Vector-Borne Diseases (VBD): Types, Prevention & Control

What are Vector-Borne Diseases (VBDs)?

Vector-borne diseases are infections transmitted to humans and other animals by blood-feeding arthropods.
Vectors are the organisms that transmits or carries pathogens from one host to another.
Vector-borne diseases are human ailments initiated by parasites, viruses, and bacteria that are spread by mosquitoes, sandflies, triatomine bugs, blackflies, ticks, tsetse flies, mites, snails and lice.
Every single year there are over 700,000 deaths from illnesses such as malaria, dengue, schistosomiasis, human African trypanosomiasis, leishmaniasis, Chagas disease, yellow fever, Japanese encephalitis, and onchocerciasis, universally.
Some of the common vectors are:
- Mosquitoes
- Ticks
- Sandflies
- Tsetse flies
- Blackflies etc.

Major Vector-Borne Diseases

1. Malaria

Pathogen: Plasmodium parasite, mainly P.falciparum and P.Vivax
Vector: Anopheles mosquito

2. Dengue

Pathogen: Dengue Virus
Vector: Aedes aegypti and aedes albopictus

3. Zika virus

Vector: Aedes mosquito
Symptoms: mild fever, joint pain, rashes

4. Chikungunya

Vector: Aedes mosquito
Symptoms: Joint pain and fever

5. Yellow fever

Vector: Aedes and haemagogus mosquito

6. Lieshmaniasis

Pathogen: Leishmania parasite
Vector: Sandfly

7. Lyme disease

Pathogen: Borrelia burgdorferi bacteria
Vector: Ixodes ticks

8. Japanese Encephalitis

Vector: Culex mosquito

Transmission Cycle of Vector-Borne Diseases

Reservoir host (eg: humans, birds and animals)
Vector (eg: mosquito or tick)
Susceptible human host

Risk Factors of Vector-Borne Diseases

Environmental factors: temperature, humidity, rainfall, deforestation, urban slums
Socioeconomic factors: poor sanitation and cleanliness, inadequate waste disposal
Migration, tourism and global mobility: carries the vectors to different places
Climate change
Unplanned and uncontrolled urbanization
Increased human-animal interaction
Resistance to insecticides

Classification of Vector-Borne Diseases

VBD are broadly divided into four branches:

1. Arboviral Diseases Branch

It emphasizes on viruses transmitted through mosquitoes and ticks. This branch is accountable for viruses like chikungunya, West Nile, yellow fever, and Zika.

1.1 Chikungunya virus

It spreads to people through the bite of an infected mosquito.

Symptoms

Fever
Joint pain
Headache
Muscle pain
Joint swelling/ rash.
There is a possibility that the virus will be brought in to new regions via diseased explorers.
There is certainly no vaccine to avert or remedy to treat chikungunya virus infection.

1.2 West Nile virus (WNV)

It is a prominent source of mosquito-borne disease in the central United States.

It is most frequently transmitted to people through the bite of an infested mosquito.
Circumstances of WNV arise throughout mosquito season that begins in the summertime and lasts over fall.
There are no vaccines to inhibit or prescriptions to treat WNV in individuals. Luckily, the utmost people sick with WNV do not sense sickening.
About 1 in 5 people who are diseased, progress a malaise and additional symptoms.

1.3 Yellow fever virus

It has prevailed in tropical and subtropical parts of Africa and South America.

Transmission

Through infected mosquito bite
Illness varies from a fever thru headaches and discomforts to unadorned liver disease with hemorrhage and yellowing skin (jaundice).

Diagnosis

Centered on laboratory testing, an individual’s signs, and travel history. There is no medication to treat or cure contagion.

1.4 Zika virus

Zika virus spreads typically by the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus).

Zika can be conceded from a pregnant woman to her fetus. Infection throughout pregnancy can initiate certain birth deficiencies.

There is no vaccine or medication for Zika

2. Bacterial Diseases Branch

It emphases on bacteria caused by ticks and fleas. This branch is liable for bacteria like Lyme disease, plague, and tularemia.

2.1 Lyme disease

It is initiated by the bacterium Borrelia burgdorferi and is transferred to humans through the bite of infested black-legged ticks.

