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CASE NOTES


NSW STATE REPORT AUTUMN 2013

Bob McKinnon, based at Tamworth provided the executive summary for the autumn 2013 NSW sheep report; ‘live sheep, dead sheep and parasitised sheep.’

For those seeking a bit more detail, several district veterinarians in the eastern half of the state reported Haemonchus losses. Ted Irwin reported numerous cases of haemonchosis in the Warialda district despite dry conditions. In the Goulburn area, Bill Johnson noted that following good rainfall in late January, Haemonchus problems now predominate. ‘In one case, the owner of 160 prime XB lambs on a lush ryegrass pasture, on mustering them to draft of the tops to sell, found five dead and carried another ten to the yards. The lambs had been drenched 24 days prior with BZ/Lev, but then spent a few days in a contaminated creek paddock.’ Bill considers that the control of Haemonchus in some flocks is becoming difficult, with confirmation of mectin and closantel resistance more frequent.

While I have seen clinical disease I have also encountered several mobs with worm egg counts of several thousand, mainly Haemonchus but with no clinical disease. I presume that conditions were ideal for eggs to hatch for a few weeks in the late summer and early autumn but with drier and colder weather, conditions are no longer suitable for hatching, so the problem has not escalated. However, we still have to deal with pastures contaminated by larvae that hatched during the favourable conditions.

In an unusual parasitism of sheep, Lisa Martin (Tenterfield) saw an ascending paralysis in Dorset ewes infested with paralysis ticks (Ixodes holocyclus and I. cornuatus)). Lisa speculated that tick numbers have risen in part because bandicoot numbers have risen, in turn due to dingo control and wetter previous seasons creating more cover. Of interest, tick borne diseases seem to be increasing in importance in many parts of the globe. For example, Ixodes ricinus, the host of the causative agent of tick pyaemia and tick borne fever, Anaplasma phagocytophila, also appears to be increasing its range in Europe at present.

Many district veterinarians report pregnancy toxaemia in autumn lambing ewes. On the central tablelands, late summer early autumn rain was ideal for pasture growth. Ewes gained weight only to face declining pasture quality as winter approaches. Further south and west however, producers were less fortunate and conditions are dry. Both circumstances are ideal for pregnancy toxaemia. Bill Johnson reports from the Goulburn area that ‘feed is starting to become scarce away from the high country. Ewes were in fabulous condition for joining, but have lost weight during pregnancy. Few owners have begun to supplementary feed, waiting instead for rain on pastures to fill the feed gap. Some twin-bearing ewes are headed for disaster.’

Belinda Edmonstone saw cases of chlamydial polyarthritis in lambs on lucerne along the Lachlan River earlier in the season. This is the normal presentation for chlamydial polyarthritis, posing the question, why are rapidly growing lambs on the river valleys of the NSW slopes and plains susceptible to chlamydia. Does it occur elsewhere without manifestation or does it have a specific distribution in NSW?

Still on arthritis, Kasia Hunter, based at Condobolin was called to a case in which about 100 of 600 (17%) merino weaners had erysipelas arthritis. The owner usually only sees about 1% lameness in his lambs. Kasia speculated that the spike in prevalence this year might have been due to an increased marking percentage (114%), mismothering, and stress post lamb marking/mulesing. The lambs were born June/July, marked and mulesed in Aug, then shorn in January. Symptoms were first observed in the lambs in Dec/Jan.

Kasia also reported hypocalcaemia in a mob of weaned Merino lambs running in a cereal stubble paddock with supplementary oaten/wheaten hay and grain oats in feeders. They were not supplemented with any minerals (salt/lime) and the feeders ran out of grain for a couple of days, following which the lambs were mustered for drenching and started to collapse. Approx 25 from a mob of 3,000 died. The deaths stopped within a few days of providing the lambs with a 1:1 lime/salt ration as a loose lick. Analysis of bloods from live affected lambs and aqueous humour from one dead lamb confirmed hypocalcaemia.

