Lecture 6: Erythrocytes

Shapes, Inclusions, & Infective Agents

camelid erythrocytes

normal mammalian discocyte (RBC)

(goat blood)

poikilocytes

(deer blood)

drepanocytes

What are drepanocytes?

fusiform or spindle-shaped cells (sickle cells)

avian erythrocytes

What is rouleaux vs agglutination?

R: stacks of RBCs like coins

A: clumps of RBCs

What has occurred to these RBCs?

rouleaux

How does hyperglobulinemia cause rouleaux?

increased concentration of positively charged proteins coat the normally negatively charged RBCs neutralizing their surfaces and allowing them to stack together

What has happened to these RBCs?

agglutination

How would you differentiate rouleaux from agglutination?

saline wash → cells don’t adhere with rouleaux, but continue to adhere in saline with agglutination

Describe the erythrocyte morphology.

normal

Describe the erythrocyte morphology.

anisocytosis (different sizes)

Describe the erythrocyte morphology.

hypochromasia (paler, reduced hemoglobin)

Describe the erythrocyte morphology.

polychromasia anisocytosis (variation in size and prescence of immature RBCs that stain blue)

When would you expect to see hypochromic appearance in RBCs?

iron deficiency anemia (lack of hemoglobin production)

What is poikilocytosis?

general term for the presence of abnormally shaped erythrocytes

What species is poikilocytosis normal?

goats

When would you expect to see echinocytes?

• usually an artifact in pigs

• snake bites

• uremia, post-transufsion, PK deficiency in dogs

• total body depletion of cations (horses)

• RBC dehydration, ATP depletion, increased pH, increased RBC calcium

True or false: crenation (echinocytes) is a reversible shape change.

true

What are acanthocytes?

RBCs with excess cholesterol vs phospholipids which reduces membrane fluidity, giving the cell a spur shape

When would you expect to see acanthocytes?

• liver disease

• hemangiosarcoma, glomerulonephritis, DIC

• normally in young goats, and some cattle

What type of RBC is this?

acanthocytes

What are stomatocytes?

RBCs with a slit in the center

What type of RBC are these?

stomatocytes

Hereditary stomatocytosis with swollen erythrocytes has what effect on the diagnostics?

increased MCV and decreased MCHC

True or false: stomatocytes are most often artifacts in thick blood films.

true

When do spherocytes form?

when a portion of the erythrocyte membrane is bond and removed (erythrocytes can reseal themselves) which no longer allows for the formation of discocytes

True or false: spherocyte volumes are remarkably lower than discocytes because their diameters are consdierably less

false: volumes are only slightly lower

When would you expect to see spherocytes?

• IMHA (immune-mediated hemolytic anemia)

• snake bites and bee stings

• erythrocyte parasites

• dyserythropoiesis in english springers

• zinc toxicity

What deficiency causes spherocyte formation in cattle?

band 3

What is a schistocyte?

fragmented RBC

What type of RBC can be seen on the right?

schistocyte

What erythrocyte changes may be seen in blood smears with fragmentation?

schistocytes, keratocytes, acanthocytes

What is the best evidence for fragmentation?

schistocytes

What could cause erythrocyte fragmentation?

• anemia

• mechanical injury: DIC, caval syndrome (heartworms), cardiac valvular stenosis, glomerulonephritis

• endothelial injury: vasculitis, splenic or hepatic disease, hemangiosarcoma

• thermal injury: heat stroke or severe burns

What types of deficiencies/disorders can cause fragmented erythrocytes?

• severe iron deficiency

• myelofibrosis

• hemophagic histiocytic disorders

• congenital and acquired dyserythropoiesis in dogs

• PK deficiency post-spelectomy in dogs

What are some endogenous oxidants that would cause the formation of eccentrocytes in dogs?

• ketoacidotic diabetes

• inflammation

• neoplasia

What are some exogenous oxidants that would cause the formation of eccentrocytes in dogs?

onions, garlic, NSAIDs, propofol, vitamin K

What causes the formation of eccentrocytes?

membrane oxidant injury

What effect do acetaminophen, onions, garlic, vitamin K, propofol, vitamin K antagonist rodenticides have on dog RBCs?

form eccentrocytes

What enzyme deficiencies can cause horses to develop eccentrocytes?

GR and G6PD (carbohydrate metabolism)

True or false: occasionally, nucleated erythrocytes present in low numbers in healthy dogs and cats.

true

What can cause nucleated erythrocytes?

• regenerative anemias

• lead toxicity

• heat stroke

• marrow injury or disease

• hereditary dyserythropoiesis in dogs and cattle

• cardivascular disorders, inflammation, trauma, or hyperadrenocorticism in dogs

What is your top differential if a dog presents with mild anemia with more nucleated erythrocytes than leukocytes in the blood and basophilic stippling?

lead toxicity

What could cause nucleated erythrocytes and marrow injury, but may not cause anemia?

• septicemia

• endotoxic shock

• drugs

• heat stroke

What are the marrow disease with nonregenerative anemia?

• myelodysplasia

• hematopoietic neoplasms

• infiltrative disorders

What is a Howell-Jolly body?

a nuclear remnant in an RBC

In what species are Howell-Jolly bodies normal?

cats and horses

What is the arrow pointing to?

Howell-Jolly body

When would you expect to see Howell-Jolly bodies?

• regenerative anemias

• splenectomy

• glucocorticoid admin

• vincristine therapy in regenerative anemia, nuclear fragmentation

How can you tell the difference between Howell-Jolly and Heinz bodies?

Howell-Jolly bodies are DNA fragments appearing as small, dark, round dots with Wright's stain, while Heinz bodies are denatured hemoglobin seen as larger, often irregular, purple inclusions requiring a special supravital stain, not routine stains

What diseases cause an increase in Heinz bodies?

diabetes, lymphoma, hyperthyroidism

What are some causes of Heinz bodies in small animals?

• splenectomy in dogs

• propylene glycol in soft-moist cat food

• acetaminophen, methylene blue, methionine

• propofol anesthesia in cats

• skunk musk in dogs

What are some causes of Heinz bodies in large animals?

• kale and other Brassica species in ruminants

• copper toxicity in sheep and goats

• selenium-deficient cattle on St. Augustine grass

• phenothiazine in horses

When do you expect to see basophilic stippling?

• regenerative anemia, primarily in ruminants

• lead toxicity

What are some protozoal infectious agents of erythrocytes?

• Babesia spp.

• Theileria spp.

• Cyauxzoon spp.

What rickettsial organism is an infectious agent of erythrocytes?

Anaplasma spp.

What bacterial organism is an infectious agent of erythrocytes?

Bartonella spp.

What viral organism is an infectious agent of erythrocytes?

distemper

B. bigemina (cattle)

B. gibsoni (dogs)

B. vogeli (dogs)

B. felis (cats)

What infectious agent causes schizogony in lymphocytes?

theileria spp.

T. equi (horses)

T. buffeli (cattle)

What infectious agent causes intermediate schizonts and merozoites?

cytauxzoon felis

What are bacterial organisms that divide within vacuoles inside cells?

rickettsia

A. marginale in a cow

What are hemotropic mycoplasmas?

small bacterial organisms attached to the outside of erythrocytes

M. haemofelis

M. suis

M. ovis

M. haemocanis

M. Wenyoni in cattle

Distemper virus inclusions