Much of NSW is experiencing an exceptional season. Bill Johnson from Goulburn commented that for his area this is the third consecutive wet mild summer. Jillian Kelly based at Dubbo reported continued heavy rain (with some areas around Coonamble have had 5 inches of rain in the last 6 days) and we have all heard the news reports of flooding rain in the north. Consequently, district veterinarians from across the state report that internal parasites are or will become a major problem. Bill considered that in his area sheep producers are better prepared this time, with significant increases in the amount of worm monitoring. However, Haemonchus continues to be a major threat, with resistance to long-acting drenches confirmed on some properties.
Tony Morton from Wagga Wagga remarked that above average rainfall over the summer is causing both carry over Teladorsagia and Trichostrongylus problems as well as emerging Haemonchus. Bob Templeton from Braidwood reports a similar picture and Libby Read based at Narrabri noted that Haemonchus is a major issue in the north west again this year. David Thomson reports that on the north coast, worms continue to be a difficult issue with a lack of response/resistance to combination wormers, almost all sheep on small blocks, many with little internal infrastructure, and a relatively mild, damp spring-summer so far.
Despite the high prevalence of fluke on the central tablelands (as judged by both abattoir surveillance and serological surveys), I have seen remarkably few cases of clinical fascioliasis in my time on the central tablelands. However, Dan Salmon reported that while liver fluke have practically disappeared from the southern irrigation areas with the improvement in layouts over recent years, seven of 300 ewes died from acute fascioliasis with no apparent illness before death. On post mortem, the liver had extensive fluke migration tracks and there was haemorrhage into the peritoneum.
Dan also noted a disturbing diagnosis of lice in a mob of sheep that had been treated with one of the new off-shears pour-on treatments. It was only one sheep out of several thousand and there were only a few lice in one localised area and it was several months after treatment so there are no real grounds to blame the chemical. However, Dan opined that these incidents are what led to lice becoming resistant to the pyrethroids and IGRs. A better news story on this subject came from Jillian Kelly who reported that a producer near Warren was concerned about lousy sheep a few weeks after plunge dipping using a contractor. On examination, these sheep were found to have no sign of lice, but a heavy corkscrew grass burden, which appeared to be causing the itching.
Jillian also recently diagnosed a case of humpy back in ewes north west of Nyngan. The sheep were full wool merinos grazing paddocks with plenty of Solanum esuriale (Quena or Wild Tomato) plants with fruit. If like me your next case of humpy back will be your first, you will no doubt like to refresh your memory with AVJ papers; O’Sullivan 1976 52:414-418 and McMeniman 1976 52: 432-433.
Jim McDonald from Yass reported pinkeye in merino weaners, which he attributed to a combination of flies, long grass and yarding. Jillian Kelly has also seen several cases of pinkeye in the Dubbo region. Libby Read diagnosed coccidiosis as the cause of ill thrift in weaners on one western merino property. The lambs were effectively set stocked in a small area because of an abundance of rank feed in the remainder of the paddock. She predicts that with wet weather and flooding continuing, her area may see more of this stress-related problem in set stocked youngsters. Libby has also been monitoring for ovine brucellosis in a number of commercial flocks in the Walgett region, with about one in three being positive. She noted the continued need for biosecurity and ongoing monitoring.
Dan Salmon based at Deniliquin reported an anthrax incident where 30-odd sheep died. This was in the southern Riverina within the traditional anthrax endemic area where there is a case every few years. The deaths stopped three days after vaccination. Dan noted that the carcass was not particularly autolysed considering the hot conditions and there was no blood, dark and tarry or otherwise, coming from the orifices. However, the immunochromatographic test (ICT) (the newly developed rapid, in-field, test for anthrax) gave a strong positive and infection was confirmed by smear and PCR.
Steve Whittaker based at Albury excluded anthrax in the sudden loss of 15 of 900 crossbred lambs in a flock that adjoined a property with a confirmed anthrax history. Steve commented that the ICT kit proved valuable in quickly alleviating owner (and DV) concerns in relation to the possibility of anthrax and permitted relatively safe autopsies to be conducted, establishing the diagnosis of summer pneumonia.
