PATHOLOGY - Equine Anaemia Flashcards
How does horse breed influence PCV?
Breeds used as racehorses are going to have a higher PCV compared to breeds used for leisure horses etc
How can exercise and stress affect an equine blood sample?
Exercise and stress cause splenic contraction which will increase the PCV
How can sedation affect an equine blood sample?
Sedation causes splenic relaxation which will decrease the PCV
What should you be aware of when using EDTA tubes to collect blood samples from horses?
In horses, erythrocytes and platelets tend to form rouleaux (aggregates) which can affect haematology results
Which blood tube should you use if you want to carry out an accurate platelet count in horses?
Sodium citrate tube
What are the clinical signs of acute anaemia in horses?
Tachycardia
Tachypnoea
Hyperpnoea
Pale mucous membranes
What are the clinical signs of chronic anaemia in horses?
Exercise intolerance
Pale mucous membranes
Adaptive tachycardia
Weight loss
Haemic murmur
What is a haemic murmur?
A haemic murmur is a heart murmur due to the decreased viscosity associated with anaemia which will result in turbulent blood flow
What are the two main causes of non-regenative anaemia?
Primary bone marrow disease
Secondary failure of erythropoiesis
Where are bone marrow samples taken from in horses for bone marrow evaluation?
Sternum
What is the most common cause of secondary failure of erythropoiesis in horses?
Chronic disease resulting in chronic inflammation
Which laboratory findings can be indicative of anaemia secondary to chronic disease?
Inflammatory leukogram
Increased acute phase proteins
What are the two main forms of regenerative anaemia?
Haemorrhagic anaemia
Haemolytic anaemia
What are the distinguishing features of regenerative anaemia on a horse blood smear?
Mild anisocytosis
Howell-jolly bodies
(T/F) Horses do not have reticulocytes
TRUE.
What are the distinguishing features of regenerative anaemia on horse haematology?
Increased mean corpuscular volume (MCV)
What can be indicated by a high mean corpuscular haemaglobin concentration (MCHC) in horses?
A high mean corpuscular haemaglobin concentration (MCHC) in horses indicates haemolysis because there are increased concentration of free haemoglobin in the blood
What is the normal neutrophil to lymphocyte ratio in horses?
The normal neutrophil to lymphocyte ratio in horses is 2:1
What is the average blood volume in horses?
80 - 100ml/kg (depending on if they are warm or cold blooded, warm is on the higher end)
When will horses begin to show signs of hypovolaemia and shock due to acute blood loss?
Horses will begin to show signs of hypovolaemia and shock following acute blood loss of 20 - 30%
What can you do to determine if an anaemia is regenerative in a horse following acute blood loss?
You can take sequential blood samples to measure the PCV and the total protein and see if there is improvement
How quicky should PCV begin to improve in a regenerative anaemia following acute blood loss?
PCV should improve by 1% every 3 days following blood loss
How quicky should total proteins begin to improve in a regenerative anaemia following acute blood loss?
Albumin should begin to improve in 5 - 10 days post haemorrhage and immunoglobulins should begin to improve in 3 - 4 weeks following blood loss
Which site can be useful for taking sequential blood samples to monitor for regeneration?
Facial venous sinus
What can you do to manage acute haemorrhagic anaemia?
Blood transfusion
What are the two main indicators that a horse requires a blood transfusion?
Tachypnoea
Hyperpnoea
Indicates there is hypoxaemia or hypercapnia
(T/F) Horses have pre-existing alloantibodies
FALSE. Horses do not typically have existing alloantibodies unless they have had a previous transfusion or have been pregnant
What is the significance of horses not typically having alloantibodies?
Because horses do not typically have naturally occurring allo-antibodies, this means that for their first transfusion, it is safe to transfuse any blood type, however you will be required to cross-match any subsequent transfusions as the horse will have developed antibodies against the originally transfused blood type
Why are mares breeds not typically the best blood donors?
Mares may have produced antibodies against the foetal red blood antigens, making them more risky blood donors
What is the ideal signalement for blood donation in horses?
AaCa non-arab gelding
How much blood can horses donate?
Horses can donate 1 litre of blood per 100kg of body weight
Which vessel is used to administer blood products in horses?
Jugular vein
What are four generalised causes of chronic haemorrhage and resulting anaemia in horses?
Gastrointestinal bleeding
Respiratory bleeding
Urinary tract bleeding
Haemostatic disorder
Which further tests could you to investigate for chronic gastrointestinal bleeding?
Gastroscopy
Faecal egg count/parasite screening
Which further tests could you to investigate for chronic respiratory bleeding?
Endoscopy
Sampling and cytology
Which further tests could you to investigate for chronic urinary bleeding?
Urinalysis
Which further tests could you to investigate for chronic bleeding due to a haemostatic disorder?
