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A. S. Young - One of the best experts on this subject based on the ideXlab platform.

  • Survival of Theileria parva in its nymphal tick vector, Rhipicephalus appendiculatus , under laboratory and quasi natural conditions
    Parasitology, 2003
    Co-Authors: H Ochanda, A. S. Young, G F Medley
    Abstract:

    Groups of nymphal Rhipicephalus appendiculatus Muguga, having a mean of 1 or 9 Theileria parva Muguga-infected salivary gland acini per tick, were kept under quasi-natural conditions at an altitude of 1950 m or 20°C at a relative humidity of 85% in the laboratory and their survival and infection prevalence and abundance determined over time. Theileria parva infections for both categories of ticks survived in the nymphal ticks for 50 or 26 weeks post salivary gland infection under quasi-natural or laboratory conditions respectively. There was a distinct decline in infections in the more heavily infected nymphae under both conditions of exposure, reflecting an apparent density dependence in parasite survival. Nymphal ticks having an average infection level of 1 infected salivary gland acinus per tick, survived for up to 69 or 65 weeks post-repletion under quasi-natural or the laboratory conditions respectively. Nymphae having an average infection level of 9 infected salivary gland acini per tick survived for a similar duration under each of the 2 conditions. The infection level of 9 infected salivary gland acini per tick did not seem to significantly affect the survival of the tick vector compared to those having an average of 1 infected salivary gland acinus per tick.

  • factors influencing infections in Rhipicephalus appendiculatus ticks fed on cattle infected with theileria parva
    Parasitology, 1996
    Co-Authors: A. S. Young, R. A. I. Norval, F. N. Mwakima, T T Dolan, S P Morzaria, J Scott, Andrea Sherriff, George Gettinby
    Abstract:

    A large database on the transmission of a stabilate of the Theileria parva Muguga stock from one breed of cattle using two stocks of Rhipicephalus appendiculatus, Muguga and Ol Pejeta was developed and analysed. Factors associated with the ticks and cattle, and the infections developing in cattle were studied in relation to the infection variables in the tick batches harvested daily from cattle. Generalized Linear Interactive Modelling (GLIM) was used to determine the importance of factors and interactions in influencing the levels of tick infection variables using Type I and Type III sums of squares analyses. Analysis of the 6 variables, prevalence (percentage of ticks infected), abundance (mean number of infected salivary gland acini per tick examined) and intensity (mean number of infected salivary gland acini per infected tick) in batches of 30 male and 30 female ticks showed that 24 covariates, factors or interactions had a significant effect (P> 0·05). Certain covariates and factors were particularly important for all 6 tick infection variables; parasitaemia of animal on the day of tick harvest, stabilate dilution administered to animal, month in which tick batch was harvested, minimum packed cell volume of animal over the sampling period, age of animal, and the minimum leukocyte count of the animal over the sampling period. The GLIM analyses were found to be a useful tool in identifying factors that influence infection levels and in devising methods of producing tick batches with more predictable infections.

  • comparison of the transmission of theileria parva between different instars of Rhipicephalus appendiculatus
    Parasitology, 1996
    Co-Authors: Horace Ochanda, A. S. Young, C Wells, Graham F Medley, Brian D Perry
    Abstract:

    The transmission of Theileria parva by nymphal and adult Rhipicephalus appendiculatus was compared by the assessment of salivary gland infections in tick batches fed on the same group of infected cattle at the same time. When larval and nymphal R. appendiculatus Muguga ticks were fed concurrently on cattle undergoing acute infection with T. parva Muguga, the resultant nymphae developed a slightly lower prevalence of infection than did the adult ticks. The abundance of infection was 5-20 times higher in the adult ticks than in the nymphae. When larval and nymphal R. appendiculatus Muguga and R. appendiculatus M c Ilwaine were fed to repletion on cattle infected with T. parva Boleni, a parasite causing subacute infection, resultant adult tick batches had a relatively high prevalence of infection, but infection was not detected in resultant nymphal batches. When cattle that were carriers of 2 stocks of T. parva, Marikebuni and Kiambu 5, were used as the source of infection, the infections developing in adult R. appendiculatus Muguga ticks were much higher than those developing in nymphae. The structure of salivary glands differed between nymphal ticks, adult males and adult females, and this is considered to be an important factor affecting the infection levels. The morphology of the type III acini, the target acini for sporogony, was similar, but the mean numbers of type III acini were different, with 87 in nymphae, 1346 in males and 1736 in females. This difference was correlated with the different infection levels produced in the various instars and sexes. While the process of sporogony in the different tick instars and sexes was similar, the rate of sporogony was fastest in feeding nymphae, taking on average 2-3 days, compared to 3-4 days in females and an irregular period in the males. These results are discussed in relation to the epidemiology of T. parva.

