It is caused by a tiny parasite (Babesia canis) which is introduced into the body by a tick bite.
The peracute (very sudden and severe) form causes death within a few hours and treatment is of little avail.
If this is 39 °C or higher you should have the dog examined – do not wait until its mucous membranes become pale, white or yellow, which commonly suggests a more advanced stage of the disease.
Yellow faeces and brown or red urine also suggests the presence of biliary fever.
In early cases simple injections are usually sufficient, but in others blood transfusions, electrolyte infusions per vein, liver tonics, blood-building, etc., may be required.