Diseases of Domestic Guinea Pigs

Virginia C. G. Richardson

• Publisher: Wiley-Blackwell
• Year: 2011
• Print ISBN: 9780632052097
• eBook ISBN: 9781118250341
• Edition: 2
• Topic: Medicine
• Subtopic: Veterinary Medicine

This book provides a comprehensive text covering all aspects of guinea pig medicine. This updated edition will be of value to veterinary surgeons and students, veterinary nurses, breeders and all those working in the animal care industry. Written in note form the book assists in the formulation of a diagnostic plan when the practitioner is faced with a sick animal. Sections on clinical signs, diagnoses and treatments, allow rapid reference in successive chapters on the reproductive, digestive, respiratory, musculoskeletal and urinary systems, the skin, head and neck, nervous system and husbandry.

All the latest drug information has been included and full details of dose rates, contraindications and components of the proprietary preparations are listed in chapter 11. A new chapter has been written providing information on herbal and homeopathic remedies.

1

THE SKIN

The skin of the guinea pig normally provides a resistant barrier against infection. However, there are many factors which lower this resistance and predispose the guinea pig to the development of skin disease. One of the most common findings is an increased incidence of skin problems in guinea pigs fed on marginal diets, especially if these diets have a low vitamin C content. The feeding of stale dried food will cause such a problem as the vitamin C content deteriorates rapidly 6–9 weeks after milling. Rabbit food is also too low in vitamin C to be used as a staple diet for guinea pigs. If guinea pigs are fed a rabbit food their diet must be supplemented with daily greenfood and carrots, and if necessary with vitamin C in their drinking water.

Other important stresses which predispose the guinea pig to the development of skin conditions are overheating, pregnancy and showing.

SPECIFIC SKIN CONDITIONS

Ringworm

Clinical signs: Areas of alopecia, usually accompanied by varying degrees of seborrhoea. The lesions are often found around the face but may spread to the rest of the body. The affected hair can be readily plucked from its follicles. The condition may or may not be pruritic. There may also be accompanying lesions on the owner.

Diagnosis: The causal agent is usually Tricophyton mentagrophytes or Microsporum gypseum so it will not fluoresce under ultraviolet light (Wood’s lamp). Direct microscopic examination of hair from the lesion together with culture on Sabouraud’s medium will confirm the diagnosis.

Treatment: Griseofulvin (Tx 18) at a dose of 25mg/kg (approximately 0.75 mg/kg of feed) for 4–6 weeks is generally effective. If griseofulvin is used to treat an individual animal it is best given orally on a daily basis, and the approximate dose is one-eighth of a tablet daily, which can be given mixed with an unsaturated fatty acid supplement (e.g. 0.5 ml Norderm, Norden Laboratories). Care must be taken when using griseofulvin in very young animals (under 3 months) as a high incidence of infant mortality has been reported in association with the use of this anti-fungal preparation in one colony. Griseofulvin should also not be administered to pregnant sows.

Alternatively tolnaftate 1% (Tx 19, Tinaderm-M cream) can be applied to the lesions twice daily until they resolve.

Cases with severe accompanying seborrhoea will benefit from the use of an anti-fungal shampoo, e.g. hexetidine 0.5% (Tx 40). This shampoo is most effective if it is left in contact with the skin for some time (1–2 hours in severely affected cases) before rinsing. Alternatively the guinea pig can be dipped in a 0.2% solution of enilconazole (Tx 17).

A diet with good vitamin C content must be fed at the same time as treating with any anti-fungal agent to enable the affected guinea pig to make a full recovery.

Other mycoses

Clinical signs: Guinea pigs may suffer from a range of other mycotic infections, and the clinical signs may vary from mild skin changes indistinguishable from mange in its early stages, to very severe seborrhoea with accompanying systemic signs including cystitis, pneumonia, convulsions and reproductive disorders.

Diagnosis: Microscopic examination of the hair and culture on Sabour-aud’s medium.

Cases which are suggestive of mycotic infection are those which do not respond to the standard anti-parasitic treatment.

Treatment: Griseofulvin (as for ringworm) and the use of an anti-fungal shampoo, e.g. 0.5% hexetidine (Tx 40). The shampoo should be left in contact with the skin for as long as possible (up to 2 hours) before rinsing. The effectiveness of the treatment will be increased if all the affected hairs are plucked from the guinea pig’s body as this will remove a high percentage of the fungal spores. This treatment can be repeated every 3–4 days as necessary.

The use of amphotericin B has been reported in those cases exhibiting severe systemic involvement.

