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

Analysis of Genetic Diversity of cytb gene from Babesia gibsoni Isolates from Naturally Infected Dogs in Karnataka, India

PURPOSE

The study aimed to investigate genetic diversity in Babesia gibsoni, the causative agent of canine babesiosis, and to assess the presence of atovaquone-resistant isolates in naturally infected dogs.

METHODS

A total of 24 blood samples confirmed for B. gibsoni infection was subjected to PCR amplification and sequencing based on cytb gene. Genetic characterization of B. gibsoni as well as attempts to detect the point mutation rendering atovaquone resistance was carried out based on the analysis of nucleotide sequence of cytb gene using bioinformatics software.

RESULTS

The findings indicated that the B. gibsoni isolates in the investigation exhibited a high nucleotide identity with the Asian genotype, ranging from 98.41 to 98.69%. Notably, none of the isolates carried cytb gene variants associated with atovaquone resistance. Phylogenetic analysis revealed clustering of most isolates with those from Japan and China, except for one isolate forming a distinct subclade. Haplotype network analysis indicated a high diversity with 22 distinct haplotypes among the B. gibsoni isolates, emphasizing the genetic variability within the studied population.

CONCLUSION

In conclusion, the cytb gene exhibited remarkable conservation among the twenty-four B. gibsoni isolates studied and the study represents the first genetic diversity assessment of B. gibsoni using the cytb gene in dogs from India. These findings shed light on the genetic characteristics of B. gibsoni in the region and provide valuable insight for addressing the challenges posed by this life-threatening disease in dogs.

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.

An alternative combination therapy with metronidazole, clindamycin and doxycycline for Babesia gibsoni (Asian genotype) in dogs in Hong Kong

Babesia spp. are globally distributed hemoparasites that cause disease in many mammalian species. The species Babesia gibsoni (Asian genotype) is prevalent and endemic in many Asian countries but has also been reported in growing numbers in countries outside of Asia. Standard therapies for the treatment of B. gibsoni often fail to result in consistent and successful clearance of the organism. This study evaluated the use of a combination of three antibiotics: metronidazole, clindamycin and doxycycline after atovaquone and azithromycin failed to eliminate the infection on a polymerase chain reaction (PCR) test. The aim of this study was to determine whether the triple antibiotic combination was an appropriate alternative or additional treatment for the elimination of B. gibsoni. The medical records of 24 patients treated from December 2012 to July 2015 were retrospectively analyzed. The diagnosis of B. gibsoni was confirmed with a PCR test that was also used to assess treatment response. All patients were initially treated with the standard therapy, atovaquone and azithromycin with a 25% success rate clearing B. gibsoni. Dogs that remained positive on PCR using the standard therapy were then treated with the triple antibiotic protocol achieving an 87% success rate. The inclusion of an alternative and potentially effective protocol for the treatment of B. gibsoni would increase the options for the current therapeutic options, could aid in clearance of the organism and offer a more affordable option for clients.

Babesia gibsoni cytochrome b mutations in canine blood samples submitted to a US veterinary diagnostic laboratory

BACKGROUND

Babesiosis caused by Babesia gibsoni is recognized throughout the world and can be difficult to treat. Resistance to atovaquone is associated with mutations in the B. gibsoni mitochondrial genome, specifically the M128 position of cytochrome b (cytb). The prevalence of cytb mutations in North America has not been reported.

HYPOTHESIS/OBJECTIVES

The objective of our study was to describe the prevalence of cytb M128 mutations in B. gibsoni in canine blood samples submitted to a US veterinary diagnostic laboratory. A secondary objective was to determine whether or not some dogs had wild-type cytb in our initial samples then had M128 mutations detected in follow-up samples.

ANIMALS

One-Hundred seventy-four dogs that tested positive for the presence of B. gibsoni between 2012 and 2017.

METHODS

Case series of consecutive samples submitted to a veterinary diagnostic laboratory. Partial B. gibsoni cytb genes were amplified by polymerase chain reaction and screened for the presence of mutations at the M128 position.

RESULTS

The overall prevalence of M128 mutants was 3.5% (6/173 dogs) in the initial samples. The incidence of new cytb mutants in dogs that tested positive for B. gibsoni, which then had follow-up testing, was 12.1% (5/41). Conclusions and Clinic Importance: Our study reaffirms that B. gibsoni infection is widespread and most commonly detected in American Staffordshire Terrier/American Pit Bull Terrier dogs (128/174, 74% of the infected dogs in our study). The prevalence of cytb mutations does not warrant pretreatment genotyping.

Efficacy of Azithromycin and Compounded Atovaquone for Treatment of Babesia gibsoni in Dogs

Background

Approximately one‐third of dogs confiscated during dogfighting investigations are infected with Babesia gibsoni. Traditional management of B. gibsoni with polymerase chain reaction (PCR)‐screening, treatment with commercially available azithromycin and atovaquone, and PCR testing after 60 and 90 days is costly and impractical for large numbers of dogs at a time.

Hypothesis/Objectives

To assess the efficacy of an alternative protocol in which commercial atovaquone was replaced by compounded medication and PCR monitoring was initiated at 30 days after the end of treatment to decrease the total management time.

Methods

Prospective observational study. Forty‐two pit bull‐type dogs confiscated as part of an investigation of dogfighting, diagnosed with B. gibsoni infection, and judged to be suitable for adoption were treated with azithromycin (10 mg/kg PO q24h) and compounded atovaquone (13.4 mg/kg PO q8h with a fatty meal) for 10 days. PCR testing was repeated at 30 and 60 days after end of treatment if dogs with positive PCR tests at either time were tested at 90 days. Treatment was considered successful; 2 PCR tests 30 days apart were negative.

Results

Treatment was successful in 39 dogs (93%) as defined by 2 consecutive PCR‐negative test results 30 days apart. In 38 dogs (90%), PCR results were the same at 30 and 60 days.

Conclusions and Clinical Importance

Use of compounded atovaquone and a reduced monitoring period can reduce costs and holding times without compromising treatment efficacy. This more economical protocol can remove barriers to mass screening and management of B. gibsoni infections in dogfighting cases.