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close this bookAnimal Disease Control and Treatment (IIRR, 1996, 60 p.)
View the documentForeword
View the documentDisease causes and symptoms
View the documentDiseases of ruminants
View the documentDiseases of pigs
View the documentDiseases of chickens
View the documentDiseases transmissible to people

Disease causes and symptoms

Diseases are abnormal conditions of the body. You can tell an animal has a disease by looking for symptoms, or observable signs.

A disease may be acute or chronic.

Acute diseases appear suddenly, last only a short time, but are severe.
Chronic diseases last a long time, but are not usually severe.

Animals can get sick if:

· they come in close contact with sick animals;
· they graze in an area where sick animals have grazed or died, or
· they do not receive proper care and food.


A sick animal shows one or more of the following signs:

· Staying away from other animals.
· Loss or lack of appetite.
· Fever.
· Frequent thirst and shivers.
· Inactivity.
· Constipation or diarrhea.
· Drooping ears, tail or wings.
· Change in color.
· Abnormal discharges like pus, mucus.

FIG. 1. Disease causes and symptoms

Classification of diseases

Diseases may affect different parts of the animal's body.

Digestive-affects stomach and intestines
Respiratory—affects breathing and lungs.
Urinary—affects kidneys and bladder.
Reproductive—affects uterus, vagina, ovaries (in females) or penis, testes (males).

Disease causes

Contagious. These are diseases transmitted directly from one animal to another. Examples: Foot-and-mouth disease (FMD), Hog Cholera.

Infectious. Diseases caused by microscopic organisms such as bacteria, viruses, fungi and one-celled parasites (protozoa). Many infectious diseases are contagious (see below). Others such as tetanus, are not contagious.

Parasitic. Diseases due to different kinds of parasites. Examples: Mange, lice infestation, worms.

Deficiency. Diseases due to different kinds of nutritional deficiency. Example: Iron deficiency.

Metabolism. Diseases due to some kind of an upset which affects important body processes. Example: Milk fever.

Poisoning. Disorder due to eating something that destroys tissues or interferes with normal body functions. Example: Lead poisoning.

Injuries. Damage done by cuts or accidents. Example: Fractures.

Miscellaneous. Includes disorders diet do not properly belong under any of the other headings Example: Prolapse of uterus.

Prevention and control of any disease can be assisted in a number of ways:

· Education of farmers.
· Good management and feeding.
· Sanitation (keeping animals and housing clean).
· Vaccination.
· Early treatment.
· Isolation of sick animals.