Study Site

            Karnataka is located on the western coast of peninsular India which is shown in this map of India.  I based my investigation on 18 districts within Karnataka:  Bangalore, Belgaum, Bellary, Bidar, Bijapur, Chikmagalur, Chitradurga and Hassan, Dakshina Kannara, Dharwad, Gulbarga, Kodagu, Kolar, Mandya, Mysore, Raichur, Shimoga, Tumkur, and Uttara Kannara.  Chitradurga and Hassan are politically separate districts, but due to a difficulty in acquiring the climate data for the two districts separately, I combined the raw malaria data for the two districts and then calculated the malaria rates from the raw data.  Because districts in India are constructed politically rather than ecologically or epidemiologically, the combination of two districts should not affect the results, especially because these two districts share one boundary.  Also, because malaria data are collected in the same manner in each village and then aggregated at the district level, this should not affect the malaria rates in different districts.

            The NMEP program proved to be very successful in Karnataka because human plasmodia were eradicated from most of its area by 1964.  However, by 1970, especially in areas where An. culicifacies breeds, there was a rise in malaria rates.  This increase in malaria was a cause of increases in both P. vivax and P. falciparum.  P. falciparum prevalence was much higher in Bijapur, Raichur, Chitradurga, Bellary, and Bangalore (Roy et al., 1979).  Irrigation has contributed to a large degree of the malaria rise in Karnataka, especially in rural areas (Barai et al., 1982).

        Different climatic zones exist within Karnataka because of the influence of the Western Ghats that run north to south along the western coast of India and pass through Karnataka.  Thus Karnataka has humid and semi-humid climates to the west of the mountains and is semi-arid to the east of the mountains (Takahashi and Arakawa, 1981).  Dakshina Kannara and Uttara Kannara are part of a very wet and hot coastal climate.  The southern interior of Karnataka is hot, seasonally dry savannah landscape and consists of the following districts:  Bangalore, Bellary, Chikmagalur, Chitradurga and Hassan, Kodagu, Kolar, Mysore, Mandya, Shimoga, and Tumkur.  The northern interior of Karnataka is hot, semi-arid, tropical steppe climate.  Belgaum, Bidar, Bijapur, Dharwad, Gulbarga, and Raichur fall into this region.  The driest districts are Bijapur, Raichur, Bellary, and the southern half of Gulbarga.  The northeast monsoon, which is the lesser of the two yearly monsoons and occurs between October and December, affects the eastern part of the southern interior region, with rainfall stations in Shimoga and Kodagu accounting for four of the 14 highest rainfall stations in India (www.karnataka.com/profile/profile1/index.html)..

            The two primary vectors in Karnataka are An. stephensi and An. culicifacies, while An. jeyporiensis is a secondary vector (Sharma et al., 1994).  The following table lists the breeding sites and feeding practices of the two primary species in Karnataka.

Primary Vectors in Karnataka, India

An. culicifacies develops during the pre-monsoon period in Karnataka starting in February to May or from April to July.  Then, the monsoon flushes out the larvae and An. culicifacies does not develop again until after the monsoon.  An. fluviatilis also has a pre-monsoon peak in April and then An. annularis peaks occur in March, April or June (Collins et al., 1990).