A policeman returning from a mission in Haiti and a man who returned recently from Dhangadhi had contracted dengue. The tropical disease was first detected in Nepal in the tarai and inner-tarai districts in 2006 but no indigenous cases have been found yet in Kathmandu. [break]
The two recent cases were also imported and both patients have now recovered. But doctors are concerned that the disease can pose a threat even in Kathmandu.
Dengue fever is caused by the dengue virus (DenV), a mosquito-borne flavivirus, and is transmitted by the Aedes mosquitoes. It may also be transmitted via the infected blood of patients when they have the fever.
Aedes aegypti mosquito is the principal vector of the disease which is also transmitted sometimes by Aedes albopictus mosquitoes.
“Only a few Aedes albopictus mosquitoes were found in Kathmandu in the past but even Aedes aegypti were found last year,” national focal person for dengue Dr Basu Dev Pandey said. “We now have the vector mosquitoes, the patients and temperatures favorable for the vector. So, there is definitely a threat,” Dr Pandey reasoned.
Severity of dengue fever
Dr Pandey says dengue fever is mild like other normal fevers but a secondary infection is extremely dangerous.
“There are four serotypes of the virus and the first infection causes mild fever. If another serotype enters the body, the reaction of this new serotype with antibodies produced after the first infection causes dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS),” Dr Pandey explained.
DHF starts with severe headache, muscle and joint pains, fever and rash. The joint pains are so severe that the disease is nicknamed break-bone fever and it ultimately results in bleeding from joints all over the body. “It is extremely difficult to treat the patient after the onset of bleeding and may lead to death,” Dr Pandey said.
Unique mosquito
Dr Pandey says the threat posed by Aedes mosquitos is much greater as it is different from other mosquitoes and therefore can catch people unawares. “It is found in clean water and not filthy water like other mosquitoes, and it bites during daytime,” Dr Pandey said.
The mosquitoes breed on water collections in artificial containers such as plastic cups, used tires, broken bottles, flower pots, and even drinking water tanks. “It is also found near air coolers and refrigerators and is therefore a threat to even the more affluent,” he explained.
Entomologist at the Epidemiology and Disease Control Division Purushottam Gautam, who had stumbled upon some Aedes aegypti mosquitoes in Kathmandu during surveillance for Japanese encephalitis in 2009, said the preventive measures should be aimed at avoiding collection of water in used tires, bottles and cups, and regular disposal of water contained in storage tanks.
“But due to deficiency of water in Kathmandu, everyone has to store water for several days, not just in tanks, but in other vessels also, thereby providing a medium for dengue vectors to breed,” Gautam said.
Survey for vectors in 2010
There have been no surveys for dengue vectors in Kathmandu Valley. “We have not done a survey so far as we have not come across any indigenous dengue cases in Kathmandu,” senior epidemiologist at the Epidemiology and Disease Control Division Dr Bishwa Raj Khanal stated.
But the origins of infected patients do not matter when it comes to transmission of the virus. Dr Khanal promised that his division will conduct a survey for dengue vectors in August-September this year.
Entomologist Gautam did not rule out the possibility of a high prevalence of Aedes mosquitoes in Kathmandu as they can be ferried in by vehicles coming from high-prevalence areas like Birgunj, Biratnagar and Chitwan district and can breed in the favorable temperatures here.
Dr Pandey conceded that the presence of the vector, even though the density of its prevalence has not yet been ascertained, still poses the threat of an outbreak like that in Delhi, India in 2006 which claimed more than 50 lives including doctors.
“Raising awareness about the disease and its vector and measures by the government to control mosquitoes will go a long way in preventing a possible outbreak,” he concluded.
premdhakal@myrepublica.com
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