What Are Vector-Borne Diseases?

Medically Reviewed by Dany Paul Baby, MD on November 07, 2022
Written by Venkat S.R.
5 min read

Vector-borne diseases are caused by the bites of disease-causing pathogens like mosquitoes and ticks. This article looks at the different types of vector-borne diseases and their symptoms, causes, and possible treatment options.

Vectors are lifeforms that act as a medium for transmitting infectious germs from animals to humans — and in some cases, between humans. These organisms first get infected by the disease-causing pathogens, and once infected, they can transmit the pathogen to humans throughout their life whenever they come in contact with a human host. Diseases transmitted through such vectors are called vector-borne diseases. Some vector-borne disease examples are:

Vector-borne diseases cause roughly 700,000 deaths worldwide every year. Vectors can carry different types of pathogens, including viruses and bacteria. Tropical and subtropical regions report large numbers of vector-borne diseases that typically affect people living in poorer areas. Diseases like chikungunya and leishmaniasis could cause permanent disabilities and lead to social stigma.

Vector-borne diseases are caused by the bite of infected insects like mosquitoes, ticks, and sandflies, which act as carriers. Most of these vectors are insects that suck human blood, which is when pathogen transmission occurs. These vectors first ingest a disease-causing pathogen from an already-infected host (an animal or human) and transmit it to other humans during subsequent blood meals. Insects from the arthropod species, like mosquitoes, ticks, triatomine bugs, sandflies, and blackflies, typically transmit vector-borne diseases.

The spread of vector-borne diseases depends on several factors, like the environment in which it breeds, population density in the region, and frantic urbanization. You’re at greater risk of getting a vector-borne disease in areas where the vectors thrive, like still water bodies, tall grass growth, and regions that report large outbreaks.

Vector-borne diseases happen due to the action of specific pathogens and vectors. Some vector-borne diseases, their disease-causing pathogens, and their vectors are listed below.

  • Chikungunya, dengue, yellow fever, and Zika. Caused by a virus carried by the Aedes mosquito
  • Malaria. Caused by a parasite carried by the female Anopheles mosquito
  • Japanese encephalitis and West Nile fever. Caused by a virus transmitted by the Culex mosquito
  • Chagas disease (American trypanosomiasis). Caused by a parasite transmitted by Triatomine bugs
  • Sleeping sickness (African trypanosomiasis). Caused by a parasite carried by Tsetse flies
  • Leishmaniasis. Caused by a parasite carried by sandflies
  • Typhus. Caused by bacteria transmitted by lice
  • Plague. Caused by bacteria transmitted by fleas (transmitted from rats to humans)
  • Crimean-Congo hemorrhagic fever. Caused by a virus transmitted by ticks
  • Lyme disease. Caused by bacteria transmitted by ticks

Symptoms of vector-borne diseases vary depending on the condition and the disease-causing pathogen. Some signs of widely reported vector-borne diseases are as under:

  • Chikungunya. Symptoms include sudden fever, joint pain, muscle aches, headaches, nausea, fatigue, and skin rashes. Joint pain can last for weeks.
  • Dengue. Common symptoms include sudden high fever (that can sometimes reach 39°C or 40°C), along with severe headache, pain behind the eyeballs, muscle pain, joint pain, nausea, vomiting, swollen lymph nodes, and rashes.
  • Yellow fever. Fever, muscle pain (especially in the back), chills, headaches, loss of appetite, and nausea are typical symptoms, which usually disappear after three to four days. Sometimes remission may happen, along with high fever, leading to a dangerous phase with severe symptoms like gastric bleeding, jaundice, dark-colored urine, abdominal pain, and vomiting. Of the cases that enter the dangerous phase, 50% are fatal.
  • Zika virus. Most people don’t have any symptoms. Only 20% of the people show mild symptoms like low fever, conjunctivitis, headache, joint stiffness, muscle pain, and pain behind the eyes. In some cases, it can trigger other neurological conditions like Guillain-Barré syndrome.
  • Malaria. Symptoms include fever, chills, sweating, headache, nausea, body aches, diarrhea, vomiting, breathing issues, and chest pain. Severe malaria cases could lead to jaundice (yellowing of the skin and the white part of your eyes) and sometimes a coma.
  • Japanese encephalitis. Initial symptoms in adults include fever, headache, and vomiting. Neurological symptoms, weakness, and movement issues could develop after a few days. Children usually get seizures, and 20% to 30% of people who report brain infections die.
  • West Nile fever. Some symptoms include fever, headache, fatigue, body aches, nausea, enlarged lymph glands, and skin rashes (in some cases). Usually, 1 out of 150 cases becomes severe, causing neck stiffness, coma, tremors, and paralysis.
  • Plague. Bubonic plague affects the lymph nodes, causes inflammation and pain, and fills the sores with pus. When the infection spreads to the lungs, it’s called pneumonic plague. Signs of this phase include pneumonia with shortness of breath, chest pain, cough, and in some cases, bloody sputum.
  • Typhus. High fever, headache, chills, coughing, severe muscle pain, and fatigue are common symptoms.

Viral vector-borne diseases can’t be treated. Parasitic infections, like those that cause malaria, can be treated using drugs like quinone, which kills the parasite or prevents its growth. Antibiotics like doxycycline and chloramphenicol treat bacterial infections like plague.

You can take some precautions to prevent vector-borne diseases:

  • Vaccines are available to prevent vector-borne diseases like yellow fever, Japanese encephalitis, and tick-borne encephalitis.
  • Identify whether the location you’re traveling to has reported vector-borne disease outbreaks. If so, ask your doctor what precautions you should take before you travel.
  • Make sure there’s no stagnant water where you live, as this is a breeding ground for many vectors.
  • Cover your body from head to toe to reduce the likelihood of being bitten by insects and bugs. Apply insect repellents on unprotected skin before going outside.
  • Avoid touching infected people or animals' blood or fluids.
  • Make sure the food you eat is hygienic. This includes the pans you use for cooking and where you store the food.
  • If you find a tick on your body, don’t remove it with your hand. Use tweezers and clean the area with a disinfectant right away. If you’re returning home after traveling to a region that reported a vector-borne disease, make sure you don’t accidentally bring in a bug. Check your clothing, luggage, and other belongings carefully before you enter your house.
  • Get vaccinated against all the diseases in your area.
  • Vector-borne diseases make up more than 17% of all infectious diseases caused by bacteria, viruses, and parasites.
  • There are 219 million cases of malaria reported worldwide, which lead to more than 400,000 deaths each year.
  • There are roughly 129 countries in the world where dengue is prevalent. It causes 96 million cases and leads to 40,000 fatalities annually.