Adaptive differentiation of Plasmodium falciparum populations inferred from single-nucleotide polymorphisms (SNPs) conferring drug resistance and from neutral SNPs.

BACKGROUND: Theoretical and experimental data support the geographic differentiation strategy as a valuable tool for detecting loci under selection. In the context of Plasmodium falciparum malaria, few populations have been studied, with limited genomic coverage. METHODS: We examined geographic differentiation in P. falciparum populations on the basis of 12 single-nucleotide polymorphisms (SNPs) in 4 genes encoding drug resistance determinants, 5 SNPs in 2 genes encoding antigens, and a set of 17 putatively neutral SNPs dispersed on 13 chromosomes. We sampled 326 parasite isolates representing 7 P. falciparum populations from regions with varied levels of malaria transmission (Gabon, Kenya, Madagascar, Mali, Mayotte, Haiti, and the Philippines). RESULTS: Frequencies of drug resistance alleles varied considerably among populations (mean F(ST), 0.52). In contrast, allele frequencies varied significantly less for antigenic and neutral SNPs (mean F(ST), 0.16 and 0.24, respectively). This contrasting pattern was more pronounced when only the African populations were considered. Signature of selection was detected for most of the resistant SNPs but not for the antigenic SNPs. CONCLUSION: These data further validate the utility of geographic differentiation for identifying loci under strong positive selection, such as drug resistance loci. This study also provides frequencies of molecular makers of resistance in some overlooked populations.

Prevalence of malaria parasitemia and accuracy of microscopic diagnosis in Haiti October 1995

In October 1995 the Ministry of Public Health and Population in Haiti surveyed 42 health facilities for the prevalence and distribution of malaria infection. They examined 1,803 peripheral blood smears from patients with suspected malaria; the overall slide positivity rate was 4.0 percent (range, 0.0 percent to 14.3 percent). The rate was lowest among 1-to 4-year-old children (1.6 percent) and highest among persons aged 15 and older (5.5 percent). Clinical and microscopic diagnoses of malaria were unreliable; the overall sensitivity of microscopic diagnosis was 83.6 percent, specificity was 88.6 percent, and the predictive value of a positive slide was 22.2 percent. Microscopic diagnoses need to be improved, and edequate surveillance must be reestablished to identify areas where transmission is most intense. The generally low level of malaria is encouraging and suggests that intensified control efforts (AU)

Prevalence of malaria parasitemia and accuracy of microscopic diagnosis in Haiti, October 1995 / Prevalencia de parasitemia por malaria y precisión del diagnóstico microscópico en Haití, octubre de 1995

In October 1995 the Ministry of Public Health and Population in Haiti surveyed 42 health facilities for the prevalence and distribution of malaria infection. They examined 1.083 peripheral blood smears from patients with suspected malaria; the overall slide positivity rate was 4.0 por cent (range, 0.0 por cent to 14.3 por cent). The rate was lowest among 1-to 4-year-old children (1.6 por cent) and highest among persons aged 15 and older (5.5 por cent). Clinical and microscopic diagnoses of malaria were unreliable; the overall sensitivity of microscopic diagnosis was 83.6 por cent, specificity was 88.6 por cent, and the predictive value of a positive slide was 22.2 por cent. Microscopic diagnoses need to be improved, and adequate surveillance must be reestablished to identify areas where transmission is most intense. The generally low level of malaria is encouraging and suggests that intensified control efforts targeted to the areas of highest prevalence could furhter diminish the effect of malaria in Haiti

En octubre de 1995 el Ministerio de Salud Pública y Población de Haití inspeccionó 42 establecimientos de salud para determinar la prevalencia y distribución de la infección por malaria. Se examinaron 1 803 frotis de sangre periférica obtenidos de pacientes con sospecha de tener esa enfermedad; la tasa general de positividad de los frotis fue de 4,0% (con un recorrido de 0,0 a 14,3%). La tasa más baja (1,6%) se observó en el grupo de niños de 1 a 4 años y la más alta en personas de 15 años de edad o mayores (5,5%). Los diagnósticos clínico y microscópico de la malaria fueron poco confiables; la sensibilidad general del diagnóstico microscópico fue de 83,6% y su especificidad de 88,6%, y el valor predictivo de un frotis positivo fue de 22,2%. Es preciso mejorar los diagnósticos microscópicos y reestablecer una vigilancia adecuada a fin de identificar las zonas donde la transmisión es más intensa. La frecuencia relativamente baja de la malaria es un dato alentador y sugiere que el refuerzo de las iniciativas de control dirigidas a las zonas de mayor prevalencia podría mitigar aun más el efecto de la malaria en Haití

Prevalence of malaria parasitemia and accuracy of microscopic diagnosis in Haiti, October 1995

In October 1995 the Ministry of Public Health and Population in Haiti surveyed 42 health facilities for the prevalence and distribution of malaria infection. They examined 1.083 peripheral blood smears from patients with suspected malaria; the overall slide positivity rate was 4.0 por cent (range, 0.0 por cent to 14.3 por cent). The rate was lowest among 1-to 4-year-old children (1.6 por cent) and highest among persons aged 15 and older (5.5 por cent). Clinical and microscopic diagnoses of malaria were unreliable; the overall sensitivity of microscopic diagnosis was 83.6 por cent, specificity was 88.6 por cent, and the predictive value of a positive slide was 22.2 por cent. Microscopic diagnoses need to be improved, and adequate surveillance must be reestablished to identify areas where transmission is most intense. The generally low level of malaria is encouraging and suggests that intensified control efforts targeted to the areas of highest prevalence could furhter diminish the effect of malaria in Haiti