  • optimization of the in vitro feeding of Rhipicephalus appendiculatus nymphae for the transmission of theileria parva
    Parasitology, 1995
    Co-Authors: S. M. Waladde, A. S. Young, S. N. Mwaura, G N Njihia, F. N. Mwakima
    Abstract:

    An apparatus for artificial feeding of Rhipicephalus appendiculatus nymphae was modified to improve feeding performance. Heparinized blood was supplied above a treated artificial membrane while the ticks attached below on its undersurface. The feeding apparatus was incubated at 37 degrees C in an atmosphere of 3% CO2 concentration and a relative humidity of 75-80%. Under these conditions, 91% of the engorged nymphae attained a mean weight of 6-11 mg, and an average of 93% of those nymphae moulted into adults. When this system was used to feed nymphal ticks on blood infected with Theileria parva piroplasms, the mean prevalence of infection in the resultant female and male ticks was 86% and 54%, respectively. The feeding performance and T. parva infection levels were comparable to those of nymphal ticks fed on the blood donor cattle. The apparatus used in this study has potential for modification to suit the artificial feeding needs of other species of ixodid ticks and for use in investigations to examine other tick/pathogen relationships.

  • differential development and emission of theileria parva sporozoites from the salivary gland of Rhipicephalus appendiculatus
    Parasitology, 1995
    Co-Authors: M K Shaw, A. S. Young
    Abstract:

    The initiation of feeding of infected Rhipicephalus appendiculatus adults induces the rapid development of Theileria parva sporoblasts within the salivary gland acini leading to the production of numerous sporozoites which are inoculated into the mammalian host initiating infection. In this study the pattern of development, host cell specificity and emission of T. parva sporozoites within the salivary glands of heavily infected, 4-day fed adult R. appendiculatus ticks was examined. Infected acini were randomly distributed throughout the salivary gland. Sporozoite development within each gland was not synchronized and wide variation in the rate of parasite development, which correlated with the secretory activity of the individual acinus, was observed in all glands examined. Previous studies had shown that T. parva developed primarily in Type III 'e' cells. However, in heavily infected salivary glands sporogony and the emission of mature sporozoites also occurred in 'c' cells of Type II acini. Sporozoite emission from infected cells occurred by a process similar to apocrine secretion. The loss of the apical membrane of the infected cell allowed sporozoites free access to the lumen of the acinus and into the collecting ducts of the salivary gland. Sporozoite discharge was gradual since few parasites were found in the acinus valve or in the collecting ducts. Furthermore, the small size of the acinar valve aperature ensures that only small numbers of sporozoites can be released at any one time from an infected acinus.

Patricia A. Nuttall - One of the best experts on this subject based on the ideXlab platform.

  • functional role of 64p the candidate transmission blocking vaccine antigen from the tick Rhipicephalus appendiculatus
    International Journal for Parasitology, 2009
    Co-Authors: Sabina Havlikova, Ladislav Roller, Juraj Koci, Adama R Trimnell, Maria Kazimirova, Boris Klempa, Patricia A. Nuttall
    Abstract:

    Anti-ectoparasite vaccines offer attractive alternatives to the use of chemical pesticides, especially if they also control the pathogens that ectoparasites transmit. However, selection of suitable antigens is a major constraint on vaccine development. The recombinant tick cement protein, 64TRP, derived from the African brown ear tick, Rhipicephalus appendiculatus, acts as a transmission-blocking vaccine in a mouse model of tick-borne encephalitis virus (TBEV) transmission, protecting immunised mice against lethal challenge with TBEV after exposure to infected ticks. 64TRP acts as a dual action vaccine, targeting both 'exposed' antigens in tick saliva and 'concealed' antigenic epitopes in the tick midgut. To assess further the suitability of 64TRP as a vaccine antigen, we examined the function (including localisation) of the protein, and its sequence variability. Histological profiles of normal hamster skin showed similarities between normal skin proteins in the epidermis (keratin) and dermis (collagen/reticulin) and the tick cement cone. Immuno-reactivity of anti-64TRP sera with hamster skin suggests a potential sequence similarity of 64P with host skin proteins and may reflect previously reported sequence similarities of 64P with skin keratin and collagen proteins. Variability in the N-terminal signal peptide and in the C-terminal glycine-rich amino acid repeats of 64P protein was detected; previous studies showed the C-terminal region to be immunologically non-protective. Using in situ hybridisation and quantitative reverse transcriptase-PCR, 64P mRNA was detected in the types II and III salivary gland acini. The highest levels of 64P mRNA were observed in 1-day fed females, and 1- and 7-day fed males. Salivary glands of longer feeding females and unfed ticks as well as midguts of both sexes were negative. Early expression in tick salivary glands is consistent with previously published data that 64P is a cement protein, and contributes to its candidacy as a vaccine antigen. However, further studies are required to assess whether cross-reactivity with skin proteins may induce autoimmunity.

