HORSE MEDICINE Flashcards
fWhat are the top 3 differentials for weight loss in a horse
1) Nutrition (low quantity or quality)
2) Dental Disease
3) Parasite
What are your differentials for a horse with weight loss
1) Increased demand - illness, pregnancy/lactation, increased workload, environmental factors
2) Inadequate intake - low quantity, low quality, low uptake (dental disease or GI disease)
3) inappropriate utilization - liver disease, GI disease (malabsorption or maldigestion, parasites)
What should you do if a horse presents to you with weight loss?
-Measure quantity of feed
-Measure quality of feed consumed
-Check teeth
-Perform a fecal
-blood work, abdominal U/S, abdominocentesis, abdominal x-rays, absorption testing
How do you determine the caloric maintenance requirements for a horse
Maintenance: 0.033 x BWT (kg)
light work: x 1.2
moderate work: x 1.4
hardwork: up to x 1.9 DE for maintencane
Charlie is a 12yo QH gelding weighing 500kg (1100Ib) in excellent health and a couch potato. How many calories does Charlie need per day?
Maintenance: 0.033 x 500kg = 16.7 Mcal/day for weight maintenance
This can be divided to 0.8Mcal/Ib (Hay) or 1.3Mcal/Ib
100% forage diet = 20.8Ibs (2% body weight)
90% forage/10% grains = 18.8 Ib forage / 1.3Ib grain
about 4 flakes a day
T/F: grain is an essential part of the horse’s diet
False- grain is not an essential part of the equine diet
*Cornerstone of the diet is hay
Hay should meet as mich of the horse’s protein, energy and fiber needs are possible
T/F: all hay “flakes” are created equally
False
but a flake of small bale hay is about 5Ibs
A flake is about
5 pounds of hay- not all are created equally
The digestible energy and nutritive value (quality) of hay is dependent on the
plant maturity at the time of harvest
Hay analyses look for
Increased in Crude protein
Decreased in acid detergent fiber (ADF: lignin and cellulose (digestibility of nutritionist))
Decreases in neutral detergent (NDF: structural carbohydrates)
Alfalfa that is in early bloom has _________ calories/pound, ________ crude protein, and ______ Ca2+ than alfalfa in full bloom
Early bloom: more calories, more crude protein, more calcium
What hay has the highest Crude protein
a) alfalfa (early bloom)
b) alfalfa (full bloom)
c) orchard grass (early bloom)
d) timothy (early bloom)
alfalfa (early bloom)
What hay has the highest mcal/Ib
a) alfalfa (early bloom)
b) alfalfa (full bloom)
c) orchard grass (early bloom)
d) timothy (early bloom)
alfalfa (early bloom)
What hay has the highest Ca++ %
a) alfalfa (early bloom)
b) alfalfa (full bloom)
c) orchard grass (early bloom)
d) timothy (early bloom)
alfalfa (early bloom)
How often do you need a horse
If possible allow access to feed (hay) 24hrs/day
Preferable feed small meals frequently
Lily is a 4yo TBH mare weighing 450kg (1000Ibs) that is a race horse- hard to keep weight on her. How many calories does Lily need per day?
0.0363 x 450kg x 1.9 = 31Mcal/day for maintenance weight of heavy exercise animals.
Hay= 0.8Mcal/Ib
100% hay diet = 24.8 Ibs hay/day
Grain 1.3Mcal/day
70% hay diet = 17.36 Ib hay/day ; 30% ???
How many calories does hay typically have in it
0.8Mcal/Ib
How many calories does grain typically have in it
1.3Mcal/Ib
How can you add more high fat content into a horse’s diet, which is popular for equine athletes
-Vegetable oils
-Linseeds
-Ricebran
High fat diets in horses, like with vegetable oils, linseeds, and ricebran spares the use of _____________ and increases the use of ___________
this leads to less production of lactic acid and heat during exercise
spares use of glucose/glycogen and increases the use of body fat
*Requires an adaption period of 3 weeks
How long does it take for a horse to adapt to a high fat diet to spare the use of glucose and increase the use of body fat and reduce excitable behavior in horses
about 3 weeks
What effect does carbs (certain grains) have on a horse’s behavior
certain grains can make horses hot
Dietary fats (corn oil) reduce excitable behaviors in horses
Vegetable oils, such as corn oil, may offer natural protection against__________
gastric ulceration
What are the benefits and disadvantages of using a fat supplemented diet in horses
Pros: energy density, no mastication required, less risk of GI disturbance, behavioral benefits, GI protection (ulcers), glycogen sparing effect
Cons: weight gain, reduced palatability, cost, messiness, shelf life (unsaturated FA), insulin sensitivty?
