BVSc (hons) DZooMed (Reptilian) MRCVS
BCG Veterinary Liaison Officer
First published in BCG Newsletter No.175 (January/December 2007)
Parasites are a common finding in tortoises and there are a few types that are of concern. It has often been said that tortoises require worming twice a year both upon awakening from hibernation and prior to going back in again. Questions regarding the need to worm tortoises have been a regular email enquiry and this article will hopefully address these questions more fully.
Worms can have a complex life cycle and infection occurs due to the ingestion of food contaminated with worm eggs. These develop into the adult worms after a varying amount of time and passage through internal organs. The adult worms then start producing infective eggs that are passed out in the faecal material. Two types of worms are a concern in tortoises; these are the oxyurids and the ascarids. Other nematodes have also been identified as a problem. Protozoan parasites are also commonly found but can be in elevated numbers secondary to other disease. Some protozoa can be identified due to cysts within the faeces others are motile parasites that can be detected in a wet preparation. Some do not cause disease but it can be difficult to differentiate between the types.
Treatment of parasites depends on the types identified and their numbers present. There are many ways to reduce the likely burden of parasites in tortoises without resorting to drug therapy.
Firstly given the life cycle removal of all faecal material is important to reduce contamination of the tortoise’s feet and shell. Bathing the tortoise in a separate container (cat litter trays are ideal) can stimulate the tortoise to pass faeces and urates in the water preventing contamination of its environment. This is also a good way to get a faecal sample provided it is scooped out quickly! Rinsing the tortoise of afterwards is required.
Contamination of the tortoise paddock or lawn is more problematic as the eggs can survive for longer periods and faecal material is difficult to remove quickly. Many owners only have the one dedicated area for their tortoise or a small garden (with favourite areas) and so parasites can build up over the years in these circumstances. Being able to move the tortoise pen around over at least a three year cycle can help reduce parasite build up. Testing the tortoise’s faeces for parasites and treating if required followed by a check to confirm you were successful prior to putting the tortoise onto a paddock is a wise move. This may delay the build up of parasites significantly. Even on contaminated paddocks treatment of new animals may reduce further adding to the worn burden. It may be in these circumstances that routine treatment is recommended, but in all cases examination of faeces to identify the most useful drugs to use is indicated.
Examination of faeces for parasites.
A wet preparation of faeces smeared on a microscope slide will enable a rapid result and an indication of large numbers of worm eggs or motile parasites. A faecal flotation is also useful. This is where a concentrated solution is mixed with a small amount of faecal material and the worm eggs float to the surface. The fluid from the top is then examined. These techniques suffice for routine examination.
Generally if worm eggs are identified on a floatation or wet preparation then it is best to consider treatment with an appropriate anthelmintic. There is a school of thought that a low level or oxyurid worms assists reptiles by churning up the faecal material and aiding digestion. Thus has yet to be proven to be of clinical benefit. In captivity a low worm count can easily become significant due to the tortoise infecting itself in a vivarium or outdoor pen or garden.
In clinical cases further testing may be required such as obtaining a definitive egg count, a concentration technique or special stains for protozoal parasites.
Treatment of faecal parasites.
Treatment of protozoan parasites must be performed by a veterinary surgeon after faecal testing. Historically many tortoise owners have treated their own animals with wormers such as oxfendazole or fenbendazole. Sadly it has come to light that these products are actually toxic if dosed inappropriately. There have been reports of the toxic effects in Fea’s Vipers and Hermann’s Tortoises to date but side effects in birds are well known. The toxic effects lead to bone marrow suppression and a reduced white cell count. The bowels can become oedematous and haemorrhagic. Regurgitation, diarrhoea, secondary infections and death can follow.
To prevent toxicity you firstly need an accurate weight of all the tortoises due to be wormed. Secondarily the effectiveness of worming has been shown to be increased by giving lower doses over a few days and also minimising the risks of a one off higher dose. Thirdly lower doses may still prove effective. Fourthly the faeces should be tested afterwards to ensure effectiveness.
Practically this can be difficult to perform as it involves daily stomach tubing. If this is not possible at home then daily trips to the vet are needed. Two faecal samples should be assessed to confirm, firstly a need for treatment and secondarily to confirm the effectiveness of the treatment.
Some tortoises can be problematic to stomach tube repeatedly (notably the leopards and horsfields) and in these a mild sedation may be needed to get the de-wormer in! Under no circumstances should an injectable wormer of the class avermectins be administered as this can lead to paralysis and death in tortoises.