Horses Exam

Question 1

What are the physiological mechanisms involve in recrudescence from seasonal acyclicity in the mare? What management strategies are available for hastening recrudescence and what are the main reasons for doing so on TB stud farms?

Answer 1

*Light additional to ambient photoperiod at the end of the day e.g. turn lights on at 4:30pm and off at 11pm– pineal gland signals the hypothalamus through secretion of melatonin. When the day length is shorter, melatonin released by the pineal gland suppresses GnRH synthesis and relase. When the day length is long, melatonin secretion is reduced and the inhibitory influence of melatonin on GnRH synthesis is removed

* Southern Hemisphere Aug 1 is the imposed official birth date of all TB horses. This avoids age changes during the racing season. Breeders try to have mares in foal as soon as possible after the official birth date– 11 month gestation– so start of the breeding season in the Southern Hemisphere is on Sept 1. Only a quarter of the mares are already cycling regularly at this stage, the others are in a period of transitional oestrus.

Question 2

Describe the potential abnormalities associated with the infertile “susceptible” mare, which may prevent her from conceiving or carrying a foal. What strategies would you employ to optimise fertility in a “susceptible” mare?

Answer 2

* Congenital abnormalities- conformational such as vulval seal- lips do not appose properly– air may be aspirated can lead to inflammation–> infection–> transmitted to the uterus–> endometritis*** Management: Caslick operation removing thin strip of mucosa from each side of the vulva & suturing raw edges together

* Uterine tube abnormalities- PGE2 applied to the outside of the uterine tube via a flank incision restored tube patency

*Ovarian tumour- removal

* Endometritis- endometriosis- physical and chemical uterine curettage variable success; infectious endometritis- fungal or bacterial– infusion of antifungal or antibacterial +/- systemic treatment

* AHF- PGF2alpha after 7 days

** Strategies to employ to optomize fertility in a susceptible mare

Special repro exam– Physical exam e.g. vulva conformation, internal exam– palpation and U/S, vaginal exam- manual & speculum.

U/S- assess uterus- diameter, tone, wall thickness, contents (air, fluid, cysts, pregnancy?)/ Ovaries- size and shape, presence of ovulation fossa (lost if ovarian tumor), presence, size, grade of fluctuation of follicles, CL

* Endometrial samples in dioestrous after day 7– cytology and culture

* Uterine biopsy– indicated in prepurchase exams, barren mares, and mares that require expensive repro surgery

Question 3

Discuss the physiological control of parturition. Using your knowledge of the event, what drugs or techniques could be useful in correcting a dystocia in a mare?

Answer 3

* Uterine contractions start after the foetus releases cortisol– the contractions force the placenta against the uterus and a release of oxytocin from the pituitary occurs (Ferguson’s reflex)… this also stimulates the release of PGF2alpha which puts further pressure on the fetal membranes and results in the rupture of the chorio-allantois

* Oxytocin can induce labour

* PGF2alph can also induce parturition

Question 4

Neuroendocrine control of spermatogenesis in the stallion

Answer 4

* LH effects spermatogenic tubules and Sertoli cells– controls the rate at which they release formed spermatozoa into the lumen

* Testosterone and other androgens maintains spermatogenesis– develop and maintain optimal male sexual behaviour as well

* LH, FSH, testosterone and inhibin exert a broad controlling influence over the process of spermatogenesis. Paracrine and autocrine factors within the testis exert a fine tuning influenceon spermatogenesis. Leydig cells produce opioid peptides and receptors for them are found in Sertoli cells.

** Oestrogens secreted by Sertoli cells or Leydig cells appear to play an important role in regulating the cyclic activity of spermatogenic epithelium.

The hormonal requirements for normal spermatogenesis have not been fully clarified. Androgens are

required for the development of the gonocytes to type A spermatogonia. Testosterone is

needed for the reduction division in the division of primary spermatocytes. FSH and

testosterone are needed for the maturation of the spermatid. Probably LH, FSH and

testosterone are all required in optimal balance for quantitative maintenance of normal

spermatogenesis.

Question 5

Maximizing fertility when inseminating mares with frozen semen

Answer 5

* Must be thawed properly

* Frozen sperm are fertile for a shorter period than fresh or chilled due to cell membrane damage suffered in the freezing/ thawing process.

* Mare will require 3 cycles to become pregnant

* Daily U/S exam to determine when the mare has oestrus folds and 3 cm follicle

* Mare is treated with ovuplant at this stage on the morning of Day 1, the mare will be expected to ovulate in the late afternoon of day 3

* Day 1 administer ovuplant (follicle no bigger than 30 mm) (3 cm = 30 mm)

* Day 2: scan to ensure she will not ovulate on her own– check for soft follicle, disappearing oedema

* Day 3- scan to make sure has not ovulated if she has, inseminate anyway

* Day 3- 6 hours later inseminate

* Day 3- 6 hours later– confirm ovulation

** In uterus, more semen

Question 6

Managing twin conception in the mare

Answer 6

* Second scan carried out around Day 28- 30 to detect embryonic viability and to look for twins so they can be dealt with before endometrial cups are formed on day 35.

