After a lizard dies: getting an answer and decontaminating the enclosure

Quick answer

When a lizard dies there are three questions worth answering, and only one of them is about feelings. Why did it die, is the enclosure safe for anything else to live in, and is anything else in the house now at risk.

Most reptile deaths at home are never explained, and the reason is almost always the same: the body was frozen, or thrown away, before anyone asked. If you want an answer, the decisions that make one possible are made in the first few hours.

The next animal inherits whatever this one left behind: the same lamps, the same thermostat, the same wood, and sometimes the same organism.

• Refrigerate the body. Do not freeze it. Freezing destroys the tissue detail a pathologist needs.
• Phone an exotics vet the same day, even if you are unsure whether you want a post-mortem.
• Do not put another lizard into the enclosure until you know what killed the last one.
• If you keep other reptiles, they are the priority now. Separate equipment, and wash hands between enclosures.
• Several reptile diseases survive in wood, substrate and silicone long after the animal has gone.

Decide in 60 seconds

Why the cause matters more than it feels like it should

In the hours after a pet dies, working out why can feel like a cold thing to be doing. It is not, and there are three concrete reasons.

Because the same thing can happen again. If a thermostat failed, the next lizard will meet the same thermostat. If the UVB lamp had stopped emitting useful output while still producing visible light, the next animal will be under the same lamp. Neither of those is visible without being looked for.

Because some causes are still in the room. A husbandry failure is over when it is corrected. An infection is not. Several reptile pathogens persist in substrate, in porous wood, in silicone sealant and in water bowls, and the next animal is placed directly into them.

Because other animals in the house may already be incubating it. If you keep more than one reptile, a death is a warning about the others, and the interval in which testing and separation help is short.

There is also a fourth reason, less clinical but real: the cause is usually not what the owner assumes, and a specific answer is much easier to live with than a vague sense of having done something wrong.

What actually kills captive lizards

Cause of death in captive reptiles clusters into a small number of groups, and the group matters because it determines whether the enclosure is dangerous.

Thermal and environmental failure. A stuck-on heat source cooking an animal, a failed thermostat leaving it cold, a heat mat under glass with no gradient, a heat rock burning the belly, or an enclosure in direct sun turning into an oven. Overheating kills quickly and often leaves an animal found dead in a cool corner. Chronic cold kills slowly through failure to digest, which turns into a gut full of rotting food.

Nutritional and metabolic disease. Metabolic bone disease from inadequate calcium, vitamin D3 or UVB. Gout from chronic dehydration and dietary imbalance. Hepatic lipidosis in overfed animals. Hypovitaminosis A. These are slow, so a post-mortem usually reveals long-standing changes rather than an event.

Obstruction and impaction. Substrate, an oversized food item, or a foreign object. Often preceded by a period of straining and reduced droppings that was not recognised.

Reproductive disease. Egg binding and follicular stasis in females, including in females kept alone, since many species will produce eggs without a male.

Infection. This is the group that matters for the enclosure. Cryptosporidium, adenovirus, Entamoeba invadens, various bacterial septicaemias including Salmonella, and species-specific viruses. Some produce a long wasting course; some kill fast with almost no warning.

Trauma and escape. Falls, crush injuries, attacks by household cats and dogs, and animals lost in a house that then die of cold or dehydration.

Age and organ failure. In an old lizard, kidney disease, liver disease and tumours all occur, and death from old age is a real and acceptable answer.

The overlap between these groups is the practical problem. A lizard weakened by poor temperatures is more likely to succumb to an infection it was carrying quietly. A post-mortem often finds both, and the report is more useful for that.

Getting an answer: what a post-mortem can and cannot tell you

Ask specifically for a post-mortem examination, sometimes called a necropsy. Many general practices will not perform reptile post-mortems themselves but will collect the body and send it to a laboratory or pathologist experienced with reptiles. Ask which route they are using, because a general small-animal pathologist and a reptile pathologist do not return the same quality of answer.

