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==Introduction==

==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 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.  

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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.

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.

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==Strains and Stocks==

==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.

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.

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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 “[[Guinea_Pig_Breeds_-_WikiNormals#Skinny_Pig|skinny pig]]” is a type of guinea pig originally developed for laboratory use.

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 “[[Guinea_Pig_Breeds_-_WikiNormals#Skinny_Pig|skinny pig]]” is a type of guinea pig originally developed for laboratory use.

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==Anatomy and Histology==

==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;

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===

===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.

In males the inguinal canal remains open throughout the guinea pig’s life and this can lead to an increased risk of abdominal organ prolapse 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===

===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.

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.

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==Diseases==

==Diseases==

For ease of use, the diseases of guinea pigs listed below will be by body system, or where this is not appropriate in an “Other” category displayed after the body system sections. Those diseases listed below are not exhaustive but rather highlight common diseases encountered with laboratory guinea pigs.

For ease of use, the diseases of guinea pigs listed below are by body system, or where this is not appropriate in an “Other” category displayed after the body system sections. Those diseases listed below are not exhaustive but rather highlight common diseases encountered with laboratory guinea pigs.

 

==Integument System==

==Integument System==

Perhaps the most common finding in guinea pigs are skin problems related to diet, specifically a low vitamin C diet. Diet should always be considered when evaluating the integumentary system.<br />

Perhaps the most common finding in guinea pigs are skin problems related to diet, specifically a low vitamin C diet. Diet should always be considered when evaluating the integumentary system.<br />

The causal agent of this mycotic infection is commonly either ''Trichophyton mentagrophytes'' or ''Microsporum gypseum''. Areas of alopecia and seborrhoea can be found and hair can easily be plucked. Microscopic examination of hair plucked from areas of lesion is sufficient to confirm diagnosis.<br />

The causal agent of this mycotic infection is commonly either ''Trichophyton mentagrophytes'' or ''Microsporum gypseum''. Areas of alopecia and seborrhoea can be found and hair can easily be plucked. Microscopic examination of hair plucked from areas of lesion is sufficient to confirm diagnosis.<br />

Guinea pigs can suffer from a wide range of mycotic infections which can range in severity from mild skin changes to cystitis, pneumonia and reproductive disorders.<br />

Guinea pigs can suffer from a wide range of mycotic infections which can range in severity from mild skin changes to cystitis, pneumonia and reproductive disorders.<br />

===Mange===

===Mange===

Although this condition is rare in guinea pigs, its duration is 17 days. Care must be taken that sows do not develop mastitis during pseudopregnancy.<br />

Although this condition is rare in guinea pigs, its duration is 17 days. Care must be taken that sows do not develop mastitis during pseudopregnancy.<br />

===Pregnancy toxaemia===

===Pregnancy toxaemia===

Pregnancy toaemia is a metabolic disorder similar to twin lamb disease in sheep. Predisposing factors include obesity and stress leading to negative energy balance. The energy imbalance progresses to ketoacidosis together with aciduria, proteinuria and hyperlipaemia. There is also a fatty degeneration of the liver. <br />

Pregnancy toxaemia is a metabolic disorder similar to twin lamb disease in sheep. Predisposing factors include obesity and stress leading to negative energy balance. The energy imbalance progresses to ketoacidosis together with aciduria, proteinuria and hyperlipaemia. There is also a fatty degeneration of the liver. <br />

In cases of stress the sow stops eating, becomes depressed and will have a ruffled appearance. Some sows may also salivate profusely and the distinctive smell of ketones (pear drops) may be present. The condition is more prevalent in hot weather.<br />

In cases of stress the sow stops eating, becomes depressed and will have a ruffled appearance. Some sows may also salivate profusely and the distinctive smell of ketones (pear drops) may be present. The condition is more prevalent in hot weather.<br />

Necropsy will show an empty stomach and pathology including fatty liver and kidneys, fetae with varying levels of haemorrhage and large fat reserves in the abdomen.

Necropsy will show an empty stomach and pathology including fatty liver and kidneys, multiple fetae with varying levels of haemorrhage and large fat reserves in the abdomen.

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===Hypocalcemia (Eclampsia)===

===Hypocalcemia (Eclampsia)===

Pregnant sows can develop an acute calcium deficiency due to the metabolic demands of parturition combined with lactation. Obesity and stress are key predisposing factors.

Pregnant sows can develop an acute calcium deficiency due to the metabolic demands of parturition combined with lactation. Obesity and stress are key predisposing factors.

A wide range of commensal protozoa are carried and are not pathogenic except for Coccidia and Cryptosporidium species. Protozoan infections are generally the result of poor husbandry. Contact with rabbits can allow other rare protozoan infections in guinea pigs. <br />

A wide range of commensal protozoa are carried and are not pathogenic except for Coccidia and Cryptosporidium species. Protozoan infections are generally the result of poor husbandry. Contact with rabbits can allow other rare protozoan infections in guinea pigs. <br />

Eimeria caviae is the coccidial species contracted by guinea pigs eating contaminated food, however coccidiosis in guinea pigs is rare. Droppings will be slimy and contain blood. Oocysts will be present in the faeces and can be seen on microscopic examination.<br />

Eimeria caviae is the coccidial species contracted by guinea pigs eating contaminated food, however coccidiosis in guinea pigs is rare. Droppings will be slimy and contain blood. Oocysts will be present in the faeces and can be seen on microscopic examination.<br />

Cryptosporidium species that colonise the intestine will cause weight loss and diarrhoea. Microscopic pathologic findings will include flattened and irregular villi in the ileum together with a granulomatous infiltrate into the lamina propria and absorptive areas of the intestinal epithelium. In some cases the parasite itself may be visualised via parasitophorous vacuoles within the apical portion of the infected enterocyte.

Cryptosporidium species that colonise the intestine will cause weight loss and diarrhoea.

Microscopic pathologic findings will include flattened and irregular villi in the ileum together with a granulomatous infiltrate into the lamina propria and absorptive areas of the intestinal epithelium. In some cases the parasite itself may be visualised via parasitophorous vacuoles within the apical portion of the infected enterocyte.

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'''Ascaridae'''

'''Ascaridae'''

===Heatstroke===

===Heatstroke===

Although this can occur in outdoor guinea pigs exposed to direct sunlight, heavily pregnant females are the most susceptible especially if they have been deprived of water. This can be a problem during transportation or during problems with laboratory infrastructures such as air conditioning.<br />

Although this can occur in outdoor guinea pigs exposed to direct sunlight, heavily pregnant females are the most susceptible especially if they have been deprived of water. This can be a problem during transportation or during problems with laboratory infrastructures such as air conditioning.<br />