CASE NOTES


TURTLE MORTALITIES ON THE BELLINGER RIVER

Sarah Britton, Animal Biosecurity & Welfare, NSW Department of Primary Industries (DPI)

Posted Flock & Herd May 2015

INTRODUCTION

In mid-February 2015, an increasing number of sick and dead turtles were reported from a section of the Bellinger River on the north coast of NSW. The Bellinger River Snapping Turtle (BRST) appeared to be the only species affected. They presented emaciated and with severe eye lesions causing blindness. Multiple agencies have been involved in the investigation and management of the event.

BELLINGER RIVER SNAPPING TURTLE

The Bellinger River Snapping Turtle (Myuchlys georgesi) is only found in a 70 kilometre section of the Bellinger River (and Kalang River) in Northern NSW. A 2007 survey estimated the total population of this species at 1500- 4500. The species is at risk of being endangered, due to the high fatality and high morbidity rate. Smaller numbers of other species including the Murray River Turtle (Emydura macquarii) are also present in the rivers but appear to be unaffected. Only 5 Emydura sp. have been seen but were all normal and no reports of sick or dead Emydura sp. have been received.

M. georgesi is omnivorous, predominantly carnivorous and reliant on sight for feeding. They often feed on macro invertebrates, terrestrial fruit and aquatic vegetation and prey such as caddis-fly larvae (Cann et al).

They live in deeper pools of clear running water and prefer the upper waters of the Bellinger River. They tend not to live in the brackish water in the lower Bellinger River.

EPIDEMIOLOGY

Over 330 BRST have been collected from a 20 km stretch of the Bellinger River since 17 February 2015. The affected area has been divided into cold, equating to no sick or dead turtles, and hot, indicating a high number of sick or dead turtles found. 66% of the available habitat of M. georgesi is within the hot (red) zone (see map below). The case fatality rate ranges between 95-100% and very few healthy turtles have been seen on surveys of the affected area.

Epidemiological studies have shown that in recent years there have been higher water and air temperatures. There has also been a drop in the water level.

Figure 1: Map of affected area (courtesy of OEH)

PRESENTING SIGNS

Initial presenting signs were swollen eyes and emaciation. Many had slight clear nasal discharge, and some animals had hind limb paresis. At necropsy, animals were thin, had bilateral swollen eyelids and anterior uveitis, with tan foci on skin and ventral thighs.

HISTOPATHOLOGY

Histopathology findings included

There was evidence of fibronecrotising splenitis and nephritis with inflammation and embolic spread showering into multiple organs. All turtles had acute lesions but the severe emaciation suggests an undetermined event preceded and possibly predisposed to the development of the acute inflammatory changes.

Fig 2: Renal pallor with tan foci (courtesy K.Rose)

OTHER LABORATORY TESTS

On haematology, animals had low white cell counts and low total protein. Several animals had elevated uric acid and creatinine kinase.

A chlamydia like organism was found in the eyelids of affected animals, but not elsewhere in the body. Aeromonas hydrophilia was also cultured from the eyelids. Trichomonas PCR, protozoal PCR and Mycoplasma PCR were all negative. Viral studies including Ranavirus, Adenovirus, Ferlavirus, Herpesvirus, Picornavirus PCR were all negative and no growth on viral culture (Chinook salmon embryo cells, Rainbow trout gonad cells and Bluegill fry caudal peduncle cells). Electron microscopy did not detect any infectious agents.

The NSW Environment Protection Authority (EPA) collected water samples at four separate sites on the 18/2/15 and did not identify any pesticides (including organochlorines, organosphosphorus and pyrethroids) or hydrocarbons. The EPA also inspected the road works being conducted by Road Maritime Service (RMS) at Myers Bluff on Waterfall Way and no significant environmental issues were identified at this site.

Turtle tissue heavy metal and pesticide testing is being conducted by the EPA to determine if it could be a possible cause for the poor body condition. Algal counts and identification are also being conducted and other tests still being performed include deep sequencing. At this stage the cause of deaths has not been determined. Investigation of the disease has involved sharing and discussion of results with the Australian Registry of Wildlife, Elizabeth Macarthur Agricultural Institute (EMAI) laboratory staff, Australian Animal Health Laboratory (AAHL), experts from University of Sydney, Murdoch University, University of Queensland, University of Tasmania, specialists from overseas and many other experts in herpetology.

