First Detection of Ehrlichia canis in Cerebrospinal Fluid From a Nonthrombocytopenic Dog with Meningoencephalitis By Broad-Range PCR

Molecular Detection and Characterization of Hemotropic Mycoplasma in Assamese Macaques (Macaca assamensis) of Northern Thailand

Hemotropic mycoplasmas, also known as hemoplasmas, are parasitic bacteria that infect red blood cells, potentially leading to varying degrees of anemia across numerous mammalian species, including nonhuman primates. The present study aims to investigate the prevalence of hemoplasma infection and identify the species involved among free-ranging Assamese macaques (Macaca assamensis) inhabiting northern Thailand. A total of 133 blood samples were collected from Assamese macaques in Chiang Rai province, Thailand, and subjected to screening for hemoplasma infection utilizing nested PCR amplification targeting the 16S rRNA gene. Positive samples were subsequently analyzed through nucleotide sequencing and phylogenetic analysis for putative species identification. Current study results revealed that 17.3% (23/133; 95% CI 11.29-24.81) of Assamese macaques tested positive for hemoplasma infection using the nested PCR assay. Partial 16S rRNA sequences derived from hemoplasma isolates in Assamese macaques exhibited 99% homology, forming a cluster within the same phylogenetic clade as "Candidatus Mycoplasma haematomacacae," previously identified in long-tailed macaques, rhesus macaques, and Japanese macaques. These findings suggest the presence of "Ca. M. haematomacacae" not only in long-tailed macaques and rhesus macaques but also in Assamese macaques in Thailand. To our knowledge, this marks the first molecular detection of "Ca. M. haematomacacae" in Assamese macaques in Thailand. These results hold significance as they enhance our understanding of hemoplasma infection distribution among macaque populations in Thailand.

Bacterial DNA and osteoarthritis in dogs with patellar luxation and cranial cruciate ligament rupture

Background and Aim

The association between bacterial DNA in stifle joints, including those with cranial cruciate ligament rupture (CCLR) and medial patellar luxation (MPL), and osteoarthritis in dogs remains elusive. This study investigated the potential association between the detection of bacterial DNA and osteoarthritis in dogs using a broad-range polymerase chain reaction technique targeting the 16S ribosomal RNA gene.

Materials and Methods

Synovial fluid (35 samples) and knee tissue samples (32 samples) were obtained from 35 dogs diagnosed with CCLR (n = 20; 11 males and nine females) or MPL (n = 15; five males and 10 females) who underwent a surgical operation between October 2014 and April 2015.

Results

Dogs with CCLR had a higher average osteoarthritis score than those with MPL (2.0 ± 0.9 vs. 0.5 ± 0.9; p = 0.005). Bacterial DNA was detected in the stifle joints of 60.71% of dogs with MPL. Pelomonas spp. (25.00%), Halomonas spp. (17.86%), and 5 other species (17.86%) were the most frequently identified bacteria. Bacterial DNA was detected in 41.03% of dogs with CCLR. Pelomonas spp. (15.38%), Sphingomonas spp. (10.26%), Halomonas spp. (5.13%), and 4 other species (10.26%) were the most frequently identified bacteria. No significant difference was observed in the prevalence of bacterial DNA obtained from tissue samples (46.88%) or joint fluid samples (51.43%). The presence of bacterial DNA was not associated with the type of knee injury (MPL or CCLR; p = 1.000). There was a higher prevalence of bacterial DNA in samples from dogs with moderate-to-severe osteoarthritis (94.44%) than in those with minimal osteoarthritis (41.18%), and a significant association between the presence of bacterial DNA and moderate-to-severe osteoarthritis was identified (p < 0.01).

Conclusion

Dogs with moderate-to-severe osteoarthritis were more likely to have bacterial DNA in their stifle joints than those with no or minimal osteoarthritis. These findings provide valuable insight into the potential role of bacterial DNA in joint tissue or joint fluid and the development of osteoarthritis in dogs.

