Canine babesiosis

Molecular epidemiological survey of the Babesia gibsoni cytochrome b gene in western Japan

In this study, we conducted a survey of the cytochrome b (cytb) gene of Babesia gibsoni (B. gibsoni) isolated from clinical cases to determine the prevalence of potential atovaquone (ATV)-resistant variants. Ninety-two blood samples were collected from naturally B. gibsoni infected dogs. The cytb nucleotide sequence was determined by direct sequencing. Twelve non-synonymous amino acid substitutions were identified in cytb. The principal ATV-resistant substitution, M121I, was detected in three cases. This survey determined that potentially ATV-resistant B. gibsoni strains are present in dogs in Japan.

Canine vector-borne disease pathogens in dogs from south-east Queensland and north-east Northern Territory

OBJECTIVES

To determine the prevalence of canine vector-borne diseases (CVBD: Babesia spp., Anaplasma spp., Ehrlichia spp., haemotropic mycoplasmas and Hepatozoon) in Australian dogs; namely, dogs from pounds in south-east Queensland and an indigenous Aboriginal community in the north-east of the Northern Territory.

DESIGN AND PROCEDURE

Blood samples were collected from 100 pound dogs and 130 Aboriginal community dogs and screened for the CVBD pathogens using polymerase chain reaction (PCR). All positive PCR products were sequenced for species confirmation.

RESULTS

In total, 3 pound dogs and 64 Aboriginal community dogs were infected with at least one CVBD pathogen. Overall, B. vogeli was detected in 13 dogs, A. platys in 49, M. haemocanis in 23, Candidatus Mycoplasma haematoparvum in 3 and C. M. haemobos in 1 dog. Co-infections were detected in 22 Aboriginal community dogs.

CONCLUSIONS

This study found B. vogeli, A. platys and haemotropic mycoplasma infections to be common in dogs in subtropical and tropical areas of Australia. This study also reports for the first time the prevalence and genetic characterisation of haemotropic mycoplasmas in dogs in Australia.

First evidence and molecular characterization of Babesia vogeli in naturally infected dogs and Rhipicephalus sanguineus ticks in southern France

Babesiosis is an emerging tick-borne disease of animals and humans caused by intraerythrocytic protozoa of the genera Babesia and Theileria. In France canine babesiosis has a high prevalence with Babesia canis thought to be the main aetiological agent of the disease. Babesia vogeli has already been reported to occur in Europe and in other countries around the Mediterranean Sea. The tick Rhipicephalus sanguineus, the main known vector of B. vogeli, occurs in southern France. However, only one case of a B. vogeli infected dog has been reported to date in France. To gain further insight into the prevalence of Babesia and Theileria infections in dogs and ticks of the R. sanguineus complex, a study was conducted in a veterinary practice in the south of France from January to September 2010. Twelve bloods from dogs and 36 R. sanguineus ticks were analyzed using PCR and sequencing. For the analysis of ticks, a new primer was designed to specifically amplify the B. vogeli 18S rRNA gene. Four dogs (33.3%) and 8 ticks (22.2%) were found to be infected with B. vogeli. This approach has thus revealed for the first time a cluster of cases of canine babesiosis caused by B. vogeli in France and highlights the need to systematically screen for pathogens potentially responsible for canine babesiosis at the species level using suitable molecular tools.

Canine babesiosis in Romania due to Babesia canis and Babesia vogeli: a molecular approach

Canine babesiosis is a tick-borne disease caused by the protozoa Babesia spp. that affects dogs worldwide. In Romania, canine babesiosis has become quite frequent in the last few years, with a wide variety of clinical signs, ranging from mild, nonspecific illness to peracute collapse, and even death. Traditionally, a Babesia infection in dogs is diagnosed based on the morphologic appearance of the intraerythrocytic piroplasms observed in peripheral blood smears. To date, no data on genetic characterization of Babesia species in dogs has been documented for Romania. Therefore, a molecular survey on natural Babesia infections of dogs in Romania using polymerase chain reaction and genetic sequence analysis of a fragment of the ssRNA gene was performed. A total number of 16 blood samples were tested for the presence of Babesia DNA. Blood samples were collected from 11 dogs with symptoms of babesiosis and microscopically proven positive for Babesia and from a group of five asymptomatic dogs, not tested microscopically for Babesia, which were included in the study for comparative analysis. The piroplasm-specific PCR amplifying the partial 18S rRNA gene confirmed Babesia spp. infection in all 11 samples from dogs with clinical babesiosis, and in one of the clinically normal dogs. Sequence analysis revealed the presence of Babesia canis in all clinically affected dogs and Babesia vogeli in one clinically normal dog. This is the first molecular evidence of B. canis and B. vogeli in dogs from Romania. The results of the study provide basic information toward a better understanding of the epidemiology of canine babesiosis in Romania and will help to promote an effective control program.