* Crush one of the twin vesicles manually– best carried out during the mobility phase (prior to day 16). If unilateral twins are detected, it is easier to separate them prior to fixation.

* If found after 50 days– you can try to abort one twin with injection of KCL or penicillin into the foetus thorax– but often this kills both foetuses

Question 7

You have been called to look at a very lethargic 12-year-old Thoroughbred gelding.
Owners indicate that the horse has lost considerable weight in the last few weeks. It
consumes about half a bale of lucerne hay daily. The horse has been wormed every 12
weeks with either “Equest plus” (moxidectin and praziqantal) or “Ivomec” (ivermectin).
When you examine the horse you notice it is in poor body condition (body score 2 of 5),
has a heart rate of 56 beats per minute, respiratory rate 24 breaths per minute and
temperature 38.6 oC. It passes normal manure and has normal gut sounds. A plaque of
ventral oedema is present between the front limbs. On auscultation of the chest there is
a grade 2 early systolic murmur audible on the left side only, loudest over the base of
the heart. Harsh lung sounds are evident in the dorsal lung fields, but no lung sounds are
evident below shoulder level on either side of the chest. A jugular pulse is seen
extending half way up the neck.

* Describe your approach to the investigation and management of this case. Interpretation of the history, clinical and laboratory findings already mentioned, potential DDX, how these could be rejected or confirmed, any treatment you might initiate.

Answer 7

JUGULAR PULSE & FILLING

-W

ith t

he horse’

s head in neutral carriage, it is normal for a

jugular pulse to extend from the level of the thoracic inlet up to a point that is approximat

ely 1/3

of

the way up the neck. A jugular pul

se extending beyond this point is indicative of

cardiac

disease

(and cranial mediastinal masses)

. A normal jugular vein should fill within two to three

seconds after being occluded, and imm

ediately disappear o

nce that pressure is relieved. A non-

distended jugular vein i

s normally not palpable.

There is usually increased central venous pressure

in ho

rses with right sided heart failure, so there is venous engorgement and therefore an engorged

jugular vein.

Question 8

An owner has asked you to look at her 8 yo eventing mare. For the last two weeks the mare has been spelled in a paddock and not observed bythe owner until today. The mare has a pink, fleshy, proliferating lesion approximately 5 cm in diameter protruding from the front of the fetlock area. The lesion is not painful to palpate and the horse is not lame. Describe your investigation and management of this case.

Your answer should include potential diagnoses and how you would distinguish between them as well as treatment options for two of the more likely diagnoses.

Answer 8

* Sarcoid- biopsy- removal– destroy all tumour cells, miminize damage to healthy tissue

Eosinophilic granuloma- non-tumour nodular skin disease of horses- not a common location however. Insect HS. Biopsy. Surgical excision.

Exuberant granulation tissue (proud flesh)- from a previous wound

* Pythiosis- fungus like organism in tropical/ sub-tropical areas… calcified necrotic tissue, exudate and protein, removed in their entirety from the fistulae. Intensely pruritic. Biopsy– treatment is difficult and expensive

Cutaneous habronemiasis- Culicoides HS, Ivermectin + Corticosteroids to control rxn + removal

Viral papilloma- highly unlikely due to the age and presentation- no treatment usually indicated, resolve spontaneously

SCC- unlikely as usually unpigmented areas- surgical excision with wide margins- histopath first

** distinguish between them with a thorough history and look around the stable.

Question 9

An owner has asked you to look at his yearling TB colt which is being prepared for the premium yearling sales. The horse has been noticed to stumble frequently while being lunged over the past 2 weeks and last night he was cast in his box and appeared to have considerable difficulty getting to his feet. The horse is well grown, in good body condition and has superficial skin grazes on the dorsal aspect of both hind pasterns. His heart rate is 32 BPM, RR 10 BPM and his temp is 37.4 C, he is eating well and there is normal fresh manure in his box.

Describe your approach to the investigation and mangement of this case. Interpret clinical data, possible DDX, details of those aspects of the clinical exam that are most likely to assist in establishing a diagnosis, any diagnostic aids you might consider and any recommendations you might make.

Answer 9

DDX: Osteochrondosis- osteochondral (bone and cartilage) fragmentation of articular surfaces in young, growing horses.

