Evaluation on Infectivity of Babesia microti to Domestic Animals and Ticks Outside the Ixodes Genus

An investigation of Haemaphysalis longicornis (Ixodida:Ixodidae) habitat and pathogen overlap with resident tick species in Southeastern Pennsylvania forests

The long-horned tick, Haemaphysalis longicornis Neumann (Ixodida: Ixodidae) was recently introduced to the United States from its native range in Asia. Although H. longicornis transmits numerous disease-causing pathogens in its native range, it is unclear to what extent H. longicornis will act as a disease vector in the United States. The ability of H. longicornis to acquire pathogens likely depends on overlap with resident tick species in both habitat and pathogens transmitted within its introduced range. To assess the potential overlap in habitat and pathogens between invasive H. longicornis and resident tick species, we field-collected ticks across southeastern Pennsylvania and tested them for pathogens. We then contextualized the risk of pathogen transmission to and by H. longicornis at sites where it overlaps with the current vector species using a network of vectored pathogens. None of the collected H. longicornis individuals tested positive for any pathogens. However, we found significant overlap in habitat use among H. longicornis and resident tick nymphs, as well as several overlaps in the pathogens vectored by resident ticks and those carried by H. longicornis in Asia. These findings indicate a high but yet-to-be-realized potential for H. longicornis to acquire North American tick-borne pathogens.

Tick HRF-dependent ferroptosis pathway to promote tick acquisition of Babesia microti

B. microti is a tick-transmitted zoonotic erythrocytic intracellular parasite. Ferroptosis is an iron-dependent form of programmed cell death that affects pathogen replication in the host. Currently, there is limited research concerning the effect of tick ferroptosis on Babesia infection and the underlying mechanism of action. The present study used a B. microti -mouse- Haemaphysalis longicornis infection model in which nymphs fed on the blood of B. microti-infected mice. The midgut divalent iron (p<0.01) and reactive oxygen species (ROS) (p<0.05) levels were significantly elevated in infected ticks, and transmission electron microscopy (TEM) showed that mitochondrial ridges were absent or decreased in size. Downregulation of ferritin 1 and glutathione peroxidase 4 (GPX4) in ticks infected with B. microti suggests that these changes promote ferroptosis. In vivo studies demonstrated that the ferroptosis promoter Erastin increased B. microti load (p<0.05), while the inhibitor Ferrostatin-1 effectively decreased load (p<0.01). Tick histamine-releasing factor (HRF), a protein related to the antioxidant system, was downregulated in infected nymphs compared with uninfected nymphs (p<0.05), and interference with HRF promoted tick acquisition of B. microti (p<0.001). Transcriptomic analyses showed that HRF interference promotes tick ferroptosis by downregulating ferritin 1 and GPX4. Meanwhile, interference with tick HRF molecules showed increased divalent iron and ROS and decreased mitochondrial ridges compared with controls. These findings highlight the critical role of tick HRF molecules in regulating ferroptosis and acquisition of B. microti, thereby providing important insights for a deeper understanding of the tick-Babesia interaction.

Molecular prevalence, epidemiology, and phylogenetic analysis of Babesia microti in dogs with a note on its impact on host hematological profile

Babesia (B.) microti is an intra-erythrocytic protozoan parasite that infects humans as well as domestic and wild animals. Prevalence of B. microti was investigated in 654 apparently healthy dogs belonging to 55 different breeds from three districts in Punjab province (Muzaffargarh, Bahawalpur and Jhang) and two districts in Khyber Pakhtunkhwa province (Dir Upper and Charsadda) in Pakistan. The hematological profile of dogs, risk factors associated with the infection and phylogenetic diversity of the detected isolates were also evaluated. In total, 29 blood samples (4 %) scored PCR positive. Sanger sequencing of partial 18S rRNA gene confirmed the presence of B. microti. The phylogenetic analysis of the sequences based on the 18S rRNA gene displayed global phylogenetic similarity with the isolates that were previously documented from Russia, France, Poland, Spain, China, Japan and USA. The infection rate was consistent across different sampling sites and dog breeds. Sex or presence of ectoparasites on dog was also not associated with B. microti prevalence. Babesia microti infected dogs had elevated red cell distribution width-coefficient of variation (%) than uninfected animals. This study presents updated data about the prevalence of B. microti among local Pakistani dogs and will be helpful in designing control strategies against this tick-borne pathogen as the tick infesting a B. microti infected dog may transmit this parasites to human as well.

