Johann Schröder, Project Manager - Animal Health & Welfare, Meat & Livestock Australia
February 2013
 

Internal parasite infestation is the single most important disease faced by red meat producers. Chemicals against parasites make up the bulk of products marketed for livestock by the global pharmaceutical industry.

Meat & Livestock Australia’s investment in on-farm research also reflects the importance of parasites in Australian livestock. In the period from 2003 to 2015, the company will have invested more than $9.5 million in completed and running projects concerning internal parasites alone. With co-investments by R&D partners such as Australian Wool Innovation, the total investment in internal parasite projects managed by MLA in this period amounts to $12.2 million.

What is it about these pests that make us throw so much money at understanding them better? For one thing, they have this annoying ability of developing resistance to every chemical man has thus far invented to control them (there are several articles elsewhere on this website dealing with drench resistance).

We deal with this problem in several ways. On the one hand, we try to invent new chemicals with novel modes of action – “novel” in the sense that they have a mode of action not previously used against worms. MLA’s contribution to this search has cost $4.949 million thus far and has resulted in the discovery of a number of possible drug targets, but no new chemical, as yet.

The drug target search involved an analysis of internal parasites’ genetic make-up (sequencing parts of the genome), looking for genes which code for proteins which are:

• essential for the parasite’s development and survival,
• accessible to chemical interference (i.e. “drugable”) and
• either absent or much less important in the mammalian genome (to ensure safety of the new drug to the host animal).

Another approach to countering drench resistance is to reduce our reliance on chemicals for parasite control. If parasites (eggs or larvae) are left alone on pasture for long enough, they die. This gives rise to various recommendations regarding pasture spelling and rotation. Internal parasites are also fairly host specific, which means that alternating e.g. sheep and cattle on the same paddock can help reduce the parasite load on that pasture.

These efforts at reducing chemical use and integrating it with alternative methods is sometimes referred to as IPM or Integrated Parasite Management. MLA’s investments in this area amount to $1.164 million.

An additional component to an IPM approach is to exploit the host’s immune system. Some sheep carry fewer worms and excrete fewer worm eggs onto pasture than others. This trait is partly heritable and can be selected and bred for.

Research funded by MLA has helped with the development of an estimated breeding value (EBV) for worm egg count (WEC) (Visit www.sheepgenetics.org,au for more information).

Boosting the host’s immunity with a worm vaccine offers another possible non-chemical worm control method. MLA is funding the efficacy work for the registration of the Moredun Barber’s Pole Worm vaccine (described in more detail in another article on this website). Mounting an immune response requires energy. There is evidence that this energy might be expended at the cost of production (live weight gain, wool, and milk). MLA is funding research to try and determine the production cost of selecting for host resistance against parasites. MLA’s total investment in this host immunity area comes to just under $1 million.

Effective parasite control also requires more knowledge about the parasites and their habits:

• when and where do they occur?
• what influences their distribution and survival on pasture?
• how important is their effect on the host? (does it warrant all the efforts to control them?).

Research funded by MLA investigated the importance of internal parasites in prime lambs on irrigated pasture in southern Australia.

An ongoing project is teaching us more about the distribution, prevalence and importance of Sheep Measles (the intramuscular cyst stage of the dog tapeworm, Taenia ovis; also more elsewhere on this website). These investments cost $1.2 million.

It is often important to diagnose sheep worm infections:

• how big is the worm burden (do they need a drench)?
• are they bringing new (resistant?) worms onto my property?
• are the worms resistant to the drench I want to use?

For decades now, worm diagnosis in live animals is mostly done by looking at worm eggs in dung. Doing a WEC provides an estimate of the size of the worm burden (bearing in mind that immature worms which do not yet lay eggs can also cause substantial damage). Following that up with a larval differential culture provides some more information on the actual species make-up of the worm infestation.

This is a laborious and time-consuming process. What if we could extract worm DNA from those eggs which could tell us which worms they come from and how many there are? How much better would it be if we could know the answer within a day or two, instead of waiting a fortnight for the larval diff results to come through?

An MLA-funded project which is underway, will deliver a molecular diagnostic test which will do just that. The company has invested $1.2 million in improved diagnostic methods thus far.

Australia’s rural R&D Corporations are the envy of many primary industries around the world. In addition to red meat, there are livestock RDCs for wool, milk, eggs, pork, and poultry.

Although MLA is a not-for-profit organisation, joint ownership of intellectual property generated in the course of MLA-funded research, means that commercialisation of R&D outputs offer a potential additional source of revenue and, therefore, effectively more bang per producer contributed dollar.