Development of a polymerase chain reaction method for diagnosing Babesia gibsoni infection in dogs

The Etiology, Incidence, Pathogenesis, Diagnostics, and Treatment of Canine Babesiosis Caused by Babesia gibsoni Infection

Simple Summary

Babesia gibsoni is a parasite that causes the rupture of red blood cells in dogs. Although there is no natural, tick-borne transmission of this disease in Europe, it has become more common in European countries in recent years. Dogfighting breeds are predisposed to disease and they are a potential source of infection. Given the high popularity of these dog breeds in Europe and the participation of many dogs at sports competitions and shows, it is likely that the incidence of the disease in Europe may be higher than expected. The fact that the disease is mostly manifested as asymptomatic infection and that dogs of predisposed breeds are often imported from endemic areas, or they travel due to mating or competitions around the world, also contributes to this hypothesis.

Abstract

Babesia gibsoni is one of the small Babesia species and the infection this pathogen causes is usually asymptomatic, which complicates the capture of potential parasite carriers. In endemic areas, especially in Asia, B. gibsoni occurs quite often due to direct transmission by way of a tick vector. Due to the absence of vectors, its occurrence is described only sporadically in Europe; but, it is increasingly occurring in predisposed, so-called fighting breeds, especially the American pit bull terrier. This review describes the etiology, incidence, clinical signs, pathogenesis, diagnostics, and treatment of B. gibsoni infection, with an emphasis on the clinical and laboratory peculiarities of the disease. As the treated dogs do not eliminate the parasite from the body—only reducing parasitemia and improving clinical signs—the treatment of B. gibsoni infection is a challenge in many cases, and its study therefore deserves great attention.

Clinical Efficacy and Safety of Malarone®, Azithromycin and Artesunate Combination for Treatment of Babesia gibsoni in Naturally Infected Dogs

Babesia gibsoni is a tick-borne protozoal blood parasite that may cause hemolytic anemia, thrombocytopenia, lethargy, and/or splenomegaly in dogs. Many drugs have been used in management of canine babesiosis such as monotherapy or combined treatment, including diminazene aceturate, imidocarb dipropionate, atovaquone, and antibiotics. This report examines the effectiveness and safety of Malarone®, azithromycin (AZM) and artesunate (ART) combination for the treatment of babesiosis in dogs naturally infected with Babesia gibsoni. Twelve American Pit Bull Terriers were included in the experiment. Examined dogs underwent clinical and laboratory analysis including hematology and biochemistry profile and serum protein electrophoresis. After diagnosis, the dogs received combined therapy with Malarone® (13.5 mg/kg PO q24 h), azithromycin (10 mg/kg PO q24 h) and artesunate (12.5 mg/kg PO q24 h) for 10 days. The combined treatment improved hematology and biochemical parameters to the reference range gradually during the first 14 days already, resulting in the stable values until day 56 after treatment. No clinically apparent adverse effects were reported during treatment and monitoring. No relapses of parasitemia were detected in control days 180, 360, 540 and 720 in all dogs. Results of the study indicate that the combined treatment leads to successful elimination of parasitemia in chronically infected dogs with B. gibsoni.

Further epidemiological survey for atovaquone resistant related gene of Babesia gibsoni in Japan during 2015-2018

A single-nucleotide polymorphism causing the replacement of methionine with isoleucine (M121I) in cytochrome b of Babesia gibsoni has been reported to reduce the susceptibility to atovaquone (ATV) in B. gibsoni infection. In our previous study, B. gibsoni with M121I was suggested to exist in nature. Thus, further examinations were performed. In total, 105 genomic DNA samples from B. gibsoni-infected dogs were collected from western (98 samples from 15 prefectures) and eastern areas (7 samples from 4 prefectures) in Japan. The M121I variant population was identified using allele-specific real-time PCR: it was then detected in nine samples (8.57%), which was higher than that in the previous study (4.11%). Although there are unclear points, such as the history of ATV usage, careful attention should be given to emerging ATV resistance.

A novel PCR-based point-of-care method enables rapid, sensitive and reliable diagnosis of Babesia gibsoni infection in dogs

BACKGROUND

Babesia gibsoni (B. gibsoni) is an intraerythrocytic protozoan parasite of dogs that causes fever and hemolytic illness. A timely diagnosis is essential for the disease management.

RESULTS

Here, we report a QubeMDx PCR system which enables a rapid, sensitive and reliable diagnosis of B. gibsoni near the dog patient. Within 30 min, this diagnostic assay was able to detect as low as 0.002% parasitemia of the dog blood. Using clinical samples, this new assay was validated to demonstrate 100% agreement with real-time PCR.

CONCLUSIONS

This novel diagnostic method provides a reliable point-of-care test to assist in the identification of B. gibsoni.

Comparison of conventional polymerase chain reaction and routine blood smear for the detection of Babesia canis, Hepatozoon canis, Ehrlichia canis, and Anaplasma platys in Buriram Province, Thailand

Background and Aim:

Dog blood parasites are important tick-borne diseases causing morbidity and mortality in dogs worldwide. Four dog blood parasites species are commonly found in Thailand: Babesia canis, Hepatozoon canis, Ehrlichia canis, and Anaplasma platys. They are transmitted easily by tick species. However, there is little prevalence data available in Thailand. Diseases presentation of blood parasites infection is similar, but the treatment of each species is different. Current diagnosis mainly relies on microscopic examination of a stained blood smear, which has low sensitivity. Therefore, accurate diagnosis is important. This study aims to evaluate the efficacy of the conventional polymerase chain reaction (PCR) method and routine blood smears in the detection of four blood parasites species in dogs from Buriram Province, Thailand.