What preserves the answer. Refrigeration, promptly, at ordinary fridge temperature. Wrapped in damp paper towel to stop tissue drying, in a sealed bag. Delivered as soon as possible, because autolysis begins immediately and progresses even in the cold.

What destroys it. Freezing. Leaving the body at room temperature. Waiting several days. Cleaning or disinfecting the body.

What it can find. Gross abnormalities such as burns, impaction, retained eggs, organ enlargement or gout deposits. Histopathology, which is where most infectious diagnoses come from. Bacterial and fungal culture. Specific testing for organisms such as Cryptosporidium or adenovirus, which usually has to be requested rather than assumed.

What it cannot find. A temperature that was wrong three months ago. A lamp that had aged out. A thermostat that failed once. That is why the history you supply matters as much as the tissue.

What it costs you to skip it. Certainty. If you intend to keep reptiles again, an unexplained death in a collection is a permanent unknown that follows you into the next enclosure.

Which causes threaten the next lizard

Furnishings divide cleanly into two groups: things that can be disinfected, and things that have to be thrown away. Wood, cork and used substrate are in the second group.

Sort the possible causes into two piles.

Not transmissible, and therefore not an enclosure problem. Trauma. Old age and organ failure. Egg binding. Nutritional disease. Impaction. Thermal injury. In these cases the enclosure needs correcting, not decontaminating.

Transmissible, and therefore an enclosure problem. Cryptosporidiosis, adenovirus, Entamoeba invadens, bacterial infections including Salmonella, fungal disease, and mites. These persist outside the animal for varying lengths of time and can infect the next occupant.

Two of those deserve particular caution.

Cryptosporidium in reptiles is not the same species that infects mammals, and it is exceptionally hardy. The oocysts resist most routine disinfectants, including household bleach at the concentrations people use for general cleaning. Practically, an enclosure that has held a confirmed case is usually stripped completely, with porous contents discarded rather than treated.

Adenoviruses lack the fatty envelope that makes many viruses easy to kill, so alcohol-based products and mild disinfectants are unreliable against them. They are a well-recognised problem in bearded dragons in particular.

If the cause is unknown, treat the enclosure as if it were in the transmissible pile. That is the whole practical value of the distinction.

Decontaminating an enclosure properly

Everything in here has a decision attached: keep and disinfect, bake or steam, or discard. Porous wood is almost always discard.

The order matters, and each step fails if the one before it was skipped.

Strip everything out. Substrate, water bowl, food dish, hides, branches, plants, thermometer probes, and any decor. Bag the substrate and dispose of it rather than composting it.

Discard what cannot be cleaned. Porous wood, cork bark, natural branches, unsealed stone, sponge, cardboard, and anything with a rough or cracked surface. Organisms sit in the pores where neither scrubbing nor disinfectant reaches. This is the step people resist because the wood was expensive, and it is the step that most often reintroduces the problem.

Clean mechanically before you disinfect. Hot water and detergent, and physical scrubbing, to remove all visible organic matter. Faeces, shed skin, food residue and biofilm all inactivate disinfectants. A disinfectant applied over dirt is a disinfectant applied to dirt.

Then disinfect, and respect the contact time. Choose a product appropriate for the pathogen if you know it, and ask your vet which one, because the right choice for Cryptosporidium is different from the right choice for a bacterial problem. Whatever you use, the surface must stay visibly wet for the full time stated on the label. Spraying and immediately wiping achieves almost nothing.

Rinse thoroughly, then air and dry. Reptiles are sensitive to chemical residues and to fumes, and a poorly rinsed enclosure is its own hazard. Leave it open, dry and ventilated for a good while afterwards.

Use heat where you can. Some items tolerate a dishwasher cycle, boiling water, steam cleaning, or a low oven, and heat reaches places chemicals do not. Check what the item is made of first.