Vegetable oils vary in terms of proportions of
1) Saturated vs unsaturated fatty acids
2) Omega 3 vs omega 6 fatty acids
Canola, corn, flaxseed, olive, soybean, and sunflower are all types of
vegatable oils
differ in their proportions of saturated vs unsaturated fatty acids and omega 3 vs omega 6 fatty acids
Why do we not just feed horses more grain
health problems associated with feeding large grain meals
Digestive disturbances: colic, colitis, diarrhea, gastric ulcers, laminitis (endotoxin)
Metabolic: laminitis (insulin resistance), tying up, obesity, hoint disease, hyperlipemia
How do oats differ from corn
Oats: palatable, best nutrient balanced, starch is foregit digested, “sugar high”
Corn: denser than oats (overfeeding), not nutrient balanced, starch mostly hindgut digested (hindgut acidosis and colic) unless processed
Are oats or corn more likely to cause a sugar high
oats
Are oats or corn more likely to cause hindgut acidosis
Corn- it is mostly hindgut digested (oat is foregut digested) corn needs to be processed
Forage based diets are typically deficient in
trace minerals (copper, zinc) and vitamins
provide vitamin/mineral supplements to the diet
YOu should limit concentrates to about
3Ibs/meal (if they are even needed at all)
To increase the energy content of a horse’s diet ________
supplement with fats, rather than carbohydrates
________ can be fed to a horse whole while ______ needs to be processed
oats ; corn
Asa general rule of thumb, you should aim for approximately _____ percent of a horse’s BW in hay/day
2%
What are good indicators of hay quality
Numerous factors affect the quality of hay and include the type of hay, maturity of the plant at harvest, season of harvest, handling of the crop during harvest and storage condition.
In general, the characteristics of good quality roughage include high leaf-to-stem ratio, fresh smell and appearance, cleanliness, and natural color. Despite the fact that these characteristics are good indicators of quality, hay should be analyzed to determine its actual nutrition content especially if it is being fed to horses suffering from endocrine/metabolic conditions.
The following statement is TRUE or FALSE?
Grain is not an essential part of the equine diet.
True
Despite the fact that many horse owners consider a normal equine diet to consist of hay and grain(s), grains are not an essential part of a horse’s diet. Forage (e.g. pasture, hay) should meet as much of the horse’s proteins, energy, and fiber needs as possible.
When additional energy is needed, it is safer to use fats and fermentable fibers before grains. Modern feeds with added fat and digestible fiber are recommended over high-starch feeds.
T/F The starch contained in whole corn is mostly hindgut digested, thus increasing the horse’s risk of developing hindgut acidosis.
True
Most of the starch (72%) from whole or cracked corn is not digested in the foregut and proceeds to the hindgut where it is rapidly fermented. That process results in the production of lactic acid, which lowers the large intestinal pH (=hindgut acidosis) which can result in bacterial death and endotoxin release. For these reasons, corn should be processed (e.g. ground, pelleted, extruded) for all horses, and pelleted feeds should not contain more than 25% of corn.
Please calculate the energy needs for a 1,200 lbs horse with a normal metabolism that performs a moderate amount of work.
How many flakes of grass hay would you need to feed to provide 100% of this horse’s energy needs?
