Vector-Borne Diseases | Zoology Optional Notes for UPSC PDF Download

Vector-Borne Diseases

What are the vectors?

Vectors are organisms that transmit pathogens and parasites from an infected person (or animal) to another.

What are vector-borne diseases?

Vector-borne diseases are diseases caused by vectors, and are often found in tropical areas where insects are abundant and in places where it is difficult to access safe drinking water and sanitation systems.

How serious is vector-borne disease?

Vector-borne diseases are among the most serious and unpredictable. Protection and control are extremely difficult since infection can return even after treatment because the organisms are inherent in the environment where they are spreading. The seriousness of vectors lies in their ability to transmit the disease on a larger scale and faster than other diseases that require human-to-human contact to be transmitted. They also transmit the disease from different organisms (mice, rats, monkeys, birds, dogs, etc.) to humans and facilitate the spreading of the micro-organisms which cause serious diseases. The treatment of such diseases is difficult and protection requires the elimination of the vector.

Types of vectors:

• Mosquitoes
• Flies (sand fly and black flies)
• Tick
• Bugs
• Snail carrying parasites

Possible places of presence of disease vectors:

• Pots and ponds with stagnant water and swimming pools
• Rainwater gathering places such as parks' toys
• Abandoned places and equipment
• Open water tanks in the bathroom or kitchen
• Flower pots with stagnant water
• Rodent burrows and dark places
• Stagnant water due to air conditioning and ventilation holes
• Stagnant water on the roofs of buildings
• Swimming pools, ponds, and swamps, especially in agricultural areas
• Animal husbandry sheds
• Beds and unclean sleeping areas may be a bunk.

Preventive measures to protect against vectors:

• Control insect vectors and the locations of their larvae by spraying with appropriate pesticides.
• Backfill ponds and marshes and dispose of waste to prevent accumulation.
• Wear long-sleeved clothes, cover the legs in places infested with insects, and apply insect repellents to the skin and clothing.
• Make sure to place mesh nets with tiny holes on all windows and doors to prevent insects from coming in.
• Use a mosquito net if you are planning to sleep outside.
• Cover water tanks tightly.
• Remove potential water-gathering areas such as old tires, planting basins, and generally unused equipment.
• When spending a long time out of the house, close the toilet cover, siphon cover, drainage holes, and drains.
• Change the water in flower pots every two days and clean the pots from the inside.
• Remove stagnant water in drainage channels above the roof and in the garden.
• Change the water in animal pots every two days.
• Avoid traveling to places where insect-borne diseases are common and be sure to receive vaccines or medicines to prevent them in case of travel such as yellow fever or malaria.
• Check sleeping places such as beds, bed linen, and mattresses, especially in hotels, to avoid bugs.
• Pay attention to the cleanliness of barns and cattle where breeding takes place.
• Dry the skin thoroughly after exposure to water in endemic areas.
• Do not swim in ponds or stagnant water, and do not defecate there at all.
• Control snails carrying the infectious phase of schistosomiasis.
• Always maintain personal hygiene and use pure water to drink or shower.
• Dispose of human waste away from water sources.

Vector-borne disease groups

What is mosquito?

It is one of the most important insect vectors in humans, where it infects diseases due to transmission of viruses and parasites.

How does a mosquito transmit diseases?

When a mosquito carrying viruses, parasites, or worms (microorganisms) that cause diseases bites a person, it transmits them into the body by injecting the microorganisms' saliva into the skin.

Main mosquito-borne diseases:

• Malaria
• Dengue Fever
• Yellow fever
• Chikungunya disease
• Elephantiasis

Identification and characteristic symptoms of mosquito-borne diseases:

Malaria

Malaria is a mosquito-borne disease caused by a parasitic organism called plasmodium. Symptoms include frequent attacks of fever and chills, sweating, headache, nausea and vomiting, and diarrhea.

Dengue Fever

It is a viral disease transmitted by a type of mosquito known as the Egyptian Aedes aegypti. Symptoms include fever, severe headache, severe pain behind the eye, joint and muscle pain, skin rash, and symptoms of bleeding from the nose or gums or spots under the skin.

Yellow fever

A viral disease transmitted by a particular type of mosquito that spreads in the tropics of Africa and South America. Symptoms include fever, headache, muscle pain especially in the back and knees, nausea and vomiting, redness of the eyes, face or tongue, jaundice, bleeding from the nose, mouth, and eyes, irregular heartbeats, liver and kidney failure, and brain dysfunction.

Chikungunya disease

Chikungunya is a viral disease that is spread by mosquitoes and spreads in Africa, Asia, and the Indian subcontinent. Symptoms include sudden fever with severe joint pain that often leads to significant disability of the human, muscle pain and headaches, and skin rash.

