Page 1131 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1106 CHAPTER 10

VetBooks.ir Diagnosis Solanaceous plants
Members of the family Solanaceae contain either the
Diagnosis is usually based on clinical signs and a
history of chronic exposure to the toxic plant. The
pasture should be evaluated, as should multiple bales tropane (atropine-like) or solanum groups of alka-
loids and cause signs of neurotoxicity when ingested
of hay. MRI has been successfully used for ante- by horses. Datura spp. (thornapple, jimsonweed),
mortem diagnosis, but is not always readily available. Atropa belladonna (deadly nightshade) and Dubosia spp.
Focal necrosis and malacia of the globus pallidus (corkwoods) contain the tropone alkaloids. These
and/or the substantia nigra are characteristic lesions plants are widely distributed but are unpalatable
of this disease and are usually seen bilaterally. to horses. Poisoning may occur when these plants
are included in hay or grain. Associated signs are
Management anorexia, depression, excessive urination and thirst,
There is no specific treatment for the disease other diarrhoea, mydriasis, muscle spasms and convul-
than supportive care. Horses should be removed sions. Physostigmine or neostigmine (a short-acting
from the pasture if this is the suspected source. cholinesterase) (1–5 mg s/c q1–4 h) is the treatment of
Otherwise, the hay source should be changed. choice and should be used to effect. Solanum nigram
(black nightshade) is the most toxic of the solanum
Prognosis alkaloid-containing plants. Colic, ataxia, weakness,
Complete recovery is not seen. tremors and convulsions are associated with black
nightshade poisoning. Solanum tuberosum (common
OTHER PLANT POISONINGS potato) may also be toxic when green.

Bracken fern and horsetail poisoning Toxic alcohols
Ingestion of either Pteridium (bracken fern) or Umbelliferous plants (hemlock-type) contain higher
Equisetum (horsetail) species causes neurological alcohols, including enanthotoxin and cicutoxin, and
disease in horses. These plants are not usually eaten are amongst the most poisonous plants known. The
by horses, but can be ingested in times of shortage toxins are concentrated in the root and stem and
of more palatable forage or if the plants have been these plants are found throughout the USA and in
incorporated into hay. These plants contain a thi- many other countries, especially in Europe, growing
aminase that, after repeated exposure, causes thia- in wet or swampy areas. Signs of poisoning include
mine deficiency. Clinical signs occur weeks after salivation, mydriasis, colic, delirium and convulsions.
ingestion begins and may continue after removal of
the source. Anorexia, bradycardia and ataxia are fre- MISCELLANEOUS NEUROLOGICAL
quently seen, while signs of forebrain disease, such CONDITIONS
as blindness and head pressing, are more infrequent.
Ataxia may be severe and involve all four limbs. CEREBRAL ABSCESS
Thiamine administration (0.5–1 g p/o q12 h) results
in a rapid resolution of clinical signs. Definition/overview
Intracranial abscesses are rare and sporadic in horses.
Grove poisoning
Grove poisoning occurs in areas of southern Florida Aetiology/pathophysiology
with intensive horticultural activity and has been asso- Intracranial abscesses may develop secondary to bac-
ciated with plants of the Indigofera genus. The clinical terial infection elsewhere in the body or via extension
syndrome seen indicates diffuse cerebral, vestibu- of local disease processes such as sinusitis, rhinitis,
locerebellar and spinal cord disease; however, there otitis media, tooth root abscesses and periocular
has been no consistent neuropathological lesion. The lesions (Fig. 10.59). Similar to bacterial meningi-
signs may fluctuate in severity, but are progressive tis, the likely aetiological agents relate to common
over time and poisoning usually results in death. causes of septicaemia, or may be organisms known