Antigenic diversity of Plasmodium vivax and their geographic distribution in Thailand.

Fifty-eight monoclonal antibodies (MAbs) raised against the erythrocytic stages of Plasmodium vivax were selected for typing of 501 P. vivax isolates from different geographic locations throughout Thailand. Based on their reactivities in the indirect fluorescent antibody test, these MAbs were classified into five groups: group I MAbs showing generalized staining of all blood stages; group II MAbs reacting with merozoites and their organelles; group III MAbs reacting with the surface membrane of merozoites; Group V MAbs reacting with the surface membrane of trophozoites and schizonts; and group VII MAbs reacting with internal components of the parasites. Sixteen MAbs reacted with more than 95% of the isolates; the epitopes recognized by these MAbs were considered as being invariant. The remaining MAbs reacted with 30-90% of the isolates, and the epitopes recognized by these MAbs were regarded as being variable. The variant epitopes were associated with > 200-, 135-, and 100-kilodalton (kDa) molecules of all blood stages, the 95-kDa molecule on merozoite organelles, the 200-kDa molecule on the surface of trophozoites and schizonts, and the 85-kDa molecule of the parasite internal components. Antigenic diversity occurred among the P. vivax population in the endemic areas of Thailand and was shown to vary from place to place and was highest in the area with the highest rate of transmission along the Myanmar border in western Thailand and along the Cambodian border in eastern Thailand, including Trat (48.4%), Tak (41.7%), Chantaburi (36.5%), and Mae Hong Son (36.4%). Demonstration of antigenic diversity of P. vivax parasites signals a note of caution in the development of vaccines for vivax malaria. The vaccines should be directed against protective, conserved and not against variant epitopes.

Antigenic disparity of Plasmodium vivax causing initial symptoms and causing relapse.

Relapse infections are an important obstacle to the successful treatment and control of Plasmodium vivax malaria, but little is known about the nature of the relapse. To provide insight into the antigenic disparity of the parasites causing initial clinical symptoms and causing relapse, a panel of 58 monoclonal antibodies (MAbs) against erythrocytic stages of Plasmodium vivax was tested by indirect fluorescent antibody test in five relapse cases. The initial and relapse strains from three patients (R3, R4, and R5) exhibited similar IFA reactivity with all MAbs tested, whereas the isolates from two relapse cases (R1 and R2) showed different patterns of reactivity and were seen only with 15 MAbs In case R1, different IFA reactivities were observed with 12 MAbs, nine of which reacted with the initial (RPV261) but not the relapse (RPV393) isolates, whereas the other three MAbs reacted only with the relapse isolates. With regards to the second relapse case (R2) in whom two relapses occurred, different IFA reactivities were demonstrated with seven MAbs that reacted only with the initial isolate (RPV 182) and with the isolate from the first relapse (RPV 240) but not with the isolate from the second relapse (RPV 300). The antibody responses from patients who developed primary clinical symptoms and relapse were detected by Western immunoblotting. In cases R3, R4 and R5, there was no difference in the spectrum of antigens from initial and relapse sera recognized by the antibodies. In contrast, in cases R1 and R2, the molecules recognized by antibodies in initial and relapse sera were markedly altered. In case R1, the series of molecules of P. vivax antigens recognized by initial (RPV 261) and relapse (RPV 393) sera were 21, 25, 31, 39, 42, 61, 95, 115, 200, > 200 kDa and 21, 24, 31, 35, 57, 75, 200, > 200 kDa, respectively. In case R2, the initial serum (RPV 182) recognized P. vivax antigens with molecular weights of 23, 30, 52, 57, 68, 75, 85, 95, 115, and 195 kDa while the first relapse (RPV 240) and the second relapse sera recognized P. vivax antigens with molecular weights of 23, 30, 52, 85, 95,115 kDa and 30, 57, 68, 75, 85,195 kDa, respectively.

Treatment of Opisthorchis viverrini and intestinal fluke infections with Praziquantel.

