Management of Disease - Equine

Question 1

What is anaemia

Answer 1

Anaemia is the reduction of circulating red blood cells or reduced haemoglobin concentration. Functionally it is the reduced oxygen carrying capacity of the blood.

Question 2

What is the normal PCV for:

a. hot blooded horses
b. cold blooded horses and ponies

Answer 2

Thoroughbred or hot blooded horse = 35-40%

Cold blooded horse or pony = 25-35%

Question 3

what is so important about the equine spleen?

Answer 3

The spleen stores 1/3 of the horses’ entire blood volume which it can expel when excited, scared or during exercise to increase the PCV by up to 25%. Can compensate for blood loss for a significant while and is also a main store for platelets

Question 4

what are the clinical signs of anaemia?

Answer 4

Tachypnoea, tachycardia, pale mucous membranes, exercise intolerance, collapse, weakness, lethargy. Can sometimes hear a flow murmur due to changes in blood flow upon auscultation

Question 5

What are the clinical signs of hypovolaemic shock

Answer 5

Tachypnoea, tachycardia, hypothermia, cold extremities, weak pulses, muscle weakness, pale, tacky mucous membranes, increased capillary refill time

Question 6

Why is melena so uncommon in horses?

Answer 6

the bacteria in the large intestine break down the blood

Question 7

What is the normal blood volume of a horse?

Answer 7

8% of it’s body weight

Question 8

how much blood can a horse lose before going into shock?

Answer 8

30% of it’s total blood volume

Question 9

What compensatory mechanisms are there for coping with blood loss other than the spleen?

Answer 9

Catecholamines induce vasoconstriction and increase cardiac output

Plasma volume is expanded by increased renal absorption of fluid due to ADH release

Question 10

what is polychromasia?

Answer 10

variation in cell colour

Question 11

what is anisocytosis?

Answer 11

increase in cell size

Question 12

Why is it difficult to determine if anaemia in a horse is regenerative and how can you tell?

Answer 12

Horses don’t have circulating reticulocytes so instead you must take a blood test then take another a week apart and compare the PCV

Question 13

what colour is normal horse serum?

Answer 13

very yellow

Question 14

What test would you use to check for equine infectious anaemia?

Answer 14

coggins test

Question 15

name some causes of acute blood loss anaemia

Answer 15

Epistaxis, uterine artery rupture, guttural pouch mycosis, tumours, rib fracture in foals, thoracic vessel rupture in race horses, mesenteric artery rupture due to strongyle parasites, renal haemorrhage

Question 16

name some causes of coagulopathies

Answer 16

Secondary to sepsis, SIRS (systemic inflammatory response syndrome) or severe liver failure

Question 17

name some causes of haemolytic anaemia

Answer 17

Neonatal isoerythrolysis ( mare has antibodies against foal’s blood group), blood parasites, equine infectious anaemia, oxidant induced haemolytic anaemia due to toxicity (red maple leaf)

Question 18

Name some causes of non-regenerative anaemia

Answer 18

Bone marrow disorders, anaemia of chronic disease – renal failure resulting in reduced levels of erythropoietin, iron deficiency (chronic blood loss), folic acid deficiency (medication)

Question 19

what are the main three causes of anaemia?

Answer 19

Increased destruction, reduced production or blood loss

Question 20

When carrying out a clinical exam what questions should you ask the owner as part of your subjective exam?

Answer 20

Taking a History, questions to ask in addition to the normal ones (has he been eating, drinking, coughing, sneezing, diarrhoea, urinating, defeacating, exercising ok etc):
• How long have you owned the horse
• Was a pre-purchase exam performed before buying the horse?
• Is the horse up to date with its worming and vaccinations?
• When was it last visited by the farrier?
• When was it last visited by the dentist?
• Is this a problem with an individual or with a group of animals?
• Has the horse recently travelled?

Signalment - some horses of a certain breed, age, gender, colour are more susceptible to certain diseases. e.g. grey horses are more susceptible to melonomas and Squamous cell carcinomas are more common in pink eyed animals.

Ponies can be more pre-disposed to hyperlipaemia (abnormally high conc of lipids in blood )and laminitis
Horses are more prone to atrial fibrillation (irregular heart rate due to chaotic beating of the atria causing poor blood flow to the rest of the body), cervical vertebral instability and idiopathic laryngeal neuropathy (dysfunction of the larynx) - roaring horses.

Question 21

When examining the horse from a distance what should you look at?