Mange

This condition may also be called ‘sellnick’ or ‘rat mange’. It refers to the condition produced by Trixacarus caviae, a sarcoptiform mite.

Clinical signs: These usually occur 3–5 weeks after infection, although they may remain inapparent for considerable periods. The lesions are seen mainly around the head and shoulders and over the dorsum, but may spread further to affect the whole guinea pig. The hair comes out and the skin is seborrhoeic and usually intensely pruritic. There may also be many open sores due to self-trauma. If the sow is in-pig and is quite severely affected she may resorb or abort her litter. If her young are born normally they will become infected immediately.

In cases where the pruritus is severe the guinea pig may also exhibit nervous signs, and in extreme cases may actually have fits.

Diagnosis: Microscopic examination of skin scrapings.

Treatment: Numerous treatments have been advocated. Probably the most effective is ivermectin (Tx 31), but as this is not licensed for guinea pigs it should be used with care. The dose is 200 µg/kg and this can be repeated at 10–14-day intervals if necessary. The Ivomec injection (Merial Animal Health Ltd.) is the most convenient preparation to use (0.02 ml/kg) and it can be diluted 1:10 to produce a dose of 0.2 ml which should be administered subcutaneously. Alternatively this same drug has been administered orally with the same effect. Up to 2 drops from a 2 ml syringe (equivalent to 400 µg) can be given with no side-effects. Although the oral absorption of ivermectin has not been evaluated, treatment in this way seems to be effective.

Trials using ivermectin, performed at the Cambridge Cavy Trust have shown that greater doses of this drug can be used without any adverse effects. Their recommendations are as follows:

• Age 3 weeks to 3 months: 0.1 ml (1000 µg) by subcutaneous injection. Oral dosing is not recommended.
• Age 3 months to adult: 0.2 ml by subcutaneous injection. One drop given orally.

These treatments can be repeated after an interval of 10–14 days.

Other preparations which can be used include sprays containing pyrethrum extract (e.g. Johnson’s Anti-Pest Insect spray). Seleen (Tx 30) can be used as a shampoo.

If this or any other skin condition is accompanied by intense pruritus, this can be controlled by an injection of a steroid preparation (Tx 37 and 38). Creams containing local anaesthetic agents can also be used on the lesions to prevent self-trauma.

Self-trauma can also be limited if the hind feet are lightly dressed, or alternatively the worst sores can be protected with a loose body bandage.

If nervous signs are present, diazepam (Tx 44) at a dose of 1–2 mg/kg can be given intramuscularly to help control these. However, if the symptoms are as severe as this, euthanasia may have to be considered.

An alternative treatment for controlling any seizures is primidone (Mysoline Tx 42).

If a pregnant sow is badly affected she should be treated. The slight risks incurred by handling a gravid sow are better than the consequences of leaving her untreated. Ivermectin has been administered during pregnancy without obvious side effects, and dosing is a less stressful procedure than bathing or dipping.

If the problem is a recurrent one, treatment is more effective if it is varied. If the same preparation is used repeatedly it is not unknown for some mites to develop resistance to the treatment and the condition then becomes more persistent.

The environment should also be treated. The hutch can be sprayed with an environmental flea spray.

Comment: Trixacarus caviae is a burrowing mite, and transmission can be via direct or indirect contact. The female burrows into the skin and lays her eggs in the tunnels she creates. Multiple larvae then hatch out in these tunnels, metamorphose through two nymph stages and then develop into adults. The life cycle takes 14 days. The mite eggs can remain dormant for a period of 1–21 months, and can exist all this time in the host. Stresses such as malnutrition, overcrowding, poor ventilation, extreme heat and pregnancy predispose to this condition.

Prevention: If there is a problem in the caviary all individuals can be treated with ivermectin (Tx 31) given orally in order to eradicate any sub-clinical disease.

Demodex

Clinical signs: Areas of alopecia, especially around the head and forelegs. The condition may or may not be pruritic.

Diagnosis: Microscopic examination of skin scrapings.

Treatment: Injection of a high dose of ivermectin (Tx 31) which may need to be repeated two or three times at fortnightly intervals.

Lice

Clinical signs: This condition need not be pruritic, and the lice can often be seen in the fur. ‘Static lice’ refers to the eggs of the lice which are seen as black or white specks sticking to the hair, especially around the neck and ears and on the ventral abdomen. ‘Running lice’ refers to the adult forms which are visible to the naked eye.

