Page 362 - WSAVA2018
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 25-28 September, 2018 | Singapore
M. Lappin1
1Center for Companion Animal Studies,
Colorado State University, Fort Collins Colorado, USA
Objectives. The primary objectives of this session are to review the known parasitic and bacterial causes of diarrhea followed by a discussion of optimal diagnostic tests, treatments and preventions.
Gastrointestinal (GI) signs can be the result of primary diseases of the GI system or secondary GI diseases. The secondary GI diseases are generally those of
the kidneys, liver, pancreas (pancreatitis or exocrine pancreatic insufficiency [mainly dogs]), endocrine
system (hyoadrenocorticism; diabetic ketoacidosis; hyperthyroidism [mainly cats]), or central nervous system.
Differential diagnoses for primary GI diseases are
often grouped into obstruction (masses, foreign body, and intussusception), dietary intolerance, drugs/toxins (garbage gut), inflammatory gastric and bowel diseases, neoplasia, infectious diseases, and parasites.
The primary bacteria associated with gastrointestinal tract disease in dogs and cats include Salmonella spp., Campylobacter spp., Clostridium perfringens, Helicobacter spp., bacterial overgrowth syndrome, bacterial peritonitis, and bacterial cholangiohepatitis. The primary nematodes are Ancylostoma/Uncinaria, Trichuris vulpis (dogs), Strongyloides, Dirofilaria immitis (vomiting in cats), Toxocara spp., Toxascaris leonina, Ollulanus tricuspis (cats), and Physaloptera spp. Common enteric protozoans include Giardia spp., Cystoisospora spp., Cryptosporidium spp., and Tritrichomonas foetus (blagburni).
Occasionally, otherwise healthy dogs or cats with acute diarrhea and normal physical examination findings
can be handled conservatively by withholding food
for 24 hours followed by introduction of a bland food for several days. For all animals with diarrhea with no apparent cause on physical examination, I will perform a fecal flotation, fecal wet mount examination, complete blood cell count (CBC), and rectal cytology if diarrhea
is present. While the CBC generally does not lead to a specific diagnosis, the presence of eosinophilia makes inflammatory bowel diseases and parasitism more likely.
I perform acid-fast staining of a fecal smear or immunofluorescence antibody staining (Merifluor Giardia/Cryptosporidium, Meridian Diagnostics) on all animals with diarrhea to assess for the presence of
Cryptosporidium spp. oocysts. A wet mount examination may aid in identifying trophozoites of Tritrichomonas and Giardia. If neutrophils or spirochetes are evident
on rectal cytology I recommend fecal culture (or PCR)
for Salmonella spp. and Campylobacter spp.. If spore- forming rods consistent with Clostridium perfringens are present in large numbers, fecal enterotoxin assays and PCR assays can be performed to help confirm
the diagnosis. However, these tests can be positive in healthy animals as well and so has less than 100% predictive value.
There are multiple drugs used in the treatment of gastrointestinal parasitic infections. For all puppies and kittens, the strategic deworming recommendations for the control of hookworm and roundworm infections from the Centers for Disease Control and the American Association of Veterinary Parasitologists should be followed by veterinary practitioners. ( ncidod/dpd/parasites/ascaris/prevention.htm; www.
If owners are interested in more in depth information a good website is available (
Giardia infections often respond clinically to the administration of metronidazole but infection is usually not eliminated. Administration of metronidazole benzoate at 25 mg/kg, q12hr, PO, for 7 days was effective in suppressing cyst shedding to below detectable limits
in 26 cats. This is the maximum dose of metronidazole that should be used; CNS toxicity can be induced by overdosing or as a cumulative neurotoxin. I personally use fenbendazole at 50 mg/kg, PO, daily for at least
5 days in dogs or cats with giardiasis. Metronidazole
and fenbendazole can be combined in resistant
cases. Febantel containing products have been used successfully in dogs and cats and this drug is approved for the treatment of giardiasis in some countries. The empirical dog dose is the deworming dose, daily for at least 3 days. Paromomycin, ronidazole, and nitazoxanide are alternate drugs that could be tried in cases with resistant giardiasis. However, in my experience, dogs or cats with Giardia that fails to respond to metronidazole and fenbendazole have another underlying problem. Tinidazole at 30 mg/kg, PO, daily for 7 - 14 days may
be effective in some dogs and cats for the treatment
of giardiasis. Secnidazole at 30 mg/kg, PO, once was reported for treatment of cats with Giardia in Brazil. Additional information is needed before this protocol can be widely recommended.
Diet changes and probiotics can be tried for the management of parasitic diarrhea. Multiple drugs have been evaluated for the treatment of cats with T. foetus infections; until recently no drug eliminated infection and diarrhea rarely resolves during the treatment period. Recently ronidazole at 30 mg/kg, PO, q24hr, for 14 days eliminated clinical signs of disease and trophozoites

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