CASE NOTES


WINTER 2011 STATE REPORT NSW

This report is a compilation of reports of sheep disease events provided primarily by LHPA district veterinarians across NSW. An edited version appears in the Sheep Vets Newsletter, Skirting the Issues.

Bruce Watt, Tablelands LHPA, Bathurst

Unfortunately, after exceptionally wet conditions over the summer much of NSW is now dry. Kath Marsh from Condobolin reports that sheep feeding is widespread in her area. Consequently, she is seeing feed-related issues including grain poisoning, PEM and urea poisoning. Kath comments that worms (mainly scour worms) are also starting to be an issue with nutritional stress compounding the problem. Greg McCann based in Dubbo, also reports grain poisoning in ewes on feed. As he observed, more sheep die from overfeeding in a drought than underfeeding.

Steve Eastwood based at Armidale reports that the New England has experienced a relatively mild winter and stock are in good condition. However, pregnancy toxaemia has been seen especially in early lambing, twin bearing ewes. In the centre of the state Jillian Kelly (Dubbo), reports that she has also seen sheep affected by pregnancy toxaemia, in those flocks that aren't supplemented or are supplemented incorrectly. One example of this is ewes were supplemented with cottonseed - 60 ewes had died and the owners were finding 10 ewes down each day with signs consistent with pregnancy toxaemia. The deaths stopped when additional barley was fed out each day. 

In the southwest, Dan Salmon, based at Deniliquin reports that the dry winter with a good body of dry feed from the wet summer has meant that sheep have remained pretty healthy. There have been rare cases of pregnancy toxaemia and even rarer cases of metabolic disorders on grazing crops. Dan comments that even the lice seem to be settling down as producers start to use treatments that will kill lice.

Pregnancy toxaemia has also been reported as a significant problem in the dry northwest according to Libby Read based at Narrabri and in the central west according to Belinda Edmonstone based at Forbes. Belinda commented that the favourable summer and early autumn might have contributed with high twinning rates. Colin Peake from Hay reports a few cases of pregnancy toxaemia (but plenty of lice). In the far southeast, Chris Haylock reports that wet conditions there have also led to foot abscess followed by pregnancy toxaemia. Seems that we cannot escape pregnancy toxaemia this season.

Internal parasites have been and continue to be a major problem on the southern tablelands. Bill Johnson based at Goulburn reports that seasonal conditions have been conducive to survival of worm eggs and larvae for eighteen months. This along with declining feed availability (quality and/or quantity) for lambing ewes has seen some explosive worm outbreaks. Despite pre-lambing drenching with an effective drench, several flock owners have been forced to drench again before lamb marking, to stop the ewe deaths, especially in ewes rearing twins. There are often marked paddock effects, with those, which have been used in the previous few months by last year's lambs being the most dangerous. Both Teladorsagia and Trichostrongylus predominate. Merino weaners have also been affected, one typical owner picking up 40 dead ('and a lot more looking pretty weak') five weeks out from an effective drench.

Vaginal prolapse in ewes is an intriguing problem. New Zealand studies indicate that multiparous crossbred ewes grazing hilly country pre-lambing are most at risk. Oestrogenic pastures predispose to the problem (West et al 2009). However, a Bathurst merino breeder recently who lost 34 of 800 mixed age merino ewes to vaginal prolapse. The ewes were only in fat score 2-3 and were grazing on native pastures with limited clover. Another producer recently lost eight of 800 maiden merino ewes to vaginal prolapse. One of the respondent to a Tablelands LHPA ewe mortality survey lost 10% of his ewes to vaginal prolapse last year. Losses seem to be variable, unpredictable and do not always follow accepted risk factors.

The Wagga office has also received a number of reports of vaginal prolapse in ewes. These seem to be associated with multiple risk factors including; high BCS ewes, retention of older ewes in lambing mobs (>5years old), grazing on winter cereal crops (possible link with low calcium intake in older ewes affecting capacity of musculature to retain prolapse). Eliz Braddon based at Young has also had quite a few producers reporting vaginal prolapse in ewes.

Eliz Braddon, Ian Masters based at Gundagai and the Wagga office also reported listerial abortions in ewes. Eliz commented, 'we have had a few notifications of increased abortions in ewes (late term usually) one investigation was unrewarding but the second yielded a pure culture of Listeria ivanovii in two foetuses submitted.' The Wagga office reported that a second Listeria ivanovii abortion outbreak was investigated in crossbred ewes. Estimated losses are 20-30 still born/aborted foetuses in a mob of 800 3-6 yo ewes. The suspected source of contamination is access to spoiled canola meal post disposal.

In the case Ian Masters reported, Listerial abortion occurred in a mob of maiden merino ewes from the Cootamundra area. The ewes were running on a rank phalaris dominant pasture that had been slashed earlier in the year to knock down summer growth. Ian suspected a build up of trash and wet, cloudy weather may have provided the right conditions for this bacterium. The small liver lesions (pinhead sized, white spots on a swollen liver) were difficult to see when autolysis set in so easily missed. In this case, 10-15 late term abortions ex 260 ewes over 3-4 days then seems to have stopped. No neurological cases in this mob and no problems in older ewes on similar feed.

Phalaris staggers affected 13 of 160 8-month-old second cross lambs between Bathurst and Orange. The lambs have grazed phalaris for most of their lives. The diagnosis was confirmed by histopathology. Greg McCann, saw the disease south of Dubbo. On one property, new cases occurred 3 months after the sheep were removed from the pasture, with symptoms brought on by yarding. Tony Morton, district veterinarian based at Wagga reported big losses in purchased merino weaners. Those from the southern tablelands were less affected than those from northwest NSW. Eliz Braddon based at Young has reports of at least ten cases in the past six weeks while Chris Haylock has also seen phalaris staggers near Bombala.

The Wagga office also reports salmonellosis causing diarrhoea and deaths young SAMM rams subsequent to handling and trucking and a case of Mycoplasma ovis causing light losses in merino weaners. They also reported a large outbreak of post mulesing infection in one of three mobs. The affected mob was mulesed under wet conditions. Fortunately, mass medication of the whole mob with long acting tetracycline was very effective. M. ovis has also caused post mulesing losses in the Dubbo region. Lambs on grazing cereals have also developed bone problems in the Dubbo and Forbes regions.

REFERENCE

West DM, Bruere AN and Ridler AL. The Sheep. Health, Disease and Production. 3rd edition. 2009, pp 397-399

 


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