Osteomyelitis in a Hermann’s tortoise

18 Osteomyelitis in a Hermann’s tortoise




INITIAL PRESENTATION


Nail loss in a Hermann’s tortoise.



Introduction


Reptilian metabolism is slower than that of mammals. Pathological processes therefore usually develop (and heal) much more slowly, resulting in a longer course of the disease and treatment. An accurate diagnosis aids greatly in selection of treatment, which is often of necessity protracted.



CASE PRESENTING SIGNS


A 53-year-old male Hermann’s tortoise (Testudo hermanni) (Box 18.1) presented with loss of nails (onychomadesis) from both forefeet.



BOX 18.1 Ecology of Hermann’s tortoises



• Hermann’s tortoises have a wide distribution throughout the Mediterranean and Eastern Europe.

• They are generally solitary, except during the breeding season.

• The IUCN has identified Hermann’s tortoises as Lower Risk/Near Threatened, although the Western subspecies Testudo hermanni ssp hermanni is classed as Endangered. Hermann’s are listed with other Testudinae on CITES Appendix I, restricting their trade.

• They live in evergreen Mediterranean oak forest (though this habitat is now rare), coarse arid scrub and hillsides.

• In captivity, the species tolerates an arid to moderately damp environment, but requires plenty of warmth and sun. Heating and UV-B lighting should be supplemented in more temperate climes.

• Their free-ranging diet is herbaceous and succulent plants.

• Captive individuals should be fed a wide range of weeds and green vegetation. Edible plants include: dandelion, sow thistle, plantains, vetch, mallows, clovers, grapevine leaves, succulents (e.g. Sedum spp and Aloe vera spp), Hibiscus spp, Rubus spp (raspberry and blackberry), dead-nettles and bindweeds. When available, edible flowers from the above plants as well as honeysuckle are appreciated. Although fruits are well accepted, only small quantities (<5% of the diet) should be allowed. Salads are a poor substitute for the free-ranging diet. Animal protein (e.g. dog/cat food) should not be fed.

• Tortoises may live up to 100 years.


Husbandry


The tortoise had been in the owner’s family in Scotland for over three decades. During the previous 20 years, he had been housed in an outdoor pen during the day and in a greenhouse overnight. At the time of presentation, he was housed mainly indoors, roaming in the house during the day and returned to a plastic container measuring approximately 1 × 0.25 m overnight. The substrate in the indoor enclosure was a mixture of newspaper and towel. An outdoor pen was used for daytime housing during good weather.


A heat lamp was present, but used only intermittently. The owner did not measure the environmental temperature. No supplemental UV lighting was provided.


The tortoise’s diet was mainly mixed salad (lettuce, tomatoes and cucumber) and fruit (pears and satsuma oranges), and he also had access to various weeds (e.g. dandelions) in his outdoor pen. Water was provided in a shallow bowl, and the tortoise was bathed weekly to encourage drinking.


The tortoise had previously been hibernated, but not during recent years.



Case History


Two years prior to presentation, the tortoise had sustained trauma to both forefeet from rough substrate, resulting in small abrasions that were treated with topical antiseptic solution (povidone–iodine) and appeared to resolve.


More recently, the tortoise had lost some nails from the forefeet. The owner did not notice any other abnormalities. No changes were noted in appetite or activity.



Clinical Examination


Mediterranean species of tortoise are relatively easy to examine conscious, and the tortoise received a full clinical examination. Findings were as follows:


• Bright, alert and reactive

• Good body condition with well-muscled limbs and no evidence of oedema. Weight 1.95 kg, with a straight carapacial length (SCL) of 18 cm

• No ocular, nasal or oral lesions. Mucous membranes pink, with no evidence of stomatitis

• Carapace and plastron unremarkable

• Limb examination:
• No obvious lameness

• Forelimbs: firm swellings of both feet, loss of all nails, skin smoothed with some scale loss, some inflammation and erythema ventrally on distal limbs, feet swollen and firm

• Hindlimbs: obvious stifles, possibly abnormally swollen. Nails present and no swellings on feet.


DIFFERENTIAL DIAGNOSES


The differentials for limb swelling were:


• Infection – abscess or osteomyelitis, aetiological agents may include bacteria (including mycobacteria) and fungi

• Granuloma

• Intra-articular gout

• Trauma, e.g. fracture, dislocation, soft tissue injury

• Haematoma

• Parasitic cysts

• Neoplasia (may be associated with pathological fracture)

• Scar tissue.