  • Rhipicephalus appendiculatus acari ixodidae dynamics of thogoto virus infection in female ticks during feeding on guinea pigs
    Experimental Parasitology, 2003
    Co-Authors: Reuben W Kaufman, Patricia A. Nuttall
    Abstract:

    Engorged nymphs (Rhipicephalus appendiculatus) were inoculated parenterally with Thogoto (THO) virus (approximately 1 microl per nymph; 10(6)-10(7) PFU/ml). The adult females which resulted were used as the source of infected ticks for this study. Hemolymph, salivary glands, synganglion, gut, ovary, and Malpighian tubules were collected on each day of the blood meal and titrated for THO virus by plaque assay. The percent of tissues infected with virus was 16% or less on the day of attachment. Percent infection rose for all tissues throughout 6-7 days of feeding, reaching 40-100% infection during the rapid phase of engorgement. For the first 4 days of feeding, virus titer in the synganglion was higher than in salivary glands (means of 6.4-34.7 PFU/synganglion and 1.6-8.8 PFU/salivary gland pair). From days 5-7, virus titer was generally higher in the salivary gland than the synganglion (means of 422, 408, and 817 PFU/gland pair and means of 62, 811, and 9 PFU/synganglion). However, because a salivary gland pair is much heavier than a synganglion, the virus concentration in the synganglion was much higher than in the salivary gland during the slow phase of feeding. During the rapid phase of feeding, the difference in virus titer between the synganglion and salivary gland reduced. This difference between the early and late stages of feeding may explain why a previous study [J. Gen. Virol. 70 (1989) 1093], using immunofluorescence and immuno-gold labelling, failed to detect virus in the salivary gland early in feeding. These data provide evidence to explain that R. appendiculatus can transmit THO virus within 24h of attachment, an important epidemiological finding.

  • molecular individuality and adaptation of the tick Rhipicephalus appendiculatus in changed feeding environments
    Medical and Veterinary Entomology, 2001
    Co-Authors: Hui Wang, W W Cui, W R Kaufman, Patricia A. Nuttall
    Abstract:

    The tick Rhipicephalus appendiculatus Neumann (Acari: Ixodidae) naturally infests many host species. However, the mechanisms that enable it to feed on such a wide range of hosts are unclear. One possibility is that a tick population maintains molecular (genotypic and/or phenotypic) diversity among individuals such that individuals vary in their competency in taking bloodmeals under different feeding conditions. As a first step in testing this hypothesis, we showed that the polymorphism of salivary gland proteins, previously demonstrated in unfed ticks, was maintained during feeding on guinea-pigs. We then compared feeding performance under standard laboratory rearing conditions: one instar (adults or nymphs) feeding on guinea-pigs, with three changed conditions: (1) two instars (adults and nymphs) feeding together on guinea-pigs; (2) one instar (adults or nymphs) feeding on hamsters; and (3) two instars (adults and nymphs) feeding together on hamsters. The mean engorged weight of adult females was significantly reduced under all changed conditions, indicating that most of the adult individuals were significantly challenged by the changed conditions. However, some individuals achieved successful engorgement, indicating competence to the changed condition, and demonstrating variation in adaptive ability among individuals. Engorged females produced egg masses positively correlated to the engorged weights. More interestingly, the correlation coefficient (R) increased when feeding condition was changed. This may lead to more efficient selection for population adaptation under the changed conditions. As the feeding success of ixodid ticks depends on the efficiency of the cocktail of immunomodulatory saliva, the relevance of the polymorphism of salivary gland proteins and host adaptation is discussed.

