002 Antibiotics in Canine Acute Haemorrhagic Diarrhoea

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Referring here to acute bloody watery diarrhoea from typically diffuse small intestinal disorders (e.g. canine idiopathic haemorrhagic gastroenteritis syndrome); not fresh large intestinal haemorrhage or melaena.

Potential indications for antibiotics?

(1) Primary small intestinal bacterial infection with enteropathogenic bacteria:

Relatively rare
Identification in faeces does not mean causative agent

American College of Veterinary Internal Medicine Consensus Statement* (2011):

Marks SL, Rankin SC, Byrne BA, Weese JS. Enteropathogenic Bacteria in Dogs and Cats: Diagnosis, Epidemiology, Treatment, and Control. J Vet Int Med 2011. 25(6):1195-1208.

“The advent of real-time PCR panels for dogs and cats with diarrhea has provided a new paradigm for the rapid and sensitive detection of toxin genes or organisms associated with disease. Interpretation of these panels can be problematic, however, because virtually all of these bacterial organisms have been frequently isolated from the feces of clinically healthy dogs and cats.”

Discusses Clostridium difficile, Clostridium perfringens, salmonella and campylobacter
Take-home message in each case: antibiotics not recommended unless patient is showing signs of systemic illness.

(2) Bacterial or endotoxin translocation:

Intestinal translocation

Literature (experimental animal, human) supports potential occurrence

So there is potential risk and all these patients should receive antibiotics, right?

Well, if some degree of bacterial translocation occurs the systemic immune response should be able to deal with this unless the situation becomes overwhelming.

Risk-benefit analysis:
Potential benefit: may prevent sepsis if appropriate antimicrobial(s) used

  • Promoting antibiotic resistance; some enteric bacteria develop nasty multidrug resistance!
  • Oral administration may harm normal intestinal flora and thereby reduce competitive antagonism
  • Financial costs
  • Potential drug adverse effects; idiosyncratic reactions

My approach:

Dynamic decision to prescribe antibiotics made on individual patient basis
Does the patient have/does the patient develop clinical findings that raise the index of concern for sepsis risk?
Does the patient have a pre-existing reason to be more susceptible to sepsis?

Criteria include:

(1) Hard to stabilise with respect to cardiovascular status and/or hard to keep stable with repeated episodes of hypoperfusion.

(2) Evidence of SIRS criteria with appropriate changes in heart rate, respiratory rate, body temperature and/or white blood cell count; e.g.

  • Persistent tachycardia, pyrexia, tachypnoea
  • Marked degenerate neutrophilic left shift, lots of bands, severe toxicity; inappropriately normal neutrophil count; and especially neutropenia

(3) Hypoglycaemia (or maybe low-normal blood glucose)

(4) Pre-existing immunocompromise (e.g. chemotherapy) or potentially poor immune function (very young animals?)

Vast majority of canine parvovirus cases receive antibiotics.

This is an opinion- and experience-based approach, both mine and that of previous colleagues.

Here is one paper:

Unterer S, Strohmeyer K, et al. Treatment of Aseptic Dogs with Hemorrhagic Gastroenteritis with Amoxicillin/Clavulanic Acid: A Prospective Blinded Study. J Vet Int Med 2011. 25(5):973-979.

Study type: prospective, randomised, placebo-controlled, blinded
Aim: to evaluate the benefit and efficacy of amoxicillin/clavulanic acid in the treatment of dogs with aseptic HGE.

60 dogs diagnosed with HGE
Inclusion criterion: acute onset of bloody diarrhoea (<3 days)
Exclusion criteria:

  • Patients pre-treated with antibiotics
  • Patients with potential signs of sepsis
  • Patients with haemorrhagic diarrhoea because of a disease aetiology unrelated to HGE (e.g. drug adverse effects, gastrointestinal parasites)
  • Detecting bacteria in the faeces that are considered potentially primary enteropathogens (e.g. Salmonella spp. or Campylobacter spp.)

Potential signs of sepsis defined as:

  • Rectal temperature >39.5⁰C (or 103.1F)
  • White blood cell (WBC) count <4 or >25 109/L
  • Band neutrophil count >1.5 109/L)

Describe various other investigations that to allow presumptive diagnosis of idiopathic canine HGE.

Computer-generated randomisation: 30 dogs in treatment group, 30 dogs in placebo group
Treatment group: amoxicillin/clavulanic acid for 7 days
Other treatments standardised and equal for both groups

Treatment efficacy evaluation:

  • Daily assessment of clinical signs by clinician blinded to treatment using “canine HGE activity index”
  • Parameters scored: patient attitude, appetite, vomiting, stool consistency, stool frequency, dehydration
  • Obligatory hospitalisation for 3 days; thereafter scoring based on owner-provided information

Outcomes compared between treatment and placebo groups:

  • Canine HGE activity index (on any individual day and over whole course of disease)
  • Duration of hospitalisation beyond obligatory 3 days
  • Dropout rate
  • Mortality rate


  • Patients in each group similar and considered reliably comparable
  • No statistically significant difference between outcome measures between two groups
  • 6 dogs in placebo group dropped out of study due to concerning signs (e.g. fever, leukopenia, left-shifted neutrophilia) or not improving as expected

Supports approach of withholding antibiotics from aseptic patients; those not considered to be showing signs of systemic compromise.

** Don't forget the importance of client education on the issue of avoiding unnecessary antibiotic use! **

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