New Guinea Pig Problems: Sexing & Pregnancy; URI, Ringworm & Parasites; Vet Checks & Customer Rights

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Staff member
Mar 10, 2009
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Coventry UK
In order to nip any major problems in the bud as much as possible right at the start, there are some things you should do with all new arrivals.

- double-checking the gender
- when to quarantine new companions?
- vet checks and when you can reclaim vet fees from a pet shop
- list of the most common illnesses in new guinea pigs
- list of guinea pig specific parasites

Always double-check the gender upon arrival!

Mis-sexing especially babies is sadly still very common. Please always check the gender of any new guinea pigs yourself upon arrival and do not just rely on staff or breeders, or even guessing vets!

Our illustrated sexing link for guinea pigs of all ages, including babies and neutered boars: Sexing Guide

If you struggle with sexing, please open a thread in our Sexing section (which is only visible to registered members). Please note that we will still ask you to check how the inside of the slit looks, as that is the only way you'll ever 100% clarity. Be aware that we cannot see more than you from fuzzy and badly lit pictures than you.

Mis-sexing and not separating any male pups at 3 weeks of age when they become sexually active can lead to pregnancies. Even if you have been sold two sows, one or both of them can be pregnant if the impregnation has happened at the commercial supply breeders, the transport to the various shop branches or in the shop itself.
If you suspect a pregnancy, please open a support thread in our pregnancy section, which is only visible to registered members after they have signed up to our strictly enforced no breeding forum policy.
PS: The earliest sows can give birth is ca. 14-16 weeks of age. They won't show before they are ca. 11-14 weeks old.

When is a quarantine necessary?
If you have already got guinea pigs and your new arrival has not undergone a mandatory quarantine in a good standard rescue, quarantining is strongly recommended.

If you bring home babies under 12 weeks, please waive a quarantine as their need for companionship is too desperate. You will need to treat all piggies in contact if there is an infectious illness/parasite infestation.
Quarantine also does not apply for acute pining freshly bereaved piggies of yours (not eating/drinking and staring at the wall), again because the need for instant company is paramount.

If you get guinea pigs from a home where you know for sure that they have been well cared for and haven't been exposed to neglect/sub-standard care, a quarantine is also usually not necessary.
If you have any doubts whatsoever, please have them vet checked and err on the side of caution!
Importance Of Quarantine

Please note that guinea pigs are group animals that should not be kept as singles.

Vet health check upon arrival
We recommend to have all new guinea pigs vet checked. You cannot reclaim the cost of a routine health check at the vets.
A vet check is always necessary if you acquire second-hand guinea pigs from free-ads, privately or from rescues/shelters without a mandatory quarantine.

Be aware that many infectious issues like ringworm/fungal or mites take 10-14 days between in infection and outbreak. In the case of ringworm, this can happen even later if ringworm spores are carried on the coat, but have not come into contact with the skin.

Please be aware that vet cost are going to make the largest budget post in any pet's life and that you need to take out either exotics pet insurance (not available in many countries) or you need to save up on a weekly or monthly basis as an integral part of their normal living cost.
Emergencies can happen at any time during their lives. Guinea pigs can go downhill very quickly; you do not have the time to argue with your family for days! Serious illness and operations can quickly climb into the hundreds of pounds/dollars.
The right to be free of pain and to not suffer unnecessarily is one of the basic rights for any domestic animals.

Recommended UK vets: Recommended Guinea Pig Vets
Recommended exotics vets in some other countries: Guinea Lynx :: GL's Vet List

Reclaiming any vet treatment for new pet shop guinea pigs
If there are health problems during the weeks after a shop sale, you can reclaim any vet cost from the shop as exposure and infection must have happened at the shop.
UK chain shops generally acknowledge any vet bills that are presented together with the sales receipt and dated within the first 2-3 weeks while US chain shops do so within the first month.

You can also reclaim any arising vet cost from a mis-sexed pair or buying an already pregnant sow, as well as claim support (cage, feeding) for any unplanned babies as part of your customer rights for having been sold faulty ware.

Please refuse to sell your guinea pigs back to the shop with the option of buying them again after any successful treatment! This means that you lose any legal rights to your guinea pigs, including the right to raise a complaint if your guinea pig dies from ineffective cheap treatment since you have no control or no say.


Staff member
Mar 10, 2009
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Coventry UK
Most common infectious illnesses in new shop or breeder guinea pigs
The immune system in baby guinea pigs is still under construction when they are ripped away from the families, have their lives upturned several times and are kept at very close quarters in shops, especially in the holding area behind the shop front. Weak immune system, stress, close proximity and exposure are the ideal conditions for bugs to be picked up and spread around.
The only place you can avoid this is by adopting from a good standard guinea pig rescue with a mandatory quarantine, a pregnancy watch for all incoming sows and a health check before any guinea pigs are being put up for adoptions. Since many sows coming into rescue are pregnant, there are often babies to be found in rescue, too. We can provide lists for recommended safe rescues in several countries if wished.

Ringworm (fungal skin infection)
Highly infectious and transmittable to humans and other pets. Requires scrupulous hygiene and a vet strength disinfectant. Please see a vet promptly and ask for a preferably oral systemic fungal treatment, which is prescription-only. If not available, ask for an efficient dip.