Development of in vitro atovaquone-resistant Babesia gibsoni with a single-nucleotide polymorphism in cytb

An atovaquone (ATV)-resistant Babesia gibsoni was developed by in vitro exposure of uncloned wild type (WT) B. gibsoni to 800 nM ATV for 6 days. Sequence analysis of mitochondrial genes showed a single-nucleotide polymorphism (SNP) at cytb nt363 (G to T) that resulted in the substitution of methionine with isoleucine (M121I), which is one of the SNPs reported in a previous in vivo study. 363T or 363G allele-specific real-time polymerase chain reaction (PCR) revealed that an M121I variant was present in over 99% of the ATV-resistant population. As neither ATV resistance nor gene polymorphisms appeared in the B. gibsoni WT sibling clones, the expression of ATV resistance in this study was suspected to be because of selective multiplication of the B. gibsoni M121I variant. This ATV-resistant B. gibsoni displayed the same sensitivity as the WT B. gibsoni against 5 other drugs, including diminazene aceturate, azithromycin, doxycycline, clindamycin, and proguanil. This is the first report on the in vitro establishment of an ATV-resistant B. gibsoni with gene polymorphisms.

Expression of truncated Babesia gibsoni thrombospondin-related adhesive proteins in Escherichia coli and evaluation of their diagnostic potential by enzyme-linked immunosorbent assay

Among the previously established enzyme-linked immunosorbent assays (ELISAs), an ELISA using the full length of a recombinant thrombospondin-related adhesive protein of Babesia gibsoni (rBgTRAPf) is considered as the most sensitive diagnostic method for the detection of an antibody to B. gibsoni in dogs. However, the expression of rBgTRAPf in high concentration is poor and, thus, limits its usefulness as a diagnostic antigen. To improve its expression level, we have truncated BgTRAPf into two fragments having either an N- or a C-terminus (BgTRAPn or BgTRAPc, respectively). The expression of BgTRAPc protein in Escherichia coli yielded adequate recombinant protein. The specificity and sensitivity of ELISAs with the truncated proteins were determined using dog sera experimentally infected with B. gibsoni and specific pathogen-free (SPF) dog sera. A total of 254 field dog sera were examined by the ELISA with rBgTRAPn, rBgTRAPc, and rBgTRAPf as well as by an indirect fluorescent antibody test (IFAT). The specificity of rBgTRAPc was the highest (97.15%), and its kappa value was more (0.8003) than rBgTRAPn (0.7083). With a sufficient level of expression as well as higher specificity and reliable sensitivity, rBgTRAPc appears to be a potential candidate antigen for the serodiagnosis of B. gibsoni infection in dogs.

Polymerase chain reaction confirmation of Babesia canis canis and Anaplasma phagocytophilum in dogs suspected of babesiosis in Slovakia

Canine babesiosis was considered an imported tick transmitted disease until the first case of autochthonous canine babesiosis in Slovakia was described in 2002. Since then, the number of cases kept increasing every year. The causative agent of babesiosis in dogs is not yet characterized; therefore, the aim of our study was to determine the agent and the rate of infection in the vector tick D. reticulatus in Slovakia. Babesia canis canis was detected in 80 out of 87 blood samples from dogs with clinical manifestations of babesiosis. Six dogs suspected of babesiosis tested positive for presence of Anaplasma phagocytophilum, and one mixed infection of B. c. canis and A. phagocytophilum was detected. B. c. canis was detected in 35.6% questing adults of D. reticulatus. The obtained sequences from blood samples showed 99.7% and from D. reticulatus, 99.4% similarity with the B. c. canis (AY072926) from dogs infected in Croatia. In our study, we characterized the agent of canine babesiosis from blood samples of naturally infected dogs and D. reticulatus, the vector tick. Further, the presence of A. phagocytophilum, bacterium responsible for the canine granulocytic anaplasmosis, was recorded in dogs for the first time in Slovakia.

Canine vector-borne disease in travelled dogs in Germany--a retrospective evaluation of laboratory data from the years 2004-2008

When importing dogs from various Mediterranean countries into Western Europe canine vector-borne infections are often considered as a major issue. Several diseases including babesiosis, leishmaniosis, hepatozoonosis, canine heartworm disease or ehrlichiosis can potentially be endemic in this region and pose a potential health risk for travelling dogs. Information on such infections in travelled dogs is scarce and therefore this study has been undertaken to examine the frequency of vector-borne infections in travelled dogs from the years 2004-2008. A total of 997 samples were screened by direct and/or indirect methods. Total seroprevalence was 7.5% with individual seroprevalence for the 3 species Leishmania spp., Ehrlichia canis and Babesia canis spp. ranging from 3.1 to 4.9%. Total detection rate for pathogens by direct methods was 3.5%. Nineteen Giemsa-stained blood smears were positive for large Babesia. None of the samples screened for microfilariae by Knott's test or for Dirofilaria immitis antigen by DiroChek(®) were positive. Using PCR methods Leishmania-DNA was detected in 1/42 samples but none of 59 animals screened for E. canis-DNA was positive. The prevalence values as established by indirect and direct pathogen detection are considered as rather low.

