Mosquito menace: The ever daunting task of vector borne disease control

The world’s deadliest carriers of vector-borne diseases are becoming more difficult to eradicate as mosquito-caused epidemics continue to claim lives in India

Published: 15th October 2016 06:45 PM  |   Last Updated: 15th October 2016 06:48 PM   |  A+A-


The world’s deadliest carriers of vector-borne diseases are becoming more difficult to eradicate as mosquito-caused epidemics continue to claim lives in India and in other underdeveloped countries 

Twelve-year-old Gautam Chaudhary complained of high fever and chills on September 22 evening. Preliminary tests found that the boy had dengue. Three weeks on, his mother, Babita, is busy preparing a papaya leaf concoction in her Mumbai home for Gautam who is recuperating from the life-threatening illness. As Babita recounts the stories of the days that followed, she narrates it all in a matter-of-fact way. Did she expect a dengue attack in her family? “Well, I have never seen any fumigation in my neighbourhood. Surely not in the last month.” Gautam’s family had to move the boy from one hospital to another in search of good doctors. By then, his condition worsened and the doctors told Babita to be prepared for the worst.

However, in the first week of October his platelet count improved and he is back home. But not everyone has been as lucky as Gautam this season.
The mosquito has become the global public enemy no.1. Be it the Zika virus in the Americas, or dengue, chikungunya and malaria in India, mosquitoes are wreaking havoc across the globe. In Delhi, 952 cases of dengue were recorded in September alone. Also, India for the first time reported a chikungunya-associated death this year in the capital.

The city is also coping with a dengue outbreak with 2,133 cases and 11 deaths so far. Of the cases, more than 900 were reported in September alone.Ankita Sukla, 16, missed school for 15 days. The Dwarka resident had 104 fever for five days before she visited the doctor. “The dengue fever was accompanied by joint pain and rashes but matters became worse after the fifth day. I felt so weak that I couldn’t get up from my bed. My board exams are nearing and I couldn’t even study or attend classes.”

Delhi is also battling a chikungunya outbreak with 6,667 cases reported so far, compared to 64 cases last year. Ashwini Shrivastava, a resident of Malviya Nagar, visited the doctor after he had high fever two weeks back. “Subsequent tests confirmed my fear as I tested positive for chikangunya. Though the contamination was ‘low’, it gave me rashes all over the body. The pain hasn’t gone yet and I still can’t walk properly. Doctors say it may take six months or more to fully recover.”

Ashwini believes the state government is not taking adequate measures to check the menace. “Civic bodies should do regular fumigation both during the day and night to keep infections at bay. City hospitals need to be well equipped to help the poor, the worst affected.”
Even though Delhi seems to be battling a bad case of chikungunya, it is Karnataka that has been the worst hit by the vector-borne disease. As many as 10,494 cases have been reported in the southern state, making it the prime victim.

Odisha, Chhattisgarh and West Bengal accounted for 65 per cent of the malaria cases reported this year. While Odisha reported 1.1 lakh cases and 14 deaths, West Bengal registered 4,116 cases and 27 deaths. West Bengal is also battling a dengue outbreak that claimed at least 24 lives this year. According to some estimates, the number of dengue-related deaths in West Bengal is pegged at 38 as of September. There has been a 120 per cent increase in the number of dengue-related deaths from 2015. In 2015, 14 deaths were recorded of a total 8,516 recorded dengue cases.

How did it come to this?

Monsoons in India are synonymous to the triumvirate of mosquito-borne maladies: malaria, dengue and recently chikungunya. Mosquito nets, repellents and killer bats come out of storage and families perform various preventive rituals to protect themselves. While the rituals are elaborate and extensive, they are not foolproof. Homes and public spaces are ripe for mosquito breeding if a single preventive action is not taken. One bite by an infected mosquito is all it takes. And that is how thousands of Indians contract one of these painful and deadly diseases.

Delhi resident Rinku Kaw is not sure how she got the virus even after being a cleanliness freak. “Even though I got chikungunya about a month-and-a-half ago, I still have joint pain. I can barely cook and look after my children.” The homemaker says she has no energy left after fighting chikungunya.
The resurgence of these vector-borne diseases stems from multiple factors. At the core of which is vector control, and there can be no complacency in this aspect. Says Dr Mandar Kubal, a Mumbai-based specialist in Internal Medicine and Infectious Diseases: “Vector control is where everyone goes wrong, and mosquitoes strike back with the slightest complacency from our side.”
According to Dr Claire Donald, a researcher who studies mosquito transmitted viruses at the University of Glasgow, India’s problems are no different from other areas affected by the virus —India lacks in vector control strategies. “As there are, at present, no effective vaccines for zika, dengue or chikungunya, the only way to reduce the risk of disease is to reduce transmission through bites.” It is therefore important to control breeding and protect against mosquito bites, she says.
Bengaluru’s garbage menace has played an ugly role in putting the city on the chikunguya map of the country. “Even though residents segregate waste and take precautions to prevent breeding, the civic authorities have not done enough,” says Dr Sowmya Raghavan, a bio-chemist from Bengaluru. Be it garbage collection or fumigation, the city’s municipal corporation has failed its residents in both aspects this year.