Symptoms

Fever
Headache
Fatigue
A distinguishing skin rash termed erythema migrans. If left untreated, septicity is able to spread throughout the joints, the heart, also the nervous system.

Diagnosis

Based on the warning sign
Laboratory testing is useful if castoff appropriately and implemented with authorized methods.
Most cases of Lyme disease can be cured productively with limited use of antibiotics.

Prevention

Via insect repellent
Eliminating ticks quickly
Applying pesticides
Decreasing tick habitation. The ticks that transfer Lyme disease can sporadically transfer other tick-borne diseases also.

2.2 Plague

Plague is a disease that affects the human being and other mammals.

It is initiated by the bacterium, Yersinia pestis. Plague is ill-reputed for slaying masses of people in Europe through the Middle Ages.

Currently, human plague infections remain to befall in the western United States, nevertheless considerably, more cases happen in parts of Africa and Asia.

Prevention

Lessen rodent habitation around the house, workplace, and leisure regions.
Practice repellent if there is a chance to be exposed to rodent fleas throughout the activities, for example sleep out, trekking, or working outdoors.

2.3 Tularemia

It is a disease that can pass on an infection to animals and people. Rabbits, hares, and rodents are specifically vulnerable and repeatedly expire in great numbers thru outbreaks. People can turn out to be diseased in numerous ways, containing:

Tick and deer fly bites
Skin contact with infected animals
Symptoms differ dependent on how the person was diseased.

Tularemia can be life-threatening, however, most contagions can be cured effectively with antibiotics.

Prevention

By insect repellent
Wearing gloves while holding sick or dead animals
Evading mowing over dead animals

3. Dengue Branch

It emphases on the four dengue viruses spread by mosquitoes.
Dengue viruses are transmitted to people through the bite of an infected Aedes species (Ae. aegypti or Ae. albopictus) mosquito.
One of any of four interconnected viruses causes dengue: Dengue virus 1, 2, 3, and 4. Therefore, an individual can be diseased with a dengue virus four times in his or her lifespan.

Prevention

Avoid mosquito’s bites
Use insect repellent
Receiving vaccine (Dengvaxia)

4. Rickettsial Zoonoses Branch

Emphases on a distinct category of bacteria mainly spread by ticks, lice, and fleas and bacteria like Q fever, Rocky Mountain spotted fever and typhus fevers.

4.1 Q fever

It is a disease triggered by the bacteria Coxiella burnetii.

Transmission

Inhalation of dust that has been tainted by diseased animal feces, urine, milk, and birth products

Prevention

Lessen the risk of getting Q fever by dodging interaction with animals, particularly while animal delivery.
Do not consume uncooked milk or raw milk products.
Antibiotic treatment

4.2 Rocky Mountain spotted fever (RMSF)

It is a bacterial disease spread through the bite of an infected tick. Majority of people suffering from RMSF will have a fever, headache, and rash. RMSF can be fatal if not cured promptly with the correct antibiotic.
There is no vaccine to avert RMSF. Inhibit illness by averting tick bites, and similarly on your pets.

4.3 Typhus fevers

It are a set of diseases instigated by bacteria that are transmitted to human being thru fleas, lice, and chiggers. Typhus fevers consist of scrub typhus, murine typhus, and epidemic typhus.

Symptoms

Fever
Headaches
Mental changes, ranging from confusion to coma
Enlarged lymph nodes
No vaccine to prevent epidemic typhus.

Prevention

Reduce the risk of getting c typhus by avoiding overcrowded areas
Can be treated with the antibiotic doxycycline. Antibiotics are operational when given quickly after signs originate.
Spray insect repellent
Treat apparel and gear with permethrin

Prevention and Control Strategies of Vector-Borne Diseases

Use of insecticides
Destroying the breeding sites of vectors
Use of insecticide-treated nets (ITNs) and repellents
Introducing natural predators and pathogens
Regular use of vaccination for VBD like yellow fever, Japanese Encephalitis and dengue
Continuous surveillance through strong surveillance systems
Use of GIS and remote sensing techniques for mapping high-risk zones
Health education and community awareness
Community engagement activities for disease prevention and removal of breeding sites of vectors
Adopting ‘One Health Approach’ for united actions
Research and investment in Integrated Vector Management (IVM) to control VBDs