• Subchondral cystic lesions in young growing horses

Clinical exam:

• Swelling? Often bilateral if OCD, typical in the fetlock on sagittal ridge of MC/MT3.

Diagnostic aids:

• Radiographs flexed lateromedial view for sagittal ridge lesions, dorsopalmar/plantar views

Recommendations:

• conservative– restrict exercise, restrict diet, monitor radiographically… or if fragmentation present.. arthroscopic removal of osteochondral fragments, arthroscopic debridement of subchondral cystic lesions

Question 10

You have been asked to examine a 3 yo TB colt in full work. Yesterday the horse can in a 1200 m race and came last by 15 lengths with a time of 1 minute 24 seconds. He had won his two starts prior to this, both over the same distance, in times of approximately 1 minute 8 seconds. the horse has a heart rate of 44 bpm, RR of 16 bpm and temperature of 37.6 C. The heart rhythm is irregular and very eratic and the heart sounds grade II systolic murmur audible loudest over the base of the heart. Vary in intensity from beat to beat. There is a grade II systolic murmur audible loudest over the base of the heart. Describe your investigation and management of this case.

Your answer should include an interpretation of the clinical data, any further investigation you might initiate, possible diagnoses, how these might be confirmed or rejected and any treatment you might consider.

Answer 10

Most horses with primary atrial fibrillation exhibit no clinical signs at rest or with moderate exercise/work; however, more strenuous exercise or work may result in evidence of reduced cardiac output. This can be seen in racehorses who are evaluated for a sudden reduction in race performance. In this setting, the clinical signs could also be due to paroxysmal atrial fibrillation, which can be identified only during the exercise period. In horses with primary atrial fibrillation, conversion to sinus rhythm with quinidine at a dosage of 22 mg/kg, PO, every 2 hr until conversion, is still the treatment of choice. The success rate for conversion is greatest in horses with atrial fibrillation of shorter duration. The chance for success is considered excellent if the duration is <4 mo and relatively good if >4 mo, although conversion may take longer and quinidine toxicity is more likely to develop. Horses with atrial fibrillation can also be successfully converted to sinus rhythm electrically (cardioversion). This requires the careful placement of electrode catheters in a pulmonary artery and the right atrium (via the jugular vein) of an awake horse followed by anesthesia. Electrical shocks of increasing intensity are then delivered through the catheters. This method is very successful but is time-consuming and expensive. Most horses can return to successful racing performance after conversion. However, some will revert to atrial fibrillation over time. Conversion to sinus rhythm is not indicated in horses with severe underlying cardiac disease, because the likelihood of conversion, or maintenance of sinus rhythm if converted, is very low.

Question 11

a) factors predisposing to endometritis
b) induction of ovulation
c) retained foetal membranes

Answer 11

a) age, vulva abnormalities (improper apposition of lips), natural service, retained foetal membranes
b) GnRH can induce fertile ovulation in seasonally anoestrous mares but expensive and inefficient. Progestagens administered when a follicle is 20 to 25 mm in diameter. Dopamine antagonists administered to a mare in shallow anoestrous + hCG and deslorelin. LH-like hCG and Deslorelin (GnRH analogue) induce ovulation during oestrous.
c) RFM- should lose them within 3 hours of foaling. After 4-6 hours mare should be attended. Septic metritis can lead to laminitis, septicaemia and toxic shock. Penicillin + gentamycin+ oxytocin+ NSAID (flunixin)… fluids if kidney function is a concern.

Remove manually without forcing and flush with saline until clear.

Question 12

You have been called to a TB filly foal which is recumbent and appears too weak to rise. It was born, unobserved approximately 3 days earlier. It had appeared normal to the owner for the first 2 days of life. Clinical examination reveals a heart rate of 140 bpm, a RR of 40 bpm and rectal temp of 38C. A soft systolic murmur is audible over the base of the heart. A weak suck reflex can be elicited. The MM are slightly jaundiced and dry. The cornea of the left eye is cloudy. There is no abdominal distension, no signs of abdominal pain and normal milk faeces are apparent on the end of the thermometer.

Answer 12

Sepsis is a clinical syndrome defined by the development of a systemic inflammatory response syndrome (SIRS) in response to proven or suspected infection. The condition implies an extensive, whole body insult after invasion of bacteria into tissue or a body fluid or cavity. The presence of viable bacteria in the bloodstream is termed bacteremia. Sepsis and SIRS are two of the most common problems of equine neonates, while bacterial infection accounts for nearly one-third of all foal mortality.