Do Babesia microti Hosts Share a Blood Group System Gene Ortholog, Which Could Generate an Erythrocyte Antigen That Is Essential for Parasite Invasion?

The United States of America (US) has the highest annual number of human babesiosis cases caused by Babesia microti (Bm). Babesia, like malaria-causing Plasmodium, are protozoan parasites that live within red blood cells (RBCs). Both infectious diseases can be associated with hemolysis and organ damage, which can be fatal. Since babesiosis was made a nationally notifiable condition by the Centers for Disease Control and Prevention (CDC) in January 2011, human cases have increased, and drug-resistant strains have been identified. Both the Bm ligand(s) and RBC receptor(s) needed for invasion are unknown, partly because of the difficulty of developing a continuous in vitro culture system. Invasion pathways are relevant for therapies (e.g., RBC exchange) and vaccines. We hypothesize that there is at least one RBC surface antigen that is essential for Bm invasion and that all Bm hosts express this. Because most RBC surface antigens that impact Plasmodium invasion are in human blood group (hBG) systems, which are generated by 51 genes, they were the focus of this study. More than 600 animals with at least one hBG system gene ortholog were identified using the National Center for Biotechnology Information (NCBI) command-line tools. Google Scholar searches were performed to determine which of these animals are susceptible to Bm infection. The literature review revealed 28 Bm non-human hosts (NHH). For 5/51 (9.8%) hBG system genes (e.g., RhD), no NHH had orthologs. This means that RhD is unlikely to be an essential receptor for invasion. For 24/51 (47.1%) hBG system genes, NHH had 4-27 orthologs. For the ABO gene, 15/28 NHH had an ortholog, meaning that this gene is also unlikely to generate an RBC antigen, which is essential for Bm invasion. Our prior research showed that persons with blood type A, B, AB, O, RhD+, and RhD- can all be infected with Bm, supporting our current study's predictions. For 22/51 (43.1%) hBG system genes, orthologs were found in all 28 NHH. Nineteen (37.3%) of these genes encode RBC surface proteins, meaning they are good candidates for generating a receptor needed for Bm invasion. In vitro cultures of Bm, experimental Bm infection of transgenic mice (e.g., a CD44 KO strain), and analyses of Bm patients can reveal further clues as to which RBC antigens may be essential for invasion.

Repellent effects of Chinese cinnamon oil on nymphal ticks of Haemaphysalis longicornis, Rhipicephalus haemaphysaloides, and Hyalomma asiaticum

The repellent activity of Chinese cinnamon oil (Cinnamomum cassia) on nymphal ticks (Haemaphysalis longicornis Neumann, Rhipicephalus haemaphysaloides Supino, and Hyalomma asiaticum Schulze and Schlottke) was evaluated in a sample Y-tube bioassay. The results were based on the vertical migration of ticks during the host-seek phase and showed a dose-dependent repellent effect of Chinese cinnamon oil on the tested nymphs after 6 h. For H. longicornis, R. haemaphysaloides, and H. asiaticum at the concentrations (vol/vol) of 3, 3, and 1.5%, the repellent percentages over time were 68-97, 69-94, and 69-93%, respectively, which indicated strong repellent activities against ticks, similar to the positive control DEET (N,N-diethyl-3-methylbenzamide). Chinese cinnamon oil exerted the strongest effect on H. asiaticum nymphs. To our knowledge, this is the first study to investigate the repellent effects of Chinese cinnamon oil on ticks. Chinese cinnamon oil has considerable potential and should be developed as a practical tick repellent.

