Adaptation of a chloroquine-resistant strain of Plasmodium vivax from Indonesia to New World monkeys

The spread of chloroquine-resistant Plasmodium vivax from Papua New Guinea and Indonesia poses a serious health threat to areas of Southeast Asia where this species of malaria parasite is endemic. A strain of P. vivax from Indonesia was adapted to develop in splenectomized Aotus lemurinus griseimembra, Aotus vociferans, Aotus nancymai, and Saimiri boliviensis monkeys. Transmission to splenectomized Saimiri monkeys was obtained via sporozoites. Chemotherapeutic studies indicated that the strain was resistant to chloroquine and amodiaquine while sensitive to mefloquine. Infections of chloroquine-resistant P.vivax in New World monkeys should be useful for the development of alternative treatments.

Serum concentrations of granulocyte-colony stimulating factor in complicated Plasmodium falciparum malaria

Involvement of neutrophils in the control of blood parasites in malaria has been reported. Both, mononuclear phagocytes and neutrophils are known to be stimulated by cytokines such as TNF-alpha in order to augment the defence potency against the parasites. Previously, it has been shown that serum-G-CSF concentrations are increased in patients with bacterial sepsis. In vitro studies have shown that P. falciparum - infected erythrocytes induce the release of G-CSF by several cells such as endothelial cells and monocytes, however, nothing is known about G-CSF serum concentrations during the clinical course of severe P. falciparum malaria. Thus, it was the aim of the present study to investigate the time course for G-CSF serum concentrations in patients with complicated P. falciparum malaria, and to correlate these values with other mediators of inflammation and hematopoesis. Twenty-six patients suffering from complicated P. falciparum malaria were included in the study, and 20, age and sex matched, healthy volunteers were used as the negative control group. Serum samples for determination of G-CSF were taken on day 0, 7 and 14, and measured by ELISA. We found significantly increased serum concentrations of G-CSF in patients with complicated P. falciparum malaria on day 0, values decreasing to within the normal range by day 7. A significant correlation was found between G-CSF (d0) and procalcitonin, the parasite count, erythropoietin and macrophage inflammatory protein, however no correlation could be shown for the neutrophil count. In conclusion, on the day of hospital admission, elevated serum concentrations of G-CSF were detected in patients with complicated P. falciparum malaria, which might indicate a role of G-CSF in the acute defence mechanism against the parasites.

Prevention and treatment of malaria in UK travellers

With around 2500 new cases of malaria being reported each year and more than a million UK residents visiting malaria endemic countries, there has never been a greater need for effective prevention and treatment. The latest information on malaria management is outlined below.

[RIII mefloquine resistance in children with falciparum malaria in Manaus, AM, Brazil]

We report the occurrence of resistance to mefloquine 20mg/day in 51 children with falciparum malaria treated, at reference center of Manaus, Brazil, from October to December 1997. All children were evaluated at day 3, 5, 7, 14, 21, 28 and 35 of treatment. Clinical and parasitological cure criteria were adopted. The incidence of RIII mefloquine resistance was 5.9% (IC 95% 1.5-17.2). The cure/resistance proportion was 20:1 and cure/severity was 62:1. These findings suggest the importance of mefloquine resistance within this group of children.

[Imported malaria in Emergency Department]

It occasionally happens that patients don't suspect to have malaria and diagnosis becomes difficult for the Emergency Department physicians. Since September 1995 to February 1999, 8 cases of malaria have been diagnosed in our first aid station; 5 occurred in european and 3 in extraeuropean immigrants. Incidence of imported malaria was greater after holiday period for european, and equally distributed along the year for immigrants. Patients' provenience was sub-Saharian Africa and Asia. Standard blood examination and thick and thin blood smears were performed showing P. falciparum and P. malariae infection. All patients were successfully treated with mefloquine as recommended. The aspecificity of the symptoms and signs makes diagnosis difficult if malaria is not suspected, in presence of fever in people returning from the tropics. Even in presence of symptoms and abnormal laboratory examinations, diagnosis is possible only with microscopic blood examination.

Neuropsychiatric problems in 2,500 long-term young travelers to the tropics

BACKGROUND

The prevalence and features of travel associated neuropsychiatric problems (NPP) and their relation to previous psychological consultations, antimalarials and recreational drug use have not been adequately studied.

METHODS

A two-phase postal and telephone survey has been conducted among 2,500 young travelers to tropical countries. We measured the rate and duration of NPP, characterized their features, and their association with previous psychological profiles, itinerary, type of travel, consumption of recreational drugs, and malaria prophylaxis.