The energy requirements for a 1,200 lbs horse (=545 kg) with a normal metabolism (0.0333 Mcal/kg) and a moderate workload (X 1.4) are the following:
1.4 X 545 kg X 0.0333 Mcal = ~ 25.4 Mcal/day
Additional information needed:
1 lbs of hay contains approximately = 0.8 Mcal/lbs
1 flake of hay weighs approximately = 5 lbs
The number of flakes of hay this horse needs to be fed to cover 100% of its energy needs is:
25.4 Mcal/day /0.8 Mcal = 31.76 lbs of hay
31.76 lbs / 5 lbs = 6.35 flakes ~ 6 flakes of hay
What are the clinical signs of equine esophageal disease
-Dysphagia
-Frequent swallowing
-Coughing
-Hyper-salivation (ptyalism)
-regurgitation of feed (mouth, nostrils)
-Anxiety, neck stretching
-Swilling, emphysema
T/F you should use barium if perforation is suspected
False- do not use barium if perforation is suspected. barium within the tissue can cause inflammation
What is nasogastric intubation in a horse used for
passage of nasogastric tube can help determine if there is an obstruction present. If esophageal obstruction (choke) is suspected, care should be taken not to damage the mucosa.
can sometimes be passed beyond the obstruction and enter the stomach, giving false impression that either an obstruction did not exist of had been relieved. Esophageal perforation at obstructed site may also allow passage of tube beyond the obstruction. If the perforation is cervically located, the tube may ass subcutaneously to the thoracic inlet
What should you be careful for when doing nasogastric intubation to check for choke
avoid causing more damage to the esophageal mucosa
What is the color of the normal esophageal mucosa
whitish-tan to slightly
The esophagus is normally _______ when coated with the barium solution, allowing visualization of the smooth, longitudinal folds
collpased
What should you give a horse for sedation when performing a good oral examination
-A2 agonists - Xylazine or Detomidine
-Acepromazine
-Buscopan-muscle relaxant
-Methocarbamol (Robaxin)
-Lidocaine (topical)
Why is the use of atropine for oral examination controversial
it will only relax the smooth muscle of the distal 1/3 esophagus, which is not where the chokes usually occur. also risk for colic (GI ileus)?
What is the most common esophageal disorder in horses
esophageal obstruction- usually due to intraluminal impaction
The proximal 2/3 of the horse esophagus has no serosal layer, meaning it
takes longer to heal
What are vital structures adjacent to the esophagus that are at risk with choke
-Vagosympathetic trunk
-Recurrent laryngeal nerve
-Carotid artery
High choke means there is is an esophageal obstruction in the
cervical part of the esophagus- at risk for aspiration pneumonia
Low choke means there is an esophageal obstruction in the
thoracic inlet
Intrathoracic choke is rare but it means that there is an esophageal obstruction in the
lower esophageal sphincter
How do you treat esophageal obstructions in horses
1) Sedation/Muscle relaxation (Xylazine/ Detomidine or Acepromazine and then allow a nasal gastric tube to help pass the obstruction into the stomach. Avoid pressure if not removed do lavage
2) Lavage
3) Drugs : NSAIDs, antibiotics (broad spectrum if aspiration)
4) Support: treat dehydration and electrolytes, treat esophageal inflammation and aspiration pneumonia. Horses with excessive salivation will have hypochloremic metabolic alkalosis - give 0.9% NaCl
T/F you should use lubricating agents, such as mineral oil and softening agents (DSS) during lavage to relieve esophageal obstructions in horses
False- they are contraindicated - cause granulomatous pneumonia because they are non-degradable
What are the predisposing factors of esophageal obstructions in camelids
The bosses that are dominant
greed eaters
pelleted foods
How do you treat esophageal obstructions in camelids
needle trocar if bloated
sedation
antibiotics if aspiration occured
prolonged salivary salivary loss: metabolic derrangements
may need general anesthesia/intubation/gentle lavage
may follow choke
results in weight loss, regurgitation, recurrent choke, recurrent bloat
most are idiopathic but can result from organophosphates and myasthenia gravis
Megaesophagus
What solution should you use when doing lavage to dislodge an esophageal obstruction
warm water, preferably with 0.9% sodium chloride solution
Which of the following clinical signs is NOT found in a horse with esophageal disease?
Dysphagia
Ptyalism
Diarrhea
Stretching of neck
Coughing during swallowing
Diarrhea
The hallmark of esophageal disorders in the horse is dysphagia. Additional clinical signs, particularly for proximal esophageal disorders, include frequent, ineffectual attempts to initiate swallowing, coughing during swallowing, ptyalism (excessive salivation), and nasal regurgitation of feed mixed with saliva. Other clinical signs include anxiety, restlessness, and stretching of the neck.
