Electric Mosquito Racket

This device can be very helpful killing mosquitoes. It's a practical and efficient mosquito racket. The insects get electrically toasted. This version has a supporting light in the handle. Inside is a rechargeable battery. Image by Asienreisender, 2013

Dengue Fever



Dengue Fever - An Emerging Disease

In difference to malaria, which vector is a parasite, dengue fever is a viral disease. It's hosts are exclusively primates, mostly humans and some kinds of mosquitoes of the family aedes, who transfer it. There are four different subspecies of the virus.

Mosquitoe Larvas by Asienreisender

Mosquito larvas in a washing basin in Cambodia. Images by Asienreisender, 2013

Dengue fever is a very dangerous and painful disease. It is also an emerging disease, in fact the fastest dispersing disease in the world transfered by mosquitoes. In the fifty years between 1960 and 2010 dengue cases rose up thirty fold worldwide. In the ten years between 2000 and 2010 the number of cases doubled. That has to do with the expansion of the vector mosquito, what is in Southeast Asia (mostly) the Asian tiger mosquito, in general mosquitoes of the aedes family. This mosquito kind thrives in urban regions, and it's very adaptable. Since urbanisation is rampant in Southeast Asia, the Asian tiger mosquito has a rapidly growing habitat. But it's also worldwide spreading out. Globalization promotes the outspread of the tiger mosquito and the disease. Increased mobility as travel activities, population growth and global warming play a role as well.

Particularly the Philippines and Laos are in the center of the emerge, but also Thailand, Malaysia, Singapore and Vietnam have all reported an increase in cases.

The World Health Organization (WHO) estimates between 50 to 100 million annual cases of dengue worldwide, of whome half a million suffer a heavy course of disease and 22.000 people die; most of the victims are children. In Asia more than 90% of the heavy course of the disease hit children. The magazine 'Nature' wrote in it's April 2013 issue that even 390 million people get infected annually, referring to the studies of the scientific authors of the article.

Dengue is endemic in 110 countries in the tropical and subtropical regions of the earth; 75% of the dengue cases appear in the Asia/Pacific region.

Dengue fever is commonly also called the 'breakbone disease' or 'dandy fever'.



The disease is mostly transfered by the Egyptian tiger mosquito, also known as dengue mosquito or yellow-fever mosquito and, here in Southeast Asia, by the Asian tiger mosquito (lat. Stegomyia albopicta, aedes albopictus). There are some other mosquitoes who transfer the disease, particularly in New Guinea and in the south Pacific (the Polynesian tiger mosquito).

'Tiger Mosquito' by Asienreisender

Apparently a tiger mosquito, accidentally shot in flight on Ko Chang (Island). Image by Asienreisender, 2012

The circle of reproduction is similar to those of other mosquito-born diseases. A female mosquito sucks blood from an infected person and gets the virus in it's stomach. If the virus concentration is high enough, it can befall the mosquito's stomach cells and reach it's own blood circulation and contamine the mosquito's saliva. The extrinsic incubation time inside the mosquito is eight to ten days, means that the virus is then mature and harmful. Next time when it's biting someone, the infection is transfered to him or her. That's because at any bite a mosquito does, first it's injecting some saliva into the victims blood. A single bite of an infected mosquito is sufficient to transfer the disease, but not necessarily does. The virus can also be transfered from the mosquito to it's lavaes.

Although the mosquito gets itself infected by the dengue virus, there are no harming effects for the mosquito.

Dengue can't spread directly from one person to another one. But, if there is someone around who has dengue fever it is most important to protect everybody from the mosquitoes around, particularly the patient. They can transfer the virus from the infected person to other people around.

Dengue can also be transfered by blood transfusions and organ donations if the donator was infected himself.

The risk of an infection is highest in the rainy season (monsoon), for the mosquitoes then find the most breeding places and florish. The tiger mosquitoes prefer living indoor in urban regions and their daily peak periods of biting are around sunrise and up to two hours later and around sunset. Though, it can bite at any time of the day.