The study was carried out from September to November 1997 in Phrae Province of northern Thailand. A total of 95 adult patients with Opisthorchis-like ova in their stools were randomly treated with two different manufactured Praziquantels. Group 1, consisting of 49 patients, received a single dose of 40 mg per kg Praziquantel manufactured by the Thai Government Pharmaceutical Organization. Group 2 (46 patients) received Biltricide at the same dosage. Haplorchis taichui, H. yokogawai, Echinostome spp., O. viverrini, Taenia saginata and Enterobius vermicularis were expelled in the stools after treatment. Minute intestinal flukes were detected in 64% of patients. O. viverrini was found in lower proportion of 17%. By formalin-ether concentration examination one stool specimen from each patient, the cure rate in both groups on the 30th day of treatment was 100%. The side effects of the two different Praziquantel treatments were mild with no significant difference. Praziquantel, regardless of its manufacture, proved effective against O. viverrini and other minute intestinal flukes (H. taichui, H. yokogawai and Echinostome spp).

Two doses of artemether/mefloquine or artesunate/mefloquine combination for multidrug resistant falciparum Malaria.

Plasmodium falciparum in Southeast Asia is highly resistant to chloroquine, sulfadoxine/ pyrimethamine, quinine and even mefloquine. The use of two doses of short course artemether/mefloquine combination has been shown to be effective in a recent study. In the present study, we have assessed the efficacy of short course treatment with artesunate/mefloquine, in comparison with artemether/mefloquine in patients with multidrug resistant falciparum malaria. Ninety-nine Thai male patients who sought consultation at Makham Malaria Clinic, Chantaburi (eastern part of Thailand), were randomized to receive either the combination of artemether (150 and 100 mg; group A) or artesunate (150 and 100 mg; group B) with mefloquine (750 and 500 mg) at 24 hours apart. The follow-up was on days 1, 2, 7, 14, 21, 28, 35 and 42. Patients in both groups showed a rapid initial response to treatment; fever and parasite were cleared within 48 hours in 100 and 100% vs 91.8 and 96%, for group A vs B, respectively. All patients in group A had completed the 42 day-follow up; however, two patients in group B did not finish the 42-day follow-up. The cure rate was 100% in either group. No serious adverse effects were found. Artemether or artesunate with mefloquine given two doses at 24 hours apart can be used as effective alternative treatment regimens for multidrug resistant falciparum malaria.

Effect of artemether on electrocardiogram in severe falciparum malaria.

The effect of intramuscular artemether (intramuscular loading dose of 160 mg, followed by 80 mg daily for another 6 doses), in comparison with that of quinine (intravenous infusion of loading dose of 20 mg/kg, followed by 10 mg/kg q 8 hourly for 7 days), on the electrocardiograph of severe falciparum malaria patients were investigated in 102 Thai patients (92 males, 10 females) admitted to Pra Pokklao Hospital, Chantaburi, southeast of Thailand. Fifty patients (19 with quinine and 31 with artemether) were eligible for ECG analysis. Hypotension was found significantly more common in the quinine group (13 vs 2 cases). Thirteen, 5 and 1 patients with quinine treatment, respectively, had tachycardia, non-specific T-wave change and QTc prolongation. No significant dysrhythmia was found despite high plasma quinine concentrations. Five patients died; their ECGs were not significantly different from those who survived. In the group with intramuscular artemether, 17 cases had tachycardia prior to artemether treatment. QTc prolongation and non-specific T-wave change were found in 2 and 6 cases. One patient had RBBB and second degree AV-block on Day 1, but returned to normal on Day 2. No other dysrhythmia or other significant changes in ECG tracing which would suggest any effect of artemether on cardiovascular system were observed.

Quinine-tetracycline for multidrug resistant falciparum malaria.

Plasmodium falciparum in Southeast Asia is highly resistant to chloroquine and sulfadoxine/ pyrimethamine. Quinine-tetracycline has been used as a second line treatment for uncomplicated falciparum malaria, but duration of treatment varies from place to place. The 7-days course of this combination has been shown to be very effective. However, due to the cinchonism adverse effects, the patient compliance has not been satisfactory. We have evaluated the efficacy of a 7-days course of tetracycline in combination with either 5 or 7-days course of quinine. Ninety male Thai patients who were admitted to the Bangkok Hospital for Tropical Diseases were randomized to receive tetracycline 250 mg qid for 7 days in combination with either quinine 600 mg tid for 5 days (Q5T7; group A) or quinine 600 mg tid for 7 days (Q7T7; group B). The patients were hospitalized for 28 days. Patients in both groups had a comparable initial response to treatment, with the clearance of fever and parasites within 4 days. There were 46 and 40 patients in group A and B, respectively, who completed the 28 day of follow-up. The cure rates were 87 and 100%, respectively for group A and B. No serious adverse effects were found in either group; transient nausea, vomiting and tinnitus were common findings. The incidence of adverse effects was not different between the two groups. The results from the present study suggest that a short course treatment of quinine (Q5T7) had significantly decreased the cure rate. In areas with quinine resistant falciparum malaria, a full course of 7-days quinine, in combination with 7-days course of tetracycline is recommended for hospital treatment. However, an alternative shorter course of antimalarials is suggested for home treatment.