  • Salivary fluid secretion in the ixodid tick Rhipicephalus appendiculatus is inhibited by Thogoto virus infection
    Experimental & Applied Acarology, 2001
    Co-Authors: W. Reuben Kaufman, Alan S. Bowman, Patricia A. Nuttall
    Abstract:

    Adult Rhipicephalus appendiculatus ticks, infectedwith Thogoto (THO) virus or control, were fed on guinea pigs and removed atintervals throughout the feeding cycle. Salivary fluid secretion was measuredbyan in vitro technique. The salivary glandsof infected, partially-fed ticks secreted fluid in vitro at about 75% the rateof controls, but the difference between infected and controls among engorgedticks was not statistically significant. Basal and DA-stimulated levels ofcyclic AMP (cAMP) were determined in isolated glands and were significantlyaffected by THO virus infection. The differences in secretory rate amongcontroland infected ticks could not be explained in terms of altered cAMP levels.Haemolymph volume was measured by a tracer-dilution technique using^3H-inulin. The mean haemolymph volume for both THO-infected andcontrol groups was between 23–24% body weight throughout the feedingcycle, indicating that infection by this arbovirus did not influence salivaryfluid secretion via altered haemolymph volume. The mechanism by which THO virusaffects secretory activity of its tick vector remains unknown.

  • Immunoglobulin G binding proteins in male Rhipicephalus appendiculatus ticks.
    Parasite Immunology, 1995
    Co-Authors: Hui Wang, Patricia A. Nuttall
    Abstract:

    Three abundant immunoglobulin G binding proteins (IGBPs) of29kDa (IGBP-MA), 25kDa (IGBP-MB), and 21 kDa (IGBP-MC) were isolated from partly fed male Rhipicephalus appendiculatus ticks using an agar-ose-IgG column. After separating the proteins by SDS-PA GE, each individual IGBP band was cutou tfrom the gel and used to raise antiserum in guinea pigs. Using immuno-blotting, each of the three IGBPs was shown to be antigenically distinct, and specific for feeding male R. appendiculatus ticks. They were detected in the salivary glands of male ticks that had been feeding in either the presence of absence of female ticks, and appeared to be glycoproteins. The smallest protein, IGBP-MC, bound to guinea pig IgG (on which species the ticks were fed) and also bound to human and bovine IgG, whereas IGBP-MA and possibly IGBP-MB only bound to guinea pig IgG. The function of IGBPs in tick salivary glands and their significance in male ticks are discussed.

Misao Onuma - One of the best experts on this subject based on the ideXlab platform.

  • pcr based detection of blood parasites in cattle and adult Rhipicephalus appendiculatus ticks
    Veterinary Journal, 2009
    Co-Authors: Shinji Yamada, Satoru Konnai, Saiki Imamura, Misao Onuma, Martin Simuunza, Amos Chota, Andrew Nambota, Mwelwa Chembensofu, Kazuhiko Ohashi
    Abstract:

    Abstract To ascertain the infection rate for tick-borne pathogens in Zambia, an epidemiological survey of Theileria parva, Babesia bigemina and Anaplasma marginale in traditionally managed Sanga cattle was conducted using PCR. Of the 71 native Zambian cattle, 28 (39.4%) were positive for T. parva, 16 (22.5%) for B. bigemina and 34 (47.9%) for A. marginale. The mixed infection rate in cattle was 8.5% (6/71), 16.9% (12/71), 7.0% (5/71) and 2.8% (2/71) for T. parva/B. bigemina, T. parva/A. marginale, B. bigemina/A. marginale and T. parva/B. bigemina/A. marginale, respectively. To predict the risk for transmission of tick-borne pathogens from ticks to cattle, a total of 74 Rhipicephalus appendiculatus ticks were collected from a location where cattle had been found positive for T. parva. Of the ticks collected, 10 (13.5%) were found to be PCR-positive for T. parva. The results suggest that the infection rate for tick-borne pathogens was relatively high in Sanga cattle and that adult R. appendiculatus ticks were highly infected with T. parva.

  • cloning and characterization of Rhipicephalus appendiculatus voraxinα and its effect as anti tick vaccine
    Vaccine, 2009
    Co-Authors: Shinji Yamada, Satoru Konnai, Saiki Imamura, Takuya Ito, Misao Onuma, Kazuhiko Ohashi
    Abstract:

    Abstract Male tick-derived voraxinα and voraxinβ, a pair of testicular proteins, are transferred to female via copulation to stimulate female blood feeding in the tick Amblyomma hebraeum ( A. hebraeum ). Immunized animals with recombinant (r-)voraxinα and voraxinβ have been shown as highly resistant to the tick infestation. In this study, we describe the cloning and characterization of voraxinα homologue from the tick Rhipicephalus appendiculatus ( R. appendiculatus ), the major vector for East Coast fever in Eastern Africa. The sequence analysis of the R. appendiculatus voraxinα indicated that the deduced amino acid sequence had high similarity with voraxinα of the tick A. hebraeum and Dermacentor variabilis , suggesting that voraxinα is conserved in different tick genera. Quantitative RT-PCR and Western blotting analysis showed that male voraxinα was predominantly expressed in testis and its expression was induced by blood feeding. R. appendiculatus voraxinα was not secreted into the host during tick feeding and was detected in mated female hemolymph as measured by Western blotting. Preliminary vaccination of rabbits with r-voraxinα elicited the humoral immunity and conferred protective immunity against female ticks, resulting in the reduced fed weight. These results suggest that r-voraxinα could be a good candidate as anti-tick vaccine.

