12. large animal med- acute/infectious liver disease in LA

what are causes of focal, small areas of damage to the liver?

abscesses

neoplasia

solitary infarctions

how do animals present with focal damage to the liver?

often mild presentation- fever, weight loss, etc.

exception is liver lobe torsion in horses: acute colic and septic peritonitis, usually normal liver enzymes, and diagnosed via surgery or necropsy

what are causes of acute generalized hepatic injury?

toxic, infectious, necrosis, metabolic, inflammation

what are clinical signs/findings of acute generalized hepatic injury?

-often induces signs of failure (hepatitis, cholangitis)

-pale, usually large and friable liver

-significant serum chemistry changes

-theilers, lipidosis, etc

what are causes of chronic, generalized hepatic injury?

chronic hepatitis conditions

cholelithiasis

EHV 5

when do clinical signs for chronic generalized hepatic injury start to show?

when over 75% of parenchyma is lost/fibrotic

how does hepatic fibrosis/cirrhosis occur?

fibrosis occurs when rate of cell death exceeds hepatocyte regeneration

cirrhosis= widespread fibrosis, nodular regeneration and biliary hyperplasia

what are causes of anatomical or functional hepatic injury?

vascular shunts (cause anoxic damage, and failure to detoxify blood)

what is the most common cause of acute hepatitis and hepatic failure in horses?

theiler's disease (parvovirus acute hepatitis)

what is theiler's disease potentially related to?

sometimes relates to use of equine biologic agents

-equine serum or plasma products

-tetanus antitoxin

-disease occurs 4-10 wks later

what is the signalment of horses that typically get theiler's disease?

adult horses over 2 years old

lactating mares have increased mortality (1-3 months post-foaling)

what are the clinical signs of theiler's disease?

acute progressive hepatic failure over 2-7 days

-jaundice, anorexia, depression

-photosensitization

-yawning, hepatic encephalopathy

-resp. distress, IV hemolysis, laryngeal paralysis

-subclinical cases common

what is the etiology of theiler's disease?

equine parvovirus:

-found in horse with theiler's as well as products they were given before the disease (plasma, tetanus AT, allogenic stem cells)

healthy horse can be viremic and might reflect the main source of transmission

how is theiler's disease diagnosed via laboratory work?

-signs of acute hepatic failure

-history of biologics might be present

-chemistry panel changes

-functional tests (high bile acids and ammonia)

-check for DIC (platelets, PT time, d-dimers)

what chemistry panel changes may be seen with theiler's disease?

increases in:

-bilirubin (often unconjugated)

-SDH, AST (these dominate)

-GGT and ALP

-sometimes dz is too fulminant for big changes

-low BUN and glucose

how do livers appear with theiler's disease on ultrasound?

decreased parenchymal echogenicity and size, heterogenous (from acute necrosis)

what will biopsies of livers with theiler's disease show?

diffuse necrosis, biliary hyperplasia

how will livers with theiler's disease appear post mortem?

enlarged, pale and diffusely mottled liver

somtimes small, 'dishrag' appearance

what is the treatment for theiler's disease?

supportive:

-IV dextrose and electrolytes reduce hepatic energy demand and maintain plasma volume

-plasma (if coagulopathy)

-liver support drugs/ammonia reduction

-corticosteroids controversial (bc caused by virus)

what is the prognosis of theiler's disease?

mortality can approach 90%

death in 5 days or gradual recovery in 7-10 days (recovery may be protracted and incomplete)

how is theiler's disease prevented?

-avoid offending products

-mention risk when giving tetanus antitoxin (encourage routine tetanus prophylaxis using toxoid)

-screen other horses on property

what is infectious necrotic hepatitis (INH)?

aka 'black disease;

-sudden death of grazing animals (sheep)

-toxemia related to clostridium novyi type B

-rupture of SQ vessels causes dark skin (hemorrhage)

what is the epidemiology of infectious necrotic hepatitis (INH)?

ubiquitous: soil, bowel, liver of grazing animals

hepatic damage creates anaerobic environment--> germination, proliferation and production of exotoxins

how can hepatic damage cause INH?

-migrating larvae of fasciola hepatica (common liver fluke)

-other causes: f. magna, d. dentricum, c. teniocollis, liver biopsy

what is the pathogenesis of INH?

1. spores consumed and shed by grazing animals

2. some bacteria cross the gut and disseminate in the RE system (kupffer cells)

3. hepatic damage and anaerobic environment allows spores to germinate, produce exotoxins

what are the clinical signs of INH?

usually sudden death in late summer and fall

fever, anorexia, depression, separation from herd

what is found on necropsy in animals with INH?

-decomposed carcass

-widespread SQ hemorrhage

-blood-tinged body cavity fluids

-swollen and congested liver (focal coagulative necrosis, evidence of fluke migration)

what other diagnostics can be used to diagnose INH?

-gram stain of impression smears of liver (large gram + rods)

-culture is difficult (since anaerobic)

-fluorescent antibody on impression smears

-specific exotoxin identification

what is the treatment for INH?