Elephantiasis

A syndrome caused by nematodes attacking the lymphatic system, leading to swelling and accumulation of tissues in different areas of the body, especially in the legs and limbs. Elephantiasis often does not cause death but can cause disability. Symptoms vary from asymptomatic to acute and chronic symptoms.

Treatment

Treatment for mosquito-borne diseases depends on the specific disease and may include medications to control symptoms and eliminate the infection.

Prevention of Mosquito-borne diseases:

• Control mosquito populations by eliminating breeding sites and using appropriate pesticides.
• Take measures to protect yourself from mosquito bites, such as wearing long-sleeved clothes, covering the legs in places infested with insects, and applying insect repellents to the skin and clothing.
• Use mesh nets with tiny holes on all windows and doors to prevent insects from coming in.
• Use a mosquito net if sleeping outside.
•  Avoid traveling to places where insect-borne diseases are common and be sure to receive vaccines or medicines to prevent them in case of travel.
• Ensure proper hygiene and cleanliness to reduce the risk of mosquito breeding.

Fly-borne diseases

Types of flies carrying infectious diseases:

• Sand fly: Transmits the parasite that causes leishmaniasis.
• Black flies: Transmits the parasite that causes river blindness.
• Tsetse fly: Transmits the parasite that causes African trypanosomiasis.

Leishmaniasis:

Leishmaniasis is an infectious disease transmitted to humans by various types of parasites. It can manifest as dermal, visceral, or mucous membrane leishmaniasis with varying symptoms.

River blindness:

River blindness is caused by nematode infection transmitted by black flies. Symptoms include severe itching, changes in skin color, appearance of nodes and clumps under the skin, and damage to internal organs.

African trypanosomiasis:

African trypanosomiasis, also known as sleeping sickness, is a parasitic disease transmitted by tsetse flies. It has two stages, the lymphatic stage and the neurological stage, with symptoms including fever, headache, sleep disorders, and neurological problems.

Treatment:

Treatment for fly-borne diseases depends on the specific disease and may include medications to control symptoms and eliminate the infection.

Prevention of fly-borne diseases:

• Take precautions when in areas where flies are common, such as wearing protective clothing and using insect repellents.
• Control fly populations by eliminating breeding sites and using appropriate pesticides.
• Maintain cleanliness of pets and surroundings to reduce the risk of fly infestation.

Tick-borne diseases

What is tick?

A tick is an insect that sucks the blood of animals and can transmit diseases by transferring infected blood from one creature to another.

Main tick-borne diseases:

•  Lyme disease
• Crimean fever

Lyme disease:

Lyme disease is transmitted by tick bites and is caused by a type of bacteria. Symptoms include flu-like symptoms, skin rash, joint pain, and disorders in the nervous system.

Crimean fever:

Crimean fever is a disease transmitted by tick bites and is caused by a virus. Symptoms include fever, headache, back and joint pain, stomach pain and vomiting, eye infections, and bleeding.

Treatment:

Treatment for tick-borne diseases depends on the specific disease and may include medications to control symptoms and eliminate the infection.

Prevention of tick-borne diseases:

• Avoid areas where ticks are common.
• Use insecticide-treated clothing in areas where ticks are common.
• Check for ticks on the body after being in tick-infested areas and remove them properly.
• Use repellents on clothing and skin to deter ticks.

Bug-borne diseases

What are bugs?

Bugs are large nocturnal insects that can be found in buildings with thatched roofs. Their bites are painless but they leave contaminated stools near the wound.

Main Bug-borne diseases

- Chagas disease

Chagas disease:

Chagas disease is caused by a parasitic worm transmitted by bug bites. Symptoms include fever, swelling of the eyelid, swelling at the bite site, and damage to the heart, intestines, and other organs.

Treatment:

Treatment for Chagas disease focuses on eliminating the parasite and managing symptoms. Antiparasitic drugs are commonly used.

Prevention of Chagas disease:

• Avoid sleeping in houses with thatched roofs.
• Use insecticides to remove bugs from the living environment.
• Use insect repellents to prevent bug bites.

Diseases transmitted by helminths

The most important diseases transmitted by snails:

Bilharzia

Bilharzia, also known as schistosomiasis, is a disease caused by parasitic worms. Infection occurs when the skin is exposed to fresh water containing snails that transmit the worms. Symptoms include rash, fever, cough, and damage to the liver, intestines, and bladder.

Treatment

Treatment for bilharzia depends on the specific type of parasite and may include antiparasitic medications.

Prevention of bilharzia

• Avoid swimming in fresh water where snails are present.
• Practice good hygiene and avoid contamination of water sources.
• Use safe water sources for drinking and bathing.