Yes they do – but not for the reasons that most people think!

Why do we worm our pets?

For dogs and cats, it is essential to worm regularly to kill nasty internal parasites. These include intestinal roundworms and tapeworms, that live in the gut eating the animal’s food and sometimes causing weight loss or diarrhoea; and lungworms, that affect the heart and lungs, and may (in dogs) even be fatal. Regular worming prevents these creatures from building up to the numbers and levels of maturity that would be likely to lead to disease.

Don’t rabbits get worms too?

Wild rabbits may suffer from a range of intestinal parasites; however, these almost never cause problems in domestic bunnies. In general, it is completely unnecessary to treat worms in rabbits as a regular preventative medicine – they just don’t get enough of them to be worth it!

Hang on, so why do I need to worm my rabbit then?

Because of another parasite, called Encephalitozoon cuniculi, which can cause terrible suffering or even death. Interestingly, for some reason the parasite seems to be more common in domestic, pet and farmed rabbits than in their wild cousins – studies regularly find no evidence of infection (let alone symptoms) in wild animals, but as many as 52% of pet bunnies incubating or exposed to the disease.

What is it, and why does it have such an unpronounceable name?

Well, we’d usually refer to it as E. cuniculi, if that helps! The name, roughly translated, means “brain-living creature of rabbits”, which is quite a good description, actually. It’s a protozoan parasite (a bit like an amoeba) that attacks the brain and kidneys.

What are its symptoms?

The most common symptoms are those of progressive brain malfunction, as the rabbit’s immune system hunts down the parasites, causing massive local inflammation. In general, these progress in roughly the following order:

• Head tilt, which becomes gradually more and more dramatic
• Unsteadiness and loss of balance
• Muscle tremors or shaking
• Weakness of the back legs, gradually progressing to paralysis

However, the parasites do not just invade the brain, but also attack the kidneys. Typical symptoms include increased urination, excessive thirst, and urinary incontinence. Later, kidney failure may occur, leading to dehydration, a metallic smell on the breath, collapse and death.

Occasionally, their eyes are also infected, leading to cataracts (grey or milky, cloudy pupils) or uveitis (inflammation of the front part of the eye, which may cause pus to form inside the eyeball, cloudiness of the front of the eye, and usually severe pain and sensitivity to light).

If left untreated, the disease is often fatal, either due to terminal brain damage, massive seizures, or complete kidney failure.

How is it spread?

The parasites are transmitted in urine – so other rabbits coming into contact with liquid, or aerosolised (e.g. from spraying or over-enthusiastic cleaning) urine are at risk of contracting the parasites.

What animals does it affect?

Mainly rabbits, but it has also been reported to infect guinea pigs, dogs and cats (although this is very rare!). More worryingly, it is not uncommon for it to infect humans, as it is an important zoonotic disease – especially as we’re usually the ones cleaning up after the incontinent carrier!

So why use wormers to kill it? Why not antiprotozoal drugs?

The fenbendazole wormer is much safer than most anti-protozoal drugs in rabbits, and is just as effective against this particular parasite.

How often should I treat my rabbit to prevent infection?

The current advice is to treat them 2-4 times per year; this will kill any parasites in their system at that time, and it usually takes more than 3-6 months for new ones to multiply enough to cause disease.

If you think your rabbit might have E. cuniculi, or any other disorder, make an appointment to see one of our vets as soon as possible – rapid diagnosis and treatment minimises the severity of the infection, and the degree of long term damage.