  • Rhipicephalus appendiculatus characterization of a testis associated protein
    Experimental Parasitology, 2008
    Co-Authors: Shinji Yamada, Satoru Konnai, Yuko Ito, Saiki Imamura, Takuya Ito, Misao Onuma, Kazuhiko Ohashi
    Abstract:

    A novel gene coding for Rhipicephalus appendiculatus Male-specific Protein (RAMP) was identified in a cDNA library constructed from the testis/vas deferens of R. appendiculatus ticks. This gene encodes a secreted protein exclusively expressed in the testis/vas deferens. The putative RAMP amino acid sequence contains a signal peptide and has 29% amino acid identity with male-specific Is5 gene of Ixodes scapularis. Gene expression studies revealed that RAMP mRNA was up-regulated in male ticks during blood feeding. RAMP was detected not only in the testis/vas deferens of males but also in postcoitum female ticks based on Western blotting, indicating that this protein is transferred to the female tick during copulation. Virgin female ticks, microinjected with recombinant RAMP, had significantly prolonged attachment duration during feeding, but there was no effect on fed weight. These results suggest that RAMP is a male-specific molecule in the spermatophore, and is related to female attachment behavior in R. appendiculatus ticks.

  • effects of anti tick cocktail vaccine against Rhipicephalus appendiculatus
    Japanese Journal of Veterinary Research, 2008
    Co-Authors: Saiki Imamura, Satoru Konnai, Shinji Yamada, Yuko Ito, Itabajara Da Silva Vaz, Chie Nakajima, Martin Simuunza, Tomoko Tajima, Jun Yasuda, Misao Onuma
    Abstract:

    Rhipicephalus appendiculatus serpin-3 (RAS-3), R. appendiculatus serpin-4 (RAS-4) and a 36-kDa immuno-dominant protein of R. appendiculatus (RIM36) were reported as candidate antigens for the anti-tick vaccine to control ixodid ticks. In the present study, we generated recombinant proteins of RAS-3 (rRAS-3), RAS-4 (rRAS-4) and RIM36 (rRIM36), and assessed their potency as an anti-tick cocktail vaccine in cattle model. RT-PCR analysis showed that RAS-3, RAS-4 and RIM36 transcripts were detected in both adult male and female ticks during feeding. Immunization of cattle with the combination of rRAS-3, rRAS-4 and rRIM36 had raised antibodies against all recombinants and anti-sera had reacted with the molecules from the tick salivary gland extract. Tick infestation challenge demonstrated protective immunity against female ticks, resulting in mortality rates of 39.5 and 12.8 % for the vaccinated and control groups, respectively. Moreover, the mortality rate of Theileria parva -infected female ticks was 48.5 and 10.8 % in the vaccinated and control group, respectively. In order to evaluate the levels of pathogen transmission capacity by T. parva-infected ticks fed on immunized cattle, the occurrence of T. parva in the bovine parotid lymph node and peripheral blood was also determined and quantified by real-time PCR. Although the infection with T. parva could not be protected by the vaccine, the occurrence of pathogen in peripheral blood was delayed 1 to 2 days after the infestation challenge in vaccinated group. These results suggest that this cocktail vaccine plays a role in the prevention of tick infestation.

  • attachment duration required for Rhipicephalus appendiculatus to transmit theileria parva to the host
    Vector-borne and Zoonotic Diseases, 2007
    Co-Authors: Satoru Konnai, Shinji Yamada, Saiki Imamura, Kazuhiko Ohashi, Martin Simuunza, Mwelwa Chembensof, Amos Chota, Andrew Nambota, Misao Onuma
    Abstract:

    ABSTRACT Theileria parva, the agent of East Coast fever (ECF), is transmitted to the host during the blood meal feeding of Rhipicephalus appendiculatus ticks. In order to investigate the relationship between the attachment duration of R. appendiculatus and the transmission of T. parva, infected adult ticks were allowed to attach to naive mice for variable lengths of time. Attached ticks and host animal's back skin biopsies from the tick attachment site were collected daily, starting from 24 hours post-tick attachment, and used for seminested polymerase chain reaction (PCR) detection of T. parva. T. parva-infected ticks started to transmit the parasites from 72 hours post-tick attachment. As expected, the transmission of T. parva from ticks to mouse skin increased with duration of tick attachment. Transmission of the parasites was 77.7%, 100%, 85.5%, and 100% on day 4, 5, 6, and 7 post-tick attachment, respectively, as could be detected from mice skin biopsies taken from T. parva-infected ticks' attachment...

