Combination Of Atovaquone Research Articles

Inhibition of Wnt Signaling by Atovaquone Inhibits Gastric Cancer and Enhances Chemotherapy Effectiveness Through Activation of Casein Kinase 1α

Abnormal activation of the Wnt/β-catenin signaling pathway is a driving force behind the progression of gastric cancer. Atovaquone, known as an antimalarial drug, has emerged as a potential candidate for anti-cancer therapy. This study investigated atovaquone’s effects on gastric cancer and its underlying mechanisms. Using gastric cancer cell lines, we found that atovaquone, at concentrations relevant to clinical use, significantly reduced their viability. Notably, atovaquone exhibited a lower effectiveness in reducing the viability of normal gastric cells compared to gastric cancer cells. We further demonstrated that atovaquone inhibited gastric cancer growth and colony formation. Mechanism studies revealed that atovaquone inhibited mitochondrial respiration and induced oxidative stress. Experiments using ρ0 cells, deficient in mitochondrial respiration, indicated a slightly weaker effect of atovaquone on inducing apoptosis compared to wildtype cells. Atovaquone increased phosphorylated β-catenin at Ser45 and Ser33/37/Thr41, elevated Axin, and reduced β-catenin. The inhibitory effects of atovaquone on β-catenin were reversed upon depletion of CK1α. Furthermore, the combination of atovaquone with paclitaxel suppressed gastric cancer growth and improved overall survival in mice. Given that atovaquone is already approved for clinical use, these findings suggest its potential as a valuable addition to the drug arsenal available for treating gastric cancer.

Tafenoquine-Atovaquone Combination Achieves Radical Cure and Confers Sterile Immunity in Experimental Models of Human Babesiosis.

Human babesiosis is a potentially fatal tick-borne disease caused by intraerythrocytic Babesia parasites. The emergence of resistance to recommended therapies highlights the need for new and more effective treatments. Here we demonstrate that the 8-aminoquinoline antimalarial drug tafenoquine inhibits the growth of different Babesia species in vitro, is highly effective against Babesia microti and Babesia duncani in mice and protects animals from lethal infection caused by atovaquone-sensitive and -resistant B. duncani strains. We further show that a combination of tafenoquine and atovaquone achieves cure with no recrudescence in both models of human babesiosis. Interestingly, elimination of B. duncani infection in animals following drug treatment also confers immunity to subsequent challenge. Altogether, the data demonstrate superior efficacy of tafenoquine plus atovaquone combination over current therapies for the treatment of human babesiosis and highlight its potential in providing protective immunity against Babesia following parasite clearance.

Babesia negevi infection in dogs and response to treatment

Canine babesiosis is an important protozoan tick-borne disease associated with anemia and thrombocytopenia and caused by several different Babesia spp. Babesia negevi was first reported to infect dogs in the Middle East in 2020. This study describes the presentation, clinical signs, parasitemia levels quantified by molecular techniques, laboratory findings and treatment of dogs infected with B. negevi following the first description of this species. Clinical findings in the infected dogs, a 3-year old female and two 8-week old male and female pups, included extreme lethargy and pale mucous membranes, anemia and thrombocytopenia found in all three animals. Fever was present in the older female and icterus in the female pup. Babesia parasites resembling B. negevi were detected by microscopy of blood smears from the dogs. PCR of blood targeting the 18S rRNA and cox1 genes confirmed that babesiosis was caused by B. negevi and PCR targeting the Borrelia flagellin gene indicated co-infection with Borrelia persica in two dogs. Treatment of the dogs with imidocarb dipropionate resulted in clinical improvement and initial decrease in the B. negevi parasite load as detected by quantitative PCR in two dogs, however the female pup continued to deteriorate and died. The parasite load in the 3-year old female decreased from 43,451 parasites/µl blood pre-imidocarb dipropionate treatment to 803 parasites/µl within two weeks. In the surviving pup, it decreased from 3,293,538 parasites/µl pre-treatment to 20,092 parasites/µl after two weeks. Babesia negevi DNA was still recovered from blood samples by PCR despite repeated treatment with imidocarb dipropionate one-month post-treatment in the surviving pup and up to seven months post-treatment in the 3-year old female. Only treatment with atovaquone and azithromycin for ten days eliminated B. negevi in both dogs as confirmed by negative PCR two weeks later. In conclusion, treatment with imidocarb dipropionate was helpful for recovery from clinical disease but did not facilitate parasite elimination, and it is therefore recommended to treat canine B. negevi infection with the combination of atovaquone and azithromycin.

