Vector Borne Diseases

Mammals, birds, arthropods and insects all have the potential to transmit disease to humans. Pests that transfer diseases are referred to as a vector.

The vector picks up the disease organism from an infected host, an animal or a human, and transmits it either to an intermediary host or directly to the human host. The transfer happens directly by bites, stings, or infestation of tissues, or indirectly through disease transmission. Mosquitoes and ticks are the most notable disease vectors because the most significant mode of transmission is through blood-feeding.

The table below provides example of important vectors with the diseases they are capable of transmitting.

Vectors	Diseases
Learn more about the Aedes Mosquito	Chikungunya Dengue Virus West Nile Virus Yellow Fever
Learn more about the Anopheles Mosquito	Malaria
Learn more about Birds	Avian influenza (Bird flu)
Learn more about Fleas	Bubonic Plague
Learn more about Rats	Leptospirosis Plague (via Fleas) Leishmaniasis (via Sand Fly)
Learn more about Sand Flies	Leishmaniasis
	Lyme Disease
	Chagas Disease
	Human African Trypanosomiasis (Sleeping Sickness)

Vector borne diseases are prevalent in the tropics and subtropics and are relatively rare in temperate zones, although climate change could create conditions suitable for outbreaks of diseases in temperate regions.

Nearly half of the world's population is infected by vector-borne diseases, resulting in high morbidity and mortality. Unfortunately, vector borne diseases are re-emerging and form an increased risk. This is through for all the disease above, and recent examples in support hereof are:

• Dengue fever infections are estimated at 50 million per annum. Endemic in more than 100 countries (before 1970 only 9 countries) ¹
• Leptospirosis incidence rates rising globally – 600,000 pa ¹
• 350-500 million cases of malaria reported each year ²
• Lyme disease cases doubling every year in the USA ³

There are multiple reasons for the worldwide emergence or resurgence of vector borne diseases.

• The withdrawal of more effective insecticides (like DDT) in combination with the development of insecticide resistance have led to an increase of vectors
• An unprecedented growth in population and uncontrolled expansion of urban areas in combination with deforestation means that we are moving into the natural pest habitats; pests find ideal alternative breeding areas in human made constructions
• Governments have decreased resources for surveillance, prevention and control of vector borne diseases and the public health infrastructure required to deal with these diseases has deteriorated
• Globalisation and increased international travel and transport allow infestations to quickly spread
  

Sources:

1. WHO
2. CDC
3. Medical College of Wisconsin