equis - Articles
Anemia: overview
Introduction
- The life-span of equine erythrocytes is about 100 days.
- Anemia is defined as a deficiency of erythrocytes either in number or volume or both.
- Cause:
- Hemorrhage: internal vs external, acute vs chronic.
- Hemolysis: intravascular vs extravascular, immune-mediated (primary or secondary), direct toxic damage, oxidative damage, infectious disease.
- Increased use/shortened half-life of RBCs.
- Decreased production.
- Signs: depends on the degree of chronicity of the anemia. Common features include pallor or jaundice, lethargy, weakness, collapse, poor performance/exercise intolerance.
- Diagnosis: hematological evaluation, including a blood smear, is essential for the identification of anemia.
- Treatment: depends on the cause of the anemia.
- Prognosis: depends on the cause of the anemia.
Presenting signs
- Poor performance/lethargy/slow post-exercise recovery.
- History of deficient deworming, drug administration, trauma, etc.
- History of travel abroad.
- History of chronic illness.
- Depression.
- Weakness.
- Red urine.
- Icterus.
- Weight loss.
- Chronic blood loss, eg via gastrointestinal ulceration Stomach: gastric ulceration .
- Pale mucous membranes.
- Petechiation.
Acute presentation
- Indication of blood loss, internal bleeding, eg into abdomen/chest, or external bleeding, eg guttural pouch mycosis, or following a surgical procedure.
- Pale mucous membranes.
- Lethargy.
- Tachycardia/tachypnea.
- Collapse.
Geographic incidence
- Areas in which babesiosis Babesiosis , ehrlichiosis Anaplasmosis and trypanosomiasis is endemic.
- Areas in which equine infectious anemia Equine infectious anemia (EIA) is endemic.
- Areas in which deworming is deficient.
Age predisposition
- Neonatal isoerythrolysis Immunology: neonatal isoerythrolysis in newborn foals - 3-5 days old.
- Iron deficiency in foals.
- Intestinal parasitism up to 2-3 years.
- Myelophthisic anemias in horses with a mean age of 10 years.
Cost considerations
- Treatment and investigation can be very expensive.
- Weight loss in populations of young horses due to intestinal parasitism.
Special risks
- Anemia increases the risks associated with anesthesia.
Pathogenesis
Etiology
- Hemorrhage: external or internal blood loss.
- Hemolysis: destruction of red blood cells:
- Immune-mediated (primary or secondary).
- Toxic: direct, eg following DMSO administration, or oxidative damage, eg red maple leaf or onion ingestion.
- Infectious disease, eg equine infectious anemia, babesiosis, ehrlichia.
- Anemia of chronic disease: increased use and shortened red blood cell lifespan.
- Failure of production: myelophthisic disease, eg bone marrow neoplasia, renal disease resulting in reduced production of erythropoietin.
Predisposing factors
General- Hemorrhage.
- Blood loss due to:
- Internal or external parasitism.
- Gastrointestinal ulceration Stomach: gastric ulceration .
- Gastric squamous cell carcinoma.
- NSAID-toxicosis Toxicity: non-steroidal anti-inflammatory (NSAID) .
- Ethmoidal hematoma Ethmoid: hematoma - can produces mild anemia.
- Guttural pouch mycosis Guttural pouch: mycosis ; peracute arterial bleeding.
- Disseminated intravascular coagulopathy (DIC) Disseminated intravascular coagulation /hemorrhagic diathesis.
- Exercise-induced pulmonary hemorrhage Lung: EIPH (exercise-induced pulmonary hemorrhage) .
- Trauma.
- Surgical procedures, eg castration Testis: castration - overview .
- Hemolysis:
- Exposure to drugs, eg DMSO Dimethyl sulfoxide , penicillin Penicillin G , TMPS, phenothiazine, phenylbutazone Phenylbutazone .
- Exposure to toxins, eg red maple leaf, onions, arsenic.
- Infection, eg EIA Equine infectious anemia (EIA) , babesiosis Babesiosis , ehrlichiosis Potomac Horse Fever .
- Chronic disease.
- Renal disease Kidney: disease - overview .
- Neoplasia.
Pathophysiology
- Anemia can be induced via several mechanisms.
- Hemorrhage: external or internal blood loss.
- Hemolysis: destruction of red blood cells:
- Immune-mediated (primary or secondary).
- Toxic: direct, eg following DMSO adminitration, or oxidative, eg red maple leaf or onion ingestion.
- Infectious disease, eg equine infectious anemia Equine infectious anemia (EIA) , babesiosis Babesiosis , ehrlichiosis Potomac Horse Fever
- Anemia of chronic disease: increased use and shortened red blood cell lifespan.
- Failure of production: myelophthisic disease, eg bone marrow neoplasia, renal disease resulting in reduced production of erythropoietin.
- Some diseases induce anemia by more than one mechanism, eg EIA, causes both hemolysis and reduced red cell production.
- Lymphosarcoma might induce anemia both via myelophthisis and via immune-mediated mechanisms.
Timecourse
- Anemia in case of equine infectious anemia Equine infectious anemia (EIA) is progressive and cyclic.
- Anemia following (severe) blood loss Anemia: blood loss /trauma is seen suddenly - not always external bleeding.
- Rapid onset anemia:
- Blood loss Anemia: blood loss .
- Hemolysis.
- Slow onset anemia:
- Bone marrow suppression.
- Parasitism.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Hollis A R & Corley K T T (2011) Initial experience of ultrapurified bovine haemoglobin use in horses. Equine Vet Educ 23 (11), 562-568 VetMedResource.
- Hart K A (2008) Evaluation and management of anaemia in the post operative colic patient. Equine Vet Educ 20 (8), 427-432 VetMedResource.
- Piercy R J, Swardson C J & Hinchcliff K W (1998) Erythroid hypoplasia and anemia following administration of recombinant human erythropoietin to two horses. JAVMA 212, 244-247 PubMed.
- McConnico R S, Roberts M C & Tompkins M (1992) Penicillin-induced immune-mediated hemolytic anemia in a horse. JAVMA 201, 1402-1403 PubMed.
- Mair TS, Taylor F G & Hillyer M H (1990) Autoimmune haemolytic anaemia in eight horses. Vet Rec 126, 51-53 PubMed.