The following statement in TRUE or FALSE?
An esophageal feed obstruction (choke) should be treated as a medical emergency.
True
Esophageal obstruction should be considered an emergency because prolonged pressure on the esophageal mucosa by the obstructing material can result in extensive tissue damage, with subsequent scar tissue formation and stricture.
Treatment of a horse with an esophageal obstruction (choke) typically consists of administration of heavy sedation, passage of a nasogastric tube, and gentle lavage with warm water.
What is/are the goals for administering sedation?
Relaxation of the esophageal musculature
Allowing safe handling of the horse
Reducing the risk of fluid aspiration when lavaging
All of the above
All of the above
the margo plicatus is a
distinct margin that separates the non-glandular and glandular portion of the stomach.
has stratified squamous epithelium and serves to contain the horse’s food without aiding in the chemical breakdown of the ingesta
non-glandular portion (squamous mucosa)
What are the 4 types of secretory epithelial cells that horses have on their glandular mucosa. What do they secrete?
Mucous cells: secrete an alkaline mucous
Parietal cells: secrete HCl
Chief cells: secrete pepsin
G cells: secrete gastrin
How might equine gastric rupture occur
abnormalities which interfere with the normal aboral movement of fluid through the small intestine may cause the accumulation of fluid in the stomach. Severe gastric dilation can occur and then rupture if not reated
What allows there to be a one-way valve in the equine stomach
the anatomic arrangement of the esophagus and cardia
What kind of horse is gastric ulceration more common in
race horses
What causes gastric ulceration in a horse
an imbalance betweeh the mucosal aggressive factors (HCl, pepsin, bile acids, and organic acids) and the mucosal protective factors (mucus, bicarbonate, and mucosal perfusion)
Mucosa is damaged by excessive exposure to HCl and pepsin. Non-glandular mucosa response to acid irritation by increasing thickness of its keratin layer- only providing minimal protection.
Causes: Anything that impairs mucosal lining, NSAIDs, Stress, Impaired gastric blood flow, reperfusion injury
What is the predominant stimulato to hydrochloric acid secretion
gastric, histamine, and acetylcholine via the vagus nerve.
Gastric- g cells within the gastric glands
histamine- mast cells and enterochromafin-like (ECL)
Ingestion of feed stimulates acid secretion in horses, what is also stimualted by eating to buffer the acid?
bicarbonate-rich salivary secretions
What are the protective factors of equine stomach, secreted by the glandular portion
Mucous cells: alkaline mucous coating mucosa like a gel
also increased PGE2 secretion
What portion of the equine stomach is most sensitive to acid induced injury?
The squamous epithelium (non-glandular) less mucosal protective properties (thick mucus and bicarb later like glandular mucosa has)
What are the 5 causes of gastric ulcerations in horses
1) Strenuous exercise - less blood flow and increased acid contact time
2) Stress/illness- decreased PGE2, blood flow, and mucous with increased HCl
3) NSAIDS- Decreased PGE2, blood flow and mucous with increased HCl
4) Feeding- Lenght of meal, type of feed (saliva production, gastrin release, calcium content)
5) infectious causes- H. pylori
What might be an infectious cause of gastric ulceration?