F. N. Mwakima - One of the best experts on this subject based on the ideXlab platform.

  • factors influencing infections in Rhipicephalus appendiculatus ticks fed on cattle infected with theileria parva
    Parasitology, 1996
    Co-Authors: A. S. Young, R. A. I. Norval, F. N. Mwakima, T T Dolan, S P Morzaria, J Scott, Andrea Sherriff, George Gettinby
    Abstract:

    A large database on the transmission of a stabilate of the Theileria parva Muguga stock from one breed of cattle using two stocks of Rhipicephalus appendiculatus, Muguga and Ol Pejeta was developed and analysed. Factors associated with the ticks and cattle, and the infections developing in cattle were studied in relation to the infection variables in the tick batches harvested daily from cattle. Generalized Linear Interactive Modelling (GLIM) was used to determine the importance of factors and interactions in influencing the levels of tick infection variables using Type I and Type III sums of squares analyses. Analysis of the 6 variables, prevalence (percentage of ticks infected), abundance (mean number of infected salivary gland acini per tick examined) and intensity (mean number of infected salivary gland acini per infected tick) in batches of 30 male and 30 female ticks showed that 24 covariates, factors or interactions had a significant effect (P> 0·05). Certain covariates and factors were particularly important for all 6 tick infection variables; parasitaemia of animal on the day of tick harvest, stabilate dilution administered to animal, month in which tick batch was harvested, minimum packed cell volume of animal over the sampling period, age of animal, and the minimum leukocyte count of the animal over the sampling period. The GLIM analyses were found to be a useful tool in identifying factors that influence infection levels and in devising methods of producing tick batches with more predictable infections.

  • optimization of the in vitro feeding of Rhipicephalus appendiculatus nymphae for the transmission of theileria parva
    Parasitology, 1995
    Co-Authors: S. M. Waladde, A. S. Young, S. N. Mwaura, G N Njihia, F. N. Mwakima
    Abstract:

    An apparatus for artificial feeding of Rhipicephalus appendiculatus nymphae was modified to improve feeding performance. Heparinized blood was supplied above a treated artificial membrane while the ticks attached below on its undersurface. The feeding apparatus was incubated at 37 degrees C in an atmosphere of 3% CO2 concentration and a relative humidity of 75-80%. Under these conditions, 91% of the engorged nymphae attained a mean weight of 6-11 mg, and an average of 93% of those nymphae moulted into adults. When this system was used to feed nymphal ticks on blood infected with Theileria parva piroplasms, the mean prevalence of infection in the resultant female and male ticks was 86% and 54%, respectively. The feeding performance and T. parva infection levels were comparable to those of nymphal ticks fed on the blood donor cattle. The apparatus used in this study has potential for modification to suit the artificial feeding needs of other species of ixodid ticks and for use in investigations to examine other tick/pathogen relationships.

  • estimation of heritability of susceptibility to infection with theileria parva in the tick Rhipicephalus appendiculatus
    Parasitology, 1995
    Co-Authors: A. S. Young, S. N. Mwaura, F. N. Mwakima, T T Dolan, Horace Ochanda, G M Njihia, M W Muthoni, R B Dolan
    Abstract:

    Heritability of susceptibility to infection with Theileria parva was estimated from full sib families of Rhipicephalus appendiculatus ticks. Male and female ticks of 2 stocks were mated singly. Nineteen full sib families of the Muguga stock and 17 full sib families of the Kiambu stock were obtained. Nymphae of these families were fed on cattle infected with T. parva so that the ticks became replete on days 16 and 17 after infection when the blood was parasitaemic with intraerythrocytic piroplasms. The T. parva infections were assessed in the resultant adult ticks of each full sib group and the abundance of infection, the number of salivary gland acini infected/tick, was found to be the most useful parameter for analysis. Estimates of heritability of the susceptibility to infection with T. parva for the Kiambu and the Muguga tick stocks were 0.24 and 0.26 respectively. Using only the data from ticks which fed on day 16, the heritability estimates were 0.39 for the Kiambu stock and 0.59 for the Muguga stock. These results indicate that tick lines of high or low susceptibility for T. parva infection could be produced through selection.

