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12 Causes of Sudden Death in Iguanas

Melissa cares for a variety of exotic animals and has completed a certificate in veterinary assisting and a bachelor's degree in biology.


Why did my reptile suddenly die? This is a common question many owners have upon finding their deceased pet, which may or may not have had symptoms prior. Iguanas are frequently kept as pets, with green iguanas being one of the more popular pet reptiles in the exotic animal trade. These animals actually have relatively simple care, provided that the owner does adequate research from reputable sources.

Common Symptoms of Disease in Iguanas

Often times reptiles present symptoms of more advanced health issues that can often be mistaken for the sole cause of their deteriorating health. Sometimes the symptoms and cause of sudden death overlap, or certain conditions occur simultaneously. Unfortunately, many of these symptoms are commonly observed in iguanas and are largely due to preventable husbandry errors.

  • Prolapses can occur due to constipation, nutritional issues, egg-laying problems and other issues.
  • Respiratory distress signs such as dyspnea and open-mouth breathing.
  • Anorexia: This is a very general symptom that can cause death due to lack of proper nutritional intake, but is a result of underlying conditions.
  • Dehydration: A common symptom of many serious diseases.
  • Distended abdomen/bloating: This can be indicative of gastrointestinal issues, dystocia (although healthy gravid animals also present this), and other serious illnesses.
  • Weight loss can be secondary to anorexia or be a result of parasitism and other diseases.
  • Stress: Most illnesses will result in chronic stress in reptiles that will exacerbate other symptoms.
  • Dystocia­­­: Also called egg binding, this is a life-threatening yet sadly common issue [3].

Why Did My Baby Iguana Die?

There is often a difference between the diseases that younger and older iguanas can contract. However, nutritional issues can occur in younger iguanas in as little as five months. Hatchlings fed insufficient calcium levels may also develop severe nutritional osteodystrophy [1], and kidney failure can also occur at any age [11]. As younger animals are still growing, it is even more imperative to ensure they are getting adequate nutrition. Sadly, there is some misinformation on how to properly feed baby iguanas, including the myth that they are insectivorous when they are younger.


Sudden Death of Adult Iguanas

Even though adult iguanas can be hardier than adults, many owners are faced with the sudden death of these older animals. Sadly, what often appears to be sudden mortality is often the result of chronic conditions with subtle symptoms that the owner has missed for some time, and reptiles can be adept at hiding signs of illness, in addition to being less expressive than their mammal counterparts. The following are some of the more common ailments that cause perceived "sudden" death in adult and young green iguanas [8].

Reproductive and Egg-Laying Issues

Sadly, dystocia and egg binding is a common ailment of captive reptiles and a common presentation in green iguanas to veterinary hospitals, despite the complication being rare in wild reptiles [8]. Retained eggs can remain in the uterus for a period of time without obvious signs, which can lead to serious complications down the road [15].

  • If your iguana is female, you will want to pay special attention to this condition, as issues with husbandry such as nutrition, temperature, improper nesting site, and inadequate hydration are frequent causes [8].
  • Dystocia can also be a result or symptom of other underlying issues. The eggs can be malformed or broken, infections may be present, or the iguana can have abnormal reproductive anatomy [3][16].
  • If your female iguana had a distended abdomen and quickly became depressed and inactive, with death following a few days later, it may have been unable to lay eggs [3][8].
  • Egg yolk coelomitis or peritonitis is a common reproductive disease in iguanas that occurs when the retained eggs rupture in the body cavity of the iguana. This condition causes the animal to rapidly decline [8][15].

Kidney Diseases

As opposed to acute kidney/renal disease, unfortunately, chronic kidney or renal disease is an extremely common cause of sudden death in older adult captive iguanas. Acute kidney disease results from inflammation, infection, or intoxication [6][8].

The predisposing factors for chronic kidney disease involve improper husbandry-related factors; most often high protein diets and chronic dehydration from low humidity levels, which cause hyperuricemia, gout, and nephrosis [6][16]. Secondary nutritional hyperparathyroidism is also predisposing disease [8].

Kidney disease may cause death due to nitrogenous waste accumulation and electrolyte imbalances. Gout and soft tissue mineralization occur when the majority of renal function has been lost [16].

Owners tend to notice symptoms of chronic kidney disease in the late stages when the iguana is lethargic, anorexic, and in poor body condition. Once the disease progresses to this point of minimal renal function, the prognosis is poor even with treatment [11][16].

Metabolic Bone Diseases

You'll often hear the term "metabolic bone disease" (MBD) used to describe a common ailment in reptiles and especially iguanas, however, this word describes several different medical disorders that affect the integrity of the bones [8].

