Skip to content

Local Disease Watch for July

District vets in South East Local Land Services area have seen cattle affected by blackleg, liver fluke, grass tetany and ketosis this month. Sheep have been affected by liver fluke and barber's pole worms, phalaris staggers, pregnancy toxaemia and footrot. There is also a timely reminder about Hendra virus infection in horses.

Hendra virus precautions with horses

Hendra virus is a serious, usually fatal infection of horses and humans. Flying foxes carry the virus and occasionally infect horses. Humans only become infected with Hendra virus through contact with sick horses.

While no case of Hendra virus has been reported in this area yet, colonies of flying foxes visit, and tests show they have been in contact with the Hendra virus. More cases of Hendra occur in the cooler months. Horse owners should remain vigilant and take steps to minimise exposure of their horses. Keep horses away from flowering and fruiting trees that are attractive to bats. Any fruit lying underneath trees should be picked up and disposed of before the horses are returned to the paddock. Horse owners should talk with their private veterinarian about vaccinating their horse, and are reminded to use good hygiene practices when handling horses.

Deaths of cows from grass tetany

Grass tetany is a complex disease which kills many cows in southern NSW. Several properties have reported deaths already this season, and more are expected as calving gets into full swing. Most cows die suddenly, seemingly from a heart attack, while others show nervous signs (aggression, trembling and staggers) or are found unable to rise. Without swift treatment, they die.

In its simplest form, grass tetany is caused by a deficiency of magnesium. Green grass pastures are low in magnesium, and cows need a lot of it soon after calving. Most grass tetany cases occur in middle-aged high-producing cows, which are low in calcium and energy as well as magnesium. Interrupting grazing through bad weather or yarding, high soil potassium, low sodium (salt) in feed, cold overcast weather followed by a couple of warm days, and lack of clover in pastures can all further complicate this disease.

Your district vet can collect samples to determine the cause of sudden deaths in your cows. Better still, ask about measures to protect your cows from grass tetany. These include providing magnesium supplements, preferably on hay, to high-risk cows; and keeping them away from paddocks where deaths have occurred previously.

Barber's pole worms still affecting sheep

Despite the onset of winter, some sheep flocks are showing weakness and anaemia caused by barber's pole worms. While the eggs of this worm cannot hatch in winter, pastures will remain dangerous if contaminated during the warmer weather. There have been several deaths in one flock which was only drenched six weeks previously, indicating how rapidly sheep can become re-infected. Declining pasture quality and onset of lambing both increase the risk from this parasite.

Trials of a new vaccine against barber's pole worms have been undertaken in northern NSW this year. The results show the vaccine works. However, it is relatively costly (about 60c a dose) and boosters are required every six weeks during the warmer months. Vaccination may prove useful to protect coastal flocks from barber's pole worms in future, while traditional methods of control (drenching and pasture management) continue to be more economical in tableland flocks.

Footrot in sheep

Despite recent media reports suggesting that footrot in sheep is rife, only one new footrot case was detected during targeted flock inspections this month. There are currently only 25 footrot-infected properties in South East LLS region, and all affected producers are working hard to clean up the problem. Several part-properties have been recently cleared of footrot and released from quarantine, with more to follow in coming months. The level of cooperation our staff receives from these producers is outstanding, so it is a blow to morale when the media only reports on the problems being faced rather than the achievements.

Blackleg in cattle

Blackleg is one of the clostridial diseases we vaccinate for using five- or seven-in-one vaccines. So prevention should be pretty straightforward. Deaths from blackleg occur suddenly in young cattle, mainly on the coast and hinterland. There is frequently an association with bad weather. In one recent case, ten of thirty young cattle died from blackleg on a south coast holding. As often happens, the cattle had received a dose of vaccine at calf marking, but no follow-up booster. Cattle producers are reminded to follow the label in vaccine packs, particularly regarding the requirement for second and subsequent doses. Giving a single dose to previously unvaccinated cattle is a waste of time and money.

Liver fluke

Reports of problems with liver fluke are on the increase, in both sheep and cattle. Liver fluke requires a small freshwater snail to complete its life-cycle, so stock grazed in paddocks with creeks or swampy areas are at risk. Sudden deaths of sixty ewes occurred due to "acute" fluke infection, where large numbers of immature fluke irreparably damaged their livers. The damage meant several more sheep died despite treatment. Cattle with illthrift and weight loss were also found to be infected with liver fluke, and will take some time to regain the weight following effective treatment.

Your District Vet can help with testing for liver fluke and advice on treatment options.

Pregnancy toxaemia in ewes and ketosis in cows

The quality of pastures available to ewes and cows in late pregnancy has declined markedly on many district properties, causing a crisis. Some ewes and cows were over-fat when joined, and now face an uphill battle to maintain that body condition. The situation is exacerbated when they are carrying twins.

Affected animals become dull and listless, and separate from the mob. Ewes often gaze into space. They stop eating, go down, and die. Finding one animal affected is a signal that others in the mob are border-line. Treatment is only partially effective once animals have gone down. Increasing the energy available in the diet is critical, either with a move to better pasture, or better still a high-energy supplement such as grain or pellets. Be mindful that too much grain or pellets too soon can be fatal, so follow recommendations to gradually increase the quantity of these supplements.

Bill Johnson
District Veterinarian
4824 1910