Mud maps and misconceptions

Mud Map of Australia (WormMail 200906041730)

(See link, below)

I was talking to a colleague recently about misconceptions we have about sheep worm control in various regions.

For example, some New Zealanders might have a particular view of Australia that is half-right, and vice versa.

This is not to suggest that Kiwis (Keen Interest Without Intelligence, the joke goes) are clueless or complete idiots. Some of the colleagues I highly respect are Kiwis. One of them recently said “I am not a complete idiot – some parts are missing”.

Jokes aside, there is probably no-one who has a really good understanding of sheep and cattle worm issues in all regions, although some might come close.

So, misconceptions or half truths are to be expected.

I cobbled together a map to give a thumbnail sketch of climate, sheep distribution, and other worm-related information. It might be of interest to some, if you can read my scrawl. Excuse the bad jokes.

Mud Map of NSW

(See link, below)

With the advent of LHPAs (see below), I decided to draft a map of New South Wales with the new LPHA boundaries (and the old RLPB ones), overlaid with isohyets, summer vs winter rainfall boundaries, and some redrawn ‘worm region’ lines. This is a work in progress.

The original boundaries for DrenchPlan and WormKill were drawn to fit PP Board boundaries, and climatic zones. So, ‘WormKill’ – launched in 1984 and designed to manage Haemonchus/Ostertagia/Trichonstronglyus in particular – covered the north-east of the state, and DrenchPlan, launched a year later, covered the non-seasonal and winter rainfall areas of central and southeast NSW, where Ostertagia/Trichostronglyus are the main issues. (Fasciola – liver fluke- of course is very important in some areas as well).

The lower rainfall areas of the western NSW planes (the ‘Western Division’) got their own programs – FarWestWorm and WestWorm – in 1998.

There are two problems with using PP Board/RLP Board boundaries. Firstly they are susceptible to change, given our penchant for reviews (some of which may be good). Secondly, being based (I think) more or less on old Police District boundaries (and/or Parishes??) from the 19th century (when this system was set up to deal with sheep scab), most people don’t know exactly where the boundaries are.

So, I decided to shift the worm region boundaries a little to line up with lines between towns, for example, assuming that location of the towns is less likely to change.

LHPAs, RLPBs and PP Boards

For those not familiar with rural New South Wales, this state is unusual in that it has an extra form of ‘government’ that funds itself by way of rates levied on local land-holders, mainly for the purposes of animal health and pest management. As intimated above and in an earlier WormMail, this system started in the 19th century for the purpose of dealing with sheep scab (1863 Scab in Sheep Act). (And NSW knocked off sheep scab before the other states, and the ‘mother country’ (for all you AngloCelts)).

In relatively recent times, the Pastures Protection Boards had a name change to Rural Lands Protection Boards, and some PP Boards were absorbed into others, e.g. Carcoar, Pilliga, if not at the time of the name change. The most drastic reduction in the number of these districts came into effect in January this year, when 14 Livestock Health and Pest Authorities replaced the 47 RLPBs in the state. The new logo is nicer.

From my point of view, one of the really good things about PP Boards/RLP Boards/LHPAs, is the District Veterinarians. This is an animal health management resource that other states don’t have. But then, I am not a ratepayer.

Other states have their idiosyncrasies. It was only when working on the WormBoss committee to develop WormBoss that I discovered that South Australia has a system of land division called ‘Hundreds’, which was formerly used in England and other countries.

More on Misconceptions

Here are some misconceptions that surface from time to time:

* Extrapolating from ‘summer drenching’ areas of WA to other areas

As you know, since modern strategic programs came into play in the 1980s (WormKill (1984), DrenchPlan (1985), then WormPlan (Vic), WormBuster (Qld), CRACK (WA) etc, in no particular order), the non-seasonal and winter rainfall sheep raising areas have used summer drenching. A drench at summer (followed in some areas by a drench at the end of summer), was much more effective than several drenches in the wetter parts of the year when clinical parasitism tended to occur.

But then WA got ivermectin resistance in Ostertagia (Teladorsagia) in double quick time, and strategic drenching copped all the blame. There was a renewed emphasis on refugia as a factor in the development of drench resistance (in addition to the other well-known factors). Ivermectin was released in Australia in 1988 and the first reports of resistance occurred several years later: Le Jambre et al (1993; Haemonchus – northern NSW); Besier et al (1994; Ostertagia – WA). See NSW DPI Primefact 478 – ‘Drench resistance and sheep worm control’.

The upshot of all this was that some argued that summer drenching in southern NSW should be jettisoned on the basis of the WA situation. While general principles of sheep worm control are transportable, the region-specific principles may not be. The only pertinent similarities between south western WA and southern NSW are summer drenching and sheep. A cursory look at the climatic data shows they are quite different. This is discussed in Primefact 479, ‘…summer vs winter drenching in southern NSW’.