* Penicillin + amikacin sulfate+ Metronidazole (anaerobic)

* Sepsis, VSD, PDA, Tetralogy of Fallot but not the right clinic presentation

Question 13

Write notes on:

a. PGF 2alpha
b. domperidone (Motilium)
c. Oxytocin
d. Altrenogest (Regumate)
e. human chorionic gonadotrophin
f. deslorelin (Ovuplant)

Answer 13

a. Uterus can produce prostaglandin, can cause uterine contraction at a slower rate than oxytocin lasting longer however (5 hours), regresses CLs– can induce oestrous
b. Domperidone is a D2 dopamine receptor antagonist. Can induce ovulation in mares in shallow anoestrous. hCG and deslorelin (GnRH) are used in conjunction.
c. cause uterine contraction, remove fluids through the cercix, treatment of persistent endometritis causes contractions of the uterus, useful at the time of breeding for uterine clearance, enahnces uterine involution possibly
d. Altrenogest is an oral progestagen- can be used to delay oestrous or ovulation– delaying the first post partum ovulation, can be given in an attempt to deliver one live foal even after aborting the other purposefully
e. hCG- ovulation inducing drug, usualling given with deslorelin (GnRH)
f. Deslorelin- used with hCG and Domperidone to induce ovulation

Question 14

A client is adamant he wants his TB broodmare bred on foal heat because it is getting towards the end of the breeding season. What limitations would you put on foal heat breeding and hwat management procedures might you institute to maximize the mare’s chances of conceiving? What alternatives could you suggest to the client?

Answer 14

Foal heat 5-12 days after foaling, average interval post foaling is 10-11 days

Seasonal variation

Decreased pregnancy rates and higher embryonic death– possibly because of uterine involution, uterine infection, large uterine lumen

* Higher if they ovulate after day 10 post foaling versus before day 10

** Individual mare monitoring and selection by rectal and U/S and make sure normal foaling, no RFM, no evidence of metritis or endometritis, ovulation on or after day 10

**You can also shorten the luteal phase with PGF2alpha about 6 days after the first ovulation and breed on a shortened cycle to give more time for uterine involution

**You can give Altrenogest (Progesterone) to delay the first ovulation until after day 10

** Can use oxytocin and/or PGF2alpha to possibly enhance uterine involution

Question 15

Answer 15

Methods of breeding- natural, artificial insemination

Frequency of breeding- once per year due to gestation

Numbers of mares capable of being bred- one stallion 3 mares

Methods of transporting semen to other studs- raw (breed multiple mares from same ejaculate), cooled semen 75% first service conception

Question 16

Answer 16

6 week old TB

Severe left hind limb lameness- sudden

LH swollen to the top of the fetlock

39.5 temp

** Septic arthritis- present with acute onset lameness, pyrexia, +/- joint swelling

**Synovial fluid analysis with arthrocentesiss … Total WCC > 10 x 10^9/L, Protein > 25 g/L, neutrophils > 90%

** radiography– often subchondral bone or physeal involvement

**U/S detect fibrin, swelling in deeper joints

** CT if you were going to do surgery

Treatment: Broad spectrum antibiotics, treat failure of passive transfer, lavage joint space, debride affected bone

Prognosis is guarded if bone is involved

Question 17

a) Briefly discuss the diagnosis, prevention and treatment of endometritis

Answer 17

Diagnosis- Clitoral swabbing, endometrial culture and cytology > 5 neutrophils per field, inflammation is present, uterine biopsy, uterine luminal fluid on U/S

Prevention- oxytocin after foaling, oxytocin or prostaglandin if uterine fluid on U/S during oestrous as predisposed for PMIE

Treatment- Clitoral infections– clitoral fossa packed with antibacterial cream, saline to flush uterine lumen, intra-uterine infusion of antibiotics based on culture and sensitivity, oxytocin to cause uterine contraction

Question 18

b) Describe the behavioural and ultrasonographic signs of spring transition in mares
and indicate how you would advance the onset of cycling

Answer 18

Follicles that do not grow to a mature size

Mare does display heat but not enough oestradiol to induce LH receptor expression and endometrial oedema is weak or not present

Question 19

c) List the indications for performing a Caslicks procedure

Answer 19

* Vulva lips that do not appose properly (endometritis risk)

* as mares age, abdominal muscles lose tone, reproductive tract becomes more pendulous and the dorsal vulva may be pulled forward

* Vaginal abnormalities– downward sloping vagina

* Vulval shelf - severe abnormal conformation

* poor body condition- old, thin mares

Question 20

Answer 20

6 week old TB filly, increasingly lethargic, cough, intermittent bilateral mucopurulent nasal discharge, food material in the nostrils. Suckling normally. 60 bpm HR, rr 48, temp 39.8, lung sounds are harsh, moist rattles on both sides

*DDX: EHV-1, Equine Influenza, Viral infection with secondary pneumonia, aspiration pneumonia, parasitic pneumonia (Dictyocaulus arnfieldi)

