This document discusses meningitis in farm animals. It begins by defining meningitis as inflammation of the meninges, and noting the common clinical signs. For each major farm animal, it lists common causes of meningitis, including various bacteria, viruses, and other pathogens. It then covers the pathogenesis of meningitis, typical clinical findings observed, diagnostic testing including CSF analysis, potential necropsy findings, and recommended treatments which primarily include various antibiotics.

1. DR ANITA SEWAG
MVSc MEDICINE
1ST YEAR

2. MENINGITIS
 Inflammation of the meninges.
 Meningitis is usually associated with a bacterial
infection and is manifested clinically by fever,
cutaneous hyperesthesia, and rigidity of muscles.
 Although meningitis may affect the spinal cord or
brain specifically, it commonly affects both.
 Meningoencephalitis is common in neonatal farm
animals.

3. DO YOU KNOW ?
 Compared with adults, bacterial meningitis is more
common in neonates because their immune system is
immature, the blood-brain barrier is incomplete, and
umbilical infections are common, providing a nidus of
infection.

4. ETIOLOGY
Cattle
 Viral diseases including bovine malignant catarrh,
sporadic bovine encephalomyelitis
 Bacterial diseases including listeriosis, H. somni,
chronic lesions elsewhere in the body possibly
associated with meningitis in adult animals; rarely
tuberculosis.

5. Sheep
 Melioidosis, S. aureus (tick pyemia) in newborn lambs
 Pasteurella multocida in lambs
 Mannheimia (Pasteurella) haemolytica in lambs.
Pigs
 Glasser’s disease, erysipelas, salmonellosis;
 S. suis type 2 in weaned and feeder pigs.

6. Horses
 Strangles, Pasteurella haemolytica (also donkeys and
mules), Streptococcus suis, S. equi, Actinomyces spp.
 Klebsiella pneumonia, Staphylococcus aureus,
coagulase-negative staphylococci.
 Anaplasma phagocytophilum (equine granulocytic
ehrlichiosis), Borrelia burgdorferi, Sphingobacterium
multivorum, and
 Cryptococcus neoformans.

7. PATHOGENESIS

8.  Inflammation of the meninges causes local swelling
and interference with blood supply to the brain and
spinal cord.
 The signs produced by meningitis are thus a
combination of those resulting from irritation of both
central and peripheral nervous systems.
 Defects of drainage of CSF occur in both acute and
chronic inflammation of the meninges and produce
signs of increased intracranial pressure.

9.  In spinal meningitis, there is muscular spasm with
rigidity of the limbs and neck, arching of the back, and
hyperesthesia with pain on light touching of the skin.
 When the cerebral meninges are affected, irritation
signs, including muscle tremor and convulsions, are
the common manifestations.
 Meningitis is usually bacterial in origin, fever and
toxemia can be expected if the lesion is sufficiently
extensive.

10. CLINICAL FINDINGS
 Acute meningitis usually develops suddenly and is
accompanied by fever and toxemia in addition to
nervous signs.
 There is trismus, opisthotonus, and rigidity of the
neck and back.

11.  Motor irritation signs include tonic spasms of the
muscles of the neck causing retraction of the head,
muscle tremor, and paddling movements.
 There may be disturbance of consciousness manifested
by excitement or mania in the early stages, followed by
drowsiness and eventual coma.

12.  Blindness is common in cerebral meningitis but not a
constant clinical finding.
 In young animals, ophthalmitis with hypopyon may
occur, which supports the diagnosis of meningitis.
 The pupillary light reflex is usually much slower than
normal.
 Examination of the fundus of the eyes may reveal
evidence of optic disc edema, congestion of the retinal
vessels, and exudation.

13.  In uncomplicated meningitis the respiration is usually
slow and deep, and often phasic in the form of
Cheyne–Stokes breathing (a breathing pattern
characterized by a period of apnea followed by a
gradual increase in the depth and rate of respiration)
or Biot’s breathing (an irregular breathing pattern
characterized by groups of quick, shallow inspirations
followed by periods of apnea).
 Terminally there is quadriplegia and clonic
convulsions.

14. CLINICAL PATHOLOGY
 Cerebrospinal Fluid CSF collected from the
lumbosacral space or cisterna magna.
 In meningitis contains elevated protein
concentrations, has a high cell count, and usually
contains bacteria.
 Hematology - Hemogram usually reveals a marked
leukocytosis, reflecting the severity of the systemic
illness secondary to septicemia.

15. NECROPSY FINDINGS
 Hyperemia, the presence of hemorrhages, and
thickening and opacity of the meninges, especially
over the base of the brain, are the usual macroscopic
findings.
 The CSF is often turbid and may contain fibrin. A local
superficial encephalitis is often present.

16. Lesions
 Gross lesions are extremely variable depending on
cause and location and whether the disease is diffuse
or multifocal. Pathologic changes characteristic of
meningitis include diffuse infiltration of leukocytes
into the leptomeninges.

17.  Listeriosis uniquely causes microabscesses deep within
the CNS parenchyma, which consist of accumulations
of neutrophils and microglial cell reaction with central
liquefactive necrosis.

18. Diagnosis
 The analysis of CSF is the most reliable and accurate
means to identify an encephalitis, meningitis, or
meningoencephalitis.
 The protein content of the CSF is usually also
significantly increased (>100 mg/dL), with an increase
in the globulin component of CSF.

19.  Occasionally, bacteria are seen on cytologic
examination of the CSF and identified with Gram
stain.
 Fungi and occasionally protozoa have been identified
in CSF, but serology is usually necessary to confirm
mycotic and protozoal infections in vivo.
 Serologic testing is available for most viral
encephalitides.

20. DIFFERENTIAL DIAGNOSIS
 Hyperesthesia, severe depression, muscle rigidity, and
blindness are the common clinical findings in cerebral
meningitis, but it is often difficult to differentiate
meningitis from encephalitis and acute cerebral
edema.
 Analysis of CSF is very useful in the differential
diagnosis of diseases of the nervous system of
ruminants.

21. TREATMENT
 The most promising antimicrobial agents for the
treatment of bacterial meningitis in farm animals are
trimethoprim-sulfonamide combinations, the third-
generation cephalosporins, and fluoroquinolones.

22. Excellent with or without inflammation
 Sulfonamides
 Third-generation
 Cephalosporins
 Cefoperazone,
 cefotaxime

23. Good only with inflammation
 Ampicillin
 Carbenicillin
 Cephalothin
 Cephaloridine

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