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Ticks are obligate haematophagous ectoparasites of wild and domestic animals as well as humans, considered to be second worldwide to mosquitoes as vectors of human diseases, but the most important vectors of disease-causing pathogens in domestic and wild animals. Babesia spp. are tick-borne pathogens that cause a disease called babesiosis in a wide range of animals and in humans. In particular, Babesia bovis and Babesia bigemina are transmitted by cattle ticks, Rhipicephalus (Boophilus) annulatus and Rhipicephalus microplus, which are considered the most important cattle ectoparasites with major economic impacts on cattle production. The objectives of this study were to identify R. annulatus genes differentially expressed in response to infection with B. bigemina. Functional analyses were conducted on selected genes by RNA interference in both R. annulatus and R. microplus ticks. Eight hundred randomly selected suppression-subtractive hybridisation library clones were sequenced and analysed. Molecular function Gene Ontology assignments showed that the obtained tick sequences encoded for proteins with different cellular functions. Differentially expressed genes with putative functions in tick-pathogen interactions were selected for validation of SSH results by real-time reverse transcription-PCR. Genes encoding for TROSPA, calreticulin, ricinusin and serum amyloid A were over-expressed in B. bigemina-infected ticks while Kunitz-type protease inhibitor 5 mRNA levels were down-regulated in infected ticks. Functional analysis of differentially expressed genes by double stranded RNA-mediated RNAi showed that under the conditions of the present study knockdown of TROSPA and serum amyloid A significantly reduced B. bigemina infection levels in R. annulatus while in R. microplus, knockdown of TROSPA, serum amyloid A and calreticulin also reduced pathogen infection levels when compared with controls. Several studies have characterised the tick-pathogen interface at the molecular level. However, to our knowledge this is the first report of functional genomics studies in R. annulatus infected with B. bigemina. The results reported here increase our understanding of the role of tick genes in Babesia infection/multiplication., (Copyright © 2012 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

In Uzbekistan, 1984 cattle were vaccinated with the TAU-219 autochthonous live Theileria annulata vaccine under field conditions. There were no post-vaccination reactions recorded in calves vaccinated with 10 times the recommended dose, under semi-field conditions. After vaccination 53.9% of the vaccinates developed fever over 39.5 degrees C that lasted for a few days, but none developed clinical theileriosis or required drug treatment during the 3-week follow-up. The numbers of animals in which piroplasms were detected before and after vaccination were similar (7.15% and 7.25%, respectively), indicating previous exposure to T. annulata tick infection. Following vaccination none of the 241 pregnant cows aborted. Milk production during 30-45 days was similar in non-vaccinated and vaccinated cows, at about 5.2-5.9L/day. During 1999-2006 a total of 11,000 field-grazing cattle were safely vaccinated in Uzbekistan.

Susceptible dairy cattle were immunized with attenuated, live calf-derived, in vitro-cultured or biologically cloned Babesia bovis, with non-viable exoantigens, or with recombinant rhoptry-associated protein 1 (rRAP1). Antibody response assessed by the indirect fluorescent assay (IFA) and by the growth inhibition activity in vitro showed that seroconversion correlated with neutralization activity in vitro in all immunized groups, but not with protective immunity in vivo. The protective responses elicited by immunization with completely avirulent biologically cloned live parasites, or by the exoantigens were sufficient for highly susceptible dairy cattle, in which prime immunization with blood-derived attenuated parasites cause clinical babesiosis. Upon challenge with virulent live parasites all immunized calves were solidly protected, but only partial protective immunity was acquired by rRAP1 immunization.

Overwhelming evidence has accumulated of the effectiveness of immunization with live attenuated vaccines to control tick-borne diseases of livestock. Despite several disadvantages, vaccination with live attenuated organisms against tropical theileriosis, babesiosis and possibly heartwater constitutes one of the most cost-effective intervention strategies. Although great advances have been made through genomics and proteomics research, this has not yet translated into effective non-living vaccines. As a result, there is a continuing necessity to use available live vaccines in tick and tick-borne disease-control strategies adapted to conditions prevailing in many parts of the world.

Attenuated vaccines, produced by prolonged in vitro culture of the macroschizont stage of the life-cycle, are the main method of controlling Theileria annulata infections. Little is known about the mechanism(s) of attenuation. Here we present data from a Turkish cell line demonstrating that attenuation is associated with reduced ability to differentiate into microschizonts and a reduction in matrix metalloproteinase activity. We also show that attenuation results in a change in the structure of the parasite population. Using the technique of differential mRNA display, we demonstrate that gene expression profiles differ between non-attenuated and attenuated macroschizont infected leucocytes. One differentially expressed gene is of parasite origin. These data are discussed in the context of a multifactorial model for virulence.