Materials and Methods:

In total, 49 EDTA-blood samples were collected from dogs in Buriram Province, Thailand. Blood parasite infection was compared using the Giemsa-stained blood smear technique to identify the parasite under a 100× oil immersion with PCR amplification of the 18S rDNA gene of B. canis and H. canis and the 16S rDNA gene of E. canis and A. platys.

Results:

Only one dog out of 49 was positive for H. canis based on microscopic examination whereas the PCR results showed that 2.04% (1/49), 4.08% (2/49), 36.73% (18/49), and 30.61% (15/49) of dogs were positive for B. canis, H. canis, E. canis, and A. platys, respectively. Moreover, coinfection was found in 16.33% (8/49) of dogs.

Conclusion:

This study is the first report to demonstrate the molecular prevalence of blood parasites in domestic dogs in Buriram Province. The results indicated that the PCR method exhibited much higher sensitivity and reliability for blood parasites diagnosis in dogs. Therefore, our data support serious concern regarding the diagnostic technique used in routine blood testing and also provide prevalence data for the management and control of blood parasites in this area.

Optimal Vector-borne Disease Screening in Dogs Using Both Serology-based and Polymerase Chain Reaction-based Diagnostic Panels

Vector-borne disease and idiopathic immune-mediated disease present similarly. Diagnostic panels that include multiple organisms help detect infection and identify coinfections. Comprehensive diagnostic panels that combine polymerase chain reaction (PCR) and serology should be used in initial screening to maximize sensitivity and identify infection. Repeat testing using PCR is warranted in dogs at high risk of infection with organisms that circulate in blood in low numbers or intermittently. Convalescent serologic testing can help diagnose acute infection. This article discusses the pathophysiology and epidemiology of the organisms, panel selection, and how to recognize when more aggressive testing for an organism is warranted.

The role of healthy dog carriers of Babesia microti-like piroplasms

BACKGROUND

While in Europe Babesia canis has been traditionally held responsible for canine piroplasmosis, Babesia microti-like piroplasm (Bml) infection is being ever more observed in dogs, with the first clinical cases reported in northwestern Spain. This study examines the epidemiological role of healthy dogs living in endemic areas of Bml infection in Spain. The data obtained were used to describe the clinical status and map the geographical distribution of Bml infection in healthy dogs in northwestern Spain.

RESULTS

Blood samples and ticks were taken from 756 healthy dogs representatively across the whole Galicia region (northwestern Spain): stray (n = 211), hunting dogs (n = 333) and pets (n = 212). Blood samples were tested by microscopy parasite observation, nested PCR-RFLP and sequencing. Piroplasm infection prevalences in healthy dogs from northwestern Spain were 17.1% (129/756) by PCR and 3.4% (26/756) by microscopy observation. The species found by PCR were: 2.2% (17/756) for B. canis and 15.1% (114/756) for Bml. Co-infection with B. canis and Bml was noted in 2 dogs. The higher prevalences detected were Bml in hunting dogs (25.5%; 85/333) and B. canis in stray dogs (6.6%; 14/211). In fox-hunting dogs from any area and dogs from the A Coruña Province, significantly higher prevalences of Bml infection were detected (P < 0.001). Upon physical examination, tick infestation was observed: 130 ticks in 18 hunting and three pet dogs. These were subsequently identified as Rhipicephalus sanguineus (s.l.) (49.2%), Ixodes hexagonus (38.5%), Ixodes ricinus (6.9%) and Dermacentor reticulatus (5.4%). Among the more prevalent ticks infesting healthy carrier dogs were I. hexagonus, followed by D. reticulatus and I. ricinus.

CONCLUSIONS

Babesia canis and Bml were the only piroplasm species found infecting healthy dogs in Galicia, the prevalence of Bml being higher than of B. canis. Factors correlated with a higher Bml infection risk were being a hunting dog and living in the A Coruña Province. Healthy dogs travelling to other countries could act as carriers and probably contribute to the spread of Bml infection in dogs and wild carnivores throughout Europe.

Babesia microti-like piroplasm (syn. Babesia vulpes) infection in red foxes (Vulpes vulpes) in NW Spain (Galicia) and its relationship with Ixodes hexagonus

Piroplasmosis is caused by several species of protozoa such as the Babesia microti-like piroplasm (Bml), an emerging blood protozoan also known as Theileria annae or Babesia vulpes. Infection by Bml was first reported in dogs in Spain where it is endemic today. Recently, a high prevalence of Bml has been increasingly detected in red foxes (Vulpes vulpes) in European countries. The objective of this study was to determine infection levels of this parasite in foxes from Galicia, NW Spain, and ticks species infestation in these carnivores, where they are so far unknown. Samples of blood, spleen and ticks (if present) were taken from 237 hunted red foxes in the Galicia region. Blood smears were prepared for direct parasite observation, and spleen and tick samples were examined by nested PCR. Prevalences of Bml infection in Galician red foxes were estimated at 72% (171/237) by PCR and 38.23% (26/68) by direct observation. Among 837 ticks collected, the main tick identified was Ixodes hexagonus (present in 82.4% of the foxes) followed by Ixodes ricinus (12.3%), Dermacentor reticulatus (12.3%) and Rhipicephalus sanguineus sensu lato (3.5%). From 34 foxes testing positive for Bml, 616 ticks were collected: positive Bml PCR results were obtained in 55.6% (227/408) of ticks collected from 9 foxes, while the 208 ticks from the remaining 25 infected foxes returned negative PCR results. Given that canine piroplasmosis is endemic in this area, our observations point to the red fox as the main reservoir for Bml infection and the high proportion of I. hexagonus among ticks collected from red foxes suggests its likely role as vectors of B. microti-like piroplasm in this region. Further studies are needed for a better understanding of the link between the wild and domestic life cycles of this piroplasm.

