Guinea Pig Respiratory Infection: Why Quiet and Off Food Is a Chest Sign

Quick answer

Pneumonia is one of the main killers of pet guinea pigs, and it almost never announces itself with coughing. What owners see is a guinea pig that has gone quiet, stopped coming out for food and lost a little weight, which is exactly what every other guinea pig illness looks like.

Forget about taking a temperature. A guinea pig that is seriously ill is often cold rather than hot, home thermometers are unreliable and stressful in this species, and the numbers that genuinely help are weight and resting breathing rate, both of which you can record at home in a minute.

A guinea pig that is sitting apart from the others with its coat fluffed has usually been unwell for longer than you think.

• Weight and resting breathing rate are the two home measurements worth taking. Temperature is not.
• Crusty discharge on the front paws is often the first visible sign, because that is what a guinea pig wipes its nose with.
• Never house guinea pigs with rabbits. Rabbits commonly carry the bacterium that causes guinea pig pneumonia without being ill themselves.
• Ammonia from soiled bedding damages the airway lining and lets infection take hold.
• Several antibiotics that are routine in other species are fatal to guinea pigs.

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Open-mouth breathing in a guinea pig is a terminal-stage sign and needs emergency care immediately.

Guinea pigs breathe through the nose and do not open the mouth to breathe unless they are in severe respiratory failure or their airway is blocked. By the time this appears, the reserve is gone. Handle the animal as little as possible, transport it in a carrier without chasing it, keep it cool rather than warm if it has been in a hot room, and go straight to a vet. Do not attempt steam, nebulisation or any home treatment at this stage.
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Decide in 60 seconds

Why the lungs fail first

Guinea pigs have relatively small lungs for their body size and a limited ability to compensate when part of the lung is out of action. They are also prey animals, so they conceal illness until concealment stops working. Those two facts together explain why so many cases arrive at a vet already severe.

The infection itself usually starts as bacteria colonising the upper airway. The lining of that airway is covered in cilia, microscopic hairs that beat in a coordinated wave and sweep mucus, dust and organisms upward and out. Anything that damages the cilia removes the guinea pig's main defence.

Three things damage them, and all three are husbandry.

Ammonia.

Urine soaking into bedding is broken down by bacteria into ammonia gas, which sits low in the enclosure exactly where the guinea pig's nose is. Ammonia paralyses and destroys the cilia. In a covered enclosure with poor airflow, the concentration at floor level can be far higher than anything you notice standing over it.

Dust.

Fine dust from low-grade sawdust bedding or dusty hay is inhaled continuously and provokes chronic irritation.

Aromatic softwood shavings.

Cedar, and untreated pine, release volatile compounds that irritate the airway lining directly.

On top of a damaged airway, the organisms that cause disease are frequently already in the house. Bordetella bronchiseptica is carried without symptoms by many rabbits, and also by dogs and cats. A guinea pig housed with a rabbit, or living in a home with a dog with a mild cough, is exposed continuously. Streptococcus species are also common, and one of them causes both pneumonia and the abscessed lymph nodes in the neck that owners call lumps.

Vitamin C sits underneath everything. Guinea pigs, like people, cannot synthesise it. A deficient guinea pig heals badly, mounts a weaker immune response and has more fragile tissues, so a marginal diet turns a survivable infection into a fatal one.

What early illness looks like

A weekly weight written down is the earliest warning system a guinea pig owner has, and it costs a minute.

Behaviour before anything else.

Not coming out for vegetables. Sitting apart from the group. Coat held fluffed rather than sleek. Reluctance to move. Sleeping in a hunched position rather than stretched out.

Weight.

Falling before any visible sign. Weigh weekly on a kitchen scale, at the same time of day, and write it down. A guinea pig that has lost weight across two weeks is unwell even if you cannot see what is wrong.

Breathing.

Count breaths over a full minute while the animal is at rest and undisturbed, ideally watching from a distance rather than holding it. Do this several times while your guinea pigs are healthy and write the numbers down, because your own animal's normal figure is more useful than any published range. An increase over that personal baseline, or any change in effort, is the sign.

Discharge.

Look at the nostrils, the corners of the eyes, and the inside of the front paws. Guinea pigs wipe their faces with their forelimbs, so crusted or matted fur there is often visible before the nose itself looks wet.

Sound.

Hold the guinea pig gently against your ear, or listen closely while it is settled. Clicking, whistling, crackling or a wet sound with each breath is abnormal. Normal guinea pig breathing is almost silent.

Posture in advanced disease.

Head and neck extended forward, elbows pushed away from the chest, and an exaggerated movement of the abdomen with each breath. This is an animal maximising its airway and it is an emergency.

What else looks the same

A quiet, hunched guinea pig that is off its food is one of the least specific presentations in small animal practice, which is why an examination matters more than a guess.

Dental disease. Painful cheek teeth stop hay intake first. Look for drooling, a wet chin, food dropped half-chewed, and a preference for soft foods.

Gut stasis and bloat. Reduced or absent droppings, a tense or distended abdomen, teeth grinding.

Bladder stones and cystitis. Straining, crying while urinating, blood in the urine, a hunched posture over the litter area.