Case Report of a Fatal Babesia vulpes Infection in a Splenectomised Dog

Babesia vulpes is a small Babesia prevalent in foxes in Europe and mainly clinically affects dogs in north-western Spain. A dog imported from this region that had been living in Germany for three years developed splenic torsion. After splenectomy, the dog underwent immunosuppressive therapy because of autoimmune disease due to haemotrophic Mycoplasma sp. infection. As clinical signs worsened, small Babesia were detected in a blood smear and identified as B. vulpes by molecular analysis. Anaemia, thrombocytosis, elevated liver enzymes, and renal parameters were the most significant findings in blood analysis. The dog was treated with a combination of atovaquone (20 mg/kg BW, BID), proguanil hydrochloride (8 mg/kg BW, BID) and azithromycin (10 mg/kg BW, SID), which led to an increase in the cycle threshold in real-time PCR and the absence of B. vulpes in the blood smear. However, after clinical signs deteriorated, the dog was euthanised. This case report supports the recommendation to screen imported dogs for pathogens and highlights the impact of splenectomy on the course of infection.

The effect of atovaquone on the mitochondrial membrane potential of Babesiagibsoni

Atovaquone (ATV) has a growth inhibitory effect against Babesia gibsoni. The target site is considered mitochondria, as in the case of Plasmodium spp.; ATV would collapse the mitochondrial membrane potential. B. gibsoni has also reported that single nucleotide polymorphisms in cytochrome b of mitochondria are involved in ATV susceptibility. However, the details are still unknown. The study aim was to measure the mitochondrial membrane potential of B. gibsoni and evaluate the effect of ATV alone and combined with proguanil (PG) on the mitochondrial membrane potential. As a result of exposure of wild-type B. gibsoni to ATV alone, the number of cells with decreased mitochondrial membrane potential increased. When wild-type B. gibsoni was exposed to the ATV + PG combination, the peak value of mitochondrial membrane potential was larger than that when exposed to ATV alone. It was suggested that ATV alone affects the mitochondrial membrane potential of B. gibsoni, and the effect is enhanced by the combination of ATV and PG. The effect of ATV was weakened for B. gibsoni having reduced sensitivity to ATV (B. gibsoni with M121I), and the effect was not enhanced by the combination of ATV and PG. Although we still need to elucidate the mechanism of ATV and PG for B. gibsoni, these results strongly suggests that the target of ATV for B. gibsoni is also cytochrome b of mitochondria.

Histopathological and ultrastructural assessment of atovaquone-proguanil hydrochloride combination in chronic murine toxoplasmosis

ABSTRACT Over one billion people worldwide are expected to have Toxoplasma gondii infection with anonymous health problems. Available therapies are ineffective for persistent chronic toxoplasmosis. So, there is an imperative need for effective therapies to eliminate chronic tissue stage. In this study, we aimed to assess the effect of a drug combination of atovaquone and proguanil hydrochloride in the treatment of experimental chronic toxoplasmosis. Fifty Swiss Webster mice were used in the study. Forty mice were infected with Me49 type II cystogenic Toxoplasma gondii strain and allocated into four groups: infected untreated (vehicle-administered), infected and treated with cotrimoxazole (CTX) 370 mg/kg/day, infected and treated with atovaquone (ATV) 100 mg/kg/day, and infected and treated with atovaquone/proguanil (ATV/PROG) 50 mg/kg/day. An additional group of uninfected mice was used as an uninfected control group. Drug treatment was initiated 8 weeks post-infection and continued for two weeks. All mice were sacrificed 12 weeks post-infection. Parasitological and histopathological parameters were assessed. Toxoplasma gondii cysts recovered from brain tissue homogenates of both infected untreated and ATV/PROG-treated groups were examined by scanning electron microscopy. Combined ATV/PROG treatment demonstrated a significant reduction of Toxoplasma gondii cyst count in brain tissue (a reduction rate of 84.87%) compared to untreated group (P < .001). Brain tissues obtained from ATV/PROG treated group showed reduction of inflammatory infiltrate and marked attenuation and deformation of recovered Toxoplasma gondii cysts. We conclude that ATV/PROG drug combination could offer a potential drug therapy for Toxoplasma gondii chronic cystic stage.

