We previously culture isolated a strain of Ehrlichia canis, the causative agent of canine ehrlichiosis, from a human in Venezuela. In the present study, we examined whether dogs and ticks are infected with E. canis in Venezuela and, if so, whether this is the same strain as the human isolate. PCR analysis using E. canis-specific primers revealed that 17 of the 55 dog blood samples (31%) and all three pools of four Rhipicephalus sanguineus ticks each were positive. An ehrlichial agent (Venezuelan dog Ehrlichia [VDE]) was isolated and propagated in cell culture from one dog sample and was further analyzed to determine its molecular and antigenic characteristics. The 16S rRNA 1,408-bp sequence of the new VDE isolate was identical to that of the previously reported Venezuelan human Ehrlichia isolate (VHE) and was closely related (99.9%) to that of E. canis Oklahoma. The 5 (333-bp) and 3 (653-bp) sequences of the variable regions of the 16S rRNA genes from six additional E. canis-positive dog blood specimens and from three pooled-tick specimens were also identical to those of VHE. Western blot analysis of serum samples from three dogs infected with VDE by using several ehrlichial antigens revealed that the antigenic profile of the VDE was similar to the profiles of VHE and E. canis Oklahoma. Identical 16S rRNA gene sequences among ehrlichial organisms from dogs, ticks, and a human in the same geographic region in Venezuela and similar antigenic profiles between the dog and human isolates suggest that dogs serve as a reservoir of human E. canis infection and that R. sanguineus, which occasionally bites humans residing or traveling in this region, serves as a vector. This is the first report of culture isolation and antigenic characterization of an ehrlichial agent from a dog in South America, as well as the first molecular characterization of E. canis directly from naturally infected ticks.

Blood specimens from clinically normal military dogs and their trainers, in Lara, Venezuela were screened for Anaplasma platys, A. phagocytophilum, or Ehrlichia ewingii using 16S rRNA PCR tests. Sixteen percent (7/ 43) of dog specimens were positive by A. platys PCR test followed by sequencing of the PCR products, and all human blood specimens [25] were negative. All specimens from these dogs and humans were PCR negative for E. ewingii or A. phagocytophilum. Twelve Rhipicephalus sanguineus ticks removed from these dogs were negative for A. platys by reverse transcription PCR test. Almost the entire 16S rRNA gene (1,364 bp) and groESL operon (1,646 bp) sequences of A. platys isolated from a dog were determined, revealing that both sequences were closely related to the sequences of an A. platys strain detected in R. sanguineus ticks from the Democratic Republic of Congo.

Anaplasma platys infects peripheral blood platelets and causes infectious cyclic thrombocytopenia in canines.The genes, proteins, and antigens of A. platys are largely unknown, and an antigen for serodiagnosis of A. platys has not yet been identified. In this study, we cloned the A. platys major outer membrane protein cluster, including the P44/Msp2 expression locus (p44ES/msp2ES) and outer membrane protein (OMP), using DNA isolated from the blood of four naturally infected dogs from Venezuela and Taiwan

El objetivo del estudio fue determinar la participación de la garrapata Rhipicephalus sanguineus en la transmisión de Anaplasma platys en caninos. Se inoculó un canino con una cepa de A. platys y una vez que desarrolló parasitemia confirmada por frotis y por PCR, se le infestó con ninfas y adultos de R. sanguineus. Se colectaron las garrapatas ingurgitadas, se colectó el intestino y la glándula salival de las garrapatas alimentadas en el canino inoculado y se realizó un PCR. No se amplificó ADN de A. platys en el macerado de ninfas, en adultos pos-muda sin alimentar, o en adultos alimentados del canino inoculado experimentalmente. Los resultados indican que la R. sanguineus no participa en la transmisión de A. platys.