Integration of control measures for malaria vectors in endemic areas of Thailand.

Various vector control measures were applied in different endemic areas in two provinces, Saraburi and Chanthaburi, with comparison among different control measures. Application of IGR (insect growth regurator, pyriproxyfen) was introduced at Wat Tam Pra Pothisat, Tab-Kwang District, Saraburi Province. Some integration measures were performed at villages 6 and 8, Patavee, Makham District, Chanthaburi Province. In Tab-Kwang District with low malaria endemicity at the study site predators were not able to be released due to rapid velocity of running water. IGR could effectively control malaria compared to the basin released predators. Another endemic areas villagers 6 and 8, Patavee, Makham, Chanthaburi Province was chosen. Highly endemic multidrug resistant malaria has been prevalent for many years in this area. Integration of Kanda's trapping system, application of IGR, use of both residual spraying and impregnated bed-net methods with etofenprox successfully interrupted malaria infection. The application of these methods as an integrated control system could be adjusted to environmental conditions. The results of this study suggest rapid effective vector control.

Pharmacokinetics of praziquantel in patients with opisthorchiasis.

The pharmacokinetics of praziquantel was investigated in 9 Thai male patients with asymptomatic opisthorchiasis (stool positive) and 9 patients (6 males, 3 females) with moderately advanced infection (hepatomegaly). The geometric means of the pretreatment Opisthorchis viverrini egg count in these patients were 2,950 vs 4,468 eggs per gram of stool. The results indicate the impairment of metabolism of praziquantel in the moderately advanced stage opisthorchiasis. The pharmacokinetics of the drug in these patients during the acute infection was markedly altered when compared with that after recovery and in patients with early stage of the infection. The clearance rate (Cl/f) was significantly reduced [medians and ranges of 106 (43-242) vs 192 (112-692) and 171 (133-427) ml/min/kg] and the t1/2z and MRT were prolonged [t1/2z: 3.8 (2.0-6.2) vs 2.7 (1.7-4.3) and 2.3 (1.7-2.8) hours; MRT: 6.2 (3.2-11.0) vs 4.6 (2.7-6.2) and 4.5 (2.9-5.1) hours]. In addition, AUCo-alpha was significantly greater [6.0 (2.5-15.6) vs 3.5 (0.6-6.0) and 3.9 (1.6-5.0) micrograms hour/ml].

Mefloquine level monitoring in patients with multidrug resistant Plasmodium falciparum on the Thai Myanmar border.

A total of 42 patients with uncomplicated falciparum malaria who attended the malaria clinic in Mae Sot, Tak Province were treated with single oral dose of MSP 3 tablets (Fansimef, equivalent to 750 mg of mefloquine) concurrently with primaquine (30 mg). They all contracted the infection from Cambodia. The aim of the study was to monitor the efficacy of MSP 3 tablets for the treatment of this highly multiple drug resistant strains of Plasmodium falciparum in this area. Of the 39 patients included for efficacy assessment, 13 (33.3%) patients had sensitive responses, whereas 15 (38.5%) and 8 (20.5%) had RI and RII types of response, respectively. Melfoquine concentrations on Day-3 after treatment in patients with sensitive and treatment failure groups were comparable; the respective mean (SD) values were 665 (279) and 772 (264) ng/ml.

Mefloquine monitoring in acute uncomplicated malaria treated with Fansimef and Lariam.

Mefloquine levels were compared between Plasmodium falciparum malaria patients with sensitive response and those with treatment failure who received 3 drug regimens of mefloquine (46 patients with MSP 3 tablets (Fansimef), 38 and 34 with mefloquine (Lariam) 750 mg and 1,250 mg). Mefloquine concentrations on Day-1 in any regimens in patients with treatment failure were significantly lower than those from the sensitive response, whereas there was no difference in the concentrations on Day-7. However, MIC values of mefloquine prior to drug treatment were comparable in both groups. The study suggests that pre-treatment in vitro sensitivity testing was a non-reliable indicator of clinical outcome. Mefloquine concentration on the first day after treatment is a better predictor of the treatment outcome.