* WormKill, recipes and other furphies

There are various misconceptions about WormKill, some of them amusing.

WormKill was the first of the ‘modern’ strategic sheep worm control programs, being developed for the Haemonchus– endemic area of NE NSW by CSIRO scientist Keith Dash, building on the pioneering work of CS(I)R(O) scientist H McL Gordon. Three critical factors for the success of WormKill were the grandfather and father of WormKill, Hugh Gordon and Keith Dash respectively, and the release of closantel in 1982. Closantel has sustained activity against Haemonchus. There were other factors of course.

Pasted below are images of Gordon’s and Dash’s strategic programs:

Which WormKill?

The figure above/right is what most people remember about WormKill – that or the first version – and the fact that it was so simple and memorable was part of its success. However, supporting advisory material was also developed and in addition there were successive revisions of WormKill. What also escapes attention is that the various iterations of WormKill are built on a foundation of epidemiological principles, and the core of these principles undergird all sheep worm control programs today.

Most commentators do not make it clear to which version of WormKill they refer, but probably it is the initial version (1984) which they have in mind.

An early version (pictured above) included grazing management at a time when IPM was not yet a household acronym. Other elements of IPM were added in following years.

Early versions of WormKill may be described as a ‘recipes’. Indeed it was a simple, prescriptive expression of the underlying principles. And it worked a treat (more on that later).

However, from the outset, there were variations of WormKill – for different lambing times etc – and the enunciation of various worm control principles – in supporting advisory material. So, a recipe, yes, but not quite as rigid as a cursory examination might suggest.

After a short time, still in WormKill’s golden era (~ 1984 – early 1990s, before closantel resistance took off), other versions of WormKill were added, reducing the number of closantel treatments from three to two or even one per year on those properties were regular worm egg count monitoring (yes, WECs were advocated) showed that fewer treatments would suffice.

With closantel resistance on the increase, WormKill was further revised (under the guidance of Marcus Holdsworth, who had taken over from Betty Hall as Veterinary Officer, Armidale), reducing the interval between closantel treatments from 12 weeks to eight.

Alas, such details often go unmentioned, which leads to misconceptions.

WormKill was OK – there was nothing better

Faint praise is another way that history is re-written and misconceptions are generated.

As to WormKill being OK because there was nothing better (mid 1980s) this is entirely true. In much the same way, a perfectly functional Rolls Royce amidst a junyard of engine-less wrecks would be OK as well.

So, how good was WormKill in its golden years? Well, according to Newman and others it was an outstanding success as an extension program – perhaps never bested in terms of adoption rate – with over 90% of producers in the target area adopting the program in its first year. (Newman RL (1984) ” Worm control in sheep on the Northern Tablelands of NSW:A survey of Farmers’ Opinions”. Dept of Ag Economics and BusinessManagement, Uni of New England).

From 1982 to 1996, I worked as a field vet then as a vet pathologist. During this time, I had first hand experience of WormKill and it’s predecessors. As to efficacy, this program was an outstanding success, particularly against Haemonchus. In general the only failures were with respect to Ostertagia/Trichostronglyus, and usually because producers had not used effective broad-spectrum drenches, as advised. From 1984 to around 1990, Haemonchus -certainly heavy burdens – became a rarity, and was eradicated on some farms. (Barger, I.A., Hall, E. and Dash, K.M., 1991. Local eradication of Haemonchus contortus using closantel. Aust. Vet. J. 68, pp. 347–348).

Alas, WormKill’s very success was also its weakness, and closantel, a cornerstone of the program, became increasingly ineffective in the Northern Tablelands from around 1990 onwards. With the benefit of hindsight, the first versions of WormKill were overkill in some seasons (drier years) and localities (e.g. Moree, Narrabri).

Of course, we cannot live in or return to the past. But the way to doing better in the future is not served well by creating misconceptions about what has gone before.

We don’t want recipes: we want simple and effective!

I heard this one recently. At first hearing, it sounded good, much like any good slogan.

Alas, worm control is more complicated now because of anthelmintic resistance. And, to date, thorough-going IPM is only used by a small minority of producers.

For an advisor to say they eschew recipes is disingenuous or misguided. Well educated and experienced advisors are well acquainted with the epidemiological principles that are the foundation of current and past worm control methods. Such advisors do not walk onto a client’s farm with a blank mind: they have in mind a template – or ‘recipe’ if you will – albeit a template that can be modified to fit the client’s needs.

20090603162450.pdf

20090604142823-LHPAs and worm zones draft march 09.pdf

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