Vector Borne diseases are the illness caused by the vectors. A vector is a carrier of the causative microbe for various diseases such as mosquitoes, ticks and fleas. The reproduction rates of vectors are influenced by climate and weather. Such diseases are widespread and found throughout the world.

More than 700,000 patients die of vector-borne diseases. The major vector-borne diseases constitute about 17% of the infectious diseases in the world. The poorest populations of the tropical and the sub-tropical regions are highly affected by such diseases. Malaria is perhaps the best-known vector-borne diseases in the world. Let us have a look at the different vectors and the diseases spread by them.

Types of Disease Vectors

Vector-borne Diseases in India

Around 2 million malaria cases are recorded every year in India. Most of the rural areas in the country are prone to Malaria. The regions of Orrisa, Uttar Pradesh, Jharkhand, and Chattisgarh have many cases of malariaevery year. The World Bank Supported Vector-borne disease Control Project to be implemented in most of the endemic states. It will help the Government to prevent and treat malaria in the poorest regions. This project uses advanced technologies and medicines for the prevention of Malaria.

Prevention of Vector-borne Diseases

Vector-Borne diseases can be prevented in the following ways:

• Vaccines should be developed for protection against disease-causing viruses.
• Insect repellants such as DEET or Permethrin can be applied to the skin and clothes respectively.
• Tick checks should be performed after exposure to dogs, cats, cattle, and mice.
• Use nets while sleeping to protect against mosquitoes.
• Wash and dry clothes after an outdoor visit for a long time.
• Remove leaf litters and woodpiles from the surroundings.
• Do not let stagnant water accumulate in the surroundings.
• Use disinfectants to control infections caused by pests.

National Vector Borne Disease Control Programme

The National Vector Borne Disease Control Programme (NVBDCP) is an umbrella organisation for the prevention and control of the following six vector borne diseases – malaria, chikungunya, Japanese encephalitis, dengue, kala – azar and lymphatic filariasis. The agency is headquartered in New Delhi, India. The directorate of the NVBDCP provides the states with cash and commodities to implement policies for curbing these diseases.

What are Vectors?

• Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to humans.
• Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later transmit it into a new host, after the pathogen has replicated.
• Often, once a vector becomes infectious, they are capable of transmitting the pathogen for the rest of their life during each subsequent bite/blood meal.

Vector-borne diseases in India

• Vector-borne diseases are human illnesses caused by parasites, viruses and bacteria that are transmitted by vectors.
• The burden of these diseases is highest in tropical and subtropical areas, and they disproportionately affect the poorest populations.
• Since 2014, major outbreaks of dengue, malaria, chikungunya, yellow fever and Zika have afflicted populations, claimed lives, and overwhelmed health systems in many countries.
• Other diseases such as Chikungunya, leishmaniasis and lymphatic filariasis cause chronic suffering, life-long morbidity, disability and occasional stigmatisation.

Data related to Vector borne diseases

1. Vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700 000 deaths annually. They can be caused by either parasites, bacteria or viruses.
2. Malaria is a parasitic infection transmitted by female Anopheline mosquitoes. It causes an estimated 219 million cases globally, and results in more than 400,000 deaths every year. Most of the deaths occur in children under the age of 5 years.
3. Dengue is the most prevalent viral infection transmitted by Aedes mosquitoes – Aedes Aegyptus or Aedes Albopictus. More than 3.9 billion people in over 129 countries are at risk of contracting dengue, with an estimated 96 million symptomatic cases and an estimated 40,000 deaths every year.
4. Other viral diseases transmitted by vectors include chikungunya fever, Zika virus fever, yellow fever, West Nile fever, Japanese encephalitis (all transmitted by mosquitoes), tick-borne encephalitis (transmitted by ticks).
5. Other vector-borne diseases such as Chagas disease (transmitted by triatomine bugs), leishmaniasis (sandflies) and schistosomiasis (snails) affect hundreds of millions of people worldwide.
6. Many of vector-borne diseases are preventable, through protective measures, and community mobilisation.

List of vector-borne diseases, according to their vector

The following table is a non-exhaustive list of vector-borne disease, ordered according to the vector by which it is transmitted. The list also illustrates the type of pathogen that causes the disease in humans.

Global Vector Control Response (GVCR) 2017–2030 by WHO

• The "Global Vector Control Response (GVCR) 2017–2030" was approved by the World Health Assembly in 2017.
• It provides strategic guidance to countries and development partners for urgent strengthening of vector control as a fundamental approach to preventing disease and responding to outbreaks.
• To achieve this a re-alignment of vector control programmes is required, supported by increased technical capacity, improved infrastructure, strengthened monitoring and surveillance systems, and greater community mobilization.

