Serologic and Molecular Diagnosis of Anaplasma platys and Ehrlichia canis Infection in Dogs in an Endemic Region

[Overview on utility of in-house tests for detection of systemic infectious diseases in dogs]

For detection of infectious diseases, several point-of-care (POC) tests are on the market in addition to methods performed in commercial laboratories. These POC tests are based on enzyme-linked immunosorbent assay (ELISA) or other immunochromatographic technologies and present results within few minutes in veterinary practice. This article gives an overview of the utility of numerous POC tests of different manufacturers for detection of parvovirus antigen in feces, Dirofilaria (D.) immitis antigen in blood as well as antibodies against Borrelia (B.) burgdorferi, Anaplasma (A.) spp., Ehrlichia (E.) spp., Leptospira (L.) spp. and Leishmania (L.) infantum in blood (single or in different combinations). Sensitivity and specificity of these tests are important for their usefulness in veterinary practice. Furthermore, presence of antibodies or detection of antigen has to correlate with the presence of clinical signs. POC tests for detection of canine parvovirus antigen have a very high specificity, the sensitivity of all evaluated POC tests, however, is very low. POC tests for detection of D. immitis antigen have a very high sensitivity and specificity. As they detect antigen from the uterus of female adult parasites, test results are negative when only very few female or only male adults are present. POC tests for detection of antibodies against B. burgdorferi only indicate contact with Borrelia spp. and do not prove clinical Lyme disease, as the infection only extremely rarely causes clinical signs. POC tests for detection of antibodies against A. phagocytophilum are also not suitable for diagnosis of clinical anaplasmosis. Infections with A. phagocytophilum only lead to clinical disease in very rare cases and in these, clinical signs occur before the development of antibodies. POC tests for detection of antibodies against E. canis have a very high sensitivity as well as specificity. POC tests for detection of antibodies against L. infantum and Leptospira species (spp.) show a very high specificity and a high sensitivity. However, Leptospira spp. antibody-positive results may occur following vaccination, as the POC tests cannot distinguish between field and vaccination strains.

Molecular detection and phylogeny of Ehrlichia canis and Anaplasma platys in naturally infected dogs in Central and Northeast Thailand

Background and Aim

Ehrlichia canis and Anaplasma platys are tick-borne, Gram-negative bacteria that cause canine monocytic ehrlichiosis and canine cyclic thrombocytopenia, respectively. These diseases are of great importance and are distributed globally. This study aimed to create new primers for the identification of E. canis and A. platys in naturally infected dogs using polymerase chain reaction (PCR), DNA sequencing, and phylogenetic analysis using the 16S rDNA and gltA genes.

Materials and Methods

In total, 120 blood samples were collected from dogs in three different locations (Saraburi, Buriram, and Nakhon Ratchasima provinces) in Central and Northeast Thailand. The molecular prevalence of E. canis and A. platys was assessed using PCR targeting the 16S rDNA and gltA genes. All positive PCR amplicons were sequenced, and phylogenetic trees were constructed based on the maximum likelihood method.

Results

Ehrlichia canis had an overall molecular prevalence of 15.8% based on the 16S rDNA gene, compared to 8.3% based on the gltA gene. In addition, the overall molecular prevalence of A. platys using the 16S rDNA gene was 10.8%, while the prevalence rate was 5.8% using the gltA gene. Coinfection was 0.8% in Saraburi province. The partial sequences of the 16S rDNA and gltA genes of E. canis and A. platys in dogs in Central and Northeast Thailand showed 96.75%-100% identity to reference sequences in GenBank. Phylogenetic analysis of the 16S rDNA and gltA genes revealed that E. canis and A. platys sequences were clearly grouped into their own clades.

Conclusion

This study demonstrated the molecular prevalence of E. canis and A. platys in Central and Northeast Thailand. The 16S rDNA and gltA genes were useful for the diagnosis of E. canis and A. platys. Based on the phylogenetic analysis, the partial sequences of the 16S rDNA and gltA genes in E. canis and A. platys were related to prior Thai strains and those from other countries.

Erythrocyte sedimentation rate, C-reactive protein, and interleukin-6 as inflammatory biomarkers in dogs naturally infected with Ehrlichia canis

Background and Aim

Canine monocytotropic ehrlichiosis (CME), a tick-borne disease, leads to a systemic inflammatory response syndrome; it is thus important to assess the intensity of inflammation in order to treat it appropriately. The current study was designed to evaluate hematological, biochemical, and inflammatory parameters in dogs naturally infected with Ehrlichia canis compared with those in healthy dogs. We also assessed the relationship among several inflammation-related parameters and considered these parameters for use as inflammatory biomarkers of CME.

Materials and Methods

Twenty-eight dogs were divided into two groups based on the results of nested polymerase chain reaction for detecting E. canis, comprising a healthy group (n=11) and an infected group (n=17). A blood sample was collected from each dog to evaluate hematological, biochemical, and inflammatory parameters, with the obtained results being statistically compared between the groups. Moreover, the correlations of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and interleukin-6 (IL-6) were investigated in the 28 dogs.