In some cases the term static lice is used to describe the fur mite Chirodiscoides caviae (see below).

Diagnosis: Microscopic examination of hair and skin scrapings.

Treatment: A spray containing pyrethrum extract (e.g. Johnson’s Anti-Pest Insect spray). Seleen (Tx 30) will also be effective, and treatment can be repeated at weekly intervals. A more old-fashioned remedy was to use oil of sassafras, but unfortunately this oil is no longer readily obtainable. It can be worked gently into the coat avoiding the eyes and genitals, and left to evaporate. It will kill the lice and their eggs and leave the coat in a glossy condition. The treatment can be repeated after 14 days. Alternatively, a human head lice preparation containing malathion can be used. The spirit based preparation can be rubbed into the coat, and left for at least 10 minutes before combing with a fine comb. The guinea pig should be rinsed in warm water and dried.

Comment: Causal agents are varied. Infestations with Gyropus ovalis, Trimenopen jenningsi and Gliricola porcelli have been recorded.

Gliricola porcelli is the most common. The adults are yellow-grey in colour and are up to 1.5 mm long. Gyropus ovalis are similar, but are slightly smaller and they have a less rounded head. Trimenopen jenningsi is thought to be of little pathogenic significance unless the guinea pig is stressed.

Fur mite

These mites (Chirodiscoides caviae) are 0.5 mm long and are often found joined in pairs. They appear to produce no clinical signs even when the guinea pig is heavily infested. They will be removed with any of the ecto-parasitic treatments recommended above for mange and lice.

Prevention: The load of ectoparasites can be reduced by hanging a Vapona sticky strip (containing dichlorvos) in the environment for a 48-hour period once a week. Nuvan Top, a spray containing dichlorvos for use in cats and dogs, should not be used on guinea pigs. The active ingredients are powerful cholinesterase inhibitors and toxicity is likely to develop. If Nuvan Top has been used the antidote is atropine sulphate which should be administered at a dose of 0.1 mg/kg given intraperitoneal.

Rabbit fur mite

The rabbit fur mite Psoroptes cuniculi has been isolated from skin lesions in a guinea pig. The ears, face, underbody and hind legs were affected by a crusting and scaling dermatitis which was extremely pruritic. Treatment with three doses of ivermectin at 10 day intervals was effective.

‘Broken back^’

Clinical sign: A single area of hair loss in the centre of the back which may become an open sore; if left will scab over. This condition is often mistakenly assumed to be mange. It seems to be associated with stresses such as showing or pregnancy.

Treatment: Bathe the sore with a dilute saline solution (Tx 52) and dry. Dermisol cream or Vetsovate (Tx 23 or 26) can be applied topically up to three times daily. However, the condition will resolve with bathing only. Once the lesion is healed the affected skin may be fairly dry and this can be conditioned by topical application of cod-liver oil or evening primrose oil.

Comment: This condition affects lighter coloured guinea pigs most frequently, and it is thought to occur as a result of the guinea pig ‘overheating’. Barley is a particularly ‘overheating food’ as is flaked maize, and these should be removed from the diet. An excess of rabbit pellets has also been implicated as a cause of overheating. The problem is seen at its worst in the heat of the summer.

‘Post-natal sores’

This condition is similar to ‘broken back’ and develops in some sows after parturition as a sore in the centre of the back, and it can be treated in the same manner. It is thought to be due to a mineral and protein deficiency.

In late pregnancy sows prone to developing this condition can be given some Bemax as a supplement sprinkled on their food. Alternatively they can be given a bread and milk mash to which extra soya flour has been added to provide supplementary protein. A couple of drops of Vitapet daily as a source of polyunsaturated fatty acids may also be beneficial. This condition will also respond if 1–2 drops of Abidec (Tx 45), a vitamin preparation, are given orally once a day.

Comment: This condition also occurs in sows during gestation and is also likely to be due to a mineral and protein deficiency. The treatment is the same as for ‘broken back’.

Skin lesions immediately after parturition

Clinical signs: Sows develop raw patches on their rumps and ventral abdomen soon after parturition.

Comment: This condition is more prevalent if the sow has had a long and difficult labour. She becomes caked in blood and uterine fluids because she is too tired to clean herself immediately after the birth. This then begins to irritate her and she tears the hair out from the affected area; the lesions are therefore due to self-trauma.

There is also a possible inherited tendency towards developing this condition.

Treatment: It is important to check the sow after the birth and if necessary clean her with a dilute solution of Savlon (Tx 51).