Platelet count
Buccal mucosal bleeding time (BMBT)
Prothrombin time (PT)
Activated partial thromboplastin time (aPTT)
How can you determine if a chronic haemorrhage has stopped in horses?
Take a blood sample and assess the PCV and total solids (TS)
What is indicated by a low PCV and a low TS?
A low PCV and TS suggests that there is an ongoing chronic haemorrhage
What is indicated by a low PCV but improving TS?
A low PCV but improving TS suggests that the bleeding has stopped however regeneration has been delayed
What is indicated by an improving PCV, TS and an increased MCV?
An improving PCV, TS and an increased MCV suggests the bleeding has stopped and there is regeneration (MCV will increase due to the anisocytosis)
Which laboratory findings can be indicative of anaemia secondary to chronic disease?
Inflammatory leukogram
Increased acute phase proteins
What are the distinguising clinical signs of haemolytic anaemia?
Icterus
Haemaglobinuria
Hepato-splenomegaly
Pyrexia
What is the main cause of haemolytic anaemic in horses?
Immune-mediated haemolytic anaemia (IMHA)
What is the difference between primary immune-mediated haemolytic anaemia (IMHA) and secondary immune-mediated haemolytic anaemia (IMHA)?
Primary IMHA is an autoimmune response against the natural antigens present on the erythrocytes, whereas secondary IMHA is caused by molecular mimicry where infectious or chemical agents trigger autoimmunity by binding to the erythrocytes
What is a common form of primary immune-mediated haemolytic anaemia (IMHA) seen in horses?
Neonatal isoerythrolysis
What is neonatal isoerythrolysis?
In pregnant mares, if the foetus has a different blood type , antibodies will be produced within the mare against the foetal erythrocyte antigens. This can become a problem in subsequent pregnancies if the foals have the same foreign erythrocyte antigens inherited from the stallion because the mare will have high levels of antibodies against the foal’s blood type. These maternal antibodies will be transmitted to the foal in colostrum and cause haemolytic anaemia
What is the typical onset for neonatal isoerythrolysis?
2 to 3 days post parturition
What are the clinical signs of neonatal isoerythrolysis?
Signs of acute anaemia
Weakness
Icterus
How can you treat neonatal isoerythrolysis?
Supportive care
Blood transfusion
Very challenging to treat
What can be done to prevent neonatal isoerythrolysis?
Cross-match the mare and stallion blood types
Prevent the foal from nursing for 24 hours
Use alternate form of colostrum
What are four causes of secondary immune-mediated haemolytic anaemia (IMHA) in horses?
Respiratory tract infections
Streptococcus abscesses
Drug-induced
Neoplasia
How can respiratory tract infections cause secondary immune-mediated haemolytic anaemia (IMHA) in horses?
Viruses such as influenza and herpes virus can release antigens which bind to erythrocytes, inducing an immune reponse against the erythrocytes and haemolysis
How can streptococcus abscesses cause secondary immune-mediated haemolytic anaemia (IMHA) in horses?
Streptococcus can release antigens which bind to erythrocytes, inducing an immune reponse against the erythrocytes and haemolysis
Which three drugs can induce secondary immune-mediated haemolytic anaemia (IMHA) in horses?
Penicillin
Sulphonamides
Acepromazine
How can neoplasia cause secondary immune-mediated haemolytic anaemia (IMHA) in horses?
Tumours can release antigens which bind to erythrocytes, inducing an immune reponse against the erythrocytes and haemolysis
Which neoplasms can cause secondary immune-mediated haemolytic anaemia in horses?
Lymphoma
Fibrosarcoma
Which test is used to diagnose immune-mediated haemolytic anaemia in horses?
Osmotic fragility test
The Coombs test is generally unreliable in horses
How do you treat equine immune mediated haemolytic anaemia (IMHA)?
Stop any drugs that could be inducing haemolysis
Immunosuppressive therapy
Blood transfusion if necessary
Which two drugs can be used for immunosuppressive therapy in horses?
Dexamethasone
Prednisolone
Which infectious agent should you be aware of as a differential diagnosis in anaemic horses?
Piroplasmosis (not currently in the UK unless horse has been imported from an endemic area)
How is piroplasmosis spread from host to host?
Piroplasmosis is spread from host to host via tick vectors with piroplasmosis within their salivary glands
(T/F) Piroplamosis can cross the placenta
TRUE. Piroplasmosis can cross the placenta and thus foals can be born with clinical signs of this parasite
(T/F) Equine piroplasmosis may not be detectable clinically in an infected horse
TRUE.
Which diagnostic tests can be done to diagnose piroplasmosis?
cELISA
PCR
Complement fixation test
Indirect immunoflurescent antibody test
What can be done to prevent importing piroplasmosis into the UK?
Screen all imported horses for piroplasmosis using cELISA and PCR and continue to screen and test ticks for piroplasmosis using PCR
Which drug can be used to treat piroplasmosis?
Imidocarb dipropionate