-usually not indicated

-penicillin or oxytet, supportive care

-vaccinate other ruminants immediately

-possibly mass administration of long-acting abx

how is INH prevented?

-burn, bury, or remove carcasses

-reduce fluke infestation

-vaccination (cost/benefit; time with fluke season)

how can fluke infestation be reduced?

-pasture management

-limit access to natural water sources and canals

-anthelmintics

what is bacillary hemoglobinuria (BH)?

aka 'red water' due to potential occurrence of hemolysis/hemoglobinuria

-->sudden death in ruminants, sometimes horses

what is the etiology/pathophys of bacillary hemoglobinuria?

same as INH but different bacterium; BH is a syndrome of toxemia from clostridium novyi type D infection

exotoxins cause localized hepatic necrosis and IV hemolysis

what are the clinical signs of bacillary hemoglobinuria?

-usually sudden death

-fever, anorexia, herd separation, icterus

-bloody nasal discharge and bloody feces

-hemoglobinuria

how is bacillary hemoglobinuria diagnosed?

usually postmortem

history indicates animal is from an endemic region and vaccination usually inadequate

what is seen post-mortem in animals with bacillary hemoglobinuria?

-advanced decomposition

-blood at body orifices

-icterus, focal SQ hemorrhages, edema

-blood tinged fluid in body cavities and pericardium

-serosal hemorrhages

-characteristic focus of coagulative necrosis in the liver

what may be a differential for bacillary hemoglobinuria causing blood at body orifices?

anthrax

what further diagnostics can be performed to diagnose bacillary hemoglobinuria?

for peracute or unusual cases:

-gram stain impression smears of liver, spleen, blood, and abdominal fluid (large gram + rods)

-fluorescent antibody on impression smears of fresh or fixed tissue

-histopath (numerous clostridial rods in hepatic lesion)

how is bacillary hemoglobinuria treated?

not typically treated due to economics and severity of dz:

-supportive, transfuse if severe hemolytic anemia

-minimize stress and chances of sudden death

how is bacillary hemoglobinuria prevented?

burn, bury or remove carcasses

commercial bacterins/toxoids:

-monovalent or combination

-5-6months protection

-control of liver flukes

which animals do liver abscesses have the greatest prevalence in?

cattle

what is a common cause of liver abscesses in cattle?

erosion of rumen epithelium from high energy diets inducing lactic acidosis

80-97% caused by fusobacterium necrophorum

how do neonates get liver abscesses?

via extension of umbilical vein infection

how do goats get liver abscesses?

usually concurrent disease, esp. caseous lymphadenitis

c. pseudotuberculosis usually isolated

what are the clinical signs of liver abscesses in cattle?

reduced weight gain and feed efficiency

weight loss, decreased milk, fever, anorexia

(usually identified at slaughter/necropsy)

what are the differentials for liver abscesses in cattle?

reticuloperitonitis

parasitism

malnutrition

lymphosarcoma

johne's

what are the clinical signs of liver abscesses in horses?

weight loss

intermittent colic

intermittent pyrexia

what are the differentials for liver abscesses in horses?

abdominal abscesses

cholelithiasis

what are causes of liver abscesses in horses?

streptococcus equi equi (strangles) and corynebacterium (pigeon fever)

what are complications of liver abscesses?

usually afflict cattle:

-caudal vena cava thrombosis

-occasionally compress common bile duct

-peritonitis due to abscess rupture

what are signs of caudal vena cava thrombosis caused by liver abscesses in cattle?

shock and sudden death from abscess rupture

pulmonary thromboembolism with epistaxis, hemoptysis and anemia

what occurs in cattle when a liver abscess compresses the common bile duct?

icterus and photosensitization

how are liver abscesses in cattle suspected/diagnosed?

in cattle, high risk ration should raise suspicion

incidence can reach 95% if high grain, limited forage and no adjustment period

what lab work changes are seen with liver abscesses?

-neutrophilia

-high fibrinogen and globulins

-anemia from hemoptysis and/or chronic infection

-elevated GGT and AST if active hepatic damage

-function tests of limited value, DONT biopsy

which animals is ultrasound essential in to diagnose liver abscesses?

ultrasound in neonates is essential to assess umbilicus

what is the treatment for liver abscesses in cattle?

diagnosis often made at slaughter/necropsy

prognosis is poor in cattle with overt clinical signs (though fusobacterium is very susceptible to abx)

what is the treatment for liver abscesses in horses?

long term antibiotic therapy:

-penicillin or ampicillin combined with rifampin

-TMS combined with rifampin

-metronidazole (never give to ruminants)

what is the treatment for liver abscesses in foals?

surgery (if abscess is significant and in umbilicus)

how are liver abscesses prevented in cattle?

prevention heavily relies on dietary strategies:

-adjust grain over 3-4 weeks

-good fiber source (over 19cm in length)

-approved feedlot abx

-leukotoxin based f. necrophorum vaccine

how are liver abscesses prevented in foals?

colostrum, navel hygiene