RESUMEN
To identify the seasonal effect on the frequency of malaria and its species in blood samples of patients referred to private and public Labs of Karachi for suspected Malaria and to observe if there has been any change in the frequency of the malaria species from May 2009 to Feb 2011. A cross sectional retrospective review of the laboratory data of the positive blood samples of malarial parasites over a period of 22 months from May 2009 till Feb 2011 via convenient sampling from a private and a public sector laboratory. Blood samples of patients of all ages and gender who were referred from various doctors with suspected diagnosis of malaria were checked for the presence of malarial parasite [MP] using the slide method and/ or Immunochromatographic Technique. The samples found positive for the MP were then analyzed for species identification. The seasonal variation in the frequencies of these species assessed and the number of positive MP results observed from May 2009 to Feb 2011 were described. Plasmodium vivax was found to be the most frequently identified plasmodium species present in 78.6% of the cases followed by Plasmodium falciparum. Adult males predominated over female and children. Frequency of Malaria was highest in the months of September with an overall surge of cases in the months of Aug to Dec. It is also observed that the number of cases in the year 2010 is much higher than in 2009. The study concludes that P.vivax is the most frequently isolated species causing malaria in Karachi. The frequency of P.vivax causing malaria seems to have increased from 2009 to 2010. Malaria was more frequent in the months of August to December in Karachi affecting adult males more frequently as compared to females and children