Efficacy, safety and tolerance of imidocarb dipropionate versus atovaquone or buparvaquone plus azithromycin used to treat sick dogs naturally infected with the Babesia microti-like piroplasm

BACKGROUND

Piroplasmosis caused by the Babesia microti-like piroplasm (Bml) is increasingly being detected in dogs in Europe. Sick dogs show acute disease with severe anaemia associated with thrombocytopenia with a poor response to current available drugs. This study assesses the safety and tolerance of three treatments and compares their efficacy over a full year of follow up in dogs naturally infected with Bml.

METHODS

Fifty-nine dogs naturally infected with Bml were randomly assigned to a treatment group: imidocarb dipropionate (5 mg/kg SC, 2 doses 14 d apart) (IMI); atovaquone (13.3 mg/kg PO q 8 h, 10 d)/azithromycin (10 mg/kg PO q 24 h, 10 d) (ATO); or buparvaquone (5 mg/kg IM, 2 d apart)/azithromycin (same dosage) (BUP). Before and after treatment (days 15, 45, 90 and 360), all dogs underwent a physical exam, blood tests and parasite detection (blood cytology and PCR). Clinical efficacy was assessed by grading 24 clinical and 8 clinicopathological signs from low to high severity.

RESULTS

Before treatment, most dogs had severe regenerative anaemia (88.13%) and thrombocytopenia (71.4%). On treatment Day 45, clinical signs were mostly reduced in all dogs, and by Day 90, practically all dogs under the ATO or BUP regimen were clinically healthy (76.4 and 88%, respectively). Highest percentage reductions in laboratory abnormalities (82.04%) were detected in animals treated with ATO. Over the year, clinical relapse of Bml was observed in 8 dogs (8/17) treated with IMI. However, on Day 360, these animals had recovered clinically, though clinicopathological abnormalities were still present in some of them. Parasitaemia was PCR-confirmed on Days 90 and 360 in 47.05 and 50% of dogs treated with ATO, 68 and 60.08% with BUP, and 94.1 and 73.3% with IMI, respectively. Even after 360 days, 13.3% of the dogs treated with IMI returned a positive blood cytology result.

CONCLUSIONS

IMI showed the worse clinical and parasitological, efficacy such that its use to treat Bml infection in dogs is not recommended. The treatments ATO and BUP showed better efficacy, though they were still incapable to completely eliminate PCR-proven infection at the recommended dose. All three treatments showed good tolerance and safety with scarce adverse events observed.

Molecular identification of Babesia spp. in naturally infected dogs of Kerala, South India

Canine babesiosis is a tick borne haemoprotozoan disease caused by large and small intraerythrocytic apicomplexan piroplasms of the genus Babesia spp. The clinical manifestations of the disease vary from inapparent subclinical form to hyperacute shock related haemolytic crisis. Microscopic examination of blood smears from suspected dogs revealed Babesia canis and B. gibsoni in 3.45 and 25.86 % of samples respectively. A seminested PCR based on previously published species specific primers targeting the 18S rRNA gene was utilized to identify the Babesia species infecting dogs of Kerala at the sub species level. The study revealed 57.5 % prevalence of Babesia spp. among dogs. This report also presents the first molecular evidence of Babesia canis vogeli and B. gibsoni among naturally infected dogs in Kerala, South India. Molecular survey revealed a high prevalence of B. gibsoni infections when compared with B. canis vogeli infections among canines of the state. Preliminary survey of the tick population revealed the presence of Rhipicephalus sanguineus, R. haemaphysaloides and Haemaphysalis bispinosa in infected animals. Further studies need be directed towards utilizing the PCR protocol for confirming the vectors of these species in the region.

Development of a SYBR Green Real-Time Polymerase Chain Reaction Assay for Quantitative Detection of Babesia Gibsoni (Asian Genotype) DNA

A real-time fluorogenic polymerase chain reaction (PCR) assay based on SYBR green that allows for sensitive, reproducible, and accurate quantification of Babesia gibsoni (Asian genotype). DNA from peripheral blood of infected dogs was developed. Standard curves were created by plotting the input amount of a standard template, constructed with plasmid DNA containing 182 base pairs (bp) of the p18 gene, against threshold cycle numbers. The curves showed a wide dynamic range (1,000,000-fold input) and high correlation values (>0.99). The PCR amplification efficacy of the standard template was similar to that of intact genomic DNA obtained from peripheral blood with B. gibsoni infection. The detection limit of the assay was 9 parasites/μl of blood with B gibsoni infection. The intra-assay and interassay coefficients of variation of the threshold cycles ranged from 0.70% to 1.89% and from 1.18% to 1.92%, respectively. This assay system was found to be reproducible and accurate for the quantification of parasite DNA in experimentally infected dogs and far more sensitive than traditional microscopic examination.