Babesiosis in dogs and cats--expanding parasitological and clinical spectra

Canine babesiosis caused by different Babesia species is a protozoal tick-borne disease with worldwide distribution and global significance. Historically, Babesia infection in dogs was identified based on the morphologic appearance of the parasite in the erythrocyte. All large forms of Babesia were designated Babesia canis, whereas all small forms of Babesia were considered to be Babesia gibsoni. However, the development of molecular methods has demonstrated that other Babesia species such as Babesia conradae, Babesia microti like piroplasm, Theileria spp. and a yet unnamed large form Babesia spp. infect dogs and cause distinct diseases. Babesia rossi, B. canis and Babesia vogeli previously considered as subspecies are identical morphologically but differ in the severity of clinical manifestations which they induce, their tick vectors, genetic characteristics, and geographic distributions, and are therefore currently considered separate species. The geographic distribution of the causative agent and thus the occurrence of babesiosis are largely dependent on the habitat of relevant tick vector species, with the exception of B. gibsoni where evidence for dog to dog transmission indicates that infection can be transmitted among fighting dog breeds independently of the limitations of vector tick infestation. Knowledge of the prevalence and clinicopathological aspects of Babesia species infecting dogs around the world is of epidemiologic and medical interest. Babesiosis in domestic cats is less common and has mostly been reported from South Africa where infection is mainly due to Babesia felis, a small Babesia that causes anemia and icterus. In addition, Babesia cati was reported from India and sporadic cases of B. canis infection in domestic cats have been reported in Europe, B. canis presentii in Israel and B. vogeli in Thailand. Babesiosis caused by large Babesia spp. is commonly treated with imidocarb dipropionate with good clinical response while small Babesia spp. are more resistant to anti-babesial therapy. Clinical and parasitological cure are often not achieved in the treatment of small Babesia species infections and clinical relapses are frequent. The spectrum of Babesia pathogens that infect dogs and cats is gradually being elucidated with the aid of molecular techniques and meticulous clinical investigation. Accurate detection and species recognition are important for the selection of the correct therapy and prediction of the course of disease.

Babesiosis due to the canine Babesia microti-like small piroplasm in dogs-first report from Portugal and possible vertical transmission

Background

Canine babesiosis (or piroplasmosis) is endemic in northern Portugal, but molecularly confirmed cases of infection with small piroplasms have not been reported in the country. Three German shepherd dogs - a bitch and its 2-month old pup and an unrelated male - clinically suspected of piroplasmosis were assessed for babesial infection.

Results

Parasitemia with small piroplasms was detected by microscopy in two dogs. All three dogs were positive by PCR and the Babesia microti-like small piroplasm (syn. Theileria annae) was identified by DNA sequencing. These are the first confirmed cases of babesiosis caused by the B. microti-like piroplasm both in dogs from Portugal and in dogs suspected of clinical piroplasmosis outside of Spain.

Conclusions

Although the bitch and the male had visited neighboring Galicia (northwestern Spain), where the disease is endemic, incursion of this piroplasm into northern Portugal is evident and infection of the non-traveled pup was due to either vertical transmission or autochthonous tick infection.

Clinical management of canine babesiosis

OBJECTIVE

To review and summarize current information regarding epidemiology, pathogenesis, and pathophysiology leading to the various clinical syndromes associated with canine babesiosis. Diagnosis, treatment, preventative strategies, and zoonotic implications are discussed.

ETIOLOGY

Babesiosis is caused by hemoprotozoa of the genus Babesia. Numerous species of Babesia exist worldwide. An increased incidence of babesiosis is described, especially in North America. The babesial organism spends the majority of its life cycle within the erythrocyte of the definitive host, resulting in hemolysis, with or without systemic complications.

DIAGNOSIS

Definitive diagnosis depends on direct visualization of the organism on blood smear or polymerase chain reaction. A positive serologic antibody test indicates exposure with or without active infection.

THERAPY

Antiprotozoal drugs, antimicrobials, and supportive care are the mainstays of babesiosis therapy.

PROGNOSIS

Prognosis depends on the severity of disease, which in turn depends on both organism and host factors. Clinical syndromes associated with a poorer prognosis include red biliary syndrome, acute renal failure, acute respiratory distress syndrome, neurologic dysfunction, acute pancreatitis, cardiac dysfunction, and hypoglycemia.

Sequence and phylogenetic analysis of the thrombospondin-related adhesive protein (TRAP) gene of Babesia gibsoni isolates from dogs in Taiwan

The genetic diversity of Babesia gibsoni strains worldwide is currently poorly defined. The aim of the present study was to characterize B. gibsoni strains in naturally infected dogs in Taiwan using a combination of polymerase chain reaction (PCR) and sequence analysis of both 18S rDNA and the gene encoding thrombospondin-related adhesive protein (TRAP). Genomic DNA was extracted from 29 parasitemic dogs, and the target genes were separately amplified, sequenced and aligned with corresponding sequences available in GenBank. All 18S rDNA sequences (1,262 bp) amplified from the Taiwanese isolates were identical to each other and had very high similarity (99.9-100%) with previously reported B. gibsoni sequences. These results provide the first molecular evidence showing infection of dogs with B. gibsoni from Taiwan. On the other hand, a phylogenetic analysis based on the deduced amino acid sequence of the TRAP gene demonstrated that the Taiwanese isolates were closely related to strains previously identified from Okinawa Island, Japan, but genetically distinct from strains found on Honshu in Japan and Jeju Island in South Korea. The divergence of TRAP among the geographically dispersed strains examined in this study and others supports the conclusion that this gene is useful for molecular genotyping of B. gibsoni strains.

