Week 11 - Infectious agents as a cause of subclinical disease in animals Flashcards
What are subclinical disease in animals
Diseases that are hard to detect in animals
What is one way to cause subclinical disease to turn to clinical
Due to other factors which often are environment that shift in favour of pathogen
- Weather
- Dietary change
What are some individual sub-clinical disease
- Dog with early stage of heartworm infection
- Cat with calicivirus
- Sheep with low nematode burden
- Cow with sub-clinical mastitis
- Parainfluenza virus in cattle without any associated bacterial disease (feedlot example)
- If sub-clinical disease remains sub-clinical at the individual level it may never result in problems (when did you last take an anthelmintic?)
What are some group sub-clinical disease
- Sheep nematodes
- Sheep lice
- Cattle nematodes
- Cattle mastitis
- Feedlot pneumonia (shipping fever)
- Johne’s disease (ruminants)
- Roundworms in puppies
- Cattery with calicivirus
- Pound with parainfluenza virus
What are the Clinical signs of mastitis
- Change in colour of milk
- Change in consistency of milk
- Change in volume of milk produced
- Animal may stop eating
- Change in size of udder
- Change in udder “tone”
What may be the direct loss of costs
– Reduced milk volume
– Reduced milk quality & changed payment band
– Reduced market access, poor quality milk may not be suitable for some applications eg. cheese
What may be the indirect loss of costs
– Reduced condition score
– Reduced reproductive success
– Increased chance of culling (cost of replacement)
– Infection of other stock
What maintains the infection in a farm
- Sub-clinical disease can be a vital method for pathogens to remain on a property
- Very difficult (if not impossible) to eradicate many nematode parasites from grazing properties
- Eg. Nematode population = animal + environment
- Different selection pressures on two different populations
How can weather lead to the change of sub-clinical disease for foot abscess
– Disease of sheep caused by multiple bacteria – Requires damage to hoof – Usually in wet conditions – Usually heavy sheep – Particularly after yarding them – Leads to abscess in foot (hence name!)
What can drought affect in the fields
– Animals “mobbed” together into several large groups, rather than many distinct smaller flocks
What is efficacy
ability to produce desired effect
What are the Regulation of veterinary treatment
- APVMA (Australia), FDA (USA) etc
- International harmonisation, but variation between countries and continents
- Difference between companion animals and food producing animals
- WHP & ESI
- Pharmacokinetics & pharmacodynamics (see toxins lectures in first semester)
- Costs a lot of money (millions) to register each drug (safety, efficacy, chemistry studies etc)
What are some ways in delivering treatment to animals
– oral,
– sub-cutaneous (applied under the skin.)
– intra-muscular,
– intravenous (administered into, a vein or veins)
– transdermal (route of administration wherein active ingredients are delivered across the skin for systemic distribution)
– intra-abdominal,
– intra-ruminal,
– intramammary (breast tissue)
– Topical (eg conjunctival) (applied directly to a part of the body)
– Aural (relating to the ear )
– intravaginal
– inhalation and
– suppository (cone-shaped object that you put in your body)
Different classes to treatment a disease
- Inhibition of cell wall synthesis
- Damage to cell membrane function
- Inhibition of nucleic acid synthesis or function
- Inhibition of protein synthesis
Factors and ways for Inhibition of cell wall synthesis
- Eg. Penicillins, cephalosporins (beta-lactam antibiotics)
- Cell wall = major difference between bacteria and mammalian cell
- Difference in cell wall between gram positive and gram negative (gram +ve = thicker)
Factors and ways for Damage to cell membrane
function
- Polymyxins, polyenes (amphotericin, nystatin), imidazoles (-azole) & monensin
- Damage to cell membrane leads to leakage of cellular contents and cell death
- Polyenes & imidazoles important in fungal therapy (see fungal)
Factors and ways for
Inhibition of nucleic acid synthesis or function
- Nitroimidazoles, nitrofurans, nalidixic acid, fluoroquinolones (-floxacin), novobiocin, firampin, sulfonamides, trimethoprim & 5-flucytosine
- Most act by binding DNA to inhibit replication or transcription (Trimethoprim-sulfonamide inhibit synthesis of folic acid)
Inhibition of protein synthesis
• Tetracyclines, aminoglycosides (-cin),
amiocyclitols (spectinomycin),
chloramphenicol, lincosamides and macrolides ( eg. Erythromycin & others)
• Selectively inhibit bacterial ribosomes compared to mammalian
• Affect either 30S or 50S ribosome
What is the difference between Bacteriostatic and bacteriocidal
• Capable of inhibiting the growth or reproduction of bacteria versus
capable of killing bacteria
• In general a bacteriocidal (kill) antibiotic is preferred where possible
What are the choices of antibiotic
• C & S, location of bacteria • Spectrum • Cidal versus static • Administration form • Duration of treatment • Ability to repeat dosage (wild animals) • Cost • Other – Gut flora – Reactions (birds and procaine)
When do you use antibiotics
front line when other preventives have failed
What are the preventives
– Good diet
– “good” bacteria (ruminal fluid for acidosis)
– environment
What are some drugs for
• Large number of different families of drugs • Some examples – Monensin – Amprolium – Lasolacid – Toltrazuril
What are some drugs against cestodes
- Praziquantel – active against wide range of tapeworms
- Niclosamide (salicylanilide) – used for tapeworms of sheep, cattle horses & poultry (also dogs and cats)
- Some benzimidazoles have moderate activity against tapeworms