Molecular detection and genetic diversity of Babesia gibsoni in dogs in India

Babesia gibsoni is a tick borne intraerythrocytic protozoan parasite causing piroplasmosis in dogs and has been predominantly reported in Asian countries, including Japan, Korea, Taiwan, Malaysia, Bangladesh and India. The present communication is the first evidence on the genetic diversity of B. gibsoni of dogs in India. Blood samples were collected from 164 dogs in north and northeast states of India and 13 dogs (7.9%) were found positive for B. gibsoni infection by microscopic examination of blood smears. Molecular confirmation of these microscopic positive cases for B. gibsoni was carried out by 18S rRNA nested-PCR, followed by sequencing. Nested-PCR for the 18S rRNA gene was also carried out on microscopically B. gibsoni negative samples that detected a higher percentage of dogs (28.6%) infected with B. gibsoni. Genetic diversity in B. gibsoni in India was determined by studying B. gibsoni thrombospondin-related adhesive protein (BgTRAP) gene fragments (855bp) in 19 isolates from four north and northeast states of India. Phylogenetic analysis of the BgTRAP gene revealed that B. gibsoni parasite in India and Bangladesh formed a distinct cluster away from other Asian B. gibsoni isolates available from Japan, Taiwan and Korea. In addition, tandem repeat analysis of the BgTRAP gene clearly showed considerable genetic variation among Indian isolates that was shared by B. gibsoni isolates of Bangladesh. These results suggested that B. gibsoni parasites in a different genetic clade are endemic in dogs in India and Bangladesh. Further studies are required for better understanding of the genetic diversity of B. gibsoni prevalent in India and in its neighbouring countries.

Development of recombinant BgP12 based enzyme linked immunosorbent assays for serodiagnosis of Babesia gibsoni infection in dogs

Indirect ELISA and dot-ELISA using recombinant BgP12 (rBgP12) were developed for the diagnosis of Babesia gibsoni infected dogs. The complete open reading frame of BgP12 gene (378bp) was cloned in pET-32a(+) expression vector and expressed in Escherichia coli as a soluble thioredoxin (Trx) fusion protein. The purified rBgP12 was used for production of anti-rBgP12 rabbit serum, which recognized a native 12-kDa protein in B. gibsoni infected erythrocyte by Western blot analysis. To evaluate the potential of rBgP12 for the serodiagnosis of B. gibsoni, a panel of serum/plasma samples from dogs infected with B. gibsoni (n=13), uninfected sera (n=13) and sera from dogs infected with other haemoparasites viz., Babesia canis vogeli (n=3), Ehrlichia canis (n=3), Hepatozoon canis (n=1) and Dirofilaria immitis (n=1) were used in ELISA formats. In addition, the performance of rBgP12 based indirect ELISA and dot-ELISA were evaluated using 75 serum/plasma samples collected from suspected dogs, in respect to the nested PCR as reference test. The diagnostic sensitivities of indirect ELISA and dot-ELISA were 94.59% and 89.18%, respectively, while their specificities were 84.21% and 81.57%, respectively. Moreover, both the assays using rBgP12 showed no cross reaction with sera from dogs infected with other common haemoparasites indicating their high specificity. High kappa values of indirect ELISA and dot-ELISA indicated the potentials of these assays with substantial agreement at 95% confidence level. It is concluded that indirect ELISA and dot ELISA using rBgP12 might be used in large scale epidemiological surveys and clinical diagnosis of B. gibsoni infection in dogs.

The epidemiological survey for atovaquone resistant related gene of Babesia gibsoni in Japan

In 73 gDNA samples from Babesia gibsoni-infected dogs, the M121I variant population was measured by using allele-specific real-time PCR. Although the mechanism of atovaquone against B. gibsoni has not been clearly identified, it is reported that the mitochondria cytochrome b gene of the atovaquone-resistant B. gibsoni had a single-nucleotide substitution at nt363 (G to T), which resulted in the substitution of methionine with isoleucine (M121I). In this study, 3/73 samples showed over 5% M121I variant population. Although the M121I variant population is a low percentage, it runs the risk of spreading drug-resistant parasites. It is important to prevent the spread of drug-resistance, so we need to gather information about this at regular intervals.

Theileria annae (syn. Babesia microti-like) infection in dogs in NW Spain detected using direct and indirect diagnostic techniques: clinical report of 75 cases

Background

In north-western Spain, piroplamosis caused by Theileria annae is now recognized as a serious problem because veterinarians, despite being aware of the clinical signs of piroplasmosis, lack the necessary information on its epidemiology or specific diagnostic tools for its management. This, along with the fact that T. annae infection is also refractory to current piroplamosis treatments, prompted this study designed to assess the clinical presentation and diagnosis of this largely unknown parasitic disease in dogs.

Methods

One hundred and twenty dogs in NW Spain suspected clinically of having piroplasmosis were examined and piroplasm species detected by light microscopy (LM) observation of Giemsa-stained blood smears, immunofluorescent antibody test (IFAT), and PCR plus sequencing.

Results

Seventy five of the sick dogs were confirmed to be infected with T. annae by PCR (designated “true infection cases”). Intraerythrocytic ring-shaped bodies morphologically compatible with small piroplasms were observed by LM in 59 (57 true infections) of the 120 blood samples. Anti-Babesia antibodies were detected by IFAT in 59 of the 120 sera (55 of which were “true infections”). Using PCR as the reference method, moderate agreement was observed between positive LM vs PCR and IFAT vs PCR results (kappa values: 0.6680 and 0.6017, respectively). Microscopy examination and IFAT were moderately sensitive in detecting the pathogen (76% and 73.3%, respectively). In the 75 cases of “true infection”, the most common clinical signs observed were pale mucous membranes, anorexia and apathy. Blood cell counts consistently revealed severe regenerative anaemia and thrombocytopenia in dogs with piroplasmosis due to T. annae. Young dogs (≤3 year) (p = 0.0001) were more susceptible to the disease.

