Mechanical vs. Biological Transmission

Introduction to Vectors

Vectors: Animals that carry a pathogen from one host to another.
Common vectors: Flies and mosquitoes, but can include larger animals like mammals.

Definition: Pathogens are carried on the body of a vector.
Example: A fly lands on fecal material, picks up bacteria, and then transfers it to food.
- Consumption of contaminated food can cause illness.
Diseases Spread Mechanically:
- Shigellosis (bacillary dysentery) via infected fecal material on food.
- Typhoid fever.
- Diarrhea and dysentery diseases.

Definition: More complex than mechanical; involves the vector being part of the pathogen’s life cycle.
Mechanism:
- Vector is infected and transmits the pathogen through saliva or fecal matter.
Examples:
- Mosquitoes and Malaria:
  - Malaria parasite in mosquito’s salivary glands.
  - Transmitted to humans through bites.
  - Parasite spreads in human blood and can be picked up by another mosquito.
- Ticks and Lyme Disease: Transmission through tick bites.
- Lice and Typhus: Transmission through lice bites.
- Mammals and Rabies: Transmission through bites, with rabies virus in saliva.

Salivary Glands: Pathogens reproduce before being transmitted through bites.
Gut: Pathogens reproduce before being transmitted through fecal matter.
- Insects might defecate when biting, allowing pathogens into the host through the bite wound.

Understanding the differences between mechanical and biological transmission is crucial for preventing disease spread.
Various diseases are associated with each type of transmission, highlighting the importance of controlling vector populations and mitigating exposure.

End of Notes on Dr. O's lecture on Mechanical vs. Biological Transmission