There have been several reports of phalaris staggers this autumn. We have seen cases on the central tablelands as has Bob Templeton based at Braidwood. Bill Johnson commented that phalaris staggers necessitated the destruction of 6 of 80 stud Dorset ewe hoggets introduced for two weeks to an old phalaris pasture freshened by autumn rain. ‘The worst affected ewes progressed quickly to become recumbent; two more ewes continue to show typical staggers when disturbed.’

Colin Peake noted a few cases of grain poisoning in the far south west as grain feeding has become increasingly necessary. Tony Morton from Wagga Wagga was called to a case of grain poisoning following a silo accident, in which 700 lambs gorged on barley. The lambs were drenched (off-label) with Eskalin wettable powder (2 sachets with 3 litres or more of warm water to treat 300-330 head). Only 21 head died and the owner commented "it must be pretty good stuff as I am sure I averted a certain catastrophe here".

Tony and Amy Shergold report continued cases of crystal associated hepatopathy and photosensitisation in sheep grazing witch grass (Panicum capillare and not to be confused with the native perennial, hairy panic Panicum effusum). Jillian Kelly diagnosed photosensitisation in Merino ewes near Coonamble, attributed to cathead (Tribulus terrestris).Greg McCann at Dubbo and Ian Masters at Gundagai have also seen cases of ‘yellow bighead’ or geeldikkop in merino weaners that grazed on fresh Tribulus terrestris. In addition, Ian saw a case resembling facial eczema in sheep grazing a paddock consisting mainly of dry phalaris and rye grass (with no Tribulus, Panicum spp or St John’s wort). The paddock had been flooded last autumn. Histopathology indicated a toxic hepatopathy and Ian therefore suspected a mycotoxicosis.

Virulent footrot is down but not out. However, dry conditions are aiding eradication. Eliz Braddon from Young is taking advantage of dry conditions to inspect properties with a view to quarantine release. The Wagga team report tracing and inspections from infected properties. Ian Master noted that aggressive benign strains are making diagnosis more challenging in some instances.

Amy Shergold reported a case of presumed listeriosis involving 10 of 550 second cross ewes from a property near Uranquinty. They had been fed 3-year old silage that had been rodent infested and subsequently damaged. It was plastic-wrapped and the outside of the bales were obviously spoiled on examination. Of interest, while the mob consisted of lambing ewes and ewes that had recently weaned a lamb, only the latter group was affected. Amy examined four ewes in the paddock. She noted hypersalivation, unilateral ear drooping, circling and holding the head in a fixed lateral position. The producer reported that the ewes "were walking in circles in one direction until they crashed into you."

Amy also reported that the same silage had also been fed to cattle with no problems, although this ceased following the visit. This is consistent with previous observations that cattle are less susceptible than sheep.

Figure 1. A ewe with presumed listeriosis (photograph courtesy Amy Shergold)

Jillian Kelly (based at Dubbo) mentioned reports of poor scanning results from October-November joinings in the Central West, attributed to the dry conditions and lack of feed. ‘In the most extreme example of this, one producer near Nevertire scanned a mob of 800 ewes - in the first 100, there was only one ewe that was pregnant and so scanning was abandoned.’ Jillian found that both the ewes and rams were Fat Score 1.5 on average and had been ever poorer at joining.

Jillian also isolated Mannheimia haemolytica in a case in which four of 32 merino ewes suffered from mastitis near Gulargambone. Two died but two responded to oxytetracycline.

Redgut remains a problem for producers running lambs on high quality pastures and especially lucerne. A producer running 400 second cross lambs on lucerne flats near Canowindra told me that he lost 12 of 400 lambs from presumed redgut. The producer vaccinates the lambs at marking and again at weaning before running them on the lucerne. Losses commenced after the lambs had been on lucerne for 2-3 weeks and especially occurred a week or so after rain freshened the lucerne. The owner will supplement the lambs with grass hay and may graze them for four days on lucerne followed by three days on a grass-based pasture. Bill Johnson diagnosed redgut in a big mob of Dorper and Dohne lambs grazing lush lucerne. Fibre was introduced into the diet by way of a couple of round bales of rough hay, which the lambs avidly devoured. ‘The close contact around the hay aided an explosive pinkeye outbreak, with many lambs suffering severe bilateral corneal opacity and blindness. Weight loss was dramatic.’

 


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