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How do you treat bacterial diarrhea in dogs?

Acute diarrhoea in dogs and cats: causes and faecal analysis

Acute diarrhoea is a common complaint seen in first-opinion small animal veterinary practice. Despite the fact that it is often self-limiting and likely to resolve with symptomatic treatment alone, antibiotics are frequently prescribed as part of the therapeutic management plan. In part one of this two-part article we will look at the common causes of acute diarrhoea, including infectious agents, and consider the use of faecal analysis. In part two, we will address when and why antibiotics are used in the management of acute diarrhoea, whether they are truly indicated and the potential adverse effects of antibiotic usage.

Diarrhoea is defined as an increase in frequency, fluidity or volume of faeces and is a common complaint in dogs and cats (Battersby and Harvey, 2006). Diarrhoea can occur secondary to disorders affecting the small or large intestines, or both (Hall, 2009). Localisation to the small or large bowel may not be possible in diffuse disease; it may also be less relevant in acute diarrhoea as biopsies are unlikely to be required and symptomatic treatment may not differ. Diarrhoea lasting for less than two weeks is generally described as acute (Chandler, 2002) and commonly resolves without the requirement for veterinary intervention (Hubbard et al., 2007). Therefore, animals are often presented at the vets due to owner concern or difficulty in managing the symptoms.

In terms of prevalence, one study found that 14.9 percent of dogs had experienced an episode of diarrhoea within the previous two-week period (Hubbard et al., 2007); another reported 28.6 percent of dogs visiting the vets had diarrhoea as their presenting complaint or had experienced an episode of diarrhoea within the previous month (Stavisky et al., 2010). Data from pet cats is limited, but one study showed that prevalence of diarrhoea in a rescue cat population was 11.9 percent (German et al., 2017).

Common causes of acute diarrhoea

Given the often self-limiting nature of acute diarrhoea, an exact aetiology is not always established. However, common causes of acute gastrointestinal upset include dietary indiscretion, dietary intolerance, sudden change in dietary composition, infectious organisms, anatomical abnormalities (eg intussusception), toxin exposure and metabolic or systemic disease (Table 1).

ProtozoaGiardia, Cryptosporidium, Coccidia, Isospora, Tritrichomonas foetus

BacterialSalmonella spp., pathogenic E. coli, Campylobacter jejuni, Clostridium difficile, Clostridium perfringens, Yersinia spp.

Viral – parvovirus, coronavirus, FeLV, FIV, distemper, rotavirus, circovirus, norovirus, canine adenovirus, feline torovirus, reovirus, enteroviruses, feline astrovirus


Dogs which have experienced a recent change of diet (scavenging or owner administered) or are fed a home-cooked diet, that live in a multi-dog household or have recently stayed in kennels, are at increased risk of diarrhoea (Stavisky et al., 2011). There are other potential causes of diarrhoea which may initially present as acute diarrhoea, but then develop into chronic diarrhoea. While there is some overlap with the causes of acute diarrhoea, an extensive list of differential diagnoses for chronic diarrhoea is beyond the scope of this article.

Infectious causes of acute diarrhoea

There are many potentially pathogenic organisms which may cause or contribute to the development of acute diarrhoea. Given that a healthy gastrointestinal microbiota consists of a diverse mix of microorganisms, including some which are potentially pathogenic, it can be difficult to determine whether the presence of certain microorganisms is of clinical significance in cases of diarrhoea. A North American study investigating the prevalence of enteric pathogens found that 30 percent of faecal samples from dogs with diarrhoea, and 22 percent of faecal samples from healthy dogs, contained potential pathogens (Hackett and Lappin, 2003).

Parasites and protozoa

Parasitic infections tend to be more common in younger animals (ESCCAP, 2018). Identification of worms or their eggs in the faeces of diarrhoeic animals is an indication for treatment with an appropriate endoparasiticide. While protozoal infections can be subclinical (Santín, 2013; Tysnes et al., 2014), diarrhoea may follow heavy infestations, infections in young or immunocompromised animals or infections alongside other pathogens or concurrent disease (Battersby and Harvey, 2006). Clinical manifestations of protozoal disease may require medical management.

Common infectious causes of diarrhoea in dogs and puppies

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There are many infectious causes of diarrhoea in dogs and puppies, and this is sometimes associated with other symptoms such as vomiting, lethargy and loss of appetite. A common step in the diagnosis of the cause of diarrhoea is analysis of a pooled stool sample. When collecting a stool sample from your dog it is important to try and collect three samples from three consecutive days to increase the chance of detecting an infection. Once the stool sample has been analysed by the lab, results may indicate a gut infection. In this article we will discuss some of the main gut infections in dogs, and what it means if your dog tests positive.

The main infectious causes for diarrhoea in dogs are: Campylobacter infection Parvovirus infection Giardia infection Cryptosporidium infection Salmonella infection Clostridium perfringens type A infection Can I get a stomach bug from my pet? When to see a vet? Further information Still have questions?