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  • Nutritional secondary hyperparathyroidism (NSHP) is the specific metabolic bone disease that is the most common disease in captive reptiles [8][16]. In one study, 84% of lizard patients were diagnosed with some form of nutritional MDB [12].
  • Husbandry errors can lead to reduced ionized calcium levels which are essential for the movement of the gastrointestinal tract. This condition may result in a slower transit time within the gut, which then leads to dehydration of the bowel contents, obstipation, and firm fecolith production.
  • While in many cases, recovery from nutritional MBD can be expected with medical intervention, in severe chronic cases, death can occur. Prolonged hypocalcemia may result in paralysis, dystocia, and spinal fractures that can lead to severe neurological issues such as the inability to urinate and defecate [8][12[16].
  • Iatrogenic hypervitaminosis D is associated with hypercalcemia, which can lead to mineral deposits in the lungs, causing them to be prone to fracturing. When this happens, blood may be produced from the nostrils or mouth, which is often fatal [8].

Iguana With Paralysis

Lower Respiratory Diseases

Dyspnea is another word for labored breathing. It is a common sign of respiratory disease in reptiles.

  • Pneumonia of bacterial origin is likely the most common respiratory disease of lizards, however, it can also be fungal or parasitic. Generally a disease of poor husbandry due to improper ventilation, nutrition, humidity, or temperature, it can also occur due to typical bacteria becoming pathogenic when the host is immunocompromised due to chronic stress. Cases of acute or peracute pneumonia often present as sudden death due to sepsis, with previous symptoms of lethargy, anorexia and dyspnea [16].
  • Aspiration pneumonia may occur as a result of improper technique with assist feeding.
  • Obstructions in the airway can also cause an iguana to have respiratory distress. In 2 cases, green iguanas had human hair wrapped around their epiglottis and trachea, of which removal restored proper breathing.
  • Cancer, pulmonary edema from cardiac or hepatic disease, and other lesions that prevent lung expansion can also result in dyspnea and perhaps sudden death [8][16].


There is a multitude of ways that iguanas can become infected. Various types of viruses, bacteria, fungi, and parasites have caused serious diseases in reptiles [8].

The chances of infection in reptiles may increase during the colder winter months. The following are some diseases and pathogens that can cause sudden death, either singularly or when they occur concurrently with other diseases and generalized weakened condition [8].

While wild reptiles all carry parasites, there can be higher concentrations of these organisms in confined spaces, and this is further exacerbated by unsanitary conditions, poor diet, and chronic stress from poor husbandry, which can be lethal for the carriers [7][14]

The following are a few infectious diseases that can cause sudden death:

  • Cryptosporidiosis: Parasite that infected via the fecal-oral route and contaminated surfaces. May cause gastric inflammation, organ dysfunction and congestion and cholecystitis [10].
  • Abscesses: Depending on their location, these growths can become severe when left untreated.
  • Entomelas sp.: A common lungworm in lizards.
  • Acute hepatitis: A condition that is associated with infectious agents and is common in reptiles.
  • Septicemia: This is a life-threatening complication of systemic bacterial infection.
  • Enteritis: Inflammation of the intestine from an infection.
  • Gastroenteritis: Inflammation of the digestive system from bacterial, viral, or parasitic infection.
  • Acanthamoeba sp.: Aparasite that infects the soft tissue of reptiles.
  • A herpes-like virus has been shown to cause lymphocytosis, splenic hyperplasia, and histocytic lymphoid infiltrates of the liver, spleen, myocardium, and bone marrow in iguanas [8].

Iguana With Breathing Issues

Neoplasia and Cancer

Cancer has been found to have a prevalence of 9.8 percent in reptiles. Unsurprisingly, cancer and tumor growth can result in sudden death in various ways (although not all abnormal growths are neoplastic). For instance, as previously stated, neoplasia of the lungs can lead to dyspnea and death.

  • Neoplasias have been found to affect the brain and spinal cord, ovaries, and heart [4]. Leukemia is also possible in green iguanas [13].
  • Several non-specific symptoms can point to cancer, such as lethargy and anorexia.
  • Coelomic neoplasia may result in the abdomen becoming enlarged.
  • Malignant cancers generally have a poor prognosis unless detected early and treated aggressively [8].


If an iguana ingests a poisonous plant or other toxic substance, this can result in a relatively rapid death [8]. Exposures to toxins, poisons and nephrotoxic drugs may result in acute renal failure, with symptoms including sudden onset of depression, lethargy, anorexia, weakness, and lack of urination. However, unlike chronic renal disease, the iguana can be in good body condition when the symptoms become severe [6]. Some common sources of toxicities include the following:

  • Plants such as those in the heath family (azalea, laurel, and rhododendrons), lilies, castor bean, sago palm.
  • Zinc intoxication from ingestion of pennies.
  • Rodenticides can cause dyspnea, lethargy, anorexia, paralysis, tremors, and seizures.
  • Paint solvents.
  • Lead poisoning.

