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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 />

===Ringworm===

===Dermatitis===

 

===Dermatophytosis (Ringworm)===

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===

This mite infection is commonly caused by ''Trixacarus caviae'', a sarcoptiform mite. Clinical signs usually occur 3-5 weeks after infection and lesions are usually visible around the head, shoulders and back. Hair is easily plucked and skin is usually seborrhoeic and pruritic. In some cases self trauma may also compound problems.<br />

This mite infection is commonly caused by ''Trixacarus caviae'', a sarcoptiform mite. Clinical signs usually occur 3-5 weeks after infection and lesions are usually visible around the head, shoulders and back. Hair is easily plucked and skin is usually seborrhoeic and pruritic. In some cases self trauma may also compound problems.<br />

===Liver Disease===

===Liver Disease===

Hair loss is a common cause of hair loss once parasitic and fungal infections have been removed. During liver disease the overall fur covering is sparse and the skin is thickened. Often this general hair loss is accompanied with seborrhea. <br />

Hair loss is a common cause of hair loss once parasitic and fungal infections have been removed. During liver disease the overall fur covering is sparse and the skin is thickened. Often this general hair loss is accompanied with seborrhea. <br />

===Abscesses===

===Abscesses===

Abscessess are mainly caused by fighting and various types of bacteria have been isolated as the causal agent. These include ''Pseudomonas aeruginosa'', ''Pasteurella multocida'', ''Corynebacterium pyogenes'', ''Staphylococcus aureus'', ''Streptococcus spp.'' and other Enterobacteria. There will be localised swelling and most abcessess occur in the throat area.<br />

Abscessess are mainly caused by fighting and various types of bacteria have been isolated as the causal agent. These include ''Pseudomonas aeruginosa'', ''Pasteurella multocida'', ''Corynebacterium pyogenes'', ''Staphylococcus aureus'', ''Streptococcus spp.'' and other Enterobacteria. There will be localised swelling and most abcessess occur in the throat area.<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 />

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 />

 

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===Miscarriage and Abortion===

===Miscarriage and Abortion===

If abortion occurs early in gestation (up to 40 days) the sow will commonly not be systemically affected. Later than 40 days will result in systemic illness with severe blood loss with potentially fatal consequences. <br />

If abortion occurs early in gestation (up to 40 days) the sow will commonly not be systemically affected. Later than 40 days will result in systemic illness with severe blood loss with potentially fatal consequences. <br />

This type of infection is usually caused when a foreign body such as saw dust becomes trapped in the prepuce causing preputial dermatitis. This can lead to a swelling of the prepuce but also cause inability to copulate. Similarly it has been found that saw dust can also block the vagina of the female also leading to an inability to achieve copulation. <br />

This type of infection is usually caused when a foreign body such as saw dust becomes trapped in the prepuce causing preputial dermatitis. This can lead to a swelling of the prepuce but also cause inability to copulate. Similarly it has been found that saw dust can also block the vagina of the female also leading to an inability to achieve copulation. <br />

To decrease the risk of preputial infections and vaginal blockage wood shavings are superior to saw dust.<br />

To decrease the risk of preputial infections and vaginal blockage wood shavings are superior to saw dust.<br />

==Urinary System==

==Urinary System==

===Polydipsia===

===Polydipsia===

The clinical symptoms of pneumonia include dyspnoea, ruttling (see above), sneezing, nasal discharge and coughing. If left untreated, guinea pigs can become depressed anorexic and it can become a fatal infection. In guinea pigs pneumonia can be caused be various bacterial and viral agents including ''Bordetella bronchiseptica, Streptococcus zooepidemicus, Streptococcus pneumonia, Klebsiella pneumonia, Pseudomonas aeruginosa and Pasturella spp.''<br />

The clinical symptoms of pneumonia include dyspnoea, ruttling (see above), sneezing, nasal discharge and coughing. If left untreated, guinea pigs can become depressed anorexic and it can become a fatal infection. In guinea pigs pneumonia can be caused be various bacterial and viral agents including ''Bordetella bronchiseptica, Streptococcus zooepidemicus, Streptococcus pneumonia, Klebsiella pneumonia, Pseudomonas aeruginosa and Pasturella spp.''<br />

Diagnosis is via isolation of the causal agent from a culture of the nasal discharge.<br />

Diagnosis is via isolation of the causal agent from a culture of the nasal discharge.<br />

'''''Bordetella'' Pathology''': mucopurulent rhinitis, purulent bronchitis and tracheitis. Exudate can also be found in the tympanic bullae.<br />

'''''Bordetella'' Pathology''': Bordatella has an affinity for ciliated respiratory epithelium. Necropsy may reveal mucopurulent rhinitis, purulent bronchitis and tracheitis. Exudate can also be found in the tympanic bullae. There may also be pulmonary consolidation (usually anterioventral). Pleuritis or pyosalpinx may be seen.<br />

'''''Streptococcus'' Pathology''': necropsy will show fibrinopurulent bronchopneumonia, with or without fibrinous pleuritis and pericarditis. Lungs will often contain a sanguinous fluid.

