CASE NOTES


STATE REPORT AUTUMN 2012

Bruce Watt, SDV Tablelands

Rainfall across most of NSW has been above average over the summer and autumn creating conditions that are ideal for flystrike and haemonchosis. Eliz Braddon based at Young summed this up. The vast majority of my time in the past 4-6 weeks has been spent dealing with BPW outbreaks in flocks causing up to 10% mortalities. At least three of these flocks have ML resistance as a feature, one of which was moxidectin resistance. These comments were echoed by Alan Taylor (Molong) and Belinda Edmonstone further west at Forbes and Kath Marsh further west again at Condobolin. Kath summed it up as worms, worms, foot abscess, worms! Big issues with Barbers Pole Worm since October, which has obviously got worse in the last month. Belinda added BPW like we have never seen. The problem has escalated in the last month. I think paddock contamination has built up over summer that many people have reached a crisis point. Lambs circulating through lush lucerne paddocks over summer can no longer graze these paddocks (despite abundant feed) as they are so dirty. Belinda also reports a fair bit of BPW mectin resistance. Greg McCann (Dubbo) also noted losses occurring about a month after the use of a knock-down drench. He agreed with Belinda, remarking there have been some magnificent lucerne stands produced as a result of last years rain, but these pastures have now nearly become a no go zone for young sheep without a sound drenching strategy.

Bill Johnson based at Goulburn has also seen serious and ongoing haemonchosis although he commented on a case where BPW was unfairly blamed. A recent outbreak of enterotoxaemia in lambs was thought by the producer to be barbers pole worm; the carcases looked a bit pale to him, just before they turned black. Bill commented on the difficulty of finding Haemonchus control options for lambs being finished on crop. These paddocks are heavily contaminated and with lambs dying close to market weight, effective drenches need a short ESI.

Redgut was a problem for some producers with excellent lucerne pastures. However, the problem may not have been as bad as expected. Ian Master (Gundagai) commented that he has not seen redgut despite great lucerne pastures all summer. However, he did see a case of enterotoxaemia in crossbred lambs on fresh lucerne. Jillian Kelly (Dubbo) was called to a case of redgut in crossbred weaner sheep near Narromine. They had been grazing lucerne with access to rough straw hay for a couple of months with no problems. However, recent showers meant the lucerne was particularly lush, and red gut killed 16 out of 120. Moving them out of the lucerne onto native pasture stopped the deaths. Belinda Edmonstone had many reports of redgut about a month ago (February March) however this seems to have settled down perhaps they are all dying of worms on these lucerne paddocks now!

Dan Salmon from Deniliquin and Colin Peake from Hay report a spate of pregnancy toxaemia. Some of it was following the stress of the severe rainfall event early in March, but some of it is a result of other stresses on fat ewes carrying twins and grazing relatively lush pastures. Kath Marsh (Condobolin) is starting to see plenty of foot abscess in heavier sheep, with associated pregnancy toxaemia in ewes. Jillian Kelly has also seen several cases of pregnancy toxaemia in lambing ewes around Nyngan. All cases were in fat ewes bearing twins/triplets. Deaths stopped on introduction of grain.Jillian considered that the pasture is not as good as farmers think this year, and multiparous ewes just cant fit enough grass in to supply their energy requirements!

Several DVs report recent cases of Mycoplasma ovis infection. I saw this problem quite frequently when at Condobolin but have only seen one (unconfirmed) case on the central tablelands in my six years here. Colleagues occasionally report it elsewhere on the eastern tablelands. Steve East wood for example has seen two cases in the last month in Armidale (one with concurrent coccidiosis). Steve added M ovis , I suspect, is underreported given BPW is a normal summer occurrence and assumed to be the main cause of anaemia in weaners. Alan Taylor (Molong) commented on a case in which M. ovis and Haemonchus may have been concurrent.

In general, M. ovis seems to be more frequently reported on the western slopes and plains. In my experience, the problem was strongly associated with mulesing (occurring 4-6 weeks after the event). Dan Salmon commented that in the Riverina it usually occurs during the winter, which is interesting because the biting insect population is usually sparse. Dan commented last week I saw it in Dorper lambs which had never been mulesed and were marked last year. Off the top of my head I would guess that less than half of the incidents that I have seen directly follow mulesing. He has seen other acute cases recently including one involving 10% of a mob of 6000 lambs that were anaemic and lost condition a month after the rainfall event. Jillian Kelly investigated a case of ill thrift and anaemia in lambs in conjunction with the local private practitioners. She diagnosed M. ovis on pooled PCR, while direct examination of smears was negative.

I have recently seen a case of OJD staggers in a mob of 1,000 crossbred lambs on their mothers. The lambs were vaccinated with Gudair in late January. Seven to 8 lambs were noted with hind limb weakness and a tendency to collapse when pressed. The two autopsied lambs had a 5 cm granulomatous mass pressing on the cervical cord. Bill Johnson was also called to an outbreak affecting 11 of 800 fine wool merino weaners. The lambs were Gudair-vaccinated at weaning, with the first lambs affected from 3 weeks later. The flock had a history of genetic neuropathy, and the lambs had been grazing lush phalaris with abundant marshmallow on the sheep camps. The owner had seen similar cases every year. They displayed progressive forelimb paresis initially only when mustered. A spectacular granulomatous mass extended from the cervical musculature to the spinal canal, causing compression of the ventral spinal tract.