Tony Morton diagnosed OJD by post mortem in 2 of 850 ill thrifty 4 and 5 year old unvaccinated merino ewes. Both ewes were in light condition, one was scouring and yet the balance of the mob was in very good order. Tony commented that fortunately the owner started Gudair vaccinating a few years ago. As the younger age groups are all vaccinated losses should be light, providing the vaccination program is continued.
Bill Johnson remarked that the current value of sheep has reignited interest in OJD vaccination. Some owners of vaccinated flocks are concerned to investigate continuing OJD losses of 1-1.5% of 4 and 6 tooth vaccinated ewes, while one purchaser of unvaccinated merino ewes from the OJD high prevalence area has recently lost 40% same age ewes. Bill commented that one of his most frequent enquiries regards the feasibility of vaccinating merino wethers with Gudair® at twelve to eighteen months of age. It seems that breeders who saved on OJD vaccination of wether lambs based on limited re-stocker interest at that time now face a dilemma. OJD vaccination status has become a major selling point at recent ram and first cross ewe sales and few lots are offered without it.
I have seen a number of cases of enterotoxaemia on the central tablelands. In most cases, it has been at least 12 months since their most recent vaccination. Jillian Kelly has also seen cases of enterotoxaemia predisposed by the wet summer and lush feed conditions. She reported that one producer near Coonamble lost 50 unvaccinated weaner lambs. On examination and post mortem some had classic acute enterotoxaemia (sudden death, fibrin clot inside pericardium, glucosuria immediately post mortem) while others had evidence of Focal Symmetrical Encephalopathy (head pressing, lethargy, blindness). Deaths stopped within a week of vaccination.
I have seen two cases of chlamydial polyarthritis in prime lambs grazing on lucerne. A group of DVs with an interest in this condition are developing a project to investigate this intriguing problem further. I aim to report on this in a future edition of this newsletter. The Wagga office has also had a number of calls concerning arthritis in lambs less than 12 months of age. Bill Johnson considered that an outbreak of septic cellulitis and arthritis in about four percent of a mob of roughly shorn crossbred lambs was predisposed by phalaris staggers. The lambs were weaned, shorn and placed at a high stocking rate on magnificent lucerne. Affected lambs were noticed to be lying around, stumbled when disturbed, were dehydrated and febrile, and had developed putrid abscesses associated with shearing cuts presumably from wound contamination in lambs more recumbent than usual. They had been reared on an almost pure stand of Australian phalaris, with phalaris toxicity confirmed by histopathology.
I was interested to learn that Tony Morton has seen pneumonia as the apparent cause of lamb losses at Old Junee where there was also some underlying evidence of possible toxic plant damage. Pathologist was unable to attribute the damage to a specific plant or toxin. I have seen a similar case near Cowra. A producer who routinely buys weaned lambs to fatten on lucerne and stubbles, last year presented with both pneumonia and liver disease. The problem has recurred this year. The pathologist’s interpretation is that the liver pathology is chronic with adequate functional reserves. The problem presents similar to bovine respiratory disease, ‘shipping fever’ in cattle.
With the wet summer, photosensitisation cases are to be expected. Tony Morton reports fielding many calls involving suspected witch grass (formerly hairy panic) photosensitisation. St John’s wort poisoning has also be more prevalent that usual on the central tablelands this year. Because it is a perennial, it appears to have flourished under reduced grazing pressure. Merino breeders reported problems in merino lambs but usually not their mothers. I have just seen a case involving black headed Dorpers. Only the white parts of the back and flank were affected so that the lambs were spared the usual eyelid, lip and ear damage seen in white skinned breeds.
Tony Morton noted the usual summer enquiries regarding grain poisoning. He commented that storm damage may mean more full heads of grain available than normal. Tony has advocated the use of virginiamycin (Eskalin) in both treating and preventing grain poisoning and commented that Eskalin wettable powder will shortly will be back on the market.
Finally, Dan Salmon commented on footrot in the Riverina, noting more cases than desirable. However, on a positive note, no cases were carryover infection from the footrot eradication program. All cases had been introduced within the previous 12 months, almost invariably from the footrot residual area to the south. This is reinforcing the hard lesson, which Riverina sheep producers used to have to learn every 20 years, or so: footrot does not disappear of its own accord if the weather gets dry.