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Prevent dengue fever with guppies

Dr Mohd Khadri Shahar is one Malaysian in Cambodia who is using his career experience to help eliminate insect-borne diseases like dengue fever by encouraging people to take simple steps to live healthier lives.

Dr Shahar serves as Technical Officer for Dengue Fever and Communicable Diseases in the Cambodia office of the World Health Organization. He says people can just throw a few ordinary guppy fish into their water tanks. The guppies love to eat mosquito larvae, thus curbing the spread of both dengue fever and chikungunya.

Dr Shahar only arrived in Cambodia in mid-July, but already has been on house-to-house inspections in six villages in Kandal and Takeo provinces and is starting to help promote easy and free or very inexpensive programs to help rural Cambodians improve public health and prevent diseases.

He noticed on his inspections Cambodians love to have big earthen jars of water, some full, some half-full and some neglected. He said these earthen water jars constitute 95 per cent of the breeding grounds for mosquitoes.

“Put a few small guppy fish inside the water tank and all the larvae will be gone in a few minutes, they get eaten by the guppies. It doesn’t hurt the drinking water. Guppies have a very strong survival rate. This method of disease prevention is called biological control. Guppies also replicate very fast.”

Dr. Shahar sees public participation as key to disease prevention.

“The message I want to give here, is for people to spend ten minutes each weekend and make sure to clear all the breeding sites and introduce guppy fish into all the water tank jars.”

One family could keep their area clean of standing water in jars and rubbish, while another might not. The mosquito has a flight range of 200 metres from the breeding spot, thus enabling infections coming from neighbor areas.

Dengue fever is also transferred by what’s called “vertical transmission” which means a mosquito that bites an infected person will pick up the virus and subsequently lay 80-100 eggs, then hatching takes place producing larvae and those new immature stages of mosquitoes are also infected with the virus and can quickly pass the virus to people living there when turn to adult stage mosquitoes.

“One mosquito can infect many people,” he said, calling for a rapid response for every dengue case.

“Once a dengue case is confirmed by the hospital or laboratory, people should take immediate action to terminate all the adult mosquitoes in their home or working area, even in the hospital compound, itself and ensure no mosquitoes are breeding. At hospital, people should be encouraged to give a complete address so that immediate action can be taken by the disease control unit to visit their house and treat their water containers or do fogging. ”

The key for Dr Shahar is breaking the cycle of dengue transmission. Once the infected mosquito killed there will be no bites or transfer of dengue virus to other family members or neighbours. He’d like to see Cambodian citizens respond quickly to break the transmission on their own.  

“In Malaysia, guppy fish actually can easily be found and collected from ponds, and water in road side gutters and streams. Aquarium fish shops are also selling the guppy fish.”

“You have to break the transmission. I always try to emphasis this main point. We cannot just rely on MOH or other people to kill a mosquito in our house!”

The danger with dengue is that an infected person can get bitten again by a mosquito, that mosquito can lay infected eggs, and suddenly after a week there are hundreds of mosquitoes flying around which are infected with dengue, ready to spread the disease.

“With the Bacillus (Bti) and the insecticide (Abate), we can kill all the larvae in between 20 minutes and four hours, but the guppies eliminate the larvae much faster.”

Dr Shahar says the guppies are known as “seven colors fish” and invites people to pick up a few and bring them home and put them into their ponds and water containers.

Another method of preventing the spread of disease in Cambodia, according to Dr Shahar, is education about sanitation.

“Primary school children should be educated about sanitation; how to dispose of rubbish properly, and how to wash their hands properly. Education in primary school for sanitation is very important.

Control for the Aedes mosquito can be started from primary school.  The guppies can be given to the schools and given to the kids and they can take back to the parents and rearing it in their container,” he said.

Dr Shahar makes the case that human health is an asset and that if you are healthy, you can do everything. If you are not healthy, you are restricted from doing anything.

“When I see children in the village naked without shoes under the hot sweltering sun it makes me really want to learn the Khmer language so I can speak expressively and deliver the message and touch their heart and feelings.

“I think some of the Khmer people need motivation; need motivational people to relay the message and pass it to the public in a motivational way of talking. In a normal way it might not reach their heart, how important it is to control your health. When you are healthy you are fit to do anything, to learn and to work.”

It all started for Dr Shahar in 1993 when he started working as a research officer for the Institute of Medical Research in Kuala Lumpur. Today, he and his wife, who is also a public health official, working in Sabah, East Malaysia, have five children: three boys and two girls.

“For the last five years I have carried the slogan on dengue control: never quit; never surrender. Don’t give up. Carry on.”

Another disease Dr Shahar is concerned about is Japanese encephalitis, which is usually transmitted by mosquitoes around pig farms. Dengue fever, malaria and Japanese encephalitis as well as Chikungunya, is also an insect-borne virus, with more than thousand reported cases in Cambodia last year.

During his career in Malaysia, earning a PhD in medical entomology along the way, Dr. Shahar studied a disease vector of leishmaniasis, which is caused by a microscopic blood parasite. During 1999 in Malaysia, he was the first to carry out entomological study on this leishmaniasis vector in Malaysia. At the same time, many migrant workers were reported infected with the disease. Leishmaniasis or kala-azar, which mean ‘black fever’ is a disease causing an enlargement of the spleen and liver due to the microscopic parasite, which is spread by an insect called ”sand fly”.

During his research, he learned that most of the cases are imported cases that had been brought by the migrant workers and Malaysians who work in endemic countries of kala-azar.

So he went to India for three weeks and studied the species identification, habitats of the sand fly and learned that a lot of them were in cattle farming areas, whereas in Malaysia the sand flies were in the limestone areas.

His PhD thesis determined that the cases were imported and there was no domestic danger. But something else emerged from the research: that there were many new species of sand fly in Malaysia.
While doing his PhD research, he was appointed by a minister to carry out research on Aur Island and a few other islands off the east coast of Malaysia.

Dr Shahar and his team performed a “bare-leg landing catch” in which they offered themselves up, buffet style, for biting midges to land on, then caught them.

“That species attacked people during daytime, not at night. After they bite, they drill into the sand for breeding and eggs-laying. The biting was opportunistic and when their nest was disturbed by tourists.”

Tourist arrivals were down in the islands because of the irritating qualities of the sand flies, so Dr Shahar advised insecticide spraying two metres above the high tide level along the beaches, with great success.

“We managed to control about 400 metres of beach for about one month. So they loved it because their method can only control the midge for three days. Guidelines were given so that every resort cooperated to spray the beaches and successfully control it for many months and we really had a major tourism impact.”

For personal protection from the biting midge, Dr. Shahar advises the use of extra amount of suntan oil or olive oil on exposed skin which disrupts the flies’ functions and kills them in less than five minutes.

Finally, Dr Shahar with deep hope says, “Please bear in mind, dengue fever and dengue hemorrhagic fever have no cure. Do not wait or regret until your beloved ones, your wife or your husband, your son, your daughter or your parents get the fever. By that time it is too late. Act now!”



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