Case Study #4 Parasitology

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

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

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

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??

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?

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

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

Findings

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

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