CASE NOTES

FIELD INVESTIGATION OF KANGAROO DEATHS IN STURT NATIONAL PARK AND AREAS NEAR TIBOOBURRA IN EARLY 2010

Greg Curran, Technical Specialist, Western Division, NSW Wildlife Health Coordinator, Industry and Investment NSW, Broken Hill

Posted Flock & Herd March 2011

SUMMARY

Kangaroo deaths were reported within about 100km of Tibooburra NSW, including within Sturt National Park (NP) in early march 2010. On investigation, the animals affected were red kangaroos, mainly larger adult males and females. Examination of a limited number of affected animals found degrees of blindness without external eye lesions; severe changes around and in most limb joints examined; subcutaneous haemorrhages, congestion and some oedema about these joints, along long bones, and across the rib cage. From reports of the numbers of dead or affected animals seen, the mortality event might have affected 200 to 600 animals. It appeared to last from mid-February to March, 2010. The event occurred after a series of heavy summer rains, from November 2009 to February 2010. Pasture available was excellent, with good diversity of herbage and grasses. Kangaroo populations were much lower than seen in a major die-off of kangaroos in 1998. Water was not a limiting factor, although affected animals tended to be close to the few permanent waters on Sturt NP. Heavy rains had left many smaller ephemeral waters in the area.

Image 1. Looking north to Queensland border and Warri Gate Hut from hilly and stony rise of the Jump Ups. Superb pasture and diversity of species

INDEX CASE

The index case reported was received from a National Park Field Officer, Uli Kloecker. The animal was a large red male about 5 years of age that had been hand-reared as a joey at Mt Wood, about 25km to the east of Tibooburra. This animal had been returned to the wild when young, and only occasionally returned to the homestead. It was seen ill in mid-February 2010. It was reported as unwilling to stand but could, and would move about. It was not eating but did drink milk. It was aware of its surroundings. This animal died about 5 days after first signs of illness. It was not necropsied. No other animals were seen affected in this area at this time. The reluctance to rise is similar to animals affected later. The animal may have been blind but appeared to have some awareness of its surroundings as it may have moved its ears as people moved. It may have been partially blind and perhaps could locate and follow movement with limited vision.

OTHER REPORTS

An experienced Tibooburra kangaroo trapper, Michael Summerfield, noted dead and affected kangaroos in ones or twos from about 18 February 2010. These animals were observed in passing through Sturt NP on his way to leasehold land where he had licenses to harvest kangaroos; on Onepah Station adjacent to and to the northeast of Sturt NP; and on leasehold land immediately about Tibooburra. Michael had been harvesting kangaroos in the 1998 epidemic, and saw some similarities between deaths in 1998 and in 2010. He continued observations until he was reasonably sure that the matter was of concern and contacted LHPA Ranger, John Hiscox, who passed Michael?s reports on to Department of Environment staff.

Image 2. Very large male red kangaroo, dead under a bush. Not scavenged. 17 March 2010

Another Department of Environment field officer, John Illies, reported having seen about six dead red kangaroos near Millers Tank close to the Queensland border and about 30km northwest of Tibooburra on about 9 March 2010. The heavy rains had badly damaged roads and tracks in the area, and had prevented movement and inspection. Coincidentally, shortly before receiving this report from Michael Summerfield, Department of Environment staff had raised concerns that conditions in the northeast might be conducive to a kangaroo die-off. This had led to veterinarians in Industry and Investment NSW to prepare a kangaroo die-off response plan. This plan was rolled out a few days after it was prepared.

There were large numbers of biting insects following the heavy rains. Most were mosquitoes but there were some reports of sandflies.

FIELD OBSERVATIONS

Michael Summerfield reported seeing kangaroos that were ?stiff and sore? and sometimes bent over as though they were perishing, as well as some dead kangaroos. Seeing numbers of dead animals was unexpected, as pastoral conditions were exceptionally good.

