Study of virulence and vector transmission of Babesia bovis by use of cloned parasite lines

Timms, Peter; Stewart, N. P.; Vos, A.J. De

doi:10.1128/iai.58.7.2171-2176.1990

Cited by 47 publications

(23 citation statements)

References 16 publications

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“…In this study, vaccine 'breakthroughs' (HO and SC) isolated from two vaccinated animals experiencing clinical tropical theileriosis was compared. An important consideration is whether cell line vaccine strains themselves can revert to virulence (Timms et al, 1990). The Teylovac genotype was not detected in either of the 'breakthrough' isolates and clinical disease was attributed to field challenge.…”

Section: Discussionmentioning

confidence: 99%

Infection dynamics of Theileria annulata over a disease season following cell line vaccination

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et al. 2019

Veterinary Parasitology

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Tropical theileriosis is a tick-borne haemoparasitic disease of cattle caused by the protozoan parasite Theileria annulata. Globally, the economic impact of the disease is immense and enhanced control measures would improve livestock production in endemic regions. Immunisation with a live attenuated vaccine is an effective and widely used control method, however, the repeated use of live vaccines may have an impact on the field parasite population at a genetic level. Additionally, there has been an increasing number of reports of vaccine breakthrough cases in recent years. Thus, the present study was designed to evaluate the genetic composition of a parasite population over a disease season in a locality where live cell line vaccination is practised. A diverse range of parasite genotypes was identified and every T. annulata positive cattle blood sample harboured multiple parasite genotypes. An alteration in the major genotype and an increasing multiplicity of infection in individual animals was observed over the course of the disease season. Vaccination status was found not to effect within-host multiplicity of infection, while a significantly higher number of genotypes was detected in grazed cattle compared to non-grazed ones. A degree of genetic isolation was evident between parasite populations on a micro-geographic scale, which has not been reported previously for T. annulata. Analysis of parasite genotypes in vaccinated animals suggested only a transient effect of the vaccine genotype on the genetic diversity of the T. annulata population. The vaccine genotype was not detected among clones of two vaccine 'breakthrough' isolates and there is no suggestion that it was responsible for disease. The obtained data indicated that in the system studied there is no apparent risk of introducing the vaccine genotype into the population with only a transient effect on the genetic diversity of the parasite population during the disease season.

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Section: Discussionmentioning

confidence: 99%

Infection dynamics of Theileria annulata over a disease season following cell line vaccination

Bilgiç

Aksulu

Bakırcı

et al. 2019

Veterinary Parasitology

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“…22 It has been suggested that field isolates consist of subpopulations, each expressing virulence genes to varying degrees and that serial passage in splenectomised calves selects populations enriched with faster growing avirulent phenotypes. 23 A change of strain used in the vaccine was generally made in response to field evidence of vaccine failures (Figure 1). Early immunisation strategies involved revaccination with at least one different vaccine strain.…”

Section: Immunity To Heterologous Challengementioning

confidence: 99%

“…Studies with clones of B bovis showed that protective immunity was unrelated to virulence with none of the clones giving as good protection as the parent strain. 27 Using a limiting dilution method, Timms et al 23 were able to infect splenectomised calves by the intravenous inoculation of one B bovis parasite. However, De Vos 26 showed that the infectivity of diluted vaccine parasites given subcutaneously became variable at 10 5 with only three of five animals becoming infected, but when the dose was infective there was no difference between the number of B bovis organisms and the severity of the infections observed.…”

Section: Effect Of Virulence Dose Rate and Route Of Vaccination On Imentioning

confidence: 99%

Immunity following use of Australian tick fever vaccine: a review of the evidence

Bock

Vos

2001

Aust Veterinary J

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Objective To review the evidence available on the degree and duration of immunity provided by Australian tick fever vaccines against Babesia bovis, B bigeminaand Anaplasma marginale infections in Australia and overseas. Background Vaccines containing attenuated strains of B bovis and B bigemina as well as A centrale grown in splenectomised calves have been used in Australia since 1964 to immunise cattle against tick fever. About 800,000 doses of vaccine are supplied annually and much of the evidence for protection is field evidence rather than conventional immunological measures or pen trials. Conclusions Immunity to Babesia bovis and B bigemina – A single inoculation generally provides sound, long‐lasting protection both in Australia and overseas. No evidence was found of a loss of immunity with time. Vaccine failures to B bovis d o occur, but are uncommon and evidently caused by a number of factors, including immune responsiveness of the vaccinated animals, and immunogenicity of the vaccine strain. Immunity to Anaplasma marginale– The vaccine containing A centrale provides partial, variable protection against A marginale. Protection against challenge in Australia is adequate in most cases to prevent disease and use of the vaccine in this country appears to be justified. Protection against antigenically diverse, highly virulent stocks of A marginale i n other countries is, at times, clearly inadequate and better vaccines are required in situations where the challenge is severe.

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“…99 Two mechanisms, based on the selection of parasite subpopulations combined with the ability of the selected parasites to vary genetically have been suggested as causing attenuation. 100 A wide variety of genotypes has been found among B. bovis isolates in Australia. 101‐103 The proportions of B. bovis subpopulations can change with continuous cultivation, therefore, unless facilities are available for monitoring the changes and testing the parasite immunogenicity, long‐term culture for vaccine production might not be recommended.…”

Section: Culture‐grown Babesia Sppmentioning

confidence: 99%

Culture‐Derived Parasites in Vaccination of Cattle against Tick‐Borne Diseases

Shkap¹,

Pipano²

2000

Annals of the New York Academy of Sciences

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The major economically important tick‐borne diseases of cattle are theileriosis, babesiosis, anaplasmosis, and cowdriosis. Culture‐derived attenuated schizonts of Theileria annulata have proved to be safe for all types of cattle and they protect against tick‐borne theileriosis. T. parva was also successfully grown in vitro; however, inoculation of cattle with allogeneic schizont‐infected cells resulted in rejection and destruction of the parasites together with the host cells. The number of schizont‐infected cells needed for immunization is greater than for T. annulata theileriosis. Culture‐propagated Babesia bovis and B. bigemina were used for large scale vaccination in the field. An avirulent population of Babesia spp. was obtained by in vitro cloning; inoculation of cattle did not induce clinical babesiosis, but produced specific antibodies. Culture‐derived exoantigens of Babesia spp. proved to be completely safe for cattle, however, they conferred less protection than live parasites. Cell‐cultured Cowdria ruminantium was highly infective for susceptible animals but, attenuated in vitro, could offer a potential source for vaccination. Anaplasma marginale, successfully grown in tick cell culture, may be developed for vaccines. Factors that should be considered in the developing of vaccines against tick‐borne diseases include: the protective immune response to the pathogenic parasite developmental stages, virulence, immunological strain differences, and antigenic variations in cattle and in culture.

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Study of virulence and vector transmission of Babesia bovis by use of cloned parasite lines

Cited by 47 publications

References 16 publications

Infection dynamics of Theileria annulata over a disease season following cell line vaccination

Infection dynamics of Theileria annulata over a disease season following cell line vaccination

Immunity following use of Australian tick fever vaccine: a review of the evidence

Culture‐Derived Parasites in Vaccination of Cattle against Tick‐Borne Diseases

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