Multiple piroplasm parasites (Apicomplexa: Piroplasmida) in northeastern populations of the invasive Asian longhorned tick, Haemaphysalis longicornis Neumann (Ixodida: Ixodidae), in the United States

Piroplasms, which include the agents of cattle fever and human and dog babesiosis, are a diverse group of blood parasites of significant veterinary and medical importance. The invasive Asian longhorned tick, Haemaphysalis longicornis, is a known vector of piroplasms in its native range in East Asia and invasive range in Australasia. In the USA, H. longicornis has been associated with Theileria orientalis Ikeda outbreaks that caused cattle mortality. To survey invasive populations of H. longicornis for a broad range of piroplasms, 667 questing H. longicornis collected in 2021 from 3 sites in New Jersey, USA, were tested with generalist piroplasm primers targeting the 18S small subunit rRNA (395–515 bp, depending on species) and the cytochrome b oxidase loci (1009 bp). Sequences matching Theileria cervi type F (1 adult, 5 nymphs), an unidentified Theileria species (in 1 nymph), an undescribed Babesia sensu stricto (‘true’ Babesia, 2 adults, 2 nymphs), a Babesia sp. Coco (also a ‘true Babesia’, 1 adult, 1 nymph), as well as Babesia microti S837 (1 adult, 4 nymphs) were recovered. Babesia microti S837 is closely related to the human pathogen B. microti US-type. Additionally, a 132 bp sequence matching the cytochrome b locus of deer, Odocoileus virginanus, was obtained from 2 partially engorged H. longicornis. The diverse assemblage of piroplasms now associated with H. longicornis in the USA spans 3 clades in the piroplasm phylogeny and raises concerns of transmission amplification of veterinary pathogens as well as spillover of pathogens from wildlife to humans.

EVIDENCE OF PROTOZOAN AND BACTERIAL INFECTION AND CO-INFECTION AND PARTIAL BLOOD FEEDING IN THE INVASIVE TICK HAEMAPHYSALIS LONGICORNIS IN PENNSYLVANIA

The Asian longhorned tick, Haemaphysalis longicornis, an invasive tick species in the United States, has been found actively host-seeking while infected with several human pathogens. Recent work has recovered large numbers of partially engorged, host-seeking H. longicornis, which together with infection findings raises the question of whether such ticks can reattach to a host and transmit pathogens while taking additional bloodmeals. Here we conducted molecular blood meal analysis in tandem with pathogen screening of partially engorged, host-seeking H. longicornis to identify feeding sources and more inclusively characterize acarological risk. Active, statewide surveillance in Pennsylvania from 2020 to 2021 resulted in the recovery of 22/1,425 (1.5%) partially engorged, host-seeking nymphal and 5/163 (3.1%) female H. longicornis. Pathogen testing of engorged nymphs detected 2 specimens positive for Borrelia burgdorferi sensu lato, 2 for Babesia microti, and 1 co-infected with Bo. burgdorferi s.l. and Ba. microti. No female specimens tested positive for pathogens. Conventional PCR blood meal analysis of H. longicornis nymphs detected avian and mammalian hosts in 3 and 18 specimens, respectively. Mammalian blood was detected in all H. longicornis female specimens. Only 2 H. longicornis nymphs produced viable sequencing results and were determined to have fed on black-crowned night heron, Nycticorax nycticorax. These data are the first to molecularly confirm H. longicornis partial blood meals from vertebrate hosts and Ba. microti infection and co-infection with Bo. burgdorferi s.l. in host-seeking specimens in the United States, and the data help characterize important determinants indirectly affecting vectorial capacity. Repeated blood meals within a life stage by pathogen-infected ticks suggest that an understanding of the vector potential of invasive H. longicornis populations may be incomplete without data on their natural host-seeking behaviors and blood-feeding patterns in nature.

