Honored to be part of the “workshop on Climatic Change and Vector Borne Disease” hosted by Community & Family Medicine department,All India Institute of Medical Sciences, Rishikesh, Uttarakhand India, 4th Feb 2019.
Two days conference had engaging deliberations along with new doctors taking new courses on community health and particularity with respect to vector borne diseases. ICMR and many other organisations were part of the conference.Altitude and malaria are related with each other as the temperature decreases with increase in altitude,. As per the available literature, malaria has been found prevalent sometimes at 5000 ft altitude in the Himalayas and at still higher levels (6000–7000 ft) in South India, however, they are neither frequent nor severe in character and their origin is not certain. In Nainital district, malaria has been reported till Amia village near Kathgodam which is at the altitude of 614 m.
The findings of the present study revealed that cases of malaria were found beyond Kathgodam, i.e. in Bhorsa village at an altitude of 578 m and has started penetrating up to 1227 m (Nishola village,1227 m). It is to point out here that as per the records of District Malaria Office, Nainital, the whole district of Nainital reported only 3 cases of P. falciparum from 1998 to 2007. During the present survey, the reason of occurrence of malaria cases (4 P. vivax and 4 P. falciparum) in Bhorsa and Mirchijhala villages under hilly area of Bhimtal PHC may be attributed to increased temperatures.
Areas at higher altitude beyond Bhimtal were found free from malaria. Temperatures are favourable for transmission of malaria for some months even in hilly areas like Mukteshwar located at 2307 m height, but there is no record of malaria so far. It may be explained by the fact that for indigenous transmission of malaria, a buildup in density of anopheline vector is required.
The analysis of temperature from 1990 to 2008 indicated that increase in temperature in March and October months has opened the extra windows of transmission in Bhimtal. Further, from 2009–14, the rise in temperature has been observed in the months of March and October months at village-level. On the other hand, during winter months particularly January and February months, reduction in temperature has also been observed in 2008 as compared to 1990.
Another major finding of the study is the increase in temporal distribution of malaria vectors, increase in MHD and positivity of vectors for malaria sporozoite proteins during October and November months in Almora and during May and June in Nainital districts. Results of survey undertaken in 1998–99 for anopheline density in three different physiographic zones of Nainital district clearly indicated that An. culicifacies was found only in the month of August in hills, two months in Bhabar zone and four months in Terai and the highest density was 32 in hilly zone only in the month of August 1998 as compared to 110 (An. culicifacies) in the month of August 2013 in the present study. The highest density of An. fluviatilis in Bhorsa village (hilly area) was found to be 69 as compared to 33 reported from hilly areas earlier. In Almora district also, maximum MHD of An. culicifacies has been found to be 20 in the month of June 2012 while MHD of An. fluviatilis was found up to 74 in the month of May 2013.
The overall findings of the study highlight that due to increase in temperature the window of malaria transmission has expanded and P. falciparum, which was already at the threshold of hilly areas up to Kathgodam has extended further deep into the new hilly areas at higher altitudes, which may be attributed to rise in temperatures due to climate change. Increase in temporal distribution and MHD of malaria vectors further provide the evidence that conditions are quite suitable for indigenous transmission of malaria in hilly areas of Nainital and Almora districts of Uttarakhand which were hitherto free from malaria. It is to mention here that Almora, Pithoragarh and Uttarkashi districts which were considered free from malaria have started reporting malaria cases from 2010 onwards [Figure 6].
Craig et al determined a minimum of three consecutive months for suitability of malaria transmission in Africa. Cut-off of malaria transmission due to RH is not understood clearly that is why in the month of April, P. falciparum cases were detected from Bhimtal PHC, when RH was 36.32% [Table 1]. When the TWs are determined based on temperature alone and with T+RH combined, there is reduction in April and May months due to decrease in RH [Table 1]. The availability of malaria vectors, positivity of field collected mosquitoes for malaria sporozoite proteins and positivity of patients in the month of May suggest that transmission does not stop due to < 50–55% RH (44.7–45.2%). In a study undertaken in Jodhpur (Rajasthan) during the month of May–June, Batra et al reported malaria cases when the temperature was above 40 °C. It suggests that mosquitoes find micro niche for resting in houses to meet the condition of required temperature and RH which are quite different from outdoor climatic conditions. It warrants to elucidate the role of outdoor or indoor RH for determining transmission windows of malaria or any other vector-borne diseases. ( Source http://www.jvbd.org/article.asp)