Animal Health

Parasites

Their Life Cycles and Classification

Infectious Agents Causing Disease can be divided into

Three General Groups:

Bacteria

Viruses

Parasites

Bacteria

• Simple plant life• Microscopic• Can be Pathogenic and

beneficial• Live outside of host• Sensitive to antibiotics

Viruses

• Are Ultra-microscopic• Live in tissue of host

cells• Are resistant to

antibiotics• highly contagious

Parasites

• Live in, on, or at the expense of the host.

• Infections develop slowly

• Difficult to eradicate completely

• Animals do not develop resistance

• Animals may not show symptoms

• Host-specific

• Include fungi, protozoa, arthropods, and helminths

Bot fly common horse parasite

The Parasites in this Group

• Cause tissue damage

• Absorb nutrients

• Suck blood and lymph

• Obstruct passages

• Causes growths

• General irritation

• Secondary infections

• Cause serious economic damage

Non-infectious AgentsThat Cause Disease

• Chemical and poisons

• Poor Nutrition

• Injuries

• Physical stress from breeding, conception, lactation, and birth

• Any other stress or trauma that weakens the animal or its immune system to secondary infections

Causes Of Disease

• Nutritional Defects– Result from unbalanced

diets

• Physiological Defects– Improper functioning of

body parts

• Morphological Defects– Physical disabilities

• Pathogenic Organisms– Tiny living things

capable of causing disease

Life Cycle of Tapeworm in a Sheep

Ascarids

Strongyles

Beef and Pork Tapeworms

The Life Cycle of FliesOccurs in Four Stages

Lice

Ticks

Tick infested horse