Conclusion

Microscopy showed moderate diagnostic sensitivity for acute T. annae infection while IFAT-determined antibody titres were low (1/64 to 1/128). The infecting species should be therefore confirmed by molecular tests. Our results suggest that the disease affects dogs in regions of Spain bordering the endemic Galicia area where this piroplasm has not been previously reported (Asturias, northern Spain). Further epidemiological surveys based on serological and molecular methods are required to establish the current geographical range of T. annae infection.

Molecular detection and genetic diversity of Babesia gibsoni in dogs in Bangladesh

Babesia gibsoni is a tick-borne hemoprotozoan parasite of dogs that often causes fever and hemolytic illness. Detection of B. gibsoni has been predominantly reported in Asian countries, including Japan, Korea, Taiwan, Malaysia, Bangladesh and India. The present study shows the first molecular characterization of B. gibsoni detected from dogs in Bangladesh. Blood samples were collected on FTA® Elute cards from 50 stray dogs in Mymensingh District in Bangladesh. DNA eluted from the cards was subjected to nested PCR for the 18S rRNA gene of Babesia species. Approximately 800bp PCR products were detected in 15 of 50 dogs (30%). Based on restriction fragment length polymorphism (RFLP) and direct sequencing of the PCR products, all parasite isolates were identified as B. gibsoni. Furthermore, the BgTRAP (B. gibsoni thrombospondin-related adhesive protein) gene fragments were detected in 13 of 15 18S rRNA gene PCR positive blood samples. Phylogenetic analysis of the BgTRAP gene revealed that B. gibsoni parasites in Bangladesh formed a cluster, which was genetically different from other Asian B. gibsoni isolates. In addition, tandem repeat analysis of the BgTRAP gene clearly showed considerable genetic variation among Bangladeshi isolates. These results suggested that B. gibsoni parasites in a different genetic clade are endemic in dogs in Bangladesh. Further studies are required to elucidate the origin, distribution, vector and pathogenesis of B. gibsoni parasites circulating in dogs in Bangladesh.

Canine babesiosis in northwestern India: molecular detection and assessment of risk factors

In the current study, a total of 214 blood samples from dogs in and around Ludhiana, Punjab (India), suspected for canine babesiosis were examined with conventional and molecular assays. Examination of Giemsa-stained peripheral thin blood smears revealed an overall prevalence of 7.47% (16/214) for canine babesiosis encompassing 0.93% (2/214) of large Babesia and 6.54% (14/214) of Babesia gibsoni. However, molecular diagnosis revealed 15.42% (33/214) samples positive for B. gibsoni infection as evident by the presence of 671 bp amplicon. The results of multivariate analysis showed that the prevalence of B. gibsoni was associated with various risk factors, namely, age (P < 0.001; OR: 0.398; CI 95%: 0.080–1.799), sex (P = 0.022; OR: 0.849; CI 95%: 0.403–1.791), breed of host (P = 0.371; OR: 3.345; CI 95%: 1.045–10.710), and season (P = 0.230; OR: 2.143; CI 95%: 0.788–5.830). The prevalence of B. gibsoni was higher in summer as compared to winter season and in younger dogs, while breed and sex of the host were not significantly associated with the occurrence of the disease.

Generalized alopecia with vasculitis-like changes in a dog with babesiosis

A locally bred, 12-year-old, intact female Satsuma dog presented with generalized alopecia. Erythema, crusts and desquamation were observed primarily on the truck. Papules and erosions were present in the pinnae, and there were multiple areas of skin necrosis on the right forelimb. The cutaneous lesions had not responded to treatment with systemic antibiotics and prednisolone. The dog also had progressive anemia. Babesia gibsoni was detected in the blood, and the dog was treated with antiprotozoal agents. The skin lesions and anemia improved, but relapsed after the treatment was discontinued. Histopathological examination of skin biopsies revealed findings suggestive of early leukocytoclastic vasculitis or ischemic vasculopathy.

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.

Current advances in detection and treatment of babesiosis

Babesiosis is a disease with a world-wide distribution affecting many species of mammals principally cattle and man. The major impact occurs in the cattle industry where bovine babesiosis has had a huge economic effect due to loss of meat and beef production of infected animals and death. Nowadays to those costs there must be added the high cost of tick control, disease detection, prevention and treatment. In almost a century and a quarter since the first report of the disease, the truth is: there is no a safe and efficient vaccine available, there are limited chemotherapeutic choices and few low-cost, reliable and fast detection methods. Detection and treatment of babesiosis are important tools to control babesiosis. Microscopy detection methods are still the cheapest and fastest methods used to identify Babesia parasites although their sensitivity and specificity are limited. Newer immunological methods are being developed and they offer faster, more sensitive and more specific options to conventional methods, although the direct immunological diagnoses of parasite antigens in host tissues are still missing. Detection methods based on nucleic acid identification and their amplification are the most sensitive and reliable techniques available today; importantly, most of those methodologies were developed before the genomics and bioinformatics era, which leaves ample room for optimization. For years, babesiosis treatment has been based on the use of very few drugs like imidocarb or diminazene aceturate. Recently, several pharmacological compounds were developed and evaluated, offering new options to control the disease. With the complete sequence of the Babesia bovis genome and the B. bigemina genome project in progress, the post-genomic era brings a new light on the development of diagnosis methods and new chemotherapy targets. In this review, we will present the current advances in detection and treatment of babesiosis in cattle and other animals, with additional reference to several apicomplexan parasites.

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.

