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.
