146 research outputs found
Tick‐borne infectious diseases in Australia
No full textTick bites in Australia can lead to a variety of illnesses in patients. These include infection, allergies, paralysis, autoimmune disease, post-infection fatigue and Australian multisystem disorder. Rickettsial (Rickettsia spp.) infections (Queensland tick typhus, Flinders Island spotted fever and Australian spotted fever) and Q fever (Coxiella burnetii) are the only systemic bacterial infections that are known to be transmitted by tick bites in Australia. Three species of local ticks transmit bacterial infection following a tick bite: the paralysis tick (Ixodes holocyclus) is endemic on the east coast of Australia and causes Queensland tick typhus due to R. australis and Q fever due to C. burnetii; the ornate kangaroo tick (Amblyomma triguttatum) occurs throughout much of northern, central and western Australia and causes Q fever; and the southern reptile tick (Bothriocroton hydrosauri) is found mainly in south-eastern Australia and causes Flinders Island spotted fever due to R. honei. Much about Australian ticks and the medical outcomes following tick bites remains unknown. Further research is required to increase understanding of these areas.No Full Tex
Novel rickettsia in ticks, Tasmania, Australia
No full textA novel rickettsia was detected in Ixodes tasmani ticks collected from Tasmanian devils. A total of 55% were positive for the citrate synthase gene by quantitative PCR. According to current criteria for rickettsia speciation, this new rickettsia qualifies as Candidatus Rickettsia tasmanensis, named after the location of its detection
Molecular characterisation of Australian Coxiella burnetii isolates
No full textThe intracellular bacterium Coxiella burnetii is the causative agent of Q fever, a human zoonotic disease with acute and chronic forms, which is most commonly associated with exposure to infected animals such as sheep, goats and cattle. Q fever occurs worldwide and is endemic in Australia with around 300 cases confirmed by laboratory testing each year. Although the first cases of the disease were first recognised in Australia in the 1930s, at the start of this study little was known about the molecular epidemiology of C. burnetii in this country. The work presented in this thesis provides the first extensive molecular analysis of the strains of the bacterium causing Q fever in Australia.
The small, pre-existing collection of seven Australian C. burnetii isolates was expanded to a larger collection comprising 43 isolates. The majority of the new isolates were obtained from serum samples taken from acute Q fever patients during the early stage of their disease in a two year period from 2010-2012. This demonstrated that the organisms remained viable in these specimens despite the absence of host cells, thus acute serum is a valuable source of C. burnetii. Attempted isolations of C. burnetii from kangaroo faeces and an Australian wombat tick were unsuccessful but bacterial DNA was obtained from these samples for further characterisation.
Several genotyping methods were used to characterise the Australian C. burnetii isolate collection at the molecular level. All the human isolates were found to contain the plasmid QpRS and were negative for the acute disease antigen A gene. Single nucleotide polymorphism typing also failed to discriminate between the human isolates but demonstrated that C. burnetii representing three different genotypes was present in the kangaroo faecal samples. Discrimination between the human isolates was only achieved using an extended panel of PCRs targeting the repetitive insertion sequence element IS1111 and multi-locus VNTR analysis. Both methods identified 14 genotypes, most of which were novel compared to the genotypes identified in characterised strains of C. burnetii from other countries and in combination the two methods determined 24 genotypes, providing an even greater discriminatory power. Many of the genotyping targets were not amplified from the bacterial DNA in the wombat tick leading to the conclusion that the organism present was a Coxiella species other than C.burnetii.
Overall, results showed that the Australian C. burnetii isolates are genetically closely related and unique to this country. The evaluation of different genotyping methods enabled the development of a set of guidelines that will reduce the cost and workload required to characterise new Australian isolates of this important pathogen
The detection of Coxiella burnetii (Q fever) in clinical and environmental samples
No full textThe zoonotic intracellular bacterium Coxiella burnetii is the cause of the human disease Q fever. Coxiella burnetii can be shed by infected animals, can survive harsh environments and has been shown to persist within the human host. The detection and isolation of this bacterium is difficult due to its intracellular nature. In order to detect minimal concentrations of this bacterium in various clinical and environmental samples, highly sensitive assays were needed. A duplex real-time polymerase chain reaction (qPCR) assay was developed to detect C. burnetii DNA (targeting the Com1 gene and the IS1111a gene). This assay was then tested on a variety of environmental and clinical sample types.
Samples (such as water, soil, aerosols, blood and bone marrow) were spiked with C. burnetii (either living cell cultures or formalin killed cells) to determine the optimal method for extracting and detecting C. burnetii DNA. The silica column method followed by qPCR assay of the Com1 gene was shown to have a sensitivity of approximately 1100 copies/litre in water, 1900 copies/kg in soil, 870 copies/litre in milk, and seven copies/litre of air. When the same technique was applied to clinical samples the silica column method proved to be the most effective in purifying DNA from the small cell variant of C. burnetii and effectively removed potential PCR inhibitors from mock clinical samples of blood, plasma, serum and bone marrow. However, because the qPCR cannot differentiate between viable and non-viable C. burnetii DNA it was important to establish a sensitive assay for the detection of viable C. burnetii in order to investigate persistent infections and to obtain isolates of the bacteria from cases of Q fever for further studies.