Proteomic analysis of extracellular vesicles from tick hemolymph and uptake of extracellular vesicles by salivary glands and ovary cells

BACKGROUND

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures that are important mediators of intercellular communication. Arthropods transport nutrients, signaling molecules, waste and immune factors to all areas of the body via the hemolymph. Little is known about tick hemolymph EVs.

METHODS

Hemolymph was collected from partially fed Rhipicephalus haemaphysaloides and Hyalomma asiaticum ticks by making an incision with a sterile scalpel in the middle (between the femur and metatarsus) of the first pair of legs, which is known as leg amputation. EVs were isolated from hemolymph by differential centrifugation and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Proteins extracted from the hemolymph EVs were analyzed by 4D label-free proteomics. The EVs were also examined by western blot and immuno-electron microscopy analysis. Intracellular incorporation of PHK26-labeled EVs was tested by adding labeled EVs to tick salivary glands and ovaries, followed by fluorescence microscopy.

RESULTS

In this study, 149 and 273 proteins were identified by 4D label-free proteomics in R. haemaphysaloides and H. asiaticum hemolymph EVs, respectively. TEM and NTA revealed that the sizes of the hemolymph EVs from R. haemaphysaloides and H. asiaticum were 133 and 138 nm, respectively. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses of identified proteins revealed pathways related to binding, catalytic and transporter activity, translation, transport and catabolism, signal transduction and cellular community. The key EV marker proteins RhCD9, RhTSG101, Rh14-3-3 and RhGAPDH were identified using proteomics and western blot. The presence of RhFerritin-2 in tick hemolymph EVs was confirmed by western blot and immuno-electron microscopy. We demonstrated that PKH26-labeled hemolymph EVs are internalized by tick salivary glands and ovary cells in vitro.

CONCLUSIONS

The results suggest that tick EVs are secreted into, and circulated by, the hemolymph. EVs may play roles in the regulation of tick development, metabolism and reproduction.

In Silico Survey and Characterization of Babesia microti Functional and Non-Functional Proteases

Human babesiosis caused by the intraerythrocytic apicomplexan Babesia microti is an expanding tick-borne zoonotic disease that may cause severe symptoms and death in elderly or immunocompromised individuals. In light of an increasing resistance of B. microti to drugs, there is a lack of therapeutic alternatives. Species-specific proteases are essential for parasite survival and possible chemotherapeutic targets. However, the repertoire of proteases in B. microti remains poorly investigated. Herein, we employed several combined bioinformatics tools and strategies to organize and identify genes encoding for the full repertoire of proteases in the B. microti genome. We identified 64 active proteases and 25 nonactive protease homologs. These proteases can be classified into cysteine (n = 28), serine (n = 21), threonine (n = 14), asparagine (n = 7), and metallopeptidases (n = 19), which, in turn, are assigned to a total of 38 peptidase families. Comparative studies between the repertoire of B. bovis and B. microti proteases revealed differences among sensu stricto and sensu lato Babesia parasites that reflect their distinct evolutionary history. Overall, this data may help direct future research towards our understanding of the biology and pathogenicity of Babesia parasites and to explore proteases as targets for developing novel therapeutic interventions.

Experimental Infection of Ticks: An Essential Tool for the Analysis of Babesia Species Biology and Transmission

Babesiosis is one of the most important tick-borne diseases in veterinary health, impacting mainly cattle, equidae, and canidae, and limiting the development of livestock industries worldwide. In humans, babesiosis is considered to be an emerging disease mostly due to Babesia divergens in Europe and Babesia microti in America. Despite this importance, our knowledge of Babesia sp. transmission by ticks is incomplete. The complexity of vectorial systems involving the vector, vertebrate host, and pathogen, as well as the complex feeding biology of ticks, may be part of the reason for the existing gaps in our knowledge. Indeed, this complexity renders the implementation of experimental systems that are as close as possible to natural conditions and allowing the study of tick-host-parasite interactions, quite difficult. However, it is unlikely that the development of more effective and sustainable control measures against babesiosis will emerge unless significant progress can be made in understanding this tripartite relationship. The various methods used to date to achieve tick transmission of Babesia spp. of medical and veterinary importance under experimental conditions are reviewed and discussed here.

