A rising mosquito index, no doubt, triggers fear of communicable diseases. But this time around, it is more of a matter of nuisance, with mosquitoes buzzing all around, than a scare of epidemics, according to the Health Department.
However, the issue needs to be actively tackled as mosquitoes are, indeed, carriers of diseases, according to Dr. Vivek Kumar, Additional District Medical Officer.
The density of mosquito population in the city has been found particularly high with a high index of Culex mosquitoes. Their dip density ranges from 80 to 130, which implies that a dip of a serving spatula into the breeding (water) site of Mosquitoes will have around that many larvae. Found mostly in drains and dirty water, Culex is associated with the transmission of filariasis. Though there is no notification of the disease, it is important that vector density is controlled, said Dr. Kumar.
High density of mosquito population was found over the last few weeks at Nazareth, Mattammel, Thevara, Chakkaraparambu, Palluruthy, Karanakodam, Ernakulam North, Edakochi, and Cherai. According to experts in the Health Department, fogging alone will not prove effective in eliminating mosquito. To control Culex, the larvae have to be killed, and spraying the drains early in the morning is the most effective method. Fogging only drives away mosquitoes. Besides, there is a particular time when it should be taken up, depending on mosquito activity, according to a biologist in the Health Department.
Aedes mosquitoes, the vectors for dengue fever, has a low density at present. Though a few dengue cases are reported in the district every day, there is no particular concentration in a place. The vector index of Aedes egyptii is measured using three indices—house index (HI) or the percentage of houses infested with mosquito larvae; container index (CI) or the percentage of water holding containers with infested larvae, and Breteau index (BI) or the number of positive containers per 100 houses.
If HI and BI are over 10% and 50% respectively, they are indicative of an alarming situation. The indices have been found low (with a maximum of 5% BI) in the city. However, despite a low index, the disease is reported almost every day. Inspection of houses and neighbourhood areas are conducted whenever dengue fever is notified, said Dr. Vivek.
Since Aedes is a fresh water breeding mosquito, maintaining dry premises is crucial. The fogging time for Aedes is between 4 p.m. and 6.30 p.m. The use of mosquito spray early in the morning has been proved effective in houses.
In the case of Anopheles stephensi , the vector for malaria, the man-hour density is the measure of density. The vector was picked up at Vaduthala, Chalikkavattom, Kathrikadavu, Ayyappankavu, Mattancherry, Vennala, K.L. Jacob Road, Thuravur (Angamaly), Vathuruthy, and Cheria Pappalissery (Nedumbassery). But the density is low. The fogging time for Anopheles is between 8 p.m. and 10 p.m.
