10. Diagnostics, therapy and prevention of neural diseases

Question 1

Describe TSE

Answer 1

Include Scrapie (sheep/goats) and BSE (cattle) — caused by prions.

Transmission:
* Spontaneous, genetic mutation (in sheep),
* Horizontal (e.g. eating infected meat/bone meal – BSE),
* Blood transfusion.

Forms:
1) Classical BSE: From feed. Behavioral changes → nervousness, hypersensitivity → ataxia, tremors, weight loss, death.

2) Atypical BSE: Spontaneous in older cattle. Signs: dullness, inactivity, muscle wasting, poor coat.

3) Scrapie (TSE in sheep/goats):
* Classical: Behavioral change, intense pruritus, wool loss, ataxia, teeth grinding, emaciation.
* Atypical: No pruritus.

4) Chronic Wasting Disease (deer/elk): No fear, aggression, PU/PD, drooling, weight loss, poor coat.

Incubation:
* BSE: 2–8 years
* Scrapie: 2–5 years.

Dx:
* PM – spongiform lesions in brainstem/cerebellum, sampling via foramen magnum.

Tx: NONE
Px: Proper disposal of specified risk material, surveillance at 48 months (cattle), 18 months (small ruminants).

Question 2

Describe Rabies

Answer 2

Lyssavirus, Rhabdoviridae
Cattle highly susceptible

Transission - through saliva from bite or through open wounds.

Dumb and furious form
CS: hypersalivation, behavior alterations, muscle tremor, abnormal posture, tenesmus, hydrophobia, aggression.
In the end - opisthotonus, seizures, paralysis and death.

Dx: IFAT (golden standard), virus isolation, PCR, histology (negri-bodies in neurons)

Tx: NONE
Px: VACCINATION - zoonotic

Question 3

Describe Aujesky’s disease

Answer 3

= Pseudorabies
Caused by Porcine Herpesvirus 1, Herpesviridae family.

Pigs = reservoir host, all mammals (except humans); others = dead-end hosts.
Direct transmission and horizontally.

CS (non-pigs): Intense pruritus, fever, neurological signs (ataxia, circling, nystagmus, etc.),
salivation, convulsions, rapid death (1–2 days).

Dx: PCR, ELISA, IFAT — from spinal cord near pruritic area + serum.

Treatment: None.

Question 4

Describe Listeria monocytogenes

Answer 4

Gram-positive bacterium found in soil and GIT, shed by asymptomatic carriers.
Transmission = direct and indirect.

Most important in ruminants is the neurological form, causing asymmetric CNS signs: circling, torticollis, cranial nerve deficits (e.g. ptosis, dropped jaw, tongue paralysis).

Also causes abortion, septicemia in young, and ocular disease.

Dx: CS, PCR or culture with samples from - brain (neuro), liver/spleen (septic), placenta (abortion).

Tx: High-dose penicillin or oxytetracycline for 7–14 days + supportive care.

Question 5

Describe Tetanus

Answer 5

= Lockjaw

Caused by Clostridium tetani, a Gram-positive anaerobe found in soil and GIT. It produces spores and two toxins:
1) Tetanospasmin (neurotoxin)
2) Tetanolysin (local tissue damage).

CS: stiffness, muscle spasms (masseter) - unable to open mouth -> lockjaw and progress with spastic paralysis to rest of body, opisthotonus, elevated ears/tail, prolapse of third eyelid.

Dx: CS, PCR, culture from wound or serum.

Tx: Wound cleaning, aeration - H2O2, Procaine penicillin, antitoxin, muscle relaxants, supportive care.

Px: VACCINATION

DDx: Hypomagnesemia.

Question 6

Describe botulism

Answer 6

Caused by Clostridium botulinum
* Gram-positive, anaerobic, spore-forming bacterium found in soil and GIT.
Infection via ingestion of preformed toxin or wound contamination.

Incubation: 2–14 days.
CS: Flaccid paralysis, head low, tongue paralysis, salivation, weak eyelid and anal tone, death from respiratory or cardiac failure.

Dx: History + clinical signs, PCR/ELISA from feed, serum, blood, GIT content, or carcass samples.

Tx: Antitoxin, supportive care, wound debridement and aeration.

Px: Vaccination.

DDx: Hypocalcemia, phosphorus deficiency.

Question 7

Describe Thrombotic meningoencephalitis

Answer 7

Caused by Histophilus somni, a Gram-negative opportunist found in the nasal passages of cattle.
Most severe in young cattle (6–24 months).

Forms:
1) Systemic: Fever, depression, inappetence.
2) Peracute: Sudden death.
3) Respiratory: BRDC signs – cough, nasal discharge, pneumonia.
4) Nervous: Ataxia, fever, head tilt, nystagmus, opisthotonus, death in 12–24 hrs.
5) Ocular: Conjunctivitis, epiphora, retinal hemorrhage.
6) Cardiac: Myo/pericarditis, CHF after respiratory signs.
7) Joint: Arthritis, lameness.
8) Reproductive: Abortion, infertility, endometritis, orchitis, mastitis.

Dx: CS history, PCR/culture from CSF, synovial fluid, blood.

Tx: Antibiotics, dexamethasone, NSAIDs, supportive care.

Px: VACCINATION