L18 - Liver Infections

What’s the difference between liver abscess and necrobacillosis?

Abscess - morphological diagnosis based on the presence of lesions

Necrobacillosis - etiological diagnosis of abscesses caused by F. encrophorum

What is the most common pathogen from liver abscesses?

Fusobacterium necrophorum

What is a subspecies of Fusobacterium necrophorum that can cause liver abscesses? What infection typically is alongside it?

Funduliforme

Trueperella pyogenes

Symptoms of F. necrophorum

• Typically subclinical

• Abdominal pain, grunting

• Abscesses and necrotic infections

• Hepatic Necrobacillosis

• Digital Necrobacillosis (foot rot)

• Oral/laryngeal necrobacillosis of calves

Why is F. necrophorum clinically significant?

• Slaughter condemnation of affected organs

• Decreased feed efficiency

How are liver abscesses treated?

It isn’t usually

• Prolonged Tx with high doses of antibiotics

  • Procaine Penicillin G

  • Oxytetracycline

  • Ampicillin trihydrate

What kind of bacteria is F. necrophorum?

• Gram -

• Rod

• Filamentous

• Anaerobic, but aerotolerant

• Non-spore forming

What are the 4 biotypes of F. necrophorum?

A and B → mostly in cattle diseases

• A: more common, isolated in pure culture, isolated in omst of bovine liver abscess cases

• B: typically isolated with other bacteria (T. pyogenes, Bacteriodes spp., Streptococcus spp., Staphylococcus spp.)

AB and C

What kind of pathogen is Trueperella pyogenes?

• Gram +

• Rod

• Facultative Anaerobe

How does T. pyogenes promote growth of F. necrophorum?

• Synergistic

1. Uses oxygen to make an anaerobic environment

2. Provides iron for growth

What does F. necrophorum release to protect T. pyogenes against phagocytosis?

Leukotoxin

What is the typical target of T. pyogenes?

• Grain fed cattle (occurs secondary to rumenitis)

• All ages and types of cattle and sheep

• Can result in neonates from umbilical infection

Pathogenesis of F. necrophorum

• Normally in upper digestive and respiratory tract

• Lactate is major sugar substrate

• Going from roughage to high grain diets (grain overload) → increase in lactate → acidosis → rumenitis → more pathogen

• Injury at site of infection (ex. liver)

• LPS and Leukotoxins (neutrophils, macrophages, hepatocytes and rumen epithelial cells) for penetration and colonization

• Invade hepatic portal system → got liver

What is the primary cause of F. necrophorum in dairy and feedlot cattle?

Feeding high carbohydrate rations

What causes abscesses as a result of F. necrophorum?

Vascular drainage from primary lesion into the portal vascular system → embolic translocation → entraps bacteria in the liver capillary system

Clinical pathology of F. necrophorum

• Luekocytosis → neutrophilia

• Chemistry and liver tests will NOT indicate abscesses → only shows liver injury

What are the tests results of T. pyogenes?

• Hemolysis +

• CAMP +

How are liver abscesses controlled?

• Feed management → prevent rumenal acidosis

• Prophylactic antimicrobials

• Vaccines

• Tylosin Phosphate → reduces liver abscesses, and increases feed efficiency

Are infections by F. necrophorum always fatal?

No

What other diseases does F. necrophorum cause in cattle?

• Foot rot

• Respiratory dz in calves