Answer 21

demeanour, body condition, resp rate, any increased respiratory effort or unusual posture, any unusual behaviour, look at where it is housed, is it eating, what do it’s droppings look like

Question 22

what is the normal rectal temperature of a horse

Answer 22

Temp 36.5 - 38.5 (exercised or hot day) degrees

Question 23

When hospitalised how often should foals be weighed and how much weight should they gain?

Answer 23

Foals should gain 0.5-1kg every day - should be weighed every day when hospitalised.

Question 24

when examining the respiratory tract what should you look for?

Answer 24

Clinical Examination
• Noises — Coughing, Grunting, Stridor
• Nasal Discharge — Serous, Mucopurulent or Sanguinous
• Rate — Influenced by temperature, stress, metabolic
state
• Depth — Increased depth provides better alveolar
ventilation
Pattern — biphasic (both inspirator,’ and expiratory)
• Heave Line — external abdominal oblique muscle
• Nasal airflow — feel for equal airflow
• AUSCULTATION -with rebreathingbag
Scant, moderate or marked to describe quantities
Heave line is also a classic presentation for animals trying to take weight off their feet e.g. laminitis

upon auscultation:
Remember to check the trachea and larynx
Locate point of most intensity if you hear an abnormal noise
Larynx palpable in most horses - feel arytenoid cartilages
• Breath Sounds
— Loud
— Quiet
Wheezes — long sounds
• Crackles — short, sharp popping sounds
Area over which sounds can be heard
• Pleural friction rubs
Constriction of bronchioles - wheezes
Moisture or effusion in the lungs - crackles
Calves with pneumonia - friction rubs
Effusion can cause absence of lung sounds

Nostrils - symmetry, flexible, no mucous , air coming through both, look at nasal mucosa, smell air that comes out of each nostril
Palpate and percuss paranasal sinuses - should be filled with air so sound hollow and check facial symmetry
Larynx - obvious solid structure felt high up in the throat, above this can feel the muscular processes of the arytenoids - should be symmetrical
Palpate traches - rings can be palpated in the upper neck
Auscultate trachea for fluid accumulation

Re-breathing bag - Should increase resp rate significantly - can make it easier to auscultate lungs

Question 25

When examining the cardiovascular system what should you look for?

Answer 25

Rate — Influenced by temperature, stress, metabolic state Rhythm — Regular, regularly irregular, irregularly irregular • Pulse —Quality, deficits Venous engorgement — Jugular pulse, jugular distension Oedema — Limb oedema, ascites Murmurs — Point of Maximal Intensity, Grade 1-6 Regularly irregular rhythm can be quite normal in the horse Increased preload can cause venous engorgement Many horses have functional heart murmurs Check mucous membranes Transverse facial artery, over the heart ( fit horse can feel heart beat) and under mandible can be used to check pulse Heart located quite cranially - straight up behind elbow P on left and T on right

Question 26

when examining the gut what would you look for

Answer 26

Normal to hear background gut noises 4 quadrants - should hear gut sounds in all Right dorsal - caecum - caecal flush - one every minute Auscultate the abdomen - gut sounds should not be high pitched Left: Dorsal - small intestinal movement, Ventral quadrant - colonic movement Right: Dorsal - caecum Vetral - Right ventral and right dorsal colon - soft sounds look for urine and diarrhoea staining around the anus and check muscle tone and integrity

Question 27

when doing a musculoskeletal exam what would you look for?

Answer 27

Forelimb: Palpate limb for swelling, heat pain or deformity - pay particular attention to soft tissue areas Lift the foot - palpate, test movement of major joints The foot - always clean it out thoroughly first, look for evidence of a foreign body, next apply a hoof tester across the entire foot including the heel and across the frog. Also tap the foot to assess for a focus of pain Palpate the leg once more before allowing the foot to fall. Hindlimb: Palpate as for the forelimb, look for digital pulses - exaggerated with some conditions Lift the foot, check range of movement and palpate Clean the hoof, check for foreign bodies, use hoof testers as for the forelimb and tap in all areas Palpate once more before allowing foot to fall ``` Examine horse during movement - At walk - At trot - Turning in a circle - Sometimes on different elevations and ground types Sometimes with a rider ```

Question 28

What are your list of differentials upon an equine clinical exam?