DISCUSSION

So far, it has not been possible to rule out an infectious cause. However, it appears there are most likely multiple causal factors. Affected animals were observed to not recover from their illness. Therefore, as a biosecurity precaution, dead and sick turtles have been removed from the river to reduce the risk of possible transmission to other turtles. It also reduces the risk of other animals moving carcasses to other catchment areas. The area upstream of the affected zone has been closed to the public temporarily.

NSW DPI have released a fact sheet Keep a clean routine which gives hygiene advice to people using the river for recreational purposes.

The Bellinger River Turtle mortalities have highlighted a number of biosecurity challenges.

A multi-agency Incident Management Team (IMT) was established in the township of Bellingen on the 9/03/2015. The purpose of the IMT was emergency management, built around objectives of ensuring public health and safety, understanding the extent of mortality, maximising animal welfare, minimising the spread of any potential pathogens and maintaining accurate information flows to the local community. The IMT was supported in its work by a large team of specialists from the Office of Environment and Heritage (OEH, including NSW National Parks & Wildlife Service (NPWS) and Regional Operations Group and Heritage Division (ROGHD)), the EPA, Department of Primary Industries (DPI), Local Land Services (LLS), NSW Health and Bellingen Shire Council.

The combined influence of a small and restricted natural population, the high mortality rate and the possibility that that very few healthy animals remain in the population created an urgent need to initiate species recovery measures. The IMT, whose focus was emergency management, stood down and the response has continued under an over-arching BRST Species Management Program.

The over-arching objectives of the BRST Management Program include:

  1. Maximise the chances that Myuchelys georgesi will persist in the wild in the long term.
  2. Minimise risks from the spread of any potential pathogen to other wild and domestic animals, industries, communities and other catchments.
  3. Ensure the Bellingen and wider communities remain informed and updated about the on-going response.

This BRST mortality event highlights that significant disease in the wildlife sector can impact the survival of the species and while diagnostics may be able to identify specific pathogens being involved, the disease event may be symptomatic of environmental changes. Dealing with wildlife emergencies will always be difficult due to the lack of specific response agreements and funding to investigate and manage a response. The diversity of species and possible causes of disease often means a lengthy diagnostic process. Also the uniqueness of the species and its environment brings its own specific biosecurity requirements.

ACKNOWLEDGEMENTS

Office of Environment and Heritage (OEH, including NSW National Parks & Wildlife Service (NPWS) and Regional Operations Group and Heritage Division (ROGHD)), the EPA, Department of Primary Industries (DPI), Local Land Services (LLS), NSW Health and Bellingen Shire Council, Wildlife Health Australia, Karrie Rose and Australian Registry of Wildlife Health, multiple Universities in Australia and overseas, experts in herpetology.

REFERENCES

  1. Allanson M, Georges A. Diet of Elseya purvisi and Elseya georgesi (Testudines: Chelidae), a Sibling Species Pair of Freshwater Turtles from Eastern Australia. Chelonian Conservation and Biology 1999; 3 (3):473-477
  2. Spencer, R-J., Georges, A., and Welsh, M. (2007). The Bellinger Emydura. Ecology, Population Status and Management. Report to NSW National Parks and Wildlife Service, Sydney, by the Institute for Applied Ecology, University of Canberra. July 2007
  3. Cann J, Spencer R-J, Welsh M, Georges A. Myuchelys georgesi (Cann, 1997) Bellinger River Turtle draft paper
  4. Spencer R-J, Georges A, Lim D, Welsh M, Reid AM. The risk of inter-specific competition in Australian short-necked turtles. Ecol Res (2014) 29: 767-777
  5. Curran G. Data for Bellinger River at Thora pers comm
  6. Blamires S, Spencer R-J. Influence of habitat and predation on population dynamics of the freshwater turtle Myuchelys georgesi. Herpetoligica 69 (1), 2013, 46-57

 


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