Cardiac Disease

Like other animals, iguanas can get heart complications such as cardiomyopathy, which can cause heart failure and sudden death. Heart disease in iguanas can be congenital or be associated with other health issues like cancer, gout, and sepsis from infections.

Symptoms for cardiovascular issues in reptiles include lethargy, respiratory distress, ascites in coelom, generalized weakness, and peripheral swelling [2].


Foreign Body Ingestion

Cases of reptiles consuming foreign material are common and often involve dirt, stones, and sand. This condition can become life-threatening if the material obstructs the intestinal tract. Symptoms include lethargy, vomiting, anorexia, constipation, prolapse, diarrhea, and rarely, a distended abdomen.

Some symptoms can persist for weeks to months. Intestinal atony, or reduced muscle tone in the intestines, has also been reported in green iguanas. The prognosis for this condition depends on the composition and potential toxicity of the material and any damage it may have caused [5][8].


Despite being reptiles, iguanas can become overheated. A common cause of iguanas suddenly dying from heatstroke, or hyperthermia, are malfunctioning heating devices and being left in direct sunlight in an enclosed container. The deceased animal is often warm to the touch when this occurs [8].



Visceral, articular, and periarticular gout are common in pet reptiles. Gout is a metabolic disease that describes the overproduction or underexcretion of uric acid, resulting in hyperuricemia and deposition of urate crystals.

Green iguanas can be at risk of getting gout when they are regularly fed inappropriate animal sources of protein or when there is dehydration or kidney damage due to kidney diseases. Misuse of some antibiotics can cause tubular nephrosis, putting reptiles at risk for hyperuricemia.

In the later stages of visceral gout, urate crystal deposits called tophi build up throughout the body. Tophi deposition often occurs in the kidneys, liver, pericardial sac, the muscles of the head and the subcutaneous tissue. Advanced cases of gout in iguanas can cause the kidneys to become enlarged. Severe cases can make it painful for the iguana to move, eat or drink. The prognosis for cases like those is grave [9].


  1. Anderson, Marilyn P., and Charles C. Capen. "Nutritional osteodystrophy in captive green iguanas (Iguana iguan a)." Virchows Archiv B 21.1 (1976): 229-247.
  3. Axelson, Rick. "Iguana-Problems". VCA Hospitals
  4. Bel, Lucia, et al. "Diagnosis and surgical management of malignant ovarian teratoma in a green iguana (Iguana iguana)." BMC veterinary research 12.1 (2016): 1-5.
  5. Büker, Markus, et al. "Gastrointestinal obstruction caused by a radiolucent foreign body in a green iguana (Iguana iguana)." The Canadian Veterinary Journal 51.5 (2010): 511.
  6. de la Navarre, Byron. Acute and chronic renal disease (specifically in lizard species) (Proceedings). October 1, 2008
  7. de la Navarre, Byron. "Common parasitic diseases of reptiles and amphibians." CVC in San Diego proceedings (2008).
  8. Divers, Stephen J., and Douglas R. Mader, eds. Reptile Medicine and Surgery-E-Book. Elsevier Health Sciences, 2005.
  9. Divers, Stephen. Metabolic and Endocrine Diseases of Reptiles
  10. Gałęcki, Remigiusz, and Rajmund Sokół. "Treatment of cryptosporidiosis in captive green iguanas (Iguana iguana)." Veterinary parasitology 252 (2018): 17-21.
  11. Lock, Brad. Kidney Disease in Reptiles.
  12. McWilliams, Deborah A., and Steve Leeson. "Metabolic bone disease in lizards: Prevalence and potential for monitoring bone health." Nutrition Advisory Group 19 (2001): 120.
  13. Miller, Debra L. "Immunoblastic Leukemia In An Iguana (Iguana Iguana) IAAAM 2000."
  14. Loukopoulos, Panayiotis, et al. "Lethal Ozolaimus megatyphlon infection in a green iguana (Iguana iguana rhinolopa)." Journal of zoo and wildlife medicine 38.1 (2007): 131-134.
  15. Pollock, Christal. Reproductive Disease in Reptiles: Twelve Key Facts. September 23, 2012
  16. Divers, Stephen J., and Scott J. Stahl, eds. Mader's Reptile and Amphibian Medicine and Surgery-E-Book. Elsevier Health Sciences, 2018.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2021 Melissa A Smith

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