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Vector-borne diseases are illnesses caused by viruses, bacteria, and parasites that are transmitted to humans via vectors.
- Vectors are the living carriers responsible for transmitting pathogens from humans to animals and from one human to another.
- Diseases such as malaria, dengue, yellow fever, Chagas disease, etc are widely spread throughout the world.
What are Vector-borne diseases?
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Vector-borne diseases are infections caused by pathogens like viruses, bacteria, and parasites through a transmitting medium called a vector.
- Every year around 70,000 deaths occur because of such diseases.
- A majority of the transmitting medium are insects that suck on blood.
- They ingest the disease-causing microorganisms from an infected animal or human (host) and then transfer it to another host.
- Plaque, chikungunya, and Japanese encephalitis are some common examples of such diseases.
Types of Disease Vectors
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Different types of disease vectors carry different diseases. The table below shows the type of vectors, disease caused, and pathogen involved:
| Type of Vector | Disease Caused | Pathogen involved |
|---|---|---|
| Mosquito | Chikungunya | Virus |
| Dengue | Virus | |
| Lymphatic filariasis | Parasite | |
| Rift Vally Fever | Virus | |
| Yellow Fever | Virus | |
| Zika | Virus | |
| Aquatic snails | Schistosomiasis (bilharziasis) | Parasite |
| Blackflies | Onchocerciasis (river blindness) | Parasite |
| Fleas | Plague (transferred from rats to humans) | Bacteria |
| Lice | Typhus | Rickettsia prowazekii |
| Louse-borne relapsing fever | Borrelia recurrentis | |
| Sandflies | Leishmaniasis | Parasite |
| Sandfly fever (phlebotomus fever) | Virus | |
| Ticks | Crimean-Congo Haemorrhagic fever | Virus |
| Lyme disease | Bacteria | |
| Tick-borne encephalitis | Virus | |
| Relapsing fever (borreliosis) | Bacteria | |
| Tularaemia | Bacteria | |
| Rickettsial diseases (spotted fever and Q fever) | Bacteria |
Symptoms of Vector-borne diseases
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Based on the conditions of the disease-causing pathogens, the symptoms of vector-borne diseases also vary. The following are some signs of common vector diseases:
- Malaria: Jaundice, shivers, fever, body pain, diarrhea, pain in the chest, constant sweating, and coma (in severe cases).
- Chikungunya: Muscle and joint pain, quick fever, skin allergies, dizziness, nausea, and headaches.
- Yellow fever: Back pain, shivers, fever and headache, appetite loss, gastric bleeding (in severe cases), stomach ache, feeling of nausea, and jaundice.
- Dengue: High fever, headache, pain in eyeballs, muscle and joint pain, feeling of nausea and vomiting, lymph node swelling, and skin rashes.
- Zika virus: Mild symptoms like low fever, headache, muscle pain, and conjunctivitis.
- Plague: Pain and inflammation in the lymph nodes, difficulty in breathing, chest pain, cough, bloody sputum (in severe cases).
Vector-borne diseases in India
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Vector-borne diseases in India are very common, especially malaria resulting in around 2 million cases every year.
- According to the World Health Organisation, about three-quarters of the country accounts for malaria cases.
- Many cases have been recorded yearly in Northeastern regions and other states like Jharkhand, Chhattisgarh, Orissa, Karanta, West Bengal, Gujarat, Madhya Pradesh, and Andhra Pradesh.
- In most endemic states, vector-borne disease control projects have been implemented to control diseases.
- The project uses advanced technologies and medicines to control the spread of malaria.
Prevention of Vector-borne diseases
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There are various preventive measures and treatment methods. The following highlights the prevention of vector-borne diseases:
- Vaccines must be developed for protection against disease-causing viruses. Vaccination drives must be carried out in disease-prone areas.
- If a tick is present anywhere on the body, remove it immediately using tweezers and not by hand.
- Avoid contact with blood, secretions, and organs that are infected.
- Insect repellants must be used like DEET or permethrin.
- Remove any stagnant water from the surroundings as it is a breeding ground for mosquitoes.
- To control infections caused by pests, use disinfectants.
- Use nets while sleeping to protect yourself from mosquito bites.
- Eat hygienic and properly cooked food.
- Wash yourself thoroughly after outdoor visits.
