Pathological effects and reduced survival in Rhipicephalus appendiculatus ticks infected with Theileria parva protozoa

Watt, D.; Walker, A.R.

doi:10.1007/s004360050033

Cited by 16 publications

(6 citation statements)

References 25 publications

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“…A perhaps more significant determinant of survival for parasite recombinant genotypes is the tick immune system. Infection with T. parva is detrimental to the survival of R. appendiculatus ticks (50) and, although little is known of tick immune mechanisms, insect vectors are known to deploy a number of defensive mechanisms capable of compromising parasite survival, including oxidative metabolites in the gut lumen and haemocyte activity (51–53). Preliminary evidence for selection against parasite populations in the tick has been reported for T. annulata in Hyalomma ticks (54).…”

Section: Reviewmentioning

confidence: 99%

Theileria parva and the bovine CTL response: down but not out?

McKeever

2006

Parasite Immunology

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SUMMARYTheileria parva is a tick-borne intracellular protozoan of cattle, with obligate sequential differentiation stages in lymphocytes and erythrocytes. Immunity is mediated by cytotoxic T lymphocytes (CTL) that target and clear parasitized lymphocytes but allow persistence of infected erythrocytes, which are required for transmission to the tick. The life cycle of T. parva is haploid with the exception of a brief diploid stage in the tick vector during which sexual recombination occurs. There is evidence for antigenic diversity in field parasite populations, although broad immunity can be acquired following exposure to a limited number of strains. The CTL response in individual animals is tightly focused and its specificity is strongly influenced by major histocompatibility complex (MHC) phenotype. This review discusses the issue of how CTL immunity is likely to impact on parasite population structure in the light of available information on diversity of the parasite and its ability to recombine. Keywordscattle; immune selection; population structure; Theileria parva REVIEWIn host-parasite systems that involve the reciprocal application of evolutionary pressure, or co-evolution, it has been argued that an equilibrium establishes over time between host resistance and pathogen virulence (1). This equilibrium may be based on avirulent parasites and low investment in resistance by the host, or high levels of host resistance and highly virulent parasites. Where host resistance arises from adaptive immunity, co-evolution is driven by maintenance of immune recognition by the host on the one hand and avoidance of recognition by the parasite on the other (2).Like other vector-borne pathogens, Theileria parasites face selective pressure in both ruminant host and tick vector. Much of this pressure derives from immune mechanisms involving polymorphic recognition and/or effector molecules (3,4). The genus incorporates a number of species with the capability of transforming nucleated cells to a state of uncontrolled proliferation -a trait unique among eukaryotes. One of these parasites, T. parva, causes a severe and often fatal lymphoproliferative disease of cattle known as East Coast fever (ECF) in eastern, central and southern Africa. Transmitted by Rhipicephalus appendiculatus ticks, the disease exerts substantial economic impact in the region. This arises not only from mortalities, but also from losses in production and the costs of acaricides for tick control, which is the principal means of prevention. In addition, the disease constrains dairy and beef sectors in endemic areas by limiting the introduction of Increasing prevalence of acaricide resistance in tick populations has intensified the search for alternative control measures. Available vaccination options rely on infection with live parasites and simultaneous treatment with oxytetracycline -the so-called infection and treatment method (6). Widespread uptake of this approach has been constrained by its reliance on a cold chain and, because it gives rise to a ca...

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Section: Reviewmentioning

confidence: 99%

Theileria parva and the bovine CTL response: down but not out?

McKeever

2006

Parasite Immunology

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“…It is one of the world's most widely distributed and damaging tick (Watt and Walker 2000;Ndhlovu et al 2009). It transmits a wide range of devastating, even fatal diseases of livestock including East cost fever, Corridor disease, and theileriosis (Razmi et al 2003), which are considered to be an important constraint to the development of the livestock industry in Africa (Zahid Iqbal et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Compatibility between Calpurnia aurea leaf extract, attraction aggregation, and attachment pheromone and entomopathogenic fungus Metarhizium anisopliae on viability, growth, and virulence of the pathogen

et al. 2011

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Metarhizium anisopliae sensu stricto (ss) (Metsch.) Sorok. isolate ICIPE 07 is being developed as biopesticide for the control of ticks. In addition, leaf extracts of Calpurnia aurea Benth, and the attraction aggregation and attachment pheromone (AAAP) are being used as ticks' attractant. The three agents are being considered for use in combination in an autodissemination approach, whereby ticks that are attracted to semiochemicals are infected with the inoculum. Experiments were therefore conducted to evaluate in vitro the compatibility between C. aurea, AAAP, and the M. anisopliae on vegetative growth, conidial production, and spore viability. Calpurnia aurea leaf extract was compatible with the fungus at all the concentrations tested, whereas AAAP inhibited all the fungal growth parameters. The virulence of M. anisopliae formulated in emulsifiable extracts of C. aurea was also tested against different developmental stages of Rhipicephalus appendiculatus in laboratory bioassays. No significant differences in virulence were observed between M. anisopliae applied alone and M. anisopliae formulated in different concentrations of C. aurea leaf extracts. These results suggest that C. aurea leaf extracts is compatible with M. anisopliae and could be mixed together for "spot-spray" treatments as lowcost and environmental-friendly technology to control ticks in grazing field, while AAAP should be used separately.

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“…Infection with T. parva is detrimental to the survival of R. appendiculatus ticks (31) and, although little is known of tick immune mechanisms, these are likely to mimic those seen in other arthropods. For example, Anopheles mosquitoes deploy a number of defensive mechanisms that compromise survival of malaria parasites, including oxidative metabolites in the gut lumen and hemocyte activity (4,5,11).…”

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confidence: 99%

Extensive Genotypic Diversity in a Recombining Population of the Apicomplexan ParasiteTheileria parva

et al. 2006

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We evaluated sexual recombination in the apicomplexan parasite Theileria parva using genome-wide marker analysis of haploid sporozoite populations obtained from infected Rhipicephalus appendiculatus ticks. Analysis of 231 parasite clones derived by in vitro infection of bovine lymphocytes revealed 48 distinct combinations of 64 polymorphic marker loci. One genotype accounted for more than 75% of the clones, and the population was highly inbred with respect to this. The occurrence of frequent recombination was evident from reassortment of contiguous markers in blocks, with some recombination occurring within blocks. Analysis of four polymorphic loci encoding antigens targeted by protective cytotoxic-T-lymphocyte responses confirmed that these loci reassort, both within and between chromosomes, suggesting that recombination may influence immune recognition. Marker analysis of a panel of 142 clones derived from the population after an additional passage through a calf and the same tick colony revealed 18 genotypes, with the original dominant genotype accounting for 75% of the population and a higher level of inbreeding with respect to it in the remaining clones. Selected marker analysis of genomic DNA from these stabilates and the two preceding generations of the isolate, each derived from distinct tick colonies, revealed shifts in population structure with each generation, suggesting that the tick vector may impose nonrandom selective pressure on the parasite.

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Pathological effects and reduced survival in Rhipicephalus appendiculatus ticks infected with Theileria parva protozoa

Cited by 16 publications

References 25 publications

Theileria parva and the bovine CTL response: down but not out?

Theileria parva and the bovine CTL response: down but not out?

Compatibility between Calpurnia aurea leaf extract, attraction aggregation, and attachment pheromone and entomopathogenic fungus Metarhizium anisopliae on viability, growth, and virulence of the pathogen

Extensive Genotypic Diversity in a Recombining Population of the Apicomplexan ParasiteTheileria parva

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