The following points highlight the top four common laboratory animals employed in the laboratory for research purpose and for the diagnosis of the diseases. The animals are: 1. Rabbit 2. Guinea Pig 3. Rat 4. Mous.
Laboratory Animal # 1. Rabbit:
The body of the rabbit is closely covered with smooth hair or fur, except at a few places (the tip of the nose, a small portion of scrotum and the inguinal spaces). The rabbit has large and erect pinnae (external ears) with readily visualised musculature. The small external opening of the mouth is bound by a cleated upper lip and an undivided lower lip.
The external nostrils are ovoid in shape and are connected with the cleft in the upper lip. Prominent whiskers are present around the nose, over each eye and one or two on each cheek. The rabbit has large eyes (pink in albino rabbit) directed more laterally than those of most mammals. The hind legs are longer, muscular and powerful than forelimbs.
Use:
Rabbit was used in Friedman test of pregnancy, but with the advent of more easy and refined techniques, its use for this purpose has become limited.
Research areas where rabbit is experimental animal of choice include:
Hypertension, cardiac surgery, infectious diseases, metabolic disorders, ophthalmology.
In recent times, rabbit is considered as excellent animal model for the study of gastrointestinal diseases. It is also used in serology because its large ear vein facilitates easy withdrawal of blood.
In microbiology laboratory, rabbit is used to:
(a) Differentiate between human and bovine types of tubercle bacilli since it is susceptible only to bovine type;
(b) Prepare small quantity of antisera;
(c) Prepare Rabies vaccine;
(d) Isolate herpes, smallpox viruses.
Blood collection:
Marginal ear vein is the preferred site of blood collection; blood can also be withdrawn from the jugular vein, the orbital sinus, for large quantity (20 ml) of blood, the cardiac puncture of anaesthetized rabbit is preferred.
Laboratory Animal # 2. Guinea Pig:
The guinea pig is a short rodent, it does not have a tail. The head seen in profile is blunt and rectangular with small ears. The short thick neck emerges with the trunk. The limbs are unequal in length, the hind legs are longer than the forelegs. The guinea pig differs from the other laboratory rodents in many respects. It needs Vitamin C in the diet and is very susceptible to tuberculosis and to anaphylactic shock.
Use:
The guinea pig is very widely used in immunology (delayed hypersensitivity), immune responses, anaphylactic shock and allergic encephalomyelitis). It is also used in the field of biochemistry, toxicology, physiology, pharmacology, microbiology.
Particularly in microbiology, laboratory, guinea pig is quite useful:
(a) To isolate both human and bovine types of tubercle bacilli;
(b) For “Virulence” test for diphtheria bacilli and tetanus bacilli;
(c) To obtain “Complement” for serological test;
(d) To study rickettsial disease (typhus fever), viral diseases.
Blood Collection:
Small samples of blood (less than 0.25 ml) can be obtained by simple venesection of the marginal ear vein; large quantity by the cardiac puncture or from the metatarsal veins of anaesthetized guinea pig; repeated samples of small quantities from the orbital sinus.
Laboratory Animal # 3. Rat:
The albino rat has a wide head, rough fur and long ears. The tail length is always less than the body length. It has long cylindrical body, long thin tail and very short legs.
The head has a pointed snout with two silt-like nostrils, a narrow mouth with short lower jaw, and split upper lips, two small beady eyes, set so that they can look diagonally forwards and sideways, they have numerous long whiskers. It has a short neck. The trunk is slightly wider than the head.
Use:
It is used mainly for research in toxicity, nutrition, cancer. In microbiology laboratory, it is used to differentiate Yersinia pseudo-tuberculosis from Y. pestis which is pathogenic only to rat. In clinical pathology, it is used for Freak (Pregnancy) test.
Blood Collection:
Small blood samples can be obtained from a tail vein by snipping the tip of the tail, large quantity of blood can be collected by cardiac puncture or by orbital sinus from anaesthetized rat.
Laboratory Animal # 4. Mouse:
The albino mouse is small; has a slender body with a smooth hair coat, long pointed snout, prominent round ears and long flat front teeth.
Use:
It is extensively employed in the field of cancer research, toxicology, genetics, immunology, reproductive biology, diagnosis in the microbiology laboratory:
(a) For the isolation of pneumococcus from sputum since the mouse is very susceptible to pneumococci;
(b) For the isolation of causative organisms of relapsing fever, rat bite fever, trypanosomiasis;
(c) For the isolation of viruses;
(d) In clinical pathology for the Ascheim Zondek (Pregnancy) test.