Answer 28

``` Infectious: Virus Bacterial Fungal Protozoa Parasitic ``` ``` Non-infectious: GIN 'N' THONIC Genetic/ developmental Immunological/ allergic Nutritional/ toxic Neurological Traumatic Hormonal Neoplastic Idiopathic/ iatrogenic ```

Question 29

What to look for on diagnostic imaging of the equine leg

Answer 29

soft tissue: - swelling - abnormal presence of air and gas - mineralisation - foreign bodies Bone: - margins - medulary cavity and the cortex - look at the trabecular pattern - look at the bone density - look for areas of bone re-modelling Articulation: - symmetry - joint space - orientation

Question 30

What is Sclerosis

Answer 30

increased bone density can be to wall off infection due to joint stress to protect a weakened area

Question 31

what is osteolysis

Answer 31

decreased bone density | can be due to fracture, blunt trauma, infection or excessive pressure on a joint

Question 32

How can you tell the difference between active and in-active lesions

Answer 32

active lesions have irregular, poorly demarcated, sharp edges in-active lesions have smooth, well defined, rounded edges

Question 33

what are osteophytes

Answer 33

bony projections associated with cartilage degeneration

Question 34

What are enthesiophytes

Answer 34

focal areas of new bone production at the origin or insertion of soft tissue, often caused by stress at the point of soft tissue attachment

Question 35

Name the indigenous poisonous plants

Answer 35

``` v Ragwort - associated with weight loss due to severe liver failure v Giant hogweed v Water hemlock v Foxglove v Bracken v Deadly nightshade v Oak tree and acorns – severe gastrointestinal problems rhododendron ```

Question 36

Name the plants that act as neurotoxins

Answer 36

``` v deadly nightshade v yew v hemlock v oleander v sorghum v flatweed v ryegrass lathyrus sativus (singletary pea) ```

Question 37

Name plants that act as hepatotoxins

Answer 37

v senecio (ragwort) v lantana camara echium lycopsis

Question 38

Name plant that act as cardio-respiratory poisons

Answer 38

fox glove

Question 39

Name the plants that act as dermo toxins

Answer 39

mimosa | leucena

Question 40

Name the plants that act as enterotoxins

Answer 40

oak/acorns | rhododendron

Question 41

What problems does ragwort poisoning cause?

Answer 41

· Hepatotoxins · Un-palatable when fresh but when dried it becomes less distinguishable – beware of it getting into hay · Spring is a time to be vigilant as the small growing plant can often be ingested by the horse. In full bloom when the plant is easily seen it is mostly left alone · Clinical signs are secondary due to hepatotoxicity and include: - Dullness - Depression - muscle tremors and weakness - frequent yawning - blindness - Incoordination - Jaundice - photosensitisation ( agents causing this are usually detoxified by the liver) - head pressing - nasal regurgitation of food and water - inappetence, weight loss and difficulty swallowing - Can also see ventral oedema and coagulopathies. - Laryngeal paralysis is also seen and the horse is generally unresponsive · Very difficult to reverse hepatotoxicity · Pathology often develops gradually – often see damage to the liver parenchyma causing megalocytosis · Treatment of little value if chronic liver damage present and tend to treat symptomatically Control includes uprooting and burning, cutting off the tops to prevent flowering and seeding and spraying herbicide

Question 42

What problems does St Johns wort cause?

Answer 42

· Common in hedgerows and gardens · Causes primary photosensitisation due to a chemical called hypericin · Found in immune booster tablets for people Photoactivated pastern and cannon leukocytoclastic vasculitis is associated with yellow flowers and is increasing in prevalence. Occurs on the shaded areas and goes away when the animals are kept out of sunlight

Question 43

What problem does giant hogweed cause

Answer 43

· Noxious weed | · No specific signs but causes oral irritation and mouth ulcers

Question 44

What problems does Sorgium cause?

Answer 44

· Not very common in this country – grown in tropical countries, crop is harvested and horses are left to graze stalks Causes chronic cyanide poisoning - cystitis and bladder paralysis

Question 45

what problems does oleander cause?

Answer 45

``` · Common in warmer countries · Extremely toxic – affects humans too, contains cardiac glycosides · Clinical signs include: - Diarrhoea - Melaena - Disruptive cardiac arrhythmias - Death often within minutes Limited necropsy findings except possibly the plant in the ingesta ```

Question 46

what problems does false dandelion cause?

Answer 46

- Common plant in stable yards and poorly maintained pasture - Widespread - Normally ingested in low amounts without causing a problem - neurotoxin - Can induce stringhalt in horses – hyperflexion of hindlimb, form of neuropathy, seems to be a breed susceptibility

Question 47

what problems does belladonna cause?

Answer 47

· Causes atropine related signs, blocking muscarinic parasympathetic receptors (mydriasis, tachycardia, dry mucous membranes, colic, shivering and muscle spasm. · More commonly due to atropine drug poisoning so should monitor carefully if giving and use as lower dose and least frequency possible and remember it can cause gut stasis Treat with supportive care e.g. fluids

Question 48

What problems does bracken fern cause?

