Abstract. This article presents two case reports of Anaplasma platys detection in two women from Venezuela. Both patients were exposed to Rhipicephalus sanguineus, the presumed tick vector, and experienced chronic, nonspecific clinical signs including headaches and muscle pains. Intra-platelet inclusion bodies resembling A. platys were observed in buffy coat smears and A. platys DNA was amplified and sequenced from whole blood; however, treatment with doxycycline did not alleviate their symptoms. These cases provide further support for A. platys as a zoonotic tick-borne pathogen, most likely of low pathogenicity; nonetheless, the cause of illness in humans by A. platys is yet to be confirmed.

Abstract. Since 1982 Ehrlichia platys, now emended as Anaplasma platys, has been diagnosed in dogs from Maracaibo, Venezuela, using buffy coat smears stained with Dip Quick. Three dogs were inoculated with an A. platys strain. When parasitemia reached 60-97%, blood samples obtained from the inoculated dogs and from two naturally infected dogs were centrifuged to obtain platelet-rich plasma, which was mixed with 0.1% glutaraldehyde at 37 C for 10 minutes. Platelet pellets were fixed in 3% glutaraldehyde for 72 hours and processed for conventional transmission electron microscopy. Platelets contained pleomorphic organisms with a distinct double membrane that was not observed when the bodies were in a determinate developmental stage. There were 1-15 individual bodies included in a host cell vacuole. The organisms had an electron-lucent inner area, whereas the internal surface of their inner plasma membranes exhibited an electron-dense rough substance. In naturally infected dogs, organisms with different ultrastructural features were found inside the same platelet. Some organisms contained central dense material surrounded by a pale zone, which was in turn surrounded by a moderately dense peripheral area. Other organisms contained an eccentrically electron-dense material. The intravacuolar space appeared fully electron-lucent. Each organism usually exhibited inner fine strands. Empty structures displaying junctions with the vacuolar membrane were observed. Our results indicate that distinct ultrastructural characteristics are associated with different stages of A. platys development and may differ among A. platys strains.

Since 1982, Ehrlichia platys infection has been diagnosed in canines from Venezuela by the use of buffy coat smears. In 1992, ehrlichia-like bodies were observed in platelets from a severely ill girl by light microscopy. The patient was seropositive to E. chaffeensis by the indirect fluorescent antibody test (IFAT). Tetracycline was administered and the patient recovered. More than 400 cases with such intra-platelet organisms have been studied at this laboratory over the past 6 years, and all the patients had a good response to the treatment. To determine whether the organisms in human blood platelets were truly platelet ehrlichiae, IFAT and transmission electron microscopy (TEM) studies were undertaken in four patients. Light microscopic examination of blood samples revealed the dense organism inside platelets, and a great reactivity of the blood cells. Sera from the four patients were seronegative against E. chaffeensis and E. platys antigens. Three of four samples contained the intra-platelet organisms when examined by TEM. Electron microscopy showed platelets with vacuoles containing pleomorphic organisms. These organisms had a thickened membrane, an electron-translucent inner area and an electron-dense granular component in the periphery. An abundant electron-dense material was observed surrounding them. The ultrastructure of such micro-organisms has not been reported previously. Based on the similarity of many of their characteristics with rickettsiae, we suggest that the microorganisms found in the present study might belong to the family Rickettsiaceae.

Highlights Trypanosoma vivax strains exhibit different virulence and pathogenicity patterns. TvMT1 strain showed low virulence and high pathogenicity. TvLIEM176 strain showed high virulence and moderate pathogenicity. Protein expression varies in high virulence/moderate pathogenicity strain vs low virulence/high pathogenicity strain.

The studies on three -dimensional structure of healthy animal blood platelets are scarce, and the three -dimensional characteristics of blood platelets infected by some type of external agent that causes disease have not been reported up to now. The goal of the present research was the determination of the three -dimensional structure of platelets infected with Ehrlichia platys, which has been diagnosed in platelets from dogs of Maracaibo -Venezuela, using light and transmission electron microscopy techniques. Blood samples were taken from dogs with symptoms of ehrlichiosis and healthy dogs, given by Veterinary Sciences Faculty of University of Zulia. Each one of these samples was centrifuged to obtain platelet -rich plasma (PRP). A drop of this PRP was pipetted directly onto a circular cover glass and glutaraldehyde 3% was added. After one hour, the sample was processed following the scanning electron microscopy (SEM) conventional technique and observed in a SEM Phillips XL 30. Infected platelets were pleomorphic and were 4.3 to 5.4 µm in diameter, with projections emerging from their external surface. Platelets displayed 7 to 13 short projections, with blunt aspect in their ends (figure 1), which were 0.2 to 0.8 of µm in length and located throughout the platelet surface. Some platelets displayed small protuberances on their surface (figure 2), whereas others only showed certain convolutions. Larger pseudopods than the rest of the surface projections were also distinguished (figure 3). Small apertures were randomly visualized in platelet membrane. A slight roughness in the membrane was demonstrated. These findings demonstrate an alteration of the platelet surface when it is infected by a bacteriological agent that causes a disease.