Suppurative spinal meningomyelitis in a dog with intra-neutrophilic cerebrospinal fluid cells Ehrlichia canis morulae

A 2-year-old castrated male Creole Shepherd mixed dog was presented for non-ambulatory paraparesis of the pelvic limbs. The magnetic resonance imaging and cerebrospinal fluid (CSF) analysis were consistent with meningomyelitis. Positive serology for Ehrlichia canis/Ehrlichia ewingii suggested exposure to a pathogen; qPCR on the serum and the CSF confirmed active infection. Ehrlichial morulae were observed within CSF and peripheral blood polymorphonuclear neutrophils; a species-specific PCR confirmed E. canis infection. This is an interesting report of E. canis infection in a dog with morulae observed in neutrophils both in the peripheral blood and CSF.

Systematic evaluation of TaqMan real-time polymerase chain reaction assays targeting the dsb and gltA loci of Ehrlichia canis in recombinant plasmids and naturally infected dogs

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.

Molecular Detection of Bartonella quintana among Long-Tailed Macaques (Macaca fascicularis) in Thailand

Bartonella quintana is a zoonotic pathogen with a worldwide distribution. Humans and non-human primates are considered to be natural reservoir hosts for B. quintana. However, information on the molecular epidemiology of this organism is very limited in regard to long-tailed macaques (Macaca fascicularis) in Thailand. Therefore, this study aimed to investigate the occurrence and genetic diversity of Bartonella spp. among long-tailed macaques in Thailand. In total, 856 blood samples were collected from long-tailed macaques in Thailand. All specimens were screened for Bartonella spp. using a polymerase chain reaction (PCR) assay targeting the 16S rRNA, gltA and ftsZ genes. All positive samples were further analyzed based on nucleotide sequencing, phylogenetic analysis and multiple sequence alignment analysis. Only one macaque showed a positive result in the PCR assays based on the 16S rRNA, gltA and ftsZ genes. Nucleotide sequencing and phylogenetic analysis revealed that the obtained sequences were closely related to B. quintana previously detected in non-human primates. Single-nucleotide polymorphisms (SNPs) were detected in the gltA and ftsZ gene sequences. This study revealed that long-tailed macaques in Thailand carried B. quintana. Despite the low infection rate detected, long-tailed macaques may be a reservoir of B. quintana.

Detection and genetic characterization of "Candidatus Mycoplasma haemomacaque" infection among long-tailed macaques (Macaca fascicularis) in Thailand using broad-range nested polymerase chain reaction assay

Background and Aim

Hemoplasmas are defined as small, epicellular parasitic bacteria that can infect the red blood cells of several mammalian species. Diseases caused by these bacteria range from asymptomatic infections to acute hemolytic anemia. However, data on hemoplasmas in non-human primates in Thailand remain to be limited. Therefore, this study aims to determine the occurrence and genetic diversity of hemoplasmas among long-tailed macaques in Thailand.

Materials and Methods

Blood samples were collected from 339 long-tailed macaques in three provinces of Thailand. DNA was then extracted from the blood samples and tested for hemoplasma using broad-range nested polymerase chain reaction (PCR) based on the 16S rRNA gene. PCR-positive samples were sequenced, and phylogenetic analysis for species identification was conducted.

Results

In total, 38 (11.2%) out of the 339 samples were found to be positive for hemoplasmas, based on the broad-range nested PCR assay of the 16S rRNA gene. The 16S rRNA sequences of Mycoplasma spp. were highly similar (98-99% identity) to "Candidatus Mycoplasma haemomacaque." Furthermore, phylogenetic analysis using maximum likelihood demonstrated that the sequences were located in the same cluster of "Ca. M. haemomacaque."

Conclusion

The detection of hemoplasmas among long-tailed macaques in Thailand is reported. Genetic characterization confirmed that these hemoplasmas are closely related to "Ca. M. haemomacaque." These results indicate that long-tailed macaques in several locations in Thailand may be infected and serve as reservoirs for this parasite.

Detection of specific IgM and IgG antibodies in acute canine monocytic ehrlichiosis that recognize recombinant gp36 antigens

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.