Two affected animals in Sturt NP on 11 March 2010 were examined. They were found recumbent under bushes, and reluctant to rise. As we moved closer, both found it difficult to locate where we were, as judged by their ear movements. When the animals knew we were close, both rose and moved away slowly and steadily. The older red male found it more difficult to move but had no incoordination and no obvious lameness. He moved towards a vehicle and people, which was consistent with being blind. He had an aged cataract on one eye. The other eye appeared normal. There was no response to rapid movement towards the eye but he did respond when the eyelid was touched. The red doe moved more freely than the male but was easily caught. She did not appear totally blind, as judged by her response to movement towards her eyes. The male was in poor condition; the female was fat.

Image 3. Red male recumbent as Greg Curran approaches. Sturt National Park 11 March 2010.

Image of recumbent kangaroo and veterinarian

Neither had rapid respiratory rates despite rising and moving, and the stress of capture. Neither had jaundice nor were their skins hot to touch. No body temperatures were taken.

Several dead kangaroos were observed. These were generally larger red adults and were close to or under bushes. Relatively few animals were affected.

Necropsy

The male and female kangaroos examined above where euthanased and necropsied. Key features observed were:

Polyarthritis in both animals.
Severe inflammation (haemorrhage and exudate) surrounding the joints of limbs of both animals.
In the male but not the female, some small linear structures that may have been round worms (possibly Breinlia spp) were seen in the inflamed areas around the joints.
Widespread subcutaneous haemorrhages along long bones and over the rib cage of both animals. There were no haemorrhages in internal organs.
Congestion of the bone marrow of the hindlimbs of both animals..
Congestion of body fat in the female. The male had no observable fat.
Eyes - normal appearance but clinically blind.
Splenomegaly in the male.
Pericardial effusion which was non-clotting in both. No other changes. The male had exhausted all fat around the heart.
All kidneys had a lighter than expected cortex. The urine was clear and the bladder normal.
The livers were normal but with minor fatty change.
The intestinal tract and stomachs were normal. Very few internal parasites seen. There was good quality but reduced volume of ingesta in the stomachs. There was a good quantity of dung in both.
The lungs appeared normal.
Oral cavities appeared normal.
The dead animals had similar external damage around the joints as live animals.

Image 4. Haemorrhage, inflammation and arthritis of the hock (male kangaroo)

Image 5. Subcutaneous and adventitial haemorrhage, inflammation and oedema in the tissues along the long bones (including tendons and ligaments)

Image 6. Spleen showing rounded edges, thickening, and an abnormal texture of the surface (male kangaroo)

Image 7. Pericardial effusion

Image 8. Haemorrhages of subcutis and adventitia over thorax (female kangaroo)

COMPARISON OF THE 2010 EVENT WITH PREVIOUS EPIDEMICS

A. 1994 Wallal-Warrego blindness

This disease affected a much larger area of NSW, Victoria and SA. Animals affected were blind or partially blind, and died from misadventure, usually over weeks and months. Where feed and water were sparse, they died from starvation and malnutrition but most areas had reasonable to good pastures.

Animals necropsied showed no gross pathology, and no haemorrhages or damage to joints.

The disease incidence commenced and increased in cooler months after insect activity had subsided. The disease developed over several months, which appeared to allow them to adapt to developing blindness in a variety of ways, including following other kangaroos to water or away from disturbance.

Morbidity and mortality rates were relatively low in any area, compared with the 1998 die-off where morbidity and mortality rates were moderate to extreme. The epidemic lasted for months in any given area and three years across Australia.

Laboratory investigations (Hooper, 1999; Reddacliff, 1999) showed:

Wallal virus antigen in affected retinas.
Orbivirus was seen on electron microscopy.
Wallal virus was present in 3 species of Culicoides midges.
Wallal virus DNA was found in a preserved affected retina from 1975.
Chorioretinitis lesions were found in 3 of 8 kangaroos inoculated with Wallal virus.
Wallal virus and antigen was found in affected retinas of inoculated viraemic animals.
Animals inoculated with Warrego virus alone did not develop chorioretinitis.

B. 1998 Epidemic die-off

In 1998, a much larger number of animals died (possibly 50,000 or more) in the Tibooburra area over several days. Reds, greys and wallaroos were affected. Many were found dead under bushes, and were in family groups. All ages were affected.