* Rhodococcus equi- cough and nasal discharge are inconsistent

• diagnosis: any young horse showing signs of respiratory disease
• clinical pathology- hyperfibrinogenaemia, leucocytosis, increased platelet count
• TTW or BAL
• thoracic radiographs
• Tx: macrolide AMs 4-10 weeks + supportive care
• Prevention- manure removal, prevent over crowding, reduce dust

Question 21

Answer 21

TB yearling sternal recumbency, no evidence of colic, interested in eating and drinking, HR 36 and RR 12, temp 37.2 normal heart lung and gut sounds. Can get up but doesn’t remain standing. Fascicultation of limbs muscles is obvious. Horse taking short steps occasionally buckling at the knees.

* Exertional rhabdomyolysis- over exertion, high grain diets, concurrent illness, electrolyte imbalances, vit E and selenium deficiency

* Lameness exam + physical exam

* CBC and biochem- esp CK and AST and electrolytes, urinalysis (myoglobinuria?)

Muscle biopsy not likely necessary

Treatment: fluid therapy, relieve muscle pain with NSAIDs, sedation if necessary (ACE), Diet- goo quality hay with little or no grain, rested with light walking once stiffness has resolved

* If develops into chronic rhabdo: Blood samples– baseline CK and AST and electrolytes– exercise test 2 minutes wakling followed by 13 minutes trotting on a lunge line… post CK measurement at 4-6 hours after exercise.

Question 22

a) The origin and physiological function of equine chorionic gonadotrophin (eCG).

Answer 22

Endometrial cups formed on Day 35– leutotrophic properties leading to the formation of accessory/ supplementary/ secondary CL from ovarian follicles which develop during early pregnancy. This source of progesterone is aiding in the maintenance of pregnancy.

Question 23

b) The elements and expected normal values of a breeding soundness examination in
a stallion.

Answer 23

1. general physical exam- observation of sexual mating and ability to mount, venereal disease? infectious disease?, serology, CEM hormonal assays
2. examination of external reproductive organs- normal penis, normal testicles and scrotum– scrotal size 5-15 cm (scrotal calipers across their width and length)
3. examination of internal reproductive organs- pelvic urethra, body of prostate, seminal vesicles (size, consistency, lobulation, symmetry), bulbo-urethral glands, ampullae of vas deferens- diameter, consistency
4. semen collection and evaluation- 7 billion spermatozoa, >60% motility, bacterial cultures, pH of semen may indicate incomplete sperm release or infection, sperm morphology

Question 24

d) The mechanism of action of Ovuplant™ in inducing ovulation in the mare. What
are possible reasons for prolonged inter-ovulatory intervals and occasional
acyclicity in Ovuplant™-treated mares?

Answer 24

* Ovuplant is a GnRH analogue

* Induction of ovulation is widely used because of the long and variable interval from the onset of oestrous to ovulation

* Persistent Mating Induced Endometritis with infection for more than 4 or 5 days, the embryo can be aborted with a premature release of PGF2alpha, with a decline in progesterone and shortened inter-ovulatory intervals. Susceptible mares.

* Acyclicity in Ovuplant treated mares (delay in return to oestrus)- treated mares had lower circulating LH and FSH after ovulation. Also causes down regulation of GnRH receptors, resulting in reduction of FSH and a delay in development of a follicle wave.

Question 25

e) The origin of oestrogens during pregnancy in the mare and their relation to fetal
viability.

Answer 25

* Conceptus of the mare has the enzyme systems capable of oestrogen production and day 12 and day 13 conceptus membranes have been shown to produce oestrogens in culture

* Oestrogens also come from the primary CL between days 35 and 40– associated with onset of ecG

* Around day 60 the foetal placental unit graudally increases the oestrogen levels

* Gonads of teh fetus provide oestrogen precursors (DHA) converted to oestrogens by the placenta and conjugated in the liver of the mare

**estrone sulfate and total estrogens in blood, milk, urine or feces have been used for the diagnosis of pregnancy and as an indicator of fetal viability since some of the oestrogen comes from the foetus

Question 26

f) The causes and treatment of endometritis in “susceptible” mares

Answer 26

* Natural service–> inflammation of endometrium due to organisms induced–> most mares resolves 24-48–> if infection persists 4 or 5 days embryo will enter unsuitable environment and will not survive–> in these mares premature release of PGF2alpha with a decline in progesterone and shortened inter-ovulatory intervals–> susceptible mares

** They are unable to elminate introduced microflora in time–reduced physical drainage from the uterus, inflamm modulators do not successfully suppress the physiological inflammation within 48 hours

Tx: clear the uterus of fluid and lavage with saline (catheter via the cervix), oxytocin to aid in clearance of the uterus, antibiotic infusion into the uterus

Question 27

1. What are some ways to induce oestrus in anoestrus mares?

Answer 27

* Termination of the luteal phase of the cycle using prostaglandins to induce oestrus

* Additional light treatment

* GnRH can induce fertile ovulation in seasonally anoestrous mares

* Progesterone if the mare is in transitional oestrous

*In responding mares, domperidone isgiven until ovulation occurs. Ovulation

-inducing drugs such as hCG (Chorulon™) and deslorelin

(Ovuplant™) are used in conjunction with domperidone.

