Disorders of the Equine Hemolymphatic System III

What is the most common neoplasia of horses?

Lymphoma

Hematopoietic neoplasia arising from lymphoid tissue

Lymphoma

T or F: Lymphoma is a disease of older horses

B

What are the different clinical syndromes of lymphoma based on anatomic distribution?

1. Multicentric

2. Intestinal

3. Mediastinal

4. Cutaneous

How is lymphoma classified?

1. Anatomic location

2. Morphologic

3. Cell lineage

How do we determine the cell lineage of lymphoma?

Immunohistochemical evaluation

What is the most common cell lineage of equine lymphoma?

T cell rich, large B cell lymphoma

What are the most common clinical signs of lymphoma? (6)

1. Weight loss

2. Anorexia

3. Lethargy, depression

4. Edema

5. Recurrent fever

6. Lymphadenopathy

T or F: Peripheral lymphadenopathy is rare in horses

A (you can only feel 1 peripheral LN)

The leukogram varies for lymphoma, which is more common? Lymphopenia or lymphocytosis

Lymphopenia

____________________ can occur from GI loss if there is GI lymphoma

Hypoproteinemia

What are some paraneoplastic syndrome hematologic abnormalities that can be observed?

1. Hypercalcemia

2. IMHA or IMTP

Lymphoma involving multiple LNs and extra-nodal metastasis with nonlymphoid tissue involvement (spleen and liver most common)

Multicentric lymphoma

T or F: Multicentric has a very poor prognosis

A

What are clinical signs of intestinal lymphoma? (5)

1. Malabsorption, protein loss

2. Weight loss

3. Edema

4. Abdominal effusion

5. Colic/diarrhea

What neoplastic lesions can be seen with intestinal lymphoma?

1. Diffuse/segmental thickening

2. Focal masses

3. Scattered ulcerative lesions

What is the most common neoplasia of the equine gastrointestinal tract?

Intestinal lymphoma

How do you diagnose intestinal lymphoma?

1. Ultrasound, rectal biopsy

2. Abdominal fluid analysis (?)

3. +/- glucose absorption test

What is the most common thoracic neoplasia of horses?

Thoracic lymphoma

What are the different types of thoracic lymphoma?

1. Mediastinal

2. Thymic

3. Pulmonary

(B cell or T cell) predominates for thoracic lymphoma in horses

T cell

What are clinical signs of thoracic lymphoma in horses? (5)

1. Nasal discharge

2. Abnormal lung sounds, dyspnea

3. Pleural effusion

4. Ventral thoracic and limb edema

5. Lymphadenopathy

Skin associated lymphoid tissue with lymphoma

Cutaneous lymphoma

T or F: Cutaneous lymphoma can have single to multiple firm, subcutaneous, nonpainful masses

A

Cutaneous lymphoma is predominantly what cell lineage?

T cell rich, large B cell lymphoma

T or F: Cutaneous lymphoma is very aggressive

B

Cutaneous lymphoma is often responsive to what treatments?

Corticosteroids or surgical excision

__________________ may influence the recurrence of cutaneous lymphoma

Hormonal changes (pregnancy)

Antemortem diagnosis of lymphoma is often challenging, what are your diagnostic options? (6)

1. Palpable mass or lymphadenopathy

2. Ultrasound (mass identified)

3. Fluid cytology (pleural or peritoneal)

4. Excisional biopsy or FNA

5. Bone marrow aspirate

6. Flow cytometry (immunophenotyping or serum IgM)

Lymphoma treatment is typically ______________ and not _______________

Palliative, curative

What is involved in lymphoma treatment in horses?

1. Radiation therapy (brachytherapy, linear accelerator)

2. Corticosteroids (alone or with chemotherapy)

3. Chemotherapy (very expensive)

4. Intralesional

What drug is used for intralesional cutaneous lymphoma treatment?