In vivo efficacy of combination therapy with albendazole and atovaquone against primary hydatid cysts in mice

Alveolar echinococcosis (AE) is caused by the larval stage of Echinococcus multilocularis. Chemotherapy for AE involves albendazole (ABZ), which has shown insufficient efficacy. More effective chemotherapy for AE is needed. Previously, we have demonstrated that atovaquone (ATV), an antimalarial, inhibits mitochondrial complex III of E. multilocularis and restricts the development of larval cysts in in vivo experiments. Therefore, in this study, we evaluated the efficacy of ABZ and ATV combination therapy on E. multilocularis in culture and in vivo experiments. Protoscoleces were treated with 50 μM ABZ and/or ATV in the medium; the duration of parasite elimination was determined under aerobic and anaerobic culture. In the in vivo experiment, the effects of ABZ and ATV combination treatment in BALB/c mice infected orally with eggs from the feces of an adult-stage E. multilocularis-infected dog were compared with those of standard oral ABZ therapy. In the culture assay, the duration of elimination associated with ABZ and ATV combination treatment was shorter than that associated with ATV alone under aerobic conditions. Protoscolex viability progressively reduced owing to the combination treatment under anaerobic conditions; however, either drug used singly did not exhibit antiparasitic effects under hypoxia. Furthermore, compared with ABZ alone, the combination treatment significantly reduced the growth of the primary cyst in the liver of mice infected orally with parasite eggs (P = .011). ATV enhances the effect of ABZ in the treatment of AE in mice.

736. Babesia microti: A study of 38 cases

Background Babesia microti is an intraerythrocytic infection transmitted by Ixodes scapularis in Eastern United States. The same vector transmits Borrelia burgdorferi, Anaplasma phagocytophilum, B miyamotoi and Powassan virus resulting in mixed infections. Spleen involvement, blood abnormalities and abnormal liver functions are common in babesiosis. Here we present the clinical findings of 38 B microti (smear or serology positive) patients.MethodsWe retrospectively evaluated charts of 38 patients, 20 male and 18 female, smear or serology positive for B. microti in our health network from 9 hospitals in Eastern Pennsylvania and one in adjacent Warren county New Jersey.ResultsEleven had B microti and Lyme co-infections (9 western blot positive, 2 with erythema migrans) and 2 mixed infections with A. phagocytophilum (PCR+). Only 2 gave a history of a tick bite. Fourteen presented with fever. 9 were Babesia smear positive. All 9 smear positive patients had fever, 7 were anemic, 6 leukopenic and 8 had increased liver enzymes. Six out of 14 with fever and 6 out of 9 smear positive patients had low platelet counts. Two with left upper abdominal discomfort likely due to splenic inflammation were initially misdiagnosed as left pyelonephritis. One had splenomegaly. Both had anemia and thrombocytopenia. A patient with a low IGG titer 1:10 for B microti and chronic ITP with a platelet count 102,000 (NL 140-200,000) had a 1 cm splenic artery aneurysm. Four western blot negative patients 2 with joint pain and 2 with radiculopathy were not counted as mixed infections. A Lyme co-infected patient had sinus tachycardia and ST, T changes in the electrocardiogram suggestive of Lyme myocarditis. All mixed infections were treated with a combination of atovaquone, azithromycin and doxycycline, including one patient initially on quinine and clindamycin switched due to side effects.Conclusion I.scapularis transmitted mixed infections are not uncommon. The majority were due to B microti and B burgdorferi. Fever was the most common presentation in symptomatic patients. Anemia, leukopenia, thrombocytopenia and elevated liver enzymes were common in smear positive patents. Babesiosis should be suspected in patients presenting with left upper abdominal pain in tick endemic areas. Most did not give a history of a tick bite.Disclosures All Authors: No reported disclosures

The first report of atovaquone/proguanil-induced vanishing bile duct syndrome: Case report and mini-review.

The combination of Atovaquone and Proguanil (Malarone™) has been widely used for treatment and prevention of Plasmodium falciparum malaria. Transient elevation of liver enzymes is a recognized side effect of the medication. The association of Vanishing bile duct syndrome (VBDS) with the use of Atovaqoune/Proguanil was not previously reported. We describe a case of a 62-year-old male with no history of liver disease who presented with painless jaundice after receiving malaria prophylaxis with Atovaquone-proguanil for 25 days. The patient developed severe hepatitis with Vanishing bile duct syndrome. This case highlights a serious side effect of a usually well-tolerated medication.

