Changing scenario of malaria in central India, the replacement of Plasmodium vivax by Plasmodium falciparum (1986-2000).

OBJECTIVES: Since 1986, we have been studying the changing epidemiology of malaria in a forest belt of Mandla, which has the highest number of malaria cases in central India (Madhya Pradesh) to define the epidemiological characteristics of the infection with each Plasmodium species in different seasons of the year. Our long-term objective was to determine the dynamics of Plasmodium vivax vs.P. falciparum infections. METHODS: Five villages underwent fortnightly surveillance of fever cases. Drugs were distributed within 24 h after results of blood smears became available as per Indian National Anti-Malaria Programme. Indoor resting mosquitoes were also collected fortnightly. RESULTS: The only two Plasmodium species encountered were P. vivax and P. falciparum in both children and adults. Relatively more malaria infections were recorded in children (< or =14 years) than adults (>14 years) (chi2=89.94, P<0.00001). However, there were significant falling trends in P. vivax from 1986 to 2000 in both age groups (< or =14 years from 63 to 13, P<0.0001 and >14 years from 84 to 7, P<0.0001). The indoor resting density of Anopheles culicifacies, an efficient vector resistant to both dichlorodiphenyltrichloroethane (DDT) (4%) and hexachlorocyclohexane (HCH) (0.4%), was very high throughout this period in all villages (52.35 +/- 31.8, range 5-200 per man hour). Anopheles fluviatilis was present in small numbers 0.78 +/- 1.24 (range 0-7 per man hour). CONCLUSION: Major contributors of the changing epidemiology of malaria in this area are changing drug sensitivity along with insecticide sensitivity.

The hospital- and field-based performances of the OptiMAL test, for malaria diagnosis and treatment monitoring in central India.

The performance of the OptiMAL test, to detect and differentiate Plasmodium falciparum and P. vivax, was evaluated in central India. The subjects were either symptomatic patients, who presented at a referral hospital in urban Jabalpur, or the inhabitants of remote, tribal, forested villages where malaria is a major public-health problem. In each setting, the results of conventional microscopy were used as the 'gold standard'. Under hospital conditions, the test had excellent sensitivity (100%), good specificity (97%), a high positive predictive value (98%) and a high negative predictive value (100%). The corresponding values in the field-based study in the tribal villages (100%, 67%, 84% and 100%, respectively) were almost as good. The results of OptiMAL testing reveal the decline in parasitaemias (of P. falciparum or P. vivax) after drug administration. For monitoring the effectiveness of treatment, the test could therefore be a useful alternative to microscopy, particularly (1) in places where the facilities for microscopy are poor or non-existent and (2) among hospitalized patients with severe, complicated malaria (in whom parasitaemia and drug response need to be followed very carefully). Follow-up (within 28 days of diagnosis) of the 58 malaria cases detected in the field revealed that the OptiMAL test can be used to detect re-infection with a different Plasmodium sp. (sensitivity = 100%; specificity = 100%; J-index = 1) or recrudescence/re-infection with the same Plasmodium sp. (sensitivity = 83%; specificity = 100%; J-index = 0.83) accurately. The ability to use the test to distinguish P. falciparum from P. vivax, and to identify mixed infections of these two species, is of great significance in areas where the preferred and effective therapy for P. falciparum malaria differs from that for P. vivax.