Canine babesiosis in northern Portugal and molecular characterization of vector-borne co-infections

Background

Protozoa and bacteria transmitted by arthropods, including ticks and phlebotomine sand flies, may cause a wide range of canine vector-borne diseases. Dogs can be simultaneously or sequentially infected with multiple pathogens. Canine babesiosis caused by Babesia canis canis and Babesia canis vogeli is known to occur in Portugal. This study assessed, by means of blood smear examination, PCR and DNA nucleotide sequencing, the presence of Babesia spp. and co-infecting agents Leishmania, Anaplasma/Ehrlichia and Hepatozoon in 45 dogs from northern Portugal clinically suspected of babesiosis.

Results

Forty-four dogs (98%) had infection with B. canis canis and one with B. canis vogeli. Co-infections were detected in nine animals (20%). Eight dogs were found infected with two vector-borne agents: six with B. canis canis and Leishmania infantum; one with B. canis canis and Ehrlichia canis; and one with B. canis canis and Hepatozoon canis. Another dog was infected with three vector-borne pathogens: B. canis vogeli, E. canis and L. infantum. Overall, L. infantum was found in seven (16%), E. canis in two (4%), and H. canis in one (2%) out of the 45 dogs with babesiosis. Almost 90% of the 45 cases of canine babesiosis were diagnosed in the colder months of October (18%), November (27%), December (20%), February (13%) and March (9%). Co-infections were detected in February, March, April, May, October and November. Twenty-two (50%) out of 44 dogs infected with B. canis were found infested by ticks including Dermacentor spp., Ixodes spp. and Rhipicephalus sanguineus. Mortality (9%) included two co-infected dogs that died spontaneously and two with single infections that were euthanized.

Conclusions

Babesia canis canis is the main etiological agent of canine babesiosis in northern Portugal. A higher sensitivity of Babesia spp. detection was obtained with PCR assays, compared to the observation of blood smears. Twenty percent of the dogs were co-infected with L. infantum, E. canis or H. canis. Furthermore, this is the first molecular identification of H. canis in dogs from northern Portugal.

Evidence of new pathogenic Theileria species in dogs

Babesiosis, caused by tick-borne haematozoan organisms of the genus Babesia, is a parasitic disease of domestic and wild mammals. Canine Babesidae have historically been classified as "large Babesia" (Babesia canis) and "small Babesia" (Babesia gibsoni) based on the size of their intraerythrocytic forms. Recent publications, however, suggest that the diversity of piroplasm species infecting dogs might be greater than previously appreciated. Sequencing and phylogenetic analysis of the ssrRNA gene has revealed that canine piroplasms are found in three clades, 'true' Babesia sp. (B. canis and B. gibsoni), Theileria annae and Theileria-like group (B. conradae). This newly recognised piroplasm T. annae appears to be hyperendemic in northwest Spain. The vector for this emergent canine infection remains undescribed, although the Ixodeshexagonus is suspected based on their presence upon the dogs in NW Spain and the relative absence of others. These observations have introduced a major change in the approach to the epidemiology of babesiosis in dogs. More clinical samples and data will need to be collected and analyzed to understand the importance of Theileria species in dogs.

Frequency and therapy monitoring of canine Babesia spp. infection by high-resolution melting curve quantitative FRET-PCR

Babesia gibsoni and Babesia canis are the etiological agents of canine babesiosis, a protozoal hemolytic disease with global significance. Canine babesiosis has been diagnosed by microscopic identification of intra-erythrocytic trophozoites in blood smear, and by serological testing. Here we developed a quantitative fluorescence resonance energy transfer (FRET)-PCR that amplifies a fragment of the Babesia spp. 18S rRNA gene with high sensitivity and specificity. Melting curve analysis differentiates B. gibsoni, B. canis canis/B. canis vogeli, and B. canis rossi by the disassociation temperature of the fluorescent probes. Babesia gibsoni infection was detected in 8 of 48 canine breeds (17%) and 24 of a total of 235 specimens (10.2%) submitted from 22 states of the continental United States of America. A potential blood donor was positive for B. canis vogeli infection. In Hong Kong (China), B. gibsoni infection was detected in 30 of 64 specimens (46.9%) from 15 of the 24 breeds (63%). While the frequency of canine babesiosis did not associate with seasonal change in Hong Kong, positivity in the USA for Babesia spp. infection was higher in Spring and Summer than in Autumn and Winter. The data suggest that environmental factors associated with tick vector exposure rather than genetic susceptibility determine the incidence of canine babesiosis. Babesia spp. burdens in blood declined significantly with increasing age of the infected dogs, and therapy with atovaquone and tilmicosin eliminated B. gibsoni while doxcycline and berenil did not. This demonstrates that high-resolution real-time PCR analysis may advance diagnosis and therapy monitoring of canine babesiosis.

