Page 1099 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1074 CHAPTER 10

VetBooks.ir VERMINOUS Prognosis
MENINGOENCEPHALOMYELITIS
In the vast majority of cases the prognosis is guarded
Definition/overview to hopeless. In animals that do not become recum-
bent and only display mild abnormalities, the prog-
Verminous meningoencephalomyelitis is a rare and nosis is fair to good.
sporadic disorder caused by the aberrant migration of
parasites through the CNS. It is an important differ- EQUINE EHRLICHIOSIS
ential diagnosis to consider as a cause of asymmetrical
neurological disease in horses outside the USA. Horses infected with the tick-borne pathogen
Anaplasma phagocytophila (formerly Ehrlichia equi)
Aetiology/pathophysiology often have transient truncal and limb ataxia. These
Several parasites have been reported including animals may also display weakness. The weakness
Strongylus, Hypoderma, Habronema, Draschia, Halic- and ataxia seen can be severe and these animals may
ephalobus gingivalis and Setaria species. Transmission fall and sustain serious injuries. Inflammatory vas-
of Halicephalobus gingivalis from mare to foal has been cular or interstitial lesions have been reported in the
reported. Strongylus vulgaris thromboarteritis may brains of affected animals, and histologically there
rarely lead to embolic showering of the cerebrum. is inflammation of small arteries and veins, primar-
ily in the subcutis, fascia, nerves of the limbs and
Clinical presentation reproductive organs. Treatment with oxytetracy-
The spectrum of clinical signs is variable and depends cline (6.6–7.5 mg/kg i/v q12–24 h for 3–7 days) often
on the area of the CNS that is involved. Diffuse, results in rapid improvement.
focal or multifocal disease may be evident. Cerebral,
cerebellar, brainstem or spinal cord signs may be TETANUS
observed. In the case of Halicephalobus spp., the lesions
are usually intracranial and result in acute-onset, rap- Definition/overview
idly progressing cerebral signs such as head-pressing, Tetanus is a distressing and highly fatal infectious
loss of proprioception, recumbency, coma and death. disease caused by exotoxins produced by Clostridium
One horse infected with Halicephalobus spp. showed tetani. The disease is characterised by muscular
cauda equina clinical signs, and had parasitic granulo- rigidity and hyperaesthesia in horses of all ages.
mata in the sacral spinal nerve roots. Although the causative agent is relatively ubiquitous,
disease is uncommon in developed countries because
Diagnosis of widespread vaccination, but is common in areas
Diagnosis is usually based on clinical signs and post- where vaccination is less widely used.
mortem findings. CSF changes are not specific or
consistent, with some haemorrhage and increased Aetiology/pathophysiology
numbers of inflammatory cells, such as eosinophils C. tetani is a gram-positive, spore-forming, rod-
and neutrophils, to be expected. CSF eosinophilia shaped anaerobic bacterium that is found in animals,
suggests the possibility of parasitic disease, but birds, soil and organic matter. The spores of C. tetani
is neither highly sensitive nor highly specific. are ubiquitous in the environment and resistant to
Uncommonly, larvae may be evident in the CSF. degradation.
Peripheral eosinophilia is uncommon. An anaerobic environment must be present for
infection to occur in the horse. Although deep punc-
Management ture wounds or subsolar foot abscesses are most lia-
Therapy may include the use of anthelmintics ble to create a suitable anaerobic environment, other
( fenbendazole, 50 mg/kg p/o q24 h for 3 days) and sites of entry include superficial wounds, surgical
anti-inflammatories (flunixin meglumine, vitamin E incisions, the umbilicus in foals and the post- foaling
and/or dexamethasone). reproductive tract in mares. The initial wound that