ANIMAL HEALTH

1. ANIMAL HEALTH

2. The health of livestock is of great concern to farmers. Unhealthy livestock produce less, cost money and time, look horrible and cause a lot of stress.

3. What is an Animal Disease? • An animal disease is any kind of upset in the normal body functioning that has an adverse effect on the animal. • This upset or deviation from normal leads to signs and symptoms of disease. • In animals symptoms can take the form of an increase in body temperature, an increase in the number of white blood cells, loss of appetite, mucus discharge, skin rashes, or loss of body weight and production

4. Diseases are caused by:- • Micro-organisms • Animal parasites • Plant poisons • Nutrient deficiencies. • Diseases can be infectious or non-infectious.

5. The Effects of Disease on Animals Disease in animals may have the following effects: • Death of a small number or large number of the affected animals (caused by tetanus, blackleg or pulpy kidney). • Weakening and weight loss

6. Lower production (e.g. cows with mastitis produce less milk) • Infertility and lower calving or lambing percentages (caused by abortion bacteria, retained afterbirths etc) • Stunted growth (caused by internal parasites or nutrient deficiencies)

7. All diseases are expensive to the farmer and result in lower production from the animal and increased costs in production due to the cost of animal treatments. When an animal dies, the farmer loses the capital cost of that animal (around $1200 for a dairy cow, $625 for a breeding ram etc) and he has to replace it. He also loses that animals’ future production.

8. Types of Diseases Diseases are classified according to their cause as: • Traumatic diseases caused by physical trauma e.g fractures, wounds and abrasions. • Toxic diseases are caused by poisons such as lead, arsenic, yew leaves, macrocarpa and ragwort. • Hereditary diseases are passed on to the offspring by one of the genes. A featherless condition in chickens is passed on in this way as is dwarfism in cattle.

9. Deficiency and/or Nutritional diseases occur from the lack of some essential mineral e.g. cobalt and copper or lack of essential vitamins e.g. Vitamin B12 • Metabolic diseases occur when one section of the body is not working normally. Milk fever in cattle occurs when the calcium in the blood drops to a low level, usually after calving. This disease can be treated with an injection of calcium borogluconate.

10. Functional and /or Reproductive diseases occur when an organ fails to function due to some abnormality, as in sterility due to the blocking of the oviduct so that the ovum can not pass through. Heart failure in cows can lead to excess water retention. • Microbial diseases occur when a pathogen enters the animals. A pathogen can be a virus, bacterium, fungus or protozoan. • Some examples of microbial diseases are:- • Viral disease – BVD or Bovine Viral Diarrhoea. • Bacterial disease – tuberculosis, mastitis, pulpy kidney. • Fungal disease – ringworm. • Protozoal disease – coccidiosis in chickens.

11. Metazoal diseases are caused by metazoans, which can be seen with the naked eye. These organisms include:- • Flatworms - liverflukes and tapewormsRoundworms – threadworms, barber’s pole worm • Insects – sheep blowflies • Ticks and other arthropods – sheep keds, cattle ticks and lice.

12. Physical trauma on the leg of a calf. Ostertagia

13. Primary and Secondary Causes of Disease The primary cause of disease is the actual cause of the disease, whereas the secondary cause of disease assists the disease to occur. The most common secondary causes are:- Poor Nutrition – this can result from underfeeding, either during a drought or through over stocking. • When animals are competing for food, those at the bottom of the pecking order receive less food. • Poor nutrition also comes from feeding poor quality feed low in essential minerals etc to animals.

14. Poor Hygiene – this can occur when animals are intensively housed and waste management is inefficient e.g. housed pigs and chickens. Poor hygiene can also occur at vaccination, tailing, dehorning, drenching and in the milking shed. • Overcrowding – this is most common in housed animals. Weaker animals are unable to compete for food and water and may become stunted.

15. A primary cause will cause the disease, but may need some help: whereas a secondary cause is sometimes necessary for the disease to occur, but cannot cause the disease itself. E.g. the primary cause of mastitis in dairy cows is an infection by bacteria. • The secondary causes would include poor dairy hygiene and poorly adjusted milking machines. • Lack of feed, cold weather and rough handling would lower the cow’s resistance to disease. E.g. Tetanus in animals is caused by a toxin produced by a bacterium (primary cause). • For the toxin to affect animals, it needs to enter the body. • Therefore the secondary cause is a cut or wound to the animal. • Tetanus is easily controlled by the use of clostridial vaccines e.g. 5 in 1. Primary causes of disease can be viral, fungal, parasitic, toxic or metabolic.

16. Infection and Disease Micro-organisms cause disease by entering a host, multiplying and leaving the host. For a particular host, infection by an organism depends on:- • The existence of a source of the pathogen • The transferral of the pathogen • The invasion of the host by the pathogen overcoming the host’s barriers to infection • The establishment of the pathogen within the host long enough for it to cause the disease. • Once inside the animal host, the extent of damage is determined by the growth of the organism, or by the production of toxins or enzymes that are able to decompose host tissue. • The severity of the disease is also affected by the environment. If the environment is unfavourable, then the disease will struggle to gain a hold over the animal.

17. Infective agents may enter the body in a number of ways. 1.The most common method of entry is through the mouth. • Pathogens are swallowed with food or with drinking water. • All internal parasites e.g. roundworms and tapeworms, enter the body through the mouth when the animal eats the eggs or larvae on food or pasture plants (see later for more information). 2. Some pathogens enter through a break in the skin or a wound. Wounds can be caused by incorrect fencing knots, needles, injuries or bites. 3. Other pathogens may enter the body through the respiratory tract e.g. respiratory pneumonia.

