Theileria (Cytauxzoon) spp. (2)

Question 1

How do you identify?

Answer 1

Small organisms - 1-2 micro m

In red blood cells

Question 2

Explain the life cycle

Answer 2

Amblyomma americanum transmits organism to cats

Dermacentor variabilis can transmit disease

Schizonts found in leukocytes, erythroblasts, macrophages, and other host cells

Release Merozoites

Merozoites may be absent or present in the circulating blood

Invade erythrocytes

Occurs in reticuloendothelial cells

Question 3

What is the site of infection?

Answer 3

Blood

Question 4

Describe the Pathogenesis

Answer 4

Developing Schizonts cause an enlargement of infected cells to 75 micro m

1 organism per cell, sometimes 4

Occlusion of lumen of blood vessels, sinusoids in organs (heart, liver, and lungs)

Parasitemia 1-4% of RBC

Rapid and fatal disease in south central USA

Die within 9-15 days

Fever

Question 5

What are the clinical signs?

Answer 5

Pyrexia

Anemia

Icterus

Dehydration

Question 6

How do you diagnose?

Answer 6

Wright’s or Giemsa - stained blood smears

1-2 micro m organisms with light blue cytoplasm and dark red nucleus in erythrocytes

Question 7

How do you treat and prevent?

Answer 7

No satisfactory treatment

Antiprotozoals - varying results

 - Diminazone aceturate
        - 2 mg/kg, IM, 2 consecutive days 
        - 5/6 successfully treated
 - Imidocarb diproprionate 
        - 2 mg/kg, IM, 2 consecutive days
        - One cat

Supportive therapy

 - Isotonic IV for dehydration
 - Heparin SQ for disseminated intravascular coagulation

Tick control

Question 8

What are the hosts?

Answer 8

Cats

Bobcats