Dengue Outbreak in India Linked To Changes in the Climate

Temperature between 17 to 30 °C enhances the metabolism of mosquitoes, requires lesser time for incubation and increases disease transmission by four-fold.

Climate is the major risk factor for dengue outbreak in India, finds a research by an international team of scientists at the University of Liverpool.

This was achieved by evaluating the relationship of climatic factors in the spread of dengue in different climatic zones in the country through the states of Punjab, Haryana, Rajasthan, Gujarat and Kerala.

Dengue and Dengue Fever - Symptoms, Causes, Diagnosis, Treatment & Prevention
Dengue is a tropical disease caused by mosquitoes carrying the dengue virus. Symptoms include fever, joint & muscle ache, fatigue, nausea and skin rash.

‘Changes in a factor called extrinsic incubation period (EIP), the time taken for incubation of the virus in the mosquito was associated with the temperature of the region.’

The researchers focused on changes in a factor called extrinsic incubation period (EIP) of the dengue virus by taking into account daily and monthly mean temperatures in these areas.

EIP is the time taken for incubation of the virus in the mosquito. During this period, after the mosquito draws a virus-rich-blood meal, the virus escapes the gut, passes through the mosquito's body and reaches it salivary glands. Once this happens, the mosquito is infectious and capable of transmitting the virus to a human host.

It has been found that climatic conditions play an important role in EIP. Lower temperatures (17-18 °C) result in longer EIPs thereby leading to decreased virus transmission. With increasing temperatures, feeding increases because of enhanced metabolism of the mosquito, leading to shorter EIPs.

Dengue and Dengue Hemorrhagic Fever
Encyclopedia section of medindia gives general information about Dengue and Dengue Hemorrhagic Fever

Even a 5-day decrease in the incubation period can hike transmission rate by three times, and with an increase in temperature from 17 to 30 °C, dengue transmission increases fourfold. However, a further increase in temperature beyond 35 °C is detrimental to the mosquito survival.

The study was conducted by the University of Liverpool in collaboration with the Hyderabad-based Indian Institute of Chemical Technology (IICT), National Institute of Pharmaceutical Education and Research (NIPER), Guwahati.

Papaya Leaves’ Juice to Increase Platelets in Dengue
Carica papaya leaves juice or extract increases platelet counts in cases of dengue fever. Papaya leaves protect the bone marrow.

The researchers observed that except for Gujarat which comprises of arid regions, there was a strong correlation between rainfall and dengue disease burden. They propose an increase in breeding grounds for mosquitoes as a major reason for this finding.

The study found that Kerala being warm (temperature range 23.5-30 °C) and wet and with short EIPs (9-14 days) experiences the highest number of dengue cases. It has been found that EIP is the shortest during the monsoon season in most states and therefore there is an enhanced risk of dengue during this time.

Top 15 Do�s and Don�ts for Preventing and Managing Dengue Fever
Dengue can be easily prevented and managed if you follow proper precautionary measures. Here we give you the most important dos and don’ts for dengue fever.

Researchers say it is important to take into account the dynamic EIP estimates in different regions in assessing disease burden.

Dr Srinivasa Rao Mutheneni of IICT, who led the study and worked on this project during his visit to Liverpool as a University of Liverpool Indian Research Fellow, said: "This climate-based dengue forecasting model could help health authorities to assess the disease intensity in a geographic region, based on that they can plan disease control operations well in advance and optimize the use of resources meticulously."

Changes in temperature affecting the extrinsic incubation period of the virus, future changes in the climate might have a substantial effect on dengue and other vector-borne disease burden in India.

Dr Rao added: "Though such methods are in vogue for disease control operations, we are still in the initial stages of implementation of such strategic control methods. Factors such as population density and migration also need to be included for future risk assessment studies."

Source-Eurekalert