Resistance of P. falciparum to chloroquine in Africa: true or false?

In-Vivo Efficacy of Chloroquine to Clear Asymptomatic Infections in Mozambican Adults: A Randomized, Placebo-controlled Trial with Implications for Elimination Strategies

Recent reports regarding the re-emergence of parasite sensitivity to chloroquine call for a new consideration of this drug as an interesting complementary tool in malaria elimination efforts, given its good safety profile and long half-life. A randomized (2:1), single-blind, placebo-controlled trial was conducted in Manhiça, Mozambique, to assess the in-vivo efficacy of chloroquine to clear plasmodium falciparum (Pf) asymptomatic infections. Primary study endpoint was the rate of adequate and parasitological response (ACPR) to therapy on day 28 (PCR-corrected). Day 0 isolates were analyzed to assess the presence of the PfCRT-76T CQ resistance marker. A total of 52 and 27 male adults were included in the CQ and Placebo group respectively. PCR-corrected ACPR was significantly higher in the CQ arm 89.4% (95%CI 80–98%) compared to the placebo (p < 0.001). CQ cleared 49/50 infections within the first 72 h while placebo cleared 12/26 (LRT p < 0.001). The PfCRT-76T mutation was present only in one out of 108 (0.9%) samples at baseline, well below the 84% prevalence found in 1999 in the same area. This study presents preliminary evidence of a return of chloroquine sensitivity in Mozambican Pf isolates, and calls for its further evaluation in community-based malaria elimination efforts, in combination with other effective anti-malarials. Trial registration: www.clinicalTrials.gov NCT02698748.

Plasmodium falciparum drug resistance in Angola

Facing chloroquine drug resistance, Angola promptly adopted artemisinin-based combination therapy as the first-line to treat malaria. Currently, the country aims to consolidate malaria control, while preparing for the elimination of the disease, along with others African countries in the region. However, the remarkable capacity of Plasmodium to develop drug resistance represents an alarming threat for those achievements. Herein, the available, but relatively scarce and dispersed, information on malaria drug resistance in Angola, is reviewed and discussed. The review aims to inform but also to encourage future research studies that monitor and update the information on anti-malarial drug efficacy and prevalence of molecular markers of drug resistance, key fields in the context and objectives of elimination.

In vivo and in vitro assessment of the sensitivity of Plasmodium falciparum to chloroquine in four districts of Tanga region, Tanzania

The sensitivity of Plasmodium falciparum to chloroquine was tested in Muheza, Pangani, Tanga and Korogwe districts in north-eastern Tanzania by applying both in vivo and in vitro tests in schoolchildren. A total dose of 25 mg chloroquine base/kg body-weight given over a period of three days (10 mg/kg on days 0 and one; and 5 mg/kg on day 2) failed to clear asexual parasites from the peripheral blood by day 7 in 12.5% of the children tested at Muheza, 5.9% at Pangani, 31.8% at Tanga, and 39.5% at Korogwe. In vitro micro tests were successfully carried out on 44 isolates at Muheza, 29 isolates at Pangani, 45 isolates at Tanga and 44 isolates at Korogwe. Schizont maturation at chloroquine concentrations of 1.14 mu mol/litre of blood and above, an indication of drug resistance, was observed in 20.5% of the isolates at Muheza, 41.4% at Pangani, 51.1% at Tanga and 45.5% at Korogwe. In vivo and in vitro results of the tests for resistance have been compared.

Serum concentrations of chloroquine in a patient with a late recrudescence of Kenyan Plasmodium falciparum malaria

A Swedish tourist who had visited Kenya fell ill with Plasmodium falciparum malaria 11 days after returning home, in spite of taking pyrimethamine (50 mg weekly) as malaria prophylaxis. Chloroquine treatment (25 mg base/kg body-weight) giving serum concentrations of 0.30 mumol/l cleared the patent parasitaemia and the patient recovered. Recrudescence occurred, however, within 42 days. A second chloroquine course (30 mg base/kg) gave serum levels up to 1.28 mumol/l. The patient improved rapidly and remained healthy during 28 days without renewed parasitaemia. Further follow-up for 10 months was uneventful. We consider it urgent to assess chloroquine concentrations in serum in patients being treated for falciparum malaria in order to obtain data on fully effective levels. Ineffective serum levels should be ruled out in cases not responding to chloroquine, especially when chloroquine-resistance is suspected.