Inhibition of mitochondrial respiration overcomes hepatocellular carcinoma chemoresistance

The clinical management of advanced hepatocellular carcinoma (HCC) is challenging due to its resistance to chemotherapy. In our work, we demonstrate that an antiparasitic drug atovaquone at clinically relevant concentrations is active against chemoresistant HCC. We show that atovaquone inhibits proliferation and induces apoptosis in not only HCC parental cells but also cells exposed to long time culture of chemotherapeutic agents. Consistently, the combination of atovaquone with cisplatin or doxorubicin achieved remarkably greater efficacy than single drug alone. Mechanistically, atovaquone overcomes HCC chemoresistance via supressing mitochondrial respiration and inducing oxidative stress. Atovaquone but not cisplatin or doxorubicin is ineffective in mitochondrial respiration-deficient ρ0, confirming mitochondria as a specific upstream target of atovaquone. Interestingly, we show that prolonged exposure of HCC cells to chemotherapeutic agents induces higher level of mitochondrial respiration, suggesting that tumors which develop chemoresistance after chemotherapy might be more dependent on mitochondrial respiration than primary tumors and explaining the sensitivity of chemoresistant HCC cells to atovaquone. We further show that atovaquone at tolerable does significantly inhibits chemoresistant HCC growth in mice throughout the duration of treatment. In line with in vitro data, we observe the increased oxidative stress in atovaquone-treated tumors. Our findings highlight the dependency of chemoresistant HCC on mitochondrial respiration and demonstrate that atovaquone is a potential drug to overcome HCC chemoresistance.

421. Babesiosis: Retrospective Review of 38 Cases from Upper Midwest

BackgroundBabesiosis is a tick-borne illness caused by protozoal infection of the genus Babesia. Clinical presentation varies widely from asymptomatic to rapidly fatal infection and diagnosis requires a high index of clinical suspicion. It is an emerging health risk and clinicians need to be aware of its different clinical manifestations.MethodsWe retrospectively collected and analyzed data from 38 patients with babesiosis from 1990 to 2015.ResultsMean age of patients was 63 years. 68% of patients required hospitalization with 21% requiring intensive care unit (ICU) stay. Mean length of illness before diagnosis was 15.6 days and symptoms comprised of malaise (82%), subjective fever (71%), chills (55%), anorexia (29%), arthralgia (29%), and nausea (16%). Only 47% of the patients recalled tick bites. Mean hemoglobin in the outpatients was 12.4 g/dL compared with 9.8 g/dL in the hospitalized patients (P < 0.01). Among hospitalized patients, mean hemoglobin for ICU admissions was 7.5 g/dL vs. 10.9 g/dL (P < 0.01) for those without ICU stay. Mean parasitemia was 10.1% in those requiring ICU compared with 1.4% in those admitted to the medical floor (P < 0.01). 28.9% had Lyme disease, and 10.5% had anaplasma coinfection. Co-morbidities included diabetes mellitus (n = 3), asplenia (n = 5), and immunosuppression (n = 3). Diagnosis was made with PCR and peripheral smear in 50% of patient whereas 50% were diagnosed with PCR alone. In 27% of patients with positive PCR, peripheral smear was negative. All patients with asplenia required hospitalization with 3/5 requiring ICU with initial parasitemia ranging from 2.5 to 28% and duration of parasitemia ranging from 10 to 142 days. Initial treatment comprised of clindamycin plus quinine in 31% of patients whereas combination of atovaquone and azithromycin was used in 69% of patients. Median duration of treatment was 10 days. Overall three patients underwent exchange transfusion with parasitemias ranging from 12.3 to 28.5%. None of the patients died during hospitalization.ConclusionLess than half of the patients with babesiosis recall tick bites. There is usually a delay in diagnosis of up to 2 weeks due to nonspecific nature of symptoms. In more than one-fourth of patients with babesiosis peripheral smear may be falsely negative. Hemoglobin and percentage parasitemia seemed to correlate with severity of illness.Disclosures All authors: No reported disclosures.

