Leucocytozoon spp. (2)

Question 1

How do you identify?

Answer 1

Spherical to ovoid to spindle-shaped masses containing 1-4 elongated, deeply stained structural (gamonts)

Macro/microgametocytes - 18-24 micro m

Organisms in blood or tissues

Question 2

Explain the life cycle

Answer 2

Infected when bitten by Blackflies/biting midges

Enter bloodstream

Sporozoites enter hepatocytes

First generation of Schizonts may develop in brain, heart, lungs, liver, kidney, gizzard, intestine and lymphoid tissue

Schizonts (up to 500 micro m) develop possibly in lymphoid or macrophagic cells

Megaloschizonts develop to Merozoites

Schizonts rupture and Merozoites are released

Form gamonts

Cycle can continue indefinitely

Merozoites enter lymphocytes, monocytes, and erythrocytes forming micro/macrogametocytes

Fertilization occurs in vector

Sporozoites pass to salivary glands - transferred to birds

Question 3

What are the sites of infection?

Answer 3

Brain

Heart

Lung

Kidney

Gizzard

Intestine

Lymphoid tissue

Blood cells

Question 4

Describe the Pathogenesis

Answer 4

Young animals - morbidity/mortality may be high

Mortality in adults usually low

Birds recovering from infections become lifelong carriers of disease

Highly pathogenic for young ducks and geese

Acute infections - young animals

 - Listlessness
 - Anorexia 
 - Anemia
 - Labored breathing
 - CNS symptoms seen before death

Adult birds - infections usually chronic
- Similar situations

Postmortem examination Splenomegaly and hepatomegaly seen

Question 5

How do you diagnose?

Answer 5

Gametocytes in blood smears and organs

Question 6

How do you treat and prevent?

Answer 6

Antiprotozoals remedies - administered via feed

Vaccine available

Repellents effective in decreasing vector bites

Treatment and prevention in free-living wild birds very difficult

Question 7

What are the hosts?

Answer 7

Domestic and wild fowl

Vectors

 - Blackflies
 - Biting midges