were larger, with smaller dorsal plate and fewer dorsal setae than those previously described.

Animals↗

PubMed1997

Experimental infestation of Gallus gallus with Ornithodoros (Alectorobius) amblus (Ixodoidea: Argasidae).

Ornithodoros (Alectorobius) amblus Chamberlin 1920 specimens were collected from a seagull (Larus spp.) nest in northern Chile. This reports the occurrence of this species outside Peru. The biology of 79 specimens reared under laboratory conditions at 27 degrees C, 75-80% RH, and total darkness was determined. A 13% mortality rate from larval to adult was observed. Larval ticks were fed on chicks, Gallus gallus domesticus; and nymphs and adults were fed on chickens. We recorded the number of eggs per female per gonotrophic cycle and the mean duration of the periods of preoviposition, oviposition, and incubation. The total duration of their life cycle ranged from 111 to 239 d, depending on the number of molts. Males were found after the 4th molt, and after the 5th molt the proportion of females was greater than that of males or remaining nymphs. The feeding period of larvae was 4-6 d, N1 nymphs do not feed. The N2-N6 nymphs, males and females, had a 10- to 60-min feeding period. From N2 on, there was emission of coxal fluid while on the host and during or immediately after feeding.

Animals↗

PubMed2002

Evolution of hematophagy in ticks: common origins for blood coagulation and platelet aggregation inhibitors from soft ticks of the genus Ornithodoros.

Identification and characterization of antihemostatic components from hematophagous organisms are useful for the elucidation of the evolutionary mechanisms involved in adaptation to a highly complex host hemostatic system. Although many bioactive components involved in the regulation of the host's hemostatic system have been described, the evolutionary mechanisms of how arthropods adapted to a blood-feeding environment have not been elucidated. This study describes common origins of both blood coagulation inhibitors and platelet aggregation inhibitors (PAIs) from soft ticks of the genus Ornithodoros. Neighbor-joining analysis indicates that fXa, thrombin, and PAIs share a common ancestor. Maximum parsimony analysis and a phylogeny based on root mean square deviation values of alpha-carbon backbone structures suggest a novel evolutionary pathway by which different antihemostatic functions have evolved through a series of paralogous gene duplication events. In this scenario, the thrombin inhibitors preceded the fXa and PAIs. This evolutionary model explains why the tick serine protease inhibitors have inhibition mechanisms that differ from that of the canonical bovine pancreatic trypsin inhibitor (BPTI)-like inhibitors. Higher nonsynonymous-to-synonymous substitution rates indicate positive Darwinian selection for the fXa and PAIs. Comparison with hemostatic inhibitors of hard ticks suggests that the two main tick families have independently evolved novel antihemostatic mechanisms. Independent evolution of these mechanisms in ticks points to a rapid divergence between tick families that could be dated between 120 and 92 MYA. This coincides with current molecular phylogeny views on the early divergence of modern birds and placental mammals in the Late Cretaceous, which suggests that this event might have been a driving force in the evolution of hematophagy in ticks.

Amino Acid Sequence↗

PubMed1993

Evaluation of mechanical transmission of HIV by the African soft tick, Ornithodoros moubata.

OBJECTIVES: To assess the ability of the African Hut Tampan, Ornithodoros moubata, to mechanically transmit HIV-1 and to re-appraise HIV-1 infectivity in an arthropod cell line at 28 and 35 degrees C. DESIGN: To evaluate HIV-1 transmission by O. moubata, as determined by HIV-1 survival, 'blood-meal' size and interval between feeds, various tick developmental stages were allowed to feed on a heavily infected lymphoblast-rich blood-meal containing HIV-1BRU in an in vitro feeding chamber. METHODS: Blood-meal regurgitation was evaluated using 51Cr-labelled human erythrocytes, and human lymphoblast survival in ticks using Trypan blue. HIV-1 survival in ticks was evaluated by reverse transcriptase activity in tick homogenates cocultured with CEM lymphoblasts. Polymerase chain reaction and Southern blot analysis were used to detect proviral HIV-1 in arthropod cells in vitro. RESULTS: HIV-1BRU remained viable for up to 10 days with O. moubata adults. This is the longest recorded survival of HIV in an arthropod. In agreement with other studies. O. moubata regurgitated part of its previous blood-meal into the feeding lesion. Human CEM lymphoblasts partially survived for up to 7 days at 28 and 35 degrees C inside O. moubata's digestive tract. The blood-meal of adult female ticks was as high as 240 microliters (approximately 70 times more than a mosquito), while the most likely potential mechanical vectors (fourth- and fifth-stage nymphs) ingested an average of 39 microliters (maximum, 73 microliters), with some ticks re-feeding as early as 14 days postfeed in the absence of a moult. Shortcomings associated with the experimental protocol suggest that HIV survival within O. moubata may reach 14 days following natural infection, or that ticks might re-feed earlier. Although HIV-1BRU and HIV-1NDK were unable to replicate at 28 and 35 degrees C in CD4- Aedes albopictus C6/36 mosquito cells, HIV-1NDK was detected in its proviral form. CONCLUSIONS: Our investigations showed that mechanical transmission of HIV-1 by O. moubata is unlikely to occur in the laboratory. This may not be the situation under field conditions.

