Foal: Nervous System Diseases Flashcards
Why are foals particularly tricky to diagnose/ assess for a neurological disorder?
- Foals naturally have more abrupt, jerky and exaggerated head movements
- Foals don’t always have a menace response- this is a learned response
- Their gait is normally choppy and dysmmetric, and often have a wide-base stance
- Preamture foals often are weak, quiet, sleep more, have a depressed suckle and have floppy ears + lips: this needs to be differentiated from a primary neurological disease
What clinical signs are considered abnormal in the foal?
- Barking, teeth grinding, jaw chomping, protruding tongue
- Loss of affinity for the mare, aimless wandering, excessive sleeping
- Head-pressing, dog-sitting
- Depression, coma, seizures
- Decreased responsiveness to stimuli
What are some of the common neurological disorders in the foal?
- Sepsis
- Prematurity
- Hypoxic-ischemia encephalopathy
- Neonatal isoerythrolysis
- Bacterial meningitis
- Viral meningitis
- Skull/ vertebral trauma
- Botulism (Shaker foal syndrome)
- Tetanus
- Tyzzer’s Disease
- Hydrocephalus
- Cerebellar abiotrophy of Arabian Foals
- Occipito-atlanto-axial malformation (OAAM)
What are some causes for seizures in foals?
- Parturition-asphyxia Syndrome (PAS)
- Trauma: maybe got kicked by the mare
- Sepsis
- Hemorrhage
- Metabolic causes
- Developmental
- Idiopathic
What are you looking out for when you suspect a foal is having a seizure?
- Oral and buccal movements (look like they are chewing gum)
- Facial grimacing, twitching
- Rapid eye movements + repetitive eye blinking
- Paddling, tonic posturing, extensor rigidity
Note: foals have a low seizure threshold, possibly due to cortical immaturity
What is the treatment protocol for seizures in foals?
- Anticonvulsants: Diazepam or Phenobarbital
- Anti-inflammatories: Prednisolone sodium succinate, or NSAIDs
- Supportive care
What are the most commonly identified bacteria in bacterial meningitis in the foal?
How do these bacteria get into the meninges?
- E.coli, Streptococcus spp, Actinobacillus equuli, Klebsiella, Staphylococcus spp
Most commonly get into the meninges through hematogenous spread, thus meningitis is commonly associated with septicemia
Can enter through 5 main routes of entry:
- The gut, the lung, the umbilicus, through a penetrating wound, and across the placenta in utero
What are the clinical signs associated with bacterial meningitis in the foal?
- Depression
- Coma
- Cervical stiffness
- Seizures
How can bacterial meningitis be diagnosed in the foal?
- Physical exam + neurological exam
- Blood work
- CSF analysis + culture
- Blood culture
- Blood gas analysis
How can bacterial meningitis be treated in the foal?
- Long term, broad-spectrum IV antibiotics (4-6 weeks minimum)
- Anti-inflammatories
- Supportive care
What is the etiological agent of viral meningitis in the foal?
Equine Herpesvirus-1
- Infection in utero
This is a rare, fulminant, generalized and rapidly fatal disease
What are the clinical signs associated with viral meningitis?
- Aborted or stillborn
- If born alive, diffuse cerebral neuro signs, icteric (hepatic failure), pneumonia and often die in 24 hours after birth
How can viral meningitis be diagnosed in the foal?
- PM examination
- Serological test on pre-colostral serum for EHV-1
Is there a treatment for viral meningitis in the foal?
How can viral meningitis be prevented in future pregnancies?
No
Prevention: vaccinate the pregnant mare
Prevention is better than trying to treat
What is the cause of Hydrocephalus in the foal?
Unknown causes
Thankfully this rarely occurs
How can Hydrocephalus be diagnosed in the foal?
Can Hydrocephalus be treated in the foal?
- Head may be enlarged and dome-shaped
- Rads
- CT scan
- MRI
No successful treatment has been documented yet
What is the most common route of entry for Botulism in the growing foal?
Through ingestion of toxin or spores
Rarely is it associated with wound entry
What clinical signs are associated with Botulism in the foal?
- Alert, hungry, but having difficulty swallowing and thus have milk dripping from their nose and mouth
- Depressed tongue tone
- Progresses to muscle tremors and generalized muscle weakness
- Dilated pupils
- Respiratory paralysis
How can Botulism be diagnosed in the foal?
- Clinical signs
- Can attempt to isolate the organism from the GIT, but this is difficult
What is the treatment for Botulism in foals?
How can Botulism be prevented in the foal?
- Potassium Penicillin: 20,000-44,000 IU/kg IV, QID
- Debride and clean wounds, if this was the route of entry
- Antitoxin: 200mls (30,000 IU) IV
- Supportive care: watch for aspiration pneumonia
Caution: Avoid the use of procaine penicillin, aminoglycosides and tetracyclines: these can potentiate the toxins neuromuscular blocking effects
Prevention: vaccinate the mares/ adults on the farm with botulism toxoid
What is the etiological agent of Tyzzer’s Disease?
What is the route of entry?
- Clostridium piliformis
This is a 100% fatal disease, thankfully it is rare
- Mare is thought to be the carrier in her GIT, and contaminates the environment
What are the clinical signs associated with Tyzzer’s Disease?
How can Tyzzer’s Disease be diagnosed?
- Acute death
- Depression
- Fever
- Pronounced icterus
- Feces may appear white/ grey (lack of bile production)
- Hypoglycemic
- Metabolic acidosis
- Inflammation
Dx: PM will see multiple foci of necrosis in the liver +/- lungs and heart and intestinal lesions
What is Lavender Foal Syndrome?
aka Coat Colour Dilution Lethal- CCDL
This is a genetic disease that affects newborn foals of certain Arabian bloodlines
These foals have severe neurological abnormalities, cannot stand and require euthanasia after birth
There is no treatment
What is Occipito-atlanto-axial Malformation (OAAM)?
This is a neurologic disorder caused by a malformation of
the occipital bone of the skull and the first two cervical vertebrae (the atlas and axis), with fusion of the
atlas to the base of the skull. An unusual variation of this malformation can be the presence of an
additional atlas. This abnormal structure causes a compression of the upper portion of the cervical
spinal cord, resulting in damage and neurological signs
This is inherited in Arabian lines
Foals are generally euthanized when diagnosis is made
