Protecting yourself from dengue-carrying mosquitoes

Photos sourced by author from the internet
Photos sourced by author from the internet

With 229,736 cases in the country, including 958 deaths, from January 1 to August 17, 2019, dengue is indeed “the fastest spreading vector-borne disease in the world,” according to the Department of Health (DOH).

Based on the DOH routine surveillance system, the most affected age group among dengue cases is 5-9 years (23%).  In like manner, the most affected age group among dengue deaths is 5-9 years (40%).  The majority of dengue cases are male (52%), whereas the majority of dengue deaths are female (54%).

Already, eleven out of 17 regions have exceeded either the alert or the epidemic threshold forcing the health department to declare a national dengue epidemic on August 6.  

To lessen the number of cases, the health department launched the “4 o’clock habit” drive where residents are asked to clean their surroundings and drain water containers to prevent the spread of dengue-carrying mosquitoes.

For its part, the Department of Science and Technology (DOST) has been doing its best to control the proliferation of the day-biting Aedes aegypti mosquitoes.  DOST is the government’s executive department responsible for the coordination of science and technology-related projects.

According to studies, each Aedes female can lay up to four batches of eggs – at least 40 eggs per batch – during its life cycles.  It takes 7 to 10 days for an egg to develop into an adult.  The eggs reportedly can survive for up to a year – even with their breeding grounds go dry under natural conditions.  This means that the eggs can still go on when the breeding sites become filled with water again.

DOH said breeding sites of these carriers are those that can accumulate water. These include tree holes, bamboo stumps, earther jars for water storage, discarded bottles and tins, old rubber tires, rain barrels for collecting rainwater, clogged roof gutters, coconut shells and husks, and bancas and small fishing boats.

Inside the house or office buildings, the potential sites for the mosquito larvae are uncovered water storage tanks, flower vases, saucers for ornamental plants, soft drink bottles, and metal and plastic pails for water storage.

In 2011, through its Industrial Technology Development Institute (ITDI), introduced the mosquito ovicidal/larvicidal trap (OL trap) to help curb the population of the dengue-carrying mosquitoes.

The main component of OL trap is the solution made from natural active agent which is safe to humans but lethal to mosquitoes.  The two other components are the black container (like a cup) and a small strip of lawanit (that looks like an ice drop stick).

“The scent of the solution invites female mosquitoes to the trap where they lay eggs on the lawanit stick and on the solution itself,” the DOST explains.  “The stick, moistened by the solution through capillary action, is highly attractive for mosquitoes to lay eggs on.

“As the eggs and the hatched larvae (also called ‘wrigglers’) get exposed to the solution, they die.  The trap does not kill the adult mosquitoes.  Instead, its ovicidal and larvicidal effect prevent the next generation of mosquitoes from reaching adulthood, thus curbing the Aedes mosquito population.”

The DOST advised that each house should have at least four OL traps, two placed inside the house and the other two placed outside, particularly dark corners.  “Ideally, the trap can cover a 50-meter radius, so another set of traps should be placed before the end of the covered distance.”

Meanwhile, the Philippine Textile Research Institute (PTRI) has developed mosquito repellant textiles that can be used against Aedes mosquitoes.  It’s called mosquito re-coil, a modern take on the traditional mosquito coil (“katol”).

“Commercially available topical repellents using essential oils as active ingredient last only for a few hours when applied on skin,” wrote Rodolfo P. de Guzman in an article published by S&T Post.  “In some instances, these may even have harmful effects particularly to persons with sensitive skin.”

Research studies headed by Evangeline Flor P. Manalang used natural essential oils as active ingredients.  “The application of controlled-release system on natural textiles through surface modification technology can provide protection from mosquitoes up to six days per activation,” the PTRI senior science research specialist reported.

One of the benefits of this technology is that it can easily be adopted to existing textile finishing mills because it requires machineries already existing in the mills, Guzman wrote.  It is made from natural active ingredients and natural textile thus it is safe to be used and reused. 

“It can be replenished with the active ingredient easily and provides longer protection against mosquitoes,” Guzman added.

This is good news indeed. “With the development of mosquito-repellant finishing technologies, local finishing companies can adopt this technology to add functionality and premium to textile which in turn can be converted to various end uses that are of value to people,” Manalang said.

Another medical breakthrough is the development of what will perhaps take over from the controversial Dengvaxia.  DOST said it has already developed a “possible” cure for dengue.  Called Irtadevir, it can be given for two days with the treatment benefit immediately seen thereafter.

“Irtadevir is a combination of herbal drugs, the first in the market,” explained Dr. Rita Grace Y. Alvero, a pharmacologist from the College of Medicine at the De La Salle Medical and Health Sciences Institute in Dasmarinas, Cavite.  “It addresses the root cause of the problem by reducing the replication and infectivity of the four serotypes of the virus.”

There are four viruses of dengue: DEN 1, DEN 2, DEN 3 and DEN 4.   This means a person can develop four infections in a lifetime.  Often, infection with a subsequent strain results in more serious illness, though experts are unsure why this happens.

According to Dr. Alvero, Irtadevir works by decreasing the viral load and reducing the ability of the virus to produce infection, thus it is recommended that the drug be given to patients before the virus increases rapidly.”

Irtadevir will be used and marketed as an antiviral drug.  “We can give it when the patient has a mild symptom and the doctor is thinking it could be dengue, so that it will not progress to the severe form of the disease,” Dr. Alvero told S&T Post. 

She added the drug can also be given and will still have a positive effect on treatment in patients who are already in the severe stage of the disease.

“This is the first definitive treatment for dengue,” said Dr. Alvero, who is the founding president of RGA BioPharma Solutions, Inc.  “It fills the gap because there are no other treatment options.”

Dengue fever usually starts suddenly with a high fever, rash, severe headache, pain behind the eyes, and muscle and joint pain, says the World Health Organization (WHO).  The severity of the joint pain has given dengue its other name.

Nausea, vomiting, and loss of appetite are common, the WHO says.  A rash usually appears 3-4 days after the start of the fever.  The illness can last up to 10 days, but complete recovery can take as long as a month.  Older children and adults are usually sicker than young children.

Most dengue infections result in relatively mild illness, but some can progress to the deadlier dengue hemorrhagic fever (DHF).  With DHF, the WHO states, the blood vessels start to leak and cause bleeding from the nose, mouth, and gums.  Bruising can be a sign of bleeding inside the body.

Without prompt treatment, the blood vessels can collapse, causing shock.  This is what experts call as dengue shock syndrome.  DHF is said to be fatal in about 5% of cases, mostly among children and young adults.

“Children are much more likely to get DHF than adults,” Dr. Allan Schapira, then an official of the WHO Regional Office in Manila, told EDGE Davao.  “This is the reason why children are much more at risk of dying.  In adults, dengue fever usually does not develop to the severe form.”