1. Case Study #4
Parasitology

2. History German shorthaired pointer, MN, 2 years, 52 lb
Active during hunting season; however, presented in late January, not during season
Goes to dog park many times a week
Current on vaccinations; previously healthy
Presented for acute collapse at home, diarrhea over past week
Eats things in yard and park
May have lost a little weight in past month

3. Clinical Findings
Dog presented unable to stand or walk, conscious but dull and unresponsive
T = 98°F; P = 55; R = 20. Weak peripheral pulses and very light pink mucous membranes. Body condition score of 3/9
Blood drawn for in-house ISTAT
Blood pressure 80/48 mmHg

4. Initial Findings and Treatment
Initiated PlasmaLyte-A at shock doses
Abnormal ISTAT findings
Glu: 60, BUN: 46, Creat: 2.3, Na+: 128, K+: 6.8,
Na/K: 18.8
Presumptive diagnosis of Addison’s disease
ACTH stimulation test performed and sent to reference lab
Dexamethasone SP given at 0.5 mg/kg IV
Dextrose 50% (diluted)—10 mL of 25% IV
Fluids switched to 0.9% NaCl with 2.5% dextrose
Dog’s mentation improved slightly to fluid therapy and dextrose but still unable to rise/stand

5. Further Information ACTH stimulation results
Pre: 3.0 (0.5–4 µg/dL)
Post: 15 (8–20 µg/dL)
These results are considered within normal limits and not diagnostic for hypoadrenocorticism (Addison’s disease)
What could be the other causes of this presentation—toxins, parasites, anaphylaxis??

6. Diagnostic Information
A fecal flotation was performed. No other diagnostics done at this time
How do you perform a fecal flotation? With a diarrheic dog, what can you do if you do not have enough feces to perform a flotation?
What is the doctor hoping to find on the fecal that may explain this dog’s presentation?

7. Answers
The flotation method used will be determined by the standard in your practice
This practice used a commercial flotation device
A fecal loop was utilized and obtained only a small amount of liquid feces
The feces was thoroughly mixed in the bottom of the device with a small amount of zinc sulfate
The “strainer” was pushed down to the bottom of the device
Additional zinc sulfate was added until a meniscus formed at the top and a cover slip was placed
The flotation sat for 15 minutes before being read

8. Answers
A direct smear can be performed when only a small amount of feces is available
A small amount of feces was obtained on a wooden stick and mixed thoroughly with a couple of drops of saline on a microscope slide. A cover slip was placed on top. This was allowed to sit for 1 minute
Both the fecal flotation and direct smear were scanned on 4× and evaluated on 10× under the microscope

9. Findings

10. Diagnosis and Treatment Plan
Only one Trichuris vulpis (whipworm) was seen on the direct smear and five on the flotation.
Diagnosis: Trichuriasis and pseudohypoadrenocorticism (false Addison’s disease)
The dog was diagnosed as having a heavy whipworm infestation
Even though only a few ova were seen on the fecal tests, it is important to remember that the very small volume of feces used for the tests would make it difficult to detect a larger number of eggs
Trichuris vulpis is the primary GI parasite infestation that can cause an Addisonian-like crisis

11. Diagnosis and Treatment Plan
Because the dog had not presented with vomiting, it was decided to give a dose of fenbendazole at 50 mg/kg and continue fluid therapy overnight
All ISTAT results were within normal limits 24 hours after presentation. The dog’s mentation and ambulation returned to normal
Discharge instructions were fenbendazole as follows: 50 mg/kg/d for 2 more days; then 50 mg/kg once a month for 3 months
The dog improved significantly over the next week and had no further recurrences