Helicobacter pylori (sporadically been found in horses with gastric ulceration)
What are the clinical signs associated with gastric ulceration in adult horses
colic, poor body condition, poor hair coat, poor performance, changing appetite, attitude changes, “girthiness”, back pain
What is the difference in clinical signs of gastric ulceration of foals vs adult horses
Foals get diarrhea, excessive salivation (1-4mo),
f*oals can perforate
What are the clinical signs of gastric ulceration in foals
colic, teeth grinding, DIARRHEA, excessive salivation, reduced appetite
What can be unreliable tests for gastric ulceration in adult horses
Fecal occult blood test and constrast radiography
*Testing for fecal occult blood is only of value in young foals isnce the colonic microflora throughly digest hemoglobin
How do you treat gastric ulceration in horses
Management- avoid stress, allow access to feed 24hours/day preferable feed small meals frequently, vegetable oils may offer natural protection against ulceration
Medical to decrease gastric acidity and improve mucosal protection
Antacids- Mallox,
Proton pump inhibitor- omeprazole
Anti-histamines (Cimetidine, Ranitidine, Famotidin)
Mucosal protectants- Sucralafate, bismuth subsalylate, misprostol
PGE2 analog- Misprostol
What are drugs that serve as mucosal protectants for gastric ulceration
Sucralfate (bandage to unprotected surface, immediate pain relief, does promote healing, does not alter gastric pH, does not prevent ulceration)
Bismuth subsalicylate
Misoprostol (Synthetic PGE2 analog
serves as a bandage to unprotected surface, immediate pain relief, does promote healing, does not alter gastric pH, does not prevent ulceration
Sucralfate
Misoprostol is a
synthetic PGE2 analogue used to help gastric ulceration
Misoprostol is a synthetic prostaglandin E analog and has been shown to be effective in the treatment of gastric ulcers in humans and horses. The proposed mechanism of action involves both inhibition of gastric acid secretion and mucosal cytoprotection. Reported adverse effects include colic and diarrhea.
What is omeprazole’s mechanism of action
inhibiting proton pump which is the final pathway in hydrochloric acid secretion used to help with gastric ulceration
What is the prognosis for gastric ulceration
Good: if only squamous mucosa and management changes
Fair: if glandular mucosa
Poor: if perforated
What is the only definitive diagnostic for gastric ulceration
Gastroscopy
While a presumptive diagnosis of gastric ulceration is often based on the presence of age-related clinical signs and response to therapy, gastroscopy is the only definitive diagnosis currently available. Diagnostic procedures aimed at the detection of fecal occult blood or plasma protein (e.g. albumin) are unreliable.
True or false: duodenal ulcers and strictures are more common in adult horses than foals.
False: they are more common in foals.
What is the primary H2 antagonist used in horses with gastric ulcers?
Ranitidine
80% of equine gastric ulcers occur in which part of the stomach?
Squamous
The parietal cells in the glandular mucosa of the stomach produce the gastric hydrochloric acid.
Which of the following does NOT stimulate cellular HCl production?
A) Histamine
B) Prostaglandin
C) Acetylcholine
D) Gastrin
Prostaglandin
Which of the following is considered to be (a) factor(s) in gastric ulcer formation in horses?
Choose all that apply
Decreased PG E2 production
Increased mucosal blood flow
Large grain meals
Feeding alfalfa
Decreased mucosal blood flow
Decreased mucous production
Decreased PG E2 production
Large grain meals
Decreased mucosal blood flow
Decreased mucous production
Factors that have been implicated in gastric ulcer formation in horses include inhibition of prostaglandin E2 synthesis (e.g. by NSAID administration and stress). PG E2 increases blood flow to the stomach mucosa, promotes secretion of bicarbonate-rich mucus (which creates a lumen-to-mucosa gradient in pH from 1.5 to 6.5), and decreases acid secretion. In addition to decreased synthesis of PG E2, other factors that impair gastric blood flow (e.g. intense exercise) may also contribute to ulcer formation. Mucosal capillary perfusion is an integral component of mucosal protection, since disruption of mucosal perfusion readily produces ulcerations. Cellular restitution refers to the regeneration of surface epithelial cells in response to an irritating substance.
Eating behavior has also been shown to have an effect on the risk of gastric ulcer formation. For example, restricting access to roughage and feeding a large amount of concentrate (which reduces the time spent eating and increases postprandial gastrin release) promotes increased gastric acidity. In contrast, high roughage diets tend to stimulate production of bicarbonate-rich saliva, which will help buffer gastric acid. Concentrates stimulate a greater postprandial serum gastrin response than roughage, thus increasing hydrochloric acid production. Moreover, the calcium contained in alfalfa can act as a natural antacid buffer for hydrochloric acid.
