Hepatozoon spp. (1)

Question 1

How do you identify?

Answer 1

Gamonts in blood cells of peripheral blood

Leukocyte contains parasites

Question 2

Explain the life cycle

Answer 2

Ingesting tick, sporozoites released
- Transported to target tissues and organs (including skeletal and
cardiac muscle)

Schizonts are formed

Parasitic organisms found in white blood cells

Ticks become infected by ingesting a blood meal that contains white blood cells that harbor gamonts

Sexual replication in gut of tick

Production of Oocysts containing infective sporozoites

Transmission of H. americanum via ingestion of cystozoites in muscle
- Predation as a means of natural transmission

Question 3

What are the sites of infection?

Answer 3

Schizonts - in various tissues

Gamonts - circulating white blood cells

Question 4

Describe the Pathogenesis

Answer 4

H. canis causes subclinical infection

H. americanum cause severe disease

 - Marked neutrophilic leukocytosis
 - Joint pain
 - Myositis
 - Periosteal bone proliferation - revealed by radiographs 
        - Lesions occur in proximal long bones
               - Similar to hypertrophic osteopathy

Question 5

How do you diagnose?

Answer 5

Examination of muscle tissue at biopsy or necropsy

Gamonts in peripheral blood

Examination of muscle tissue to reveal Schizonts

Large cystic form of H. americanum occurs in skeletal muscle and muscle biopsy very useful

Question 6

How do you treat and prevent?

Answer 6

No satisfactory treatment

Antiprotozoals - failed to prevent relapse

Tick control

Question 7

What are the hosts?

Answer 7

Dogs

Vector is:

 - Amblyomma maculatum (Gulf Coast Tick)
 - Rhipicephalus sanguineus