Page 1094 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1069

VetBooks.ir may play a part in an individual horse’s susceptibil- and results in profound neurological signs due to
Septic meningitis is the most common form
ity to infection. With respect to neurological disease,
the classic histopathological findings include multi-
roots of the brain and spinal cord. As the condition
focal microabscessation in the brainstem, medulla involvement of the superficial parenchyma and nerve
and pons, a similar distribution to CNS listeriosis progresses, secondary CNS oedema and obstructive
reported in ruminants. Most antimicrobials that are hydrocephalus may lead to a worsening of clinical
routinely used in horses, with the exception of ceftio- signs. One complication of temporohyoid osteopa-
fur, should be effective against L. monocytogenes. thy (THO) is the migration of bacteria (usually
upper respiratory tract commensals) to the CNS
BACTERIAL via fractures of the petrous portion of the temporal
MENINGOENCEPHALOMYELITIS bone. Similarly, horses with suspected basilar skull
fractures are also at risk of bacterial translocation
Definition/overview to the CNS. For these reasons, it is recommended
Bacterial meningitis is a highly fatal disease that is that horses with acute-onset suspected THO or sus-
rare in adult horses, but more common in neonatal pected skull fractures receive broad-spectrum anti-
foals. microbial therapy.

Aetiology/pathophysiology Clinical presentation
Meningitis in the horse is usually bacterial in origin In neonates, the initial clinical signs, such as aim-
and commonly occurs in one of three ways: (1) hae- less wandering, depression, loss of affinity for the
matogenous spread from other sites; (2) direct exten- dam and abnormal vocalisation, are not specific for
sion of a suppurative process in close proximity to the meningitis, although they do indicate neurologi-
calvarium; and (3) secondary to penetrating wounds or cal disease (Figs. 10.23, 10.24). These signs are
fractures of the calvarium. Infections of the CNS in
neonates are usually associated with the agents causing
generalised sepsis, and therefore gram-negative organ- 10.24
isms predominate: Escherichia coli, Actinobacillus equuli
and Klebsiella species. In older animals, gram-positive
organisms are predominant, such as Staphylococcus spp.
and haemolytic Streptococcus spp., and rarely Rhodococcus
equi. Salmonella is infrequently associated with menin-
gitis, as a sequela to enterocolitis.

10.23

Fig. 10.24 Seizure
activity and head
pressing in a foal
Fig. 10.23 A foal with meningitis wandering aimlessly. with meningitis.