Mefloquine levels in patients with mefloquine resistant Plasmodium falciparum in the eastern part of Thailand.

A total of 99 patients with uncomplicated falciparum malaria who attended the malaria clinic in Bo Rai, Trat Province were treated with a single oral dose of MSP 3 tablets (Fansimef; equivalent to 750 mg of mefloquine) concurrently with primaquine (30 mg). The aim of the study was to detect RII and RIII types of response with 3 tablets of MSP. Seven (8.1%) and 22 patients (25.3%) had RII and RIII types of response, respectively, and 58 (66.8%) had no parasitemia on Day-7 (S or RI response). Mefloquine concentrations on Day-3 after treatment in patients in the S/RI group were significantly higher than those with early treatment failure (RII, RIII), with the respective mean (SD) values of 1,959 (696) and 1,622 (863) ng/ml. The mean concentrations of mefloquine in these patients with RII and RIII types of response were higher than those with a sensitive response in a previous study. The result suggests that Plasmodium falciparum strains in this part of the country are highly resistant to mefloquine and that blood levels of mefloquine on Day-3 may also be a good indicator of treatment outcome in this particular area.

Intramuscular artemether in female patients with uncomplicated falciparum malaria.

Thirty-three female patients suffering from acute uncomplicated falciparum malaria were treated with intramuscular artemether for 5 days during May-October 1990. Fourteen patients received 160 mg as an initial dose, followed by 80 mg daily for 4 days. Nineteen patients with low body weight (mean weight of 36.5 kg) were given artemether at 3.2/kg as a loading dose and followed by 1.6 mg/kg/dose for another 4 days. The geometric mean of parasitemia was 17,378/microliters (range 640-234,720). The mean fever (FCT) and parasite clearance time (PCT) were 41.8 and 49.4 hours, respectively. Two patients had probable intercurrent infection with FCT of over 7 days. Thirty-one patients had completed the 28-day follow-up. The cure rate was 90.3% (28/31). Three patients had RI type of response. Mild and transient adverse effects were experienced in eleven patients; these consisted of pain at the injection sites, vomiting, dizziness, abdominal pain, palpitation and diarrhea. These symptoms may in part be due to symptom complex of malaria. The MIC of chloroquine, quinine, quinidine and mefloquine was performed in all patients but only 25 isolates were successfully cultured and tested. The MIC of all tested drugs were shown to be higher than that of previous studies, suggesting that there is a rapid increase of mefloquine resistant strains of falciparum malaria. In conclusion, artemether proves to be effective against multiple drug resistant falciparum malaria (including mefloquine resistant strains) and can be considered as an alternative antimalarial to mefloquine. The drug was well tolerated in female patients with mild and transient side-effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical trials with halofantrine in acute uncomplicated falciparum malaria in Thailand.

The antimalarial efficacy of halofantrine was compared with mefloquine in an open-label, randomized comparative trial in adult male patients with acute uncomplicated falciparum malaria. Twenty-eight patients received halofantrine and 27 received mefloquine. Halofantrine was administered in 3 doses of 500 mg at 6 hour intervals and mefloquine was administered in divided doses of 1,250 mg or 1,500 mg depending on whether the patients weighed less than or more than 60 kg. The patients were followed for 42 days and observed for drug tolerance and evidence of recrudescence. Response to treatment was favorable with both drugs, but three patients (two treated with halofantrine and one with mefloquine) did not completely eliminate malaria parasites from peripheral blood films in seven days. The parasite and fever clearance times were 75.6 and 55.7 hours, and 80.1 and 61.3 hours, respectively for halofantrine and mefloquine. However, 12 patients recrudesced during the 42 day follow-up period. Nine of these had been treated with halofantrine and three with mefloquine. The 42-day cure rate for the two drugs was 56% and 84%, respectively. The side-effects of halofantrine and mefloquine were comparable and transient. These are diarrhea, dizziness, orthostatic hypotension and black out. However, vomiting was found to be more common in mefloquine group (41% vs 22%).

Artemether in the treatment of multiple drug resistant falciparum malaria.

