Transcript animal health

ANIMAL HEALTH
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.
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
Diseases are caused by:•
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Micro-organisms
Animal parasites
Plant poisons
Nutrient deficiencies.
Diseases can be infectious or noninfectious.
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
• 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)
• 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.
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.
• 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.
• 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.
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.
Physical trauma on the
leg of a calf.
Ostertagia
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.
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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.
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.
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.
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.
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
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.
• 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.
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.
• 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.
In animals bacteria cause:•
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Brucellosis
Anthrax
Salmonellosis
Pulpy kidney
Mastitis
Tetanus
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.
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.
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.
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.
THE LIFECYCLE OF SHEEP
BLOWFLY
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.
• 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.
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
The Life Cycle of Liver Fluke
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.
THE DIFFERENCES BETWEEN
CESTODES, TREMATODES AND
NEMATODES.
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).