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'''''Streptococcus'' Pathology''': necropsy will show fibrinopurulent bronchopneumonia, with or without fibrinous pleuritis and pericarditis. Lungs will often contain a sanguinous fluid. Histologically, an acute fibrinosuppurative bronchopneumonia is present with thrombosis of pulmonary vessels. Infiltrating cells may be elongate and form palisading patterns in affected airways.

===Adenovirus===

===Adenovirus===

Adenoviridae do not require co-infection with bacteria in order to become pathogenic within the respiratory system. The infection may have no clinical symptoms but in susceptible animals such as those that are stressed or immune-deficient it can be fatal.<br />

Adenoviridae do not require co-infection with bacteria in order to become pathogenic within the respiratory system. The infection may have no clinical symptoms but in susceptible animals such as those that are stressed or immune-deficient it can be fatal.<br />

==Digestive System==

==Digestive System==

===Infectious Causes of Diarrhoea===

===Infectious Causes of Diarrhoea===

'''Salmonella'''

'''Salmonella'''

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''Salmonella typhimurium'' and ''Salmonella enteriditis'' are the common causative agents and are often associated with contaminated food and bedding. Diarrhoea may be haemorrhagic, cause septicaemia and can also cause sudden death. Diagnosis is via isolation and culture of the ''Salmonella spp'' via faecal samples.<br />

''Salmonella typhimurium'' and ''Salmonella enteriditis'' are the common causative agents and are often associated with contaminated food and bedding. Diarrhoea may be haemorrhagic, cause septicaemia and can also cause sudden death.  

Diagnosis is via isolation and culture of the ''Salmonella spp'' via faecal samples.<br />

Chronic cases and those that recover from a ''Salmonella'' infection are likely to become carriers and should be destroyed to prevent further outbreaks. <br />

Chronic cases and those that recover from a ''Salmonella'' infection are likely to become carriers and should be destroyed to prevent further outbreaks. <br />

'''Yersinia (pseudotuberculosis)'''

'''Yersinia (pseudotuberculosis)'''

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Acute forms of this disease can cause septicaemia and death within 48hrs. Chronic cases have more progressive clinical symptoms but will usually culminate in death after 3-4 weeks. During this 3-4 week period any young may become congenitally or neonatally affected. Diagnosis is via culture of ''Yersinia pseudotuberculosis'' from blood, lymph nodes or faecal samples.<br />

Acute forms of this disease can cause septicaemia and death within 48hrs. Chronic cases have more progressive clinical symptoms but will usually culminate in death after 3-4 weeks. During this 3-4 week period any young may become congenitally or neonatally affected. Diagnosis is via culture of ''Yersinia pseudotuberculosis'' from blood, lymph nodes or faecal samples.<br />

''Yersinia'' infections are transmitted via wild birds and other rodents contaminating their food, particularly green foods. Once the disease is endemic  in a breeding population some infections can be passed vertically in the milk. <br />

''Yersinia'' infections are transmitted via wild birds and other rodents contaminating their food, particularly green foods. Once the disease is endemic  in a breeding population some infections can be passed vertically in the milk. Macroscopic pathologic lesions include enlarged or abscessed lymph nodes and necrosis of liver and spleen.<br />

'''Clostridia'''

'''Clostridia'''

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Normally this species are present in the large intestines as commensals but during certain circumstances such as antibiotic administration they are able to proliferate and cause fatal enterotoxaemia. ''Clostridium'' species can be cultured from the lumen of the infected intestine.

Normally this species are present in the large intestines as commensals but during certain circumstances such as antibiotic administration they are able to proliferate and cause fatal enterotoxaemia. ''Clostridium'' species can be cultured from the lumen of the infected intestine.

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'''Antibiotic-Induced Enterotoxemia'''

'''Antibiotic-Induced Enterotoxemia'''

Bacterial overgrowth is associated with enterocolitis, septicemia and death.  Antibiotics implicated include penicillin, erythromycin, lincomycin, chlortetracycline, oxytetracycline, bacitracin, dihydrostreptomycin, cefazolin, cephalexin, cephalothin, ampicillin, clindamycin & gentamycin. All of the above species have been implicated as potential causative agents.