Artemether has the potential to be an alternative antimalarial for multiple drug resistant falciparum malaria. However, it has been associated with high recrudescent rates which may be due to incorrect dosage regimens. The dosage regimens are varied from country to contry. We have carried out a comparative study of two dosage regimens, ie 480 mg and 600 mg total dose given over 5 days in uncomplicated and severe falciparum malaria. 167 patients were included in the study, 61 with acute uncomplicated falciparum malaria and 106 with severe malaria. All patients showed a good initial response. The difference in total dose had no effect on the parasite or fever clearance time (PCT or FCT). However, the severity of the disease did have some influence of these times. The PCT and FCT from either regimen of uncomplicated malaria were significantly faster than those of severe malaria (p < 0.005 and = 0.05, respectively). The cure rate seems to have some correlation with the amount of drug given and severity of the disease. The cure rates in uncomplicated malaria were 84 and 92%, respectively, for 480 mg and 600 mg. In severe malaria the cure rates dropped to 65 and 76%, respectively, for 480 and 600 mg. We conclude that artemether can be considered as an alternative antimalarial for multiple drug resistant falciparum malaria. However, the cure rate of severe falciparum malaria in this study is not considered satisfactory in areas with multiple drug resistant falciparum malaria. Further studies are needed to assess the curative efficacy with different dosage regimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of quinine, quinidine and Cinchonine when given as combination.

Pharmacokinetics of quinine, quinidine and cinchonine when given as a combination were evaluated in Thai patients with falciparum malaria during acute infection and convalescence. The combination of quinine, quinidine and cinchonine was randomly given to thirteen patients at 400 mg or 600 mg (consisting of one-third of each component; 7 patients were enrolled in 400 mg regimen and 6 in 600 mg regimen) intravenously every 8 hours for 7 days. The drug combination was given again at day 35 to define the pharmacokinetics of each drug during convalescence. All patients with the 600 mg regimen had good response with 100% cure rate while patients with the 400 mg regimen had a good initial response but one patient recrudesed on day 46. This particular patient had plasma concentrations of all three drugs lower than the mean values of patients with sensitive responses. The plasma levels of quinine and quinidine obtained from the present study were higher than that expected from one-third of the conventional dose (600 mg) when given alone, suggesting drug combination interaction. The terminal half-lives of each of the three components were prolonged during acute malaria when compared to those obtained during convalescence.

Fansimef for prophylaxis of malaria: a double-blind randomized placebo controlled trial.

At a time when Fansimef, the fixed combination of mefloquine, sulfadoxine and pyrimethamine was considered for prophylaxis of falciparum malaria, a randomized double-blind study comparing the efficacy and tolerability of Fansimef with that of Lariam (mefloquine), Fansidar, chloroquine and placebo in malaria prophylaxis was performed in Thailand from July 1987 to January 1988. The study population of 602 adult males was recruited in Pak Tongchai District, some 360 km North-East of Bangkok, where multiresistant P. falciparum is endemic. All active treatments and placebo were given once weekly for 24 weeks with doses as follows: Fansimef: 125 mg mefloquine + 250 mg sulfadoxine + 12.5 mg pyrimethamine (1 half-strength tablet); Lariam: 125 mg mefloquine (1 half-strength tablet); Fansidar: 500 mg sulfadoxine + 25 mg pyrimethamine; chloroquine; 300 mg. A loading dose of 2 half-strength tablets was given in the Fansimef group in weeks 1 and 2 and in the Lariam group in weeks 1 to 4. The incidence of acute episodes of P. falciparum per 100 person months of prophylaxis was 0.17 each in the Fansimef and the Lariam groups, 1.18 in the Fansidar group, 0.69 in the chloroquine group and 0.64 in the placebo group (differences statistically not significant). Clinically adverse events were reported by 170 subjects (Fansimef 28, Lariam 29, Fansidar 41, choroquine 43, placebo 29; differences statistically not significant). The most frequent adverse events in all groups were headache, sleepiness, dizziness and weakness.(ABSTRACT TRUNCATED AT 250 WORDS)

Two-site sandwich ELISA for detection of Plasmodium vivax blood stage antigens using monoclonal and polyclonal antibodies.