Aedes↗

PubMed1988

Genetic diversity of African swine fever virus isolates from soft ticks (Ornithodoros moubata) inhabiting warthog burrows in Zambia.

The genomes of African swine fever virus isolates collected from soft ticks (Ornithodoros moubata) inhabiting warthog burrows in four areas of Zambia were compared by restriction enzyme site mapping. Isolates from different areas showed considerable diversity. The regions of genomes that differed between isolates were distributed throughout the virus genome, although some more conserved regions were identified, such as the right-hand third of the genome. The genomes of seven isolates from neighbouring warthog burrows within Livingstone Game Park in southern Zambia were more similar to each other than those from different areas. However, a number of differences were observed even between the genomes of isolates from the same warthog burrow. The variation between these latter isolates probably resulted from point mutations located at various positions along the genome, in addition to small additions or deletions at both terminal regions. Restriction enzyme site mapping indicated that one isolate may have originated by earlier recombination between two distinguishable viruses.

African Swine Fever Virus↗

PubMed1987

An experimental assessment of the tampan tick Ornithodoros moubata as vector of hepatitis B virus.

Wild-caught and colonized tampan ticks, Ornithodoros moubata (Murray), were fed on hepatitis B virus (HBV)-positive blood-means in a series of four experiments. Hepatitis B surface antigen (HBsAg) persisted in nymphal and adult ticks for up to 779 days, while the epsmark antigen (HBeAg) persisted in mature nymphs up to 13 days, in adult males up to 11 days and in adult females up to 16 days. HBsAg was transmitted trans-stadially through two moults during the life cycle but transovarial transmission did not occur. The surface antigen was transmitted by two out of fifteen single ticks into 0.4 ml aliquots of HBV-negative blood, although six groups of ticks failed to transmit into 5.5 ml aliquots of blood: this antigen was not transmitted to hamsters. HBsAg was detected in samples of the ticks' coxal and rectal fluid secretions always at the infecting feed and usually at the second feed. HBeAg was only detected in one of two samples of coxal fluid collected at the infecting feed. The results as a whole indicate that no biological multiplication of virus occurs in O.moubata but that mechanical transmission from ticks to man could occur by: (i) contamination of a person when crushing infected ticks; (ii) infection by bite; (iii) contamination with coxal fluid, especially by scratching bites. This is thought to take place among the Kavango tribe in their village huts in north-eastern Namibia where infestations of infected O.moubata occur.

Animals↗

PubMed1987

Host immunoglobulin G titre and antibody activity in haemolymph of the tick, Ornithodoros moubata.

Immunoglobulin G (IgG) in tick haemolymph was analysed immunochemically and biochemically for its antigenicity, antibody activity and relative concentration in a soft tick, Ornithodoros moubata (Murray) sensu Walton 1962 (Acari: Argasidae). Ouchterlony immunodiffusion tests showed that haemolymph from a tick engorged on rabbit IgG (or human IgG) through an artificial membrane, reacted with anti-rabbit IgG (anti-human IgG) but not with anti-human IgG (anti-rabbit IgG). This indicates that haemolymph of the fed tick contains IgG with a similar antigen specificity to host blood IgG. IgG from tick haemolymph was demonstrated by enzyme immunoassay to have the same antibody activity as ingested IgG. The IgG concentration in tick haemolymph was measured by a quantitative single immunodiffusion test. Changes of IgG titre after a bloodmeal were correlated with IgG activity, which was low for 5 days after a bloodmeal and then suddenly increased. The IgG titre reached a maximum 7 days post-engorgement, and remained high for over 4 months during and after oviposition. 125I-labelled IgG was injected into the tick haemocoel to determine the persistence of IgG in the haemolymph. Recovery of labelled IgG was low at 1 and 3 days, and high at 5, 8 and 16 days after engorgement. The data suggest that IgG in haemolymph disappears quickly soon after engorgement possibly by degradation and/or absorption (adhesion to tissues).

Animals↗

PubMed1992

Analysis of the specificity of the salivary antigens of Ornithodoros erraticus for the purpose of serological detection of swine farms harbouring the parasite.