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The main infectious causes for diarrhoea in dogs are:

Campylobacter infection

Campylobacter species are a group of bacteria that can cause vomiting and diarrhoea in many types of animals, including people and dogs. Humans usually become infected via contact with raw poultry either by improper hygiene when cooking or eating undercooked meat, whilst dogs usually become infected by contact with contaminated faeces, water or food such as raw diets. There are many types of campylobacter organisms, some of which are found in normal dog faeces, and therefore the presence of campylobacter does not always indicate that this bacteria is the cause of your dog’s symptoms. You must be led by your vet, in deciding whether to treat this bacteria if it is found in a stool sample. It is also very important to maintain good hygiene if your dog has tested positive, to prevent infection passing to you or members of your household.

Parvovirus infection

Parvovirus causes a severe life threatening infection in dogs, with the main symptoms being vomiting, diarrhoea and lethargy. In the UK, dogs and puppies can be vaccinated against parvovirus as part of any routine vaccination protocol offered by your vet practice. It is unvaccinated dogs and puppies that are at risk of parvovirus infection. Parvovirus is diagnosed by detecting the presence of virus particles in your dog’s faeces. These particles will only be found if your dog has the infection, or if your dog has been recently vaccinated. Therefore, it is a fairly reliable way to diagnose an infection in dogs with symptoms consistent with parvovirus. There is no specific treatment, but patients often require supportive care, such as intravenous fluids to increase their chance of survival.

Giardia infection

Giardia is a small parasite that causes profuse watery diarrhoea in dogs, cats, humans and many other species. It is contracted by contact with infected faeces or contaminated ground. Symptoms include foul smelling watery diarrhoea, smelly gas, signs of general illness such as lethargy and decreased appetite, weight loss and vomiting. Treatment with a course of Panacur (fenbendazole) for several days is generally successful, though sometimes more than one course is required.

Cryptosporidium infection

Cryptosporidium is a small parasite that can cause watery diarrhoea in dogs, cats, humans and cattle. Transmission is via ingestion of infected faeces, water or food, and some life stages of the parasite can persist in the environment for many days. There are different species of cryptosporidium, one of which is often found in the faeces of cattle, therefore areas around farms have a higher risk of environmental contamination and infection.

Usually the infection will cause diarrhoea that will settle after a few days. However, sometimes the diarrhoea can be more severe, with animals needing hospital treatment, particularly if they are old, young or immunocompromised, for example if they are receiving steroid treatment for another condition. Treatment, if required, is usually with a course of an antibiotic such as tylosin.

Salmonella infection

Salmonella are a group of bacteria, of which a small number are extremely dangerous to humans, and therefore considered a major public health risk. They can cause vomiting and diarrhoea, and also acute septicaemia (typhoid), which kills humans in the UK every year. Dogs and cats usually contract salmonella by eating raw or out-of-date meat, or infected faeces. In dogs and cats, illness from salmonella is rare, but when it does occur it is often serious requiring hospitalisation and antibiotics. However, they can also carry salmonella species, without showing any symptoms, which can then lead to infection in humans of the same household, though this is rare.

Clostridium perfringens type A infection

Clostridium perfringens type A are a type of bacteria very commonly found in the gut of normal healthy dogs (around 80% of the UK dog population!) and rarely cause a problem. There are different strains, some of which produce toxins that target the gut (enterotoxin) and cause bloody diarrhoea, often with mucus. The bacteria produce these toxins in response to certain triggers, such as antibiotic treatment, sudden dietary changes or infection with another bug. Diarrhoea can range from mild to life-threatening, sometimes requiring treatment with antibiotics or other measures such as intravenous fluids. Proving that this bacteria is responsible for your dog’s diarrhoea is difficult: there are tests to establish whether your dog has the toxin-producing strain, and also tests to detect the toxin itself. A heavy growth of the toxin-producing bacteria, presence of the toxin and suspicious symptoms are usually sufficient to start treatment with antibiotics. However, in practice it is rare to use these diagnostic tests, as usually the patient has recovered by the time results are back from the laboratory.

Can I get a stomach bug from my pet?

It is very rare to contract an illness from your dog or cat, but the following advice will help protect you and your family:

  • Hygiene — WASH YOUR HANDS. Particularly after scooping up poo or touching your pet. Always wash your hands before meals or preparing food
  • Try not to let your dog lick your face, particularly if you are immunocompromised, pregnant, young, elderly or if your dog is unwell
  • If you are pregnant or immunocompromised, ask another member of the household to clean up your pet’s mess. It is important to collect any poo from your garden daily to prevent contamination building up
  • Stop your dog eating poo (coprophagia) — easier said than done! But using a muzzle or keeping them on a lead in high risk areas will help
  • Avoid raw diets in households with people at risk — immunocompromised, pregnant, young, elderly
  • Take your dog or cat to the vet promptly if they have vomiting or diarrhoea. Clean up any diarrhoea as soon as possible and try to use a disinfectant
  • If your dog or cat has been having diarrhoea, wash their back end in diluted Hibiscrub to remove any contamination from their coat. You can soak them in this solution for 10 minutes and then rinse thoroughly

When to see a vet?

  • Vomiting and/or diarrhoea
  • Diarrhoea with blood or mucus
  • Lethargy
  • Loss of appetite or a decreased appetite
  • Weight loss
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