Question 28

1. How does an autumn follicle (anovulatory haemorrhagic follicle) differ from a corpus haemorrhagicum?

Answer 28

Anovulatory haemorrhage follicles (AHF) are follicles which fill with blood but fail to ovulate. They eventually luteinize but may persist for several months if not treated with PGF2alpha and can therefore prolong the interoestrous interval significantly.

MOre than one PGF2alpha injection might be necessary 7 days after formation

They are more frequent towards the end of breeding season

Question 29

1. What are some of the differentials for functional infertility?

Answer 29

* Anoestrous

• GTC tumour
• retention of endometrial cups
• silent heated
• missed oestrus
• chromosomal abnormality
• negative energy balance
• seasonal
• drugs– illegal anabolic tx, progesterone

* Abnormal cycle length

• ovarian cysts
• persistent CL
• AHF
• endometritis resulting in early release of PGF2 alpha

* Regular cyclicity

• fertilization failure
• EED
• Ovarian haematoma

Question 30

1. List some differentials for early embryonic death in horses.

Answer 30

* Abnormal hormones– luteal insufficiency

* Embryo quality–aged gametes or chromosomal abnormalities

* Uterine environment– endometrial fibrosis, endometritis, uterine cysts

Question 31

a. The origin of oestrogens during pregnancy in the mare and their relation to fetal viability.

Answer 31

* Conceptus of the mare has enzyme systems capable of oestrogen production and day 12 and day 13 conceptus membranes have been shown to produce oestrogens in culture

* surge in oestrogen production between days 35 and 40 in pregnant mares from the primary CL associated with eCG production

* Foetoplacental unit more gradual increase in oestrogen levels from around day 60

* Gonads of the fetus provide oestrogen precursors (DHA) which are converted to oestrogens by the placenta and conjugated in the liver of the mare

* At day 70 oestrone sulphate can be measured in the blood– specific for pregnancy

Question 32

1. How would you approach a dermatological problem in horses? (Diagnostic techniques)

Answer 32

* History–> physical exam–> problem list–> DDX–> diagnostic plan–> treatment plan–> monitoring plan

* Biopsy, excise or incise

* Culture

* Cytology- impression smear

* Trichnogram

* skin scraping

* Fungal culture

* Response to treatment

* Serological assays (Mange)

Question 33

1. You have a horse with guttural pouch mycosis. How would you treat it?

Answer 33

* results in erosion of the wall of the internal carotid artery and/or external carotid artery and maxillary artery

* Aspergillus nidulans isolated

* Diagnosis- endoscopy of the fungal plaque within the GP

Treatment:

* Surgical treatment is the only effective treatment and it is an emergency

* Occluding blood flow from the affected artery to cause regression of the fungal infection prevention of further epistaxis

* Ligate ICA if only medial compartment invovled– occluding blood flow from either side of the lesion

* Balloon tipped catheter is introduced into the artery, advanced past the lesion, inflated and secured OR coil embolism catheter using fluorscopic guidance

* Regression of the lesion usually occurs within 1 week of surgery and topical or systemic antifungal agents are not required

** if nerve is affected– dysphagia can occur– worse prognosis

Question 34

1. You have a horse that presents with epistaxis immediately following exercise. as the clinician once you’ve stabilised the horse, you counsel the o and explain what potential causes of the epistaxis are. Explain briefly why progressive haematomas and guttural pouch mycosis are not on your ddx list.

Answer 34

Guttural pouch mycocis is uncommon in Australia and unassociated with exercise

Progessive ethmoid haematoma– uncommon- unassociated with exercise

Question 35

1. If it was a PEH, how would you manage it medically?

Answer 35

* Chemical ablation via endoscope– inject lesion with 4% formalin on repeated occasions (every 2-3 weeks until the lesion is obliterated or too small to inject)

* Surgical resection is possible with laser ablation– but not commonly available

* Recurrence is not uncommon- annual or twice yearly endoscope examinations are recommended to monitor

Question 36

1. What factors are usually used to make dx for eq skin dz?

Answer 36

* Bald? Crusty? Lumpy? Itchy?

* Systemically well?

