Classification of Livestock Diseases and Methods of Transmission
A disease including livestock diseases can be described as a condition resulting in a deviation from the normal functional or behavioural status of an animal. Disease can be infectious or noninfectious.
Infectious diseases are those diseases that are caused by pathogenic microorganisms such as bacteria, viruses, protozoa and fungi that invade an animal’s body and can spread from one animal to another directly or indirectly (contagious).
Noninfectious diseases on the other hand are not caused by pathogens rather they can result from nutritional deficiencies, the environment or are inherited (genetics). A pathogen is a disease causing microbial agent.
This article will present the different ways diseases are classified and the methods of disease transmission in animals
Causes of Diseases
Diseases are caused by mostly pathogenic microorganisms or parasites which invade, colonize and multiply within the host cells (animal cells) causing a significant change in the body. These pathogens can be bacteria, virus, fungi, protozoa or even a parasite.
The first man to associate a particular microbe with a particular disease was Robert Koch in 1877. He attributed the disease anthrax to the organism called Bacillus anthracis.
The manner in which a disease develops (pathogenesis) differs with different diseases. There are other causes of diseases which include injuries, poisons/chemicals, poor nutrition or genetics.
Methods of Disease Transmission
Diseases are transmitted from one animal to another through the following ways:
Contact Transmission: This can be by direct contact between animals that are staying together in the herd or flock or when they meet in open field during grazing or even at animal markets.
It can also be indirect contact when animals come in contact with other objects that a sick animal has had contact with. These objects can non-living (fomite) such as syringes, boots worn by attendants, feeding troughs, pasture etc.
Vehicular Transmission: This type of transmission occurs via a medium which can through feed (food poisoning), water, air (spores), fluids (saliva) etc.
Vectors: This type of transmission refers to other animals that carry disease causing agent from one host to another and majority of these are insect or arthropods. They transmit these pathogenic microorganisms and/or parasites either mechanically or biologically.
In mechanical transmission, they passively carry the pathogen on their body parts while in biological transmission which usually involves biting actiona, part of the life cycle of the pathogen occurs within the body of the vector.
An example of this when the transmission of Malaria by mosquitoes or Trypanosomosis by Tsetse fly (Glossina species).
Read Also: Guide to Proper Prevention and Control of Livestock Diseases
Classification of Livestock Diseases
Livestock diseases can be classified using different criteria depending on what best satisfies the situation under consideration.
Consequently diseases can be classifies based on species of animals (Avian Diseases, bovine diseases, equine diseases, caprine diseasesetc); system of the body affected (Cardiovascular diseases, respiratory diseases, reproductive diseases etc) and the causative organism.
However, the etiology or causative organism is the most widely used method of classification. Here they are classified as:
Bacterial diseases – example, Anthrax, Mastitis, Salmonellosis, Fowl typhoid, etc.
Viral diseases – example, Foot and Mouth Disease, Rinderpest, African swine fever etc.
Protozoan diseases – example, Coccidiosis, Trypanosomoses, Babesiosis, etc.
Rickettsial diseases – example, Anaplasmosis, Cowdriosis, Infectious keratoconjuctivitis
Fungal diseases – example, Aspergillosis, Ringworm, Epizootic lymphangitis
Endoparasitic diseases (caused by worms) – example, Fascioliosis, Haemonchosis etc
Ectoparasitic diseases (caused by ticks, lice, fleas) – example, Mange, fleabite dermatitis, etc.
Deficiency diseases – Vitamin deficiencies, pregnancy toxaemia, etc.
Toxicoses – examples – Nitrate poisoning.
Livestock diseases can also be classified on the basis of disease prevention into six categories which are:
Neonatal diseases – diseases that affect very young animals, mainly diarrheal in nature
Vector-borne diseases – diseases transmitted by a living vector such trypanosomosis
Soil-borne diseases – disease mostly caused by aerobic and anaerobic spore-forming bacteria (e.g. botulism)
Contact diseases – usually responsible for serious epidemic diseases in livestock in the tropics such as Rinderpest, Foot and Mouth disease etc.
Parasitic diseases – similar to contact diseases examples include haemonchosis, fascioliosis etc.
Others include: Nutritional and Metabolic diseases
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