What is the best diet for managing horses with gastric ulcers
Alfalfa- high calcium content acting as a natural antacid buffer for HCl
What is the most common gastric neoplasia in the horse
Squamous cell carcinoma (actually originate from squamous epithelium of esophagus)
How do you diagnose gastric neoplasia like squamous cell carcinoma in a horse
pass nasograstric tube for resistance
neoplastic cells may be found in fluid recovered by gastric lavage
Endoscopy- positive diagnosis and biopsy
laparotomy or laparoscopy
What are the equine liver specific enzymes
SDH- hepatocellular
GGT- biliary
What are the equine liver associated enzymes
AST + LDH: Hepatocellular
AP: biliary
Gamma Glutamyl Transferase (GGT)
a biliary specific enzyme
technically not liver specific (Renal tubules-released into urine; Mammary- secreted into colostrum; and pancreas)
What can release GGT
Liver
Renal tubule cells - into urine
Mammary glands - secreted into colostrum
Pancreas
What enzyme is high in colostrum fed ruminant neonates
GGT
T/F ALT is not useful in large animals
True
How do you differentiate between liver disease and liver failure
liver failure: inability to perform its normal function
1) Nutrient metabolism (Carbs, lipids, proteins)
2) Biosynthesis (protein biosynthesis)
3) Detoxification/Excretion (Bilirubin, blood ammonia, BUN, phylloerythrin)
4) Immunity
5) Digestion
Hepatic encephalopathy is a clinical sign of
liver failure
early: agitation, wandering
late: somnolence, coma
due to increased ammonia and decreased BUN excretion through the urea cycle
May be the first clinical sign of pyrrolizidine alkaloid toxicity or biliary obstruction
photosensitization
photosensitization is most severe on
non-pigmented skin where reactive compounds are most directly exposed to the UV spectrum.
What is the photosensitizing compound created during liver failure
phylloerythrin (normally removed from the liver, after chlorophyll is broken, and then removed by the liver and excreted in bile
Primary photosensitization
associated with photodynamic compounds foind in certain plants (Bishops weed, buckwheat, spring parsley, St Johns wort which are absorbed from the digestive react, react with the nonpigmented skin upon IV light.
associated with defective porphyrin metabolism in liver
Can be seen in liver failure because the liver is responsible for the synthesis of numerous factors evolved in coagulation and fibrinolysis
Coagulopathy/ hemorrhagic diathesis
What are the clinical signs of liver failure in horses
1) Hepatic encephalopathy (early: agitation, wandering/ late: somnolence, coma)
2) Photosensitization
3) Coagulopathy
4) Icterus
5) Weight loss
6) Edema and ascites
What are the 3 causes of icterus in the horse
1) Prehepatic - hemolysis
2) Hepatic- hepatocellular dysfuction
3) Posthepatic- cholestasis
*anorexia
in food animals: icterus is more often due to
likely due to hemolytic disease rather than hepatic and biliary disease
icterus is rare in cows
in horses: icterus is most likely caused by
anorexia, followed by hepatic and biliary disease
exception is foals- do not have enough fat stores, likely neonatal isoerythrolysis or Tyzzer’s Disease
How does equine liver disease result in weight loss
decreased feed intake, anorexia, loss of normal hepatocellular metabolic activites
Why do you get ecchymotic hemorhage, epixstaxis, melena, hematuria, and hemotomas in horses with liver disease
failure to synthesize II, V, VII, IX X
What factor has the shortest half life
Factor VII T1/2= 4-5hours
Will see deficiencies in extrinsic pathway first
Why do you see edema and ascites in horses with liver failure
Hypoalbuminemia,
secondary to vascular thrombis (hyperlipidemia in ponies)
half life of albumin is relative long (19-20 days) edema is a rare clinical sign
Why is edema a rare clinical sign in horses with liver failure
half life of albumin is relative long (19-20 days) edema
Blood concentration of bile acids will be _________ with liver disease
increased.
Serum concentration is not impacted by short term fasting (<14 hours). but prolonged fasting (>3days) will increase serum bile acids of three times the baseline.
What are the most commonly used equine liver function tests?
1) Serum bile acid concentrations
2) BUN
3) Dye elimination test - Bromsulphalein
4) Ultrasound and liver biopsy
What is Bromsulphalein (BSP) used for
A test for equine liver function. A substance that when injected is metabolized in the liver. Heparin tubes are collected 3,6,9,12 minutes.