  • Transmission of Theileria parva to cattle by Rhipicephalus appendiculatus adults fed as nymphae in vitro on infected blood through an artificial membrane
    Parasitology, 1993
    Co-Authors: S. M. Waladde, S. A. Ochieng', A. S. Young, S. N. Mwaura, F. N. Mwakima
    Abstract:

    A technique is described for the efficient feeding of Rhipicephalus appendiculatus nymphae on cattle blood through an artificial membrane bearing tactile and olfactory stimuli. The effect of four anticoagulation methods on the feeding of nymphae was compared and heparinized blood was found to be the most efficacious, followed by defibrinated blood. Blood treated with acid citrate dextrose (ACD) or ethylenediamine tetraacetate (EDTA) inhibited nymphal feeding. Nymphae fed on heparinized and defibrinated blood obtained engorgement weights within the range of ticks fed on mammalian hosts and they subsequently moulted and fed normally as adults and produced viable eggs. Nymphae fed on membranes using either defibrinated or heparinized blood infected with Theileria parva piroplasma developed salivary gland infections as adult ticks and transmitted East Coast fever (ECF) to susceptible cattle. There were indications that T. parva-infected defibrinated blood was not as infective to the feeding nymphae as the infected heparinized blood. When T. parva-infected heparinized blood was used to feed nymphae through membranes in two experiments, it was found that the infections in the resultant adult ticks could be comparable to those of nymphae fed on donor cattle, but were usually lower. The membrane feeding technique will enable the study of factors affecting the tick and T. parva transmission without the complication of host/T. parva interactions and could be useful for both tick maintenance and Theileria parasite isolation and maintenance.

Satoru Konnai - One of the best experts on this subject based on the ideXlab platform.

  • Rhipicephalus microplus cystatin as a potential cross protective tick vaccine against Rhipicephalus appendiculatus
    Ticks and Tick-borne Diseases, 2020
    Co-Authors: Luis Fernando Parizi, Carolina Konrdorfer Rangel, Gabriela Alves Sabadin, Bianca Saggin, Irene Kiio, Marina Amaral Xavier, Renata Da Silva Matos, Maria Izabel Camargomathias, Adriana Seixas, Satoru Konnai
    Abstract:

    Rhipicephalus appendiculatus, the brown ear tick, is an important disease vector of livestock in eastern, central and southern Africa. Rhipicephalus appendiculatus acaricide resistance requires the search for alternative methods for its control. Cystatins constitute a superfamily of cysteine peptidase inhibitors vital for tick blood feeding and development. These inhibitors were proposed as antigens in anti-tick vaccines. In this work, we applied structural and biochemical approaches to characterize a new cystatin named R. appendiculatus cystatin 2a (Racys2a). Structural modeling showed that this new protein possesses characteristic type 2 cystatin motifs, besides conservation of other structural patterns along the protein. Peptidase inhibitory assays with recombinant Racys2a showed modulation of tick and host cathepsins involved in blood digestion and immune system responses, respectively. A heterologous tick challenge with R. appendiculatus in rabbits immunized with recombinant Rhipicephalus microplus cystatin 2c (rBmcys2c) was performed to determine cross-reactivity. Histological staining showed that rBmcys2c vaccination caused damage to the gut, salivary gland and ovary tissues in R. appendiculatus. Furthermore, cystatin vaccine reduced the number of fully engorged adult females in 11.5 %. Consequently, strategies to increase the protection rate are necessary, including the selection of two or more antigens to compose a vaccine cocktail.

  • identification and partial characterization of a gut Rhipicephalus appendiculatus cystatin
    Ticks and Tick-borne Diseases, 2013
    Co-Authors: Saiki Imamura, Naftaly Githaka, Luis Fernando Parizi, Satoru Konnai, Shinji Yamada, Itabajara Da Silva Vaz, Shiro Murata, Kazuhiko Ohashi
    Abstract:

    Vaccines are among the alternative tick control methods expected to replace at least in part the volumes of chemical acaricides currently used worldwide. However, a vaccination approach depends on a host immune response against proteins that are essential to tick physiology. The cystatin family is a protein class recently investigated to compose an effective antigen in a tick vaccine. In this study, a cDNA from Rhipicephalus appendiculatus with high sequence similarity to cystatins type 2 was identified by random sequencing analysis and called R. appendiculatus cystatin 1 (Ra-cyst-1). DNA sequence analysis showed that the cloned Ra-cyst-1 has a 423-bp open reading frame and codified to a 140-amino acid polypeptide. The putative mature protein consists of 115 amino acid residues with a deduced molecular weight of 12.8kDa. The highly conserved G (P-I), QxVxG (P-II), and PW (P-III) type 2 cystatins motifs are present in Ra-cyst-1 cDNA. RT-PCR analysis showed that the Ra-cyst-1 gene is expressed in nymph, male, and female midgut following blood feeding, but not in the salivary glands of fed females. In addition, Western blot revealed that recombinant Ra-cyst-1 was not recognized by sera derived from rabbits infested with ticks, suggesting that this cystatin is not secreted into the host during infestation. We hypothesize that Ra-cyst-1 may play a role in the tick feeding process and could be a concealed antigen candidate in further anti-tick vaccination trials.