Phenotypic and genotypic characterization of Thai isolates of Plasmodium falciparum after an artemisinin resistance containment project

BackgroundIn Thailand, artemisinin-based combination therapy (ACT) has been used to treat uncomplicated falciparum malaria since 1995. Unfortunately, artemisinin resistance has been reported from Thailand and other Southeast Asian countries since 2003. Malarone®, a combination of atovaquone–proguanil (ATQ–PG), has been used to cease artemisinin pressure in some areas along Thai–Cambodia border, as part of an artemisinin resistance containment project since 2009. This study aimed to determine genotypes and phenotypes of Plasmodium falciparum isolates collected from the Thai–Cambodia border after the artemisinin resistance containment project compared with those collected before.ResultsOne hundred and nine of P. falciparum isolates collected from Thai–Cambodia border from Chanthaburi and Trat provinces during 1988–2016 were used in this study. Of these, 58 isolates were collected after the containment. These parasite isolates were characterized for in vitro antimalarial sensitivities including chloroquine (CQ), quinine (QN), mefloquine (MQ), piperaquine (PPQ), artesunate (AS), dihydroartemisinin (DHA), ATQ and PG and genetic markers for drug resistance including the Kelch13 (k13), Plasmodium falciparum chloroquine resistance transporter (pfcrt), P. falciparum multidrug resistance 1 (pfmdr1) and cytochrome b (cytb) genes. Mean CQ, QN, MQ, PPQ and AS IC50s of the parasite isolates collected from 2009 to 2016 exhibited significantly higher than those of parasites collected before 2009. Approximately 57% exhibited in vitro MQ resistance. Approximately 94% of the isolates collected from 2009 to 2016 contained the pfmdr1 184F allele. Mutations of the k13 gene were detected in approximately 90% of the parasites collected from 2009 to 2016 which were significantly higher than the parasite isolates collected before. No ATQ-resistant genotype and phenotype of P. falciparum were found among the isolates collected after the containment project.ConclusionsAlthough the containment project had been implemented in this area, the expansion of artemisinin-resistant parasites did not decline. In addition, reduced sensitivity of the partner drugs of ACT including MQ and PPQ were identified.

Bridging Strategies for Drug Combinations in Pediatric Indications

Concurrent prescription of different drugs is common and is often necessary in many pediatric indications. A randomized concentration-controlled trial (RCCT) is proposed for pediatric studies in which drug combinations are used. The aim of our investigation was to show the relevance of flexible designs for accurate dose selection in such cases. We used the combination of atovaquone (ATV) and proguanil (PGN) as a paradigm to illustrate our approach. Pharmacokinetic models were developed for ATV and PGN using data pertaining to adults. The median area under the curve (AUC) in adults was considered the target exposure for bridging purposes. A pediatric population was simulated according to scenarios in which clearance varied from 20 to 100% of the reference adult values or allometrically correlated with body weight (BW). Doses were subsequently adapted according to the individual AUC estimates. Our results show that adaptive protocols are critical for accurate dose selection when evaluating drug combinations in children, ensuring that target exposure is achieved with respect to both active moieties in each individual patient.

Dosing Rationale for Fixed-Dose Combinations in Children: Shooting From the Hip?

In this investigation we evaluate the relevance of a model-based approach for pharmacokinetic (PK) bridging and dose selection of drug combinations in children. The fixed-dose combination of atovaquone (ATV) and proguanil (PGN) was used for illustration purposes. A population PK model was developed for each compound using plasma concentration data from adult and pediatric patients. PK parameter estimates were subsequently used to simulate drug exposure in children treated with different dose levels of these drugs. We show that, contrary to common practice, different dose ratios may be required across age groups in order to achieve target exposure levels comparable to adults. This example illustrates the effects of covariate interactions, specifically the ones involving body weight (BW) and ethnicity, on the PK of drugs. A model-based approach is critical for dose selection and the rational use of drug combinations in children. Flexible rather than fixed-dose ratios may be needed to ensure comparable target exposure in bridging studies.

