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Victoria worms, flies and lice update - April 2015

VIC WormBoss Worm Control Programs

VIC WormBoss Drench Decision Guides


Hamilton: Andrew Whale, Livestock Logic (a.whale@livestocklogic.com.au)

Livestock Logic Key Recommendations

  • Any animals without a WEC since Feb should be checked promptly.
  • Then focus egg counting on weaners in middle of May and then WEC weaners fortnightly. Once they begin to rise, turn your attention to the next most at-risk mobs, 1½ yr olds.

We have had sufficient rain in the South West to get germination and essentially give us an autumn break, the next few weeks will be critical to determine if it turns into a good autumn break or not. I was on a property south of Hamilton (Macarthur) with over 1200 kg of FOO (Food On Offer) yesterday, the paddock had been locked up for 4 weeks since rain. North of Hamilton there is a green tinge but that’s about it so far.

The chart below shows that our lab’s egg counts have dipped significantly as predicted after rain in Jan followed by a very dry February and March. We expect weaner egg counts to be on the move from mid May and would encourage clients to focus their testing on weaners for around the middle of the month. Testing in early May is likely to be too soon after the autumn rain event and a low count will give a false sense of security.


Figure 1: Percentage of  Sheep Requiring Drenching from Livestock Logic Laboratory

After the autumn break weaner egg counts will typically rise more sharply than mature sheep due to their lack of immunity to worms. For this reason, this is the group that should be closely monitored due to normally being in the lowest body condition score; they are also least able to handle a significant worm burden, so need earlier treatment to minimise production losses. Focus your attention on this age group and monitor frequently; make your weaners the priority!!!

For the autumn lambers out there it is worthwhile doing an egg count on ewes pre-lambing. As the graph shows, most adult sheep have very low egg counts and there will be next to no benefit from drenching in most flocks that had good summer worm management. You cannot kill worms that aren’t there.

Benalla: Tricia Veale (triciav7@bigpond.com)

There was very little rainfall in this area last month with a total of 6 mm.  Farmers were very concerned as the water levels in the dams were decreasing rapidly. The paddocks were completely bare and they were having to feed the stock with hay. However, finally this month there has been a really good autumn break with 61 mm so far, but we do need more rain! 

Worm populations appear to be at low to moderate levels, so it's good to check out what is happening on your place by getting a worm egg count done. Coccidian oocysts can also be identified during this test.

Some farmers have reported that sheep are now scouring badly. This has often been found to be due to moderate numbers of coccidian oocysts. Coccidia live inside the cells of the lining of the sheep’s intestine. From within these cells they can produce thousands more coccidia that pass out with the dung. These are known as oocysts and are the resistant stage of the life cycle. They remain dormant on the paddock at this infective stage for some time, providing that weather conditions stay favourable. Winter frosts often do kill the oocysts, but enough survive in sheltered spots to continue the cycle next spring.

Animals then eat the oocysts with grass and they pass down into the gut. The oocysts cell walls split open and very tiny tadpole-like sporozoites emerge. These can glide along the gut rapidly and they then enter the cells of the intestinal wall. Multiplication takes place in these cells, which eventually expand to the stage where they break open to release huge numbers of coccidia. The intestinal lining becomes irritated and inflamed. The animal’s body copes with this situation by sending down water to cool things off. This often results in scouring and diarrhoea. Young animals can become anaemic and suffer dehydration, weakness and loss of weight.

Coccidia infections are often self-limiting, they do resolve themselves. In the absence of re-infection only one cycle of development takes place. However, under natural conditions,repeated infections usually occur.

Young animals of all species are highly susceptible to coccidia, whereas adult sheep and cattle do develop a very good immunity to them.

Some farmers have often said that they can tell if animals need drenching by looking at them. This is not accurate as scouring may be from Coccidia or another cause. A worm test can save you hundreds of dollars if they don’t need drenching. Drenching unnecessarily can also contribute to drench resistance.