Cisplatin

Leukemia originates from bone marrow

Primary leukemia

Leukemic phase of lymphoma

Secondary leukemia

Leukemia with profound leukocytosis

Leukemic leukemia

Leukemia with blast cells and low/normal WBC

Subleukemic leukemia

Leukemia with abnormal bone marrow only

Aleukemic leukemia

Leukemia has a _____________ prognosis

Grave

What are the most common hematologic changes for equine leukemia?

1. Anemia

2. Thrombocytopenia

3. Increased blast (or atypical) cells in blood

How do you diagnose leukemia?

1. Bone marrow aspirate

2. Flow cytometry (cellular antigens)

3. Immunohistochemistry, immunophenotyping

Plasma cell proliferation in the bone marrow

Primary myeloma

Plasma cell proliferation

Myeloma

Plasma cell proliferation extramedullary - LN, spleen, kidney, liver

Secondary myeloma

Plasma cell proliferation in bone marrow and tissues

Multiple myeloma

What are clinical signs of myeloma in horses? (6)

1. Weight loss

2. Fever

3. Lethargy

4. Pale MM

5. Limb edema

6. Recurrent infection

How do you diagnose myeloma?

1. Bone marrow - plasmacytosis

2. Hematology

What will you see on hematology for myeloma? (5)

1. Anemia

2. Hyperglobulinemia

3. Pancytopenia

4. Hypercalcemia

5. Monoclonal immunoglobulinemia

T or F: Equine myeloma has a poor prognosis and rapid deterioration

A

What is another name for Corynebacterium pseduotuberculosis?

Pigeon fever

What is the etiology of pigeon fever?

Corynebacterium pseudotuberculosis

Pigeon fever is endemic where?

Southwest US

What type of conditions are good for pigeon fever?

Dry and dusty

T or F: Pigeon fever is reportable in all states

B (only certain states)

How is Corynebacterium pseudotuberculosis transmitted?

Mechanical vectors - flies

Corynebacterium pseudotuberculosis bacteria enter via wounds/abrasions in the skin or mucous membranes with the _________________ being predisposed

Ventral midline

What are the three clinical presentations of Pigeon fever?

1. Ulcerative lymphangitis

2. Internal infection

3. External abscesses

Of the clinical presentations of pigeon fever, which require aggressive treatment?

1. Ulcerative lymphangitis

2. Internal infection

What is the least common clinical presentation of pigeon fever?

Ulcerative lymphangitis

What is the most common clinical presentation of pigeon fever?

External abscesses

Clinical presentation of pigeon fever characterized by severe limb swelling, cellulitis and draining tracts

Ulcerative lymphangitis

Ulcerative lymphangitis from pigeon fever most commonly affects (fore or hind) limbs

Hind

Clinical presentation of pigeon fever characterized by infection in the liver, spleen, kidney and lungs

Internal infection

Clinical presentation of pigeon fever characterized by single-multiple well encapsulated abscesses with odor-free tan exudate

External abscesses

How do you diagnose external abscesses for pigeon fever?

Culture of aspirate or exudate

How do you diagnose internal infection for pigeon fever?

1. Clinical signs

2. Diagnostic imaging

3. +/- transcutaneous biopsy/aspirate

4. Synergistic hemolysis inhibition test (SHI)

The synergistic hemolysis inhibition test (used to diagnose internal infection of pigeon fever) should be interpreted in light of ________________

Clinical signs

T or F: You should use a synergistic hemolysis inhibition test (SHI) as a sole diagnostic test for internal infection of pigeon fever

B

How do you treat external abscesses from pigeon fever?

Establish drainage

T or F: Antimicrobial therapy is recommended for external abscesses from pigeon fever

B (may prolong course of disease)

When is antimicrobial therapy recommended for when treating for pigeon fever?

1. Ulcerative lymphangitis

2. Internal abscesses

3. Systemic illness

What antimicrobial drugs can be used to treat for pigeon fever?

1. Rifampin and ceftiofur/penicillin

2. TMS

3. Enrofloxacin

What is included in supportive care for pigeon fever? (5)

1. Hydrotherapy

2. Exercise

3. Drainage

4. Wraps

5. NSAIDs

How do you prevent pigeon fever?

1. Reduce environmental contamination

2. Insect control