ANSC 100

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Author:
mct
ID:
178624
Filename:
ANSC 100
Updated:
2012-10-20 19:49:30
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Infectious Diseases
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Part 4: infectious Diseases
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  1. Infectious
    Body is invaded by pathogenic agent which, under favorable conditions, multiplies and produces effects which are injurious
  2. Agents responsible for infectious diseases
    • Bacteria
    • Fungi and yeasts
    • Viruses
    • Prions
    • Parasites
    • -protozoa
    • -worms
    • -arthropods
  3. Adjuvants
    Are added to vaccines to stimulate the immune system's response to the target antigen, but do not in themselves confer immunity
  4. Bacteria
    Prokaryotes are single celled organisms that do not have a nucleus, mitochondria or any other membrane bound organelles
  5. Clostridial Diseases
    Clostridium spp
    • Diseases of considerable economic importance
    • Ubiquitous in soil and ingesta
    • May be prevented by vaccination
    • Polyvalent vaccines with up to 7 or 8 key antigens
    • Include Tetanus, Blackleg, Botulism
  6. Clostridium tetani
    • Causes generalized paralysis of muscles, especially jaw
    • Horses>Humans>Dogs
    • Occurs throughout the world
    • Organisms commonly present in feces
    • Continuously shed, sporulate and persist in environment
    • Infection from wound contamination, especially punctures
    • Incubation of 1-3 weeks
    • Bacteria remain localized, begin producing toxin in 4-8 hours
    • Treatment: debride wound, penicillin, neutralize circulating toxin (tetanus antitoxin), supportive care
    • Prevention: vaccinate!
  7. Clostridium botulinum
    • Fatal progressive flaccid paralysis of all voluntary muscles
    • Ingestion of botulinum toxin in contaminated food or water
    • Cattle, sheep, goats>pigs, dogs, cats
    • Often from a carcass, or decaying plant material
    • Epizootics occur in waterfowl in eastern Alberta lakes
    • Treatment: supportize, only possible in subacute cases
    • Prevention: good husbandry, disposal of carcasses, discard spoiled feed (silage), vaccination in enzootic areas
  8. Blackleg
    C chauvoei
    • Similar lesions from C. novyi, C. septicum
    • Peracute, noncontagious, highly fatal
    • Gaseous edema of muscles, severe toxemia
    • Common in young cattle, rare in sheep
    • Soil-borne; route of entry??
    • Mostly hot months
    • High economic losses (up to 100% mortality) in outbreaks in endemic areas
    • Anaerobic, motile, spore-forming
    • C/S: found dead; lameness, swelling
    • R/O: Anthrax; lightning strike
    • Treament: usually too late
    • Prevention: vaccinate, more from affected pastures, burn or deep burial of carcasses
  9. Clostridial Enterotoxemia
    • Ubiquitous in env't
    • May be isolated from GIT of most healthy animals
    • 5 types, A-E
    • Types A,C,D most common in North America
  10. Fungi
    • Eukaryotic, lack chlorophyll
    • Facultative anaerobes/strict aerobes
    • Chemotropic, nutrition by absorption
    • Grown in many forms
    • Widely distributed (air, water, soil, decaying organic debris)
    • Approx 100 spp. are pathogens to humans and animals
  11. Mykos
    Fungus
  12. Mycosis
    Disease caused by a fungus
  13. Mycology
    Study of fungi
  14. Fungal Groups
    Yeast, Moulds, Dimorphic
  15. Major Developments in Mycology
    • Increase in number of immunocompromised patients
    • Newly developed antifungal drugs
    • Antifungal susceptibility testing
    • Resistance to antifungal drugs
  16. Prion Disease
    • Prion: small proteinaceous infectious particles which resist inactivation by procedures that modify nucleic acids
    • spongiform encephalopathies - post mortem appearance of the brain with large vacuoles in the cortex and cerebellum
    • Scrapie - sheep
    • BSE - cattle
    • CWD - muledeer, elk
    • TME - mink
  17. Bovine Viral Diarrhea
    • RNA Virus, acute, contagious disease of cattle
    • Worldwide prevalence, spreads rapidly by contact
    • Virus in feces and urine
    • Spread on fomite
    • Different disease forms due to different strains (cytopathic, noncytopathic)
    • All ages susceptible though mostly between 6-24 mo
    • Colostral antibody protective to about 6 months
    • Reservoir inpersistently infected cattle
    • Calf may be born infected or be aborted, or be born and have malformations
  18. BVD - Mucosal Disease Complex
    • Calves: Rapid onset of fever, dry cough, oral/nasal discharge, oral ulcers, diarrhea; 10-50% of calves under 6 months may die
    • Cows: Weight loss, decreased milk production, abortion, fetal mummification
    • Treatment: only symptomatic - often of no use.
    • Prevention: Prevent introduction of infected animals
    • Buy Vaccinated animals from healthy herds
    • Isolate after arrival, etc
    • Decrease Exposure by: Preventing manure contamination of feed, water and animals' coats
    • Housing dairy calves in individual hutches
    • Isolating sick animals
  19. Protozoa
    • Single celled animals, wide variety of size/morphology
    • Groups: ciliated protozoa, amoeboid protozoa, flagellate protozoa, spore-forming protozoa
  20. Helminths (worms)
    • Often complex life cycles, often intermediate hosts
    • Flatworms: tapeworms and fluke
    • Roundworms: Equine strongyles, guinea worm
  21. Bovine Ostertagiasis
    • Nematode worm
    • Ostertagia ostertagi
    • Most common cause of parasitic gastritis in cattle
    • Weight loss, diarrhea, primarily young cattle in first grazing season, herd outbreaks, sporadic individual adult cases
    • Direct life cycle: Eggs passed in feces, under optimal conditions develop within fecal pat to infective 3 stage within 2 weeks; L3 larvae emerge under moist conditions onto grass, after ingestion, L3 moults in the rumen then develops in lumen of an abomasal gland; two more moults occur, then adult emerges about 18 days later, and becomes sexually mature on mucosal surface
    • Pathogenesis: O. ostertagi in numbers in abomasum causes severe damage, in heavy infections, up to 40,000 adult worms can be present
    • C/S: inappetance, weight loss, diarrhea, in light infection - sub-optimal weight gain
    • 2 Types: Type 1: symptoms seen in calves grazed intensively in 1 grazing season, as result of larvae ingested 3-4 weeks earlier (mid-July onwards)
    • Type 2: Symptoms occur in yearlings, usually in late winter or early spring following their first grazing season, from maturation of larvae ingested in previous autumn and waiting for week immune system
    • Diagnosis: Clinical signs, season, grazing history, fecal egg counts
    • hypoproteinemia, Ventral Edema, post-mortem exam
    • Treatment: responds to modern dewormers such as ivermectin
    • Control: routine deworming of calves, rotational grazing

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