(1) Background: Bartonella spp. are Gram-negative, facultative, intracellular bacteria transmitted by hematophagous insects. Several species cause zoonotic diseases such as cat-scratch disease. Bartonella henselae and Bartonella clarridgeiae are the main species found in Thailand, however, there have been few studies on Bartonella spp. In addition, the hematological evaluation of Bartonella-infected animals is limited in Thailand. The aims of this study were prevalence investigation and hematological evaluation of Bartonella-infected dogs and cats residing in Bangkok, Thailand. (2) Methods: In total, 295 dogs and 513 cats were molecularly evaluated to detect Bartonella spp. using PCR with primers targeting the partial gltA, rpoB, ftsZ, ribC, and groEL genes. In total, 651 domestic animals were evaluated for hematological parameters compared between Bartonella-positive and Bartonella-negative animals. (3) Results: Overall, the prevalence of Bartonella spp. was 1.61% which was found only in free-ranging cats (2.83%). Bartonella henselae and B. clarridgeiae were confirmed from a concatenated phylogenetic tree of partial gltA and ribC genes, with 100% bootstrapping replication. For other housekeeping gene sequences, mixed infection was expected from the amplicons of rpoB, ftsZ, and groEL. Importantly, the mean corpuscular volume (MCV) was significantly increased in Bartonella-positive cats. (4) Conclusions: We suggest that B. henselae and B. clarridgeiae are important species and are still circulating in domestic animals, especially cats. The evaluation of blood parameters, especially a raised MCV, should be of concern in Bartonella infection in asymptomatic cats. Additionally, the knowledge of how to prevent Bartonella-related diseases should be promoted with people in at-risk situations.

The efficacy of antibody detection tools for all stages of Ehrlichia canis infections and for various genotypes remains unclear. We produced recombinant gp36 (rgp36) antigens from different isolates of Thai E. canis to confirm the immunoreactivities to these recombinant proteins from naturally infected dogs. Sera and blood samples were taken from 21 dogs naturally infected with E. canis and in the clinical stages of acute phase ehrlichiosis. The expression vectors and competent E. coli produced two isolates of rgp36. These two major rgp36s were recognized by the dogs' sera in Western blotting, with both anti-dog IgM and IgG used as secondary antibodies. The two different genotypes of these local recombinant immunoreactive proteins were gp36 subgroup A (isolate 1055) and subgroup B (isolate 533). The Western blot analyses successfully identified both specific IgM and IgG from the dogs' sera. Of all 21 cases, five dogs presented specific IgM, twenty dogs presented specific IgG, and the commercial test used found fifteen seropositive dogs. There were four dogs that presented both specific IgM and IgG. Only one dog presented specific IgM only. This report is the first identification of a specific IgM in dogs in response to acute infections with E. canis. The recombinant gp36 isolates may be useful as potential antigenic material for subsequent serological tests that have a high possibility for differentiating between acute, chronic, primary, and nonprimary infections with E. canis.

Background and Aim: Because of the diversity of local genotypes of Ehrlichia canis, genes targeted by TaqMan real-time polymerase chain reaction (RT-PCR) assays should be systematically evaluated. This study evaluated the amplification efficiency, linearity, precision, and sensitivity of two TaqMan RT-PCR assays targeting the dsb and gltA loci of E. canis in recombinant plasmids and naturally infected dogs. Materials and Methods: Thirty blood samples were collected from dogs showing clinical signs of canine monocytic ehrlichiosis at the Kasetsart University Veterinary Teaching Hospital, Bangkok, Thailand. The dsb and gltA genes were amplified by conventional PCRs (cPCRs) on the blood samples and were then sequenced. Meanwhile, RT-PCR was used to detect dsb and gltA genes in 10-fold dilutions of the recombinant plasmids. Results: Both dsb and gltA were amplified with a high degree of linearity (R2≥0.975 and 0.993, respectively) in all dilutions, although the mean percentage of relative standard deviation of gltA was lower, but the difference was non-significant. The detection limits of RT-PCR and cPCR were 10–7 and 10–6, respectively, for both loci. RT-PCR targeting dsb (22/30; 73.3%) and gltA (15/30; 50%) yielded a number of positive results that did not differ significantly (p=0.06). The RT-PCR positive results of the dsb gene (22/30) differed significantly from that of cPCR (11/30) (p=0.004). In contrast, the RT-PCR positive results of the gltA gene (15/30) did not differ significantly from that of cPCR (12/30) (p=0.43). The mean Ct value (30.2) based on dsb RT-PCR of 22 positive cases was higher than that of gltA RT-PCR (Ct=27.4) on 15 positive cases. The Ct values from dsb RT-PCR were >30 in all seven discordant samples that were not detected by the gltA RT-PCR. Conclusion: RT-PCR targeting the dsb gene was more sensitive for detecting E. canis in naturally infected dogs. This study suggested that TaqMan RT-PCR of the dsb gene should be selected for E. canis research in this region.