Two systems of sandwich enzyme-linked immunosorbent assay (ELISA), a two-site monoclonal antibody sandwich ELISA MAb-MAb sandwich ELISA) and a two site polyclonal-monoclonal antibody sandwich ELISA (PAb-MAb sandwich ELISA) for the detection of Plasmodium vivax antigens were developed. The assays showed good correlation with the level of parasitemia when tested against serially diluted P. vivax parasites (r = 0.937, and 0.997 for MAb-MAb and PAb-MAb sandwich ELISA, respectively), with the ability to detect as few as 6.68 parasites/10(6) erythrocytes and 2.69 parasites/10(3) erythrocytes, respectively. The MAb-MAb sandwich ELISA was specific, since it was positive only with P. vivax-infected erythrocytes from vivax malaria patients and negative when erythrocytes from 34 healthy individuals and 30 falciparum malaria cases were tested. In contrast, cross-reaction was found in the PAb-MAb sandwich ELISA when the plates were coated with polyclonal IgG and tested against the serially diluted P. falciparum SO strain antigen prepared from in vitro cultures. Comparison between the two systems of two-site sandwich ELISA showed that the MAb-MAb sandwich ELISA was superior to the PAb-MAb sandwich ELISA: (1) it gave a higher sensitivity when tested with serially diluted P. vivax antigen preparations from vivax malaria patients; (2) it gave a higher specificity when tested with the SO strain of P. falciparum from in vitro cultures, (3) it gave a lower absorbance value when tested with erythrocytes from healthy individuals. All 281 cases of vivax malaria already proven by microscopic examination were positive by MAb-MAb sandwich ELISA.(ABSTRACT TRUNCATED AT 250 WORDS)

Preliminary report: a comparative clinical trial of artemether and quinine in severe falciparum malaria.

Twenty-six patients with severe falciparum malaria were randomized to be treated with quinine or artemether. Twelve patients received quinine at the standard dose and fourteen patients received artemether intramuscularly at a total dose of 640 mg over 7 days. The patients were kept in the hospital for at least 7 days. Peripheral smear was performed 6-hourly until there was no parasitemia, then daily until discharged. Adverse effects were monitored through physical examination, laboratory findings and questionnaires. Laboratory examination was performed on admission, day 2, day 4 weekly until discharged. The patients in both groups were comparable in age, body weight, admission parasitemia, hemoglobin and white blood cell count. The survival rates were 93% and 58% in artemether and quinine groups, respectively (p = 0.052 at 95% confidence, using Fisher's exact test). The parasite and fever clearance times, and the time taken to gain consciousness in cerebral malaria patients were not significantly different between the two groups. Adverse effects in the quinine group consisted of dizziness and vertigo which were found in 4 patients. No adverse effects were noticed in the artemether group. This preliminary report suggests that artemether is a good alternative drug for severe falciparum malaria and seems to be better than quinine regarding survival rate and side effects. Confirmation of these findings in a larger study size is needed.

Clinical trials of mefloquine with tetracycline.

A comparative trial of the combination of mefloquine or MSP with tetracycline was carried out in fifty-one adult Thai male patients with acute falciparum malaria. The patients were randomized to receive either the combination of tetracycline (250 mg qid for 7 days) with mefloquine 4 tablets (1,000 mg) or with MSP 4 tablets (one tablet contains 250 mg mefloquine, 500 mg sulfadoxine and 25 mg pyrimethamine). Fifty patients had a complete 28-day follow-up period. Both regimens produced similar efficacy with no difference in adverse effects. In the mefloquine plus tetracycline group, the cure rate was 72% (18/25). One patient had an RIII response, the others showed initial response to the treatment with FCT and PCT of 40.7 +/- 27.4 and 76.2 +/- 34.2 hours (mean +/- SD) respectively. However, 6 patients developed recrudescence between days 17 and 29 (RI), 3 of these had vomiting. In the MSP plus tetracycline group, the cure rate was 76% (19/25). The means (+/- SD) of FCT and PCT were 44.7 +/- 38.0 and 80.6 +/- 25.0 hours, respectively. Six patients had recrudescence between days 17 and 31 (RI), 2 of these had vomiting. Although the addition of tetracycline improved the cure rate of mefloquine when compared with standard dose of mefloquine alone (3 tablets), these combinations seem to be useful in areas where alternative drugs are not available.

Thrombocytopenia in malaria.

The relationship between platelet counts and platelet bound (direct) or platelet directed (indirect) serum antibody concentrations was studied in 17 patients with Plasmodium falciparum malaria and 12 patients with P. vivax malaria. Platelet counts rose with recovery from infection from 196 +/- 84 x 10(9)/l (mean +/- SD) and 195 +/- 34 x 10(9)/l to 319 +/- 99 and 283 +/- 62 x 10(9)/l respectively (p less than 0.002), but there was no relationship between either absolute platelet count or changes in counts and either indirect or direct platelet antibody levels. These findings suggest that a non-immunologically mediated mechanism is involved in the pathogenesis of thrombocytopenia in malaria.