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Emergency

Piroplasmosis

Piroplasmosis

Piroplasmosis Serum (clotted) or EDTA (smear)
OPYRIGHT 2019 LIPHOOK EQUINE HOSPITAL
Infection with Theileria equi and/or Babesia caballi is referred to as piroplasmosis. These are
protozoan parasites that reside within erythrocytes. Both parasites can coexist in the same horse.
Infection is present in France, Sweden, Spain, central and South America, the Middle East, Asia and
Africa. Following infection horses tend to carry the intraerythrocytic parasites for years and perhaps
for life. Cases are sometimes encountered in horses in UK following importation of previously
infected horses but transmission within the UK is thus far unrecognised.
CLINICAL SIGNS
T. equi infection is generally more severe than B caballi. Piroplasmosis is a cause of a haemolytic
anaemia in any age of foal or adult horses, mainly in the summer/autumn associated with tick
activity.

  • Pyrexia
  • Lethargy, anorexia, dullness, weakness
  • Tachycardia, tachypnoea
  • Pale/jaundiced/petechiated membranes
  • Systolic heart murmur associated with anaemia
  • (haemoglobinuria/bilirubinuria)
  • (Mild colic/diarrhoea)
  • (Oedema)
    DIAGNOSIS
    Haematology
  • Decreased PCV, RBC and Hb concentrations is typical.
  • Haemolysis may lead to increased MCH (Hb/RBC) and MCHC (Hb/PCV) due to anaemia with
    free haemoglobin
  • Increased MCV is often seen as part of a regenerative response.
  • Thrombocytopaenia common
  • White cell numbers are variable (high, low or normal)
    Microscopy
    Blood smears from acute clinical cases should be stained with Romanowsy stains such as Diff-Quick,
    Giemsa or Wrights. This may demonstrate intra-erythrocytic parasites although failure to identify

infection is not uncommon unless great care and time is taken. Identification of parasites in non-
clinical carrier animals is unlikely. With T equi, typically only 1-5% of red cells will be affected. Oval

trophozoites or 4 x pyriform merozoites (“maltese cross”) may be seen. Massive parasitaemias may
be seen in neonatal cases (eg 50% of red cells). With B caballi oval trophozoites or paired pear-shaped
merozoites may be seen although often <0.1% of red cells are parasitized.
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Biochemistry

  • High serum fibrinogen and SAA reflect the infection and inflammatory response.
  • High serum bilirubin (>100 umol/L) is common.
  • Mild increases in liver and muscle enzymes and urea and creatinine may reflect
    hypoxaemia/dehydration

Serology

  • The most reliable serologic tests are the Indirect Fluorescent Antibody Test (IFAT) assay and
    ELISA
  • The Complement Fixation test (CFT) is not very sensitive and should probably not be used
    PCR
  • May be used in both clinical cases and carriers to identify the presence of parasites.