Infection control (SA5) Flashcards
What are the stages of the chain of infection?
- Pathogen
- Reservoir
- Portal of exit
- Mode of transmission
- Portal of entry
- Susceptible host
What is a convalescent carrier?
- Recovered from disease but still sheds into environment
What is a healthy carrier?
- Exposed to organism but doesn’t become ill
- Usually because immune system has fought disease previously
What is an open carrier?
- Continuously shed organism
- Usually weeks-months
- Can be life long
What is a closed carrier?
- Doesn’t normally shed disease
- Shedding triggered by stress or steroids
Where is MRSA found?
- Within naso-oral cavity
What is an infectious disease?
Caused by microorganism capable of invading and replicating within a host
What is a contagious disease?
- Can be passed from one animal to another
- Via direct or indirect contact
- Spread through contagions
What is a zoonotic disease?
- Can be passed from vertebrate animals to humans
- immunosuppressed, young, old and pregnant most at risk
What is contamination?
- Presence of microorganisms on body surface or inanimate object
What is colonisation?
- Presence of microorganisms with no clinical signs
What are pathogens?
- Disease producing microorganisms
- May live in or on the host
- Disrupts normal physiological function
What is a facultative anaerobe?
- Will grow whether oxygen is present or not
What is an epidemic?
- Increase in number of cases of a disease
- Above what is normally expected in that population
What is a pandemic?
- Epidemic of worldwide proportions
- Increase in number of cases of a disease worldwide above normal expectations
What is an endemic?
- Disease that permanently exists is particular populations
- At normal levels and is predictable
- What is an epizootic?
- Epidemic of an animal disease
- Increase in number of cases of an animal population above normal levels
What are the causal agents of infectious diseases?
- Bacterium
- Virus
- Protozoan
- Fungus
- Prions
- Ecto/endo-parasites
What are viruses?
- Tiny intracellular parasites
- Can only replicate within a host cell
- Can only attach to compatible cells
What is the structure of a virus?
- Each virus particle
- Core of nucleic acid (RNA or DNA)
- Surrounded by protein coat (Capsid)
- Together known as nucleocapsid
- Some viruses are enclosed in an envelope
What are virus envelopes made from?
- Lipoprotein and glycoprotein
- Some have glycoprotein spikes to help them attach to host cells
What is the name for spherical viruses?
Icosahedral
What is meant by an icosahedral virus?
- Spherical in shape
What makes enveloped viruses easier to kill?
- Envelopes are fragile
- Readily absorb disinfectants
How do viruses replicate?
- Attach to host cell and penetrate membrane
- OR being taken into cell by endocytosis
- Takes control of cell, instructs to produce more virus particles
- Released by rupture or no harm to the cell
How can viruses be diagnosed?
- Serology detects antibodies
- Antigens (Viral proteins) detected in serum
- PCR detects viral DNA/RNA but expensive
What are bacteria?
Single cell organism, vary in size and shape
What are the 3 basic shapes of bacteria?
- Bacilli (Ovals)
- Cocci (Circles)
- Spirochaetes (Spirals)
Bacteria cell walls
- Can be inhibited by Cephalosporins
- Some have slimy coat for protection and to enable them to attach to cells
- Some have pili/fimbriae to stick to host
What are the different arrangements of cocci?
- Diplococcus (2 cocci)
- Streptococcus (Chains of cocci)
- Staphlococcus (Bundles of cocci - grapes)
What is the name for curved Bacilli?
Vibrios
What is the optimum temperature for bacteria to replicate?
37 degrees
What are the 2 ways bacteria can replicate?
Binary fission
- Asexual
- Creates 2 identical cells
Conjugation
- Sexual
- Sharing of DNA only
- No new cell
How does antibiotic resistance come about?
Conjugation
Commensals
Bacteria living on animals and not causing harm
Facultative
- Opportunistic bacteria
- Will cause harm in immunosuppressed
Obligate
Bacteria that always causes disease
Saphrophytic
- Replicate on dead tissue
- Responsible for decay
Symbiotic and mutualistic bacteria
benefits both parties
How are bacteria diagnosed?
- Bacterial smears
- Grams stains
- Culture on nutrient medium
- Sensitivity testing
Examples of viral infections
- Parvo
- Lepto
- Distemper
- Myxo
- RHD
- FELV
- FIV
- Parainfluenza
Examples of bacterial infections
- Bordetella bronchiseptica
- Leptospira canicola
- Chlamydophila felis
What are fungi?
- Large group of organisms
- Ranging from micro to macroscopic
- Moulds, yeasts
What are the 3 fungi of veterinary importance?
- Dermatophytes (Ringworm)
- Yeasts (e.g Malassezia)
- Mould (Aspergillus)
Is ringworm a multicellular fungus?
Yes
What is Dermatophytes?
Ringworm
What are the 2 types of dematophytes?
Trichophyton mentagrophytes
- Dogs, cats, rabbits, guinea pigs
Microsporum canis
- Dogs and cats
What are the clinical signs of ringworm and how is it diagnosed?
- Circular hair loss, may be inflamed
- Some long hair cats are asymptomatic
- Hair plucks for staining or culture
- Some species fluoresce with woods lamp
- 50% of Microsporum canis apple green
- Spores can live on fomites for long periods
Are yeasts unicellular?
Yes
What is Malassezia pachydermatis?
- Yeast
- Found on skin normally
- Dematitis/otitis externa on susceptible pets
- Often during summer
- Can be greasy, has distinct odour
How is Malassezia pachydermatis diagnosed?
- Tape strips stained with methylene blue
- appears as bottle shapes under the microscope
What is Candida Albicans?
- Yeast
- Present in normal animals
- May cause clinical signs in young, old, immuno
- Thrush
What are the clinical signs of Candida Albicans?
- White plaques in mouth
- Ulcers
- In birds sour crop
What is a protozoa?
- Single cell organisms
- Many capable of independent movement
- Many survive outside body in moisture films
How are protozoa diagnosed?
- Cysts in faeces
- Pooled samples required
- Results may be unreliable
- ELISA or PCR tests are more expensive
Is toxoplasma zoonotic?
- Yes
- Can cause spontaneous abortion
What are prions?
- Mutated proteins leading to serious neurological disease
- Spread by ingestion of infected tissue, especially brain and spinal cord
- Genetic predisposition may be required, proven in sheep
- Prions are always fatal
