Animal health

who definition of health

1948 - state of complete well being

• physical

• mental

• social

not merely the absence of disease

why is animal health important

profit losses

• mortality

• morbidity (illness)

• vet costs

• marketing

animal welfare

• suffering and stress

monitoring animal disease

diagnose early and treat illness

visual and electronic monitoring

proactive health management - illness prevention

physical health challenges

external factors, fighting, falling

microbial challenges to health

infection (bacteria and parasites)

infestation (parasites)

metabolic challenges to health

insufficient diet

poisons

allergies

psychological challenges to health

stress

fear

delight

anxiety

adaptations to reduce chance of injury

sensitive pain receptors - learnt hazard avoidance

stable social grouping (familiar vs strange)

infection avoidance

barriers to entry - skin, hair

maintain hygiene - excretory areas

fight infection and repair damage

immune system + gut

tissue and wound healing

factors affecting animal health (conditions they are kept in)

crowding and stress

selective breeding for desired traits

artificial feeding and housing

barren environments

infection prevention at a group level

biosecurity

hygiene and disinfection

vaccinations/treatment

infection prevention at an animal level

physical barriers

chemical barriers

immunological barriers

how do infections spread

contaminated air/food/water/soil

handling infected materials

contact with infected people

biosecurity definition

Practices aimed at preventing the introduction and spread of infectious diseases within animal populations - some diseases zoonotic - protects animals and humans

how to protect from contaminated air

selecting site based on

• distance from infected neighbours

• air filters

• windbreaks

• wind direction

functions of skin and scales

• physical barrier to external environment

• continuous with all natural openings of body

• protects from mechanical injury, radiation, desiccation, pathogen invasion or toxic substances

• vitamin d regulation

• sensations of hot, cold, pain and touch

challenges to skin integrity

physical

• cuts, scratches, grazes

• bruises

• ulcers

• puncture wounds

thermal

• burns or frostbite

skin responses to trauma

defensive

• inflammatory response - local reaction by immune system

reparitive

• renews integrity of skin - may lead to excess fibrous tissue = scar

inflammatory phase of skin

2-5 days long

haemostasis and inflammation

haemostasis

• vasoconstriction - epinephrine

• platelet aggregation - cytokines - attracted by collagen exposure

• coagulation - platelets bound by fibrin - fibrin formed by conversion of fibrinogen

• clot formation

haemophilia

lack of clotting factor VIII

thrombosis

clotting inside blood vessels

inflammation

vasodilation and phagocytosis

• platelets release factors attracting WBCs

• WBCs remove debris, release GF attracting fibroblasts from surrounding tissue

• WBC inject Hb from RBCs - convert to other compounds - gives colour of bruises

proliferative phase

2 days to 3 weeks

granulation

contraction

epithelialisation

granulation

• fibroblasts lay bed of collagen

• fills defect and produces new capillaries

• granulation tissue composed of leucocytes, fibroblasts and vascular endothelial cells

contraction

wound edges pull together

immune cells and exudate migrate outwards - forms pus in cavity

tissue grows up from bottom of wound

epithelialisation

epithelium grows out over granulation tissue to re-establish continuity of skin

collagen fibres initially fine but coarsen - strengthen and shorten over time - scar puckering

maturation/remodelling phase

new collagen forms to increase tensile strength

scar tissue only 80% as strong as original tissue

calcium in the body

99% contained in bones - remainder crucial for life

• nerve transmission, muscle contraction, blood clotting, cell division, enzymes

• maintains a constant blood level - dependent on supply and demand

• bone formation and resorption - osteoclast

what happens if blood calcium is low

• stimulation of parathyroid hormone

• activation of cholecalciferol in liver

• formation of hydroxycholecalciferol

• further activation to dihydroxycalicalciferol

• synthesis of ca binding protein - acts on gut, kidneys and bones to raise blood Ca

milk fever

low blood calcium - hypocalcaemia

• 5-8% incidence in dairy herds

• change in calcium requirement due to lactation

• calcium infusion or death

• prevented by calcium or vit d at calving, and a low calcium diet when dry

magnesium in the body

• 70% in bones

• needed for enzyme activity for carbohydrate and lipid metabolism

• nervous irritability and convulsions

• hypomagnesaemic tetany = death

• high in vegetable protein feeds, low in rapidly growing grass

hypomagnesaemic tetany

• rapid onset or sudden death

• highest risk in spring

• prevented by constant magensium supply

• cows - 20/30 Mg per day

• ewes - 2-3 Mg per day

hyperlipaemia

• fatty liver

• induced by increased energy requirements coinciding with reduced energy intake

• dairy cows in calving, alpacas and llamas in late pregnancy

• high levels of lipid in the blood

urolithiasis

• kidney/bladder stones

• salt precipitates from urine - usually Mg or NH4

• can cause bladder rupture

• ineffective treatments - relaxant drugs or surgery

predisposing factors of urolithiasis

• males more at risk

• diet - high levels of P or Mg

• infection

• genetics - some breeds more susceptible

routes of poison/toxin exposure

• digestion

• skin

• inhalation

definition of a poison or toxin

any substance which disturbs homeostasis

acute effect of a poison

less than 1 week

chronic exposure

longer than 3 months

variable susceptibility

species difference

• cats susceptible to phenolic compounds

• rabbits can tolerate deadly nightshade

• monensin toxic to horses yet food additive to cattle

breed differences

• texel (sheep breed) sensitive to copper toxicity, but blackface likely to suffer from deficiency

