Be ready to combat vector borne diseases

 A small bite by a seemingly trifling organism can really turn your life upside down. Can you believe the fact that Vector borne diseases cause more than one million deaths each year? Yes, the number of deaths from vector born diseases is increasing alarmingly. Under tropical conditions of excessive heat and high humidity, man is subject to serious physical and mental handicaps.  He perspires profusely and loses vigor and energy and exposes himself to such dangers as sun stroke and diseases.  Tropical conditions are ideal for survival of germs and bacteria and also encourage the spread of insects and pests. On this World Health Day, WHO is drawing attention to a group of diseases that are spread by insects and other vectors, the heavy health and economic burden they impose and what needs to be done to reduce these burdens.    Many people who survive infection are left permanently debilitated, disfigured, maimed or blind.

The tag line of this year's World Health Day 'Small Bite Big Threat', compel to turn the attention towards the alarming occurrence of vector borne diseases, and it substantiate and recommends the governments, local authorities, community groups and individuals to work together to prevent vector borne diseases.  "Mosquitoes, flies, tick and bugs may be a threat to your health-and that of your family-at home and when travelling", is the message of this year's World Health Day.

Epidemiology Vectors are organisms that transmit pathogens and parasites from one infected person (or animal) to another.  Vector borne diseases are illnesses caused by these pathogens and parasites in human population and account for 17% of the estimated global burden of all infectious diseases.  Although, the disease most commonly found in tropical areas where 40% of the population is at risk, globalization, climate change and urbanisation have affected transmission of vector borne diseases and causing their appearance in countries where they were previously unknown.

Major Vector Borne Diseases

Sl.No.	Name of the Disease	Vector	Causative agent	Certitude
1.	Dengue	Infected Female  Aedes aegypti Mosquito	Virus	More than 2.5 billion people-over 40% of words population-are now at risk of dengue.
2.	Malaria	Infected female  Anopheles Mosquito	Parasite Plasmodium	Around the word, Malaria transmission occurs in 97 countries, putting about 3.4 billion people at risk
3.	Lymphatic filariasis or Elephantiasis	Infected Mosquitos  Culex, Anopheles, Aedes	Filarial parasite	More than 120 million currently infected and 40 million disfigured and incapacitated
4.	Chikungunya	Infected female  Aedes aegypti Mosquito	Virus	There is no specific treatment for the disease. Treatment is symptomatic.
5.	Yellow Fever	Infected Mosquito  Aedes and Haemagogus	Virus	Vaccination is the most important preventive measure against yellow fever. There is no specific treatment
6.	Schistosomiasis	Infested water. Larva of the Parasite released by fresh water snails.	Parasite  Trematode flat worms(Blood flukes)	Disease prevalent in poor communities without safe drinking water and sanitation.
7.	Chagas disease (American Trypano somiasis)	Triatomine Bugs  (Kissing bugs)	Protozoan Parasite  Trypanosoma Cruzi	Potentially Life threatening condition. 7-8 million people infected worldwide, mostly in Latin America. There is no vaccine
8.	Congo-Crimean haemonhage fever	Tics and livestock animals	Nairo Virus	Case fatality rate up to 40%. There is no vaccine available for either people or animals.
9.	Human African trypanosomiasis (Sleeping sickness)	Infected Tsetse fly	Protozoan Parasitc	Fatal without prompt diagnosis and treatment
10.	Leishmaniasis (Kala-azar)	Infected Female sand flies	Protozoan  Leishmania Parasites	Every year there are 1.3 million new cases and 20,000 to 30,000 deaths
11.	Lyme	Infected deer ticks	Borrelia Bacteria	It is now the most common tick borne disease in northern hemisphere
12.	Onchocerciasis (River Blind Blindness)	Infected black flies (Simulium spp.)	Parasitic worm onchocerca volvulus	In 2013 Colombia become the 1st country to be declared onchocerciasis free by WHO
13.	Japanese Encephalitis	Culex mosquito	Virus	Vaccine is the most preventive measure.  There is no specific treatment.

Prevention and control

Time has come to utilize the full potential for vector control for reducing vector-borne disease.  Back in 1940's, the discovery of synthetic insecticides was a major breakthrough and the massive use of insecticides in 1940's and 1950's successfully brought many important vector-borne diseases under control.  But, with in the past two decades, many important vector-borne diseases have re-emerged or spread to new parts of the world.  Alongside this alarming spread of vectors there is a serious concern of increasing insecticide resistance.  At the same time, the world is facing an extreme shortage of entomologists and vector control experts who promote 'integrated vector management' as the best approach to strengthen vector control.  This approach uses a range of interventions, from indoor residual spraying to the use of natural insect predators, in combination and in a value added way.  Integrated management makes sense as many vector borne diseases overlap geographically.

Key elements in the prevention and control of vector borne diseases include the following:

·         Long-lasting insecticidal nets.

·         Indoor residual spraying

·         Outdoor spraying

·         Addition of chemicals to water

·         Insect repellents like coils, vaporizing mats.

·         Reducing breeding habit of the vector.

·         Biological control of vectors through the introduction of parasites, predators or other living organisms.

·         Genetic control strategies.

·         Waste management.

·         Housing modification

·         Personal protection against the vector

·         Medication for travelers

·         Prophylaxis and preventive therapies.

·         Mass treatment for lymphatic filariasis, sotistosomiasis, onchocerciasrs 

·         Vaccines for Japanese encephalitis, Tick-borne encephalitis, and yellow fever.

·         Blood and body fluid safety in the case of Chagas disease and crimean-congo haemonhage fever.

·         Food safety in case of Chagas disease and Tick borne encephalitis.

Key challenges in the control of vector-borne diseases include.

Ø  Emerging insecticide resistance.

Ø  Lack of expertise in vector control.

Ø  Surveillance of vectors and their diseases.

Ø  Sanitation and access to safe drinking water.

Ø  Pesticide safety and poisoning

Ø  Climate and environmental change.

            The poorest segment of of the society and least developed countries are most affected by vector born diseases. illness and disability prevent people from working and supporting themselves and their family causing further hardship and impeding economic development.

World Health Day is celebrated on 7 April every year to mark the anniversary of the founding of WHO in 1948.  Each year a theme is selected that high lights a priority area of public health.  The Day provides an opportunity for individuals in every community to get involved in activities that can lead to better health.  In recent years, renewed commitments from ministries of health, regional and global health initiatives, with the support of NGO's, the private sector and the scientific community, have helped to lower the incidence and death rates from some vector-borne diseases.

            As vector borne diseases begin to spread beyond their traditional boundaries, action needs to be expanded beyond the countries where these diseases currently thrive.  WHO resolved to provide communities with information and aims to raise awareness about the threat posed by vectors and vector-borne disease, and to stimulate families and communities to take action to protect themselves from the perennial bane.  

- Dhanya Sanal, (Assistant Director, PIB)

Thiruvananthapuram

Courtesy: Press Information Bureau (pib.nic.in)