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Protozoan infections in Chelonians.

A C Highfield


Both flagellate and ciliate protozoan organisms are frequently detected in chelonians. In most cases, they appear to cause their hosts little or no distress. From time to time, however, their populations reach pathogenic proportions and should this occur the consequences can be serious, ranging from acute diarrhoea resulting in dehydration (with the risks of renal damage that implies), to severe irritation of the intestinal walls and, in chronic cases, to a complete loss of normal digestive-tract flora. Where this occurs, the animal may continue to feed voluntarily, but still suffers inanition as a result of an inability to digest and metabolise the food consumed.

Flagellate organisms:

The most common organisms encountered are flagellates of the order Trichomonadida. We have encountered them frequently in Testudo graeca, Kinixys homeana, Kinixys belliana , Geochelone pardalis, Manouria (Geochelone) emys, Malacochersus tornieri, Testudo kleinmanni, Agrionemys horsfieldi, Geochelone elegans, Testudo marginata and Chelonoidis carbonaria. Whist we have seen them in Testudo hermanni they do not appear to be either as common (or pathogenic) as they can be in T.graeca. In captive collections they can easily attain epidemic proportions as they are extremely easy to spread by careless handling or poor hygiene practices. Symptoms of flagellate infection include poor appetite, diarrhoea, dehydration and (in the later stages) the passage of quantities of undigested food. Faeces sample viewed microscopically will reveal large quantities of small but highly motile organisms. Sometimes several successive samples need to be viewed, as occasionally even in a highly infected animal a clear sample may be passed.
Samples may be prepared for microscopic examination in various way, but the easiest and quickest are direct smears (useful where urine samples are to be viewed) and saline suspension which is more appropriate to faecal material. A high power microscope is not necessary, and excellent results in this application can be obtained from instruments of modest cost.
Treatment where necessary is usually accomplished by oral dosing with Metronidazole (e.g 'Flagyl', May & Baker) via stomach tube. We have found that the standard suspension (Benzoylmetronidazole) can induce vomiting in some species (mainly T.hermanni and Kinixys Spp. possibly due to its Ph balance). We therefore suggest suspending the drug in its tablet form in sterile water; to date no adverse effects have been noted if delivered in this way. Various dosing regimes have been suggested and used with more or less equivalent success. Jackson (1977) suggests 160mg/kg every 24 hours for 3 days. Donaldson (1975) suggests a single large dose of 275mg/Kg. Zwart (1987) suggests 25mg/Kg over 10 days. We have found all regimes effective in most cases, with the persistent and recurring cases responding to a combination of a large initial dose (275mg/Kg) followed by 4 days at 160mg/Kg. Some concern has been expressed regarding possible neuromuscular blocking effects of large doses in excess of 400mg total. This remains a possibility, and therefore doses in excess of this figure should be used with extreme caution. Certainly, in a very large animal ( e.g, an 18kg G.pardalis) a dose of 400mg is completely ineffective in eliminating pathogenic concentrations of flagellates and higher doses are almost always required if the organisms are to be brought under control.
The most serious effect of a prolonged flagellate infection of pathogenic proportions is the severe 'scour' or depletion of natural G.I tract flora which usually results. If left untreated, death can result from a combination of inanition, dehydration and cellular damage to the intestinal walls. Treatment consists in simple cases of oral dosing with a metabolic stabiliser such as Vetrumex (Willows Francis Veterinary Ltd.) or even natural (live culture) yoghurt i.e, the same program as for antibiotic induced scour. This is generally effective within 6-10 days, the faeces gradually returning to normal. Very severe and chronic cases require a different approach. A sample of faeces should be obtained from another tortoise of the same species. This should be carefully screened for pathogenic organisms, liquidised and cultured in a suitable growth media (Vetrumex is suggested) for several hours at 28ĂC. This should then be delivered via stomach tube to the affected animal. The live bacteria present will serve to replace those destroyed and will help to re-establish normal digestive activity. Sometimes several attempts are necessary, but to date every case (including the most severe) has responded extremely well to this therapy. The normal transit time through the G.I tract of a herbivorous chelonian is measured in tens of days. Where 'Sterile Gut Syndrome' exists, as little as 24 hours may be experienced. To enable the live bacterial culture to take effect, this enhanced transit period can be reduced by stomach-tubing a quantity of finely ground plant cellulose matter - powdered rabbit pellets hydrated with sterile water have been used with success.
It is extremely important to stress that flagellates are not necessarily pathogenic, and indeed may have a useful function in aiding the digestion of cellulose material. The decision as to whether or not treatment is required must reflect the balance between possible further disruption to the gut flora as a result of the anti-bacterial effects of Metronidazole, and the risks of damage to the intestine which may be incurred by leaving the tortoise alone apart from gentle support therapy e.g provision of adequate fluid and agents to promote the regeneration of natural flora. Many cases, if left untreated, do eventually subside and the flagellate population returns to normal of its own accord. Only where genuinely pathogenic populations are present is treatment really necessary or advisable.


