Lecture 11: Bacterial Neurological Diseases of Ruminants

the majority of ruminant neurologic diseases are

bacterial

listeriosis (circling disease)

acute meningoencephalitis of ruminants (not usually neonates) characterized by circling and cranial nerve deficits

listeria monocytogenes

• gram-negative, facultative anaerobe

• psychrophile

• could potentially be an inhabitant of mammalian GI tracts (and not cause disease)

clinical signs of listeriosis

• signs related to caudal cranial nerves → affected cattle are usually visual

• initial signs are anorexia, depression, excessive salivation

• proprioceptive deficits, head pressing, depressed consciousness, constant or sporadic walking or circling

• dropped jaw or facial anesthesia

• ptosis, loss of menace, absent palpebral reflex, drooped ear, loss of levator nasolabialis muscle function, decreased lip tone

• head tilt and tendency to circle to the side with the lesion

• stertorous breathing, dysphagia, paresis or paralysis of the tongue

nystagmus from listeriosis

• involuntary rhythmic side to side, up and down or circular motion of the eyes

• changes as the position of the head is altered

if listeriosis not treated in time, then

signs will progress to coma, convulsions, and death

listeriosis diagnosis

• usually not an inflammatory leukogram

• CSF analysis → mononuclear pleocytosis with a mildly elevated protein

• microabscesses in brainstem and immunohistochemistry

which anti-microbial would be illegal to use for listeriosis?

• enrofloxacin → no extralabel usage is permissible in food animals

• sulfa drugs → no extralabel usage in lactating dairy cattle is permissible

• ceftiofur → extralabel use is allowed in major food animal species, but requires use of the label dose, route, and frequency

listeriosis treatment

• can be weeks to months

• IV, oral, or enteral fluids → swallowing can be impaired

• antibiotics, → oxytetracycline, procaine penicillin G, potassium penicillin

• good footing and environment

listeriosis EEP

• gram-positive bacterium listeria monocytogenes

• mostly sporadic; occasional outbreaks

• hematogenous or ascension of cranial nerve

• sources → silage, shed in the feces, rotting vegetation, survives in soil

proper silage should be anaerobic and have a pH of

< 5.4

listeriosis control and prognosis

• no vaccines

• outbreaks due to high environmental contamination often associated with spoiled silage

• mortality rate for untreated cases nearly 100%

• most ruminants treated properly and in a timely manner survive

bovine thrombotic meningoencephalitis (TEM)

• a neurologic disease of mainly feedlot cattle, characterized by sleep-like depression (somulent) and death

• agent of disease → histophilus somni

TEM/TEME: H. somni

• gram-negative coccobacillus

• commensal inhabitant of bovine mucosa

• enters via breaks in mucosal integrity from viral infections or other bacterial infections

TEM/TEME clinical signs

• acute onset, anorexia, staggering, fever, and depression

• blindness, paralysis, tonic-clonic seizures, opisthotonos

• partial paralysis of multiple cranial nerves, including proprioceptive deficits with knuckling, crossing over, and interference

• death may occur within 2 hours

TEM/TEME diagnosis

• CBC: inflammatory leukogram

• complement fixation → titers usually > 1:400 in acute cases

• CSF → neutrophilic, high RBCs, and protein

• culture brain and kidney for H. somni

TEM/TEME postmortem diagnosis

CNS vasculitis, infarction, and abscess formation

main differentials of TEM/TEME

polioencephalopathy, lead poisoning, and water intoxication

TEM/TEME treatment and prognosis

• antibiotics → oxytetracycline, florfenicol, tulathromycin

• supportive therapy → fluids and electrolytes, anticonvulsants as necessary

• prognosis → still ambulatory = fair to good; downer = poor

TEM/TEME EEP

• gram-negative histophilus → winter months most common, shipping fever risks

• entry via respiratory system → bacteremia → thrombosis of small vessels of brain → infected endothelial cells degenerate and desquamate → exposes subendothelial collagen → initiates blood-clotting cascade and thrombosis

TEM/TEME control

• effective vaccines can reduce incidence and severity but problems → low morbidity disease, the economics of using vaccines should be considered

• not always routine in cow-calf herds

• standard BRDC control measures

meningitis clinical signs

• depression, fever, diarrhea, navel ill, arthritis, sinusitis, and otitis → the failure of passive immunity (FPI/FPT) calf

• hyperesthesia

• spinal reflexes are normal to hyperresponsive

meningitis diagnosis

• best test is CSF tap → neutrophilic pleocytosis, increased protein, fluid may be turbid to whitish, foamy and may clot, pandy test is strongly positive

• CSF glucose negative

• culture and sensitivity of CSF

• CBC

• blood cultures

meningitis treatment

• use broad spectrum to gram-negative spectrum

• anti-inflammatories → NSAIDs, steroids

• fluid support → plasma transfusions, ringers, electrolytes, and glucose

• anti-convulsants as needed

meningitis EEP

• history of passive failure → check and treat navels

• agents are usually gram-negative bacteria

• hematogenous route of infection or direct inoculation

meningitis control and prevention

• insure adequate colostral intake for neonatal calves

• prognosis is fair to poor → case fatality rate is high

• prepare client for → extended therapy, poor likelihood of success, residual deficits