Page 1095 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1070 CHAPTER 10

VetBooks.ir typical of those seen in hypoxic–ischaemic enceph- Prognosis
The prognosis for bacterial meningitis is poor. Even
alopathy in young foals and can cause misdiagnosis
in the early stages. Sometimes, fever of unknown
bacterial meningitis die despite appropriate treat-
origin is the first abnormality that is detected. As with aggressive supportive care, >50% of foals with
meningitis progresses, other signs such as hyper- ment. Early identification of disease and early treat-
aesthesia, muscular rigidity, blindness, CN deficits, ment with appropriate antimicrobials are critical.
ataxia and paresis of all limbs are seen. Without
treatment, recumbency, coma, seizures and death BORRELIOSIS (LYME DISEASE)
can occur.
Definition/overview
Differential diagnosis Lyme disease, an immune-mediated disorder
EPM; hypoxic–ischaemic encephalopathy; viral caused by the spirochaete Borrelia burgdorferi, may
encephalitis; leucoencephalomalacia; cholesterol occasionally cause neurological disease (neurobor-
granuloma of the choroid plexus; trauma; verminous reliosis) in horses in certain geographical areas.
meningoencephalomyelitis (Halicephalobus deletrix); The high seroprevalence of Borrelia burgdorferi in
hepatic or intestinal hyperammonaemia; metabolic equine populations, paucity of well-documented
derangement. cases of Lyme disease in the same populations and
lack of understanding of the spirochaete’s patho-
Diagnosis genesis result in significant controversy regarding
Meningitis in foals should be regarded as a clinical the disease in equine practice.
emergency and early confirmation of the diagno-
sis is essential. This can be done by demonstrating Aetiology/pathophysiology
bacteria, increased numbers of inflammatory cells, B. burgdorferi is a spirochaete that is maintained in a
an elevated protein concentration and low glucose 2-year enzootic cycle involving Ixodes spp. ticks and
concentration in the CSF. Culture and cytology of mammals. Transmission to horses is known to occur
CSF, in addition to blood culture and culture of any during feeding activity of adult female ticks in the
other available septic sites, should be performed in summer, autumn or late winter. Serological studies
an attempt to isolate the causative organism. PCR have demonstrated a high seroprevalence in horses
may also be useful for identification of certain patho- in certain regions.
gens in the CSF.
Clinical presentation
Management Clinical signs of neuroborreliosos (Lyme disease)
Without bacterial isolation and sensitivity pat- in horses are variable, the most common including
terns, or identification of an organism on cytology, low-grade fever, hyperaesthesia, muscle fascicula-
treatment with broad-spectrum or combination tions, lethargy and behavioural changes. There can
antimicrobials is required. Commonly used treat- be spinous muscle atrophy, facial nerve dysfunction,
ments include aminoglycoside and penicillin spinal cord ataxia and paresis. Systemic signs that
combinations, potentiated sulphonamides, third- may accompany neuroborreliosis include uveitis,
generation cephalosporins and chloramphenicol. cardiac arrhythmias and polyarthritis (joint swelling
Meningeal inflammation considerably improves and stiffness).
penetration of drugs into the CSF. Duration of
antimicrobial therapy should be a minimum of Differential diagnosis
14 days, with therapy continuing for 7 days after It is clear that the signs of neuroborreliosis mimic
the resolution of clinical signs. If a septic focus a range of neurological diseases in horses includ-
is present, it should be addressed if possible. ing: bacterial meningitis; exertional rhabdomyolysis;
Aggressive supportive care, including nutritional septic arthritis; laminitis; WNV encephalitis; frac-
support, may be required. tured pelvis; trauma.