Things to Remember
- Vector-borne diseases are caused by blood-sucking pathogens like ticks and mosquitos.
- Malaria is one of the most common diseases accounting for 219 million cases globally.
- Bubonic plague is an infectious disease that affects the lymphatic system.
- Tsetse flies are the parasites that cause sleeping sickness.
- Most of the vector diseases can be prevented and treated.
Sample Questions
Ques. How does malaria differ from chikungunya with reference to their vectors? (1 Mark)
Ans. Malaria is spread by the vector, i.e. Anopheles mosquito, whereas chikungunya is spread by the vector, i.e. Aedes
Ques. Name the common vector borne disease? (1 Mark)
Ans. The two most common vector borne diseases include malaria and dengue fever.
Ques. What are the diseases caused by the vector sandflies? (1 Mark)
Ans. Diseases that are caused by sandflies include leishmaniasis, and Phlebotomus.
Ques. What is a vector? (1 Mark)
Ans. Any pathogen that carries and transmits diseases and infections from one host to other host is called a vector. These vectors may be parasites or other microbes.
Ques. How to control mosquitoes and diseases caused by them? (2 Marks)
Ans. By controlling mosquitoes, diseases caused by them will also be controlled. Mosquitoes can be controlled by decreasing or reducing the number of breeding sites, removing algae from the ponds, and using mosquito repellents.
Ques. What is the project implemented in India to control vector borne diseases? (2 Marks)
Ans. Vector borne disease control project supported by the World Bank has been implemented in India to control diseases. The project uses modern and advanced medicines and technologies to control vector borne diseases.
Ques. Study a part of the life cycle of malarial parasite given below. (3 Marks) [Delhi 2012]
(i) Mention the roles of A in the life cycle of the malarial parasite.
(ii) Name the event C and the organ where this event occurs.
(iii) Identify the organ B and name the cells being released from it.
Ans. (i) A is female Anopheles mosquito, these mosquitoes act as vectors and transmit the disease from patients to healthy individuals.
(ii) The event C is fertilisation. It occurs in the intestinal wall of mosquitoes.
(iii) B is salivary glands, sporozoites cells are released from it.
Ques. What are vector borne diseases? (3 Marks)
Ans. Vector borne diseases are the illnesses caused by infections transmitted by infection carriers called vectors. These vectors include ticks, mosquitoes and fleas. These vectors carry different infection-causing microorganisms like viruses, bacteria, and protozoa and transfer these infection-causing pathogens from one host to another. This vector borne diseases cause a significant number of illnesses and deaths every year over the world.
Almost everyone has been bitten by a mosquito, tick, or flea. Vectors are mosquitoes, ticks, and fleas that spread pathogens. A person who gets bitten by a vector and gets sick has a vector-borne disease. Some vector-borne diseases, like plague, have been around for thousands of years. Others, like Heartland virus disease and Bourbon virus disease, have been discovered recently.
Ques. The National Vector Borne Disease Control Programme does not cover which of the following disease (4 Marks)
(A) Dengue
(B) Polio
(C) Malaria
(D) Filaria
Ans. There are various infectious diseases that are caused in humans with the help of vectors like mosquito, house fly, fleas, louse etc. These vector borne diseases are malaria, dengue, filaria, kala-azar, Japanese encephalitis, Chikungunya, etc. National Vector borne Disease Control Programme is an agency made by the Ministry of Health and Family Welfare, Government of India for the control and prevention of the above six vector borne diseases.
Option A: Dengue is a disease caused by dengue virus. It spreads from infected person to an uninfected person through infected Aedes aegypti mosquito.
Option B: Polio is also a viral disease caused by poliovirus in children. It spreads through droplets of sneezing, cough and by the contact of faces of infected people.
Option C: Malaria is a disease caused by protozoan parasites, like plasmodium. It is transmitted through the bite of an infected Anopheles mosquito.
Option D: Filaria is caused by roundworms or nematodes like Wuchereria bancrofti. It is transmitted from an infected person to a non-infected person through the bite of an infected mosquito.
Thus, dengue, malaria and filaria are transmitted from an infected person to an uninfected person by vectors like mosquito and only polio is not transmitted through vectors. Hence, polio is not a Vector Borne Disease and it is not included in the National water Borne Disease Control Programme.
Hence, the correct answer is option (B).
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