Results

In the infected group, the mean levels of red blood cells, hemoglobin, and hematocrit were significantly lower than in the healthy group, while the mean lymphocyte and monocyte counts were higher. The mean levels of ESR and CRP were significantly higher (p<0.05) in the infected group, whereas no significant differences were found in IL-6 levels between the two groups. In the correlation analysis, ESR and CRP levels were highly correlated (p<0.01, r=0.531).

Conclusion

Elevated ESR and CRP levels were found in dogs naturally infected with E. canis, which also presented mild to moderate inflammation in this study. Moreover, CRP was significantly correlated with ESR, so ESR and CRP may serve as inflammatory biomarkers for monitoring CME.

Molecular Detection of Ehrlichia canis in the Pet-Dog Population in R. N. Macedonia

Canine monocytic ehrlichiosis (CME) is a widespread, tick-borne, canine disease, caused by an obligate intracellular bacterium, Ehrlichia canis. The main vector, a brown-dog tick, Rhipicephalus sanguineus, is widely distributed, especially in areas with tropic, subtropic, or Mediterranean climates (Central and South America, Eastern and Western Asia, Africa, Australia and Southern Europe). The study performed in 2012, by Stefanovska et al., determined a seroprevalence of 18.7% of E. canis among the Macedonian dog population. Up to date, the presence of E. canis, using molecular diagnostic methods, has not been investigated in Macedonia. Therefore, this study aimed to confirm the presence of E. canis, in the pet-dog population on the territory of the city of Skopje, North Macedonia, using a highly sensitive multiplex Real-Time PCR method (qPCR). Whole blood samples from 80 dogs of different breeds and ages, with clinical symptoms of CME and positive serology result for the presence of antibodies against E.canis, were collected for analyses. Out of 80 dogs, 36 (45%) were found as positive. The present work reports the first molecular detection of E. canis in pet dogs on the territory of the city of Skopje, Macedonia.

Molecular detection and characterization of Anaplasma platys and Ehrlichia canis in dogs from the Caribbean

Anaplasma platys is a tick-transmitted rickettsial pathogen, which is known to be the etiologic agent for cyclic thrombocytopenia in its primary canine host. Infections with this pathogen are also reported in cats, cattle and people. Similarly, Ehrlichia canis is another tick-borne rickettsial pathogen responsible for canine monocytic ehrlichiosis and is also reported to cause infections in people. We describe infections in dogs with these two pathogens on the Caribbean island of Grenada, West Indies by detection using molecular methods. We utilized a 16S rRNA gene-based PCR assay to detect both Ehrlichia and Anaplasma species by screening 155 canine blood samples from asymptomatic dogs. We found 18.7 % of the dogs to be positive for A. platys and 16.8 % for E. canis. Samples that tested positive for A. platys were further assessed by sequence analysis targeting 16S rRNA, 23S rRNA, citrate synthase (gltA) and heat shock protein (groEL) genes. Phylogenetic analysis revealed high correlation of A. platys 16S rRNA and gltA gene sequences with the geographic origins, while 23S rRNA and groEL gene sequences clustered independent of the geographic origins. This study represents an important step in defining the widespread distribution of active rickettsial infections in Caribbean dogs with no apparent clinical signs, thus posing a high risk for canine health and to a lesser extent to humans, as most dogs in the Caribbean are free-roaming.

Development of a Multiplex PCR and Magnetic DNA Capture Assay for Detecting Six Species Pathogens of the Genera Anaplasma and Ehrlichia in Canine, Bovine, Caprine and Ovine Blood Samples from Grenada, West Indies

Infections with tick-borne pathogens belonging to Anaplasma/Ehrlichia in various vertebrate hosts are a persistent problem resulting in nonspecific clinical signs during early infection. Diagnosis of single and multi-infections with these pathogens, causing diseases in companion/agricultural animals and people, remains a challenge. Traditional methods of diagnosis, such as microscopy and serology, have low sensitivity and specificity. Polymerase chain reaction (PCR) assays are widely used to detect early-phase infections, since these have high sensitivity and specificity. We report the development and validation of an assay involving PCR followed by magnetic capture method using species-specific oligonucleotides to detect six Anaplasma/Ehrlichia species pathogens in canine, bovine, caprine, and ovine blood samples. Overall, the assay application to 455 samples detected 30.1% (137/455) positives for one or more out of six screened pathogens. Single-pathogen infections were observed in 94.9% (130/137) of the positive samples, while co-infections were detected in 5.1% (7/137). Anaplasma marginale infection in cattle had the highest detection rate (34.4%), followed by canines positive for Anaplasma platys (16.4%) and Ehrlichia canis (13.9%). The assay aided in documenting the first molecular evidence for A. marginale in cattle and small ruminants and Ehrlichia chaffeensis and Ehrlichia ewingii in dogs in the Caribbean island of Grenada.