INTRODUCTION OF LIVESTOCK AND POULTRY DISEASES
CONCEPT OF HEALTH AND DISEASE
general, the normal structural (anatomical) and functional (physiological) well-being of an animal are called health. According to the World Health Organization (WHO), health is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity. Here, health indicates the general condition of a person in all aspects. It is also a level of functional and/or metabolic efficiency of an organism. Animal health is the subject matter of veterinary science. Normal urination and defecation, normal growth, production and reproduction, normal physiological attributes like body temperature, respiration and pulse rates, normal behavior, and workability are the indications of good health of animals. Any deviation from the normal state of health is called disease. Like human beings, domestic animals may also suffer from various types of diseases, which may lead to havoc loss in animal business through the death of animals or reduced production. Animals cannot express their complaints. So, diagnosis of animal disease is a very difficult task. History taking (based on asking suitable questions to the animal keepers) is the key for an accurate diagnosis of animal disease, besides various clinical and laboratory investigations. On the other hand, the cost of animal treatment is increasing day by day. So, it is truly said that prevention is better than cure.
SIGNS OF ILL HEALTH OF ANIMALS
Observation of various signs of ill health helps in the early diagnosis of the disease. The most common signs of ill health of livestock are indicated below:
1. Change in normal posture and behavior: Change in normal posture and movement indicates an early disease condition. Animals standing alone at the corner of the shed separating from others or animals standing with head down, pushing the head against a wall, charging at various objects, and acting aggressively are warning signs. Some specific postural changes of animals are observed in some specific diseases like keeping the head on flank region in milk fever of dairy cows, stiff gait and locked jaw in tetanus, walking in a circle in gid of goats, etc. Different abnormal postures in animals are observed in paralysis, fracture, dislocation of the hip, sprain, injury, inflammation, etc. Some specific behavioral changes may be observed in some specific disease conditions like excitement in nephritis, difficulty in defecation in impaction, or constipation, etc.
2. Loss of appetite: There may be partial loss of appetite (inappetence) or complete loss of appetite (anorexia). Conditions like Suspended rumination or no rumination may be seen in ruminant animals.
3. Dry skin, falling of hair, and change of color of skin: Dry skin and falling of hair may indicate disease. It may be caused due to deficiency of nutrients (like zinc deficiency) ectoparasitic infestation (like lice or mange infestation, etc.). In Swine disease, red-violet colored patches are seen on the skin. Erysipelas
4. Dry muzzle: Dry muzzles indicate dehydration and hyperthermia or fever.
5. Abnormal secretion: Abnormal secretions like Mucoid or mucopurulent discharge and blood-stained discharge from the nose (in respiratory infection), fresh blood from the nose (epistaxis), excessive saliva from the mouth (in FMD, PPR), discharge from the eye (1lachrymation), and the presence of glue in the eyes, abnormal discharge from genitalia like pus, blood, foul-smelling discharge in pyometra, metritis).
6. Change of color of urine: Normal urine color is straw-washed water. Sometimes, red urine (haematuria/hemoglobinuria) is seen.
7. Change of consistency of feces: Loose stool/diarrhea and constipation are very common. It commonly indicates digestive problems. The normal consistency of feces of different livestock species is cattle and buffalo: semi-solid, sheep and goat: the aggregate of small globules, chicken: droppings.
8. Sudden reduction of milk yield and mastitis:Milk yield may be reduced suddenly in some diseases (like FMD). Watery milk, blood in the milk, curd, and flakes in milk, hot painful udder, swollen udder and teats are the indications for mastitis (inflammation of the udder).
9. Abnormality in body structures: Enlarged joints with joint pain (arthritis), swelling (abscess, cyst, neoplasm, haematoma), abnormal abdominal distension (bloat/tympanitis), etc. indicate ill health.
10. Change of physiological norms: Variation in common physiological norms like body temperature (rectal temperature), respiration rate and pulse rate indicate ill health of animals. However, female animals in advanced pregnancy, young animals, and animals after exercise or grazing on the field usually show higher body temperature, respiration and pulse rates than normal. On chilly days, weak and debilitated animals usually show sub-normal body temperature.