Infection of the renal-urinary system by the flagellate organism Hexamita parva presents a serious danger. Symptoms include voiding of unusually concentrated urine, often smelling strongly of ammonia. In severe cases, this may be tinged with blood. The animal may also display signs of dehydration, and may drink excessively. In chronic cases, the tortoise will have a wasted, debilitated appearance and may lack muscular retractive power particularly of the back legs. The condition is highly infectious, and suspected cases should be isolated immediately and veterinary assistance sought urgently. If untreated, death will eventually result from necrotic degeneration of the kidneys.
We have encountered several cases of Hexamita parva infection, and it seems particularly prevalent in G.pardalis. Urine samples from infected animals viewed microscopically will reveal large quantities of the organisms, which are much smaller than Trichomonads, typically measuring 8.03um X 4.79um (Zwart & Truyens,1975). The recommended treatment consists of oral administration via stomach tube of Ronidazole Duodegran) 10mg/Kg daily for 10 days,or Metronidazole (Flagyl) over the same period at 25mg/Kg (Zwart,1987). We have, however, noted a quicker response to the Metronidazole if the first dose of the course is delivered at 260mg/Kg and thereafter at the lower dose for the remaining period. Constant urine examinations should be undertaken throughout the treatment period, and thereafter at weekly intervals for several months and any recurrence must be treated immediately.
During treatment renal damage can be limited by supplying a kidney 'flushing' agent such as Hartmann's Solution (compound sodium lactate intravenous infusion B.P) orally at 5% of total bodyweight daily.(N.B: This can also be useful when dosing with aminoglycoside antibiotics where nephro-toxicity is a potential problem).


This organism, which is large, slow moving and very easy to detect microscopically is frequently encountered, although to what extent it is pathogenic seems unclear at this stage. In pigs, Balantidium coli has been linked to systemic abscessing, and one T.graeca detected did have abscessing of a front leg. Whether this was associated with the the organisms subsequently detected in his faeces samples is not known . We have observed Balantidium Spp. in T.hermanni, T.graeca, G.pardalis, M.tornieri and Kinixys homeana. It also occurs in Galapagos and Indian Ocean giant tortoises. Paromomycin ('Humatin',Parke-Davis & Co.,West Germany) has been found efficacious at a dose rate of 25mg/Kg repeated after 7 days but is extremely difficult to obtain in the U.K. Lacking reliable sources for this drug, Metronidazole was employed and produced equally good results. A single dose of 260mg/Kg cleared the organisms permanently in all 17 cases so far encountered without adverse side effects.


Ernst and Nichols (1974) report finding this ciliate in in G.carbonaria and G.elegans imported into the USA. To date we have not encountered it in this country. It is of doubtful pathogenicity.

Entamoeba invadens:

We have encountered this organism in chelonia, although there was no evidence of any pathogenic effect. Frank (1984) suggests that chelonians may be healthy carriers of the organism which is highly lethal in other species. This is sufficient reason for not permitting chelonia to share accommodation with other reptiles, especially snakes and lizards, as the potential for mutual cross-infection with dangerous pathogens is considerable. Terrapins and aquatic chelonia in general are particularly likely hosts for E.invadens.


Protozoan organisms can represent a major hazard to captive collections of chelonia but not all occurrences are pathogenic, especially where Trichomonads are concerned. Good hygiene is the best prevention and all cages should be kept scrupulously clean with adequate attention paid to food handling and feeding routines. Areas which have housed infected animals should be thoroughly cleansed with povidone-iodine and dilute formalin solution. Effective treatment exists, but early detection and diagnosis is the key to successful treatment. The onus is on keepers to regularly screen both urine and faeces samples for evidence of pathogenic agents, and to seek veterinary treatment at the earliest possible opportunity where pathogenicity is suspected. Delay can result in permanent damage, especially where Hexamita organisms are involved.

Important note: This information is provided for keepers reference only. The necessity to consult a qualified veterinary surgeon with extensive experience of reptile medicine in all cases cannot be over emphasised. The drugs referred to are Prescription Only Medicines and should only be administered under qualified veterinary direction.


  • Donaldson, M., Heyneman,D., Dempster, R. and Garcia, L., (1975) American Journal of Vet. Res. 36:807-817
  • Ernst, C.H., and Nichols,J.N., (1974) Internal Ciliates of Tortoises, Brit.J.Herpetology, 5:3 450-451.
  • Frank,W (1984) in Hoff,G.L., Fryer F.L., and Jacobson, E.R. Diseases of Amphibians and Reptiles, Plenum Publications.
  • Jackson,O.F., (1977) Journal of Small Animal Practice, 18:479-491.
  • Zwart,P., (1977) Testudo (Journal of the British Chelonia Group), 2:5 1-14
  • Zwart,P. and Truyens, E.H.A (1975) Vet.Parasit, (1), 175-183