BSP half life is prolonged when greater than 50% of hepatic function is lost
Why is a bile acid elevation not specific to equine liver failure
They are also increased when there is cholestasis and portosytemic shunting
Are CNS signs typically seen in acute or chronic equine liver disease
Acute
Is weight loss typically seen in acute or chronic equine liver disease
Chronic
Is photosensitivity typically seen in acute or chronic equine liver disease
Chronic
T/F: Chronic equine liver disease will often only have mild elevation of liver enzymes
True: Mild
T/F: Acute equine liver disease will often only have mild elevation of liver enzymes
False: often severe elevation in the liver enzymes
Theiler’s Disease typically impacts
adult horses
Tyzzer’s disease typically impacts
foals
Acute hepatitis in adult horses, acute onset with acute hepatic necrosis, liver failure, caused by viral etiology
Theiler’s Disease
What is the etiology of Theiler’s disease
A mystery but has a viral etiology.
Flaviviridae family- Theiler’s disease associated virus
Equine Parvovirus (EqPV-H) associated with antitoxin?
What is the causative agent of Tyzzer’s disease
Clostridium piliforme
What is the prognosis for horses with Theiler’s disease
guarded
What causes acite hepatitis, 7-42 days, often peracute with no signs of disease, killing foals with fever, anorexia, icterus, seizures, and coma
Tyzzer’s disease caused by Clostridium piliforme
What is the prognisis of foals with Tyzzer’s disease
extremely poor
Use supportive care, fluids, NSAIDs, nutrition, tx for hepatic encephalopathy
Does pyrrolizidine alkaloid toxicity cause acute or chronic liver failure in horses
Chronic liver failure- weight loss, photosensitivation, icterus, hepatic encephalopathy
The most common cause of chronic liver failure in horses in certain parts of the US
chronic megalocytic hepatopathy from pyrrolizidine alkaloid toxicity
Pathogenesis of pyrolizidine alkaloids
pyrroles alkylate nucleic acids and proteins (cross links DNA) stopping mitosis and protein synthesis. Hepatocytes then enlarge, forming megalocytes. When megalocytes die- fibrosis (cirrhosis) occurs
Hepatocytes around portal triad (zone 1) are affected first.
bile duct hyperplasia
can cross the placenta and toxic to the fetus
What area of hepatocytes are impacted first from pyrrolizidine alkaloid toxicity
Zone 1 is affected first (hepatocytes surrounding the portal triads)
What results in megalocytes?
pyrroles alkylate nucleic acids and proteins (cross links DNA) stopping mitosis and protein synthesis. Hepatocytes then enlarge, forming megalocytes.
pyrrolizidine alkaloid toxicity is typically diagnosed by presumptive signs, exposure history and lab evidence of hepatic disease. How do you get a definitive diagnosis
Liver biopsy- look for
1) megalocytosis
2) biliary hyperplasia
3) fibrosis
can also be detected in feed by high-performance liquid chromatography
What species is relatively resistant to pyrrolizidine alkaloids?
Sheep
-pre-graze pastures laden with PA containing plants
What is the prognosis for pyrrolizidine alkaloid toxicity
If fibrosis is present-> prognosis is poor
No treatment available
Serum bile acid concentration greater than 50umol/L is suggestive of grave prognosis
How do you manage a field with tons of pyrrolizidine alkaloid containing plants
Sheep
-pre-graze pastures laden with PA containing plants
Is an icteric horse more likely to be experiencing cholastasis or liver disease
Cholestasis
What is the cause of cholelithiasis in horses?
unknown but
Ascending infection, decreased bile flow and salmonella
What is associated with cholelithiasis in horses?
salmonellosis - ascending infection because they lack and exit port sphincter to prevent backflow of intestinal contents into the biliary tract.
Horses do not have an exit port sphincter in their biliary tract. Why is this clinically significant
salmonellosis and other enteric pathogens - ascending infection because they lack and exit port sphincter to prevent backflow of intestinal contents into the biliary tract.