previous history of animal - liver/kidney damage

physiological state - pregnancy, weight, age

poisonous plants

most known by 1700s

10-20% of animal poisonings due to plants

drying or ensiling plants may denature poisonous principles

alkaloids

largest group of poisons

4000 different compounds in 10% of all plants

found in all parts of plants

denatured in liver prior to excretion

many have therapeutic uses - analgesics, cardiac depressants, vasoconstrictors

eg ragwort or yew

glycosides

not toxic

can have positive effects

4 types

• cyanogenic

• goitrogenic

• cardiac

• saponins

eg - linseed or buttercups

cyanogenic glycosides

via enzyme - CN to hydrogen cyanide if damaged, affected by Ph

goitrogenic glycosides

affects thyroid function - pungent flavour to prevent consumption, concentrated in seeds

cardiac glycosides

reduces heart rate, widely used in medicine

saponins

haemolyse RBC, in many plants - red clover and horse chestnut - more harmful to fish and snails than mammals

nitrates and nitrites

plants take up nitrate - converted to toxic nitrite when eaten = methaemoglobin causing poor oxygen transport - cattle more prone than sheep, then horses, then pigs - found in beet, rapeseed, turnips

oxalates

found in most plants in varying amounts

greater content in leaves

forms insoluble Ca salts, depleting Ca from the body

pesticides

affects non target animals

can cause

• neurotoxins

• anticoagulant

• gastrointestinal distress

minerals

toxic in excess - can lead to chronic toxicity eg copper

excess accumulates in liver

death due to liver failure

mucous membranes = chocolate brown

mycotoxins

over 500 identified

produced by moulds eg aflatoxin, patin

fusarium toxins - fumosis, trichothecene

compound fracture

one end of bone tears through skin

higher risk of infection

complete fractures

• transverse - straight

• oblique - diagonal

• spiral - halves are twisted

• comminuted - breaks into small pieces

• impacted - one end of the bone is driven into the other

• avulsion - small piece attached to tendon or ligament gets pulled away from main bone mass

incomplete fractures

• fissure - crack in bone

• greenstick - only one side of bone is broken

• depression - broken bone portion pressed inwards

physeal bone

seperation or fragmentation of the epiphyseal plate in growing animals - weak when young

bone fracture healing

• hematoma formation - clotted blood forms inflammatory reaction, cel debris cleared by phagocytes, osteoclasts remove necrotic bone

• soft callus formation - network of spongey bone, fibrous tissue and cartilage formed, bridging sides of fracture

• bony callus formation - ossification occurs, hardening of callus starts peripherally, and moves towards the centre

• bone remodelling - excess spongey bone removed, converted into compact bone

bovine hyena disease

caused by excessive vitamin A administration - uncommon

Degenerative joint disorder

• obesity is a risk factor

• long term deterioration of the articular cartilage - between bones

• can be identified living or post mortem

selective breeding in broilers

skeletal disorders such as spondylolisthesis and tibial dyschondroplasia (weak legs) - associated with rapid growth

brachycephaly

Brachycephalic obstructive airway syndrome (BOAS)

• respiratory distress

• partially associated with a mutation in the SPARC related modular calcium binding 2 gene

• nostril stenosis - narrower

• elongated soft palate - extra tissue that blocks airway

• caudal oversized turbinates = crowded, role in thermal regulation

other diseases associated with brachycephaly

gastro-oesophageal reflux - contents from stomach, can lead to pharyngitis or laryngitis

enraged eyes more susceptible to disease

skin conditions due to excess folds

overbite - inflammation in mouth

brachycephaly in cats

• changes in skull morphology

• engaged soft palates, stenotic nares (narrow nasal cavity), corneal ulcers

spondylocostal dysostosis

• hindquarters reduced in size compared to forequarters - coma like morphology to body

• associated with mutation in Hes family bhlh transcription factor 7 gene - HES7

• rare, animals die before birth

arachnomelia

• thinning of legs and severe angler deformities in distal part of forelegs

• associated with mutation in molybdenum cofactor synthesis step 1 gene in Simmental cattle - MOCS1