* History, geography, location of lesions, treatment or lack there of (parasite control)

Question 37

1. How do you medically manage a case of PI?

Answer 37

* Instability with billowing movements of soft palate without displacement can be seen during exercise with endoscopy– may be a manifestation of the same condition as iDDSP

* Rest, reducing any nasopharyngeal inflammation (systemic DXs, aerosol fluticason), treating any lower airway inflammation and gear changes such as use of a dropped or figure of eight noseband

* Thermal palatoplasty and tension palatoplasty performed via oral approach intend to stiffen the SP – little evidence

* Tie forward is not recommended as could make PI worse by narrowing the nasopharynx

Question 38

1. You do a skin biopsy. Do you place local in and if so where?

Answer 38

Do not use it immediately adjacent to the site due to local inflammatory effects. Regional nerve block or no LA at all.

Question 39

1. Sarcoids freq occur at site of injury T or F

Answer 39

False

Question 40

1. Do you worry when you find a sarcoid, about mets?
2. Suspected cause of Sarcoids?

Answer 40

Locally aggressive– do not really metastasize but can present along a fascial plane distant to the palpable mass

Diagnosis by biopsy– complete excision– with histopathology to ensure complete margins (wide margins)

Suspected cause Bovine Papillomavirus 1 and 2

Question 41

1. List some neoplastic nodular conditions of horse skin along with Tx.
2. What are some non-neoplastic nodular skin lesions in horses and what cause them?

Answer 41

1. Melanoma- surgical excision and cimetidine, squamous cell carcinoma- surgical excision with wide margins checked histopathologically, intralesions cistplatin, cryotherapy
2. Sarcoids– BPV1 and 2, Eosinophilic granuloma- insect hypersensitivity, Viral papilloma- equine papillomavirus, Pythiosis- Pythium insidiosum- fungus like organism, Cutaneous habronemiasis- Larvae of Habronema spp. (flies)

Question 42

1. A 14 month old horse presents to you with tarsocrural swelling. What is the most likely diagnosis and how would you confirm it?

Answer 42

Osteochondrosis– distal intermediate ridge of the tibia

Radiographs looking for cartilaginous lesions, subchondral cysts– RG the contralateral joint

Question 43

1. A client comes to you with his horse who has just been exercised. He believes that the horse, a thoroughbred, has muscle pain. On biochemistry, you see increased creatine kinase activity. What are your differential diagnoses?

Clue: presentation is summarised as ‘acute rhabdomyolysis following exercise’

Answer 43

* Bilateral or multiple limb lameness

* Muscle strain/sprain/tear

* Acute rhabdo

* polymyositis- muscular dystrophy

Question 44

1. Which joint is most commonly affected with osteochondrosis in young horses?

Answer 44

Tarsal osteochondrosis– present with tarsocrural swelling

Question 45

1. Your patient (5 year old broodmare) presents in severe resp distress due to severe arytenoid chondritis. You do an emergency tracheostomy. List three other indications for this procedure in horses.

Answer 45

* Regional lymph node abscessation and swelling, guttural pouch distension–> obstructive diseases of the URT causing dyspnoea

* Tracheal intubation for inhalation anaesthesia and to divert airflow post-op after upper respiratory tract surgery that may be associated with post-op swelling and airway obstruction

Question 46

1. You have been asked to look at a valuable 6-week-old Thoroughbred filly on a large stud. The filly is well grown but the stud manager has noticed she has been increasingly lethargic over the last 3 days. The filly has been heard to cough on several occasions and intermittently a bilateral mucopurulent nasal discharge has been noted. Today food material was noticed in the nostrils as well. You observe the filly suckling normally. She has a heart rate of 60 bpm, respiratory rate of 48 bpm and a temperature of 39.8°C. On auscultation of the chest the lung sounds are harsh with some moist rales on both sides. Describe your investigation and management of this case in detail. Your answer should include potential diagnoses, the findings consistent with each and how you would distinguish between them, as well as prognosis and any treatment you would recommend.

Answer 46

Equine herpesvirus, EI– with secondary bacterial infection

* Oesophageal obstruction- less likely not all the symptoms

*Bacterial pneumonia– most likely R. equi

• clin path- chronic inflamm– hyperfibringogenaemia, culture of TTW, RG with consolidation or abscessation, U/S pulmonary abscesses in the pulmonary parenchyma

* Inflammatory airway disease– stabled??

Question 47

1. A horse presents with poor performance and abnormal resp noises. What are your top two diagnoses? Elaborate the particular forms.