Detection of Babesia vogeli in stray cats of metropolitan Bangkok, Thailand

The combination of a rapidly growing stray animal population and the lack of animal control in Bangkok has resulted in a unique opportunity to evaluate the potential role of companion animals as sentinels and reservoirs of infectious diseases, including several of those caused by vector-borne parasites. The purpose of this study was to determine the prevalence and factors associated with the distribution of Babesia species infections among stray cats in Bangkok. Blood samples were collected from 1490 stray cats residing in 140 monasteries of 50 metropolitan districts of Bangkok, and assayed with light microscopy and PCR for evidence of Babesia spp. Pear-shaped merozoites were observed microscopically from two (0.13%) of these cats, while a nested 18S rDNA-based PCR assay detected babesial infections in 21 (1.4%) of the cats tested. The prevalence of infection was significantly different between sexes (p<0.05), and PCR-positive cats were found in 30% (15/50) of the districts surveyed. All 21 amplicon sequences were identical, and were determined to be closest to that reported for B. vogeli (98% identity). These results represent the first molecular confirmation that a Babesia sp. is enzootic among stray cat populations in Thailand, and suggest that the presence of pet companion animals could be a risk factor for exposure of stray cats to vector-borne parasites.

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.

Detection of Babesia gibsoni by reaction of phage display single chain antibodies with P50 proteins

Babesia gibsoni (B. gibsoni) is a tick-borne hemoprotozoan parasite, which causes piroplasmosis in dogs. Diagnosis of canine babesiosis is commonly carried out using Giemsa-stained thin blood smears. However, at low levels of infection, it is difficult to detect Babesia organisms by observation of Giemsa-stained thin blood smears. We constructed a monoclonal phage display single chain antibody (scFv) against a B. gibsoni merozoite antigen, P50 protein. Intraerythrocytic B. gibsoni organisms are clearly stained using this antibody. The monoclonal scFv facilitated the detection of B. gibsoni organisms in canine blood samples.

Canine babesiosis: from molecular taxonomy to control

Canine babesiosis is a clinically significant emerging vector-borne disease caused by protozoan haemoparasites. This review article considers recent literature pertaining to the taxonomic classification of Babesia and Theileria species affecting dogs and the geographical distribution of these parasites. The diagnosis of canine babesiosis by traditional, molecular and serological methods is reviewed, together with recent advances in our understanding of the pathophysiology of piroplasmosis, and of the treatment and prevention of this disease.

Tick vitellogenin receptor reveals critical role in oocyte development and transovarial transmission of Babesia parasite

A cDNA encoding the vitellogenin receptor of the ixodid tick, Haemaphysalis longicornis Neumann (HlVgR) was cloned and characterized. The full-length cDNA is 5631 bp, including an intact ORF encoding an expected protein with 1782 amino acids. The deduced amino acid sequence of the HlVgR cDNA revealed two ligand-binding domains with four class A cysteine-rich repeats in the first domain and eight in the second domain similar to those of insect VgRs. The immunoblot analysis detected approximately 197 kDa protein in both tick ovary and egg. The developmental expression profile demonstrated that HlVgR mRNA exists throughout the ovarian development, and the transcriptional level is especially high in the previtellogenic period. Immuno electron microscopy analysis demonstrated that the localization of HlVgR is detected on the external surface of oocyte plasma membrane. RNAi showed that eggs of HlVgR dsRNA-injected adult ticks had not developed into fully mature oocytes and laid abnormal eggs. The Babesia parasite DNA was not detected in the eggs of HlVgR dsRNA-injected tick that fed on Babesia gibsoni infected dog, whereas it was detected in the eggs of PBS-injected ticks and noninjected ticks. Expression of HlVgR was increased by the vitellogenic hormone 20-hydroxyecdysone. These results indicate that HlVgR, which is produced by the developing oocytes, is essential for Vg uptake, egg development in the H. longicornis tick, and transovarial transmission of Babesia parasites.

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.

Molecular survey of Babesia canis in dogs in Nigeria

An epidemiological study of Babesia canis in dogs in Nigeria was performed. Four hundred blood samples collected from dogs in Nigeria were investigated using nested PCR and sequence analysis. On nested PCR screening, nine samples (2.3%) produced a band corresponding to a 698-bp fragment indicative of B. canis infection. Sequence analysis of the PCR products identified eight samples (2.0%) as B. canis rossi and the ninth (0.3%) as B. canis vogeli. This is the first report of the prevalence of B. canis rossi and B. canis vogeli in dogs in Nigeria.

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.

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.

Identification of three protein disulfide isomerase members from Haemaphysalis longicornis tick

Three genes encoding putative protein disulfide isomerase (PDI) were isolated from the Haemaphysalis longicornis EST database and designed as HlPDI-1, HlPDI-2, and HlPDI-3. All three PDI genes contain two typical PDI active sites CXXC and encode putative 435, 499, and 488 amino acids, respectively. The recombinant proteins expressed in Escherichia coli all show PDI activities, and the activities were inhibited by a PDI-specific inhibitor, zinc bacitracin. Western blot analysis and real-time PCR revealed that three HlPDIs were present in all the developmental stages of the tick as well as in the midgut, salivary glands, ovary, hemolymph, and fatbody of adult female ticks, but the three genes were expressed at the highest level in the egg stage. HlPDI-1 is expressed primarily in the ovary and secondarily in the salivary glands. HlPDI-2 and HlPDI-3 are expressed primarily in the salivary gland, suggesting that the PDI genes are important for tick biology, especially for egg development, and that they play distinct roles in different tissues. Blood feeding induced significantly increased expression of HlPDI-1 and HlPDI-3 in both partially fed nymphs and adults. Babesia gibsoni-infected larval ticks expressed HlPDI-1 and HlPDI-3 2.0 and 4.0 times higher than uninfected normal larval ticks, respectively. The results indicate that HlPDI-1 and HlPDI-3 might be involved in tick blood feeding and Babesia parasite infection in ticks.