RESULTS

First phase: Out of 1,340 respondents, 151 (11.3%) indicated that they had NPP during travel, in contrast with 2.3% who needed psychological consultation before travel (p<.001). Second phase: 117 of 151 responded to the study questionnaire. The mean age of the respondents was 24.4 years, 54.7% were female, and the mean stay abroad was 5.3 months. The most common NPP were sleeping disturbances (52.1%), fatigue (48.7%) and dizziness (39.3%). Thirty-three travelers (2.5%) had severe symptoms, and 16 (1.2%) had symptoms lasting more than 2 months. Seven travelers had pure or mixed depressive symptoms. Consumption of recreational drugs was admitted by 22.2%. Mefloquine was used significantly more often by those who suffered NPP, than by the entire cohort (98.2% vs. 70.7%; p<.001).

CONCLUSIONS

Long-term travel to the tropics was associated, in this cohort, with a considerable rate of neuropsychiatric symptoms. The majority of the responding travelers were females, used mefloquine as prophylaxis, and at least one fifth used recreational drugs.

Combination therapy for malaria in Africa: hype or hope?

The development of resistance to drugs poses one of the greatest threats to malaria control. In Africa, the efficacy of readily affordable antimalarial drugs is declining rapidly, while highly efficacious drugs tend to be too expensive. Cost-effective strategies are needed to extend the useful life spans of antimalarial drugs. Observations in South-East Asia on combination therapy with artemisinin derivatives and mefloquine indicate that the development of resistance to both components is slowed down. This suggests the possibility of a solution to the problem of drug resistance in Africa, where, however, there are major obstacles in the way of deploying combination therapy effectively. The rates of transmission are relatively high, a large proportion of asymptomatic infection occurs in semi-immune persons, the use of drugs is frequently inappropriate and ill-informed, there is a general lack of laboratory diagnoses, and public health systems in sub-Saharan Africa are generally weak. Furthermore, the cost of combination therapy is comparatively high. We review combination therapy as used in South-East Asia and outline the problems that have to be overcome in order to adopt it successfully in sub-Saharan Africa.

Plasmodium falciparum antimalarial drug susceptibility on the north-western border of Thailand during five years of extensive use of artesunate-mefloquine

Following a marked decline in the efficacy in vivo of mefloquine between 1990 and 1994, a combination of artesunate (4 mg/kg/d for 3 d) and mefloquine (25 mg/kg) has been used as first line treatment of uncomplicated falciparum malaria in camps for displaced persons located along the north-western border of Thailand. Antimalarial drug susceptibility of fresh isolates of Plasmodium falciparum from this population was evaluated using a radioisotope microdilution assay between 1995 and 1999. In total, 268 isolates were collected, of which 189 were from primary infections and 79 from recrudescent infections. The geometric mean 50% inhibitory concentration (IC50) values from primary infections were: dihydroartemisinin 1.2 ng/mL, artesunate 1.6 ng/mL, artemether 4.8 ng/mL, atovaquone 0.4 ng/mL, lumefantrine 32 ng/mL, chloroquine 149 ng/mL, quinine 354 ng/mL, mefloquine 27 ng/mL and halofantrine 4.1 ng/mL. A significant positive correlation was found between the susceptibility in vitro to artesunate and quinine (r = 0.43, P < 0.001), mefloquine (r = 0.46, P < 0.001), and halofantrine (r = 0.51, P < 0.001). These levels of resistance in vitro are among the highest reported and confirm continuing high level multidrug resistance in this area. Despite intensive use of the combination between 1995 and 1999 there has been a significant improvement in mefloquine sensitivity (P < 0.001) and artesunate sensitivity (P < 0.001). This supports observations in vivo that the combination of artesunate and mefloquine has reversed the previous decline in mefloquine sensitivity.

A case-control auditory evaluation of patients treated with artemisinin derivatives for multidrug-resistant Plasmodium falciparum malaria

The artemisinin derivatives are now used widely in areas with multidrug-resistant Plasmodium falciparum malaria such as Southeast Asia, but concerns remain over their potential for neurotoxicity. Mice, rats, dogs, and monkeys treated with high doses of intramuscular artemether or arteether develop an unusual pattern of focal damage to brain stem nuclei (particularly those involved in auditory processing). To investigate whether a similar toxic effect occurs in patients treated with these compounds, clinical neurologic evaluation, audiometry and early latency auditory evoked responses were measured in a single-blind comparison of 79 patients who had been treated with > or =2 courses of oral artemether or artesunate within the previous 3 years, and 79 age- and sex-matched controls living in a malaria-endemic area on the northwestern border of Thailand. There were no consistent differences in any of these test results between the cases and controls. This study failed to detect any evidence of significant neurotoxicity in patients treated previously with oral artemether or artesunate for acute malaria.