The Tick Microbiota Dysbiosis Promote Tick-Borne Pathogen Transstadial Transmission in a Babesia microti-Infected Mouse Model

Ticks are obligate hematophagous ectoparasites. They are important vectors for many pathogens, of both medical and veterinary importance. Antibiotic residues in animal food are known, but very little is known about the effects of antibiotic residues in animals on the microbiome diversity of ticks and tick-borne pathogen transmission. We used a Haemaphysalis longicornis–infested mouse model to evaluate the effect of antibiotic usage on tick microbiome. Nymphal ticks were fed on an antibiotic cocktail-treated or water control mice. Adult ticks molted from nymphs fed on the antibiotic cocktail-treated mouse had a dysbiosed microbiota. Nymphal ticks were also fed on a B. microti–infected mice that had been treated with antibiotic cocktail or water. We found that the B. microti infection in adult ticks with a dysbiosed microbiota (44.7%) was increased compared with the control adult ticks (24.2%) by using qPCR targeting 18S rRNA gene. This may increase the risk of tick-borne pathogens (TBPs) transmission from adult ticks to a vertebrate host. These results show that an antibiotic-treated mouse can induce tick microbiota dysbiosis. Antibiotic treatment of B. microti-infected mouse poses the possibility of increasing transstadial transmission of B. microti from the nymph to the adult H. longicornis. These findings suggest that B. microti transmission may be exacerbated in high antibiotic usage areas.

Animal reservoirs of zoonotic Babesia species: A global systematic review and meta-analysis of their prevalence, distribution and species diversity

Zoonotic babesiosis caused by Babesia divergens, B. microti and B. venatorum is a vector-borne protozoan zoonosis of increasing public health importance worldwide. A complex system of animal reservoirs including a wide range of mammals and a limited number of birds play a central role in maintaining the infection. Governed by the PRISMA guidelines, we conducted a systematic review and meta-analysis to determine the global prevalence, distribution and the diversity of zoonotic Babesia species in animal reservoirs. We pooled data using the random-effects model and determined quality of individual studies, heterogeneity and across study bias using the Joanna Briggs Institute critical appraisal instrument for prevalence studies, Cochran's Q-test and Egger's regression test respectively. Seventy nine studies from 29 countries reported a total 9311 positive cases of zoonotic Babesia infections from 46,649 animal reservoirs, yielding an overall estimated prevalence of 12.45% (95% CI: 10.09-15.27). Continental prevalence ranged between 8.55 (95% CI: 1.90-31.11) in Africa and 27.81% (95% CI: 21.25-35.48) in North America. Estimated prevalence in relation to country income levels, methods of diagnosis, study periods, sample sizes and reservoir categories ranged between 4.97 (95% CI: 1.80-13.00) and 30.12% (95% CI: 22.49-39.04). B. divergens was the most prevalent (12.50%, 95% CI: 8.30-18.39) of the 3 species of zoonotic Babesia reported in animal reservoirs. Zoonotic Babesia infections are prevalent in animal reservoirs across the world with the highest prevalence in North America and domestic animals. B. microti had the widest geographic distribution. We recommend tick control as well as strategic and prophylactic treatment against these parasites in animal reservoirs to curtail the economic losses associated with zoonotic Babesia species and possible transmission to humans.

Distribution and Density of Haemaphysalis longicornis (Acari: Ixodidae) on Public Lands in Pennsylvania, United States

Since the recent introduction of the Asian longhorned tick (Haemaphysalis longicornis Neumann) in the United States, quantitative surveillance information remains lacking, which hinders accurate estimates of population structure and entomological risk. We conducted statewide, active tick surveillance from May to August 2019 and report data on H. longicornis geographical distribution and population density in Pennsylvania. In total, 615 H. longicornis were collected from four counties. Across samples recovering H. longicornis, mean density of H. longicornis was 9.2/100 m2, comparably greater than Ixodes scapularis Say (8.5/100 m2). Density of H. longicornis was also significantly greater in August, largely driven by larvae, and greater in recreational habitat types (12.6/100 m2) and in Bucks County (11.7/100 m2), situated adjacent to the location of the first U.S. discovery of intense infestations. These data are among the first to document H. longicornis from statewide tick surveillance and provide initial measures of population density enabling more quantitative characterizations of distributional patterns.

