Plasmodium falciparum strain characterization in highland and lowland areas of Muheza, northeastern Tanzania
Introduction: Different parasite strains have variable roles in the development of clinical malaria. Similarly, environmental factors such as altitude and climate have significant contributions to the development of clinical disease. This study was conducted as part of ongoing project on the epidemiology of malaria in Muheza district, northeastern Tanzania. It aims at providing information on P. falciparum genetic diversity, multiplicity of infection and their influence on febrile conditio.
Methods: Random blood samples were collected from 1956 individuals aged 6 months to 45 years in Muheza district during short rains (November to December 2003). Out of those, 615 were parasitologically positive, of which 264 samples met the inclusion criteria for molecular characterization. The selected samples were from individuals who were febrile or afebrile, positive for P. faliparum with parastaemia 400 parasites per _l of blood and had no danger signs such chronic diseases and complicated malaria. Genotyping of the selected samples was done for Merozoite surface protein 2 (msp2) marker using polymerase chain reaction (PCR) and restriction digestion with Hinf1. STATA 7.0 was used for data analysi.
Results: Genotyping was successful on 192 samples with 46 (23.96%) highlands and 146 (76.04%) from lowland areas. Out of those, 27.08% (52/192) had parasites belonging to 3D7 family while 15.10% (29/192) had FC27, and 57.81% (111/192) were of both allelic families. Individual parasite family distribution in both strata (highland and lowland areas) was not significantly different (highlands: 3D7 = 59.3%, FC27 = 40.8% and lowlands: 3D7 = 66.7%, FC27 = 33.3%; p = 0.512). The level of multiple infection (with both parasite families) was higher in lowland than highland areas (lowlands: 63.0% and highlands: 41.3%; p = 0.026) but the trend of an individual being infected with both families was shown to increase in lowlands and vice versa in the highlands. Overall prevalence of fever was not significantly different in the two altitude strata (highlands = 34.8%; lowlands = 40.4%; p = 0.495). Logistic regression model, adjusted for altitude strata and age showed that 3D7was fairly associated with fever as compared to FC27 allelic family (OR = 2.56, 95% CI 0.89–7.37; p = 0.082) while the combination of the two families was significantly associated with fever episodes as compared to FC27 family alone (OR = 2.93,95%CI 1.10–7.86; p = 0.037).
Interpretation: There was homogenous distribution of P. falciparum allelic families in low and high altitude areas, with 3D7 being more associated with fever episode. This information has to be considered when designing interventions such as malaria vaccine trials.
Ishengoma, D., Kafuye, M., Massaga, J., Malecela, E., Kitua, A., Magesa, S., & Lemnge, M. (2005). Plasmodium falciparum strain characterization in highland and lowland areas of Muheza, northeastern Tanzania. Acta Tropica, 95(Suppl.), S212.