Dengue, Chickungunya (vector ¬borne) preventable till bite of mosquito


Vector borne diseases have assumed greater significance, as they are causes for preventable death. But presently they are preventable till a mosquito bite. Usually they cause fever for few days and discomfort. But in many cases they present a life threatening disease process, which is rapid and  difficult  to treat. Therefore prevention of mosquito bite is of great importance. Dengue shock syndrome, Dengue Hemorrhagic fever or encephalitis, ARDS present life threatening situations and difficult to treat.

Dengue

  • Dengue is a viral infection spread by the bite of the aedes aegypti mosquito and does not spread directly from person to person.
  • The symptoms start within five to six days after person you’re bitten by an infected mosquito.

            Chikungunya

It is a viral infection spread by the bite of the aedes aegypti mosquito.

The word “chikungunya” means “to become contorted” in Kimakonde, a language spoken in parts of Tanzania and Mozambique, which refers to the contorted walk of infected persons who develop severe joint pain.

Symptoms appear between 4 and 7 days after being bitten by the infected mosquito.

Routine fogging is dangerous as it can lead to increased resistance to the insecticides rendering them useless during outbreak situations

With increasing cases of mosquito-borne diseases, like dengue and chikungunya, being reported from the country, the government and scientists are looking at newer ways of controlling the vector and preventing the spread of infections

 

Outdoor fogging provides only short ­term benefits and can also affect non ­target organisms, such as honeybees, moths and butterflies, say experts.

Dengue and chikungunya, which together affected close to 46,000 people in the country this year, do not have any cure currently.

Patients infected with the diseases transmitted by day-biting aedes aegypti mosquitoes usually receive symptomatic treatment for fever, joint aches, internal bleeding, and in severe cases, organ failure.

For malaria, which is transmitted by the anopheles mosquitoes that bite at dusk, it is essential to detect cases early and start treatment.

However, the best method of preventing the disease is to control breeding.

This does not always happen properly on time as pointed out by a 2016 report by the Comptroller and Auditor General.

The report found that the existing number of domestic breeding checkers was so less that it was possible to revisit a house in Delhi only after 44 days, as opposed to every six days as per the norm set by the municipal corporations.

And, several houses remain unchecked because either nobody is home or they deny the breeding checkers entry. The implementation has to be better for effective control of vector

The report states that only 30% of all health institutions in Delhi were reporting cases of dengue defeating the purpose of surveillance and early detection of an outbreak. Cases were also being under-reported.

In 86% of the houses that were treated for breeding, the method or the chemical formulations used were not prescribed or recommended by national agencies responsible for setting guidelines.

Routine outdoor fogging was also carried out by the corporations  that is recommended only for emergency situations. Routine fogging is dangerous as it can lead to increased resistance to the insecticides rendering them useless during outbreak situations.

“Pesticides have been a cornerstone of vector-borne disease control. Use of chemicals on a vast and increasing scale has led to the widespread development of resistance,” according to a report by the World Health Organisation.

“Outdoor fogging with insecticides looks dramatic and hence provides visible evidence that the government is doing something. Fogging requires considerable resources, provides only short-lasting benefits, and has been severely compromised by the spread of vectors resistant to the available insecticides. Fogging can also affect non-target organisms, such as honeybees, moths, and butterflies,” said a study.

A growing resistance by anopheles mosquitoes to pyrethroids threatens to reverse all gains made since 2000, according to another study which reported an increasing mosquito survival.

“This is a concern not just for malaria but all mosquito-borne diseases, given that insecticides play a major role in vector control. This has led to a three pronged effort to develop new vector control tools as quickly as possible,” the study said.

Resistance is known to affect all major malaria vector species and all four recommended classes of insecticides. Since 2010, a total of 61 countries have reported resistance to at least one class of insecticide, with a 50 of those countries reporting resistance to 2 or more classes, according to WHO.

There are, however, newer measures for preventing vector borne diseases.

THE WOLBACHIA TRIAL

India has collaborated with researchers from Australia to created modified mosquitoes that have been infected with Wolbachia bacterium. The bacterium ends the disease transmitting capability of aedes aegypti mosquitoes that transmit dengue and chikungunya. A lab trial is currently underway at Vector Control Research Centre, Puducherry. Studies have also shown that the wolbachia bacteria resists the malaria causing parasites in anopheles too.

DENGUE VACCINE

Dengvaxia by French drugmaker Sanofi Pastuer is currently the only vaccine against dengue available in the world. It is not yet available in Indian markets as the Indian Council of Medical Research in in the process of conducting research to check the level of seroprevalence (the number of people who have at least once been infected with dengue).

“The subset of trial participants who had not been exposed to dengue virus infection prior to vaccination had a higher risk of more severe dengue and hospitalisations due to dengue compared to unvaccinated participants,” according to WHO.

India has also developed a dengue vaccine candidate, which confers protection against all four strains of dengue without increasing the risk of lethal secondary infections from different strains. There are several other dengue vaccine candidates under development.

MALARIA VACCINE

Mosquirix developed by GlaaxoSmithKline is the world’s first malaria vaccine and has been shown to provide partial protection against malaria in children against malaria caused by plasmodium falciparum, that can cause cerebral malaria. It has been recommended by WHO for pilot introduction in three African countries

 

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