Severe hypersensitivity reaction as acute eosinophilic pneumonia and skin eruption induced by proguanil

To the Editors: The combination of atovaquone and proguanil is effective and safe in the prevention and treatment of malaria. We present the first report of proguanil-induced acute eosinophilic pneumonia (AEP) associated with skin eruption. On December 18, 2006, a 40-yr-old female was admitted to our hospital (Victor Provo Medical Centre, Roubaix, France) for shortness of breath and widespread skin lesions. She had a 10-pack-yr smoking history but no respiratory illness or relevant comorbidity. On the morning of December 8, 2006, she had initiated atovaquone–proguanil treatment for malaria prophylaxis prior to a trip to Senegal. She had taken the same treatment for the first time 1 yr previously without any complications. That evening she developed progressive dyspnoea with nonproductive cough and subacute fever (38°C). She only stayed in Senegal for 4 days and did not leave her hotel room during this time. After returning to France she continued to take atovaquone–proguanil for 1 week. Increased shortness of breath prompted her to consult her general practitioner, who prescribed amoxicillin plus clavulanic acid for bronchitis. This treatment was withdrawn on the day 4 because of rapidly spreading skin eruptions on day 3. Although …

Efficacy of Atovaquone and Azithromycin or Imidocarb Dipropionate in Cats with Acute Cytauxzoonosis

Imidocarb or a combination of atovaquone and azithromycin (A&A) has been suggested for treatment of cats with cytauxzoonosis, but neither has been prospectively evaluated for efficacy. That survival to hospital discharge is improved by treatment with A&A as compared with imidocarb. Eighty acutely ill cats with Cytauxzoon felis infection treated at one of 18 veterinary clinics in 5 states. An open-label, randomized prospective study compared survival in cats treated with atovaquone (15 mg/kg p.o. q8h) and azithromycin (10 mg/kg p.o. q24h) or imidocarb (3.5 mg/kg i.m.). All received heparin, fluids, and supportive care. Clinical and clinicopathologic data from initial presentation were collated. Parasitemia was quantified (n = 79) and pathogens genotyped (n = 60). Logistic regression was used to determine the impact of treatment group on the primary endpoint, survival to hospital discharge or death. Covariants were analyzed by rank-sum testing. Of 53 cats treated with A&A, 32 (60%) survived to discharge while only 7 of 27 cats (26%) treated with imidocarb survived (P = .0036; odds ratio 7.2, 95% CI 2.2, 24). Cats with a lower parasitemia were more likely to survive, as were cats with higher white blood cell counts and lower total bilirubin. Unique pathogen genotypes were identified from 15 cats, while genotype isolated from 21 cats had been described previously. There were multiple pathogen genotypes identified in 24 cats. Survival to discharge was more likely in cats treated with A&A as compared with imidocarb, although case fatality rate remained high.

Possible Emergence of Drug‐Resistant Variants of Babesia gibsoni in Clinical Cases Treated with Atovaquone and Azithromycin

There is no well-established treatment strategy for Babesia gibsoni infection. A new therapeutic protocol using atovaquone (ATV) and azithromycin (AZM) has been proposed, but there is concern about the possible induction of relapse and the emergence of ATV-resistant variants after treatment. To evaluate the clinical use of combination therapy with ATV and AZM as a first-line treatment of clinical B. gibsoni infection in dogs, and to investigate the emergence of ATV-resistant variants. Eight B. gibsoni naturally infected dogs showing signs of acute onset of disease. Retrospective case study. Eight clinical cases received combination therapy with ATV and AZM at Kagoshima University Veterinary Teaching Hospital during 2007-2008, and their clinical courses and clinicopathological parameters were evaluated. In addition, alterations in the cytochrome b (CYTb) gene of B. gibsoni were analyzed by polymerase chain reaction and DNA sequencing techniques. All of the dogs responded well to the treatment, with rapid improvement in their clinical condition and hematological parameters. However, 5 of the 8 dogs relapsed after treatment. Analysis of the CYTb gene strongly suggested the emergence of ATV-resistant variants after treatment. The combination of ATV and AZM can be used as a first-line treatment for dogs with babesiosis, but relapses occur. Attention should be paid to the possible in vivo selection of drug-resistant variants.

