Local Disease Watch - December 2015
District veterinarians visit farms to investigate herd and flock problems in livestock. The information we gain from these investigations improves livestock production and animal welfare, and helps to ensure that Australia is free from certain animal diseases.
During the month, district veterinarians on the coast saw an increase in mastitis cases in dairy cows associated with wet conditions, and high levels of liver fluke. Inspections of lame sheep in all areas found a range of conditions, including virulent footrot, foot abscess, scabby mouth and infectious arthritis. Cattle with sore eyes had pinkeye in some herds, and a viral infection in another. Worms slowed growth of young cattle despite recent drenching, and a microscopic parasite mimicked worms in lambs. Worms also caused the death of an alpaca.
Worms in young cattle
The message from many research trials is that cattle over two years of age rarely benefit from worm drenching. But the detrimental effect of worms, particularly brown stomach worms, on young cattle should not be underestimated. One recent trial using tablelands cattle showed worms alone reduced liveweight of beef heifers by 50kg. Bodyweight is the main factor which determines puberty in heifers, so worms can have a large impact on heifer fertility.
Worm control programs in tablelands beef herds stipulate drenching at the same time as a paddock change to a low worm pasture, in early August. This year, some herds which closely followed this program were caught with yearling cattle which by October were obviously worm-affected. These cattle were usually scouring, had not lost their winter coats, and were in lower body condition score. Worm egg counts on dung are not that reliable in cattle, so blood tests were used to diagnose the condition. A further drench and another paddock change reversed the weight loss.
Worms and other parasites in sheep
Several consecutive warm rainy days not only disrupted shearing schedules but were ideal for hatching of Haemonchus (barber's pole) worm eggs. While no outbreaks of disease due to Haemonchus have been seen yet, some mobs have high worm egg counts which are predominantly barber's pole. Remembering how quickly a few barber's pole worms become a lot, managers of sheep flocks in all parts of the district need to be vigilant.
Apart from high worm egg counts, blood-sucking Haemonchus causes anaemia (check for pale skin and eyelids), weakness and sudden death. Several producers have noticed these exact symptoms recently in well-grown un-weaned lambs, about six weeks after marking and mulesing. In one case, a few bigger lambs were found dead in the paddock, while on two other properties, a lamb dropped out during mustering and died when lifted onto the ute. These lambs had "infectious anaemia" or M.ovis infection. Several bigger flocks in the district have seen M.ovis for the first time ever, this year. An autopsy confirms the diagnosis and rules out Haemonchus. Mustering and handling of lambs affected by M.ovis anaemia often kills them, so it is important to work out early whether the anaemia is due to M.ovis or Haemonchus.
Elsewhere, sheep are carrying significant black scour or brown stomach worm counts. It may be tempting to delay weaning, given the amount of green feed about, but lamb growth rates will be retarded by worm build-up in lambing paddocks.
Despite late rain extending the green of spring, it has hayed off enough for a first summer drench.
Blowfly activity has ramped up in response to showers. Any sheep with a few wet dags has been a prime target for breech strike, and winter-drop crossbred lambs are being struck on the shoulders and back. Watch the withholding period on blowfly products, as different restrictions apply to meat and wool. Your treatment of choice may differ, depending on when you intend to sell, or whether you intend to retain and shear some lambs later. Wool withholding periods for blowfly products range from nil to three months. And don't forget a poll treatment for rams. Flystrike on the head is common in fighting rams at this time of year, and may cause the ram to be infertile for two months or more - which is right about the time you wish to join.
Infectious arthritis in lambs
Nothing is more distressing for a producer than seeing crook livestock that can't be cured. Infectious arthritis is like that, and some sheep flocks have been badly affected this year. This infection usually involves bacteria which are ever-present in sheep paddocks, and which enter the body either through the navel or more commonly after marking and mulesing. Managers of affected flocks have done nothing different this year, and the condition has commonly only affected one or two mobs on the farm. One likely culprit is the irritation caused by myriads of flies, particularly bush flies. Fly products used at marking usually have no repellent effect.
Alpacas and worms
Authorities went to great lengths to ensure that alpacas were worm-free when imported into Australia. While those measures were largely successful, alpacas readily pick up worms from other species, including sheep, goats and cattle. Alpacas mostly use common toilet areas, which trap worm eggs in communal dung piles. Heavy stocking rates or co-grazing alpacas with less meticulous animals like sheep or goats leaves them prone to heavy worm burdens.
An alpaca used as a fox sentinel for sheep and goats died recently from blood loss due to barber's pole worms. This reminds us to treat these guard animals at the same time as the stock they protect, to keep them healthy.
Further information: DPI Primefact on alpacas and worms