PIL A- Species Specific Module- Common Disease and Symptoms Flashcards
Causes of disease
Infection (species specific), Neoplasia, Injury, Toxin, Allergy, Genetic malformation, etc…
Subclinical disease
An illness that is below clinical detection.
Alters the host physiologically & biochemically despite healthy appearance.
Reduces the host resistance to stress.
Can be zoonotic disease = infectious diseases which can spread between animals & humans: poses risk to both species; e.g. LCM, Hantaan virus, reovirus, leptospirosis, streptobacillus monofiliformis, salmonella, Pasteurella, human influenza.
Affects validity of results -> Increase numbers of animals required to statistically satisfy hypothesis.
Health status
: Lab animals kept & bred under a variety of regimes according to health status:
(1) Conventional; (2) Specified pathogen free ; (3) Gnotobiotic
Conventional
Animals kept in clean rooms, cages washed / sanitised frequently.
Technicians adopt good hygiene procedures.
Food and Bedding - reliable source & storage and handled hygienically.
Subclinical and clinical disease can be introduced by air and staff – varied health status.
Disease incidence fluctuates continually.
After several years tend to develop background pattern of infection which varies in intensity but is consistent.
Specified Pathogen Free (SPF)
Air supply – filtered (&therefore sterilised) via HEPA filter.
Sterilised Food/ Bedding/ Appliances.
Staff adopt strict hygiene procedures.
Free from infection (not 100% effective) – in theory no change of health status.
Monitor animals ~ every 3-6 months for infection.
Screened for:- Fresh kill, serology, bacteriology, autopsy for specific agents.
Gnotobiotic
Ensure no exposure to micro-organisms.
Usually kept in plastic film isolators, completely self-contained, ventilated with conditioned sterile air.
Sterilised food, water, bedding and utensils.
Use of air locks = animals never direct contact with handlers.
Lack normal intestinal flora = differ biochemically and metabolically from other animals.
Extremely expensive, time consuming & technically demanding.
Is health monitoring of animals used for scientific purposes a legal requirement?
Yes
How is health monitoring carried out?
Monitoring is carried out in two ways:
(1) Daily checking of each animal for signs of clinical disease & post-mortem examination of any animals dying.
(2) Routine screening of predetermined number of species to determine what micro-organisms are present or previously present.
Signs of clinical disease
Requires familiarity with animal health & illness – species specific changes in appearance & behaviour.
Observation of adversity -> recorded & named veterinary surgeon informed.
Routine screening
Predetermined number of representative young & adult animals (4 young and 8 old) are selected from a colony: numbers & frequency dependent on risk level, animals & environment. Detailed study of microorganisms & antibodies present: either undertaken by commercial lab 2/4 times yearly OR in house to monitor microbial population.
Samples collected for analysis: fresh faeces (gut content) for parasites, hair for sign of ectoparasites, ear swabs for ear mites & throat and nasal swabs for bacteria and viruses.
Clotted blood sample for antibodies to listed MO and for serum biochemistry.
Complete screening may help identify subclinical diseases from which health problems arise.
Sentinel monitoring
Screening a small group housed under the same conditions and micro-biological barriers.
Soiled bedding introduced into the group.
Detects subclinical disease.
Disadvantages - need to be shedding, stability of organisms in environment, sufficient amount in bedding.
Sendai, CARB bacillus, MIV
Animal selection
Choice of health status depends to some extent on type of research.
If using conventional or SPF then check if interaction between disease agents & research project have been documented.
Wild mice
Are secretive, burrowing & nesting animals which breed well.
small (20-40g), easy and economic to maintain, high genetic diversity & short generation time .
Outbred mice
Derived from mating unrelated mice & maintained by breeding techniques which minimise in-breeding, cheap and easily bred, identical phenotypically but not genetically. Strains will differ between labs – difficulty in reproducibility.
Inbred mice
> 20 consecutive brother/sister matings, eliminates virtually all genetic variation. Genetically identical & should be stable over time & country. Can compare with work elsewhere with same inbred strain.