Analyses of cytochrome b mutations in Plasmodium falciparum isolates in Thai-Myanmar border, 2002–2005

The combination of atovaquone and proguanil (Malarone™, GlaxoSmithKline) has been established as an effective drug of choice not only for treatment but also for prophylaxis of multi-drug resistant Plasmodium falciparum malaria in travellers. However, several cases of resistance against Malarone™ have already been reported in some parts of Africa, and many of the cases are associated with mutations at codon 268 of cytochrome b gene in mitochondrial genome of P. falciparum. On the contrary, in Asian countries, only limited numbers of clinical failures with the drug has so far been reported, and no mutations could be found at the codon 268. To maintain the usefulness of Malarone™ in travel medicine, monitoring of the effectiveness of the drug is needed. In this study, mutations of atovaquone binding site on the cytochrome b were investigated by PCR amplification and sequencing of the gene (1131 bp length) in the parasites from patients at the Hospital for Tropical Diseases Mahidol University in Bangkok, Thailand, in 2002 through 2005. Twenty-five blood samples were from complicated falciparum malaria patients and another 25 were from non-complicated falciparum patients who were infected in multi-drug resistant areas in Thai-Myanmar border. Forty-seven out of 50 samples were successfully analyzed, and no mutation was observed in putative ubiquinol (Q0) binding site 1 and 2. In fact, they showed identically conserved nucleotide sequences, as was reported by our previous study conducted in the same area in 1999. We may conclude from these findings that Malarone™ is still effective and recommended for treatment and prophylaxis for travellers to Mekong region.

Treatment of Malaria in the United States

Many US clinicians and laboratory personnel are unfamiliar with the diagnosis and treatment of malaria. To examine the evidence base for management of uncomplicated and severe malaria and to provide clinicians with practical recommendations for the diagnosis and treatment of malaria in the United States. Systematic MEDLINE search from 1966 to 2006 using the search term malaria (with the subheadings congenital, diagnosis, drug therapy, epidemiology, and therapy). Additional references were obtained from searching the bibliographies of pertinent articles and by reviewing articles suggested by experts in the treatment of malaria in North America. Important measures to reduce morbidity and mortality from malaria in the United States include the following: obtaining a travel history, considering malaria in the differential diagnosis of fever based on the travel history, and prompt and accurate diagnosis and treatment. Chloroquine remains the treatment of choice for Plasmodium falciparum acquired in areas without chloroquine-resistant strains. In areas with chloroquine resistance, a combination of atovaquone and proguanil or quinine plus tetracycline or doxycycline or clindamycin are the best treatment options. Chloroquine remains the treatment of choice for all other malaria species, with the exception of P vivax acquired in Indonesia or Papua New Guinea, in which case atovaquone-proguanil is best, with mefloquine or quinine plus tetracycline or doxycycline as alternatives. Quinidine is currently the recommended treatment for severe malaria in the United States because the artemisinins are not yet available. Severe malaria occurs when a patient with asexual malaria parasitemia, and no other confirmed cause of symptoms, has 1 or more designated clinical or laboratory findings. The only adjunctive measure recommended in severe malaria is exchange transfusion. Malaria remains a diagnostic and treatment challenge for US clinicians as increasing numbers of persons travel to and emigrate from malarious areas. A strong evidence base exists to help clinicians rapidly initiate appropriate therapy and minimize the major mortality and morbidity burdens caused by this disease.

Analyses of cytochrome b mutations in Plasmodium falciparum isolates in Thai-Myanmar border

The combination of atovaquone and proguanil (Malarone) has been established as a drug of choice to prevent and treat multi-drug resistant Plasmodium (P.) falciparum malaria in travelers. However, several cases of resistance against Malarone have been reported in some parts of Africa, and many of the cases are believed to be associated with mutations at the codon 268 of cytochrome b gene in mitochondria of P. falciparum. The aim of the study was to estimate the effectiveness of Malarone in treatment and prophylaxis for the travelers to Thai-Myanmar border where multi-drug resistant malaria is highly endemic. Seventy P. falciparum samples obtained from patients from Thai-Myanmar border were sequenced to detect mutations around the codon 268. The same samples were also sequenced to detect P. falciparum chloroquine resistance transporter mutation (PfCRT K76T). All the 70 samples showed no mutations at the codon 268 of cytochrome b gene. Whereas, 50 samples, whose pfcrt genes were sequenced successfully, had an identical genotype for K76T mutation. In Asian countries, even in the multi-drug resistant areas in the great Mekong region, no case of Malarone resistance has been reported clinically or genetically thus far. In this study, all the P. falciparum parasites tested successfully were shown to be chloroquine resistant but atovaquone susceptible genetically. The more the usefulness of Malarone increases for both treatment and prophylaxis, the wider the drug-resistance against Malarone may spread in the region. Although the total number of samples examined is not large, it is concluded from these findings that Malarone should be recommended for prophylaxis of malaria for travelers to the Mekong region.