Livestock Parasitology Animal Science

TERMINOLOGY Parasitology – branch of biological science that deals with the study of parasites. Epidemiology – science dealing with the relationships of the various factors which determine the frequencies and distribution of disease. – Three parts – disease causing agent, susceptible animal, correct environment. Remove one of these, and disease will not occur.

Terminology continued Parasite – plant or animal which lives upon or within another living organism. Host – organism which harbors and/or nourishes a parasite. Intermediate host – organism that harbors the larval or asexual stages of the parasite’s life cycle. Definitive host – an organism that harbors the adult or sexual stages of the parasite’s life cycle.

More terminology Vector – insect or arthropod which carries micro-organisms from one host to another. Infestation – invasion of arthropod macro- organism such as mites, ticks, and insects. Invasiveness – the ability to invade in living tissue. Communicability – rate of transmission of pathogen from a host to another

Requirements for a Parasite Gain entrance to host – nose & throat most common. Multiply and adapt to environment. Exit from host – feces for internal parasites, insects, conjunctive, saliva. Mechanism to transfer to a new host – insects, eggs, larvae, intermediate host.

Mechanism of Host Resistance Physiological barriers to parasites – Skin – flora in rumen and intestinal tract – nose & trachea – conjunctiva of eyes – genital tract – phagocytosis

Influence of Age, Nutrition & Environment Age – younger animal have less resistance Stress – climate, shipping, fatigue Nutrition – Vitamin's A & C increase host resistance, protein deficiency lowers antibodies. Environment – unsanitary housing, dirty water source, overcrowding.

Typical life cycle of internal parasite

Liver flukes have an intermediate host.

Heart worm cycle in dogs Note the intermediate host of the mosquito!

A Few External Parasites Fleas, one of the most common external parasite. Mites burrow into the skin and cause itching.

Blood Sucking Flies! Horn flies bite the animal and suck blood. Horse flies suck blood and are vicious feeders.

DEER TICKS CARRY LYME DISEASE The changing face as the deer tick engorges itself with blood.

The Cost of Parasites to the Animals Internal parasites such as stomach worms, intestinal, roundworms and tapeworms are all examples of internal parasites that can drain the nutrients that an animal should be able to absorb and metabolize effectively. Parasites such as these that exist in the digestive tract have serious effects on the digestive system itself as well as on the availability of the nutrients consumed which are critical to animal health and performance.

Over All Health Problems Any situation where the immune system is compromised creates a problem. With internal parasite s there a problem with depressed nutritional status. There is damage to the gastrointestinal tract and other tissues (liver tissue with liver flukes, lung tissue with a lungworms). Parasites compromise blood volume which creates a problem for normal metabolism in the animal. These circumstances can decrease the animal's performance and will ultimately cause death if left untreated.

How do we control Parasites? Sanitation of housing, pastures, pens. Avoid overcrowding of animals. Deworming on regular schedule – Using anthelminthic - drench, injectable, pour-on Fecal testing – accomplished with fecal sample, microscope. Can be completed by a veterinarian or you can do it.