Neurotoxic Clostridia Flashcards
How many species of Clostridium are there and how many are pathogenic?
200 species, 20 being pathogenic
What are some general characteristics of Clostridium spp?
large motile gram-positive rods, produce endospores, fastidious anaerobes, catalase and oxidase-negative, ferment carbohydrates and proteins
How are Clostridium spp divided?
neurotoxigenic, enterotoxigenic, histotoxic
What is the habitat of Clostridium spp?
soil, freshwater or marine sediments, normal flora of intestines, sequestered as endospores in muscle and liver, animal feces
How are Clostridium spp transmitted?
ingestion of spores, wound contamination
What is the protocol for specimen collection for Clostridium spp?
must be taken from live or recently dead animals, collect samples from blocks of tissue or fluids, place in anaerobic transport media and culture promptly
What are the cultural requirements for Clostridium spp?
media should be freshly prepared or pre-reduced to ensure the absence of oxygen, incubate in anaerobic jar containing hydrogen supplemented with 5-10% carbon dioxide
What media is used for the culture of Clostridium spp?
blood agar enriched with yeast extract, vit K, and hemin, cooked meat medium
What methods are used for the detection and differentiation of clostridia?
limited colony morphology, PCR, fluorescent antibody techniques, commercial biochemical kits, ELISA to detect toxins
What are the main virulence factors of clostridia?
production of toxins
What species of Clostridium are neurotoxigenic?
C. tetani and C. botulinum
What are some general characteristics of C. tetani?
gram-positive straight and slender rods, anaerobic, spherical terminal endospores with drumstick appearance
What disease is associated with C. tetani?
tetanus
How is tetanus transmitted?
spores originating from soil or feces contaminating wounds
What are some common sources of infection of tetanus?
nail wounds in horses, castration and docking wounds in goats/sheep, castration, dehorning, and nose-ringing in cows, contaminated umbilical tissues in young animals
What are the virulence factors of C. tetani?
tetanospasmin or neurotoxin, tetanolysin
What is the pathogenesis of tetanus?
anaerobic conditions and wound contamination -> spores germinate -> bacteria start producing tetanospasmin in 4-8 hours -> binds ganglioside receptors on neurons -> blocks release of inhibitory NTs -> continuous stimulation by excitatory NTs -> spastic paralysis and tetanus
What does tetanolysin do in terms of pathogenesis of tetanus?
enhances pathogenesis by increasing permeability of cytoplasmic membrane
What is the incubation period for tetanus?
5-10 days up to 3 weeks
Why are the clinical signs delayed in latent tetanus?
due to wound healing
What does the nature and severity of tetanus depend on?
anatomical site of replicating bacteria and the amount of toxin produced
What species are most susceptible to tetanus?
horses* > humans > mice > rabbits > dogs > cats > chickens > cattle* > sheep > goats > pigs
What clinical signs are associated with localized (ascending) tetanus?
stiffness and spasm of muscles close to injury due to toxin on local nerve endings
What clinical signs are associated with generalized (descending) tetanus?
stiff gait and “saw-horse” stance, lockjaw, mild tactile/auditory stimuli can precipitate seizures of muscle, altered heart and respiratory rates, dysphagia and prolapse of 3rd eyelid
What is the tetanic triad in humans?
trimius (lock jaw), risus sadonicus (grimace), opisthotonus (arched back)
How do you diagnose tetanus?
history and clinical signs, gram-stained smears, anaerobic culture from wound tissue, PCR, toxin assays
How do you treat tetanus?
antitoxin, toxoid, penicillin, wound debridement
How do you control tetanus?
routinely vaccinate with tetanus toxoid, antitoxin
What are some general characteristics of C. botulinum?
gram-positive, straight/slightly curved, motile, oval sub-terminal endospores with tennis racquet appearance
What disease is associated with C. botulinum?
botulism
How is botulism transmitted?
ingestion of pre-formed toxin (intoxication) or spores that germinate to release toxin
In what species is botulism outbreak common in?
waterfowl, cattle, horses, sheep, mink, poultry, farmed fish
What species are relatively resistant to botulism?
pigs and dogs. rare in cats
What are some predisposing factors of botulism in animals?
contaminated feed, dead rodents/carcasses, decaying plant/animal matter, contaminated poultry litter and bone chewing, warm moist decaying flesh (low O2)
What are some virulence factors of C. botulinum?
BoNT (botulinum neurotoxin; 8 types)
How is BoNT of C. botulinum inactivated?
by boiling for up to 20 minutes
What types of BoNT are of major significance?
Type C and D
What are some sources of type C BoNT?
dead invertebrates, maggots, rotting vegetation and carcasses of poultry (susc. to waterfowl, poultry), ensiled poultry litter, poor quality hay or silage contaminated with rodent carcasses (susc. to cattle, sheep, horses), meat, especially poultry carcasses (susc. to dogs, mink)
What are some source of type D BoNT?
carcasses and bones (susc. to cattle and sheep), fish (susc. to fish eating birds and humans)
What conditions are associated with type C alpha BoNT?
limberneck/western duck sickness in waterfowl and swans
What conditions are associated with type C beta BoNT?
forage poisoning in cattle, horses, and dogs
What conditions are associated with type D BoNT?
Lamsiekte in cattle and sheep from eating contaminated bones
What condition is associated with toxico-infectious botulism?
shaker foal syndrome
What is the pathogenesis of botulism?
botulinum neurotoxin enter bloodstream -> binds to peripheral cholinergic nerve endings -> blocks motor nerve endings -> inhibits release of NTs (ACh) -> descending flaccid paralysis starting from cranial nerves
What is the incubation period for botulism?
3-17 days, average 2-6 days
What are some of the clinical signs of botulism?
incoordination, dilated pupils, decreased salivation, dysphagia, progressive flaccid paralysis, head turned to flank in cattle, paralysis of respiratory muscles, death within days
What do low phosphorus levels in cows lead to?
chewing on dead carcasses leading to ingestion of toxin and botulism
What are some ways in which horses acquire botulism?
consumption of toxin in contaminated feed and water, contamination of wounds
How do you diagnose botulism?
history and clinical signs, toxin assays, toxin neutralization, ELISA, PCR, MLST
How do you treat botulism?
not usually successful, polyvalent antitoxin to neutralize unbound toxin in early stage, tetraethylamide and guanidine hydrochloride IV, ruminal or stomach lavage, fluid and nutritional supportive care
How do you control botulism?
vaccinate farm animals routinely with toxoid. bivalent vaccines to protect against types C and D. good feed quality and avoiding contamination. burn and properly dispose of dead carcasses
What are the options for vaccination against botulism?
short acting: 2 doses 4-6 weeks apart then annually. long acting: single dose and booster every 1-3 years
T/F: clostridia are gram positive
TRUE
T/F: clostridia are not capable of forming spores
FALSE
A dog present with lock jaw, stiff gait, and seizures. What is the name of the toxin which is responsible for these clinical signs? a) hemolysin b) epsilon c) tetanolysin d) tetanospasmin e) botulinum
d) tetanospasmin
T/F: botulinum toxin causes FLACCID paralysis
TRUE
