The value of in vitro cell culture of granulocytes in the detection of Ehrlichia

A Comparison of Peripheral Blood Smears, Autologous Cell Cultures, and Reverse Line Blot Hybridisation in Screening for Anaplasma/Ehrlichia in Roaming Dogs and Symptomatic Dogs in Trinidad

This study compared two methods to detect cases of canine ehrlichiosis in a field setting. One method was a polymerase chain reaction for the 16S rRNA gene followed by reverse line blot hybridisation with genera and species-specific probes for Anaplasma/Ehrlichia. The second method was an autologous cell culture of peripheral leucocytes isolated from heparinised blood and maintained in a homologous canine serum in Dulbecco's Modified Eagle medium without antibiotics. The cultures were examined under light microscopy for inclusion bodies after 48 h. Leucocytes were successfully propagated for 20 of the 34 samples submitted for autologous cell culture. Inclusion bodies were observed after cell culture in leucocytes of eight dogs. Two dogs were positive to the Anaplasma/Ehrlichia genera probe and six dogs were positive to the E. canis probe after reverse line blot hybridisation. There was acceptable agreement between reverse line blot hybridisation and cell culture results. Both reverse line blot hybridisation and autologous cell cultures can be used to detect E. canis in subclinical and clinical cases of disease. A definitive diagnosis of E. canis is best achieved by a combination of clinical signs, positive autologous cell culture, and reverse line blot hybridisation results.

The application of PCR and reverse line blot hybridization to detect arthropod-borne hemopathogens of dogs and cats in Trinidad

Arthropod-borne diseases are important causes of morbidity and mortality of companion animals in Trinidad. As clinical signs are vague, more sensitive methods to diagnose these diseases based on the polymerase chain reaction (PCR) followed by reverse line blot hybridization (RLB) of amplified products are being developed. An RLB of 14 oligonucleotide probes coupled with polymerase chain-amplified regions of 16S rRNA or 18S rRNA genes of hemoparasites from cats and dogs detected Ehrlichia canis, Anaplasma platys, Babesia canis vogeli, feline mycoplasmas ("Candidatus Mycoplasma haemominutum,"Mycoplasma haemofelis), and some unknown species within the Babesia/Theileria group and the Anaplasma/Ehrlichia tribe. Amplified products were obtained from blood samples collected from 348 dogs and 15 cats. Overall, hemopathogen DNA was detected in 92 (26.4%) dogs and six (40.0%) cats. E. canis (49, 14.1%) and feline mycoplasma (5, 33.3%) DNA were most frequently identified in dogs and cats, respectively. B. canis vogeli (1, 6.7%) and E. canis (1, 6.7%) were also detected in cats. Mixed infections of Anaplasma/Ehrlichia sp. and Babesia sp. were present in five (1.4%) dogs, while mixed infections of the feline mycoplasmas were present in two (13.3%) cats, one of which was also positive for E. canis. Pyrexia was significantly associated with a positive RLB result in dogs (P= 0.00, chi(2), 1 df). This is the first reported application of macro-arraying techniques to detect arthropod-borne hemopathogens of companion animals in the Americas and the first detection of DNA of B. canis vogeli and E. canis in cats in Trinidad.