Short-beaked Echidna (Tachyglossus aculeatus aculeatus) with severe sparganosis and mycobacteriosis

Submitted by mkemp on Mon, 11/21/2016 - 11:31

HISTORY

Short-beaked echidna

An adult female echidna was found on a road in Cromer, NSW and taken to a local veterinary hospital.  The echidna was not moving well and was sent to Taronga Wildlife Hospital for assessment.  The echidna presented with a large lump on its back (Image) and was subject to x-ray under anaesthesia where it was found to have a fracture of the left zygomatic arch and an old maxillary fracture.  The pelvic structure appeared abnormal, possibly due to old, healed fractures.  There was a large, firm, soft tissue mass visible on the right dorsum over the shoulder joint and several smaller associated masses.  A fine-needle aspirate showed the mass to contain clear fluid with white deposits.  The echidna was emaciated with a body condition score of 1/5. Euthanasia was elected.

GROSS FINDINGS

The animal was in poor body condition and moderate to good hydration.  Externally large, firm masses were palpable under the skin on the right side, extending from the axilla to the inguinal area.  On reflection of the skin, 4 masses were shelled out from the subcutis, the largest measuring 12 x 15 cm and weighing 984 grams.  

Image: Short-beaked echidna with multiple large, firm, subcutaneous masses over right dorsum (Australian Registry of Wildlife Health)

Image: Short-beaked echidna after multiple large, firm, subcutaneous masses were removed from over the right dorsum (Australian Registry of Wildlife Health)

On cut surface the mass was pale cream and tan, solid and granular.  Smaller masses (5x8 cm) contained 2-3 mm diameter cysts from which translucent oblong structures could be extruded.

Image: Cut surface of large subcutaneous mass (left), and smaller mass (right) removed from a Short-beaked echidna (Australian Registry of Wildlife Health)

Multiple 1-2 cm diameter cream/tan firm masses were present in the lungs.  A wet preparation shows foamy macrophages and neutrophils.  The pelvis was fractured in three places.

Image: Multiple pulmonary masses in a Short-beaked echidna (Australian Registry of Wildlife Health)

BIOCHEMISTRY

Total Protein (refractometer) 66 g/L 

Total Protein (colorimetry) 71 g/L 

Glucose 4.8 mmol/L 

Urea Nitrogen (BUN) 11.4 mmol/L 

Creatinine 53 umol/L 

Calcium 2.47 mmol/L 

Phosphate 1.38 mmol/L 

Sodium 131 mmol/L 

Potassium 5.4 mmol/L 

Albumin 28 g/L 

Globulin 43 g/L 

ALT(SGPT) 109 U/L 

Total Bilirubin 15 umol/L 

Amylase 225 U/L 

Alkaline Phosphatase 165 U/L 

HAEMATOLOGY

White Blood Cells 13.75 x 10 E+9/l 

Haemoglobin 103 g/l 

Packed Cell Volume 28 % 

Heterophils/Neutrophils (%) 33 % 

Heterophils/Neutrophils (x10^9/L) 4.54 x 10 E+9/l 

Lymphocytes (%) 57 % 

Lymphocytes (x10^9/L) 7.84 x 10 E+9/l 

Monocytes (%) 3 % 

Monocytes (x10^9/L) 0.41 x 10 E+9/l 

Eosinophils (x10^9/L) 0.14 x 10 E+9/l

Eosinophils (%) 1 % 

Atypical mononuclear 6%

Atypical mononuclear 0.83 x 10 E+9/l

HISTOLOGY

Tissues are in good condition. The following tissues exhibit no significant histopathological changes: Bladder (D), stomach (D), kidney (D), ovary (E), heart (E), pancreas (E), colon (F), ileocaecal junction (F), brain (G, H)

Masses (A): The masses consist of dense connective tissue (fibrosis) surrounding multiple large clear spaces. These spaces contain multicellular organisms in various stages of degeneration. The organisms lack a pseudocoelom, contain calcareous corpuscles and are surrounded by a tegument (larval pleurocercoids). In some cases, large numbers of neutrophils are filling the spaces and into the degenerating worms.

(Image: Subcutaneous masses containing plerocercoids, believed to be Spirometra erinacei, surrounded by an inflammatory infiltrate.)

Lung (B, C): Corresponding to firm white lesions noted grossly, the pulmonary parenchyma is demonstrating coagulative and some liquefactive necrosis. Within this necrosis, there are numerous pleurocercoids, as described above, in various stages of degeneration. Alveoli adjacent to affected areas are lined by hyperplastic pneumocytes and contain foamy macrophages. Viable worms are often found in these areas. No acid fast organisms are detectable on a Ziehl Neelsen stain.

(Image: Pulmonary parenchyma with coagulative and liquefactive necrosis, with degenerating pleurocercoids, and alveoli lined by hyperplastic pneumocytes) 

Spleen (A): Moderate extramedullary haematopoiesis. 

Liver (C): Minimal extramedullary haematopoiesis. Hepatocytes are reduced in size with an increased nuclear to cytoplasmic ratio.

Duodenum (E): Rare coccidial organisms are found in the enterocytes.

OTHER

Taronga Wildlife Hospital:  Acid Fast Bacilli observed on direct lung smear 

Victorian Infectious Diseases Reference Laboratory (VIDRL):  Lung tissue and aspirate on slide - Mycobacterial DNA DETECTED by PCR. This test does not necessarily indicate presence of viable organisms.

MICROBIOLOGY

ZN Stain:  Lung - Negative

Aerobic Culture:  Lung - No Growth / No Significant Growth

Anaerobic Culture:  Lung - No Growth / No Significant Growth

Fungal Culture:  Lung - No Growth / No Significant Growth

DIAGNOSIS

Euthanasia

Pelvic fracture, probable vehicular trauma

Subcutaneous sparganosis, likely Spirometra erinacei

Pulmonary sparganosis, likely Spirometra erinacei

Mycobacteriosis - Mycobacterium chelonae

COMMENT

Based on gross and histopathological findings, the large masses in the subcutis of this echidna were associated with spargana (larval cestodes). There was immense fibrosing reaction to the organisms, many of which were not viable. In addition to the subcutis, the same organisms were found in the lung where they had also incited immense reaction. 

Additionally, acid fast bacteria were detected on a direct post-mortem smear from lung. The acid fast bacteria could not subsequently be detected with ZN stained histological sections. Despite this, PCR at VIDRL detected DNA from Mycobacterium chelonae. This is a very unusual finding. Echidnas are not reportedly susceptible to mycobacteriosis. Additionally, M. chelonae is most commonly associated with fish and reptiles, although it is considered a rare but ubiquitous environmental species, and can cause disease in humans (generally immunocomprimised).

Finally, the animal had an acute pelvic fracture which was likely the result of being hit by a car.

An adult female echidna was found on a road in Cromer, NSW and taken to a local veterinary hospital.  The echidna was not moving well and was sent to Taronga Wildlife Hospital for assessment.  The echidna presented with a large lump on its back (Image) and was subject to x-ray under anaesthesia where it was found to have a fracture of the left zygomatic arch and an old maxillary fracture.  The pelvic structure appeared abnormal, possibly due to old, healed fractures.