Bill Johnson reported that a local practitioner diagnosed acute salmonellosis in a 2000-head opportunity lamb feedlot, which has so far killed ninety lambs. Ten percent of 200 lambs in one pen died the first night. The Salmonella typhimurium isolate is resistant to OTC.

DVs from across the state also report pink eye in all classes of sheep. Jillian Kelly has seen multiple cases in the last few months near Dubbo, Nyngan, Tottenham, Warren, Carinda and Coonamble. She has tried to isolate the organism via culture of swabs (Branhamella and Mycoplasma) and Chlamydia serology but all negative in all cases investigated. She asked is there another bug causing it, or am I just missing it?

Evelyn Walker based at Dubbo reported severe losses in a mob of newly purchased weaner sheep delivered to a Nyngan property. The sheep were hungry when they got off the truck and chewed out yards infested with weeds including Crown Beard and Nettle Leaf Goosefoot. Within 24 hours, sheep displayed various symptoms knuckling over in hind limbs, falling, spontaneous tetanic limb spasms, severe tachycardia and hyperthermia. Although there was no indication of polio-encephalomalacia (PEM) on brain histopathology, affected sheep responded favourably to several days of twice-daily thiamine injections. Nettle Leaf Goosefoot (Chenopodium murale) has high levels of sulphur, which may cause PEM. On the subject of unusual plant toxicities, Jillian Kelly was called to another case of Humpy Back in full wool aged Merino ewes at Tullamore. Quena or Wild Tomato (Solanum esuriale) was present in the paddock, although it looked deformed due to a sub-lethal herbicide application.

With the damp conditions, DVs are reporting foot abscess and strawberry footrot. Jim McDonald from Yass commented that strawberry footrot is emerging on properties with strong clover pastures. Steve Eastwood (Armidale) and Andrew Biddle (Glenn Innes) also reported strawberry footrot. In the discussion about the relative contributions of Dermatophilus versus orf, Dan Salmon commented, the limited EM that I have had done on strawberry footrot have all been orf. I call most of them orf based on the presence of lip lesions. On several occasions scabby mouth vaccination has prevented recurrence of longstanding problems. Steve Eastwood considers that in his area most are mixed infection with orf (with mild oral lesions). He rarely sees Dermatophilus alone. Andrew Biddle however saw a number of very wet very lame ewes this year without mouth lesions and with moist red hair loss was up the back of the heels. He commented that because diagnostic testing is expensive, and because at least some responded to well to penicillin, that Dermatophilus was more likely.

Foetal loss is occasionally reported as a problem. I have investigated some of these without establishing a diagnosis. Greg McCann has had a similar experience, commenting that sheep scanners around the Central West are reporting higher numbers of abnormal twins, aborted and resorbing pregnancies. Although we have attended several cases, we are yet to find a cause, despite extensive testing. Continuing the reproduction theme (or lack of) Shaun Slattery and Derek Lunau reported a case of ulcerative balanitis (affectionately known as galloping knob rot) of unknown aetiology in a mob of 27 young Border Leicester rams from the Walgett district. Stay tuned for some eye watering photographs and more detail in a case report in preparation. Shaun added as an aside, the owner sought extra ram power in the form of older rams from another property. He was persuaded to test for OB before using, with 20/25 positive.

Greg McCann reported chlamydial polyarthritis in a number of flocks of lambs post weaning. High titres have been recorded in the investigated cases with a good response to oxytetracycline treatment. All cases have occurred in rapidly growing lambs often on lucerne. The kerato-conjunctivitis sometimes seen in chlamydial polyarthritis cases has not been a big feature this year. Colin Peake (Hay) also saw a case of polyarthritis in 6-8 month old White Suffolk x merino lambs in which 20-30 affected of 120. Colin commented that the distal limb joints were very swollen hot and painful. This is unusual for chlamydial polyarthritis but titres ranging from 32 to 128, a rapid response to oxytetracycline and negative joints cultures supported that diagnosis. Kath Marsh confirmed a case of erysipelas arthritis in thirty of 550 6-month-old crossbred lambs from near Naradhan. Affected lambs showed firm fibrosed swelling in one or more joints. Erysipelothrix rhusiopathiae was cultured from all three joints submitted to the laboratory.

Finally a comment on what appears to be a dramatic change in drench resistance across southern and central NSW. Eliz Braddon and colleagues Belinda Edmonstone and Kath Marsh are undertaking an extensive drench resistance survey (43 properties to date) among sheep producers in the Lachlan LHPA. They found that 43% of properties have evidence of abamectin resistance in Haemonchus and 20% have resistance in Trichostrongylus. Jim Kerr commented when I left the Scone RLPB at the end of 2007, closantel was still effective in nearly all flocks in this predominantly barbers pole area. Worm tests now suggest that closantel resistance is common. Jim attributed much of this to importing resistant worms. We have also recently conducted 15 FECRTs on the central tablelands and have found that abamectin is 95% or more effective against Haemonchus on 20% of properties. Abamectin is fully effective against Teladorsagia on 71% of properties and is fully effective against Trichostrongylus spp on 77%. Is this a rapid change or are we just not good at detecting low level, emerging resistance?

 


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