Immunogenicity and growth inhibitory efficacy of the prime-boost immunization regime with DNA followed by recombinant vaccinia virus carrying the P29 gene of Babesia gibsoni in dogs

In recent studies, heterologous prime-boost approaches, employing plasmid DNA and viral vector pathogen-delivering sequences, have been considered an effective protection strategy for intracellular parasite infections. Here, we evaluated the efficacy of such a strategy against the canine Babesia gibsoni infection. The DNA (pCAGGS-P29) and recombinant vaccinia virus (vvP29) both encoding the P29 of B. gibsoni were used in this study. The dogs were immunized 3 times with priming DNA and boosted once with recombinant virus. The dogs immunized with P29 developed a significant level of IgG2 antibody against P29. The response was strongly boosted by the inoculation of vvP29. The peripheral IFN-gamma responses of the dogs immunized with P29 were significantly higher than those of controls after the parasite inoculation. Moreover, the P29 immunized group showed a significantly low level of parasitemia. In conclusion, this study supports the efficacy of a prime-boost strategy for dogs against canine B. gibsoni infection.

Molecular characterizations of three distinctBabesia gibsonirhoptry-associated protein-1s (RAP-1s)

Three cDNAs encoding rhoptry-associated protein 1 (RAP-1) homologues were found in theBabesia gibsoniEST database. Based on similarities to BgRAP-1a, which was identified previously by serological screening of a cDNA merozoite library, the two new genes were designatedBgRAP-1b(33·7%) andBgRAP-1c(57%). Mice antiserum raised against each recombinant protein reacted specifically withB. gibsoniparasites as determined by Western blotting, which showed native molecular sizes of the BgRAP-1a (51 kDa), BgRAP-1b (53 kDa) and BgRAP-1c (47 kDa) consistent with predictable molecular weights. Immunofluoresence using these antibodies revealed localization of all BgRAP-1s within the matrix of merozoites; however, BgRAP-1a appeared to diverge from the other two when it was found secreted into the cytoplasm of infected erythrocytes. Apical localization of all 3 BgRAP-1s during the extracellular stage of the parasite combined with their ability to bind a canine erythrocyte membrane fraction was suggestive of a role for these proteins in erythrocyte attachment. Lastly, the ability of these recombinant proteins to be used as diagnostic reagents was tested by ELISA and the sensitivities of BgRAP-1a and BgRAP-1c were found increased through N-terminal truncation. Taken together, our data suggest divergent roles for the 3 BgRAP-1s in the merozoite stage ofB. gibsoni.

[Vector-borne parasites of dogs on the Islands of Cabo Verde]

During an animal welfare campaign on the Islands of Cape Verde (in the capital Praia on the island of Santiago) a total of 57 dogs were examined for ectoparasites and blood parasites. 84% of the animals were infested with arthropods, mostly ticks. Haemotropic parasites were examined via blood smear, polymerase chain reaction (PCR) and/or serology. 23 dogs had single infections, five multiple infections with haemoparasites. In eight dogs Ehrlichia canis and in one Amaplasma phagocytophilum were detected by PCR, while 43.1% and 36.2% respectively were serologically positive. In 23 blood smears Babesia gibsoni, but no Babesia canis could be detected. In four cases Hepatozoon canis was found in the smears. All animals were negative for Dirofilaria larvae or antibodies against Leishmania. Arthropod-infested animals more frequently harboured babesiae (44%), ehrlichiae (19%) or H. canis (8%) compared to non-infested animals (20%, 0%, 0%). In bitches and dogs aged one year or less babesiae were more frequently detected (48% of the bitches and 13% of the male dogs; 45% of animals less than one year and 26% of the older ones). Due to the high infection rates the import of animals from Cabo Verde to Central Europe must be seen as critical, since an endemisation of (sub-)tropical infectious agents cannot be excluded.

Characterization of a leucine aminopeptidase of Babesia gibsoni

Peptidases of parasitic protozoa are currently under intense investigation in order to identify novel virulence factors, drug targets, and vaccine candidates, except in Babesia. Leucine aminopeptidases in protozoa, such as Plasmodium and Leishmania, have been identified to be involved in free amino acid regulation. We report here the molecular and enzymatic characterization, as well as the localization of a leucine aminopeptidase, a member of the M17 cytosolic aminopeptidase family, from B. gibsoni (BgLAP). A functional recombinant BgLAP (rBgLAP) expressed in Escherichia coli efficiently hydrolysed synthetic substrates for aminopeptidase, a leucine substrate. Enzyme activity of the rBgLAP was found to be optimum at pH 8·0 and at 37°C. The substrate profile was slightly different from its homologue in P. falciprum. The activity was also strongly dependent on metal divalent cations, and was inhibited by bestatin, which is a specific inhibitor for metalloprotease. These results indicated that BgLAP played an important role in free amino acid regulation.