Course of Disease

After getting bitten by a mosquito and infected, dengue has a latent period between three and fourteen days. Most of the cases are mild and not to distinguish from a normal flu. One get's fever (up to 40 degree C) with ague, headache, eye- muscle- and limbpains. It comes together with a rash. After three to seven days it's easing off. Though, in two to four percent of the cases the course of disease continues heavy. A 'dengue hemorrhagic fever' (DHF), also called 'dengue shock syndrome' can appear. One to five percent of the heavy cases are lethal.

Dengue hemorrhagic fever is an acute shock syndrom with uncontrollable inner and outer bleedings; the blood circulation breaks down, abdominal pain, fever and headache, dehydration, brain caused spasms, coma, bloody vomiting, bleeding gums, a swollen liver and many more symptoms appear.

The shock occurs two to six days after infection with sudden collapses, cool clammy extremities, weak thready pulse and blueness around the mouth, blood spots in the skin, spitting blood, blood in the stool, bleeding gums and noise bleeding. It can lead to pneumonia and heart inflammation. The mortality rate at this stage is announced by the WHO by between 2.5% with proper medical treatment up to twenty percent, without. Letal cases are mostly among children.

The disease is very painful. The acute phase lasts between one to two weeks, but can extend much longer (four to six weeks). If the infection is survived, the patient is immune against all four dengue viruses for a short time and for the certain virus which caused the acute disease a live long.

When suffering the first typical symptoms it makes sense to have it checked by a doctor to make certain what it exactly is.



Particularly in the early phase of the disease it's difficult to make a diagnosis. Dengue starts very much like a flu; could be malaria, chikungunya, yellow fever, measles or several other diseases as well. A blood analysis in a laboratory is required for a safe diagnosis.

The blood test checks either for the virus itself or for the antibodies to it.

The handling of a blood sample requires strict safety measurements. Dengue is subject to compulsory registration to the health authorities in Germany, Austria and Switzerland.



As already mentioned, there is no specific therapy for dengue fever. In heavy cases it's recommendable to go into a hospital. A sympthomatic treatment as rehydration or administration of medicines, namely pain relievers, can be done. Aspirin should be avoided by all means, for it prevents blood clotting and will promote uncontrolled inner bleedings.

In heavy cases of blood circulation collapse a blood transfusion is necessary to counteract blood losses.

It's best to rest and drink plenty of fluids.



Still there is no vaccination or any other preventive medication on the market to immunize from dengue.

Asian Tiger Mosquito - Aedes Albopictus by Asienreisender

The Asian Tiger Mosquito is the main vector for dengue fever in Southeast Asia.

The fight against dengue is above all the fight against mosquitoes from the beginning on, by destroying their breeding places and killing the insects when possible. Little pools, cans, bottles, flower pots, tyres, plastic outside, where raining water can collect, has to be avoided. The use of repellents is absolutely necessary in areas with dangerous mosquito born diseases. A traveller or tourist should always have a repellent in his or her pocket. Since the Asian tiger mosquito is day-active, including dawn and dusk, mosquito nets make little sense, except for the morning hours.

As mentioned, acute dengue patients are themselves a vector for the disease which can be transmitted by mosquitoes to other people around. To prevent transmission, the patient has to be kept under a mosquito net and all the mosquitoes around have to be eradicated if ever possible. Dengue can become epidemic and infect ten thousands of people under bad circumstances.

Insecticides are risky to use, particularly inside houses. Their side-effects can cause other diseases, but might be the smaller sinister.

It's said there is a new trap developed, specialized for tiger mosquitoes, which lures them with a chemical smell to a poisoned breeding place. I personally haven't ever seen this trap respectively substance in a shop yet, though.

Some pharmaceutical companies work on the development of a vaccine against dengue fever. A French corporation announced a vaccine ready for use in 2015. As the WHO writes on her homepage, the "vaccine development has made remarkable progress in recent years, and the current dengue vaccine pipeline is advanced, diverse and overall promising".



A first infection with one of the four dengue viruses gives a lifelong immunity against this certain type, but a second infection with another type can be more severe than a first one, as Scott B. Halstead found out in around 1970.

The USA government tested dengue as a possible biological weapon. Officially the programme was ceased in 1970. Though, the USA were blamed to have initiated the heavy dengue outbreak on Cuba in 1981.

The WHO counts dengue as one of seventeen neglected diseases.

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Published on August 3rd, 2013