Role of Vectors Lesson 4 Unit Diseases Mrs

Role of Vectors Lesson 4 Unit: Diseases Mrs. Kalicharan

Define vector? �Vectors are organisms that transmit diseases by carrying pathogens from person (host) to person (host). �Pathogenic diseases are therefore transmitted by vectors. �Pathogens (disease- causing organism) cause the host to become sick or diseased. �A pathogen consists of viruses, bacteria,

Transmission of pathogens

Transmission of pathogens �Vectors may carry a pathogen either inside or outside of its body. �For example, mosquitoes carry the pathogen for malaria and dengue fever inside their bodies.

Vectors that carry pathogens inside its bodies �Vectors that carry pathogens inside its bodies, acts as a second host in which the pathogen has to complete part of its life cycle. �Transmission may be by saliva during biting or by regurgitation or deposition on the skin (the pathogen penetrates into the body when the host rubs or scratches the skin.

Vectors that carry pathogens outside its body �For example, flies carry the pathogens for cholera, typhoid and gastroenteritis on the outside of their bodies. �When flies walk or crawl on contaminated material, mainly faeces, pathogens becomes attached to hairs or sticky pads on the feet.

Vectors that carry pathogens outside its body �These pathogens are then deposited on food as the flies walk on the food. �Alternately, the pathogens may pass through the vector digestive tract and be deposited on the food in its faeces or saliva.

Examples of diseases vectors carry Vector Mosquitoes Flies Rats Examples of disease(s) spread Yellow fever, dengue, malaria and chikungunya Gastroenteritis, cholera, typhoid fever Leptospirosis

Rat flea This vector carries the pathogen that caused the plague in the 14 th century and killed 25 million people in Europe. The plague is spread when the flea feeds on an infected rodent and