Considerations in selecting wild/ outbred/ inbred
Drawback of inbred strains is they breed less efficiently than outbred & generally smaller with slow growth -> overcome by working with F1 Hybrids.
F1 Hybrids = first cross between 2 different inbred strains.
F1 hybrids are all genetically identical but will be genetically and phenotypically distinct from both parental lines and will not breed true -> in subsequent breedings the initial hybrid vigour will decline but homogeneity will develop over time.
Mutants
Over 500 different mutations in mouse – harmful mutations can occur BUT if one wants to breed for these then a Special Project Licence is required.
Congenic strains
Naturally occurring mutants have been mated with inbred strains, to produce an inbred strain with the mutation - animals that are genetically identical except for specific mutation with a few associated genetic loci.
Transgenic animals
Animal in which there has been a deliberate modification of the genome.
Produced by one of two methods: microinjection of gene construct into pronucleus of fertilised ovum or gene editing (i.e CRISPR).
Transgenesis can compromise animal welfare.
Gene insertions can result in higher incidence of foetal/post-natal deaths or cause deformities/organ failure.
Animals often used to stimulate human disease/abnormalities so chance of suffering pain and distress will be increased.
Recognition of disease
Through observation: general behaviour & appearance.
Check cage floor for diarrhoea, blood, uneaten food.
Check diet is okay: high protein promotes kidney disease, high fat promotes liver disease.
Obtaining medicines
As detailed in Medicines Order 1985.
All animals on designated premises are under care of Named Veterinary Surgeon.
Named Veterinary Surgeon = only person who can legally supply prescription only medicines for use in protected animals ie. antibiotics (EXCEPTION when an investigation into prescription only medicine is purpose of research project - use of medicine will therefore be specified within project licence).
Diarrhoea
Loose stools, liquid or mucus, weight loss.
Causative agents in mice: reovirus, coronavirus MHV, rotavirus, tyzzers, salmonella, ectromelia virus, Citrobacter freundii 4280
Causative agents in rats: reovirus, tyzzers, salmonella.
Respiratory disease
Breathing fast/heavily, ocular nasal discharges, sneezing, hunched, anorexia.
Causative agents in mice: pneumonia virus, Sendai, Pasteurella, Bordetella, Mycoplasma pulmonis.
Causative agents in rats: mycoplasma, Sendai, Pneumonia, Bordetella, Pasteurella, Corynebacterium, Streptococci, SDA, coronavirus.
Results in squinting, sneezing, photophobia, blinking, eye rubbing, cervical swellings, bulging eyes
Red tears = poryphrin pigments produced under parasympathetic control
CNS disease
Pasteurella, Lymphocytic Choriomeningitis (LCM), Theilers Encephalomyelitis Virus, MHC
Effects of experimental procedures in mice
MINUTE VIRUS:- Lymphocytic and immunosuppressant strains.
MOUSE HEPATITIS VIRUS:- Immunomodulation, contaminates neoplasms and alters enzymes.
REOVIRUS:- Transmittable neoplasms.
SENDAI VIRUS:- Immune responsiveness. Transplantable tumour growth. Anaesthesia. Depression of cell mediated immunity. Depression of blast transformation. Depression of phagocytosis and Decreased intrapulmonary antibacterial activity.
THEILERS ENCEPHALOMYELITIS VIRUS:- CNS research .
LYMPHOCYTIC CHORIOMENINGITIS (LCM):- Transplantable tumours. Stimulate/suppress immune system.
ELECTROMELIA VIRUS:- Tumour transmission.
LACTATE DEHYDROGENASE VIRUS:- Decreased auto-antibody production. Transient thymic necrosis. Lymphopaenia. Suppressed cell mediated immunity. Enhances/suppresses tumour growth.
Effects of experimental procedures in rats
TOOLANS (H1):- Contaminates transplantable tumours. Contaminates cell lines and modifies immune responsiveness
LCM
THEILERS
