How Diseases and Parasites are Spread
4-H Veterinary ScienceExtension Veterinary Medicine
Texas AgriLife Extension ServiceCollege of Veterinary Medicine and Biomedical Science
Texas A&M Systemhttp://aevm.tamu.edu
Objectives
Discuss the spread of infections by direct means
Discuss the spread of infections by direct means
Discuss the spread of infections by indirect means
Describe the methods by which parasites are spread
Discuss sources of disease
Direct vs. Indirect Transmission
Direct transmission Direct or close contact
Indirect transmission Vectors Vehicles Fomites
Sources
A. Carrier/reservoir animals1. Aerosol droplets 8. Milk
2. Nasal fluid 9. Fetal fluid
3. Ocular fluid 10. In utero
4. Saliva 11. Genital fluid
5. Skin 12. Blood
6. Manure 13. Carcass
7. Urine
Vehicles (not alive)
Instruments Needles Ear tagger Tattooer Dehorner Nose tong Knife
Utensils Buckets Troughs Boots Clothing
Routes of Entry
Susceptible Animals Mouth Vagina Nose Prepuce Eyes Transplacental Skin Venereal Teats Blood
Incubation Period
Long/short
Exposure to symptoms
Exposure to positive tests
During incubation period No symptoms
Negative tests
Latent Infections(Recrudescent Infections) Extended incubation period
No symptoms Negative tests
After recrudescence Symptoms Positive tests
Vaccinate Susceptible Animals
Not 100% protection No response Improper procedures Mishandled vaccine Expired vaccine Stored opened vaccines Poor quality vaccine Primary dose only