Identification of uncultured bacteria from abscesses of exotic pet animals using broad-range nested 16S rRNA polymerase chain reaction and Sanger sequencing

Background:

The Sanger sequencing technique has been questioned and challenged by advanced high-throughput sequencing approaches. Sanger sequencing seems to be an obsolete technology. However, there are still research problems that could be answered using the Sanger sequencing technology. Fastidious obligate anaerobic bacteria are mostly associated with abscesses in animals. These bacteria are difficult to isolate from abscesses and are frequently excluded due to the bias of conventional bacterial culturing.

Aim:

This study demonstrated the usefulness of a broad-range polymerase chain reaction (PCR) with Sanger sequencing to identify the majority population of bacteria in abscesses from exotic pet animals.

Materials and Methods:

This study performed a pilot investigation of abscesses from 20 clinical cases (17 rabbits, 2 hedgehogs, and 1 sugar glider) using standard culture methods for both aerobes and anaerobes and broad-range nested PCR targeting the 16S rRNA gene followed by the Sanger sequencing technique.

Results:

The standard culture and PCR techniques detected bacteria in 9 and 17 of 20 samples, respectively. From the 17 sequencings of the 16S rRNA, 10 PCR products were found to be closely related with obligate anaerobes including Bacteroides spp., Fusobacterium spp., Prevotella spp. Phylogenetic analysis using the rpoB gene revealed that the species for the Bacteroides was thetaiotaomicron and for the Fusobacterium was varium and nucleatum. However, the amplification of the rpoB gene for the Prevotella spp. was unsuccessful. Correlations between the standard culture and PCR techniques were found in 9 (6 positive and 3 negative samples) of 20 samples. Eleven samples were discordant between the standard culture and PCR techniques which were composed of eight samples negative by culture but positive by PCR and three samples had different bacteria by the culture and PCR techniques.

Conclusion:

According to this study, broad-range PCR combined with Sanger sequencing might be useful for the detection of dominant anaerobic bacteria in abscesses that were overlooked based on conventional bacterial culture.

Neospora caninum and Ehrlichia canis co-infection in a dog with meningoencephalitis

An 8-year-old mixed-breed dog was presented for acute, progressive weakness and ataxia, inappetence, and weight loss. The patient was mentally normal, but nonambulatory, with a right head tilt, right positional ventral strabismus, and slight head tremors. A neurologic lesion was localized to the cerebellum and right brainstem. Cerebrospinal fluid (CSF) analysis showed a markedly increased protein concentration and mixed pleocytosis, with eosinophil predominance (44%), intracytoplasmic inclusions within eosinophils, consistent with Ehrlichia canis (E canis) morulae, and Toxoplasma gondii (T gondii) or Neospora caninum (N caninum) tachyzoites within eosinophils and monocytes. A serum indirect immunofluorescent antibody test was positive for N caninum (titer 1:12 800) and negative for T gondii. Both blood and CSF PCR results were N caninum- and E canis-positive and T gondii- and Anaplasma phagocytophilum-negative, and blood PCR, but not CSF PCR, was Hepatozoon canis-positive. The dog was treated for 30 days with clindamycin, sulfamethoxazole-trimethoprim, doxycycline, prednisone, and cephalosporin, but did not improve neurologically, and was euthanized. Brain histopathology showed moderate multifocal, subacute meningoencephalitis with necrosis and gliosis. The neurologic disease was mostly attributed to central nervous system (CNS) neosporosis, with the possible contribution of ehrlichiosis, which was likely a manifestation of blood-brain barrier disruption. Hepatozoonosis was probably a result or cause of underlying immunosuppression. To our knowledge, this is the first report of CNSN caninum and E canis co-infection detected by both CSF PCR and cytology and E canis morulae identified within CSF eosinophils.

Efficacy of Minocycline in Naturally Occurring Nonacute Ehrlichia canis Infection in Dogs

BACKGROUND

Minocycline has been used in the treatment of Ehrlichia canis infection in dogs as an alternative to doxycycline, the recommended treatment. However, efficacy of this alternative therapy is unknown.

OBJECTIVE

To assess the efficacy of minocycline in the treatment of natural occurring E. canis infection in dogs.