[Malaria in travelers returning to Israel from endemic areas: diagnosis of two patients in a family practice]

2 cases of malaria in family practice are described in a 26- and a 50-year-old woman. Both probably could have been prevented had common chemoprophylactic drugs been taken. The risk of malaria is greater than the risk of possible side-effects of the drugs commonly used by travelers for prevention. Family physicians must be aware of the possibility of malaria in young people with fever, especially those who have travelled to equatorial areas and special attention should be given to encourage chemoprophylaxis.

Primaquine as prophylaxis for malaria for nonimmune travelers: A comparison with mefloquine and doxycycline

Malaria prophylaxis for travelers is a controversial issue. The commonly used regimens are associated with side effects, low compliance, or low efficacy, which have raised concern regarding their use. In addition, they are inefficient against the tissue stage of the parasite and thus do not prevent relapses of Plasmodium vivax infection. Primaquine is aimed at the pre-erythrocytic stage and thus may be a potential causal-prophylactic treatment that can abolish the need for long postexposure therapy. During 1995-1998, we followed retrospectively travelers who joined rafting trips to an area in Ethiopia where both P. vivax and Plasmodium falciparum are hyperendemic. Of the 106 travelers who received primaquine, 5.7% developed malaria; of the 19 doxycycline recipients, 53% developed malaria; and of the 25 mefloquine recipients, 52% developed P. vivax malaria (>/=3 months after return from the area of endemicity). Primaquine was well tolerated, and only 1 withdrawal from therapy (due to gastrointestinal symptoms) was reported. Primaquine was shown to be a safe and effective prophylactic drug against both P. falciparum malaria and P. vivax malaria in travelers.

In vivo efficacy of mefloquine for the treatment of Falciparum malaria in Brazil

Ninety-four patients with falciparum malaria were treated with mefloquine (1000-mg single dose) and remained hospitalized in a malaria-free area for a minimum of 28 days. There was 1 parasitologic failure (grade I resistance [RI]) for a 99% cure rate (95% confidence interval, 94.2%-99.7%). Mean parasite clearance time by thick smear was 45.7 h (SD, 11.4 h). The subject in whom therapy failed had a parasite clearance time (71 h) >2 SD above the population mean. His plasma mefloquine level 48 h after administration was lower (578 ng/mL) than the range of levels from 8 randomly selected cured subjects (834-2360 ng/mL). The IC50 to mefloquine for the recrudescent strain of the RI failure was in the upper 90th percentile of IC50 values from 30 cured subjects. These results show a high mefloquine cure rate but document the onset and mechanism of the emergence of resistance.

Inoculum effect leads to overestimation of in vitro resistance for artemisinin derivatives and standard antimalarials: a Gambian field study

Artemisinin (QHS) and its derivatives are new antimalarials which are effective against Plasmodium falciparum parasites resistant to chloroquine (CQ). As these drugs are introduced it is imperative that resistance is monitored. In this paper we demonstrate that the inoculum size used in in vitro testing influences the measured in vitro susceptibility to QHS and its derivative dihydroartemisinin (DHA) and to mefloquine (MEF) and CQ over the range of parasitaemias routinely used in testing with the WHO in vitro microtest. An increase in parasitaemia and/or haematocrit was accompanied by a decrease in the measured sensitivity of 2 laboratory lines. In the context of a field study testing in vitro susceptibility of parasite isolates from patients with uncomplicated malaria in Fajara, The Gambia we demonstrate that failure to control for inoculum size significantly overestimates the level of resistance to QHS and DHA as well as MEF, halofantrine (HAL) and quinine (QUIN). When controlling for the inoculum effect, cross-resistance was observed between QHS, MEF and HAL suggesting the presence of a multidrug resistance-like mechanism. These studies underline the importance of inoculum size in in vitro susceptibility testing.

Automated exchange transfusion for life-threatening plasmodium falciparum malaria--lessons relating to prophylaxis and treatment

We report a case of traveller to Kenya who contracted severe plasmodium falciparum malaria complicated by disseminated intravascular coagulation and acute renal failure. She had taken no antimalarial prophylaxis in view of concerns in the media regarding the adverse effects of mefloquine. There was a protracted delay before the diagnosis of malaria was made. Clinical recovery occurred following treatment with intravenous quinine, haemofiltration and manual/automated red-cell exchange transfusions. Automated red-cell exchange transfusion resulted in a marked decrease in the parasitaemia, before a response to quinine therapy would have been anticipated, leading to a successful outcome thereafter. In conjunction with other groups we therefore feel that exchange transfusions should be considered in seriously ill patients with falciparum malaria, multiorgan complications and parasitaemias greater than 10%.