Alterations in some blood coagulation parameters in naturally occurring cases of canine babesiosis

Changes in coagulation parameters were studied in dogs naturally infected with Babesia canis canis (n = 30), and haemostasis was evaluated and compared to values obtained from healthy dogs (n = 29). To date, there have not been any studies examining the dynamics of thrombin-antithrombin complex formation in cases of canine babesiosis. Coagulation parameters evaluated before (day 0) and on days 1, 2, and 3 after treatment with imidocarb (6 mg/kg inj. s.c.) included the determination of platelet counts, the formation of thrombin-antithrombin complexes (TAT), prothrombin time (PT), activated partial thromboplastin time (APTT) and antithrombin III (AT III) activity. TAT complexes were significantly elevated in animals with babesiosis on days 0 and 2 (mean 49.7 and 87.7 microg/L vs. control, 7.2 microg/L). AT III activity was significantly decreased at all time-points examined. There were no differences in PT. On days 2 and 3 the APTT was significantly shortened in the infected dogs when compared to control animals (means of 21.3 and 19.2 s vs. control, 30.0 s). Our analysis demonstrated that infected dogs had significant thrombocytopenia during the course of the study (mean day 0 - 29 x 10(9) /L, day 1 - 48 x 10(9) /L, day 2 - 47 x 10(9) /L and day 3 - 87 x 10(9) /L, vs. control -259 x 10(9) /L). These data suggest that babesiosis in dogs compromise primary and secondary haemostasis and that induction of disseminated intravascular coagulation (DIC) occurs in canine babesiosis.

Identification of secreted antigen 3 from Babesia gibsoni

A cDNA expression library of Babesia gibsoni was screened with the serum collected from a dog experimentally infected with B. gibsoni. A novel antigen sharing homology with secreted antigen 1 of B. gibsoni was isolated. The genomic analysis indicated that the BgSA3 gene exists as multicopies in the genome of B. gibsoni. The putative peptide encoded by the BgSA3 gene showed some characteristics of secreted proteins. The serum raised in mice immunized with the recombinant BgSA3 expressed in Escherichia coli could recognize a native parasite protein with a molecular mass of 70 kDa. Moreover, a sandwich enzyme-linked immunosorbent assay with anti-BgSA3 antibodies could detect the circulating BgSA3 in the blood plasma of dogs experimentally infected with B. gibsoni. The identification of BgSA3 provided a useful target for the development of a diagnostic test for detecting specific antibodies and circulating antigens.

Evaluation of efficacy of bruceine A, a natural quassinoid compound extracted from a medicinal plant, Brucea javanica, for canine babesiosis

Bruceine A, a natural quassinoid compound extracted from the dried fruits of Brucea javanica (L.) Merr., was evaluated for its antibabesial activity in vitro and in vivo. Bruceine A inhibited the in vitro growth of Babesia gibsoni in canine erythrocytes at lower concentration compared with the standard antibabesial drug diminazene aceturate and killed the parasites within 24 hr at a concentration of 25 nM. Oral administration of bruceine A at a dosage of 6.4 mg/kg/day for 5 days resulted in no clinical findings in a dog with normal ranges of hematological and biochemical values in the blood. Three dogs were infected with B. gibsoni and two of them were treated with bruceine A at a dosage of 6.4 mg/kg/day for 6 days from day 5 post-infection. An untreated dog developed typical acute babesiosis symptoms including severe anemia, high fever, and complete loss of appetite and movement. However, the two bruceine A-treated dogs maintained their healthy conditions throughout the experimental period of 4 weeks although complete elimination of parasites from the peripheral blood was not achieved and decreases in the packed cell volume and the erythrocyte and platelet counts were observed. Since natural quassinoid compounds have been used as traditional medicines for the treatment of various ailments including cancer and malaria, the present results suggest that bruceine A or other related compounds are potential candidates for the treatment of canine babesiosis.

Genetic diversity of two selected antigen loci in Babesia gibsoni Asian genotype obtained from Japan and Jeju island of South Korea

Previous reports have shown that the secreted antigen 1 of Babesia gibsoni (BgSA1) and the thrombospondin-related adhesive protein of B. gibsoni (BgTRAP) are promising diagnostic reagents and vaccine candidates. Therefore, we determined the extent of nucleotide sequence variation in the BgSA1 and BgTRAP genes, obtained from eight isolates of B. gibsoni got from clinically infected dogs in geographically distinct areas of Japan and one isolate from Jeju island of South Korea. Sequence analyses have revealed that nucleotide diversity is lower in BgSA1 than that in BgTRAP. The mean number of non-synonymous (dn) nucleotide substitutions was significantly greater than that of synonymous (ds) ones per site in region II of BgTRAP. Overall, the results predict more allele-specific immunity to BgTRAP than that to BgSA1, which could be useful in designing and testing efficacy of diagnostic reagents as well as vaccine candidates for the B. gibsoni isolates from Japan and Jeju island of South Korea.