In Spain, considerable efforts are currently being devoted to the eradication of Ornithodoros erraticus from the swine farms harbouring this parasite, the European vector of African swine fever (ASF). However, to do so, a preliminary requirement is to determine on which farms it is present. Of all possible methods for discovering this, the only one feasible for large scale application is the serological detection of swine bearing anti-O. erraticus antibodies. To apply serology it was necessary to check the specificity of extracts from the salivary glands (SGE) from O. erraticus. For this, indirect ELISA, competitive ELISA and Western blot were used to assay the SGE from O. erraticus and their corresponding antisera against the SGE and respective antisera from 4 ixodidae, one mange mite, one louse and a mosquito. The results obtained show that only the anti-ixodidae sera are able to react against the SGE from O. erraticus. The cause of this reaction are the somatic antigens present in the SGE of the argasid but not its soluble (secretory) antigens. It is proposed that the anti-cement antibodies present in the anti-ixodidae sera are those that react with the somatic antigens of O. erraticus.

African Swine Fever Virus↗

PubMed1977

Nosema parkeri sp. n., a microsporidan from the argasid tick, Ornithodoros parkeri Cooley.

Nosema parkeri sp. n. is described from nymphs and adults of the argasid tick, Ornithodoros parkeri Cooley, from a laboratory colony. Schizogonic and sporogonic stages are described from various tick tissues. Spores are binucleate, measuring 3.2 (3-4) x 1.9 (1.8-2.5) micronm. Transmission is transovarial and transstadial. The parasite does not appear to affect adversely the development or reproduction of the tick. Dermacentor andersoni Stiles was experimentally infected. Attempts to infect Swiss mice by tick feeding or by injection of infected tick suspensions were unsuccessful. The microsporidan differs in structure from Encephalitozoon ixodis Weiser) and Nosema slovaca Weiser & Rehácek, the only other microsporidans known from ticks.

Animals↗

PubMed1967

Spermatophore formation and sperm transfer in Ornithodoros ticks.

In seven species of Ornithodoros and two species of Argas ticks the spermatophore is formed outside the male body in three consecutive stages: (i) the outer bulb, the ectospermatophore, is formed; (ii) it is filled with sperm; and (iii) the inner capsules, the endo-spermatophore, are extruded into the ecto-spermatophore. The morphologies of the ecto-spermatophore and the endo-spermatophore are related to their biological functions. Eversion and evagination of the endo-spermatophore after deposition of the spermatophore on the female genital opening, as well as transfer of sperm from ecto-spermatophore to endo-spermatophore, are described.

Animals↗

PubMed1985

Isolation of a spirochete from the soft tick, Ornithodoros coriaceus: a possible agent of epizootic bovine abortion.

A Borrelia-like spirochete was detected in all three parasitic stages of Ornithodoros coriaceus, the soft tick implicated in the epizoology of epizootic bovine abortion. After the spirochete had been isolated, its distinctness from other North American tick-borne borreliae as well as from Spirochaeta aurantia, Treponema pallidum, and Leptospira interrogans serovar pomona was established on the basis of its morphology, protein components, and inability to infect mice. The spirochete is passed trans-stadially and via eggs by ticks, and it is also excreted in coxal fluid after ticks have fed and detached. Circumstantial evidence suggests that the spirochete may be causally related to epizootic bovine abortion.

Abortion, Veterinary↗

PubMed1982

Isolation of infectious bovine rhinotracheitis virus from the soft-shelled tick, Ornithodoros coriaceus.

Infectious bovine rhinotracheitis virus was isolated from the soft-shelled tick (Ornithodoros coriaceus). Serological identification of the isolated viruses was confirmed by restriction endonuclease digestion of purified virus DNA. These isolations indicate that the soft-shelled tick may be a vector for infectious bovine rhinotracheitis virus. This may be the first reported isolation of mammalian herpesvirus from an arthropod vector.

Animals↗

PubMed2000

Genetic characteristics of Borrelia coriaceae isolates from the soft tick Ornithodoros coriaceus (Acari: Argasidae).

Two Borrelia isolates (CA434 and CA435) cultured from the soft tick Ornithodoros coriaceus were analyzed by contour-clamped homogeneous electric field gel electrophoresis of unrestricted and ApaI-restricted DNA, standard electrophoresis of BamHI- and HindIII-restricted DNA, Southern hybridization, restriction fragment length polymorphism and sequencing of the 16S rRNA gene, and amplification of the 5S-23S intergenic spacer region. These isolates were compared with Borrelia coriaceae type strain Co53, B. burgdorferi sensu stricto strain CA4, and the relapsing-fever spirochete B. parkeri (undesignated). The 16S rRNA region of CA434 and CA435 differed from that of B. coriaceae type strain Co53 by the presence of 1 base (C) at position 367 (GenBank accession no. U42286). The linear plasmid profile of CA434 was similar to that of Co53, and the ApaI, BamHI, and HindIII restriction fingerprints of the total cellular DNA of CA434 and Co53 were similar. In contrast, CA435 differed somewhat from CA434 and Co53, which demonstrates that B. coriaceae is genetically diverse. Southern hybridization showed that the DNAs of CA434 and CA435 hybridized strongly with the digoxigenin-labeled DNA of Co53. Low homology was found between the DNA of Co53 and that of B. parkeri. The 16S rRNA sequence of B. parkeri was identical to previously published results for B. parkeri strain M3001 (GenBank accession number U42296). CA434 and CA435 represent only the second and third isolates of B. coriaceae obtained from any source since its initial isolation from an O. coriaceus tick in 1985. All three B. coriaceae isolates were derived from adult ticks collected from the same locality in northwestern California. Difficulties encountered in detecting B. coriaceae in, and isolating this spirochete from, the tissues of O. coriaceus are discussed. The lack of concordance between different detection or isolation methods suggests that reliance upon a single technique may grossly underestimate the true prevalence of spirochetal infection in wild-caught O. coriaceus ticks.

