Epidemic of malaria in Barmer district (Thar desert) of Rajasthan during 1990

Barmer district of Rajasthan in Thar desert and hitherto a hypoendemic area for malaria came in the grip of a severe malaria epidemic during 1990. The epidemic occurred as an aftermath of floods, preceded by normal rains during 1988 and 1989 after a prolonged drought phase. The epidemic was spread over the whole district including Barmer town. Annual Parasite Incidence (API) and Annual falciparum Incidence (AFI) for the district touched record figures of 17.20 and 5.83 respectively while for the Barmer town they were 36.5 and 14.0 respectively. Out of the eight PHCs, Baitu PHC was the worst affected where the two indices touched all-time high figures of 55.3 and 19.6 per cent respectively. A total of 122 infants were reported positive for malaria, of which 103 were contributed by Baitu PHC alone. Eighty per cent infant positivity was spread over September and November, indicating a high rate of transmission. A total of 47 deaths due to cerebral malaria were reported. However, in view of the high infectivity among infants and paediatric groups there was a strong possibility of deaths among these groups which could not be verified. Entomological findings revealed that a sudden increase in An. culicifacies densities due to extensive breeding potential, as a sequel to floods, activated the transmission, which was maintained at a low level by An. stephensi, predominant in this desert region. Other factors which contributed to the intensity and extent of epidemic were the return of drought-migrated population from malarious areas, low cattle density, malaria non-immune population, inadequate and poor spray coverage and delayed radical treatment. Insecticide adult susceptibility tests revealed a high degree of resistance in An. stephensi against DDT and dieldrin.