Babesia gibsoni: detection during experimental infections and after combined atovaquone and azithromycin therapy

Babesia gibsoni is a protozoan parasite of dogs worldwide yet both an effective treatment and a reliable method for detecting subclinical cases of this emerging infection remain elusive. Experimental B. gibsoni infections were established in vivo to investigate the efficacy of combined atovaquone and azithromycin drug therapy and to determine the detection limits of a nested-PCR, IFAT and microscopy during various stages of infection. While atovaquone and azithromycin produced a reduction in parasitaemia, it did not eliminate the parasite and drug resistance appeared to develop in one dog. Polymerase chain reaction was found to be most useful in detecting infection in the pre-acute and acute stages, while IFAT was most reliable during chronic infections. Microscopy is suggested to be only effective for detecting acute stage infections. This study also describes the detection of B. gibsoni in tissue samples during chronic infections for the first time, suggesting possible sequestration of this parasite.

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.

PCR-RFLP for the detection and differentiation of the canine piroplasm species and its use with filter paper-based technologies

Canine piroplasmosis is an emerging disease worldwide, with multiple species of piroplasm now recognised to infect dogs. A nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was developed for the detection and differentiation of each of the piroplasm species currently known to infect dogs on the basis of the 18S ribosomal RNA gene. The assay can potentially amplify and discriminate between Theileria annae, Theileria equi, Babesia conradae, Babesia gibsoni, Babesia sp. (Coco) and each of the Babesia canis subspecies. Non-canine piroplasm species can also potentially be detected using the described assay, however amplification of Neospora caninum was also observed. The PCR was found to have a high detection limit, capable of detecting a 2.7x10(-7)% parasitaemia or the equivalent of 1.2 molecules of target DNA when using DNA extracted from whole EDTA blood and detected a parasitaemia of 2.7x10(-5)% using blood applied to both Flinders Technology Associates (FTA) cards and IsoCodetrade mark Stix. The application of blood samples to filter paper may greatly assist in piroplasm identification in regions of the world where local technologies for molecular characterisation are limited. The assay reported here has the potential to be standardised for routine screening of dogs for piroplasmosis.

Babesiaparasites develop and are transmitted by the non-vector soft tickOrnithodoros moubata(Acari: Argasidae)

Ornithodoros moubataticks were fed on blood infected withBabesia equi. However, the parasites were quickly cleared as evidenced by the disappearance ofB. equi-specific ribosomal RNA from the ticks. We hypothesized that if theBabesiaparasite can escape midgut-associated barriers a non-vector tick can become infected withBabesia. To test this hypothesis,B. equiparasite-infected blood fromin vitroculture was injected into the haemocoel of ticks.B. equi-specific rRNA was surprisingly detected 45 days after injection even in the eggs.Babesia-free dogs were infested withO. moubataticks that were infected by inoculation withB. gibsoni-infected red blood cells. Parasitaemia and antibody production against Bg-TRAP ofB. gibsoniincreased gradually. These results indicate thatO. moubatamay be a useful vector model forBabesiaparasites and also a very important tool for studies on tick immunity againstBabesiaparasites and tick-Babesiainteractions.

Characterization of the Babesia gibsoni P18 as a homologue of thrombospondin related adhesive protein☆

Thrombospondin related adhesive proteins (TRAPs) are well conserved among several apicomplexans. In this study, we reported the identification of the Babesia gibsoni P18, designated by our group previously, as a homologue of TRAP and renamed the P18 as the B. gibsoni TRAP (BgTRAP). The amino acid sequence of BgTRAP consists of several typical regions, including a signal peptide, a vonWillebrand factor A domain, a thrombospondin type 1 domain, a transmembrane region, and a cytoplasmic C-terminus. The B. gibsoni infected dog serum recognized recombinant BgTRAP expressed in E. coli by Western blotting. The antiserum against recombinant BgTRAP recognized an 80kDa protein in the lysate of infected erythrocytes (RBCs), which was detectable in the micronemal area of the parasites by confocal microscopic observation. The BgTRAP showed a bivalent cation-independent binding to canine RBC, and the specific antiserum was found to inhibit the growth of B. gibsoni in the infected severe combined immune deficiency mice given canine RBC. These results suggest that the BgTRAP is a new member of TRAP family identified from the merozoites of B. gibsoni and functionally important in merozoite invasion; this protein may be useful as a vaccine candidate against canine B. gibsoni infection.

A secreted cystatin from the tick Haemaphysalis longicornis and its distinct expression patterns in relation to innate immunity

Proteins capable of selective and specific inhibition of cysteine protease have been identified as cystatins and are isolated from a variety of microbes and tissues of animals and plants. The physiological function of these proteins has been proposed to be the regulation of protein turnover and defense against pathogens as well as the balance of the host-parasite immune relationship. Genes encoding cystatins have been found in several species of ticks, but the function of cystatin in ticks is not understood. We cloned a gene encoding cystatin from tick H. longicornis and designated it as Hlcyst-2 (H. longicornis cystatin-2). Its full-length cDNA is 569 bp, and it encodes a putative 133 amino acid protein with an obvious signal peptide. Sequence analysis demonstrated that it has significant homology with the known cystatin. The recombinant protein was expressed in a GST-fused soluble form in Escherichia coli and purified by affinity chromatography. The inhibitory activity of the recombinant protein against papain, cathepsin L, and cathepsin B was identified by fluorogenic substrate analysis. Cystatin was mostly expressed in the tick midgut and hemocyte. Blood feeding induced significantly increased expression in the midgut. Real-time PCR confirmed that LPS-injected adult ticks expressed Hlcyst-2 1.6 more times than the PBS-injected control; Babesia gibsoni-infected larvae ticks expressed Hlcyst-2 1.8 more times than normal larvae ticks. The recombinant protein also showed a significant growth-inhibitory effect on Babesia bovis cultured in vitro. These results indicated this cystatin Hlcyst-2 is involved in tick innate immunity.

