C.S.I. Belongil – Backyard forensics

This is a case report which highlights the complexities of diagnosing serious disease, in a cat who refuses to let-on about what he’s been up to.  Using-up at least one of his nine lives, Oscar’s case sounds more like a script from TV medical drama than the life of a backyard cat in Byron Bay.

2009-08-08 at 06-44-11

History

Oscar, a 5 year old, desexed, male, purebred Layanese, recently resettled in a new home, had been out exploring with a new feline mate from next door. Bordering on local bushland, there were plenty of hazards for a curious cat: exotic plants, insects, snakes and paralysis ticks.

Oscar presented with a history of lethargy, poor appetite (possibly eating elsewhere) of 2 weeks, maybe a month.  His weight had dropped from 6.5 to 5.8kg since the last visit, for a cat fight wound, despite a high quality commercial diet. Was he vomiting? Difficult to say, given an outdoorsy lifestyle.  Certainly nothing abnormal in the kitty litter tray.

Examination

In consultation, Oscar was bright, alert, and happy to wander and explore the room. He was not weak and displayed usual feline athleticism traversing the hospital landscape, scoping for an escape portal. On one occasion he stumbled on his right hind, leaping to a chair; something the owners had noticed on stairs at home. Such clumsiness could be normal in human and canine patients, but not a cat.

Neurological exam was normal apart from slightly depressed patella reflexes. He was sensitive mid-spine, but many healthy cats are.  He had a subtle heart murmur (1/6) on the left. Otherwise his vital signs and physical examination was normal. No ticks were found, but we couldn’t be sure if one had just dropped off.

Had not the owner told me he was unwell, I would not have guessed it.  But given Oscar was  a treasured family member and the owners unphased by the cost, a blood biochemistry and haematology were run. Oscar went home with orders of strict home confinement: we needed to observe him more closely.

Test Results

36-hours later the results were through. A little longer than usual as the alarming readings were being double checked and scrutised by senior pathologists in the lab. Here were the abnormal findings of both the physical exam and lab tests.

  1. Wt loss – 10% over 3 months.
  2. Poor appetite – eating elsewhere?
  3. Lethargy – mild
  4. Stumbling in hinds
  5. Heart murmur – previously undetected birth defect?
  6. Thoracolumbar spinal pain  – possibly spurious.
  7. Depressed patella reflexes, more suggestive of tick, snake or spinal disease, but not consistent with the location his back seemed painful.
  8. Anaemia [Hct 20, NR: 28-45]. A 16% reticulocyte count indicated lots of new baby red blood cells were flooding in from bone marrow replace those lost.
  9. Neutropenia [ 1.0, NR: 3.8 – 5] – Lack of a white blood cell which stands as the body’s first line of defence against bacterial invasion. Without it you may swiftly die of overwhelming infection.  Reduced numbers of  this cell could have been viral, bone marrow disease, or lost to severe inflammatory demand.
  10. Abnormal lymphocytes in circulation – possibly just reacting to immunologic stimulus, but couldn’t rule out leukaemia.
  11. Mycoplasma felis, a bacteria that lives in red blood cells and can cause anaemia, were not seen in the bloodfilm, but this didn’t rule out their presence.
  12. 1% Heinz bodies – not high enough to support auto-immune destruction of red blood cells.
  13. Blood potassium markedly increased [8.4, NR 3.7 – 4.9] – no evidence of sample lysis, or urinary tract disease. Possible due to muscle injury.
  14. Elevated ALT enzyme of 189 [NR: 1- 80]  – Indicating liver disease or muscle damage.
  15. Elevated AST enzyme of 81 [NR: 1 – 60] – Indicating liver disease or insult.
  16. Normal Creatinine kinase; an enzyme increased with muscle disease and black snake envenomation.

In summary, the picture was rich and complex, involving multiple organ systems, with anaemia, suppressed bone marrow production of some white blood cells, but not red. The challenge here was to come up with a unifying explanation of a single disease process that could cause all this. Using multiple diseases to explain a cluster of findings is plausible in the chronically sick, elderly patient, but rare in the young.

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Possible Diagnoses:

Here is a shortlist of options, the evidence that supports them, and those that don’t.  Some findings, like spinal sensitivity, are subtle and subjective, and may be able to be overlooked, while others like the anaemia are major and concrete and must be explained by a diagnosis.

A. Oscar had caught Feline Immunodeficiency virus (FIV) during one of his recent fights. The virus had suppressed his bone marrow, the neutrophils had run out, he was developing infections throughout his body, in his spine and liver, and mycoplasma felis, working in concert, was destroying his red blood cells. FIV, like HIV, can be a bit of a clinical wildcard as, once you cripple the immune system, diseases can spring up anywhere.
Supportive: 1, 2, 3, 4, 8, 9, 10, 14, 15, 16.
Against: 11

B. Oscar had cancer. Probably lymphoma, crowding out the bone marrow, in liver, even in the spine, causing the neurologic signs in the back legs. This may explain the low neutrophils, abnormal lymphocytes, wt loss, poor appetite. Like FIV, lymphoma is a disseminated disease that can explain a complex and confusing bunch of findings in many different systems.
Supportive: 1, 2, 3, 4, 6, 7, 9, 10, 11, 14, 15, 16
Against: 8

