• Small type of nematode (roundworm) commonly found in lizards and tortoises
• Rarely cause symptoms
• Medical treatment rarely indicated

Pinworms (Oxyurids) are small nematodes (roundworms) commonly found in herbivorous, insectivorous and omnivorous reptiles. We encounter these parasites frequently in tortoises, geckos and Bearded/Rankin´s Dragons, to name a few. There are many different species (i.e. Pharyngodon sp.) and appearances found in reptile faecal samples.

These parasites are found in different animal groups, including humans (human pinworm: Enterobius vermicularis) reptiles and rabbits, amongst others. Pinworms are host specific and therefore, dogs, cats and other pets do not play a role in the spread of human pinworms. Reptilian pinworms do not pose a threat to humans (not zoonotic), as in this case they are considered reptile specific.

These parasites are more frequently found in herbivores and insectivores. Studies have shown that around half of all tested herbivorous and insectivorous lizards and tortoises are positive for pinworm eggs.

Adults live in the distal part (large intestine) of the intestinal tract where they feed on ingesta. Unlike other roundworms they do not migrate through body organs to mature and do not possess buccal organs to allow them to attach themselves to the intestinal mucosa. 

The life cycle is relatively simple and is direct. This means that the eggs are passed through the intestinal tract with the faeces and they are ingested by the definitive host; in this case, the reptile.

The infectious form is the egg, where a larvae is frequently visible. These eggs may remain infective in the enviromenent for long periods of time, depending on factors such as temperature and humidity.

It is presumed that insects may ingest the eggs and when the reptile consumes the insect, these can be passed on to the reptile. Insect and rodent pinworm eggs may be found in reptile faeces (i.e. reptile that ingests a mouse or a cricket). These would be classed as reptile pseudoparasites, meaning that they would simply "transit" or" pass through" the digestive tract (as they are pinworm eggs of insects or rodents). 

In faecal samples we often encounter adults, larvae and eggs. The pinworm burden may be associated with the level of eggs found in a faecal sample. Levels may be reported based on how many eggs are found in a faecal sample and counts may also be performed. In day to day practice a faecal sample may be examined without an "actual egg count". Experienced exotics vets will often examine a sample placed on to a slide without performing a "count". This is a quick and cost effective. This way, the vet will have an "idea" of levels from that one sample in time.

 

There is a single reference published in the United Kingdom for pinworm egg levels in tortoises, where levels were calculated via a specific counting method, a modified McMaster egg count. The multiplying factor will vary between animal species and therefore, depending on this multiplying factor, actual counts may vary from lab to lab. This is why levels may vary depending on where the sample was tested. Pinworms are the only nematodes in reptiles where a reference range is available. To be able to class numbers as low or high, the counting system must be exactly the same as that performed in the study.

Behavioural causes can often be the most challenging to diagnose and is often a diagnosis of exclusion. This may happen in species that hibernate, brumate or aestivate where they may be displaying a normal physiological behaviour, influenced by multiple factors, including husbandry conditions. It is very important not to assume that the problem you are seeing is a behavioural problem, unless it is a behavioiur that is completely expected or repeated every year, ie brumation in a Bearded Dragon. Some reptiles do suffer from relocation stress, although most species of reptiles we commonly encounter so not suffer "directly" from relocation stress, albeit they may suffer indirdectly i.e. coccidiosis in Bearded Dragons that has been rehomed. In these cases it is thought that the increased stress may exacerbate the underlying condition (coccidiosis), and therefore start to show symptoms of ill health.

The clinical approach has changed over the last decade. This is due the following: a) pinworms are currently not considered to be as pathological as previously thought and b) the poptential risk of adverse effects of medications used to treat these parasites.

The proposal that these parasites may be beneficial in reptiles has yet to be proven, although this has been proven in populations of amphibians that carry pinworms.

Depending on the individual circumstances, exotic animal veterinary surgeons may decide to treat pinworms in reptiles or monitor the levels. A number of factors should be taken in to account for the decision making: past history, life stage, current health status and symptoms.

The levels of these parasites can serve as an important environmental hygiene marker and possibly an overall health status.

Now that we have a better current understanding of these parasites, fewer reptiles are treated. Medications frequently used are benzimidazoles (i.e. Fenbendazole, Mebendazole, Oxfendazole). More recently, topical spot-on products have also been used successfully.

A faecal egg count reduction test (FECRT) or "retest" is usually advised following treatment. This allows to see the effectiveness of the medications and to have a baseline starting point ready to compare the next time around. A retest is generally recommended 2-4 weeks after treatment has been administered, although the percentage of egg reduction is time sensitive depending on the type of drug used to treat these parasites. Studies have shown that fenbendazole can take 4 weeks to achieve a 100% FECRT.

Anecdotally, we have found that reptiles kept in closed environments with no contact with other reptiles, will often have a negative egg count following treatment, although these may still be present and a future faecal examination may be positive. 

Always watch out for red flags which may include non-specific symptoms like anorexia, weight loss, lethargy, and contact your exotics veterinary surgeon for advise.

A list of exotic animal veterinary surgeons can be found here by selecting "Specialist in..." OR "Advanced Practitioner in..." ZOOLOGICAL MEDICINE:

Giannetto S, Brianti E, Poglayen G, Sorgi C, Capelli G, Pennisi MG, Coci G: Efficacy of oxfendazole and fenbendazole against tortoise (Testudo hermanni) oxyurids. Parasitol Res. 2007, 100: 1069-1073. https://pubmed.ncbi.nlm.nih.gov/17120044/

Hallinger M.J., Taubert A., Hermosilla C., Mutschmann F. Occurrence of health-compromising protozoan and helminth infections in tortoises kept as pet animals in Germany. Parasites Vectors. 2018;11:352. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6006665/

Hedley J, Eatwell K, Shaw DJ (2013) Gastrointestinal parasitic burdens in UK tortoises: a survey of tortoise owners and potential risk factors. Veterinary Record 30;173(21):525. https://pubmed.ncbi.nlm.nih.gov/24158320/

Hedley J, Survey of Gastrointestinal Parasites in Tortoises in the UK. http://knowledge.rcvs.org.uk/document-library/diplomas-dzm-12-1/

Efficacy of a Topical Formulation Containing Emodepside and Praziquantel (Profender®, Bayer) against Nematodes in Captive Tortoises. https://researchonline.rvc.ac.uk/id/eprint/11501/1/11501.pdf

Giannetto S, Brianti E, Poglayen G, Sorgi C, Capelli G, Pennisi MG, Coci G: Efficacy of oxfendazole and fenbendazole against tortoise (Testudo hermanni) oxyurids. Parasitol Res. 2007, 100: 1069-1073. https://pubmed.ncbi.nlm.nih.gov/17120044/

Hedley J, (2013). Survey of Gastrointestinal Parasites in Tortoises in the UK. 

http://knowledge.rcvs.org.uk/document-library/diplomas-dzm-12-1/

https://wsava.org/wp-content/uploads/2020/01/Clinician-s-Brief-February-2018-TP-Pinworm.pdf

Tang, P. K., Pellett, S., Blake, D., & Hedley, J. (2017). Efficacy of a Topical Formulation Containing Emodepside and Praziquantel (Profender®, Bayer) against Nematodes in Captive Tortoises. Journal of Herpetological Medicine and Surgery, 27(3), 116-122.

https://researchonline.rvc.ac.uk/id/eprint/11501/1/11501.pdf