Initial Case Work-Up



Blood sample


Since two limbs were affected and systemic disease is common in ageing tortoises, haematology and biochemistry tests were performed as a general health check (Box 18.2). The sample also gave information regarding some of the differential diagnoses listed above (Table 18.1):


• One would expect to see changes in the white cell picture if local or systemic infection were present.

• Hyperuricaemia would be present in cases of gout.

• Elevated creatinine kinase may be seen in cases of trauma, although possibly not in chronic disease.


BOX 18.2 Phlebotomy in tortoises


Jugular vein



• The jugular vein should be accessed if possible (Fig. 18.1). It is less likely to be diluted by lymph than other commonly used sites such as the dorsal coccygeal vein (which is difficult to obtain a large sample from) and the sub-carapacial (or subvertebral) venous sinus, and a sufficiently large volume should be readily obtainable.

• An assistant holds the tortoise, including gentle restraint on the forelimbs to keep them away from the neck area during the procedure.

• The phlebotomist grasps the head – the author prefers to extend the neck by grasping behind the head laterally (caudal to the tympanic membranes), but then holds the head dorsally and ventrally during venepuncture.

• The skin on the lateral neck is surgically prepared.

• The assistant puts pressure at the base of the neck to raise the vein.

• The vein runs superficially in a line from the tympanic membrane to the base of the neck.

• A 23–25 gauge hypodermic needle is inserted at a shallow angle. A 2 ml syringe is sufficient for most tortoises, although care should be taken not to collapse the vein with excess suction.

• Pressure is applied to the site for a few minutes after sampling to reduce the risk of haematoma formation. If the tortoise is strong and the neck cannot be extended for this period of time, use a large ball of cotton wool inserted between the neck and limb to provide pressure.

image

Figure 18.1 Venous access to the jugular vein in a tortoise (here, to induce general anaesthesia using alfaxalone).



Table 18.1 Hermann’s tortoise blood results (with reference ranges for comparison)

image

Hyperproteinaemia (in particular hyperalbuminaemia) is often seen in dehydrated tortoises (usually in association with haematological changes such as elevated haematocrit), or in females associated with normal reproductive activity (e.g. vitellogenesis). Hyperglobulinaemia may reflect chronic inflammatory activity. The mild hypoglycaemia may have reflected a reduction in food intake during the autumn months (the sample was taken in October). Other reasons for reduced blood glucose include anorexia, malnutrition, septicaemia and hepatopathy. The hyperkalaemia is commonly artefactual in samples posted to external laboratories for analysis, associated with haemolysis during the delay in processing. Elevations in potassium may be seen in cases with renal failure (usually with concurrent hyperuricaemia).


Red cells showed marked anisocytosis, poikilocytosis, polychromasia and hypochromia. Several red cells also showed multiple inclusions that may have been atypical basophilic stippling. Although anaemia was not present, these red cell changes suggest chronicity in the disease with a regenerative response (which occurs slower in reptiles (up to 4 months) than in birds or mammals (within 1 week)). Leucocytosis with heterophilia commonly suggests infection or inflammation, although the smear report did not show the presence of any toxic changes in white blood cells. Other differentials for heterophilia are trauma, stress and neoplasia.



Radiography


The tortoise was amenable to positioning and the sites of interest on the limbs were distal, so radiography was performed conscious. Initially dorso-ventral radiographs were taken of the distal limbs (Fig. 18.5a,b).


At the time of initial presentation, severe bone lysis was present in both forefeet. Both showed a focal moth-eaten appearance of the digits, metacarpal and carpal bones. There was also destruction of the left distal ulna. The destruction was more extensive in the left foot, with almost complete loss of the digits, radial aspect of the carpal bones and distal ulna. In the right foot, the destruction mainly affected digits II–V, and some focal lesions were visible in the carpal bones. Despite concerns over stifle swellings, no obvious destructive changes were identified on radiographs of the hindlimbs. Bone density in the tortoise was good (i.e. there was no evidence of metabolic bone disease).



Fine needle aspirate (FNA)


After surgical preparation of the skin, an FNA was taken from the left foot of the tortoise. A small amount of haemorrhagic material was obtained, and sent for culture (aerobic and anaerobic bacteriology, and fungal culture). The owner was warned that this small sample may not be representative of the lesion, and that more invasive procedures may be required under general anaesthesia.

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Osteomyelitis in a Hermann’s tortoise

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