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The Bane of the Southern Shepherd

July 5, 2010

Today is garlic day! Three weeks ago, we checked the ewes and lambs for worms, using the FAMACHA technique. This technique was developed in South Africa by Dr. Francois “FAffa” MAlan, who created the CHArt that bears his name. There are all kinds of parasites that can attack mammals, sheep in particular. Young lambs may be susceptible to tapeworms, liver flukes are a problem in areas that get a lot of rain, and round worms are as common as tornados in Oklahoma. But for all shepherds in the south, the most difficult parasite to combat is the barber pole worm — haemonchus contortus:

It may not look like much, but it's a killer

The FAMACHA technique was developed to combat the barber pole worm, which kills sheep by taking up residence in the fourth (or true) stomach, the abomasum, and ingests so much blood from the host that the sheep dies from acute anemia. Here’s how the life cycle works:

Thanks to Virginia Tech extension for the image

Haemonchus is prevalent all over the world, so why is it even more problematic for those of us raising sheep in the south? Well, if you look at the drawing above, the one thing that may not be clear is that the eggs need a warm environment to hatch. In the southern US, the ideal ‘hatching’ environment is from early April to early October–fully one-half of the year, larvae are capable of reinfesting the sheep over and over and over and over and over. But there’s one more ingredient the larvae need: dew. Humidity. Something we have an abundance of this summer in central Oklahoma.

Right after "how many angels are on the head of a pin?" comes the question, "how many barber pole larvae can occupy a single drop of dew?"

When I was raising sheep in Colorado, I hardly ever had problems with internal parasites, because it was such a dry climate. The larvae need the moisture to crawl up to the end of the blade of grass so they are available to be eaten by the future host. In Oklahoma, sometimes we get a break from the humidity when the temps hit triple-digits in July and it doesn’t rain for three weeks. Doesn’t look like we’re going to get that break this year, does it?So, what’s the southern shepherd to do? One option is to use chemical dewormers. There are only three different types of deworming agents (anthelmintics) available to us in the US: ivomec/cydectin, levamisole, and the “white” wormers — valbazen and fenbendazole. Looking at this list, it seems like a lot, doesn’t it? In actuality, it’s much smaller than what the Europeans and Aussies have to work with. We have severe problems with worm resistance to ivomec and the white wormers. The white wormers have been around the longest, therefore there has been more time for worms to evolve to be resistant to the deworming mechanism. For ivomec/cydectin, worms have developed resistance to them because they have been used so frequently. Levamisole has been around a long time, but the trait for resistance to its efficacy is recessive, so there are still cases where it’s pretty effective. The problem is that levamisole was taken off the market for 18 months and has only recently become available again.OK, so there are problems with using chemical dewormers. One way we’ve kept them working for us is to use them in a very limited number of cases. This is where garlic and FAMACHA come into play. Since we dewormed three weeks ago, the ewes and lambs will just now be dealing with any reinfestation. We used FAMACHA to determine which sheep were showing signs of anemia. Those were the only ones who received dewormer, in this case, levamisole. Now we come back and hit the whole flock with freshly chopped garlic mixed with sweet feed (to get them to eat it, LOL). Garlic has shown some promise as a vermicide in some research trials. On our farm, it certainly appears to create an inhospitable environment for the parasites. As long as we use it periodically, we only need to use chemical dewormer on the most severe cases.The other weapon in our arsenal against this killer is mob grazing. By letting the grass grow longer before we return to regraze it, we make it harder for the larvae to find a new host after hatching. The larvae are capable of crawling only about 4″ off of the ground. By grazing at a height of 8 – 10″, we lessen the chance of reinfestation. When the ewes and lambs are in good health and condition, if they aren’t having to fight reinfestation over and over, they stand a good chance of winning against their southern nemesis, the barber pole worm.

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