Principles of Animal Disease -Unit 1

Health

• Normal

• Fully functional

• homeostasis

• nothing impeding regular processes

Disease

• illness

• injury

• impacts normal function/homeostasis

• overwhelmed system

Subclinical

occurring with no outward signs, no changes in behavior but impeding animal

Clinical

showing signs, groggy, fever, depressed, diarrhea, hacking, active

Terminal

death

Endemic

normal amount that circulates through a population, no outbreak, may vaccinate

Epidemic

new introduction of disease to a population spreads rapidly, lots at risk

Pandemic

new introduction that crosses natural defense borders (mountains, continents, etc.)

epidemic

Causes of disease

• genetic

• infectious

• toxic

• parasitic

• hormonal

• injury

• mismanagement

Prophylaxis

preventative treatment

Metaphylactic

sick animal treated with antibiotic after diagnosis

Therapeutic

mass treatment to decrease impact on group (parasite treatment)

Why is it important to understand disease transmission?

important for implementing proper prevention and control mechanisms

Examples of Mechanisms of transmission?

• other animals

• environment

• equipment

• insects

• contaminated feed or water

Anthrax

example of how pathogens can cause different diseases based on how it is transmitted

Direct transmission

• Requires physical contact between an infected animal and a susceptible animal, and the physical transfer of microorganisms

• direct touch, sexual contact, bite, contact with oral secretions, contact with body lesions

Indirect Contact Transmission

• situations where a susceptible animal is infected from contact with a contaminated surface

• some organisms are capable of surviving on surfaces for an extended period of time

  • microorganism must be able to survive in environment for transmission

Droplet contact transmission

• situations where infected droplets contact the surfaces of the eye, nose, or mouth of susceptible animals

• too large to be airborne for long

• only travel a few feet

Airborne Transmission

• situations where droplet nuclei or dust particles containing microorganisms can remain suspended in air for long periods of time, and can be inhaled into the respiratory tract

• organisms must be capable of surviving for long period of time outside the body and must be resistant to drying

Fecal-oral transmission

• usually associated with organisms that infect the digestive system.

• microorganisms enter the body through ingestion of contaminated food and water

Urinary transmission

• usually associated with organisms that infect the urinary system

• microorganisms enter the body through ingestion of contaminated food and water

• (lepto matures in kidneys and is shed through urine)

Vector-borne transmission

• vectors are animals that are capable of transmitting disease

• intermediate

• blood-borne pathogens

• vectors must be controlled to control pathogen/disease

• increased range

• changes in vector behavior will affect the transmission pattern of the disease

Fomite-borne transmission

• fomites are inanimate objects capable of carrying microorganisms

Biosecurity

steps taken in reducing the risk of introducing disease from outside sources

Biocontainment

steps taken in mitigating and reducing the spread of disease already present on an operation

Steps of biosecurity

1. Prevent entry of disease into herd

2. Prevent movement of disease within herd

3. Prevent export of disease from herd.

Prevent introduction and contain and prevent spread

Risk assessment

• What diseases exist nearby/ are common?

• How much risk are you willing to take?

• How much money are you willing to spend?

Transmission Risk

Factors that increase (or decrease) chance of introducing disease

Pre-Patent Period

• Period of time between pathogen exposure/infection and signs of disease

• AKA incubation period

• can be days, weeks, or years

• Microorganism is growing and replicating before it reaches the pathogenic level

Ways to control disease within a herd

• maintain a closed herd

• vaccinate the herd against common diseases

• minimize fenceline contact with neighboring animals (buffer zone)

• isolate sick animals

• quarantine animals after returning to farm

Quarantine/isolation

• physical separation of animals from the rest of the group

• length is usually based on disease PPP

• good time to run diagnostics on new animals (if part of the management plan)

Biosecurity and replacements

• Lowest risk: raise your own replacements

• Purchase from verified sources (tested-nontested-dealers-auctions)

• Clean trailers used to carry animals

• quarantine all new animals for 45 days

• disease diagnostics on new animals for targeted diseases

Biosecurity and visitors

• Sign ins

• minimize visitors

• clean hands, clothing, shoes, etc.

• minimize contact with animals

• do not allow foreign visitors until they have been in the country for 5 days

Biosecurity and Vehicles

• develop vehicle flow pattern

• on-farm only vehicles

• special parking area

• clean trucks for cleaning

• separation of clean and dirty tasks

Handling Deadstock

• deadstock can be disposed of in several ways depending on local and environmental regulations

• if animals are picked up, ensure the rendering truck picks them up at the perimeter of the operation (#1 risk, travels to lots of farms)

Biosecurity and Employees

• written biosecurity plan

• develop work flow pattern

• education

• handle healthy animals first

• consider risk of personal pets

Justification for Biosecurity

• enhance/maintain profitability of the operation

• pre-harvest food safety programs required by packers/retailers

• continued consumer acceptance of product

• possible economic penalties in the future

• survival in case of bioterrorism