Response of Plasmodium falciparum to dihydrofolate reductase inhibitors in Malindi, Kenya

The response of Plasmodium falciparum isolates to dihydrofolate reductase inhibitors (DHFRI) was examined in Malindi, Kenya. All 20 infected children treated with pyrimethamine/sulphadoxine responded. In contrast, after treatment with pyrimethamine, parasitaemia in 9 of 14 infections failed to clear or recrudesced during the seven-day follow-up. In a 48-hour in vitro test, five of six isolates resistant to pyrimethamine in vivo had a minimal inhibitory concentration (MIC) to pyrimethamine greater than or equal to 300 nmoles/1 compared with less than or equal to 100 nmoles/1 for the four sensitive isolates; four isolates did not grow. MIC to M-B 35769, an experimental DHFRI structurally similar to pyrimethamine were the same (six isolates) or 10-fold lower (three isolates). In the laboratory four of five isolates adapted to in vitro culture had the same MICs as in the field while one isolate became less responsive to both drugs. Cycloguanil (the active metabolite of proguanil) was more active in vitro in the laboratory than pyrimethamine or M-B 35769.     

Immunity after treatment of human schistosomiasis mansoni. III. Long-term effects of treatment and retreatment

Group mean Schistosoma mansoni reinfection patterns are presented for 2 years after treatment with oxamniquine in 1981 of over 100 9- to 16-year-old Kenyan schoolchildren, and for one year after retreatment in 1983 with either oxamniquine or praziquantel when most (nearly 700) infected people in the whole community were treated. Quality control confirmed comparable Kato egg counts throughout the study. Continuing transmission after 1981 raised prevalence to nearly its original level within 6 months, but intensity remained suppressed throughout the 2 year follow-up and very few children reacquired heavy infections (greater than 400 eggs/g). Age and sex had significant effects: reinfection diminished with age, especially among boys--a pattern not apparently attributable to differential water contact. Children with heavy pretreatment infections tended to develop heavy reinfections but this trend was not statistically significant on a group basis, nor were similar trends during the period of less pronounced transmission following the 1983 community treatment. Oxamniquine was equally effective in children receiving it in both 1981 and 1983, and the efficacy of praziquantel resembled that of oxamniquine. In this area of Kenya, repeated chemotherapy will be needed to contain transmission, probably annually or biennially, unless supplemented with other, effective control measures. These findings confirm the beneficial effects of treating even a limited segment of a community at intervals of a year or more without necessarily stopping transmission. They are also compatible with recent findings on potential immune mechanisms in man.     

Combination of ABO blood group incompatibility and glucose-6-phosphate dehydrogenase deficiency: effect on hemolysis and neonatal hyperbilirubinemia

The incidence (%) of hyperbilirubinemia (serum bilirubin ≥257 μmol/l) was similar in neonates with a combination of ABO incompatibility and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency (45%), with ABO incompatibility (54%) or G-6-PD deficiency (37%), alone (ns). Carboxyhemoglobin values, corrected for inspired CO, were similarly elevated in all three groups (0.87 ± 0.32%, 0.82 ± 0.29%, 0.76 ± 0.18%, respectively, ns), but correlated with bilirubin only in those with ABO incompatibility alone. ABO-incompatible/G-6-PD-deficient neonates, compared with those with either condition alone, are not at increased risk for hemolysis or hyperbilirubinemia.     

Effects of oropharyngeal/buccal insulin on glucose levels in alloxan-induced diabetic rabbits: clinical implications

The effect of oropharyngeal administration of insulin lente (BP, USP) on alloxan-induced diabetic rabbits was investigated. In mild cases of hyperglycaemia (below 500 mg/dl), a buccal dose of 100 IU was able to produce significant reduction in blood glucose levels over seven hours, as compared with diabetic animals during the same period. As much as 60% reduction in glucose level from the starting level could be achieved. However, at very high levels of hyperglycaemia (above 500 mg/dl), this regimen failed to produce normoglycaemia although it rendered the animal tolerant to high levels of glucose. This mode of administration of insulin did not produce hypoglycaemia in any of the animals: the blood levels in the mildly diabetic animals were reduced to normoglycaemia without progressing into the hypoglycaemic state. The administration of insulin to normoglycaemic rabbits by this route did not produce any reduction in glucose levels. This preliminary report suggests that a noninvasive oropharyngeal route may be an alternative for the clinical management of insulin and non-insulin dependent diabetes mellitus in man.     

Species composition of the Anopheles gambiae complex (diptera: Culicidae) at two sites in western Kenya

At two sites in the Kisumu area of western Kenya, the species composition of the Anopheles gambiae complex was determined by analysis of ovarian polytene chromosomes. Of 1,915 females, 26.1% were An. arabiensis Patton and 73.9% were An. gambiae Giles; one arabiensis x gambiae hybrid was identified. No major differences in the proportions of An. arabiensis and An. gambiae were observed between sites or between years. The ratio of An. arabiensis/An. gambiae was 6.7:1 (n = 231) in cow-baited traps, 0.2:1 (n = 1,525) in indoor resting samples, and 0.5:1 (n = 145) in all-night human bait catches. The proportion of An. arabiensis decreased progressively from 50.0% to 8.3% (n = 1,129) during 11 wk from September to November 1987; this change was correlated negatively with night temperature and positively with temperature range. In cow-baited traps, 97.4% (n = 194) of An. arabiensis were cow-fed and 95.8% (n = 1,054) of An. gambiae from indoor resting collections were human-fed. In indoor collections, 37.2% (n = 215) of An. arabiensis were cow-fed and 23.1% (n = 26) of An. gambiae from cow traps were human-fed. This demonstrates post-blood-feeding endophily by An. arabiensis and suggests post-blood-feeding exophily by An. gambiae. Malaria infection rates were higher for An. gambiae than for An. arabiensis by a ratio of 3:1 in 1986 (by Plasmodium falciparum ELISA) and 2.3:1 in 1987 (by dissection). Despite the higher proportion of infective An. gambiae, both species in this area serve as efficient vectors through their remarkably stable contact with the human population as demonstrated by their blood feeding and resting behavior.