Analysis of mefloquine resistance and amplification of pfmdr1 in multidrug-resistant Plasmodium falciparum isolates from Thailand

Resistance to quinoline-containing compound has been associated with the Plasmodium falciparum multidrug resistance 1 (pfmdr1) gene. We analyzed wild P. falciparum isolates with high levels of chloroquine and mefloquine resistance for their macrorestriction maps of chromosome 5 and sequence of pfmdr1. Two types of chromosome 5 amplification were found. Eleven of 62 resistant isolates displayed Bgl 1 fragments larger than 100 kb. Twenty-nine isolates possessed multiple copies of the fragments. We failed to detect any amplification of this region on chromosome 5 in 22 mefloquine-resistant isolates, suggesting that other mechanisms can mediate the mefloquine-resistant phenotype. There was no direct association between pfmdr1 mutations and chloroquine sensitivity. Resistant lines could have Asn-86 and Tyr-184 or Phe-184, the predicted sequence of those chloroquine-sensitive isolates. No mutation at Asn-1042 and Asp-1246 was detected among these chloroquine-resistant isolates. Therefore, a few base substitutions in the pfmdr1 gene may not be sufficient to account for all chloroquine-resistant phenotypes.

Rapid absorption and clinical effectiveness of intragastric mefloquine in the treatment of cerebral malaria in African children

To obviate the lack of injectable quinine in a hospital in rural Burundi, mefloquine, only available as an oral formulation, was administered (25 mg/kg bodyweight) as a single dose by nasogastric tube to four small children with cerebral malaria. All patients recovered uneventfully after a mean coma duration of 20.5 h. Mefloquine was rapidly absorbed and therapeutic serum concentrations were achieved within a few hours in all subjects, with parasite reduction ratios after 48 h within the expected range for drug-sensitive parasites. These findings suggest that intragastric mefloquine deserves consideration whenever parenteral drugs are not available for the treatment of cerebral malaria.

[Acute paranoid hallucinatory psychosis following mefloquine prophylaxis (Lariam)]

Mefloquine is a drug of choice for malaria prophylaxis in Africa because of the spread of chloroquine resistant plasmodium falciparum. On the other hand there are some reports about severe neuropsychiatric side effects associated with the intake of mefloquine medication. In our paper we present a case-report of a patient suffering for the first time from an acute paranoid psychosis induced by mefloquine prophylaxis.

Mefloquine in the treatment of cutaneous leishmaniasis

Three cases of cutaneous leishmaniasis were treated orally with a mefloquine dose of 4.2 mg/kg/day for six days in the Teaching Hospital of the Faculdade de Medicina do Triângulo Mineiro, Uberaba, MG, Brazil. Three weeks later a new series was repeated. No patient was cured.

[Mefloquine in the treatment of cutaneous leishmaniasis in an endemic area of Leishmania (Viannia) braziliensis]

The aim of this study was to evaluate the efficacy of mefloquine in the treatment of skin leishmaniasis in patients infected with Leishmania (Viannia) braziliensis at an endemic region. Mefloquine is an oral drug effective against malaria with a prolonged half-life, less toxicity and easier administration than pentavalent antimonials. At Corte de Pedra in the Southern litoral of Bahia State, two randomized groups of ten patients with leishmaniasis were treated. The first group was treated with oral mefloquine, 250 mg per day in a single dose for six days and repeated three weeks later. The second group received meglumine antimoniate (Glucantime), 20 mg/kg daily administered intravenously for 20 days. Only one patient in the group treated with mefloquine showed evidence of clinical success. During treatment, one patient with four lesions developed a new lesion. The other three patients with clinical leismaniasis did not show evidence of clinical success after nine weeks of treatment. The group treated with Glucantime showed evident clinical improvement of the skin lesions.

Plasmodium chabaudi: effect of antimalarial drugs on gametocytogenesis

The proportion of asexual blood-stage malaria parasites that develop into transmission stages (gametocytes) can increase in response to stress. We investigated whether stress imposed by a variety of antimalarial drugs administered before or during infection increased gametocyte production (gametocytogenesis) in vivo in the rodent malaria parasite, Plasmodium chabaudi. All methods of drug treatment greatly reduced the numbers of asexual parasites produced during an infection but resulted in either no reduction in numbers of gametocytes or a smaller reduction than that experienced by asexuals. We used a simple model to estimate temporal variation in gametocyte production. Temporal patterns of gametocytogenesis did not greatly differ between untreated and prophylaxis infections, with rates of gametocytogenesis always increasing as the infection progressed. In contrast, administration of drugs 5 days after infection stimulated increased rates of gametocytogenesis early in the infection, resulting in earlier peak gametocyte densities relative to untreated infections. Given the correlation between gametocyte densities and infectivity to mosquito vectors, and the high frequency of subcurative drug therapy and prophylaxis in human populations, these data suggest that antimalarial drugs may frequently have only a small effect on reducing malaria transmission and may help to explain the rapid spread of drug-resistant geno-types.