1. How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine and Biomedical Science Texas A&M System http://aevm.tamu.edu

2. Objectives 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

4. Idea Pathogen has left infected host and looking for susceptible host

5. Direct vs. Indirect Transmission Direct transmission Direct or close contact Indirect transmission Vectors Vehicles Fomites

6. Routes of Transmission Aerosol Oral Vehicle Vector Mechanical Biological

7. Sources A. Carrier/reservoir animals 1. Aerosol droplets 8. Milk 2. Nasal fluid 9. Fetal fluid 3. Ocular fluid10. In utero 4. Saliva 11. Genital fluid 5. Skin12. Blood 6. Manure13. Carcass 7. Urine

8. Vectors (live)  Ticks  Flies  Mosquitoes  Scavengers  People

9. Vehicles (not alive) Instruments Needles Ear tagger Tattooer Dehorner Nose tong Knife Utensils Buckets Troughs Boots Clothing

10. Environment Soil Water Food Air

11. Routes of Entry Susceptible Animals Mouth Vagina Nose Prepuce Eyes Transplacental Skin Venereal Teats Blood

12. Incubation Period Long/short Exposure to symptoms Exposure to positive tests During incubation period No symptoms Negative tests

13. After incubation period Symptoms Positive tests

14. Latent Infections (Recrudescent Infections) Extended incubation period No symptoms Negative tests After recrudescence Symptoms Positive tests

15. Injury Blackleg Malignant edema Black disease Black-neck disease Diet change/overload Enterotoxemia

16. Flukes Redwater Stress IBR/PI 3 /BVD/BRSV Pasteurella/haemophilus Pregnancy in heifers Brucellosis

17. Non-Latent Infections Normal incubation period

18. Stress Factors Nutrition Weather Pregnancy Calving Working Weaning Shipping Breeding Walking

19. High Risk Herds Identify sources Separate carrier/reservoir animals (shedders) Reduce commingling

20. Vaccinate Susceptible Animals Not 100% protection No response Improper procedures Mishandled vaccine Expired vaccine Stored opened vaccines Poor quality vaccine Primary dose only

21. Long/short protection Vaccinate before exposure Does not prevent recrudescence in latent infections

22. Biosecurity Measures Raise replacements Purchase animals from clean herds Test purchased animals Vaccinate purchased animals Isolate purchased animals Restrict visitors and vehicle entries Construct buffer zone fencing