The Effects of Insecticidal Nets on Asymptomatic Malaria in India

Caleb Sooknanan ‘20

Figure 1:

Figure 1:

Over the past decade, mosquitoes have been subject to many vector control strategies in order to control the spread of Malaria. Long-lasting insecticidal nets (LLINs) have been among the most effective, as their distribution has reduced global malaria morbidity by 45% since 2000. However, a large proportion of malarial infections remain asymptomatic, likely preventing malaria elimination programs from being executed to the greatest extent. To better understand the etiology of asymptomatic malaria, Dr. Mehul Kumar Chourasia and researchers at the National Institute of Malaria Research in India analyzed the impact of LLINs on the prevalence of asymptomatic malaria.

During the post-monsoon seasons of 2014 and 2015, the study was conducted among 5862 children living in the tribal villages of Chhattisgarh. A post-monsoon baseline survey was carried out before LLINs were distributed in 2014, with a follow-up in 2015. Peripheral blood smears of all cohort children were prepared to confirm the presence of malarial parasites. Children with no symptoms of fever, but whose blood had a parasitic presence, were considered to have asymptomatic malaria. The researchers evaluated malarial infections and the use of LLINs among the study cohort.

The researchers found that 7.4% of children in the baseline survey had malarial parasites in their peripheral blood samples. Nevertheless, the prevalence of subclinical malaria was significantly reduced to 1% in the second survey, after prolonged LLIN use.

Limitations of the study may have included its focus on the post-monsoon season. Further assessment is required for the dry season, when LLIN use might be reduced due to lower mosquito density or hotter weather. More research is needed to understand the prevalence of asymptomatic malaria during the low transmission seasons. Nevertheless, the researchers were successful in determining positive correlation between the use of LLINs and reduction of malarial cases. This suggests that high LLIN coverage and usage — supported by a strong active case surveillance system — would be a useful strategy in malaria elimination.

 

References:

  1. M. Chourasia, et al., Impact of long-lasting insecticidal nets on prevalence of subclinical malaria among children in the presence of pyrethroid resistance in Anopheles culicifacies in Central India. International Journal of Infectious Diseases 57, 123 – 129 (2017). doi: 10.1016/j.ijid.2017.02.001
  2. Image retrieved from: http://www.wikiwand.com/en/Malaria
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