Typically first noticed as little crusty, bloody or bald patches on the head and ears. In later stages patches can appear all over the body as they are spread around by shed ringworm spores.
If ringworm has been diagnosed, please follow the hygiene tips in our guide in order to get on top it once and for all.
Ringworm: Hygiene And Pictures

Do not cream; it will not prevent ringworm from spreading further as you do not reach the affected area around the bald spot, catch all spores and prevent other areas from getting infected!
Never treat skin problems on spec before seeing a vet. It is the same as wiping a crime scene. Your vet will be grateful if you leave them plenty of evidence for an informed diagnosis and allow them to start immediately with good quality treatment.

Respiratory tract infection (URI)
Respiratory infections in guinea pigs are bacterial and NOT viral like human flu. They require a full course of antibiotics.
If not treated at all, wrongly or undertreated, URI can kill or cause permanent damage.
See a vet promptly; the sooner treatment kicks in, the greater the chances of a smooth and quick recovery!

Typical symptoms in order of development: very frequent and persistent sneezing (much more than 5 times a day or a one-off sneezing fit), crackly breathing, yellow/greenish gunky eyes, coughing, loss of appetite, apathy.
Guinea Lynx :: URI

Any piggy that is lethargic and not eating much or not at all is a life and death emergency and needs to see a vet ASAP at any time fo the day or night! Please make a vet appointment first (if possible) before opening a support thread in our Health/Illness section.
Step in with syringe feeding fibre and water as soon as you notice your piggy not being quite well. Over 80% of the food intake is unlimited hay, so nibbling on a leaf of lettuce is just not enough to keep a piggy alive! The need to breathe comes before the need to drink and only thirdly the need to eat.
A guinea pig that is struggling to breathe will have no appetite and grow weak very quickly. The guts will slow down and then close down. Feeding lukewarm water doesn't contain any calories and won't save a guinea pig that has stopped eating! Your care is vital to keep your piggy alive until the antibiotic is kicking in, breathing has freed up and the appetite has come back. This can take several days.
Not Eating, Weight Loss And The Importance Of Syringe Feeding Fibre
Complete Syringe Feeding Guide

Persistent sneezing without any other more advanced symptoms developing can be caused by hay dust, pollen allergy, dusty bedding (please no pine shavings!), dry air from air conditioning or radiator heat, perfumes from air fresheners, scented human body care products and perfumes as well as scent sticks. Please never smoke in a room with guinea pigs! Allergies and sensitivities can only be diagnosed by default after a URI has been exlcuded by a vet.

Please never place shop guinea pigs in an unprotected and unheated outdoors hutch during the time frosts can happen. Guinea pigs need to be treated like tender plants!
They need to spend the winter months especially in frost areas under cover and with extra protection.
URI can result if your guinea pigs are exposed to wide temperature swings without being acclimatised.

Guinea pig specific parasites

Mange mites
(trixacarus caviae: invisible mites burrowing their eggs in the skin)
Mange mites will kill slowly and agonisingly if left untreated or undertreated!

Mange mites typically appear in the small of the back as a v-shaped bald patch but they can manifest in other parts of the body, too. Very intense, frequent scratching and biting of the skin; real discomfort/refusal to being held; fitting in advanced stages.
Please note that not all fungal infections and mites manifest in textbook form and that they can look very similar in the early stages, especially if they do not happen in a classic place.

Please disinfect the cage and any contents with a vet-grade disinfectant. Change the hay supply.
No guinea pig skin parasite can survive on humans. They are species specific. Mange mites can in rare cases affect humans shortly.

Please do not treat on spec with low dosed shop products that will only suppress the symptoms temporarily but won't cure. See a vet for a diagnosis and a good quality ivermectin or selamectin-based treatment; it requires at least 3 applications at the product specific interval to make sure that they are not coming back.

Hay/fur mites
(chirodiscoides caviae: invisible mites that fix their tiny egg cases to the hairs first around the back end but in advanced cases all over the body).
Eventually small bald or scurfy patches on the body if present for a longer time. The least harmful of the three species specific skin parasites that guinea pigs have.

Hay mites usually arrive in hay bags. They have become much more common in recent years due to imported branded hay from abroad. Please get rid of any hay, disinfect the cage and hard furnishings and wash any fabrics at a higher temperature (60 C/ 140 F).

The visible egg cases look like somebody has turned a pepper mill over the back end of your guinea pig; the eggs are tiny nodules like beads strung up on a hair if you feel for them. Always check the deeper layers of the hairs at the bum end for hay mite eggs during the regular weekly health check and weigh-in.
Treatment is the same as for mange mites. With major infestations it can be helpful to give your piggy a very short haircut or shave to remove as many eggs as possible mechanically; the hairs will grow back even in short haired guinea pigs. Throw away the hay (which they usually come in) and disinfect the cage with a vet strength deep cleaning product.

In very persistent cases, a two-pronged approach with ivermectin and a course of medicated lice shampoo can help. Please ask your vet for a suitable product. Lice'n'easy shampoo from Gorgeous Guineas may also help but is not necessarily able to clean out an infestation on its own.

Guinea pig lice are small pale things crawling around the coat. They live off the blood of guinea pigs. Treatment is with a vet strength ivermectin/selamectin product. Untreated lice in weakened guinea pigs can kill!

Lice are occasionally found in backyard/farm breeder piggies that are not receiving any vet care. Please be aware that any breeder piggies with bald patches need to see a vet for treatment promptly (parasitic and/or fungal). Healthy guinea pigs only have symmetrical bald patches behind the ears!

More information on guinea pig parasites via this link here: Guinea Lynx :: Parasites
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