Molecular detection and characterization of tick-borne hemoparasites and Anaplasmataceae in dogs in major cities of Malawi

Tick-borne pathogens (TBPs) in dogs have attracted much attention over the last decade since some are now known to be zoonotic and pose a threat to both animal and human health sectors. Despite the increase in the number of studies on canine TBPs worldwide, only a few studies have been conducted in resource-limited countries where research priority is given to food animals than companion animals. In the present study, the occurrence of TBPs of the genera Babesia, Hepatozoon, Anaplasma, and Ehrlichia was investigated in 209 owned and stray dogs in three major cities in Malawi through molecular techniques. Among the examined dogs, 93 (44.5%) were infected with at least one TBP. The detection rates were 23.1% for Babesia rossi, 2.9% for B. vogeli, 19.1% for Hepatozoon canis, 2.4% for Anaplasma platys, and 3.8% for Ehrlichia canis. This is the first molecular study that has provided evidence that dogs in Malawi are infected with TBPs. Sensitization is required for veterinary practitioners, dog handlers, and pet owners as the detected pathogens affect the animals' wellbeing. Further studies focusing on rural areas with limited or no access to veterinary care are required to ascertain the extent of the TBP infection in dogs.

First molecular detection of Ehrlichia canis and Anaplasma platys in ticks from dogs in Cebu, Philippines

Ehrlichia canis infection of dogs in the Philippines has been detected by serological and peripheral blood smear examination methods, but not by molecular means. Anaplasma platys infection in dogs has not yet been officially reported, although it is suspected to occur in the country. Thus, sensitive and specific molecular techniques were used in this study to demonstrate the presence of both E. canis and A. platys in the Philippines. A total of 164 Rhipicephalus sanguineus ticks was collected from 36 dogs. Seven tick samples were found positive with E. canis and one sample with A. platys. To further characterize these pathogens, molecular analyses based on citrate synthase and heat-shock operon genes were also performed. Philippine strains were found to be not divergent from strains from other countries. The present results are the first molecular detection and analyses of E. canis and A. platys in ticks from dogs in the Philippines.

Molecular evidence of a new strain of Ehrlichia canis from South America

Blood samples from dogs with clinical signs compatible with ehrlichiosis were examined for infection of Ehrlichia canis using PCR, multiplex real-time PCR, and DNA sequencing analysis. Eleven of 25 samples were positive for a new strain of E. canis. This is the first molecular identification of E. canis infection in dogs from Peru.

Restriction and expansion of Ehrlichia strain diversity

Ehrlichia are tick-borne gram negative, obligately intracellular bacteria. The 16S rRNA gene DNA sequences are highly conserved among strains of each Ehrlichia species. The 28-kDa/Map-1 outer membrane protein genes are highly diversified among strains of Ehrlichia chaffeensis and E. ruminantium, but are highly conserved among E. canis isolates. The diversity of the immunodominant proteins of E. chaffeensis and E. ruminantium in contrast with the conservation of the immunodominant proteins of E. canis suggests that E. chaffeensis and E. ruminantium face more host immune pressure than E. canis or that E. chaffeensis and E. ruminantium evolved earlier than E. canis and have diverged.

The genome of the obligately intracellular bacterium Ehrlichia canis reveals themes of complex membrane structure and immune evasion strategies

Ehrlichia canis, a small obligately intracellular, tick-transmitted, gram-negative, alpha-proteobacterium, is the primary etiologic agent of globally distributed canine monocytic ehrlichiosis. Complete genome sequencing revealed that the E. canis genome consists of a single circular chromosome of 1,315,030 bp predicted to encode 925 proteins, 40 stable RNA species, 17 putative pseudogenes, and a substantial proportion of noncoding sequence (27%). Interesting genome features include a large set of proteins with transmembrane helices and/or signal sequences and a unique serine-threonine bias associated with the potential for O glycosylation that was prominent in proteins associated with pathogen-host interactions. Furthermore, two paralogous protein families associated with immune evasion were identified, one of which contains poly(G-C) tracts, suggesting that they may play a role in phase variation and facilitation of persistent infections. Genes associated with pathogen-host interactions were identified, including a small group encoding proteins (n = 12) with tandem repeats and another group encoding proteins with eukaryote-like ankyrin domains (n = 7).

Analysis of 16S rRNA gene sequences of Ehrlichia canis, Anaplasma platys, and Wolbachia species from canine blood in Japan

In the present study, three canine blood samples from Japan, that were suspected to be ehrlichia positive were examined. After sequencing the 16S rRNA genes, each dog was found to be infected either with Ehrlichia canis (Kagoshima 1), Anaplasma platys (Okinawa 1), or Wolbachia sp. (Okinawa 2). Phylogenic analysis was performed on these sequences. The nearly entire 16S rRNA sequence of Kagoshima 1 was found to be most similar to the sequences from Oklahoma and Venezuela E. canis strains (1 base pair difference out of 1,387, 99.9% sequence identity). The 16S rRNA gene sequence of Okinawa 1 showed the closest DNA identity to the French strain of A. platys (1 base deletion out of 1,385 bp, 99.6% sequence identity). The 16S rRNA gene sequence of Okinawa 2 illustrated the closest DNA identity to that of a Wolbachia sp. from Dirofilaria immitis (98.9% sequence similarity). These data imply a low diversity within E. canis strains and within A. platys strains, including those strains reported in this study. This is also the first demonstration of Wolbachia DNA in dog blood, suggesting the involvement of Wolbachia sp. in canine febrile illnesses.