As isolation of Coxiella can be achieved using cell culture or animal inoculation these methods were compared for their sensitivity for C. burnetii detection. Vero and DH82 cell lines were the most sensitive for cell culture isolation of the Arandale and Henzerling isolates of C. burnetii respectively. When cell culture was compared to PCR and inoculation of severely combined immunodeficient (SCID) mice it was found that inoculation of SCID mice followed by euthanasia (at day 42) and removal and analysis of the spleen was the most sensitive method for the detection of viable C. burnetii.
It has recently been hypothesised that genetic differences between isolates of C. burnetii are responsible for differences in pathogenicity and disease outcomes. Hence the differences between Australian isolates were investigated. Seven new Australian isolates of C. burnetii were genetically analysed by conventional PCR of insertion sequences and detection of the acute disease antigen A (adaA) gene. Six Australian isolates of C. burnetii were placed in geno-group III but were negative for the adaA gene. One new Australian isolate (Poowong) was placed in geno-group II and was positive for the adaA gene. The Poowong isolate was from a seronegative asymptomatic patient, with bacteraemia detected by PCR in four initial samples as well as all 12 blood samples taken over a one month period. Through sequencing of 468bp of the ankyrin gene (ankH sequenced in triplicate) it was shown that the Poowong isolate had two base pair differences compared to the Henzerling isolate (also genogroup II) and the Nine Mile isolate (geno-group I). This demonstrates that the Poowong isolate can be distinguished from the other isolates within the laboratory.
The optimal methods of detection as determined in this study were used to analyse and evaluate clinical specimens. Blood samples (serum, plasma and peripheral blood mononuclear cells) from 12 patients infected during an outbreak of Q fever in Newport UK in 2002 were examined. Cell culture of the peripheral blood mononuclear cells (PBMC) demonstrated that no viable C. burnetii cells were present. In contrast, six of the spleens from SCID mice inoculated with the PBMCs were positive for C. burnetii DNA (by Com1 qPCR) and six were positive for C. burnetii antigen (by IFA). However, only two were positive for both. This suggests that in some patients low numbers of viable C. burnetii cells persist and in others C. burnetii persist as nonviable antigen.
In conclusion, this study demonstrated sensitive and specific optimal methods for the detection of C. burnetii in clinical and environmental samples, the optimal method for isolation of C. burnetii, the application of these methods on a number of clinical samples and the characterisation of seven new isolates, including an isolate from a highly unusual asymptomatic case that is genetically unique from the others. This study has also shown that the pathogenesis of C. burnetii infection in humans and the effect of genetic differences in isolates on pathogenesis are far from adequately understood. The optimal methods of detection, isolation and grouping determined in this study will have an effect on future studies and will allow a greater understanding of C. burnetii and its persistence, both in the environment and in Q fever infections
in raw meat intended for pet consumption
No full textThe discovery of antibodies against Coxiella burnetii in cattery‐confined breeding cats indicating prior or current exposure (Shapiro et al. , 2015) prompted an investigation into possible sources of infection. One hypothesis was that raw meat diets containing reservoir species may provide a source of C. burnetii transmission. The aim of this pilot study was to determine whether C. burnetii DNA was present in raw meat sold exclusively for companion animal consumption. The sample population consisted of raw meat packages (n = 58) of primarily kangaroo origin, with three to four aliquots (50–120 mg) randomly selected from each package. Genomic DNA was extracted from whole tissue in each of these aliquots using a modified protocol. Three quantitative PCR assays were used for the detection of C. burnetii targeting the IS1111 gene, the heat shock operon htpAB and the C. burnetii outer membrane protein‐coding gene, com1 . Coxiella burnetii DNA was detected in 25/58 samples (43%) using the IS1111 , htpAB and/or com1 PCR assays and confirmed by DNA sequencing. All samples amplifying a product in the com1 assay also amplified a product in the htpAB and IS1111 assays. A total of 17/58 (29%) packets were positive with all three genes, 4/58 (7%) were positive with two genes (IS1111 and htpAB ) and 4/58 (7%) were positive with the IS1111 gene only. Coxiella burnetii DNA was five times more likely to be found in offal than skeletal muscle meat samples. All meat samples in which C. burnetii DNA was found were from kangaroo tissues, while samples labelled as non‐kangaroo meat (n = 4) were negative. Multi‐locus variable number of tandem repeat analysis (MLVA) identified three different genotypes of C. burnetii that have all been identified previously from Australian human clinical Q fever cases. Further investigations are required to determine the potential role of certain raw meats in the transmission of C. burnetii to cats and humans.No Full Tex