Blindness was not observed but the deaths happened so rapidly that no reports of clinical signs of affected animals prior to death were recorded. Later animals were reported to have lost condition, and were lame or had difficulty moving.

No animals were examined during the 1998 epidemic. The few animals examined at the end of the epidemic had marked lameness, illthrift and evidence of parasitic larval tracts through the muscles of the hindlimb. There were no marked lesions around joints.

C. Comparison of the 2010 event with the 1994 Wallal blindness and 1998 die-off.

The 2010 event was characterised by:

blindness, arthritis, haemorrhages, death, splenomegaly.
much lower morbidity and mortality rates than the 1998 die-off.
a similar short time course to the 1998 die-off and a much shorter time course than the 1994 Wallal blindness.
a shorter disease course than Wallal blindness; and a similar or slightly longer disease timeline than 1998 die-off.
a similar high insect activity to the 1998 die-off. The Wallal blindness occurred at times of low or nil insect activity.
during the Wallal blindness incident; evidence of arthritis, subcutaneous haemorrhages, splenomegaly, pericardial effusion and ill thrift was not recorded.

RAINFALL EVENTS

Rainfall in November, December and February 2010 was much higher than usual.

Rainfall for Tibooburra for late 2009 and 2010 (mm rain)

	Oct 2009	Nov 2009	Dec 2009	Jan 2009	Feb 2009
2009-2010	1.4	41.6	44.2	8.6	155.0
Median*	9.1	8.4	11.1	8.9	10.9
Mean*	18.1	16.4	21.8	27.4	29.6

*Tibooburra Post Office has continuing rainfall records from 1899 to date

Rainfall for Tibooburra for 1998 (mm rain)

	May	Jun	Jul	Aug	Sep	Oct*	Nov	Dec
1998	5	13	87	3	140	12	50	7
Median	8.6	7.6	9.0	5.4	5.9	9.1	8.4	11.1
Mean	18.3	16.7	16.4	11.7	12.2	18.1	16.4	21.8

* Month with kangaroo die-off

Rainfall in 1998 is given for comparison. The 1998 kangaroo die-off occurred in October over several weeks. Rainfall in July and September was much higher than usual. Rainfall in September 1998 amounted to 63% of mean annual rain, and was the highest September rain on record. The total rainfall for July and September 1998 (227mm) was slightly greater than the mean annual rainfall.

If the 1998 die-off was related to biting flying insect activity, it is likely that the September rainfall event was more important than the July event, as the colder conditions of July usually prevent insect build-up.

If the 2010 mortality event was related to biting flying insects, the deaths could be related to rainfall during November/December 2009 or February 2010. If the relationship between timing of rain in 1998 and timing of deaths held for deaths in 2010, the rainfall in February would be related.

BIOSECURITY AND SURVEILLANCE ASPECTS

Western NSW is a major producer of kangaroo meat for overseas and local markets. Kangaroo meat processors are acutely aware of any threat to the market?s perception of the quality and safety of kangaroo meat. On hearing of reports of kangaroo deaths, meat processors immediately closed chillers in the affected area. There was pressure to investigate the deaths to determine cause and to formulate the best management of kangaroo harvest and meat processing.

Meat processors sought assurance that it was possible to prevent any affected animals to be excluded from harvest and the meat supply chain.

The investigation found that normal field inspection by harvesters would be able to detect clinical signs of animals being affected before being shot (behavioural changes due to partial or complete blindness; gait changes with arthritis) and to detect gross pathology changes in any affected animals that were shot. Surveillance of the area and its margins by National Parks and Wildlife Service staff, local stockowners, harvesters, with support from a team controlling locusts in the area, provided a picture of the incidence of this problem, and when cases were no longer being seen.

With this information, meat processors resumed intake of harvested kangaroos from the affected area.

COMMUNICATIONS

A national coordinating team met regularly by teleconference. This group discussed and agreed on investigation, surveillance, biosecurity and communications required.

ConclusionS

Similarities to the 1998 die-off include:

Polyarthritis.
Short disease course and timelines.
Animals dying under bushes.