Specifically WHO responds to vector-borne diseases by:

• providing evidence-based guidance for controlling vectors and protecting people against infection;
• providing technical support to countries so that they can effectively manage cases and outbreaks;
• supporting countries to improve their reporting systems and capture the true burden of the disease;
• providing training (capacity building) on clinical management, diagnosis and vector control with support from some of its collaborating centres; and
• supporting the development and evaluation of new tools, technologies and approaches for vector-borne diseases, including vector control and disease management technologies.
• A crucial element in reducing the burden of vector-borne diseases is behavioural change. WHO works with partners to provide education and improve public awareness, so that people know how to protect themselves and their communities from mosquitoes, ticks, bugs, flies and other vectors.
• Access to water and sanitation is a very important factor in disease control and elimination. WHO works together with many different government sectors to improve water storage, sanitation, thereby helping to control these diseases at the community level.

National Vector Borne Disease Control Programme

• It was launched in 2003-04 by merging National anti -malaria control programme, National Filaria Control Programme and Kala Azar Control programmes.
• Japanese B Encephalitis and Dengue/DHF have also been included in this Program.
• Directorate of NAMP (National Anti-Malaria Programme) is the nodal agency for prevention and control of major Vector Borne Diseases.

List of Vector Borne Diseases Control Programme Legislations:

1) National Anti - Malaria programme

2) Kala - Azar Control Programme

3) National Filaria Control Programme

4) Japenese Encephilitis Control Programme

5) Dengue and Dengue Hemorrhagic fever

1) NATIONAL ANTI - MALARIA PROGRAMME (NAMP)

• Malaria is one of the serious public health problems in India.
• At the time of independence malaria was contributing 75 million cases with 0.8 million deaths every year prior to the launching of National Malaria Control Programme in 1953.
• A countrywide comprehensive programme to control malaria was recommended in 1946 by the Bhore committee report that was endorsed by the Planning Commission in 1951.
• The national programme against malaria has a long history since that time. In April 1953, Govt. of India launched a National Malaria Control Programme (NMCP).

2) KALA -AZAR CONTROL PROGRAMME

• Kala-azar or visceral leishmaniasis (VL) is a chronic disease caused by an intracellular protozoan (Leishmania species) and transmitted to man by bite of female phlebotomus sand fly.
• Currently, it is a main problem in Bihar, Jharkhand, West Bengal and some parts of Uttar Pradesh.
• In view of the growing problem planned control measures were initiated to control kala-azar.

3) NATIONAL FILARIA CONTROL PROGRAMME

• Bancroftian filariasis caused by Wuchereria bancrofti, which is transmitted to man by the bites of infected mosquitoes - Culex, Anopheles, Mansonia and Aedes.
• Lymphatia filaria is prevalent in 18 states and union territories.
• Bancroftian filariasis is widely distributed while brugian filariasis caused by Brugia malayi is restricted to 7 states - UP, Bihar, Andhra Pradesh, Orissa, Tamil Nadu, Kerala, and Gujarat.
• The National Filaria Control Programme was launched in 1955.
• The activities were mainly confined to urban areas. However, the programme has been extended to rural areas since 1994.

4) JAPANESE ENCEPHALITIS CONTROL PROGRAMME

• Japanese encephalitis (JE) is a zoonotic disease and caused by an arbovirus, group B (Flavivirus) and transmitted by Culex mosquitoes.
• This disease has been reported from 26 states and UTs since 1978, only 15 states are reporting JE regularly. The case fatality in India is 35% which can be reduced by early detection, immediate referral to hospital and proper medical and nursing care. The total population at risk is estimated 160 million.
• The most disturbing feature of JE has been the regular occurrence of outbreak in different parts of the country.
• Govt. of India has constituted a Task Force at National Level which is in operation and reviews the JE situations and its control strategies from time to time. Though Directorate of National Anti-Malaria Programme is monitoring JE situation in the country.

5) DENGUE AND DENGUE HEMORRHAGIC FEVER

• One of the most important resurgent tropical infectious disease is dengue.
• Dengue Fever and Dengue Hemorrhagic Fever (DHF) are acute fevers caused by four antigenically related but distinct dengue virus serotypes (DEN 1,2,3 and 4) transmitted by the infected mosquitoes, Aedes aegypti.
• Dengue outbreaks have been reported from urban areas from all states.
• All the four serotypes of dengue virus (1,2,3 and 4) exist in India.
• The Vector Aedes Aegypti breed in peridomestic fresh water collections and is found in both urban and rural areas.