Cardiac Disease in Reptiles

I would like to share with you two interesting cardiac cases in reptiles which I encountered in the past, both causing heart failure but with different presentations, underlying disease mechanisms and outcomes. Cardiac conditions in reptiles are rarely seen, possibly due to under-diagnosis or not being presented frequently to specialist reptile clinics. This could also be due to various other illnesses and diseases causing the death of pet reptiles before they reach the grand old age when they are likely to present with cardiac failure.

Cornsnake

In any case, I was very surprised to see both of the following cases within two weeks of each other, when in my previous three years of clinical practice I have rarely encountered such problems in reptile species. The first case was a 5 year old female Yemen Chameleon named Blossom. Blossom is an old girl for her species and has now laid 6 fertile clutches of eggs which is a great achievement in itself and a credit to her owners excellent knowledge and care for these specialist reptiles. Chameleons do not make easy pets, but especially females as they often get reproductive and metabolic problems. In fact, Blossom’s owner was concerned that perhaps this time around Blossom was egg-bound or unable to lay her next clutch as she was mated 10-12 weeks previously and had failed to lay any eggs. She was also quieter than usual, had a decreased appetite, was showing darker stress colouration, and her abdomen was becoming enlarged suggesting she may be gravid (carrying eggs).

When Blossom presented to the clinic her physical examination was unremarkable apart from a distended abdomen. I decided to take an X-ray to determine whether she was indeed gravid or egg-bound, or suffering from a condition called pre-ovulatory stasis whereby the ovaries produce multiple follicles but fail to ovulate and progress to laying a clutch of eggs. I was extremely surprised to find that the distended abdomen did not contain eggs or follicles but was full of fluid creating a grainy, diffusely opaque greyish appearance throughout the abdomen and obscuring the abdominal contents. The striking finding on the X-ray however was an enlarged perfectly spherical cardiac outline suggesting heart enlargement. More specifically this appearance indicated an accumulation of fluid in the pericardium or thin membranous sac that surrounds the heart rather than enlargement of the heart itself obscured within this fluid sac.

chameleon pericardial effusion A diagnosis of pericardial effusion was made, which has most likely resulted from primary cardiac failure due to old age and high metabolic stresses or demands throughout Blossom’s life. Secondary fluid accumulation in the abdomen called ascites has resulted from the failure of the heart to pump blood as effectively as normal. This inefficiency in the pumping mechanism leads to fluid pressure building up in the vessels leading to the heart and subsequently fluid leaking from the blood vessels into surrounding tissues and organs, eventually accumulating over time in the abdominal cavity. Other causes for pericardial effusion can include parasitic disease and infection but considering Blossom’s relatively bright demeanour, history, husbandry conditions and age these are unlikely causes in this case. Unfortunately for Blossom this does mean that she has congestive heart failure, which will inevitably worsen with time.

Treatment for congestive heart failure in reptiles is difficult and not a great deal of research has been carried out on the various drugs available in terms of efficacy and safety. The mainstay of treatment in such congestive heart failure cases where fluid accumulation is the most problematic clinical sign is the use of diuretic medications, which encourage elimination of excessive fluid from the body. Unfortunately, the risks of diuretic treatment in reptiles are higher than in mammals as they have a specialised renal system with a unique blood supply to the kidneys. This can therefore render them susceptible to dehydration and kidney failure on diuretics or other medications. Similarly, because treatment would involve injecting Blossom with medication 2-3 times daily, myself and the owner agreed that this would be unfair and cause her far more stress and pain than was humane considering chameleons make for stressful patients at the best of times. At present Blossom is doing well without treatment, so as long as she remains comfortable and her breathing is unaffected we will monitor her progress. I have suggested decreasing the temperatures in her vivarium to the lower end of her preferred optimum temperature zone, and also advised reducing her food intake. Both of these alterations in her husbandry are an attempt to decrease the metabolic demands on her cardiovascular system and hence try to prolong her lifespan as much as possible whilst keeping her comfortable. It will be interesting to see how long she remains healthy and bright, but sadly there may come a time where she dies of acute cardiac failure or we have to consider euthanasia when her breathing or quality of life is compromised. At this point the fact that Blossom has thrived, reproduced and lived beyond her natural lifespan in the wild to succumb to a geriatric disease rarely seen in captive reptiles is a credit to her owners excellent care.

Blossom Chameleon

 

 

 

 

 

 

 

 

The second cardiac case I saw was an old cornsnake, of unknown age due to being rehomed as a mature adult snake. I do not have as much background information for this case as it was seen by a colleague in my previous practice. The snake presented with lethargy and inappetance, having refused food for several weeks. The striking physical exam finding was a large firm swelling in the cranial third of the body corresponding to the site of the heart or possibly the stomach. X-rays (seen above and below) revealed a soft tissue opacity in this region suggesting one of either of these organs was grossly enlarged. Due to the appearance on the X-ray a foreign body ingestion in the stomach could be ruled out. Unfortunately the snake died in clinic so after discussion with the owner a post mortem exam was carried out which revealed the enlarged organ to be the heart. All three chambers of the heart were massively dilated to about three times their normal size and the ventricle was grossly thickened and enlarged. As an aside mammals and birds have four chambers of the heart compared to three chambers in reptiles and amphibians, and just two in fish!

Cornsnake DCM dissectionA diagnosis of dilated cardiomyopathy was made which lead to acute cardiac failure and death in this animal. If the snake hadn’t died this diagnosis would have been made by doing an ultrasound scan to determine what indeed the enlarged structure was. Another possibility I would have been concerned about in this case before seeing the X-rays was a parasitic infection called Cryptosporidiosis which can cause a large swollen stomach in infected snakes manifesting as a firm mid body swelling on physical examination. Again, the most likely cause of cardiac disease was degeneration of the heart and valves associated with ageing. If the snake had presented at an earlier stage of the disease treatment with cardiac medications may have been attempted but unfortunately in this case it was too late.

Cornsnake DCM Lateral 1I hope you found these case studies interesting, and if you have any questions or comments please feel free to ask in the comments section below. Similarly if you have any topics you would like me to write about in future let me know.