Optimization of a molecular method for the diagnosis of canine babesiosis

Canine piroplasmids: Molecular detection and laboratory characterization in dogs from Brasilia, Brazil, with the first molecular evidence of dog exposure to a novel opossum-associated Babesia sp

Canine piroplasmid infections can be caused by Babesia spp., Theileria spp. and Rangelia vitalii. In Brazil, canine babesiosis caused by Babesia vogeli is endemic and reported throughout the country. On the other hand, Rangeliosis caused by R. vitalii has only been described so far in the South and Southeast regions. Despite that, studies analyzing the laboratory and molecular characterization of these hemoprotozoa are still scarce. To investigate the occurrence, the laboratory features, the molecular characterization, and the diversity of piroplasmids from Midwestern Brazil, a survey was performed using blood samples obtained from 276 domestic dogs from Brasília, Federal District, Midwestern Brazil. A broad-range quantitative PCR (qPCR) targeting the mitochondrial large subunit ribosomal DNA (LSU4) was used to detect piroplasmid DNA. The overall molecular occurrence of piroplasmids was 11.2% (31/276), with 9.7% (27/276) of the sequences identified as Babesia vogeli (98-100% identity to B. vogeli isolate from the USA). Based on a partial 18S rRNA sequence pairwise alignment (-250 bp), 1.4% (4/276) of the sequences showed only 76.8% identity with B. vogeli but 100% identity with opossum-associated Babesia sp. (MW290046-53). These findings suggest the exposure of dogs from Brazil to a recently described Babesia sp. isolated from white-eared opossum. None of the analyzed dogs was positive for Theileria spp. or R. vitalii. Subsequently, all positive sequences were submitted to three additional PCR assays based on the 18S rRNA, cox-1, and cytb genes, aiming at performing a haplotype network analysis. Haplotype network using cox-1 sequences showed the presence of six different haplotypes of B. vogeli; one of them was shared with isolates from Brazil, the USA, and India. When including animals co-infected with other vector-borne diseases, piroplasmid-positive dogs had 2.3 times higher chance of having thrombocytopenia than the negative ones. The molecular results demonstrated that the compared Babesia vogeli sequences showed a low variability as well as evidence of exposure to a putative novel opossum-associated Babesia sp. in dogs from Midwestern Brazil.

Identification and phylogenetic analysis of Babesia parasites in domestic dogs in Nigeria

The present study examined the presence of Babesia parasites in 104 domestic dogs in Nigeria. Sequentially, Babesia parasites infecting domestic dogs underwent genetic and phylogenetic analyses. The results of nested PCR based on the Piroplasmida 18S rRNA gene illustrated that 13.5% (14/104) of the samples were positive. The obtained positive samples determined the nucleotide sequences of the 18S rRNA genes. In the genetic and phylogenetic analyses, four of five nucleotide sequences were similar to Babesia canis rossi, and one sample exhibited a close similarity to a Babesia sp. isolated from a raccoon in Hokkaido, Japan. The present study revealed the widespread presence of B. canis rossi among domestic dogs in Nigeria.

Canine babesiosis: A literature review of prevalence, distribution, and diagnosis in Latin America and the Caribbean

Canine babesiosis is a tick-borne disease with worldwide distribution and global significance. Traditionally, canine babesiosis was caused by B. canis (large Babesia) and B. gibsoni (small Babesia) based on cytological examination of stained blood smears. Currently, molecular techniques have demonstrated that several Babesia species infect dogs: B. canis, B. vogeli, and B. rossi (large forms) and B. gibsoni, B. conradae, and B. vulpes (small forms). In this study, we compiled and reviewed currently available data on Babesia infections in dogs in Latin America and the Caribbean, as well as on distribution of Babesia species with respect to prevalence, geographic location, and methods of detection. Forty-three studies on canine babesiosis published from 2005 to 2019 were included. The publications retrieved reported three species of Babesia (B. vogeli, B. gibsoni, and B. caballi) based on molecular confirmation of the species. Babesia vogeli was reported in Mexico, Costa Rica, Granada, Haiti, Nicaragua, Saint Kitts and Nevis, Trinidad and Tobago, Argentina, Brazil, Chile, Colombia, Paraguay, Peru, and Venezuela. In contrast, B. gibsoni was recorded in Costa Rica, Nicaragua, Saint Kitts and Nevis, and Brazil. Babesia caballi was found in a dog from Brazil. Babesia prevalence in dogs varied considerably based on parasite species and geographic location, with values close zero to 26.2%. Besides molecular techniques such as PCR, studies included examination of blood smears by microscopy and/or serologic tests. Few countries in the region, e.g., Brazil and Costa Rica, possess profound data availability, whereas the majority of them have scarce information or no data. A deeper understanding of the ecology and epidemiology of Babesia spp. in dogs is needed for the region.

Detection of Babesia canis vogeli and Hepatozoon canis in canine blood by a single-tube real-time fluorescence resonance energy transfer polymerase chain reaction assay and melting curve analysis

A real-time fluorescence resonance energy transfer polymerase chain reaction (qFRET PCR) coupled with melting curve analysis was developed for detection of Babesia canis vogeli and Hepatozoon canis infections in canine blood samples in a single tube assay. The target of the assay was a region within the 18S ribosomal RNA gene amplified in either species by a single pair of primers. Following amplification from the DNA of infected dog blood, a fluorescence melting curve analysis was done. The 2 species, B. canis vogeli and H. canis, could be detected and differentiated in infected dog blood samples (n = 37) with high sensitivity (100%). The detection limit for B. canis vogeli was 15 copies of a positive control plasmid, and for H. canis, it was 150 copies of a positive control plasmid. The assay could simultaneously distinguish the DNA of both parasites from the DNA of controls. Blood samples from 5 noninfected dogs were negative, indicating high specificity. Several samples can be run at the same time. The assay can reduce misdiagnosis and the time associated with microscopic examination, and is not prone to the carryover contamination associated with the agarose gel electrophoresis step of conventional PCR. In addition, this qFRET PCR method would be useful to accurately determine the range of endemic areas or to discover those areas where the 2 parasites co-circulate.