Proteomic Analysis of Exosome-Like Vesicles Isolated From Saliva of the Tick Haemaphysalis longicornis

Extracellular vesicles (EVs), are considered as vehicles of cellular communication. Parasites usually release EVs in their excretory-secretory products to modulate host environment. However, little is known about the secretion of EVs by ticks. In this study, we show for the first time that the tick Haemaphysalis longicornis secretes EVs in saliva that resembles exosomes. EVs were purified from pilocarpine induced saliva of partially engorged H. longicornis ticks. Electron microscopy analysis revealed the presence of exosome-like vesicles with a size of 100 nm. Proteomic analysis by LC-MS/MS identified a total of 356 proteins in tick-derived EVs. Proteome data of tick-derived EVs was validated by Western blot analysis. Immunodetection of Hsp70 and GAPDH proteins indicated that the proteomics data of tick-derived EVs were highly reliable. Bioinformatics analysis (Gene Ontology) indicated association of certain biological and molecular functions with proteins which may be helpful during tick development. Likewise, KEGG database revealed involvement of vesicular proteins in proton transport, detoxification, ECM-receptor interaction, ribosome, RNA transport, ABC transporters, and oxidative phosphorylation. The results of this study provide evidence that EVs are being secreted in tick saliva and suggest that tick saliva-derived EVs could play important roles in host-parasite relationships. Moreover, EVs could be a useful tool in development of vaccines or therapeutics against ticks.

Porin Expression Profiles in Haemaphysalis longicornis Infected With Babesia microti

The porin gene is widely disseminated in various organisms and has a pivotal role in the regulation of pathogen infection in blood-sucking arthropods. However, to date, information on the porin gene from the Haemaphysalis longicornis tick, an important vector of human and animal diseases, remains unknown. In this study, we identified the porin gene from H. longicornis and evaluated its expression levels in Babesia microti-infected and -uninfected H. longicornis ticks at developmental stages. We also analyzed porin functions in relation to both tick blood feeding and Babesia infection and the relationship between porin and porin-related apoptosis genes such as B-cell lymphoma (Bcl), cytochrome complex (Cytc), caspase 2 (Cas2), and caspase 8 (Cas8). The coding nucleotide sequence of H. longicornis porin cDNA was found to be 849 bp in length and encoded 282 amino acids. Domain analysis showed the protein to contain six determinants of voltage gating and two polypeptide binding sites. Porin mRNA levels were not significantly different between 1-day-laid and 7-day-laid eggs. In the nymphal stage, higher porin expression levels were found in unfed, 12-h-partially-fed (12 hPF), 1-day-partially-fed (1 dPF), 2 dPF nymphs and nymphs at 0 day post-engorgement (0 dAE) vs. nymphs at 2 dAE. Cytc and Cas2 mRNA levels were higher in 2 dPF nymphs in contrast to nymphs at 2 dAE. Porin expression levels appeared to be higher in the infected vs. uninfected nymphs during blood feeding except at 1 dPF and 0-1 dAE. Especially, the highest B. microti burden negatively affected porin mRNA levels in both nymphs and female adults. Porin knockdown affected body weight and Babesia infection levels and significantly downregulated the expression levels of Cytc and Bcl in H. longicornis female ticks. In addition, this study showed that infection levels of the B. microti Gray strain in nymphal and female H. longicornis peaked at or around engorgement from blood feeding to post engorgement. Taken together, the research conducted in this study suggests that H. longicornis porin might interfere with blood feeding and B. microti infection.

