Page 1052 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

H aemolymphatic system 1027

VetBooks.ir 9.29 9.30

Fig. 9.29 Blood smear from a horse with equine Fig. 9.30 Peritoneal fluid from a horse with
anaplasmosis. The arrows indicate the infectious equine anaplasmosis. The arrow indicates a morula
agent, Anaplasma phagocytophilum, present in a of Anaplasma phagocytophilum in a neutrophil
neutrophil (Wright’s stain). (Wright’s stain).

organisms causing similar haematological abnor- Supportive care is important. Ataxic horses should
malities, such as Theileria equi and EIAV, need to be be restricted to a stall where the risk of injury is less-
considered. ened. NSAIDs (e.g. flunixin meglumine 1.1 mg/kg i/v
q12 h) can be useful in pyrexic horses. Intravenous
Diagnosis administration of a balanced electrolyte solution may
Physical examination findings are non-specific. be useful in dehydrated and anorexic horses. Horses
Anaplasmosis should be considered in geographi- with limb oedema should be walked frequently if
cal areas where it has been recognised and during ataxia is not present. Cold hosing of affected limbs
the appropriate season for tick-borne disease. and application of limb bandages can be helpful. Tick
Leucopenia and thrombocytopenia are often pres- repellents should be used when horses are to enter
ent on a CBC. Hyperbilirubinaemia is common. Ixodes-infested areas. Horses should be inspected for
Anaemia is usually not present. Diagnosis can be ticks after return from infested areas.
made by observing characteristic rickettsial morulae
within granulocytes on a blood smear or peritoneal Prognosis
fluid smear (Figs. 9.29, 9.30). Morulae are always Most animals recover completely, with clinical
visible in the middle of the febrile period, where they signs often improving within a few days of insti-
may be found in 20–75% of neutrophils. Serological tuting appropriate therapy. Without treatment the
confirmation can be made by observing a fourfold infection is self-limiting and should resolve within
rise in antibody titre, but seroconversion may take 2–3 weeks. The main problem is development of
several weeks. Molecular assays are available and are complications such as injury from severe ataxia.
quite specific.
PURPURA HAEMORRHAGICA
Management
Oxytetracycline (7 mg/kg i/v q24 h for 5–7 days) Definition/overview
is most commonly used. Doxycycline (7 mg/kg i/v Equine purpura haemorrhagica (EPH) is a poten-
q24 h for 3–7 days) may also be used. Response tially serious sequela to recent respiratory infec-
to treatment is usually prompt and improvement tion and is observed most frequently following
may be noted in 12–24 hours. Relapse is uncom- Streptococcus equi infection (strangles). The reason
mon but has been reported within 30 days of EPH develops following such infections is uncer-
treatment. tain, but an allergic reaction is suspected.