CLASSIFICATION OF ANIMAL DISEASES
Animal diseases can be classified according to etiology or cause of the disease as follows:
1. Infectious and contagious diseases
The diseases caused by specific organisms and spread rapidly from one animal to another are called infectious diseases. These diseases lead to havoc loss in animal farms by causing the death of the animals/If these diseases are spread from one animal to another through direct contact, they are known as contagious diseases. So, all infectious diseases are not contagious like Tetanus, Wooden tongue, Lumpy jaw, etc.
The most important infectious diseases of livestock are as follows:
(a) Viral diseases: Foot and mouth disease (FMD), Rinderpest (already eradicated from India), Swine fever or Hog cholera, Peste des petits ruminants (PPR), Goat pox, Sheep pox, Rabies, Ranikhet disease (RD), Marek’s disease, Gumboro disease (Infectious bursal disease), Fowlpox, Infectious bronchitis, etc.
(b) Bacterial diseases: Haemorrhagic septicaemia (HS), Black quarter (BQ), Anthrax, Brucellosis, Tuberculosis, Johne’s disease, enterotoxaemia, Tetanus, etc.
(c) Protozoan diseases: Coccidiosis, Babesiosis, Theileriasis, Trypanosomiasis, ete.
(d) Fungal diseases: Ringworm, Aspergillosis (caused by Aspergillus fumigatu Acpergillus flavus), Aflatoxicosis (caused by the toxin/aflatoxin liberated by Aspergillus flavus), etc.
2. Parasitic infestation
Parasites are mainly of two types–internal and external parasites. Internal parasites called worms affecting livestock may be of three types. viz., roundworms or nematodes, tapeworms or cestodes, and flukes or trematodes. Maximum worms harbor in the stomach and intestines. However, some worms may be found in the liver, lungs, eyes, etc.
The most important roundworms affecting animals are Ascaris, Trichuris (Whipworm), Strongyloides (Threadworm), Hookworm, Oesophagostomum (Nodular worm), Stomach worm (Wireworm), Lungs worm, and Stephanofilaria (causing hump sore).
The most important tapeworms of animals are Moniezia sp. (affects ruminants), Taenia solium (pork tapeworm), Taenia saginata (beef tapeworm), and Echinococcus granulosus (dog tapeworm).
The most important flukes affecting animals are Fasciola (liver fluke causing Fascioliasis), Amphistomes (harbor in rumen and reticulum), and Schistosoma (blood fluke causing nasal granuloma or Schistosomiasis).
External parasites are lice, ticks, mites, flies and mosquitoes, etc. They cause nuisances in animals, as well as they, may act as vectors to spread some diseases.
3. Deficiency diseases
The deficiency of vitamins, minerals, and other nutrients may cause deficiency disease in livestock. These diseases are also called nutritional diseases. For example, deficiency of iron causes anemia, deficiency of iodine causes goiter, VitaminD deficiency causes rickets, deficiency of Vitamin B or thiamine causes polyneuritis or Stargazing appearance in poultry, deficiency of Vitamin B2 or riboflavin causes the curled toe paralysis in poultry, etc.
4. Metabolic diseases
These diseases are caused due to problems in the metabolism of a particular nutrient. For example, milk fever or hypocalcemia (due to the problem of Ca metabolism leading to deficiency of Ca in the blood), ketosis or hypoglycemia or acetonaemia (a problem in carbohydrate metabolism leading to deficiency of glucose in the blood), etc.
Poisoning may occur due to accidental ingestion of poison or toxic substances. Hydrocyanic acid (HCN) poisoning may occur due to feeding of gamma grass in the pre-flowering stage, bamboo shoots, etc., hydrocarbon poison may occur due to ingestion of insecticides like Aldrin, Chlordane, DDT, etc., organophosphorus poisoning may occur due to accidental ingestion of Malathion, Sumithion, Neguvon, etc., which are widely used in agricultural fields for protection of crops from various insects.
Like human beings, animals may suffer from allergies, e.g. photosensitization (allergy due to sun rays), serum shock, etc. Animals should be kept away from the specific allergen.
7. Congenital defects
Congenital defects may be seen in newborn animals due to genetic causes or abnormal growth of embryos, e.g. Atrecia ani (closed anus), closed vulva, extra teat in female calf, etc. Minor surgical intervention is needed to correct these congenital defects.
8. Miscellaneous diseases
The diseases which cannot be classified in the above groups are included in this list, e.g., tumor, bloat, retention of placenta, etc.