Cloning, expression, and characterization of Babesia gibsoni dihydrofolate reductase-thymidylate synthase: inhibitory effect of antifolates on its catalytic activity and parasite proliferation

Dihydrofolate reductase-thymidylate synthase (DHFR-TS) is a well-validated antifolate drug target in certain pathogenic apicomplexans, but not in the genus Babesia, including Babesia gibsoni. Therefore, we isolated, cloned, and expressed the wild-type B. gibsoni dhfr-ts gene in Escherichia coli and evaluated the inhibitory effect of antifolates on its enzyme activity, as well as on in vitro parasite growth. The full-length gene consists of a 1,548-bp open reading frame encoding a 58.8-kDa translated peptide containing DHFR and TS domains linked together in a single polypeptide chain. Each domain contained active-site amino acid residues responsible for the enzymatic activity. The expressed soluble recombinant DHFR-TS protein was approximately 57 kDa after glutathione S-transferase (GST) cleavage, similar to an approximately 58-kDa native enzyme identified from the parasite merozoite. The non-GST fusion recombinant DHFR enzyme revealed K(m) values of 4.70 +/- 0.059 (mean +/- standard error of the mean) and 9.75 +/- 1.64 microM for dihydrofolic acid (DHF) and NADPH, respectively. Methotrexate was a more-potent inhibitor of the enzymatic activity (50% inhibition concentration [IC(50)] = 68.6 +/- 5.20 nM) than pyrimethamine (IC(50) = 55.0 +/- 2.08 microM) and trimethoprim (IC(50) = 50 +/- 12.5 microM). Moreover, the antifolates' inhibitory effects on DHFR enzyme activity paralleled their inhibition of the parasite growth in vitro, indicating that the B. gibsoni DHFR could be a model for studying antifolate compounds as potential drug candidates. Therefore, the B. gibsoni DHFR-TS is a molecular antifolate drug target.

Babesia canis canis and Babesia canis vogeli infections in dogs from northern Portugal

Canine babesiosis represents an important veterinary medical problem. This study describes the molecular characterization of babesial parasites detected in eight clinically suspected dogs from northern Portugal, affected by lethargy, muscle tremors, weight loss, pale mucous membranes, hyperthermia or red-coloured urine. Microscopic examination of peripheral blood smears showed large intraerythrocytic piroplasms morphologically compatible with Babesia canis in all eight animals. DNA was extracted from blood on filter paper, and a Babesia spp. infection confirmed by polymerase chain reaction (PCR) amplification of a 408bp fragment of the 18S rRNA gene. Analysis of PCR-derived sequences revealed that seven dogs were infected with B. canis canis and one with B. canis vogeli. This is the first molecular identification report of both the species B. canis and the subspecies B. canis canis and B. canis vogeli in dogs from Portugal.

A Possible treatment strategy and clinical factors to estimate the treatment response in Bebesia gibsoni infection

The effectiveness of combination therapy using clindamycin, metronidazole and doxycycline against canine babesiosis, and the usefulness of platelet count and the plasma C-reactive protein (CRP) concentration as an estimation factor for treatment, were evaluated in four dogs experimentally infected with Babesia gibsoni. The combination therapy successfully eliminated B. gibsoni in peripheral blood in 3 of 4 dogs, however the remaining dog showed obvious uncontrolled relapse after a temporary recovery. In addition, it was shown that CRP levels decreased in an inverse relationship to the recovery of packed cell volume and therefore CRP levels could be used as an optional clinical marker to estimate the response to treatment.

Babesia gibsoni: Identification of an immunodominant, interspersed repeat antigen

In this report, an immunodominant antigen called BgIRA from Babesia gibsoni is identified and described. A highly repetitive antigen was screened from a cDNA library. The genomic BgIRA gene exists as single cope gene and contains 10 introns. BgIRA plays a dominant role in the immune response in dogs infected with B. gibsoni. The specificity and sensitivity of the rBgIRA in an ELISA indicated that this antigen might be useful in a diagnostic test.

A shared antigen among Babesia species: ribosomal phosphoprotein P0 as a universal babesial vaccine candidate

Babesia gibsoni ribosomal phosphoprotein P0 (BgP0) was previously identified as a cross-protective antigen against Babesia microti infection in mice. Interestingly, the same protein showed considerable antigenicity when tested with serum samples collected from Babesia-infected animals. Moreover, the polyclonal antibody raised against the recombinant BgP0 (rBgP0) recognized the P0 homologues from other Babesia species either by immunoblotting or by immunoscreening. The P0 genes from Babesia caballi, Babesia equi, and Babesia bigemina were then cloned and sequenced. The phylogenic analyses based on the amino acid sequences indicated that BgP0 has high identities with B. caballi P0 (88.1%), B. bigemina P0 (85.6%), Babesia bovis P0 (81.4%), and B. equi P0 (64.9%). Western blot analyses revealed that the corresponding native proteins ranged between 31 and 34 kDa, consistent with predicated molecular weight of Babesia P0. Furthermore, the immunogenic property of anti-rBgP0 IgG was evaluated against a B. bovis in vitro culture. The growth of B. bovis parasites was restricted by anti-rBgP0 IgG in a concentration-dependent manner, and significant reductions in parasitemia were observed only at 1 mg/ml in the culture. Taken together, these data suggest that P0 is a conserved protective antigen among Babesia species and might be a potentially universal vaccine candidate for babesiosis.