C. Oscar had Toxoplasmosis. This protozoal disease cycles between rodent and cat, and can cause neurologic, liver, muscle, respiratory and other symptoms. This alone wouldn’t have explained all the findings, but it may have been working in concert with FIV.
Supportive: 2, 3, 4, 6, 7, 14, 15
Against: 8, 9

D. Oscar’s immune system was malfunctioning. Tricked into thinking his own red blood cells were foreign, it was destroying them, and using-up his white blood cells in the process. Like the stupor of altitude, anaemia was starving his body of oxygen, causing liver enzymes to rise, weakness, lethargy, and clumsiness in the back legs. Mycoplasma felis could have triggered this process, but without seeing them in the blood smear, we couldn’t be sure.
Supportive: 1, 2, 3, 4, 8, 10
Against: 11, 12

E. Oscar has encountered something that had caused him to bleed, near fatally, during the week before he came to the vet. Without any history to support it, major trauma, like a car accident or fall, seemed unlikely.  Snake venoms contain hundreds of chemical compounds, many not studied, some causing anaemias, some damage muscle, while others cause neurological symptoms.  Could a venom also be idiosyncratically suppressing Oscar’s bone marrow? Not reported, but possible. This diagnosis would only explain symptoms in the previous week or 2.
Supportive: 3, 4, 7, 8, 11, 12
Against: 1, 16

More Results

Luckily, Oscar was on the upswing, wondering what was all the fuss was about, while owner and vet where sweating on the test results. He was confined, eating, and busting to do a runner whenever a door was open. 12-hours later, more results were in:

  • Feline Immunodeficiency Virus: NEGATIVE.
  • Feline Leukaemia Virus: NEGATIVE.

Suddenly cancer was higher on our list of possibilities and a bone marrow biopsy was looming.

48-hours after the first blood test, a second was collected, and treatment for Toxoplasmosis started, just-in-case.  The second blood sample was looking for trends: was Oscar on a downward spiral, or bouncing back?

Fortunately the latter. His percentage of red blood cells was back up to 30%, and his neutrophil count had doubled to 2. Still well short of the low end of normal (3.8), but together with his improved strength and appetite at home, my tone was more optimistic.

Upward trends made the disease look more like a transient event, like a toxin, rather than a progressive one, like cancer. If projected backwards  in time, Oscar was haemorrhaging seriously, and possibly nearly died, 3-5 days prior to his visit to the vet.  We cancelled any invasive testing for cancer, like bone marrow biopsy, and just monitored the blood.

Two weeks later, Oscar was back to normal, apart from a mild ongoing clumsiness in a hind leg, a residual effect sometimes seen in snakebite victims. The levels of red and white cells in circulation were back to normal, the abnormal lymphocytes had disappeared.  Return to normality, without treatment, could rule out diagnoses A, B and D.  While we can’t pin an exact diagnosis on the case, a mystery toxin causing haemorrhage, such as snake venom, is top of my list.

No matter how much House or ER pet owners watch on telly each week, explaining the complexities of cases like this is a challenge. Dedicated, switched-on, clients, interested in understanding what was going on are great to work with, but those tempered with patience are even better.

Many distracted or unobservant pet owners wouldn’t have noticed Oscar’s symptoms; others wouldn’t have spent the money on getting a vet check; and many wouldn’t have invested in  diagnostic tests. Luckily, for cats like Oscar, mother nature equipped us with body systems that heal and replenish after injury, and in many cases vets need only hold the pet owner’s hand, and reassure them that, given time, the majority of diseases get better naturally.

Summary

  • Animals have secret lives, and sometimes diagnostic tests are needed to uncover the cause of an illness.
  • Diagnostic tests may point to a variety of diseases, rather than giving us a definite and singular answer.
  • Seriously unwell pets can sometimes appear relatively normal, maybe just sleeping more and slightly off food.
  • There are many diseases that are self-limiting, that get better by themselves, and vet and pet owner need only stand-back and marvel at the powers of natural healing.
  • Snake bite victims can sometimes get better without anti-venom: up to 50% of dogs and 75% of cats surviving with supportive care alone.

Acknowledgment: Thanks to Pathologist Dr Brett Stone, from QML in Brisbane, and Dr Sue Foster, Feline specialist in Perth, for holding my hand through this diagnostic process, while I held Jessica and Dain’s. For more on the congo line of information see here.

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4 Responses to “C.S.I. Belongil – Backyard forensics”

  1. Dawna Stolfi says:

    i absolutely have enjoyable reading your blog. dont cease posting the wonderful high quality info!

  2. matt says:

    thanks dawna, positive feedback like yours helps maintain the momentum. tell all your friends.

  3. Jenna Polee says:

    Interesting stuff,Thanks so much for this!

  4. Suzie Deyris says:

    Dear Matt, Thank you for your thorough way of looking at unusual symptoms, their likely causes and what can be done for our treasured wordless family members when they are suffering.
    Poss and I thank you sincerely for your help in his/our present crisis.

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