Page 1122 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1097

VetBooks.ir Table 10.8 Dynamic tests to aid in the detection of a suspected botulism case

TONGUE STRESS TEST
• Keep jaws closed with one hand over the bridge of the nose
• Retract the tongue from the mouth, between the commissure of the lips
• Gently release the tongue
• If the horse allows the tongue to hang for more than 2–3 seconds, this is abnormal and indicates a reduced tongue tone due to
cranial nerve or neuromuscular dysfunction

MUSCLE WEAKNESS
Botulism causes weakness not ataxia and, therefore, a neurological examination may help to establish whether there are conscious
proprioceptive deficits, or whether clinical signs relate exclusively to muscle weakness. The limb-holding test (holding one
forelimb and watching the contralateral limb for muscle fasciculations and buckling) may exacerbate mild muscle weakness

Currently, there is no licensed specific or multiva- sulphonamides. Some antimicrobials, such as pro-
lent antiserum for equine patients in Europe but it is caine penicillin and aminoglycosides, may inhibit
available in the USA and some other countries. release of acetylcholine from pre-synaptic nerve
membranes, resulting in neuromuscular weak-
Nursing care ness. Their use in botulism cases should be avoided
An important aspect of botulism treatment is the because the neuromuscular weakness induced by
provision of excellent nursing care. Patients may these antimicrobials may be potentiated by BoNT
require enteral or intravenous isotonic fluids to and can have catastrophic consequences, such as
maintain euhydration. Care should be taken to avoid respiratory arrest in otherwise stable patients.
overwhelming the GI tract with enteral fluids in
botulism cases that may have poor intestinal motility. Prognosis
Since patients tend to be dysphagic, adequate nutri- In general, the greater the amount of BoNT pres-
tional intake should be provided by enteral feeding ent, the more rapidly progressive the clinical signs,
via an indwelling nasogastric feeding tube or via and the poorer the prognosis for recovery. Adult
parenteral intravenous nutrition. Recumbent horses horses that are recumbent and unable to rise carry a
should be turned frequently and provided with deep grave prognosis. Dysphagic horses gradually regain
bedding to avoid the development of decubital ulcers their ability to swallow over 3–14 days. Return of full
and hypostatic congestion of the lungs. The use strength may take months.
of slings and hoists for recumbent patients may be
considered. Medication to prevent gastric ulceration Prevention
may also be warranted. There are no vaccines licensed in Europe for the
prevention of botulism in horses, but some vaccine
Antimicrobials products are available elsewhere, such as the USA. In
These may be used to treat cases of wound botu- such countries, vaccination of high-risk mares with
lism where the organism proliferates and produces the type B toxoid has reduced the incidence of neona-
BoNT in vivo, but will have no direct therapeutic tal botulism. Good husbandry measures may reduce
benefit in patients who have ingested pre-formed the risk of exposure to BoNT. First, forage should be
BoNT (adult botulism). In patients with second- inspected for spoilage and animal carcasses. Second,
ary complications, such as aspiration pneumonia, large round hay or haylage bales should be properly
broad-spectrum antimicrobial therapy should be processed, stored and inspected prior to feeding.
provided and appropriate classes of antimicrobials Additionally, strict control of rodents and birds may
for this role include cephalosporins and potentiated reduce carcass contamination of forage.