Regular surveillance and fumigation are the backbone of the prevention practices. “There is a gap between the number of trained personnel to carry out the preventive measures and the size and population of the country. Therefore, the penetration of sanitation workers in all sections of society may not be adequate,” says Dr Kubal. This mismatch between manpower and population has resulted in ineffective implementation of prevention mechanisms and surveillance practices.

Vector control is not restricted to insecticide fumigation by the civic authorities. Individual homes also have a huge role to play. “We must keep our surroundings clean and garbage-free. Water should not be allowed to stagnate,”Dr Kubal adds.

He stresses the use of mosquito nets, repellents and wearing full-sleeve shirts and tops, and trousers. “Stay covered and make sure children playing outside are also adequately covered to avoid mosquito bites.”
India also lacks in active reporting when it comes to fevers and symptoms related to dengue, chikungunya and malaria. Dr Mamata Sahoo, a Bastar-based public health specialist, finds that the tribal population in the malaria endemic region does not report fevers. “Despite advising the locals to visit the clinic in case of malaria symptoms, they are indifferent and attempt home remedies,” she says.

First Chikungunya Death?

In 2006, chikungunya resurged in India after a 32-year hiatus, with 1.39 million cases reported that year. During the same period, a chikungunya fever epidemic was also reported in the Réunion Island where around 2,66,000 people (34.3 per cent of the population) were affected. Of these cases, 254 turned out to be fatal, thus changing the perception that the disease is non-fatal.
In India, though chikungunya has been commonly known only for inducing limbic deformities and debilitating pain and fever. Doctors have asserted that it is not a killer disease. “This is a misconception,” says Dr Kubal. “The correlation between an increase in mortality associated with a chikungunya epidemic was investigated in 2008 by experts in Gujarat,” he notes.
The 2008 study from Gujarat published in the Emerging Infectious Diseases journal found an “increase in mortality rates in Ahmedabad during August-November 2006 (when a chikungunya epidemic occurred in the city) compared with previous months in 2006 and the same months in the past four years.” The authors said the “mortality rate data for Ahmedabad were consistent with observations of other researchers that the virus may have mutated and become more dangerous.” Doctors say that if a patient has co-morbid conditions s/he has a risk of dying from chikungunya viral infection.
Despite studies like this, the Ministry of Health and Family Welfare continues to claim that chikungunya is not fatal. Authors of the 2008 study wrote: Although 10 chikungunya deaths were reported in Ahmebadad, the website of the government of India continues to report “zero deaths”. The World Health Organisation (WHO) in its chikungunya factsheet says that while “complications are not common, the disease can cause death in older people.”
Ten years and one death later, the health ministry still continues to call it non-fatal and is yet to modify its view based on the available evidence.
Next stop Zika Virus?

Just like chikungunya surprised the world with its resurgence in 2006, the Zika virus has had scientists in a daze this year. It was first isolated in 1947 in a monkey in the Ugandan Zika forest. The virus rarely caused complications in humans and for decades remained dormant, affecting only monkeys.
In 2007, the first Zika outbreak was reported in the Federated States of Micronesia, a Pacific island nation. By 2014, the virus had spread to four other Pacific island nations and has since been “spreading explosively”, according to WHO. As of now, 23 countries in the Americas have documented Zika virus outbreaks. The geographical spread of the Zika virus and its probable association with birth defects and neurological disorders have prompted WHO to declare a health emergency.

According to recent studies, 71 countries and territories reported evidence of Zika virus transmission. While India is not on that list, a Lancet study suggests that the country is vulnerable.
China, Thailand, Philippines and Indonesia are also at risk, according to the study. Dr Donald says that intercontinental travel and movement of goods and livestock are key factors that enable the spread of mosquitoes and thereby the virus itself. Explaining how movement increases the risk of the virus spreading, she says, “Mosquito eggs could get transported in tyres or in lucky bamboo. These vectors are highly invasive species and find new habitats. So, movement of infected people or livestock from endemic areas to naïve areas which already have competent mosquitoes can bring new viruses into contact with new mosquito populations.”     

Singapore is currently battling a Zika outbreak with nearly 200 cases reported so far. Experts believe that the virus is spreading at a high rate in the country because the population has a low immunity to the Zika virus. According to a study by the National Institute of Virology exploring Zika virus in the Indian context, “it is difficult to predict with certainty, what would happen if ZiV (Zika) virus is introduced into a new region and new ecosystem.”

