Exploratory coeliotomy and removal of an enterolith

from a Sand Tiger shark (Carcharias taurus)

Paul Hale1 Sue Thornton 2 Tania Monreal Pawlowsky2 Mark F. Stidworthy 2

1 SeaLife London Aquarium, County Hall, Westminster Bridge Rd, London, SE1 7PB, UK

2 International Zoo Veterinary Group, Station House, Parkwood St, Keighley, West Yorkshire, BD21 4NQ, UK

Introduction

Discussion

Anaesthesia

Operation

Changes to shark husbandry

Enterolith

Acknowledgements

Post Mortem examination

References

Contact Information

A reduced appetite and subsequent weight loss was observed in

a 2.7m female Sand Tiger shark (Carcharias taurus) at the

SeaLife London Aquarium. The shark had been a resident in the

aquarium for 12 years, having arrived as a juvenile.

There were no obvious signs that would account for the refusal

of food and the other sharks in the exhibit continued to feed

normally. A variety of fresh and frozen food items were tried with

inconsistent results. Over a period of 18 months separate

treatments with antibiotics, non steroidal anti-inflammatory drugs

and anabolic steroids did not return the feeding rate to normal.

Following the weight loss a large bulge was observed in the

abdomen. The mass was palpated by a diver swimming along

side the shark and was found to be firm and mobile. Due to the

failure of the previous treatments and the condition of the shark,

an exploratory coeliotomy was considered the best option.

Capture

MS222 at 100mg/L was used

for induction. This was

increased over the following

hour to 325mg/L and was

reduced at the end of surgery

to reduce the recovery time.

Oxygen levels were kept

between 120-140% saturation

for the duration of the

operation.

The anaesthesia tank was

converted to an operating

table with the addition of a

curved perforated plate once

the induction of anaesthesia

was complete.

The shark was ventilated and

kept under sedation by

pumping water from the

anaesthesia tank over the

gills. The eyes and nostrils

were also kept moist during

the operation by periodically

flooding with water.

1 2

3 4

A midline incision at the approximate position of the stomach was

made. At this time, the liver was noted to be abnormally reduced

in size (atrophied), enabling easier access to the stomach and

intestines.

Some of the gas

contained within the

stomach was aspirated

to reduce its size before

lifting it out of the body

cavity.

A solid mass was found at the entry to the spiral valve and

removed.

Any undigested

remains were

removed from the

intestines, the

incision cleaned,

closed and the

intestines returned

to the body cavity.

The shark was returned to the exhibit immediately after the

incision had been sealed and was forced ventilated to aid

recovery. Respirations increased and it appeared to recover but

unfortunately deteriorated and died 7 hours later.

The authors are grateful to Professor Keith Rogers, Cranfield

University, for the X-ray diffraction analysis and the team at

SeaLife London for their assistance with the operation.

1) Hassel DM, Snyder JR, Langer DM, Drake CM, Yarbrough TB.

Equine enterolithiasis: A review and retrospective analysis of 900

cases (1973–1996). Soft Tissue Surgery (1997) 43: 246–247.

2) Burdett LG, Osborne CA. Enterolith with a stingray spine nidus

in an Atlantic bottlenose dolphin (Tursiops truncatus). J Wildl Dis.

(2010) 46:311-315

When an octopus is fed to the sharks the beak is now removed

and to reduce the amount of calcium in the diet the heads from

large fish are also removed.

Post mortem examination and histopathology did not reveal the

cause of death. The appearance of the liver was consistent with

the history of weight loss, implying significant loss of reserves of

body fat, probably affecting the shark’s ability to cope with

capture, anaesthesia and surgery. Sections of spiral valve/large

intestine showed no major histological changes to correspond

with the impacted enterolith.

Enteroliths are generally rare, but have been described in a

range of vertebrates, particularly horses (1). To the authors’

knowledge this is the first record of an enterolith from an

elasmobranch. An enterolith around a stingray spine nidus has

been described in a bottlenose dolphin (2).

The exact reason the enterolith formed is unclear but changes in

the pH of the intestine and a diet high in minerals can contribute

to their formation following the ingestion and intestinal impaction

of any indigestible object capable of acting as a nidus.

The female Sand Tiger shark shared the exhibit with two males

and several other species of large shark and none have shown

any signs of being affected with the same disorder.

The nidus is usually an indigestible item around which the

enterolith is formed.

Analysis using X-ray

diffraction showed

that it consisted of

calcium

hydroxyapatite

(calcium phosphate

carbonate), the main

component of fish

scales and skeletons.

The mass was identified as an enterolith. Enteroliths are formed

by mineral deposition in concentric layers around a central nidus

of ingested material. The composition of the mineral is

determined by the chemistry of the intestinal content. It is

suspected that this enterolith formed over a period of many

months to years, but the exact duration cannot be determined.

p.hale@londonaquarium.co.uk

S.Thornton@izvg.co.uk

In this instance a beak from

an octopus was found at the

centre of the enterolith.

Octopus are used as food for

several species in this exhibit,

though it is possible that the

beak was consumed in the

wild.

A clear flexible PVC sock was used by the dive team to capture

the shark and pass it to the surface team who transferred it to the

anaesthesia tank.

The technique used to close the abdominal wall involved the use

of 19 gauge hypodermic needles to provide a channel for the

suture material as the suture needles were unable to repeatedly

penetrate the shark’s skin.

Surgical

glue was

used to seal

the incision.