Ovarian cysts. Common in unspayed sows. Hair loss along the flanks, a swollen abdomen, changed behaviour towards cagemates.

Pododermatitis. Sore feet make an animal reluctant to move, which reads as lethargy. Turn the animal over and look at the undersides of all four feet.

Heat stress. Flat out, panting, hot to the touch, often after a warm afternoon. This is hyperthermia, not fever, and it is cooled rather than treated with antibiotics.

Vitamin C deficiency. Reluctance to move because joints hurt, a rough coat, poor healing, bleeding gums.

Neck lumps. Firm swellings under the jaw from abscessed lymph nodes.

Heart disease. Increased breathing rate and exercise intolerance, sometimes with a cough, in older animals.

The overlap is the point. A guinea pig that is quiet and off food needs an examination that covers the chest, the mouth, the abdomen, the feet and the urinary tract, because guessing wrongly costs days that this species does not have.

Getting it treated

Treatment is veterinary and time-critical. Expect the vet to listen to the chest, take radiographs to see how much lung is involved, and possibly culture discharge to identify the organism and choose the right drug.

Antibiotic choice is not a formality in this species. Several classes that are routine in dogs, cats and people destroy the guinea pig's gut flora and cause fatal dysbiosis, so a practice that sees guinea pigs regularly will pick from a much narrower list. Never give leftover medication from another animal, and never assume that a drug that helped a rabbit is safe.

Supportive care usually matters as much as the antibiotic. That includes fluids, pain relief, vitamin C, and assisted feeding with a fibre-based recovery formula, because a guinea pig that stops eating develops gut stasis on top of pneumonia and the two together are much harder to survive.

Nebulisation, where medication or saline is delivered as a fine mist, is genuinely useful in respiratory disease and some owners are shown how to do it at home. Do it only with equipment and instructions from your vet. A steamy bathroom is not a substitute and risks heat stress in a species that overheats easily.

Isolate an affected guinea pig from any that are not showing signs, but understand that by the time one is ill the others have already been exposed. Tell the vet how many animals are in the group.

Clear eyes, a dry nose and a smooth coat is the baseline. Photograph it in health so you have something to compare against.

Preventing it

Ventilation without draughts.

Air needs to move through the enclosure. Solid-sided tanks and covered hutches trap ammonia. At the same time, a guinea pig sitting in a direct draught from a window or a door is chilled and stressed. Aim for a room with air movement and an enclosure that is open at the top.

Spot clean daily, change fully often.

The soiled corner is where the ammonia is. Removing it daily does more than a weekly full change.

Choose low-dust bedding.

Paper-based bedding, fleece over an absorbent layer, or dust-extracted shavings. Avoid cedar, avoid untreated pine, avoid fine dusty sawdust.

Check the hay.

Hay should smell sweet and green and should not produce a cloud when shaken. Mouldy or dusty hay is a direct respiratory insult and a source of fungal spores.

Get vitamin C from food, not water.

Vitamin C in drinking water degrades within hours, changes the taste, and reduces how much a guinea pig drinks, which is the opposite of helpful. Use fresh sources such as bell pepper and leafy greens, a good-quality guinea pig pellet within its shelf life, and if a supplement is needed, a stable tablet or one given directly, on veterinary advice.

Do not house guinea pigs with rabbits.

Beyond the Bordetella risk, rabbits kick and injure guinea pigs, the two species have different dietary needs, and guinea pigs need guinea pig company rather than a substitute.

Quarantine new arrivals.

A separate room, separate equipment, hands washed between, for a period your vet recommends before mixing.

Avoid temperature swings.

Sudden cold, sudden heat, and cars are all stressors that precede outbreaks.

What never to do

Do not give any antibiotic that was not prescribed for this guinea pig by a vet who knows the species.

Do not use a steamy bathroom as treatment, particularly in warm weather.

Do not put vitamin C in the drinking water.

Do not house guinea pigs with rabbits.

Do not use cedar or untreated pine shavings.

Do not attempt home temperature measurement.

Do not delay because there is no cough. Most guinea pigs with pneumonia never cough.

Do not stop antibiotics early because the animal looks better. Relapse after a shortened course is common and harder to treat.

When to get help

Go immediately for open-mouth breathing, an extended neck with elbows held out, blue or grey gums, collapse, or a guinea pig that feels cold and is unresponsive.

Go the same day for any increase in breathing rate or effort, audible chest sounds, nasal or eye discharge, crusting on the front paws, refusal of hay, or a guinea pig sitting fluffed and apart from the group.

Book promptly for repeated sneezing, weight loss over two consecutive weeks, or a group in which more than one animal has become quiet.

Back to eating hay, holding weight and breathing silently is the endpoint, and the husbandry that allowed the infection still needs fixing.

Bring the weight record, your healthy-baseline breathing rate and any video, photographs of the discharge, the bedding and hay type, how many animals are in the group and whether any others are affected, whether there is a rabbit or a dog in the household, the current diet and vitamin C source, and any medication already given. Expect chest auscultation, radiographs, and a full examination of the mouth, abdomen and feet, because the presentation overlaps with several other guinea pig conditions.