• reported in 2 breeds - other breed = different gene affected

• mutation in sulfite oxidase gene in brown Swiss cattle - SUOX

• lethal

brachyspina

shortening of entire vertebra column

long slender legs

mutation in fancomi anemia complementation group 1 gene - FANCI

lethal

complex vertebral malformation

vertebral malformation

fixation of joints in extended or flexed position

mutation in solute carrier family 35 member a3 gene - SLC35A3

lethal

cyclopia

incomplete division of embryonic prosencephalon - doesn’t divide orbits of eye into two cavities

injection of cyclopamine in animals consuming veratrum californicum

lethal

ellis van revel syndrome

• disproportionate dwarfism - shortened twisted limbs

• mutation in ellis van creveld syndrome 2 gene - EVC2

• not lethal

texel chondrodysplasia

• disproportionate dwarfism - shortened neck and limbs

• mutation in carrier 13 member 1 gene - SLC13A1

• non lethal

syndactyly

• single hoof like structure instead of normal paired claws

• mutation in LRP4 gene

• non lethal

cleft palate

• lack of fusion between structures forming palate

• genetic factors, nutritional imbalances, infectious diseases

• non lethal

meningoencephalocele

cyst like swelling in median part of skull cap

cerebrospinal fluid and brain tissues coexist in swelling

genetic factors, nutritional deficiencies

non lethal

kyphosis

abnormal outward spine curvature

mother pigs lacked vitamin D

non lethal

spinal dermoid sinus

vertebral and thoracic limbs malform

non lethal

screening programmes

uses phenotypic criterial to identify affected individuals and exclude them from the breeding pool

useful for polygenic heritable disorders - many unknown genes

efficacy is limited

polygenic inheritance

presence of condition is erratic

both sexes affected

no predictable ratios in pedigrees - unknown number of genes involved

autosomal recessive inheritance

• affected dogs are homozygous for mutant gene

• both parents are heterozygous

tapeworms features

• endoparasite

• Platyhelminthes phylum

• Cestoda class

• 8-25 cm

• head (scolex) and flattened tail (strobilia)

• head has 4 suckers to attach to organs

• strobilia is segmented, most posterior one contains eggs

tapeworm species in horses

Most common - A. perfoliata - caecal tapeworm (digestive)

less common - A. magna - posterior SI

smalles - P. mamillana - anterior SI and stomach

diagnosis of tapeworms in horses

difficult

• faecal egg detection - not reliable for detecting eggs of other endo parasites

• not finding eggs does not mean tapeworm is not present

control of tapeworms

no known drugs for removal - but pyrantel pamoate can affect A. Perfoliata

ivermectin de-wormers can work

most affective drug is pyrantel ebonite - can remove up to 70% of tapeworms

double dose at least once a year - can harm pregnant or breeding animals

taenia solium

pig tapeworm

• up to 7M long - scolex has double row of hooks

• human can serve as definitive and intermediate host

definitive hosts and impacts

human - where adult tape worm sexually reproduces - cysts in brain and other organs, can be life threatening

pig - undercooked meat as worms imbed in muscle

sheep scab

• contagious skin disease caused by mites

• large portion of fleece lost, scratching at area, skin hardens and raw patches develop open to bacterial infection

• lack of rest due to constant irritation

• self inflicted wounds - advance cases death may occur

Psoroptes ovis

• obligatory ectoparasite - causes sheep scab

• spends life cycle on one host

• eggs laid in edges of scab lesions

• spread by contact

• survives for 10-50 days

treatment of sheep scab

scabicides - chemicals which kill sheep scab mite

treat flock with Trt at the same time, twice to kill young mites

sheep blowfly

• main type = lucilia cuprina

• mainly breed on carcass - plenty of nutrients

• native to Africa - has spread to Asia and australia

• blowfly strike - many sheep affected at once - affects 80% of sheep farms each year in uk

lucilia cuprina

• australian blowfly

• lays eggs on soiled fleece or wounds

• larvae lacerate skin using anterior hooks, digests tissue by secreting proteolytic enzymes = secondary infections

preventative measures and treatments for blowfly

• failure to prevent or treat can lead to prosecution

• soaking with organophosphates

• grazing in open pastures and removal of dead animals

sheep ticks

• ixodes ricinus

• transmits 5 disease causing agents - red water fever in cattle, looping ill in sheep

• can transmit disease leading to Lyme disease in humans

life cycle of tick

• needs moisture and shade

• egg, larva feeds for 3-4 days on blood, drops into soil where it stays for many months before emerging as a nymph - attaches to host, feeds, then matures into adult

tick prevention

• pesticides - acaricide in sheep - however resistance is growing

• selective breeding to more resistant livestock

• vaccination of sheep and other livestock against pathogens which can be spread by ticks

liver fluke

• trematode or digenean - class of flatworms with one or more external suckers - fluke

• liver fluke = fasciola hepatica

• can grow up to 30mm

• sheep more succeptible

• usually classified as acute, sub acute or chronic

• causes abdominal pain and diarrhoea

• ulcers, liver damage, haemorrhage

liver fluke life cycle

• adult fluke produces eggs - passed in faeces

• miracidia hatched from eggs - invade snail acting as intermediate host - develops into a sporocyst

• exit snail and swim to vegetation - form metacercariae

• ingested by sheep

diagnosis of liver fluke

• post mortem

• fluke egg count - FEC - eggs in faecal sample

• liver enzymes - raised levels can diagnose acute, and raised GGT levels can indicate chronic

virus definition

small infectious agent - replicate only inside the living cells of an organism, causing disease.

1/100th of a bacterium

bird flu

• mild to severe illness

• caused by greater than 130 types of influenza A virus

• low pathogenic and high pathogenic - low can mutate to high

• wild birds carry low pathogenic virus