Non-archetypal Type II-like and atypical strains of Toxoplasma gondii infecting marsupials of Australia

Australia is geographically isolated and possesses a remarkable diversity of wildlife species. Marsupials are highly susceptible to infection with the cosmopolitan parasite Toxoplasma gondii. Of 46 marsupials screened for T. gondii by multilocus PCR-DNA sequencing at polymorphic genes (B1, SAG3, GRA6, GRA7), 12 were PCR-positive; the majority (67%; 9/12) were infected by non-archetypal Type II-like or atypical strains. Six novel alleles were detected at B1, indicating greater diversity of genotypes than previously envisaged. Two isolates lethal to marsupials, were avirulent to mice. The data support the conclusion that Australia's isolation may have favoured the persistence of non-archetypal ancestral genotypes

A fluorescent based PCR assay for the detection and quantitation of Giardia duodenalis genotypes in mixed populations

A method based on the polymerase chain reaction has been developed for differentiating between genotypically and phenotypically distinct strains of Giardia duodenalis and quantifying the amount of initial template of the different genotypes in mixed populations. The assay relies on a sequence-specific probe, labelled with two fluorescent dyes, designed to bind within the small subunit ribosomal (SSU) RNA gene. This target region is amplified by primers specific for either Group 1 or Group 2-type isolates of G. duodenalis and the probe binds within the primer-targeted region. This quantitative method takes advantage of the 5′ nuclease activity of Taq DNA polymerase, which, on encountering a probe bound within the target DNA sequence cleaves it, causing it to become dissociated from the template. When the two fluorescent dyes bound to the probe are in close proximity (when the probe is intact), the interaction of the two dyes prevents the reporter dye from fluorescing. However, during the extension phase of amplification, the activity of the DNA polymerase causes the dyes to become separated and hence the reporter dye increases its fluorescent intensity. This release of fluorescence is directly related to the amplified amount of target template. This assay was developed with the aim of providing a unique method with which to investigate interactions within mixed populations of genetically distinct strains of G. duodenalis

Seroprevalence of Toxoplasma gondii in wild kangaroos using an ELISA

Infection with Toxoplasma gondii is a significant problem in Australian marsupials, and can lead to devastating disease and predispose animals to predation. T. gondii infection in kangaroos is also of public health significance due to the kangaroo meat trade. A moderate seroprevalence of T. gondii was observed in a study of western grey kangaroos located in the Perth metropolitan area in Western Australia. Of 219 kangaroos tested, 15.5% (95%CI: 10.7–20.3) were positive for T. gondii antibodies using an ELISA developed to detect T. gondii IgG in macropod marsupials. When compared with the commercially available MAT (modified agglutination test), the ELISA developed was in absolute agreement and yielded a κ coefficient of 1.00. Of 18 kangaroos tested for the presence of T. gondii DNA by PCR, the 9 ELISA positive kangaroos tested PCR positive and the 9 ELISA negative kangaroos tested PCR negative indicating the ELISA protocol was both highly specific and sensitive and correlated 100% with the more labour intensive PCR assay.N. Parameswaran, R. M. O'Handley, M. E. Grigg, S. G. Fenwick and R. C. A. Thompso

Russell and Rubinstein's Pathology of Tumors of the Nervous System. Sixth Edition

An increasing number of parasites are being added to the list of those that can be transmitted via food or water and that pose a risk to human health if ingested. These zoonotic infections usually have complicated life cycles requiring a number of hosts for completion or a diversity of cycles of transmission that may interact. The challenge in all control efforts is to break the cycle of transmission that may lead to human infection, which requires the ability to detect and characterize the relevant parasite life cycle stage in food or water. This requires tools that are both sensitive and specific, and often beyond the limitations of conventional techniques such as microscopy