Development of a polymerase chain reaction method for diagnosis of Babesia ovis infection in sheep and goats

In this study, a pair of oligonucleotide primers were designed according to the nucleotide sequence of the small subunit ribosomal RNA (ssu rRNA) gene of Babesia ovis isolated from sheep in eastern Turkey. The primers were used to detect parasite DNA from blood samples of B. ovis-infected sheep and goats by polymerase chain reaction (PCR). A 549-bp DNA fragment was specifically amplified from blood samples from sheep and goats, naturally infected with B. ovis. No PCR products resulted from Babesia motasi, T. ovis, Theileria sp. OT1, Theileria sp. OT3, T. lestoquardi, B. canis, B. microti,T. annulata or normal sheep leucocytes DNA using these specific primers. B. ovis-infected erythrocytes with 1% parasitemia were subjected to 10-fold serial dilutions (from 10(-1) to 10(-9)) using an uninfected sheep erythrocytes, and DNA was extracted from each diluted sample for testing the sensitivity of the PCR. The PCR was sensitive enough to detect parasite DNA from the dilution of 10(-5) with 0.00001% parasitemia. This is more sensitive than examining 200 fields under light microscopy. In addition, 98 field samples collected from small ruminanats in eastern Turkey were tested for B. ovis infection. Four samples were positive Babesia spp. in blood smears, 21 samples were positive for B. ovis DNA by PCR. These results indicate that the PCR provides a useful diagnostic tool for the detection of B. ovis infection in sheep and goats.

Fatal experimental transplacental Babesia gibsoni infections in dogs

A Babesia gibsoni infected bitch was mated with an uninfected dog in order to determine whether this parasite could be vertically transmitted. The bitch delivered a litter of four live and one stillborn pup. The four pups died from congenital babesiosis between 14 and 39 days post-birth. Babesia gibsoni DNA was detected in tissue from all five pups. These results show that vertical transmission occurred by the uterine route and not via the transmammary route. This is the first confirmed report of transplacental Babesia infection in any animal species.

Efficacy of atovaquone against Babesia gibsoni in vivo and in vitro

The therapeutic efficacy of atovaquone against Babesia gibsoni was examined in three dogs experimentally infected with B. gibsoni isolated from naturally infected dogs in Aomori Prefecture, Japan. Once parasitemia reached 10%, atovaquone was administered orally (30 mg/kg twice daily for 7 days). Within 2 days of atovaquone treatment, the parasite disappeared from blood smears without any clinical side effects. Anemia and thrombocytopenia were significantly improved in all the dogs. However, a polymerase chain reaction assay revealed that a B. gibsoni marker gene was intermittently present in peripheral blood after atovaquone therapy, indicating that the organism had not been eliminated, and parasites reappeared in blood smears 33 days after the last treatment. To investigate the change in sensitivity against atovaquone, an in vitro sensitivity test was performed using peripheral blood obtained from an untreated dog that was infected with the original parasite isolate, and from two of the experimentally infected and atovaquone-treated animals (blood was collected at the time of the post-treatment recurrence of the B. gibsoni infection). Atovaquone was added to the culture medium to final concentrations of 0.1, 1, 10, 100, and 1000 nM. For the untreated parasites, complete growth inhibition occurred at 1000 nM of atovaquone, whereas the recurrent parasites were inhibited by only 39.52 +/- 8.34% and 31.31 +/- 8.14% at this concentration after 48 h of incubation. Thus, the recurring parasites were less sensitive to atovaquone than the untreated originally isolated parasites.

Incidence of canine Babesia gibsoni infection and subclinical infection among Tosa dogs in Aomori Prefecture, Japan

To identify the incidence of Babesia gibsoni (B. gibsoni) in Aomori Prefecture, northeastern Japan, dogs with acute B. gibsoni infection were investigated at the Animal Teaching Hospital, Kitasato University, between April 2002 and March 2003. Eighteen dogs with acute B. gibsoni infection were recognized; they were all male dogs of the fighting dog breed Tosa. Their platelet counts were below normal and their packed cell volumes (PCVs) were at various levels. We collected blood samples from 141 Tosa dogs from Aomori Prefecture and used polymerase chain reaction assay to investigate the incidence of subclinical B. gibsoni infection. We also looked into the serological abnormalities associated with thrombocytopenia or anemia in subclinical infection. Forty-one of 87 dogs (47.1%) with histories of dog fighting, and one dog of 54 without a history of dog fighting were positive for B. gibsoni; that is, 42 of 141 dogs (29.8%) showed a positive result. The mean platelet counts of dogs with subclinical infection were significantly lower and levels of anti-platelet IgG were significantly higher than levels for dogs without infection. Anti-erythrocyte membrane IgG levels were significantly higher in dogs with subclinical infections, although mean PCVs were not significantly different. Tosa dogs from Aomori Prefecture, Japan, were highly infected with B. gibsoni subclinically and this pathogen might be successfully transmitted during dog fighting. Dogs with subclinical infections were at risk of chronic thrombocytopenia, which may be due to autoimmune mechanisms.