How do you treat cholangitis/cholangiohepatitis in horses
Supportive care, antimicrobials, NSAIDs, liver support
Surgical approach is better (cholelithotripsy or choledochotomy)
What are the 3 clinical signs of cholangitis/cholangiohepatitis in horses?
1) Cholestais- icterus
2) Colic (recurrent)
3) fever (cholangitis)
What is the prognosis of cholangitis/cholangiohepatitis in horses?
poor if hepatic fibrosis is present.
What are your differentials for chronic liver failure in horses
-Pyrrolizidin Alkaloid toxicity
-Cholangitis/Cholangiohepatitis
-+/- Cholelithiasis
what are possible complication with liver biopsy in horses
hemorrhage
pneumothorax
peritonitis
abscess
*keep in mind they might have prolonged coagulation times with liver failure
What would you see on ultrasound if the horse has hepatomegaly
rounded edge and swollen
What are the intermediate hosts for liver flukes (Fasciola hepatica)
Snails
What causes bacillary hemoglobinuria
toxins produced by Clostridium hemolyticum (Clostridium novyi type D)
What is another name for Clostridium hemolyticum, the causative agent of bacilary hemoglobinuria
Clostridium novyi type D
What are the exotoxins that cause bacillary hemoglobinuria
beta toxin: phospholipase C- necrosis and hemolysis
eta toxin: tropomyosinase
theta toxin: lipase
*Cause hepatic necrosis and intravascular hemolysis
What is the pathogenesis of bacillary hemoglobinuria
spores of Cl. hemolyticum are ingested and cross the intestinal mucosa. spores reach the liver by portal circulation and can persist in the liver tissuw for long periods of time within the Kupffer cells. Following a hepatic insult (liver fluke migration, hepatic inflammation or abscesses, liver biopsy)
Creates an anaerobic environment , spores become activated and germinate, Beta, eta, and theta toxins are produced. causing hepatic necrosis and hemolysis, icterus, hemoglobinuria
In most cases, the liver insult seen in Red water disease by Clostrium hemolyticum (novyi type D) is due to
migration of Fasciola hepatica
What are the clinical signs of bacillary hemoglobinuria?
Hemolysis: Red serum/plasma, hemoglobinuria, anemia (pale mm, tachycardia)
icterus (pre-hepatic)
DIC
blood tinged frother (mouth and nose)
Rectal bleeding, blood in feces
ischemic hepatic infarct
What is another differential you need to rule out when an animal has bacillary hemoglobinuria?
Anthrax (Bacillus anthracis)
How do you diagnose bacillary hemoglobinuria
1) Fluorescent antibody test on impression smears taken from liver infarct for Cl. hemolyticum antigens
2) Necropsy- icterus, red urine, petechia, ecchymoses, red-tinged fluids, ischemic infarct
3) Clinically: anemia, increased plasma protein, DIC (fibrin degradation products, decreased platelet counts)
What does Clostridium novyi type D cause
Bacillary hemoglobinuria
What does Clostridium novyi type B cause
Blacks disease
What are the toxins of Clostridium novyi type B? What do they cause
alpha, beta, zeta (local and systemic effects)
Hepatic necrosis, endothelial damage*, resulting in passage of RBCs into tissue, neuronal damage
What are the clinical signs associated with Black’s disease
Animals usually found dead
Clinical signs are nonspecific
no red urine or external (nose/rectal) bleeding
What is seen upon the necropsy of an animal with Black’s disease
hemorrhage of suncutaneous tissues results in black discolaration of carcass - looks like diffuse bruising of all muscles
Diagnose with impression smear taken from the margin of the liver lesion - revealing numerous large gram + rods. Confirm diagnosis with fluorescent antibody testing to identify Cl. novyi type B should be performed
How do you diagnose Black’s disease
Diagnose with impression smear taken from the margin of the liver lesion - revealing numerous large gram + rods. Confirm diagnosis with fluorescent antibody testing to identify Cl. novyi type B should be performed
How do you prevent Blacks disease
vaccination - last 5 to 6 months
control flukes
How do you prevent Bacillary hemoglobinuria
vaccination - last 5 to 6 months
control flukes
Decreased production is a sign of acute or chronic liver failure in cattle
Chronic disease