Bacterial overgrowth is associated with enterocolitis, septicemia and death.  Antibiotics implicated include penicillin, erythromycin, lincomycin, chlortetracycline, oxytetracycline, bacitracin, dihydrostreptomycin, cefazolin, cephalexin, cephalothin, ampicillin, clindamycin & gentamycin. All of the above species have been implicated as potential causative agents.

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'''Pathology:''' microscopic lesions during necropsy include extensive vascular congestion, submucosal hemorrhage and oedema, and sloughing of the absorptive epithelium throughout the GI tract

Macroscopic pathology during necropsy will include a distended cecum containing blood and hemorrhagic serosal and mucosal surfaces. Microscopic pathology during necropsy will include extensive vascular congestion, submucosal hemorrhage and oedema, and sloughing of the absorptive epithelium throughout the GI tract.

===Parasitic Causes of Diarrhoea===

===Parasitic Causes of Diarrhoea===

'''Protozoa'''

'''Protozoa'''

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A wide range of commensal protozoa are carried and are not pathogenic except for Coccidia. Protozoan infections are generally the result of poor husbandry. Contact with reabbits 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 />

'''Ascaridae'''

'''Ascaridae'''

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Ascaridae are not a natural parasite of guinea pigs but if housed outdoors in areas which has been contaminated with dog or cat faeces guinea pigs will suffer from weight loss, unthriftiness and diarrhoea.<br />

Ascaridae are not a natural parasite of guinea pigs but if housed outdoors in areas which has been contaminated with dog or cat faeces guinea pigs will suffer from weight loss, unthriftiness and diarrhoea.<br />

==Musculoskeletal System==

==Musculoskeletal System==

===Pododermatitis===

===Pododermatitis===

The diet should contain a maximum of 1600iu of vitamin D per kg.<br />

The diet should contain a maximum of 1600iu of vitamin D per kg.<br />

===Metastatic Calcification===

===Metastatic Calcification===

This condition is caused by an imbalance between calcium, phosphrous and vitamin D. Metastatic calcification is mainly seen in males in which they exhibit joint stiffness, poor weight gain and eventually death.  There will also be calcium deposits in skeletal muscle and other organs.<br />

This condition is caused by an imbalance between calcium, phosphrous and vitamin D. Metastatic calcification is mainly seen in males in which they exhibit joint stiffness, poor weight gain and eventually death.  <br />

Macroscopic pathology will show mineralisation/calcification of the heart, blood vessels, stomach, colon, kidneys and lungs.<br />

The diet should have a calcium:phosphorus ratio of 1:5 and the same vitamin D level as above. <br />

The diet should have a calcium:phosphorus ratio of 1:5 and the same vitamin D level as above. <br />

===Scurvy===

===Scurvy===

This condition is due to a deficiency of vitamin C where an adult guinea pig requires 10-30mg per day. Haemorrhages will be found around joints and on all serosal surfaces. Clinical signs range from an unsteady gait, painful locomotion and bleeding gums.<br />

This condition is due to a deficiency of vitamin C where an adult guinea pig requires 10-30mg per day.  

Macroscopic pathology will include haemorrhages around joints and on all serosal surfaces, particularly around fascial and articular cartilages. Petechial and ecchymotic bleeding may be seen  on the periosteum, muscle and gingiva.<br />

 

===Osteoarthritis===

===Osteoarthritis===

In guinea pigs the most commonly affected joint is the stifle and clinical symptoms can range from lameness to weight loss in guinea pigs of 9 months and older.<br />

In guinea pigs the most commonly affected joint is the stifle and clinical symptoms can range from lameness to weight loss in guinea pigs of 9 months and older.<br />

===Cervical Lymphadenitis===

===Cervical Lymphadenitis===

Steptococcus zooepidemicus is normally present in the conjunctiva as a commensal organism. If this organism gains access to the cervical lymph nodes they can become pathogenic and in some cases death can occur due to septicaemia. Infection will cause the lymph nodes to swell. Stress has been shown to increase susceptibility. <br />

Steptococcus zooepidemicus is normally present in the conjunctiva as a commensal organism. If this organism gains access to the cervical lymph nodes they can become pathogenic and in some cases death can occur due to septicaemia. Infection will cause the lymph nodes to swell. Stress has been shown to increase susceptibility. <br />

===Wry Neck===

===Wry Neck===

This condition affects only newborn guinea pigs in which they have a degree of torticollis and may be found lying on their backs to suckle due to their inability to maintain a suitable head posture. This condition is hereditary.<br />

This condition affects only newborn guinea pigs in which they have a degree of torticollis and may be found lying on their backs to suckle due to their inability to maintain a suitable head posture. This condition is hereditary.<br />

===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 />