Animals↗

PubMed1998

African swine fever virus infection in the argasid host, Ornithodoros porcinus porcinus.

The pathogenesis of African swine fever virus (ASFV) infection in Ornithodoros porcinus porcinus was examined in nymphal ticks infected with the ASFV isolate Chiredzi/83/1. At times postinfection (p.i.) ranging from 6 h to 290 days, ticks or dissected tick tissues were titrated for virus and examined ultrastructurally for evidence of virus replication. The ASFV infection rate in ticks was 100% in these experiments, and virus infection was not associated with a significant increase in tick mortality. Initial ASFV replication occurred in phagocytic digestive cells of the midgut epithelium. Subsequent infection and replication of ASFV in undifferentiated midgut cells was observed at 15 days p.i. Generalization of virus infection from midgut to other tick tissues required 2 to 3 weeks and most likely involved virus movement across the basal lamina of the midgut into the hemocoel. Secondary sites of virus replication included hemocytes (type I and II), connective tissue, coxal gland, salivary gland, and reproductive tissue. Virus replication was not observed in the nervous tissue of the synganglion, Malpighian tubules, and muscle. Persistent infection, characterized by active virus replication, was observed for all involved tick tissues. After 91 days p.i., viral titers in salivary gland and reproductive tissue were consistently the highest detected. Successful tick-to-pig transmission of ASFV at 48 days p.i. correlated with high viral titers in salivary and coxal gland tissue and their secretions. A similar pattern of virus infection and persistence in O. porcinus porcinus was observed for three additional ASFV tick isolates in their associated ticks.

African Swine Fever Virus↗

PubMed1999

African swine fever virus replication in the midgut epithelium is required for infection of Ornithodoros ticks.

Although the Malawi Lil20/1 (MAL) strain of African swine fever virus (ASFV) was isolated from Ornithodoros sp. ticks, our attempts to experimentally infect ticks by feeding them this strain failed. Ten different collections of Ornithodorus porcinus porcinus ticks and one collection of O. porcinus domesticus ticks were orally exposed to a high titer of MAL. At 3 weeks postinoculation (p.i.), <25% of the ticks contained detectable virus, with viral titers of <4 log(10) 50% hemadsorbing doses/ml. Viral titers declined to undetectability in >90% of the ticks by 5 weeks p.i. To further study the growth defect, O. porcinus porcinus ticks were orally exposed to MAL and assayed at regular intervals p.i. Whole-tick viral titers dramatically declined (>1,000-fold) between 2 and 6 days p.i., and by 18 days p.i., viral titers were below the detection limit. In contrast, viral titers of ticks orally exposed to a tick-competent ASFV isolate, Pretoriuskop/96/4/1 (Pr4), increased 10-fold by 10 days p.i. and 50-fold by 14 days p.i. Early viral gene expression, but not extensive late gene expression or viral DNA synthesis, was detected in the midguts of ticks orally exposed to MAL. Ultrastructural analysis demonstrated that progeny virus was rarely present in ticks orally exposed to MAL and, when present, was associated with extensive cytopathology of phagocytic midgut epithelial cells. To determine if viral replication was restricted only in the midgut epithelium, parenteral inoculations into the hemocoel were performed. With inoculation by this route, a persistent infection was established although a delay in generalization of MAL was detected and viral titers in most tissues were typically 10- to 1,000-fold lower than those of ticks injected with Pr4. MAL was detected in both the salivary secretion and coxal fluid following feeding but less frequently and at a lower titer compared to Pr4. Transovarial transmission of MAL was not detected after two gonotrophic cycles. Ultrastructural analysis demonstrated that, when injected, MAL replicated in a number of cell types but failed to replicate in midgut epithelial cells. In contrast, ticks injected with Pr4 had replicating virus in midgut epithelial cells. Together, these results indicate that MAL replication is restricted in midgut epithelial cells. This finding demonstrates the importance of viral replication in the midgut for successful ASFV infection of the arthropod host.

African Swine Fever↗