Guinea Pigs (Laboratory) - Pathology
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Introduction
Guinea pigs or “cavy” originate from South America and in the wild are a type of burrowing animal. They are nocturnal herbivores and were originally domesticated by the Incas as a source of nutrition. Guinea pigs are widely used in experimentation for a number of reasons, including highly developed young at birth (due to a relatively lengthy gestation period), the ability of the young to eat solid food at age 2-3 days, being fully haired and completely mobile. These factors reduce many issues and complications regarding the use of experimentation animals. Guinea pigs are also among the easiest laboratory animals to handle and can be housed in open top cages due to their in ablility to climb or jump.
Guinea pigs have been used for a broad spectrum of scientific purposes including the production of antibodies, tumor studies, disease studies and nutritional studies. Guinea pigs have been used since the 17th century and in 1990 were even launched into space as scientific passengers by China. One of the most common experimental uses of Guinea Pigs in the past has been for the standardisation and assessment of vaccines.
Strains and Stocks
When compared with the continuous and long term breeding strains of mice such as the F344 and LEW, the breeding of Guinea pigs is not as well developed and there are few specific strains in use. The outbred strains available are mainly the Hartley, Dunkin-Hartley and Albino. Inbred strains available are strains “2” and “13”, although these are uncommon compared to the outbred strains and are only used for very specific research. There are relatively less guinea pig breeders available of the quality required for experimental use and there are likely to be considerable variations between strains from different breeders. The total number of experimental guinea pigs in use as of 2007 was 2% of the total animals used.
Other types used within experimental research are the hairless strains that were developed in the 1980s specifically for dermatological use. These strains are often a result of a spontaneous genetic mutation from the strains described above. The recently popularised “skinny pig” is a type of guinea pig originally developed for laboratory use.
Physiology
Please find details of Guinea Pig physiology within the WikiNormals section. Physiological information available includes “General”, “Biochemical”, “Haematological” and “Breed” parameters.
Anatomy and Histology
This section has been included to allow familiarisation with the peculiarities of Guinea Pig anatomy to provide a context for some of the disease and pathological headings found below. Therefore only anatomical areas with specific features warranting emphasis have been included below;
Reproductive System
In males the inguinal canal remains open throughout the guinea pig’s life and this can lead to an increased risk of abdominal organ prolapsed post-castration. Males also have coiled vesicular glands which extend into the abdomen approximately 10cm in a similar manner to a females uterine horns.
Urinary System
Guinea pig urine is opaque and creamy yellow with a normal pH 9. The urine may also contain crystals of ammonium phosphate and calcium carbonate.
Respiratory System
Although guinea pigs have a normal mammalian respiratory system, a healthy guinea pig will only breathe through its nose and mouth breathing is therefore a sign of respiratory distress.
Digestive System
Guinea pigs have a longer colon than other rodents, accounting for 60% of the length of its intestines. Guinea pigs also have a relatively large caecum for the digestion of cellulose and it is able to contain up to 65% of the gastrointestinal contents at any time. The stomach is non-glandular and the female spleen is significantly larger than a male spleen.