Antibiotics and bacterial overgrowth in rabbits

We all know that we have to be incredibly careful when using antibiotics. With rabbits we use them with even more caution.

Posted: 15 December 2018

Antibiotics and bacterial overgrowth in rabbits


Antibiotic resistance is a big subject, and with more and more super-bugs emerging, we have a huge responsibility to make sure we choose our antibiotics carefully.

With rabbits we also have the added problem that many antibiotics can cause real and serious harm to the patient.

It’s therefore important to have safe and effective protocols of work to encourage all clinicians in the practice to work together. Some of the guidelines for choice of safe rabbit antibiotics are summarised below.

Identify the organism before prescribing

This is perhaps the most important stage of antibacterial treatment planning, and may be overlooked for various reasons. However it’s worth doing, so take a swab or biopsy and perform a culture and sensitivity test first. Explain to your client your reasoning.

Antibiotics – why are rabbits at risk?

The rabbit digestive system relies on a healthy, functional bacterial flora in the gut. With stress from illness and infections, these organisms can be adversely affected, and even without treatment, rabbits run the risk of bacterial overgrowth and gut stasis. However the danger increases when using antibiotics, as there can be an overwhelming destruction of healthy bacteria.

Disease occurs when an overgrowth of abnormal bacteria produce toxins which damage the caecum and colon, as well as affecting other body systems. Clostridium spiroforme, a bacterium normally identified in the lower intestinal tract in very small numbers, is the most common cause. Other organisms isolated include;

  • Clostridium difficile
  • Campylobacter spp.
  • Bacillus spp
  • Escherichia coli
  • Staphylococcus aureus
  • Salmonella spp.
  • Vibrio spp.
  • Clostridium perfringens

Antibiotic induced bacterial overgrowth

Antibiotics that alter the ‘normal’ bacterial population in the rabbit's lower intestinal tract are the problem. The chance of these antibiotics causing enteritis or enterotoxaemia is greater if they are given orally, rather than by injection.

Signs of bacterial overgrowth

Common signs of this rapidly developing problem, which are usually evident anything from 24 hours to 10 days after administrating the antibiotics, include;

  • Anorexia
  • Depression
  • Dehydration
  • Watery diarrhoea
  • Abdominal distension
  • Low faecal output
  • Abdominal pain
  • Gut stasis
  • Death

Which antibiotic to use?

Low-risk antibiotic – those less likely to cause a problem, such as bacterial overgrowth, include;

  • Enrofloxacin
  • Marbofloxacin
  • Metronidazole
  • Trimethoprim/sulphadiazine
  • Fusidic acid (ophthalmic ointment)

High-risk antibiotics – those that should be avoided as oral treatments in rabbits include;

  • Amoxycillin
  • Ampicillin
  • Cephalosporins
  • Clindamycin
  • Lincomycin
  • Penicillin (procaine)
  • Streptomycin

Occasionally used injectable antibiotics in rabbits

  • Amoxycillin
  • Cephalexin
  • Enrofloxacin
  • Trimethoprim/sulphadiazine

Follow the cascade

As with the use of all the drugs in animals, make sure you follow the rules of the cascade, as clearly defined by DEFRA  and the VMD

A high fibre diet will help

A diet full of simple carbohydrates will increase a rabbit's chance of developing enteritis when taking antibiotics, since Clostridium spiroforme needs simple carbohydrates to produce its toxin. However a diet high in fibre, such as grass hay, will reduce the chance of antibiotics upsetting the rabbit's flora. This is because the fibre increases the motility of the cecum and colon.

7 gems of advice to prevent antibiotic induced enterotoxaemia

Prevention of enterotoxaemia is best achieved by;

  1. Safe prescribing - only giving known “rabbit safe” antibiotics
  2. Safe route – know the difference between safe and high-risk oral antibiotics. Injectable antibiotics listed above are generally well tolerated and safe.
  3. High fibre diet – insist on optimal husbandry. Encourage low carbohydrate, high fibre diets with plenty of feeding hay. Rabbits should eat between 3% and 5% of their own body weight of hay per day. This can be a large volume, almost the same size of the rabbit itself. At Burgess Pet Care we’ve got several perfect products – see our range of feeding hay.
  4. Change slowly – never make sudden changes to the animal’s diet
  5. Low stress – rabbits are prone to gut complications if they are stressed.
  6. Monitor appetite – make sure a close eye is kept on body weight, body condition and food intake. Any major changes should be brought to your attention early.
  7. Avoid muesli – stress to your clients the consequences of feeding muesli style, high carbohydrate diets. There is plenty of evidence to show that this is harmful.