-Specific or natural host: sheep, goats, cows, chicken, monkeys, and horses
-Laboratory animals: mice, rabbits, guinea pigs, rats, and rodents
The experiment animals are used for the following purposes
Preparation of inoculum
The material used for anima! inoculation may consist of filtered or unfiltered suspensions of organs or exudates. If the materials are unfiltered, it is important to add antibacterial substances such as penicillin and streptomycin, to prevent contamination or associated bacterial agents from becoming established. This is especially important in intracerebral inoculation, some bacteria which are ordinarily considered non-pathogenic may cause infection when directly introduced into the brain tissue of the living animal.
A general procedure for the Preparation of inoculum is as follows –
Route of Virus Inoculation
Mice and ferrets are usually employed for this route and inoculation is done with a V2 inch 23 s.w.g needle which should have a blunt tip. The animal is anesthetized, the animal is held keeping the head up, the needle is brought to the nostril and the required inoculum (0.05 ml in mice & 0.1 ml in ferrets) is dropped slowly.
Rat, mouse, hamster
Cattle sheep goat
Routes of virus inoculation for different animals
It may be an advantage to withdraw blood samples at regular intervals from experimental animals to detect the possible development of specific antibodies (eg. Q fever) and to cull and carry out post-mortem examination of some animals during the course of the experiment. Clinical symptoms, the development of visible lesions, abnormal behavior, and all deaths, whatever the cause, should be carefully observed and recorded. At the termination of an experiment involving infectious material, all bedding utensils cages, carcasses and tissues should be removed, burned, sterilized, or thoroughly cleaned by the most appropriate method. Animals infected experimentally must be held in separate isolation rooms and all persons handling infected animals, cages or other contaminated materials must pay strict attention to personal cleanliness.
Special care must be taken when performing inclusions if the material is believed to contain virulent viruses or when specimens obtained from experimentally infected animals are being processed for further passage in animals or inoculated into eggs or cell cultures.
Detection of virus growth in the virus-infected animals
Infected animals are examined daily for:
i.Clinical signs of the disease such as feverish signs, respiratory distress, GIT involvement, CNS disorders, visible skin or membrane lesions
ii. Abnormal behaviour
iii. Defects in animal development
-Monitor the body temperatures – taken once or twice daily
Collection of samples
-Blood samples – at specific intervals to check for rising in antibody titre, presence of virus, and blood parameter changes
-Biopsy materials or tissue are collected at necropsy following deaths or culling at specific intervals, examined;
a) Macroscopically: for lesions-vesicle, pneumonia, hemorrhages
b) Histologically: pathological changes- inclusion of bodies
c) Serologically– IFAT, ELISA, for specific viral antigens
d) Microscopically using EM to observe the virus particles
e) By isolation of the infectious virus