ANIMALS

Ten privately owned dogs of mixed breed positive for E. canis by blood PCR.

METHODS

Prospective, randomized clinical study. Dogs positive for E. canis by PCR were housed in a kennel environment and randomly allocated to receive doxycycline 10 mg/kg bodyweight PO once daily ("gold standard" control group) or minocycline (extralabel) 10 mg/kg bodyweight PO twice daily (treatment test group) for 28 days. Blood, analyzed by PCR to determine the presence or absence of E. canisDNA, was collected weekly during treatment starting on the first day of treatment and including through day 35, 7 days after the last treatment.

RESULTS

In both groups, one dog tested negative after 7 days of treatment. For the doxycycline group, the latest time to a negative PCR test was after 3 weeks of treatment. For the minocycline group, the latest time was on day 28 of treatment. All dogs tested negative 7 days after the end of treatment.

CONCLUSION AND CLINICAL IMPORTANCE

Minocycline can be an effective alternative to doxycycline for clearing E. canis from the blood in nonacute infections.

Canine Monocytic Ehrlichiosis: An Update on Diagnosis and Treatment

Canine monocytic ehrlichiosis (CME) is a tick-borne disease of worldwide distribution. The major causative agent is Ehrlichia canis, a gram-negative, obligate intracellular, pleomorphic bacterium of the genus Ehrlichia, which infects monocytes, macrophages and lymphocytes, forming intracytoplasmic, membrane-bound bacterial aggregates, called morulae. After an incubation period of 8-20 days, the course of E. canis infection, can be sequentially divided into acute, subclinical and chronic phases, although these phases can hardly be distinguished in the clinical setting. Clinical recovery is the typical outcome of acutely infected dogs, entering the subclinical phase, during which they show no or minimal clinical signs and/or mild hematological abnormalities. Immunocompetent dogs may eliminate the infection during the acute or subclinical phases, but an unpredictable proportion of dogs will eventually develop the chronic phase, characterized by aplastic pancytopenia and high mortality, due to septicemia and/or severe bleeding. This article outlines briefly the pathogenesis of CME due to E. canis, and more thoroughly reviews the recent scientific literature pertaining to the diagnosis and treatment of this devastating disease.

Association of Ehrlichia canis, Hemotropic Mycoplasma spp. and Anaplasma platys and severe anemia in dogs in Thailand

Canine tick-borne bacteria; Ehrlichia canis, hemotropic Mycoplasma spp. and Anaplasma spp., are organisms transmitted by Rhipicephalus sanguineus ticks. However, only a few clinical studies evaluating dogs infected with these organisms and anemia condition have been published. In this study, the potential tick-borne bacteria linked to anemia were investigated in eighty-one blood samples selected from anemic dogs using a broad range nested-PCR of the 16S rRNA gene. Positive results were shown in 12/81 blood specimens (14.81%). Nucleotide sequences from the PCR products were analyzed using BLAST and resulted in identification of Ehrlichia canis (8), Candidatus Mycoplasma haematoparvum (1) and Anaplasma platys (3). Two other PCR assays were used to detect and identify the positive results of these pathogens including a specific PCR for Ehrlichia canis (gp36) and a specific nested-PCR for hemoplasma species (16S rRNA) and the phylogenetic analyses of E. canis and canine hemoplasmas were performed using these two loci. These specific PCRs revealed co-infection of E. canis and Mycoplasma haemocanis in two cases. These two male dogs had presented with jaundice, severe hemolytic anemia, severe thrombocytopenia, leukocytosis, mild azotemia and hepatitis. Ehrlichia canis was detected in a significantly greater number of severe anemia cases (PCV<15%) than moderate or mild anemia cases (PCV 16-29%) (P<0.05) and these severe anemia cases were 7-fold more at risk of having E. canis infections (odds ratio: 7.11, p=0.020). However, no statistical differences were detected between E. canis detection and degrees of thrombocytopenia or leukopenia. From the results of this study, we conclude that the severity of anemia is associated with E. canis infections rather than the severity of thrombocytopenia.