[A case of chloroquine-resistant (R1) falciparum malaria from the East African Comoros Islands (author's transl)]

An African from the Comoros Islands, who has been living in Berlin for eleven years and who had made his last journey to Africa two years before, fell ill with high fever upon returning from a visit to Mayotte and Grande Comore. His blood smear revealed trophozoites of Plasmodium falciparum. After intake of 25 mg of chloroquine base per kg body weight within 66 hours, defervescence and clearance of blood ensued and by the fourth day after start of treatment the parasites could no longer be detected in the blood. On the 25th day high fever occurred and P. falciparum was found again. After chloroquine treatment had been repeated with an additional single dose of 75 mg pyrimethamine and 1.5 g sulphadoxine the patient remained healthy. During observation over a period of eight months plasmodia could no longer be detected in thick films.

Chloroquine-resistant Plasmodium falciparum from East Africa: cultivation and drug sensitivity of the Tanzanian I/CDC strain from an American tourist

A strain of Plasmodium falciparum, designated Tanzanian I/CDC, from an American tourist returning from Tanzania, was isolated in vitro and in the Aotus monkey. Clinically, the infection showed a late recrudescent pattern of chloroquine resistance. In 2 inoculated Aotus monkeys, the infection recrudesced after a dose of chloroquine (40 mg/kg) curative for sensitive P. falciparum strains in the Aotus monkey. In 4 ,dditional monkeys two primary infections and one of the recrudescent parasitaemias were cured with a 100 mg/kg dose of chloroquine; the second recrudescent parasitaemia was cured with an additional 40 mg/kg dose of chloroquine. The 48 h in-vitro chloroquine-sensitivity test demonstrated that the Tanzanian I/CDC strain had a pattern of chloroquine resistance similar to a reference resistant strain, the Vietnam-Oak Knoll (FVO). These studies reinforce reports which suggest that chloroquine-resistant malaria is being transmitted in East Africa.

The concentration of chloroquine in serum during short and long term malaria prophylaxis with standard and 'double' dosage in non-immunes: clinical implications

The concentration of chloroquine in serum was analysed after one week, six weeks and one year on standard dose prophylaxis (300 mg chloroquine base once a week) and after six months on the double dose. After six weeks, the standard dose gave adequate protection against malaria. During the first weeks of prophylaxis insufficient protection might be achieved by the customary standard dose. In a double-dose group many values reached the point above which a higher incidence of side-reactions have been observed.

Habits of malaria chemoprophylaxis and an analysis of breakdowns in a West African mining town

In a West African community approximately 80% of the non-African personnel were taking malaria prophylactics in the recommended manner. The non-takers stated that they were afraid of side-effects of the drugs and/or under-estimated the risks of the disease. During one year 123 patients with clinically suspected malaria were studied. All patients with positive slides were cured with regular dose of 1.5 g chloroquine base. No chloroquine resistance was therefore demonstrated, although 4-aminoquinoline prophylaxis had been given for almost 20 years to thousands of non-African non-immunes as well as in pregnant women and children in the town. Common reasons for 'breakdowns' were febrile disease other than malaria, false positive diagnosis and improper chemoprophylaxis.

The treatment of malaria

At least four doses of quinine followed by a single dose of mefloquine or by a single dose of sulfadoxine-pyrimethamine are two highly effective regimens for chloroquine-resistant falciparum malaria. Mefloquine alone is valuable in ambulant patients. Chloroquine-sensitive falciparum malaria can be treated with a course of chloroquine. Vivax and all other types of malaria should be treated with sequential chloroquine and primaquine. Quinine, by intravenous infusion, is the most effective drug for severe falciparum malaria. The optimum intravenous dose varies between 5 mg/kg and 10 mg/kg administered over four hours. Intravenous or oral quinine should be administered about every 12 hours and the total daily dose of quinine should rarely exceed 20 mg/kg. Intravenous fluid input should be controlled in falciparum malaria to prevent pulmonary oedema. Established renal failure is best treated by dialysis. The value of adrenocortical steroids for falciparum coma has not been established. Fresh blood transfusion may be helpful in small doses for severe anaemia and to replace clotting factors. Anticoagulants, such as heparin, should not be used in falciparum malaria.