A novel 57-kDa merozoite protein of Babesia gibsoni is a prospective antigen for diagnosis and serosurvey of canine babesiosis by enzyme-linked immunosorbent assay

We isolated a novel single copy gene encoding a 57-kDa merozoite protein of Babesia gibsoni (BgP57). The nucleotide sequence of the cDNA was 2387 bp with an open reading frame (ORF) of 1644 bp encoding a 57-kDa predicted polypeptide having 547 amino acid residues. The recombinant BgP57 (rBgP57) without a predicted signal peptide was expressed in Escherichia coli as a soluble glutathione S-transferase (GST) fusion protein. Western blotting showed that the corresponding native protein was 57-kDa, consistent with molecular weight of predicted mature polypeptide. An indirect enzyme-linked immunosorbent assay (ELISA) using the rBgP57 detected specific antibodies in the sequential sera from a dog experimentally infected with B. gibsoni. Moreover, the antigen did not cross-react with antibodies to B. canis sub-species and closely related apicomplexan parasites indicating that the rBgP57 was a specific antigen for B. gibsoni antibodies. The diagnostic performance of ELISA based on rBgP57 using 107 sera from B. gibsoni-naturally infected dogs was the same as the previously identified rBgP32 but performed better than the previously studied rBgP50. Although, seminested PCR detected higher proportions (82%) of positive samples than the ELISAs, the Mcnemar's chi-square test showed that there was no significant difference in relative effectiveness of rBgP57-ELISA and seminested PCR (chi(2)=2.70; P=0.1003) in identifying positive samples. The rBgP57-ELISA when used in combination with rBgP32-ELISA and rBgP50-ELISA appeared to improve sensitivity of the rBgP57-ELISA for detection of B. gibsoni antibodies. Overall, the rBgP57-ELISA and seminested PCR when used in combination, could improve epidemiological surveys and clinical diagnosis of B. gibsoni infection.

Clinico-pathological findings and coagulation disorders in 45 cases of canine babesiosis in Spain

A retrospective study of clinical cases of babesiosis in dogs examined at the Veterinary Teaching Hospital, Rof Codina, from January 2003 to October 2004 is presented. The diagnosis was confirmed by direct observation of large piroplasms in stained blood smears. Dogs with concurrent diseases were excluded from the study. Clinical signs, complete blood count, serum biochemistry and hemostasis profiles were obtained. The observed clinical signs were due to hemolytic anemia and inflammatory responses but the most relevant clinico-pathological findings were related to alterations in hemostasis. All dogs presented with thrombocytopenia and 20% had disseminated intravascular coagulation syndrome. Anemia of variable severity was observed in most of the dogs.

Clinical management of babesiosis in dogs with homeopathic Crotalus horridus 200C

Homeopathic Crotalus horridus 200C was evaluated in 13 clinical cases of babesiosis in dogs, compared with another 20 clinical cases treated with diminazine. Babesiosis is an important tropical tick-borne haemoprotozoan disease in dogs clinically manifested by anorexia, dehydration, temperature, dullness/depression, diarrhoea/constipation, pale mucosa, hepatomegaly, vomiting/nausea, splenomegaly, distended abdomen/ascites, yellow coloured urine, emaciation/weight loss, and occular discharge. The diagnosis of babesiosis was based on cytological evidence of Babesia gibsoni in freshly prepared blood smears. The dogs were treated with oral C. horridus 200C, 4 pills four times daily for 14 days (n=13) or diminazine aceturate 5 mg/kg single intramuscularly dose (n=20). All the dogs were administered 5% Dextrose normal saline at 60 ml/kg intravenously for 4 days. Initial clinical scores were similar in both groups and showed similar progressive improvement with the two treatments over 14 days. Parasitaemia also improved in both groups, but haematological values showed no change. No untoward reactions were observed. It appears that C. horridus is as effective in causing clinical recovery in moderate cases of canine babesiosis caused by Babesia gibsoni as the standard drug diminazine. Large scale randomized trials are indicated for more conclusive results.

Molecular characterization of a novel 32-kDa merozoite antigen of Babesia gibsoni with a better diagnostic performance by enzyme-linked immunosorbent assay

We cloned and expressed a novel gene encoding a 32-kDa merozoite protein of Babesia gibsoni (BgP32). The length of nucleotide sequence of the cDNA was 1464 bp with an open reading frame of 969 bp. The truncated recombinant BgP32 (rBgP32) without a signal peptide and C-terminal hydrophobic sequence was expressed in Escherichia coli as a soluble glutathione-S-transferase (GST) fusion protein. Western blotting demonstrated that the native protein was 32-kDa, consistent with molecular weight of the predicted mature polypeptide. Enzyme-linked immunosorbent assay (ELISA) using rBgP32 detected specific antibodies from 8 days to 541 days post-infection in the sequential sera from a dog experimentally infected with B. gibsoni. Moreover, the antigen did not cross-react with B. canis subspecies and closely related protozoan parasites, indicating that rBgP32 is a specific diagnostic antigen. Analysis of 47 sera taken from dogs with anaemic signs revealed that rBgP32 detected a higher proportion of B. gibsoni seropositive samples (77%) than its previously identified rBgP50 (68%) homologue. These results indicate that the BgP32 is a novel immunodominant antigen of B. gibsoni, and rBgP32 might be useful for diagnosis of B. gibsoni infection.