Importance of Diagnostics
Reptiles are masters of hiding signs of illness. Many of my fellow reptile keepers and veterinary colleagues have stories of animals seeming fine that decline drastically and pass away- I even have such stories like this. Because very subtle changes in a reptile’s behavior can be the start of disease, sometimes veterinarians need a more internal picture of what is going on, which is what diagnostics provide.
One of the founding parts of a workup for a reptile is bloodwork- which comprises of two components- a complete blood count (CBC) and a chemistry panel. The CBC helps assess white blood cell counts, red blood cell counts, and platelet numbers. The CBC can assess whether an animal has an inflammatory/infectious process going on and whether an animal is anemic. Depending on the types of white blood cells that are elevated can also give insight into the chronicity of the condition as well. While this information can be helpful, it is not very specific, as it alone does not tell you where the infection/inflammation is in the body. This is where chemistry panel can provide some assistance and additional information. The chemistry assesses the function of various organs such as the liver and kidneys, minerals, electrolytes, and plasma proteins. If signs of infection/inflammation on the CBC coincide with elevations in certain organ parameters, this can clue a veterinarian into narrowing down an affected organ system. Even in non-infectious cases, the chemistry panel can still provide this information in cases where organ failure and other metabolic diseases are occurring. The caveat with the chemistry is that for some organs such as the kidney, the bio marker- uric acid- can remain normal despite significant kidney disease and/or gout. Additionally, because reptile medicine is not nearly as studied as dog/cat medicine, the reference ranges for “normal” blood work for the various species is either very large or non-existent, thus veterinarians need to use comparable species to get baselines.
Radiology can complement and also shed light in different ways compared to bloodwork. The most basic and most readily available form of radiology is an X-ray or radiograph. X-rays can help establish whether organs are enlarged, look for internal masses and/or follicles, assess musculoskeletal structures for bone density and/or fractures, assess GI tract motility, and much more. For disease that may not cause obvious changes in bloodwork such as constipation, intestinal impaction, and urinary bladder stones (for those species that have a urinary bladder), X-rays are some of the only ways to definitively diagnose these conditions. For more obscure diseases or species where X-rays may be less helpful (chelonians), other imaging modalities such as ultrasound and CT imaging can be used to get detailed internal pictures.
While bloodwork and radiology help paint and internal picture of a reptile, sometimes reptiles can present with external issues, such as a bumps or masses. While it is easy to assume that every bump on a reptile is an abscess, reptiles can also develop cancers like other animals, or sometimes other non-cancerous growths such as inflammation and cysts. A common saying I always tell clients is “a bump is a bump until you look at it under a microscope”. This applies for all species, and collecting samples for cytology or biopsy can help provide information into the disease processes occurring. For example, biopsies allowed me to diagnose a Bearded Dragon with yellow fungus, a Corn Snake with advanced renal disease, and an Ackie Monitor with axonal degeneration of the spine. Cytologies are minimally invasive but if a lesion is difficult to aspirate, it may misdiagnose a condition. Biopsies provide more detail on a specific lesion but are more invasive and take more time to process.
Samples used for cytology and biopsy can also be harnessed to rule out infectious diseases. Fecal examinations for internal parasites, cultures for bacteria and fungi, and PCR results for viruses and other pathogens are all options to provide specific focused care. This is important given the great variety between different pathogens. Not all parasites are the same, not all bacteria are the same, and not all fungi are the same. Due to these differences, different drugs will respond differently to these pathogens, with some being very effective in treating pathogens whereas others are ineffective. Ensuring we are using targeted antimicrobials helps provide the most effective treatment while not contributing to antibiotic resistance. Sometimes, especially if a wound/lesion does not improve, looking for other organisms such as fungi can help provide clinical resolution. The problem these types of tests run into is that sometimes due to sample collection- sometimes parasites and/or bacteria may be shed intermittently- a negative result may not be 100% definitive. Additionally, some organisms are harder to cultivate than others- the bearded dragon I diagnosed with yellow fungus had a negative fungal culture despite having a fungal infection.
In sum, each diagnostic test has its strengths and weaknesses in providing veterinarians the pertinent information needed to create a specific, tailored treatment plan for reptilian patients. While not every diagnostic is required for every case, these tests are useful to help provide the best care possible to our reptile pets.