Treat the equipment too. Thermostat probes, thermometer probes, tongs, spray bottles and tweezers all move between enclosures and all carry organisms. Either dedicate a set per enclosure or disinfect between uses.

The equipment audit before the next animal

A death is the moment to check the things that are invisible when they are working.

The thermostat. Test it, and find out what it does when it fails. Some fail off, some fail on, and the second kind kills. Consider a separate failsafe or high-temperature cutout on any heat source that can cook an animal.

The probe placement. A probe touching glass, buried in substrate or sitting in the wrong zone reports a temperature that is not the temperature the animal experiences.

Independent verification. A digital thermometer with a probe, and an infrared thermometer for surface temperatures, checked against each other. Analogue dial thermometers and stick-on strips are frequently far out.

The UVB lamp. UVB output falls long before a lamp stops producing visible light, so a lamp that looks fine may be doing nothing useful. Know the type you are using, the correct distance for that type, whether mesh sits between it and the animal, and when it was last replaced.

The gradient. Not a single number, but a map: basking surface, warm end, cool end, and night-time low, measured rather than assumed.

Power failure planning. What happens to a tropical species during a winter power cut, and whether you have a plan that does not involve improvising at two in the morning.

What never to do

Do not freeze the body if you want a diagnosis.

Do not put a new lizard straight into the enclosure because it is set up and running. This is the most common route by which one death becomes two.

Do not reuse substrate, wood or water bowls from an animal that died of an unknown cause.

Do not clean with phenol-based disinfectants, the ones with a strong medicinal smell, unless you have specifically confirmed the product is safe for reptile enclosures and rinsed exhaustively. Reptiles are sensitive to them.

Do not assume that because a general disinfectant says it kills viruses and bacteria, it kills reptile Cryptosporidium. Very few things do.

Do not skip telling the seller or breeder if a recently acquired animal died. Others from the same clutch or shipment may be at risk, and reputable sources want to know.

Do not dispose of the body in general household waste without checking. Rules on home burial, pet crematoria and clinical waste differ considerably between countries and even between local authorities, and your vet will know the local position.

Grief, and the guilt that usually comes with it

The template this article replaced assumed a lizard grieves for a lost companion. It does not. Lizards are not socially bonded in the way that assumption requires, and a surviving lizard in a separate enclosure is not mourning.

The grief in this situation is yours, and it is often harder than people expect for two reasons.

The first is that grief for a reptile is frequently dismissed by others, which leaves the owner without the social permission that follows the death of a dog. The attachment is real regardless of whether it was reciprocated in the way a mammal reciprocates.

The second is guilt. Because so many reptile deaths involve some husbandry component, owners tend to arrive at a verdict of their own negligence within about an hour, usually without evidence. That verdict is often wrong, and even when a husbandry factor genuinely contributed, it is almost always something that was invisible rather than something that was ignored. A thermostat that failed silently, a UVB lamp past its useful output, a parasite acquired before you owned the animal.

This is another argument for the post-mortem. A specific cause, including one you could not have prevented, is easier to carry than an open question you will answer with self-blame.

When to get help

Contact an exotics or reptile vet the same day if:

• A lizard has died and you want a cause established
• A second animal in the same collection has died or become unwell
• Any remaining reptile is losing weight, regurgitating, or has changed its droppings
• A recently acquired animal died and others came from the same source
• Anyone in the household with a weakened immune system has been in contact with the enclosure

An enclosure that has been stripped, cleaned, disinfected with proper contact time, rinsed and dried is a fresh start. One that has simply been wiped out and refilled is not.

Bring, or send ahead: the refrigerated body, your measured temperature and humidity readings, the UVB lamp type and its age, the substrate type, the full diet and supplement schedule, when the animal last ate, shed and passed droppings, the weight trend if you have one, where the animal came from and how long ago, and whether it was quarantined on arrival. That last question is the one that most often explains a death in a recently acquired reptile.