EQUINE VETERINARY EDUCATION / AE / APRIL 2018


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a)


(Vandenabeele et al. 2004). The prognosis following treatment for pemphigus foliaceus in horses is guarded, and the response varies (White 2009). Many horses require lifelong administration of medication to control the clinical signs, others may be gradually weaned from medication without further relapse (White 2009).


Nervous system


The use of glucocorticoids for conditions involving the central nervous system is controversial. There is a lack of evidence for benefits of glucocorticoid use in large animals, and recommendations have been extrapolated from humans and small animals. The use of these drugs is based on the fact that they are thought to stabilise microvasculature permeability, reduce oedema formation, reduce intracranial pressure and decrease oxygen-derived free radicals (Dowling 2004).


b)


Infectious conditions The use of glucocorticoids to treat cases of equine encephalitis (eastern, western, Venezuelan, equine herpesvirus 1 and West Nile virus) and equine protozoal myeloencephalitis (EPM) remains controversial, since all of these conditions are caused by infectious organisms (Long 2014). In immunosuppressed horses, there is a concern about recrudescence of infection and clinical relapse with the use of glucocorticoids in these conditions (Dirikolu et al. 2013; MacKay 2015). However, in addition to the supportive care, treatment of inflammation associated with these diseases is described using dexamethasone at a suggested doses of 0.05–0.1 mg/kg bwt administered i.v. or i.m. once or twice daily for 1–3 days (MacKay 2015). For cases of EPM, the available literature recommends that use of glucocorticoids should be reserved for horses that exhibit signs of brain involvement or recumbency; and dexamethasone at a dose of 0.1 mg/kg bwt i.v., once or twice daily for the first several days has been described (Howe et al. 2014; Reed et al. 2016). It has been also suggested to restrict the use of glucocorticoids to 1–3 days of treatment with dexamethasone at 0.05 mg/kg bwt every 12 h only in horses severely affected by EPM (Dirikolu et al. 2013). However, there is no scientific evidence demonstrating any positive effect after the use of systemic glucocorticoids for treatment of EPM. Long-term glucocorticoid treatment should be avoided due to the effects upon immune clearance of the causative agent (Dubey et al. 2015). The use of glucocorticoids in horses with bacterial


Fig 3: Lesions characteristic of purpura hemorrhagica in horses, showing haemorrhage in the muzzle region (a), and lesions on the limbs with vasculitis, necrosis and exudate (b, photography courtesy Dr Sarah Ujvari).


meningitis is controversial, with diverse results among studies in species other than horses. One human study showed that there is a benefit in survival rate in adults affected with bacterial meningitis with the use of dexamethasone in the acute phase of the disease (Fritz et al. 2012). However, a clinical trial in 2029 human patients with bacterial meningitis showed no significant reduction in death or neurological disability between dexamethasone and placebo treated groups (van de Beek et al. 2010). In a retrospective study of 28 horses with meningitis and meningoencephalomyelitis, treatment with a single dose of dexamethasone (dose not recorded) was reported for five of the horses. No significant difference in outcome was found with this therapy; however, the small sample size was a limitation in the study (Toth et al. 2012).


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