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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
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How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Dec 22, 2015

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Page 1: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

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

Page 2: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

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

Page 3: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.
Page 4: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Idea Pathogen has left infected host and looking for

susceptible host

Page 5: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Direct vs. Indirect Transmission

Direct transmission Direct or close contact

Indirect transmission Vectors Vehicles Fomites

Page 6: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Routes of Transmission

Aerosol Oral Vehicle Vector

Mechanical Biological

Page 7: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

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

Page 8: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Vectors (live)

Ticks Flies Mosquitoes Scavengers People

Page 9: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Vehicles (not alive)

Instruments Needles Ear tagger Tattooer Dehorner Nose tong Knife

Utensils Buckets Troughs Boots Clothing

Page 10: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Environment

Soil Water Food Air

Page 11: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Routes of Entry

Susceptible Animals Mouth Vagina Nose Prepuce Eyes Transplacental Skin Venereal Teats Blood

Page 12: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Incubation Period

Long/short

Exposure to symptoms

Exposure to positive tests

During incubation period No symptoms

Negative tests

Page 13: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

After incubation period

Symptoms Positive tests

Page 14: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Latent Infections(Recrudescent Infections) Extended incubation period

No symptoms Negative tests

After recrudescence Symptoms Positive tests

Page 15: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Injury Blackleg Malignant edema Black disease Black-neck disease

Diet change/overload Enterotoxemia

Page 16: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Flukes Redwater

Stress IBR/PI3/BVD/BRSV Pasteurella/haemophilus

Pregnancy in heifers Brucellosis

Page 17: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Non-Latent Infections

Normal incubation period

Page 18: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Stress Factors

Nutrition Weather Pregnancy Calving Working Weaning Shipping Breeding Walking

Page 19: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

High Risk Herds

Identify sources Separate carrier/reservoir animals

(shedders) Reduce commingling

Page 20: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

Vaccinate Susceptible Animals

Not 100% protection No response Improper procedures Mishandled vaccine Expired vaccine Stored opened vaccines Poor quality vaccine Primary dose only

Page 21: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

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

Page 22: How Diseases and Parasites are Spread 4-H Veterinary Science Extension Veterinary Medicine Texas AgriLife Extension Service College of Veterinary Medicine.

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