Answer 47

Top 2: Palatal dysfunction including PI and iDDSP

• SP displaces to a position above the epiglottis
• asypmtomatic at rest
• harsh gurgling on expiration

* Recurrent laryngeal neuropathy

• failure to abduct the arytenoid cartilage and vocal fold during inspiration
• hereditary or guttural pouch mycosis, irritant perivascular injection of the jugular vein, various poisons (lead, OPs), toxins that cause polyneuropathy and signs of stringhalt
• nois during exercise– inspiratory whistle or roaring sound/exercise intolerance/ poor performance

Less Common

* Epiglottic entrapment

* Arytenoid chondritis

* Pharyngeal collapse

* Vocal fold collapse

* Aryepiglottic fold collapse

* Inflammatory Airway Disease: non-infectious bronchitis/bronchiolitis

Question 48

1. You’re doing endoscopy on a horse. Go up the nose. You see an ethmoid turbinate. But you can’t clearly see the stalk. Can you guess where it is?

Answer 48

Attaching stalk of the ethmoid turbinate is always ventral– direct scope more ventrally to reach pharynx

Question 49

1. A trainee nurse is concerned that one of the horses is breathing funny. She says his inhalation and exhalation is active- that is- he looks like he is using muscular effort to breath. What do you say/do?

Answer 49

Normal breathing in resting horses is characterised by unique, biphasic, double effort of respiration. It is an active process using the diaphragm and intercostal mm. Expiration is predominantly passive but final phase is achieved by active abdominal effort.

* However I would take a look to see what she noticed– looking for flared nostrils, anxious appearance, extended head and neck

Question 50

1. You are doing resting endoscopy and you need to grade the movement of the arytenoid cartilages. Your horses arytenoid cartilage movements are asynchronous and the larynx is asymmetric at times, but full arytenoid cartilage abduction can be achieved and maintained. Grade the cartilage.

Answer 50

Grade II– 1

Havemeyer grading system (subgrades within 2 and 3)

Question 51

1. Explain how you would do a TTA/TTW
2. Most common complication with TTW

Answer 51

1. Aseptic collection of samples from the LRT for cytological and microbiological studies.

* application of twitch and/or administration of small amount of sedation

* Area over middle or lower trachea (easily palpable tracheal rings) is clipped and aseptically prepared

* Trachea is palpated and stabilized with the non-dominant hand

* Small volume of lignocaine is injected subcut, small stab incision through the skin

* 12 or 14 gauge needle or catheter is inserted throguh the skin incision into the tracheal lumen passing between 2 tracheal rings. Once in the tracheal lumen, the needle should be directed downward

* Sterile 5 or 6 french dog urinary catheter passed through the needle and into the trachea to approximately the level of the carina (catheter should be inserted 50 to 60 cm)

* Sterile fluid (10-20mL) is infused into the trachea and then quickly aspirated

* A sample for culture should be placed in a clot (serum) tube or appropriate media taking care not to contaminate the sample. A sample for cytology should be placed in a tube containing EDTA to preserve cell morphology.

* Remove collection catheter then the needle introducing the catheter

* Skin incision is often treated empirically with topical AMs and covered fro 24 hours

2. Mild cellulitis at the incision site is the most common complication

Question 52

1. What actually causes DDSP?

Answer 52

* Can occur as a temporary problem associated with URT or lower airway inflammation

* In young horses, guttural pouch infection or pharyngeal inflammation may be present

* Not completely understood but many factors that alter the stimulation of mechano, chemo, and baro receptors in the upper airway could be involved– e.g. inflammation, excessive mucous causing more frequent swallowing, increased negative pressure

* Structural abnormalities are present and cause iDDSP by mechanical interference with the seal between the caudal free edge of the SP and the subepiglottic tissue or by causing irritation or pain that stimulates displacement

* MOST CASES- functional deficit involving inappropriate neuromuscular control of SP stability

Question 53

Answer 53

• Systolic murmur audible and most lung sounds on both sides
• Interpret clinical findings already mentioned
  
  • Physiological systolic murmurs due to wide diameter vessels are very common in horses. Represent normal blood flow during early ventricular ejection. Can become more pronounced with exercise due to increased blood velocity.
  • Aortic or mitral stenosis is VERY uncommon cause of systolic murmurs or mitral or aortic regurgitation (also hear diastolic sounds)
• DDX
  
  • iDDSP– 30% of affected race horses do not make an abnormal noise
  • Palatal instability- can occur alone or preced iDDSP– no abnormal resp noise
  • Recurrent laryngeal neuropathy
  • Inflammatory airway disease
  • EIPH
  • Bacterial pneumonia– pleuropneumonia
• Treatment and prognosis
  
  • EIPH– endoscopic exam within 90 minutes after exercise… erythrophages or haemosiderophages in BAL or TTW samples
  • TX: Frusemide reduces severity, rest

Question 54

Normal parameters horse

Answer 54