18. TYPES OF MICROORGANISMS THAT CAUSE DISEASE • Micro-organisms can only be seen with the help of a microscope. They include viruses, bacteria, fungi, algae and protozoa

19. VIRUSES • Viruses are obligate parasites which can only reproduce inside the cells of another organism. • Viruses consist of nucleic acid (RNA or DNA) surrounded by a protein coat. • They infect a cell by incorporating their nucleic acid into the chromosomes of the host, initiating the production of more virus cells.

21. Viruses are responsible for many of the following animal diseases, most of which are spread by insect vectors, contact or inhalation. • Influenza • Rabies • Small pox • Scabby mouth of sheep • Distemper of dogs • Foot and Mouth disease.

22. BACTERIA • Bacteria are 0.5 – 2.0 um in diameter and are normally spherical, rod-like or helical in shape. • They have cell walls that may be rigid or flexible, occur singly or in colonies, reproduce by binary fission and are saprophytes or parasites. • Spherical cells are called cocci (singular coccus). • Often cells do not separate during reproduction but remain attached to each other and thus form pairs of cells (as in a diplococcus), or in a linear chain (as in a streptococcus). • When a grape like cluster of cells form, they are known as a staphylococcus. • Rod shaped bacteria are termed bacilli (singular bacillus) and can be long or short. • There are several groups of spiral or curved shaped bacteria.

24. Some bacteria are able to move. They do this by either swimming through liquids by means of flagella or by gliding in contact with a solid surface. • Flagella (singular flagellum) are long thin whip-like extensions from the cell wall.

25. In animals bacteria cause:- • Brucellosis • Anthrax • Salmonellosis • Pulpy kidney • Mastitis • Tetanus

26. FUNGI Fungi are simple eukaryotic plants consisting of fine branching threads or filaments called hyphae. They range in size from single-celled yeasts to multicellular mushrooms and reproduce asexually by spores or sexually by zygotes. In animals, fungi cause:- • Ringworm • Lumpy jaw.

27. PROTOZOA Protozoa are single celled heterotrophs (i.e. they can not produce their own food). They range in size from 5 to 250 micrometers long. They can be either free living or parasitic. • The cell wall is not always present, and if present it does not contain cellulose. • Some groups of protozoa reproduce by binary fission (dividing in two) others by multiple fission (dividing into many parts). Protozoa cause the following diseases in animals:- • Coccidiosis • Tick fever in cattle • Toxoplasmosis.

28. OTHER ORGANISMS THAT CAUSE HEALTH PROBLEMS IN ANIMALS A number of other organisms cause health problems in animals. These are found in the following invertebrate classes:- • Insects • Arachnids • Flatworms • Nematodes • Molluscs.

29. INSECTS Insects are one of the most prolific and successful life forms on earth. Insects belong to the Phylum Arthopoda or ‘jointed-feet’ organisms. To be classified as an insect, an organism must have the following characteristics:- • A body divided into 3 distinct sections, head, thorax and abdomen. • Three pairs of legs attached to the thorax. Wings may also be attached to the thorax. • No legs attached to the abdomen in the adult stage. • Air sacs called trachea (through which the organism breathes). • An exoskeleton (i.e. protective or supportive structure covering the outside of the body). The main insect pests of animals are:- • Sheep blowfly • Sheep ked.

30. THE LIFECYCLE OF SHEEP BLOWFLY

31. ARACHNIDS Arachnids are closely related to insects. They also are part of the Phylum Arthopoda. They include ticks, mites and spiders. To be classified as an arachnid, an organism must have the following features:- • A body divided into two parts. • Four pairs of legs. • No antennae. The most important arachnids affecting agriculture are ticks and mites. • Ticks have specialised structures that enable them to anchor themselves to a host. • They also have specialised mouthparts for piercing and sucking. • Mites have limbs that been modified for attachment or burrowing. Some also specialised mouthparts for feeding.

33. Ticks and mites are ectoparasites (i.e. external parasites) of farm animals. They suck the blood from the host and reduce their condition. Lice can cause serious losses in production if left untreated.

34. PLATYHELMINTHS OR FLATWORMS Platyhelminths are flatworms and belong to the Phylum Platyhelminthes. They can be free living or parasitic. To be classified as a flatworm, an organism must have the following characteristics: • Body usually flattened. • Definite reproductive and excretory organs. • A mouth leading to a simple gut. • Attachment organs such as suckers and hooks. • No circulatory or respiratory system. There are two classes of Platyhelminths that are important internal parasites of farm animals, Class Tremtoda (flukes) and Class Cestoda (tapeworms). • Tapeworms and Liver Fluke are important endoparasites of farm animals. They cause poor condition

35. The Life Cycle of Liver Fluke

36. NEMATODES Nematodes are also called roundworms, threadworms or eelworms. They have the following characteristics:- • A long, round body. • A non-segmented body. • A digestive tube with a mouth and anus. In farm animals, thousands of eggs are laid by the female in the digestive tract of the host animal. The eggs then pass out with the faeces. In warm and moist conditions, the eggs hatch and develop into infective larvae. The larvae crawl up blades of grass, are swallowed, and reinfection occurs. The nematodes that cause problems in farm animals include barber’s pole worm and Nematodirus.

38. THE DIFFERENCES BETWEEN CESTODES, TREMATODES AND NEMATODES.

39. MOLLUSCS Molluscs are soft-bodied invertebrates with shells. With regard to animal health, a snail is part of the liver fluke life cycle (see earlier).