Dr Donald says that it is possible that one may get lifelong immunity following the Zika virus infection as is the case with Chikungunya virus. “At the moment there are no long term studies to show that this will be the case for Zika virus as well. Studies in monkeys have shown that they are immune to reinfection by the same virus—but for how long it is not known,” she says.

The current Zika outbreak caught scientists by surprise and is an excellent example of why we must be prepared for the unexpected. “The best way to do this is by controlling mosquitoes,” says Dr Donald. In fact, we can learn a great lesson from our island neighbour, Sri Lanka. The country has eliminated malaria after battling the disease since the mid-20th century. The WHO declared the country malaria-free in September this year. Incidence of malaria decreased by 99.9 per cent after the country implemented a control programme. Until 2006, Sri Lanka recorded around 1,000 cases of the disease every year, but by 2012, the scenario changed. The last malaria case reported in the country was three years ago.

WHO hailed the efforts of Sri Lanka and called the strategies “highly effective”. Mobile malaria clinics were set up in high transmission areas. The clinics provided prompt and effective treatment which reduced the parasite reservoir and the chance of further transmission. The health centres screened every blood sample collected for the malaria infection and developed a nationwide electronic reporting system. “The backbone of the project was effective and extensive surveillance. They did not miss a single case and used targeted fumigation to manage mosquitoes,” says Dr Kubal.

At present, there is no specific antiviral or vaccine for zika, chikungunya and dengue viruses. Doctors and scientists say that it is hard to predict when these diseases will be eliminated. In many cases these viruses are emerging or re-emerging in many countries throughout the world. The only solution for now is to manage the breeding and spread of mosquitoes.

Fight against Malaria

India is in the control phase, but is working to reach pre-elimination by 2017 and complete elimination thereafter.

Since 2005, the Ministry of Health and Family Welfare has trained and deployed female volunteers or Accredited Social Health Activists in every village with a population of at least 1,000 people. They are trained to perform rapid diagnostic tests and administer artemisinin-based treatments.

The National Vector Borne Disease Control Programme also launched a partnership with the Indian Medical Association, under which over 2,50,000 Indian doctors are mandated to follow common guidelines for preventing, diagnosing and treating malaria.

India has also been a key player in developing vaccines.

Vector Control and Prevention Practices

  • Keep your surroundings clean and free of garbage
  • Do not allow water stagnation and eliminate mosquito breeding grounds
  • Change and refresh water from flower pots, vases, bird baths, pets’ water bowls etc. once a week
  • Keep stored water always covered with a lid
  • Spray insecticide aerosols during the day and at dusk
  • Do not wear clothes that expose arms and legs
  • Use mosquito nets or mosquito repellents
  • while sleeping
  • Install screens or wire meshes on windows to keep mosquitoes out
  • Cut tall grass and weeds to reduce outdoor resting places for adult mosquitoes

Flying danger

There are more than 3,500 species of mosquitoes

Female mosquitoes bite people, males don’t

Both sexes usually eat fruit and nectar but the female also needs blood protein to create good quality eggs

Females lay eggs every three days for their entire lives

Mosquitoes hate cold weather, anything below 80 degrees. If it dips below 50 degrees, some species hibernate

Female mosquitoes live for two months but males only live for about 10 days

Females who hibernate can survive as long as six months

Males find females by listening to the sound their wings make

Mosquitoes choose their victims based on sweat

Mosquitoes like dark clothes because dark clothing retains more heat

Bigger people tend to be bitten more as they give off more heat and CO2

Some alcohols encourage mosquitoes, as there’s more ethanol in your sweat

Mutation of Viruses

Dengue: The Dengue virus has undergone several mutations. Since 1943, it has mutated four times and all the four strains of the virus have been identified. Each have different manifestations. DENV1(classic dengue fever); DENV2 (hemorrhagic fever with shock); DENV3 (fever without shock); DENV4 (fever with shock).

Malaria: The Plasmodium falciparum parasite, which causes a deadly form of malaria, has been found to have developed resistance to the most effective anti-malarial drug—artemisinin. This mutation has not yet been seen in Indian samples. But it does pose a serious threat to the malaria endemic population of India.

Chikungunya: The resurgence of the Chikungunya virus in 2005 was accompanied by a mutation. The virus is normally transmitted by aedes aegypti mosquito, but it was transmitted in 2005–2006 by aedes albopictus mosquito, also known as Asian tiger mosquito.

Zika: Two mutations of the Zika virus have been identified—African and Asian. The Indian population is vulnerable to the Asian strain, according to some reports. Zika virus has been found to cause
microcephaly in newborns.


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