Multiplex Detection of Ehrlichia and Anaplasma Pathogens in Vertebrate and Tick Hosts by Real-Time RT-PCR

A new quantitative PCR method for the detection of Anaplasma platys in dogs based on the citrate synthase gene

Anaplasma platys is an obligate intracellular bacterium that primarily affects dogs, but it can also infect humans. Our study aimed to standardize a quantitative real-time (q)PCR method using the citrate synthase gene (gltA) as a specific target for A. platys detection in naturally infected dogs. Primers (gltA84F and gltA84R) and probe (PLATYSp) were designed to amplify an 84-bp fragment based on the gltA gene sequences of A. platys available in GenBank. A total of 186 dog blood samples originating from the Brazilian state of Rio de Janeiro were tested by qPCR. Additionally, the same samples were tested by cytology and a nested (n)PCR that targeted the 16S ribosomal DNA to determine the performance of our qPCR method compared to these existing techniques. Among the samples tested with qPCR, 17.2% were considered positive, significantly more than detected by nPCR (14.0%). Under optical microscopy, inclusions were observed in platelets of 25.3% of the samples, and among these samples, only 33.9% were identified as positive for A. platys using qPCR. The qPCR technique proved to be more specific than cytology and to have superior sensitivity to nPCR for detecting A. platys in dogs. The development of this new qPCR method contributes to the advancement of research involving A. platys Furthermore, it can be used to quantify the presence of this bacterium to evaluate the treatment of infected animals, or even as a more sensitive and specific tool for situations indicating possible clinical disease but with negative cytology.

Detection of Anaplasma marginale and A. phagocytophilum in bovine peripheral blood samples by duplex real-time reverse transcriptase PCR assay

Insufficient diagnostic sensitivity and specificity coupled with the potential for cross-reactivity among closely related Anaplasma species has made the accurate determination of infection status problematic. A method for the development of simplex and duplex real-time quantitative reverse transcriptase PCR (qRT-PCR) assays for the detection of A. marginale and A. phagocytophilum 16S rRNA in plasma-free bovine peripheral blood samples is described. The duplex assay was able to detect as few as 100 copies of 16S rRNA of both A. marginale and A. phagocytophilum in the same reaction. The ratio of 16S rRNA to 16S DNA copies for A. marginale was determined to be 117.9:1 (95% confidence interval [95% CI], 100.7:1, 135.2:1). Therefore, the detection limit is the minimum infective unit of one A. marginale bacterium. The duplex assay detected nonequivalent molar ratios as high as 100-fold. Additionally, the duplex assay and a competitive enzyme-linked immunosorbent assay (cELISA) were used to screen 237 samples collected from herds in which anaplasmosis was endemic. When the cELISA was evaluated by the results of the qRT-PCR, its sensitivity and specificity for the detection of A. marginale infection were found to be 65.2% (95% CI, 55.3%, 75.1%) and 97.3% (95% CI, 94.7%, 99.9%), respectively. A. phagocytophilum infection was not detected in the samples analyzed. One- and two-way receiver operator characteristic curves were constructed in order to recommend the optimum negative cutoff value for the cELISA. Percentages of inhibition of 20 and 15.3% were recommended for the one- and two-way curves, respectively. In conclusion, the duplex real-time qRT-PCR assay is a highly sensitive and specific diagnostic tool for the accurate and precise detection of A. marginale and A. phagocytophilum infections in cattle.

Identification of Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato in patients with erythema migrans

Anaplasma phagocytophilum has been first isolated from the blood of two Czech patients simultaneously with a cultivation of Borrelia burgdorferi sensu lato from their erythema migrans lesions. Cultivation of different Borrelia spp. from 12 erythema migrans biopsies, from 2 blood, one liquor and one placenta sample in BSK-H medium was successful. Adapted conventional methods targeting 16S rRNA and OspA genes for real-time polymerase chain reaction (PCR) and partial sequencing of these genes together with microscopical examinations of the blood smears provided a direct detection of the B. afzelii, B. burgdorferi, B. garinii, B. valaisiana and B. bissettii in the skin, B. garinii in the blood, placenta and liquor in 24 (36.3 %) patients, and A. phagocytophilum in 10 (15 %) patients with erythema migrans. Positive indirect IgM immunofluorescence against Anaplasma sp. was obtained in 7 cases, specific IgG antibodies were detected in 12 patients. Three women suffering from erythema migrans in the first trimester had positive PCR for Anaplasma and/or for Borrelia in the blood and two of them, later, in the placenta. Interpretation of laboratory data can bring important contribution to establishing the role of Anaplasma sp. in erythema migrans and forming the principle of precaution with laboratory diagnosis during pregnancy which always should be reflected in the resistance of Anaplasma sp. toward penicillins.

Ecological havoc, the rise of white-tailed deer, and the emergence of Amblyomma americanum-associated zoonoses in the United States

Two infectious diseases, and one presumably infectious disease, each vectored by or associated with the bite of the lone star tick (Amblyomma americanum), were identified and characterized by clinicians and scientists in the United States during the 1980s and 1990s. These three conditions-human monocytic (or monocytotropic) ehrlichiosis (HME), Ehrlichia ewingii ehrlichiosis, and southern tick-associated rash illness (STARI)-undoubtedly existed in the United States prior to this time. However, the near-simultaneous recognition of these diseases is remarkable and suggests the involvement of a unifying process that thrust multiple pathogens into the sphere of human recognition. Previous works by other investigators have emphasized the pivotal role of white-tailed deer (Odocoileus virginianus) in the emergence of Lyme disease, human babesiosis, and human granulocytic anaplasmosis. Because whitetails serve as a keystone host for all stages of lone star ticks, and an important reservoir host for Ehrlichia chaffeensis, E. ewingii, and Borrelia lonestari, the near-exponential growth of white-tailed deer populations that occurred in the eastern United States during the twentieth century is likely to have dramatically affected the frequency and distribution of A. americanum-associated zoonoses. This chapter describes the natural histories of the pathogens definitively or putatively associated with HME, E. ewingii ehrlichiosis, and STARI; the role of white-tailed deer as hosts to lone star ticks and the agents of these diseases; and the cascade of ecologic disturbances to the landscape of the United States that have occurred during the last 200 years that provided critical leverage in the proliferation of white-tailed deer, and ultimately resulted in the emergence of these diseases in human populations.