Answer 48

· Usually has a restricted distribution · Carcinogenic · Has thiaminase activity so clinical signs similar to that of a vitamin B1 deficiency · Clinical signs (bracken staggers): - Anorexia - Cardiac dysrhythmia (cardiac enlargement over time) - Convulsions - Incoordination - Crouched stance, arched neck, feet wide apart - Poor body condition - Clonic spasms · Diagnosis via bracken on the pasture, known ingestion or can be identified due to low blood thiamine · Treatment usually highly effective if caught early enough and given IV thiamine slowly over 7 days, IM also acceptable

Question 49

what problems does mares tails cause?

Answer 49

· Common garden plants in UK · Causes CNS signs Also contains thiaminase so treat with thiamine

Question 50

what problems does acorns and oak cause

Answer 50

· Contains tannins which cause the toxicity, present in the leaves and the acorns · Clinical signs include sudden death, colic, tenesmus and haemorrhagic diarrhoea · Mainly affects the GI tract causes gastroenteritis, haemorrhages in the abdominal cavity and oedema over the pelvic limbs and ventral body wall · Poisoning is rare and some horses don’t appear to be affected · Diagnosis: acorn traces in gut and faeces, can also look at urinary phenolic content to differentiate from other colics · Treatment same as for colic, supportive fluid therapy, analgesia, laxatives, diuresis · Control: fence off oak trees in the autumn or pick up acorns from pasture

Question 51

what problems does hemlock cause?

Answer 51

· Flowers and leaves similar to cows parsley · Flowers are the most toxic – the alkaloid has a nicotine like action – it stimulates then depresses the autonomic ganglia. End result is it paralyses skeletal muscle motor nerve endings · No signs on post mortem · Clinical signs if only ingested small quantities: - Laboured irregular breathing - Abdominal pain - Inappetance - Mouse like odour - Possible cardiac arrest - Depression · Treatment – try to lavage the stomach to remove the plant Prevention by removing plant from pasture is most important

Question 52

what problems does yew cause?

Answer 52

· Evergreen with red berries in autumn – berries not poisonous but seeds within them are. Leaves are also poisonous · Contains alkaloid taxines · Damage cardiac myocytes · Clinical signs: - Trembling - Ataxia - Bradycardia - Hypothermia - Weakness - Dyspnoea - Rapid death · Upon necropsy will see liver, spleen and lungs engorged with dark blood, a distended stomach and inflammation occurring after death for several hours · Diagnosis via clinical signs, history or finding the plant in the ingest upon PM · Prevention – avoid contact with the tree, remove it or fence it off Treatment – try a gastric lavage and give glucose and hydroxycobalamin but may not be in time to treat

Question 53

what are the problems caused by ergot infested grass

Answer 53

· Not as common in this country · Infected grasses with ergot - fungus affecting plant seed · Causes poor vascular function · Clinical signs: - Trembling, unsteadiness and poor muscle coordination - Erratic and anxious behaviour - Trembling around head and neck region Clinical signs worsen if exposure increases

Question 54

What is the difference between a mare and a filly?

Answer 54

a mare is a female over 4

Question 55

What type of breeder are horses?

Answer 55

long day, seasonally poly-oestrus = breed only once a year in warmer months naturally but during this time come into oestrus many times

Question 56

when does puberty occur in the horse?

Answer 56

12-24 months old

Question 57

How many days is the oestrus cycle in a mare?

Answer 57

21 days in total dioestrus lasts around 17 days oestrus lasts 4-6 days within 24 hours of ovulation the mare will no longer be receptive

Question 58

what role does the dominant follicle have in ovulation?

Answer 58

induces ovulation by secreting oestrogen

Question 59

What hormone does the corpus luteum produce

Answer 59

progesterone

Question 60

At what point does the corpus luteum break down if the mare is not pregnant?

Answer 60

after 15 days due to the endometrium releasing prostaglandins

Question 61

What signs will you see during the transitional period from anoestrus to oestrus ?

Answer 61

lasts up o 6 weeks will see multiple small follicles on the ovaries which look like a bunch of grapes the mare may show no signs or show eratic oestrus behaviour

Question 62

What drugs can be used to manipulate oestrus?

