Other infectious causes of hemolytic anemia in cats

Question 1

What is the epidemiology of Cytauxzoon felis

Answer 1

Cytauxzoon felis have been traditionally documented in cats living in parts of south-central and eastern USA where Bobcats (considered the reservoir host) and the tick vectors (Amblyomma americanum and Dermacentor variabilis) are endemic

Question 2

What is the pathogeny of Cytauxzoon felis

Answer 2

Within the host, the organism exists as two distinct forms:
- the schizont
- the merozoite

Schizonts injected into the host from the vector initially invade and multiply in mononuclear phagocytes, spreading throughout the body

Merozoites are then released and invade RBCs causing hemolysis and anemia

The schizogenous phase causes microthrombic disease in various organs (particularly the lungs)

Question 3

What are the clinical signs of Cytauxzoonosis

Answer 3

Cytauxzoonosis is very frequently fatal (over 90% mortality reported)

Signs include:
- acute lethargy
- depression
- fever

Neurological signs can occur (e.g., ataxia, seizures, nystagmus) and cats are typically jaundiced with hepatosplenomegaly and widespread lymphadenopathy

Question 4

What are the major laboratory signs for cytauxzoonosis

Answer 4

Hematology often reveals thrombocytopenia and leukopenia

Hemolytic anemia typically develops at day 7-14 post presentation

Hyperbilirubinemia (with relatively mild elevations in liver enzymes) are hallmarks of pre-hepatic jaundice and are typically seen

Question 5

How can a diagnosis of cytauxzoonosis be made

Answer 5

Diagnosis is via cytology of liver, spleen, lung, lymph node aspirates, or examination of peripheral blood smears where schizonts may be observed in phagocytes

Parasites may also be observed in RBCs as dark-staining dots

Some US laboratories offer PCR testing

Question 6

What is the treatment for cytauxzoonosis

Answer 6

Treatment is centered on supportive care:
- IV fluids
- blood ttransfusion

And anticoagulation
- heparin 100-300 UI/kg, SC, q8h

Studies have shown that a combination of atovaquone (15 mg/kg, PO, q8h) and azithromycin (10 mg/kg, PO, q24h) have shown superior efficacy than imidocarb dipropionate treatment (3.5 mg/kg, IM, once every 14 days)

Question 7

What is the prognosis of cytauxzoonosis

Answer 7

If the cat survives past day 7, then it has a good chance of recovery

Question 8

Is Babesia of major concern in cats such as in dogs

Answer 8

Feline babesiosis appears to be a veterinary concern only in south africa

Feline babesiosis has been poorly characterized in the cat so information regarding epidemiology or treatment are lacking

Question 9

Could FeLV be associated with regenerative anemia in cats

Answer 9

Although most anemia associated with persistently FeLV-infected cats is non-regenerative, approximately 10-20 % of the anemia associated with this infection are characterized by a regenerative response

This may be due to true immune-mediated disease or in association with concurrent hemotropic Mycoplasma infection