Bacterial and Fungal Diseases of Neuro Exam 1

What are the traits of listeria monocytogenes?

-gram positive

-rod

-ubiquitous in nature

-found in soil, water, feed, and spoiled silage

What are the pathogenic features of listeria monocytogenes?

-facultative intracellular bacteria

-expresses hemolysin to escape phagosome

-spread to adjacent cells without entering extracellular environment

-induction of host actin polymerization on to bacteria, resulting in cell to cell spread

How is listeria transmitted?

-ingestion and inhalation

-ingestion is common but disease is rare

-ingestion -> epithelial uptake -> hematogenous spread to uterus -> abortion

-ingestion or inhalation -> access to peripheral nerve endings -> ascends nerve sheaths -> neural disease

What are the clinical signs of neural listeria?

-circling

-fever

-multiple unilateral cranial nerve defects, especially V

-propulsive walking

-head tilt and pressing

-nystagmus

How do humans often get listeria?

-contaminated food

-elderly

-pregnant women

How to diagnose listeria?

-history and signs

-necropsy with histopath showing multifocal micro abscesses in brainstem

-IHC

-culture and PCR from blood, brain, or abortive tissues

How is listeria treated?

-antibiotics

-no vaccine

What are the traits of clostridium?

-gram positive

-anaerobic

-rods

-toxin based disease

-spore producing

What are the pathogenic features of clostridum botulinum?

neurotoxin is taken up by presynaptic portion of NMJ, resulting in degenerated synapse

What are the pathogenic features of clostridium tetani?

neurotoxin is absorbed by peripheral motor nerves resulting in excitation of motor neurons

How is c. botulinum transmitted?

-soil

-decaying organic matter

-found in GI tract of birds

-ingestion of preformed toxin

-wound contamination

How is c. tetani transmitted?

-wound contamination

-spores in the soil

How does C. botulinum cause disease?

-toxin absorbed by intestine -> enters blood stream -> reaches peripheral nerves resulting in flaccid motor paralysis

-death can occur by respiratory failure

What are the traits of c. botulinum in horses and ruminants?

-low to consume feed

-dysphagia

-decreased tongue and tail tone

-muscle weakness

-shuffling

-mydriasis

-decreased borborygmi

-bladder distension

-shaker syndrome in foals

T or F: c. botulinum is common in dogs and cats

False

How to diagnose c. botulinum?

-exclusion

-CBC, UA, and chemistry are normal

-identify toxin in feed, serum, or GI with ELISA

How to treat c. botulinum?

-administer antitoxin

-supportive care

-antibiotics if secondary infection

-rest

-vaccinate in endemic areas

What are the clinical signs of c. tetani?

-spastic paralysis

-tonic contraction

-conciousness persists

-death due to respiratory failure

List species most to least likely to get tetanus

horses and humans > pigs > goats and sheep > cattle > dog and cat > poultry

How to diagnose c. tetani?

-clinical signs

-wound history

-culture often unrewarding

How to treat c. tetani?

-clean wound

-supportive care

-reduce stimuli

-muscle relaxers

-antibiotics

-antitoxin

-prevent with toxoid vaccine

What are the traits of rickettsia rickettsia?

-gram negative

-coccobacilli

-obligate intracellular bacteria

-rocky mountain spotted fever

What are the pathogenic features of rickettsia rickettsia?

-invade and replicate in endothelial cells

-possess phospholipase resulting in inflammation and vasculitis

How is rickettsia rickettsia transmitted?

-infected eggs are laid

-larvae feed on small mammals

-larvae develop into infected nymph that feeds on mammals

-seasonal disease

What are the clinical signs of rickettisia rickettsia?

-rash

-edema

-petechiae

-joint and muscle pain

-renal disease

-encephalitis

-spinal cord disease

How to diagnose rickettsia ricketssia?

-signs

-season

-serological antibody test

-PCR

What is the treatment for rickettsia rickettsia?

doxycycline

What bacteria often cause otitis media and interna?

-staph

-strep

-e. coli

-pseudomonas aeruginosa

-proteus

-mycoplasma bovis in calves

What organisms commonly cause discospondylitis?

-staph

-strep

-e. coli

-brucella canis

What organisms often cause ulcerative keratitis?

-staph

-strep

-pseudomonas

-e. coli

-commonly a mixed infection

What are the traits of aspergillosis?

-ubiquitous fungus found in soil, vegetation and feed

-produce mycotoxins

How is aspergillosis transmitted?

-inhalation

-ingestion

-wound contamination

What is the pathogenesis of aspergillosis?

-tissue invasion results if macrophages and neutrophils fail

-elastase and enzymes produced aid in tissue invasion

What is aspergillosis commonly associated with?

decreased neutrophil number and function

How does aspergillosis present in horses?

-corneal infection from saprophytic fungi

-diagnose with corneal scrapping

-treat with long term topical antifungal itraconazole

How does aspergillosis present in canines?

-disseminated

-inhalation leads to nasal lesion that disseminates to CNS

-predisposing immunosuppression

-common in german shepherds

-diagnosis with imaging, biopsy, cytology

What are the traits of blastomyces, cryptococcus, and coccidoides?

-infection from inhalation

-mold transforms into yeast after inhaled

-disease occurs if host immunity is inadequate

-granulomatous lesions

-location and travel history are important

-treatment with long term anti-fungals

-no vaccine

-dimorphic fungi

What is the reservoir for cryptococcus?

birds

How can cryptococcus spread in the body?

-directly through cribriform plate

-hematogenously to CNS

What are the clinical signs of cryptococcus?

-meningitis

-liquefactive brain necrosis

When does yeast dissimination occur with cryptococcus?

-host is exposed to a large amount of spores

-host has impaired T-cell function

What is the most common systemic fungal disease of cats?

cryptococcus

Where is blastomyces dermatidis common?

midwest to southeast USA

T or F: dogs are 10x more susceptible to blastomyces than humans

True

Most cases of blastomyces occur where?

within 400 meter of water

What are the clinical signs of blastomyces?

-ulcerative dermatitis

-osteomyelitis

-ocular lesions

How to diagnose blastomyces?

-cytology and histopathy show broad based budding yeast

-culture on Sabourauds agar

What are the most relevant species of coccidioides?

-immitis

-posadasii

What is the most virulent fungus in the US?

Coccidioides

Where is coccidioides prevelant?

soils in the south west USA

How does coccidioides infection occur?

spore inhalation -> pneumonia -> systemic spread -> CNS involvement -> arthroconidia transform to spherules in host tissues and release endospores

What is the common name for cocciioides infection?

valley fever

When does prognosis for coccidioides become poor?

once it has reached the CNS

How to diagnose coccidioides?

-clinical signs

-large spherules and endospores on CSF cytology and serology

-reportable

How to treat valley fever?

-long term antifungal azole drugs and chitin synthesis inhibitors

-treat for up to a year