  • pcr based detection of blood parasites in cattle and adult Rhipicephalus appendiculatus ticks
    Veterinary Journal, 2009
    Co-Authors: Shinji Yamada, Satoru Konnai, Saiki Imamura, Misao Onuma, Martin Simuunza, Amos Chota, Andrew Nambota, Mwelwa Chembensofu, Kazuhiko Ohashi
    Abstract:

    Abstract To ascertain the infection rate for tick-borne pathogens in Zambia, an epidemiological survey of Theileria parva, Babesia bigemina and Anaplasma marginale in traditionally managed Sanga cattle was conducted using PCR. Of the 71 native Zambian cattle, 28 (39.4%) were positive for T. parva, 16 (22.5%) for B. bigemina and 34 (47.9%) for A. marginale. The mixed infection rate in cattle was 8.5% (6/71), 16.9% (12/71), 7.0% (5/71) and 2.8% (2/71) for T. parva/B. bigemina, T. parva/A. marginale, B. bigemina/A. marginale and T. parva/B. bigemina/A. marginale, respectively. To predict the risk for transmission of tick-borne pathogens from ticks to cattle, a total of 74 Rhipicephalus appendiculatus ticks were collected from a location where cattle had been found positive for T. parva. Of the ticks collected, 10 (13.5%) were found to be PCR-positive for T. parva. The results suggest that the infection rate for tick-borne pathogens was relatively high in Sanga cattle and that adult R. appendiculatus ticks were highly infected with T. parva.

  • cloning and characterization of Rhipicephalus appendiculatus voraxinα and its effect as anti tick vaccine
    Vaccine, 2009
    Co-Authors: Shinji Yamada, Satoru Konnai, Saiki Imamura, Takuya Ito, Misao Onuma, Kazuhiko Ohashi
    Abstract:

    Abstract Male tick-derived voraxinα and voraxinβ, a pair of testicular proteins, are transferred to female via copulation to stimulate female blood feeding in the tick Amblyomma hebraeum ( A. hebraeum ). Immunized animals with recombinant (r-)voraxinα and voraxinβ have been shown as highly resistant to the tick infestation. In this study, we describe the cloning and characterization of voraxinα homologue from the tick Rhipicephalus appendiculatus ( R. appendiculatus ), the major vector for East Coast fever in Eastern Africa. The sequence analysis of the R. appendiculatus voraxinα indicated that the deduced amino acid sequence had high similarity with voraxinα of the tick A. hebraeum and Dermacentor variabilis , suggesting that voraxinα is conserved in different tick genera. Quantitative RT-PCR and Western blotting analysis showed that male voraxinα was predominantly expressed in testis and its expression was induced by blood feeding. R. appendiculatus voraxinα was not secreted into the host during tick feeding and was detected in mated female hemolymph as measured by Western blotting. Preliminary vaccination of rabbits with r-voraxinα elicited the humoral immunity and conferred protective immunity against female ticks, resulting in the reduced fed weight. These results suggest that r-voraxinα could be a good candidate as anti-tick vaccine.

  • Rhipicephalus appendiculatus characterization of a testis associated protein
    Experimental Parasitology, 2008
    Co-Authors: Shinji Yamada, Satoru Konnai, Yuko Ito, Saiki Imamura, Takuya Ito, Misao Onuma, Kazuhiko Ohashi
    Abstract:

    A novel gene coding for Rhipicephalus appendiculatus Male-specific Protein (RAMP) was identified in a cDNA library constructed from the testis/vas deferens of R. appendiculatus ticks. This gene encodes a secreted protein exclusively expressed in the testis/vas deferens. The putative RAMP amino acid sequence contains a signal peptide and has 29% amino acid identity with male-specific Is5 gene of Ixodes scapularis. Gene expression studies revealed that RAMP mRNA was up-regulated in male ticks during blood feeding. RAMP was detected not only in the testis/vas deferens of males but also in postcoitum female ticks based on Western blotting, indicating that this protein is transferred to the female tick during copulation. Virgin female ticks, microinjected with recombinant RAMP, had significantly prolonged attachment duration during feeding, but there was no effect on fed weight. These results suggest that RAMP is a male-specific molecule in the spermatophore, and is related to female attachment behavior in R. appendiculatus ticks.