Answer 62

``` prostaglandins progestagens oestrogen chorionic gonadotrophin deslorelin ```

Question 63

How does oestrogen manipulate oestrus?

Answer 63

used in teaser mares for AI collection, induces the behavioural signs of oestrus but not true oestrus

Question 64

How do progestagens manipulate oestrus ?

Answer 64

suppress oestrus, used to shorten the length of the transitional period as withdrawal of the drug increases ovarian activity

Question 65

How do prostaglandins manipulate oestrus?

Answer 65

induces luteolysis of the corpus luteum. Oestrus will then commence 3-5 days post injection side efects quite common - colic, sweating, diarrhoea

Question 66

how does deslorelin manipulate oestrus ?

Answer 66

it's a GnRH analogue hormone implant given when follicle is over 30mm induces ovulation within 48 hours in most mares

Question 67

how does chorionic gonadotrophin

Answer 67

given during oestrus to induce recruitment of a dominant follicle, will induce ovulation within 24 hours if follicle is over 35 mm

Question 68

How can oestrus be manipulated using photoperiod?

Answer 68

the breeding season an be brought forward using artificail light need to provide 16 hours of day light, mares will begin ovulating 8-10 weeks later

Question 69

how long is the unfertilised oocyte viable for post ovulation?

Answer 69

12 hours

Question 70

when is the best time to mate to get the best chance of conception?

Answer 70

24-48 hours post ovulation

Question 71

How long is sperm viable for within the mare's reproductive tract?

Answer 71

48 hours

Question 72

Signs a mare is in oestrus

Answer 72

dominant follicle in one ovary uterine oedema - decreases 24 hours before ovulation a soft oedematous cervix behavioural signs

Question 73

Name some common ovarian problems associated with the mare

Answer 73

persistent corpus luteum - prevents oestrus, give prostaglandins to induce ovulation anovulatory follicle - results in prolonged oestrus, follicles increase in size but don't ovulate. Usually regress in 4-6 weeks granulosa cell tumour - nymphomania or stallion like behaviour, or persistent anoestrus. Diagnose via scan or blood test for anti-mullerian hormone. requires surgery

Question 74

What pathogens can cause chronic infectious endometritis

Answer 74

``` strep zooepidemicus e.coli pseudomonas klebsiella yeast / fungi ```

Question 75

What is the treatment for endometritis

Answer 75

uterine lavage oxytocin - repeat dose every few hours intra-uterine antibiotics

Question 76

What is chronic degenerative endometrial disease (endometrosis)

Answer 76

progressive degeneration of the endometrium with replacement by fibrotic tissue major cause of age related infertility pregnancy lessens the progression of this condition

Question 77

What is the length of an equine pregnancy?

Answer 77

336 days average but very variable

Question 78

where does fertilisation of the oocyst occur?

Answer 78

in the ampulla of the oviduct

Question 79

How long does the embryo remain in the oviduct

Answer 79

5-6 days

Question 80

When does the embryo implant

Answer 80

day 15-16, this is also where endometrial cups develop

Question 81

Describe the endocrinology of pregnancy

Answer 81

the CL continues to produce progesterone to maintain the pregnancy at day 35 the endometrial cups start secreting ECG which encourages the formaion of a second CL these maintain the pregnancy for the first 5 months After day 7 the cups start to degenerate and dissapear by day 150 the pregnancy is then maintained from day 200 onwards (CLs regress) by placental progesterone

Question 82

What lab tests can be done to diagnose pregnancy

Answer 82

blood test for ECG from dy 45-90 and to look for oestrone sulphate from day 120 onwards urine sample from day 150 to identify oestrone sulphate

Question 83

At what stage can a pregnancy be detected via manual palpation and via ultrasound

Answer 83

from day 40 | from 10 days with ultrasound

Question 84

Causes of pregnancy failure

Answer 84

``` Early embryonic death - up to day 40 Viral - EHV - EVA - Bacterial - Fungal Twins Maternal illness/stress Foetal abnormalities Umbilical torsion Idiopathic ```

Question 85

Describe the features of equine herpes virus 1

Answer 85

most common cause of infectious abortion, usually late term - 5 months plus spread via respiratory route or via contact with infected discharge and foetal membranes vaccine available to be given at 5,7 and 9 months of each pregnancy

Question 86

Describe the features of equine viral arteritis

Answer 86

notifiabe infected stallions become persistently infected shedders as it resides in the testes mares abort and recover vaccine available

Question 87

Name the pathogens responsible for bacterial abortion

Answer 87

``` strep species e.coli staph species salmonella leptospirosis ```

Question 88

How can abortions be induced

Answer 88

before 3 months an injection of prostaglandins should bring about abortion in 5-8 days after 3 months need repeated prostaglandin injections

Question 89

How can labour be induced in the mare?

Answer 89

inject oxytocin every 15-20 minutes until labour is induced