Far fewer animals were affected in 2010 compared with 1998, however this might be related to the much lower kangaroo densities of 2010.

When compared with the Wallal blindness epidemic:

The epidemiology and gross pathology of the 2010 event was distinctly different.
The blindness in 2010 might have been caused by Wallal virus if kangaroos were infected with insect activity after November or December rains.
Joint and subcutaneous lesions were far more recent than the more chronic Wallal chorio-retinitis.
Joint and subcutaneous lesions were not seen in the Wallal epidemic.

That joint and subcutaneous lesions were not seen in the Wallal epidemic might be explained by proposing:

Animals were affected by the Wallal virus as well as a later second virus (possibly an orbivirus capable of causing vasculitis).
A virus capable of causing both a more acute chorio-retinitis and the other lesions observed (possibly an orbivirus) was involved.
A Wallal virus capable of more acute chorio-retinitis and the other lesions observed, including haemorrhage and arthritis.
The haemorrhages and other inflammatory changes may be an indication of viral damage or secondary bacterial infection, or both.

The observation of worm parasites (possibly Breinlia spp) does not explain the haemorrhage, congestion and oedema observed, nor the damage to tendons, ligaments and joints.

The subcutaneous lesions around the joints and elsewhere were not consistent with primary insect bite damage. The furred side of the skin had no swelling or other signs of marked insect damage. Insect activity had declined with cooler conditions for some days before our examination.

The lesions were not consistent with any trauma during capture.

It is possible that developing blindness in certain kangaroos predisposed them to subsequent insect attack, and any pathogenic agents they carried.

FURTHER REPORTS

Cases of similar deaths have been reported by harvesters in a flooded area of south west Queensland. Queensland Biosecurity staff investigated. Samples collected from affected animals were sent to NSW EMAI veterinary laboratory for viral studies. Surveillance and response work in NSW and Queensland was coordinated by Dr Tiggy Grillo of the Australian Wildlife Health Network.

National Geographic Channel commissioned a segment on the investigation, which is being aired in 2011, with filming in Broken Hill and at AAHL.

References/READING LIST

T. Grillo, G. Curran, I. Roth, A. Gordon, P. Kirkland, D. Ryan, M. Wingett, B. Lake, B.Norman, M. Summerfield, B. Capellini. (2010) Investigation of kangaroo deaths in north-western NSW and south-western QLD in early 2010. Australian Wildlife Health Network
Curran, Greg (2010). Case report: earliest kangaroo mortality in Tibooburra area February 2010. Industry and Investment NSW, Broken Hill.
Wildlife Health in Australia: (March 2010). Investigation of kangaroo deaths in north-western NSW and south-western QLD in early 2010
Mulga Line. (July 2010). Investigation of kangaroo deaths in north-western
NSW and south-western QLD in early 2010
AN Gordon, M Gabor, T Grillo, G. Curran, M Wingett, B Lake, P Kirkland, K Condon, J Bingham. (2010). Macropod mortality associated with heavy rains and flooding in NSW and Queensland during March 2010: laboratory investigations
Clancy TF, McRae PD, Southwell C, Weaver K and McDonnell JM (1990). Post-flood die-off of kangaroos in south-western Queensland. Unpublished internal report to Queensland National Parks and Wildlife Service
Curran G, Gay E and Gilroy J (1999). Investigations of a major epidemic mortality of macropods in the northern part of far western NSW in October 1998. Unpublished internal report to the NSW Kangaroo Management Committee, 1999
Hooper PT, Lunt RA, Gould AR, Hyatt AD, Russell GM et al.. (1999). Epidemic of blindness in kangaroos – evidence of a viral aetiology. Australian Veterinary Journal77: 529-536
Reddacliff L, Kirkland P, Philbey A, Davis R, Vogelnest L et al.. (1999). Experimental reproduction of viral chorioretinitis in kangaroos. Australian Veterinary Journal 77: 522-528
Speare R, Johnson PM and Pullsford T (1991). Epidemic mortality in large macropods of central western Queensland during May 1990. Unpublished internal report to Queensland National Parks and Wildlife Service