Malaria Data Trends in Karnataka

            The SPR rates by district from 1975-1984 and 1986-1995 in Karnataka exhibit a similar trend to API:  high SPR in the 1970’s in most districts, that decreased to a minimum in the mid 1980’s and then increased again in a few districts in the 1990’s.  In addition to showing a similar trend over time, SPR and API were also very highly correlated.  The Pearson’s correlation coefficients for API and SPR ranged from a low of 0.90 in Chikmagalur to a high of 0.9983 in Bidar, with a mean value across districts of 0.97.  API and SPR were therefore very similar measures of malaria prevalence in Karnataka during this time period.

            The Annual Blood Exam Rate (ABER) is a measure of the ratio between BSE and population and therefore can show the extent to which API and SPR are the same.  If we assume that API and SPR should have the same value because they are both measures of the malaria prevalence in an area, then the ABER would be 10%.  In all districts of Karnataka, the average ABER from 1975-1995 was above 10%, which implies that more than 10% of the population was sampled for blood slides.  In Kolar, Kodagu, Belgaum, Dakshina Kannara, and Bangalore in the 1980’s, ABER was below 10%, but then it improved.  When ABER is above 10%, API is considered to be a better indicator of malaria rates in the population than SPR (NMEP, 1996).  I chose to look at both rates, which allowed me to analyze the districts whose ABER is less than 10% for some years.

            Pf% increased significantly in the 1990’s in Karnataka.  Cases of P. falciparum have been increasing throughout India.  These increases can be attributed to environmental changes due to development projects, inadequate chemotherapy, inadequate use of control measures, timing of control efforts within the transmission season, and decreases in the number of P. vivax cases which can cause a change in Pf% even if the number of P. falciparum cases are not themselves increasing (NMEP, 1996).  Also, because preliminary analysis of some districts showed that Pf% did not correlate significantly with average mean temperature or precipitation, I did not study this variable separately.  However, SPR and API include all cases of malaria including those caused by P. falciparum.