Detection of novel piroplasmid species and Babesia microti and Theileria orientalis genotypes in hard ticks from Tengchong County, Southwest China

To reveal the genetic diversity of Babesia microti and Theileria orientalis in Southwest China, we conducted a molecular survey of piroplasms in hard ticks in a China-Myanmar border county. Host infesting and questing ticks were collected from Tengchong County in 2013 and 2014. Piroplasm infection in ticks was detected by PCR, and then, phylogenetic analysis was conducted to study the genetic diversity of the pathogens identified in ticks. All in all, six piroplasm species comprising of B. microti; B. orientalis; a novel Babesia species designated Babesia sp. Tengchong, China; T. orientalis; T. luwenshuni; and an as yet undescribed piroplasmid species referred to as Piroplasmid sp. Tengchong, China, have been identified after screening goat- and cattle-attached ticks. In addition, B. bigemina has been identified by screening questing ticks. Phylogenetic analysis based on the 18S rRNA and partial β-tubulin gene revealed two novel potentially zoonotic genotypes designated B. microti Tengchong-Type A and B. The T. orientalis genotypes identified in the present study represent the seven known genotypes 1-5, 7, and N3 as revealed by phylogenetic analysis of 18S rRNA and MPSP genes. Importantly, an additional genotype designated N4 has also been identified in this study, which brings the number of recognized T. orientalis genotypes to a total of twelve. Thus, besides the two novel species, Babesia sp. Tengchong, China, closely related to Babesia species isolated from yak and Piroplasmid sp. Tengchong, China, our study demonstrates that additional novel B. microti and T. orientalis genotypes exist in Southwest China.

Establishment of Babesia vulpes n. sp. (Apicomplexa: Babesiidae), a piroplasmid species pathogenic for domestic dogs

BACKGROUND

Canine babesiosis is a severe disease caused by several Babesia spp. A number of names have been proposed for the canine-infecting piroplasmid pathogen initially named Theileria annae Zahler, Rinder, Schein & Gothe, 2000. It was shown to be a member of the Babesia (sensu lato) group infecting carnivores and is also closely related to the Babesia microti group. Subsequently, the same parasite species was reclassified as a member of the genus Babesia and the name Babesia vulpes Baneth, Florin-Christensen, Cardoso & Schnittger, 2015 was proposed for it. However, both names do not meet the requirements of the International Code of Zoological Nomenclature (no accompanying descriptions, no deposition of type-specimens) and cannot be recognized as available names from the nomenclatural point of view. The purpose of this study was to further characterize this parasite in order to confirm its validity, to provide its description and to introduce zoological nomenclature for it with the name Babesia vulpes n. sp.

RESULTS

Morphological description of the parasite in canine erythrocytes demonstrated that it takes the shape of small (1.33 × 0.98 µm), round to oval forms reminiscent of the pyriform and ring shapes of other small canine Babesia spp., such as Babesia gibsoni Patton, 1910 and Babesia conradae Kjemtrup, Wainwright, Miller, Penzhorn & Carreno, 2006. However, these parasite forms were overall smaller than those measured for the latter two species and no tetrad (Maltese cross) form was reported. Furthermore, phylogenetic analysis using the cytochrome c oxidase subunit 1 (COX1) amino acid sequences substantiates the species identity of this parasite as previously demonstrated based on phylogenetic analysis of the 18S rRNA and β-tubulin genes. The holotype of the parasite species was designated and deposited in an accessible public collection.

CONCLUSIONS

This study ratifies the name Babesia vulpes n. sp. proposed for the parasite previously referred to as Theileria annae Zahler, Rinder, Schein & Gothe, 2000, Babesia annae (Zahler, Rinder, Schein & Gothe, 2000) or Babesia vulpes Baneth, Florin-Christensen, Cardoso & Schnittger, 2015, or mentioned as "Babesia microti-like piroplasm", "Babesia Spanish dog isolate" and Babesia cf. microti.