American Hepatozoonosis (Polysystemic Infectious Diseases)

Question 1

What agent causes classic hepatozoonosis?

Answer 1

Coccidian Hepatozoon canis

• An Old World disease
• Mild signs, leukocytosis (may look like leukemia)

Question 2

What agent causes American hepatozoonosis?

Answer 2

Coccidian Hepatozoon americanum

Question 3

How is American hepatozoonosis transmitted?

Answer 3

• INGESTION of ticks (because it’s a coccidian)
• Ingestion of oocysts
  
  • Oocysts > sporocyts > intestine > lymphatics > muscle
  • Intense local inflammation
• Merozoites (lymphatics)
• Tick bites (lympatics)

Question 4

What type of tick transmits American hepatozoonosis?

Answer 4

Amblyomma maculatum (Gulf Coast Tick)

Question 5

Where (geographically) is American hepatozoonosis commonly seen?

Answer 5

Rural southeast US (we get it here from travelers)

Question 6

What are the clinical signs in a patient with American hepatozoonosis?

Answer 6

• Fever, lethargy
• Stiff gait
• Reluctance to walk (severe polymyositis)
• Will not walk to food
• Muscle waste (masticatory muscles go first)
• Ocular discharge

Question 7

What does the lab work look like in a patient with hepatozoonosis (American)?

Answer 7

• Leukocytosis (may be severe)
• Artifactual hypoglycemia
  
  • Leukocytes eat glucose before getting to lab (can get blood with fluoride)
• Increased ALP

Question 8

How do you diagnose a patient with suspected hepatozoonosis (American)?

Answer 8

• Meronts in muscle biopsy (most consistently reliable method)
  
  • ​Problem: polymyositis
• Gamonts in blood smear
• Neutrophilia + periosteal proliferation of long bones (radiographs)
• Real time PCR (takes time)
• Serology (ELISA no longer available)

Question 9

What is the treatment for a dog with hepatozoonosis (American)?

Answer 9

DIFFICULT TO KILL ORGANISMS; NEVER CLEARS ALL

• Supportive:
  
  • NSAIDs
  • Nutritional support
  • Hydration
• Antiprotozoal:
  
  • Triple combination therapy (2 weeks)
    
    • Clindamycin, SMT & TMP, pyrimethamine
  • Ponazuril (2 weeks)
    
    • Acute phase
    • Have to change to chronic therapy to prevent relapsing (2 years)
  • Chronic therapy (2 years)
    
    • Decoquinate mixed in food BID
      
      • Quinolone anticoccidial