2.2: Modes of Transmission

Question 1

Three ways disease can be transmitted

Answer 1

• Contact transmission: airborne droplets, sexual contact, direct contact
• Vehicle transmission: food and waterborne, carried in blood
• Vector transmission: anthropod borne

Question 2

Contact Transmission

Answer 2

• Pathogens may be spread by contact with other infected humans or animals through droplet transmission, indirect contact or direct contact
• Droplet transmission: mucus droplets carrying disease are discharged through: coughing, sneezing, laughing, talking
• Indirect Contact: through touching contaminated objects: eating utensils, drinking cups, bedding, money, used syringes
• Direct contact: direct transmission of an agent between its source and a potential host: touching, kissing, sexual intercourse

Question 3

Vector Transmission

Answer 3

• Many pathogens have more than one host. Intermediate host may transmit the pathogen to its primary host
• Bites from a variety of animals can carry pathogens:
• Fleas: Carried by many animals, reponsible for the spread of many bacterial disease (e.g bubonic plague)
• Rodents: Rodes carry hantaviruses, infection occurs when humans contact with rodent droppings
• Mosquitoes: ANopheles gambiae, name for the tropic mosquito, a vector for malaria parasite
• Ticks The der tick transmits Lyme disease from wild mammals to humans
• Fruit bat: Hendra viruses are transmitted in the droppings of fruit bats
• Foxes: Rabies is transmitted in bites from infected foxes and other mamals such as dogs

Question 4

Vehicle Transmission

Answer 4

• Disease may be transmitted through a medium such as blood, water, food, or air. Blood-borne, water-borne etc.

Question 5

Waterborne Disease

Answer 5

• Generally associated with regions of poor sanitation, and hygiene infrastructure. Typically where faecal matter is present in the water supply
• Hepatitis B and meningococcal disease can be spread by sharing drink bottles
• For example: Typhoid fever, cholera, hepatitis B

Question 6

Food-borne Disease

Answer 6

• Occurs when food is not cooked properly, or inadequately stored, or prepared in an unsanitary environment
• For example: Bacterial food poisoning: salmonellosis and hydatids

Question 7

Blood-borne disease

Answer 7

• Blood-borne disease are transmitted when bodily fluids from two mammals are mixed and one is infected
• For example: HIV/AIDS, Hepatitis B, Hepatitis C