Biomedical subjects

M Kalkoa

Publications and source records attributed to M Kalkoa.

3 recordsLinked to original sources

PubMed2000

Malaria eradication on islands.

BACKGROUND: To be successful, a malaria control programme needs to be tailored to the local epidemiological characteristics. Vanuatu consists of 80 inhabited islands in the Southwest Pacific, with hypoendemic and mesoendemic malaria and suitable conditions for sustained parasite elimination. We aimed to assess whether malaria can be eliminated on isolated islands. METHODS: Weekly mass drug administration of chloroquine, pyrimethamine/sulfadoxine (Fansidar), and primaquine was carried out on the entire population of 718 inhabitants of Aneityum island for 9 weeks in 1991 before the onset of the rainy season. Simultaneously with the administration of drugs, permethrin-impregnated bednets were distributed to the entire population. Larvivorous fish were also introduced into several identified breeding sites of Anopheles farauti. Periodic malariometric monitoring has continued for the past 9 years. Two additional islands of Vanuatu, one with and one without malaria transmission, have been monitored for comparison. FINDINGS: High community involvement as measured by drug compliance (88.3%) and bednet provision (0.94 nets per villager) has resulted in sustained interruption of malaria transmission in Aneityum. The surveys showed complete absence of Plasmodium falciparum after mass drug administration, and P. vivax disappeared from 1996 onwards, with the exception of two instances of imported infections (one mixed infection in 1993 and one P. vivax infection in 1999). INTERPRETATION: Malaria can be eliminated on isolated islands with well-adapted short-term mass drug administration and sustained vector control if there is a high degree of community participation.

Adolescent↗

PubMed1999

Intrinsic efficacy of proguanil against falciparum and vivax malaria independent of the metabolite cycloguanil.

Mutations in human CYP2C19 and parasite dihydrofolate reductase (dhfr) genes, related to poor metabolism of proguanil and resistance to cycloguanil, respectively, have both been assumed to be associated with poor antimalarial effect by proguanil. To study this, 95 subjects with uncomplicated Plasmodium falciparum or Plasmodium vivax infections in Vanuatu received proguanil treatment for 3 days (adult relative dose of 300-500 mg/day) and were followed up for 28 days. A similarly high antimalarial efficacy against both infections was observed in 62 patients with CYP2C19-related poor metabolizer genotype and in 33 with extensive metabolizer genotype, even though blood cycloguanil was significantly more often detected in those with extensive metabolizer genotype than in those with poor metabolizer genotype. All 28 P. falciparum isolates had two dhfr mutations (residues 59 and 108), suggesting moderate resistance to cycloguanil. The results suggest that the parent compound proguanil has significant intrinsic efficacy against falciparum and vivax malaria independent of the metabolite cycloguanil.

Adolescent↗

PubMed1998

Malaria epidemiology, glucose 6-phosphate dehydrogenase deficiency and human settlement in the Vanuatu Archipelago.

Vanuatu is located at the southeast margin of the malarious band extending from southeast Asia to eastern Melanesia. We analysed the malaria situation on different islands of Vanuatu, using passive case detection and malariometric survey data from 1985 to 1992, i.e. after the DDT residual programme ceased and before the impregnated bed-nets programme started on a larger scale. Malaria was mainly hypo-mesoendemic but with hyperendemic spots in certain years and on some islands. The transmission was generally more intense in the northern islands than in the south. In the late 1980s, annual parasite incidence per one thousand population (API) was around 180. The overall parasite rate was 11.9% with Plasmodium falciparum, P. vivax and P. malariae rate of 5.2, 6.7, and 0.1%, respectively. There was a seasonal fluctuation of P. falciparum incidence, whereas the P. vivax incidence was rather stable. Vivax malaria was confined to children less than 10 years old, while the intense in the northern islands than in the south. In the late 1980s, annual parasite incidence per one thousand population (API) was around 180. The overall parasite rate was 11.9% with Plasmodium falciparum, P. vivax and P. malariae rate of 5.2, 6.7, and 0.1%, respectively. There was a seasonal fluctuation of P. falciparum incidence, whereas the P. vivax incidence prevalence of P. falciparum only changed moderately with age. The mean rate of glucose 6-phosphate dehydrogenase (G6PD) deficiency among male subjects was in 7.4% but with a wide variation of 0-14.3% on different islands. A positive rank-order correlation was found between malaria incidence and G6PD deficiency rate on the different islands. A reasonable hypothesis is that malaria was introduced to the islands with the first human settlement 4000 years ago, with a geographical malaria distribution similar to the present situation. Different malaria endemicities possibly then selected different prevalences of G6PD deficiency over many generations.

Adolescent↗