If raw patches do develop they must be cleaned gently and towelled dry. Antibiotic creams should be used with extreme caution as there is a real risk that they will be ingested by the youngsters whilst suckling and therefore these preparations are probably best avoided. If the sores are weeping, calamine lotion can be applied and this should dry up the lesions in 24 hours with less risk to the youngsters. Some sources suggest the application of cod-liver oil to the bald areas to help them heal, but this should be avoided due to the risk of vitamin D overdose if ingested by the suckling youngsters.

Seborrhoea

Seborrhoea and the presence of excess scurf in the coat may be a symptom of many different conditions, notably mange, ringworm and other mycotic infections, and chronic liver disorders. The presence of this scurf is in itself intensely pruritic irrespective of the causal agent.

Treatment: As well as treating the underlying cause, the scurf can be removed by using a tar-based shampoo, e.g. Tarlite (Tx 43). Shampooing can be repeated at weekly intervals and the resultant improvement will bring great relief to the affected guinea pig.

If it is difficult to determine whether the initiating cause is parasitic or fungal in origin it is advisable to use Seleen (Tx 30) which has both antiparasitic and antifungal properties.

Alopecia

During pregnancy

Some sows lose their hair during pregnancy. The symptoms begin in middle to late pregnancy and the hair just begins to fall out. There is no accompanying pruritus. If a sow has experienced this condition once she is likely to do so during subsequent pregnancies, and the condition is also worse in older and frequently bred females.

Treatment: Vitamin B supplementation has been advocated, either in the form of a weekly multivitamin injection or as daily drops of an oral preparation. However, the condition will resolve slowly after parturition without treatment.

Hormonal

A bilateral symmetrical alopecia may be seen in older sows associated with ovarian cysts. These cysts may reach 2–3 cm in diameter and are readily identified during abdominal palpation.

Treatment: Ovariohysterectomy. Alternatively, the cysts can be drained via percutaneous needle aspiration.

Post-natal

After parturition some sows may lose most of their coat. The hair is lost bilaterally from the flanks and ventral abdomen.

Occasionally the young may actually be responsible for pulling hair from their dams.

Treatment: None is required. This condition is thought to be hormonal in origin and will correct itself once the sow stops nursing her litter.

Liver disease

Clinical signs: The hair cover is sparse and the skin may be thickened. There is often accompanying seborrhoea. Pruritus is not usually a feature unless the seborrhoea is severe. The guinea pig may twitch frequently.

Severe, untreated mycosis will also present with similar clinical signs.

Treatment: If parasitic and fungal causes are eliminated then this condition is often a sign of underlying liver disease. If the seborrhoea is intense, a tar and sulphur based shampoo (Tarlite Tx 43) is very effective and this can be repeated weekly as necessary. Other treatment is supportive, and should include a vitamin and polyunsaturated fatty acid supplement, e.g. Vitapet. However, in severe cases exhibiting nervous signs the prognosis is poor.

Scurvy

One of the manifestations of this condition is hair loss, usually accompanied by the other symptoms of weight loss, lameness, weakness and bleeding from the gums.

Treatment: Vitamin C at a dose of l00 mg/kg, preferably given orally in drop form, until the condition resolves.

Comment: In any skin condition the provision of adequate vitamin C is of paramount importance. Plenty of this vitamin is to be found in fresh greens, carrots and beetroot. Rosehip syrup is another useful source of vitamin C. (For further details about this vitamin refer to Chapter 9.)

Hair loss at weaning

Young guinea pigs may get a thin hair coa...

Table of contents

• COVER
• SERIES
• TITLE PAGE
• COPYRIGHT
• PREFACE
• 1: THE SKIN
• 2: THE REPRODUCTIVE SYSTEM
• 3: THE URINARY SYSTEM
• 4: THE RESPIRATORY SYSTEM
• 5: THE DIGESTIVE SYSTEM
• 6: THE MUSCULOSKELETAL SYSTEM
• 7: THE HEAD AND NECK
• 8: BEHAVIOUR AND THE CENTRAL NERVOUS SYSTEM
• 9: HUSBANDRY
• 10: ANAESTHETICS AND SURGICAL PREPARATIONS
• 11: TREATMENTS
• 12: ALTERNATIVE THERAPIES
• 13: ZOONOTIC ASPECTS
• APPENDIX 1: MISCELLANEOUS PHYSIOLOGICAL DATA
• APPENDIX 2: SUMMARY OF HERBAL AND HOMEOPATHIC REMEDIES AND THEIR USES
• FURTHER READING
• INDEX