Q fever immunology: the quest for a safe and effective vaccine
No full textAbstract Q fever is an infectious zoonotic disease, caused by the Gram-negative bacterium Coxiella burnetii. Transmission occurs from livestock to humans through inhalation of a survival form of the bacterium, the Small Cell Variant, often via handling of animal parturition products. Q fever manifests as an acute self-limiting febrile illness or as a chronic disease with complications such as vasculitis and endocarditis. The current preventative human Q fever vaccine Q-VAX poses limitations on its worldwide implementation due to reactogenic responses in pre-sensitized individuals. Many strategies have been undertaken to develop a universal Q fever vaccine but with little success to date. The mechanisms of the underlying reactogenic responses remain only partially understood and are important factors in the development of a safe Q fever vaccine. This review provides an overview of previous and current experimental vaccines developed for use against Q fever and proposes approaches to develop a vaccine that establishes immunological memory while eliminating harmful reactogenic responses
Scrub Typhus and Molecular Characterization of Orientia tsutsugamushi from Central Nepal
No full textScrub typhus is a vector-borne, acute febrile illness caused by Orientia tsutsugamushi. Scrub typhus continues to be an important but neglected tropical disease in Nepal. Information on this pathogen in Nepal is limited to serological surveys with little information available on molecular methods to detect O. tsutsugamushi. Limited information exists on the genetic diversity of this pathogen. A total of 282 blood samples were obtained from patients with suspected scrub typhus from central Nepal and 84 (30%) were positive for O. tsutsugamushi by 16S rRNA qPCR. Positive samples were further subjected to 56 kDa and 47 kDa molecular typing and molecularly compared to other O. tsutsugamushi strains. Phylogenetic analysis revealed that Nepalese O. tsutsugamushi strains largely cluster together and cluster away from other O. tsutsugamushi strains from Asia and elsewhere. One exception was the sample of Nepal_1, with its partial 56 kDa sequence clustering more closely with non-Nepalese O. tsutsugamushi 56 kDa sequences, potentially indicating that homologous recombination may influence the genetic diversity of strains in this region. Knowledge on the circulating strains in Nepal is important to the development of diagnostic tests and vaccines to support public health measures to control scrub typhus in this country
Molecular detection of Rickettsia sp. genotype RF2125 from household dogs in the central highlands of Vietnam
No full textRickettsia felis, a zoonotic vector-borne bacteria, is reported globally in humans, animals, and its invertebrate hosts. This study was designed to detect antibodies against R. felis and the DNA of R. felis in blood of domestic dogs in the Central Highlands of Vietnam using immunofluorescence antibody test (IFAT), and ompB- and gltA-PCRs, respectively. Using IFAT, 23 out of 338 plasma samples collected from household dogs were seropositive for R. felis, accounting for 6.80% (CI 95%: 4.45-10.1%). Of 171 buffy coat samples from household dogs, 50 were positive for spotted fever group rickettsioses using ompB-PCR assay, accounting for 29.2% (CI 95%: 22.6-36.7%). The gltA-PCR assay detected R. felis in 30% (15/50) of ompB-positive samples. DNA sequencing of ompB-PCR and gltA-PCR products confirmed the presence of R. felis and Rickettsia sp. genotype RF2125 / R. asembonensis. Our findings suggest a potential risk of R. felis infection in the communities in the Central Highlands of Vietnam, and the reservoir role of dogs to Rickettsia sp. genotype RF2125.No Full Tex
The presence of Rickettsia felis in communities in the central highlands of Vietnam
No full textRickettsia felis is an emerging flea-borne spotted fever pathogen that causes febrile illness in humans. In Vietnam, R. felis was detected in hospitalized patients, but there is no information on its presence in the Vietnamese community. This cross-sectional study aimed to determine the presence of R. felis in humans of the Central Highlands of Vietnam. A total of 158 blood and 213 serum samples were subjected to PCR and IFAT, respectively, to detect the presence of R. felis DNA and antibodies against R. felis. PCR assays detected R. felis DNA in four out of 158 blood samples, accounting for a prevalence of 2.53 % (95 % CI: 0.81 %-6.76 %). Phylogenetic analysis indicated the presence of R. felis and R. felis genotype RF2125 in the communities in the Central Highlands of Vietnam. The result of IFAT identified seven out of 213 serum samples (3.29 %, 95 % CI: 1.45 %-6.93 %) positive for antibodies against R. felis. This study was the first to demonstrate the presence of active R. felis infections in the communities in the Central Highlands of Vietnam utilizing both molecular and serological methods.No Full Tex
Foreign tick smuggling rickettsia evades Australian border control
No full textTick‐borne infectious diseases, including rickettsial infections, acquired in Australia or after international travel remain a diagnostic challenge.1No Full Tex
- …
