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Author: Stephen J. Divers B.Sc.(Hons), CBI0I. MiBiol, BVetMed, MRCVS

Introduction

Renowned reptile vet, Stephen J. Divers B. Sc. (Hons), gives us an insight into a condition of great concern that may be present in collections the world over. He explains what it is, how it is transmitted from host to host, how it affects the inflicted animal, how it may be diagnosed, its treatment or otherwise (as explained in the article) and what to be on the look out for.

Cryptosporidia

WHAT IS IT ?

Cryptosporidia is a protozoan (single cell) parasite, and for the scientists among us has been classified as follows;


Phylum: Apicomplexa
Subclass: Coccidiasina
Suborder: Eimeriorina
Genus: Cryptosporidia
Species: C. serpentis

This parasite causes disease in lizards and snakes, and was first documented back in the 1970s. For this article I shall concentrate on snakes as the presentation of the disease does vary between snakes and lizards. The other thing to remember is that it appears the snake disease may only be caused by C. serpentis and, therefore, Cryptosporidia from other animals, including humans and rodents, may not pose any threat, although this has yet to scientifically proven.

WHAT DOES IT DO ?

It is generally accepted that a Cryptosporidia infection is not just a simple case of bug meets snake and snake gets sick. Some snakes exposed to infection may show no signs of illness, whereas others may show a transient diarrhoea for 2-4 weeks and then recover, although some may act as carriers and shed the parasite for a year or more. However, immunosuppressed* individuals appear to be worse affected and the disease often takes hold with fatal results.

* Immunosuppressed animals (see list) have a substandard immune system which makes them more prone to infections:

  • very young or very old snakes
  • stressed snakes (wild imports)
  • snakes weakened by concurrent disease or other infections
  • snakes given steroid drugs

The mid-body swelling in this corn snake is a clear indicator of Cryptosporidiosis.
A close-up of a corn snake, showing the mid-body swelling caused by Cryptosporidia serpentis. The swelling is actually caused by the swollen stomach walls.

Boa constrictor in the advanced stages of the diseasee. Note the poor body condition, extreme weight loss and poor conformation.
Burmese python showing signs of poor body condition and generalised ill health die to Cryptosporidiosis.


HOW IS IT CONTRACTED ?

As with most protozoan infections, Cryptosporidia is acquired by exposure to sporulated oocysts in contaminated food and water and unhygienic vivaria. This microscopic parasite is tiny, with each oocyst measuring only 4.0-8.0 mm in diameter, and containing four sporozoites, so you certainly cannot see it with the naked eye!

Although the life-cycle is not completely understood in reptiles, it is believed that the ingested oocysts invade a small number of endothelial cells lining the stomach wall. The Cryptosporidia parasite naturally inhabits the snake’s intestinal tract, living just within the surface of these endothelial cells. Once within the cell, this protozoan can replicate, damaging the cell and causing irritation The life-cycle is completed by the production of oocysts which may immediately re-infect other endothelial cells within the stomach, or they may pass out in the faeces to contaminate the environment and infect other snakes. In other words, this parasite has a direct life-cycle and does not need an intermediate host, or even have to leave the snake, to reproduce. These infective oocysts can also be spread to other snakes in other vivaria on the hands of the snake-keeper, on snake hooks and in contaminated water bowls.

WHAT DOES IT DO ?

As these parasites invade and reproduce within the stomach wall cells they cause irritation. Initially, this irritation may cause fairly non-specific signs, including anorexia, lethargy and weight loss. As the disease progresses in snakes, the stomach lining starts to thicken, leading to an inability to retain food within the stomach and hindererd digestion, of which the result is frequent regurgitation. In many cases as the snake looses weight and the stomach continues to thicken a mid-body swelling becomes noticeable. As the disease progresses, the snake continues to lose weight and usually dies of emaciation and starvation. Recovery in clinically affected snakes suffering from regurgitation, weight loss and stomach thickening is very unlikely.

HOW IS IT DIAGNOSED ?

I start to get very worried about the possibility of Cryptosporidiosis in snakes whenever regurgitation is accompanied by;

  • lethargy and depression
  • slimy, pale-grey faeces
  • extreme and continued weight Ioss
  • mid-body swelling
  • failure to respond to conventional medication


The mid-body swelling in snakes is very strong evidence for Cryptosporidiosis . For a definitive diagnosis I anaesthetise the snake and pass a thin, flexible fibre-optic endoscope down the oesophagus and into the stomach to have a good look round and take a stomach biopsy. In positive snakes the biopsy will show the parasites within the stomach lining. For snakes that do not have the mid- body swelling I will usually look for the oocysts in stained smears made from faecal material, stomach washings or regurgitated food.

Above: A high power microscope picture of a stained faecal smear. The round, red objects are the Cryptosporidia oocysts.

The normal stomach lining of a python. Note the normal folds of the stomach lining. In cases of Cryptosporidiosis these folds enlarge and swell dramatically.

Endoscopic view of a stomach infected with Cryptosporidia. In this case note the huge stomach folds and the dramatically reduced stomach lumen.

Endoscopic view of a normal snake stomach. Note the small stomach folds and large lumen of the stomach.

It is not surprising that snakes cannot digest their food and regurgitate with this disease. Modern technology also enables the taking of stomach biopsies through the endoscope thereby avoiding major surgery.

HOW IS IT TREATED ?

Just in case you thought things could not get any worse, it can, because, to date, there is no effective treatment. Some vets have reported success with various sulphonamide or trimethoprim sulphonamide drugs, but I have not found them to cure, or even stop the progression of the disease. Individual snakes can often be stabilised, at least temporarily, with intensive nursing, including administering fluids and stomach-tubed liquid foods, such as Hills a/d. However, when dealing with large collections, and given the grave prognosis and likely spread of infection, I presently recommend that any confirmed cases of cryptosporidiosis are euthanased to prevent the spread of this horrible wasting disease.

What to do

Keep a close eye on your snakes and operate a six-month quarantine system for all new additions to an established collection.
Record the following;

  • weight (weekly for juveniles, monthly for adults)
  • accepted and refused feeds
  • regurgitation (including time from feeding)
  • diarrhoea (colour, consistency)



If you have a suspicion of cryptosporidiosis isolate the snake immediately and operate very strict hygiene practices. Arrange a consultation with your local reptile vet and remember to take any recent diarrhoea or regurgitation samples with you.

Editors Note: Reproduced with kind permission of the Reptillian Magazine
This site has information on the following genera of Ratsnakes ... Spilotes, Spalerosophis, Ptyas, Zamenis, Elaphe, Rhinechis, Senticolis, Pseudelaphe, Pantherophis, Bogertophis, Orthriophis, Gonyosoma, Oreocryptophis, Oocatochus, Euprepiophis, Coelognathus, Archelaphe