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  • From: Mark <mpludwig@facstaff.wisc.edu>
  • To: permaculture@lists.ibiblio.org, midwestpermaculture@yahoogroups.com
  • Subject: [permaculture] Fwd: [grazersedge] Parasite Control Update - LONG
  • Date: Thu, 24 Oct 2002 12:19:18 -0500

A snaphot of one of the better threads we have had on grazersedge, very good management suggestions late in the post.
Mark

Date: Thu, 24 Oct 2002 11:30:52 -0500
From: Lucky Pittman <Lucky.Pittman@murraystate.edu>
Subject: [grazersedge] Parasite Control Update - LONG
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At 07:03 PM 10/23/2002 -0500, Rick wrote:
>Jim Cropper wrote:
> > Judging by what you said about the study, neither DE or Ivermectin were
> > particularly effective. Therefore, since the two were tied for
> > ineffectiveness, I would still conclude that DE is still worthless.

I concur, wholeheartedly.

>The presentation was made to the American Association of Veterinary Medicine
>annual meeting so you would think this would not have been placed on the
>docket if this was not considered a proper study.

Not necessarily. There's no review, to my knowledge, of materials
presented at such meetings, as there is prior to publication in a
peer-reviewed journal. I've been an invited speaker at the local, state,
and regional veterinary medical meetings, and the program organizer just
contacts me and either requests a presentation on a specific subject or
asks if I have a topic I'd like to speak on. No one reviews my material
for accuracy, etc. It's up to me to uphold the banner of truth and accuracy.
I've searched the proceedings of the 2002 AVMA Convention presentations,
and the only reference to DE in the entire 1300 pages essentially
reiterated what we've already been over - there have been no controlled
studies that indicate that DE has any activity as an effective
anti-parasitic treatment.


>Considering that the egg counts were not lowered by very much, with either
>treatment, is that typically the case when using Ivermectin products? I know
>that egg counts are sometimes misleading when they are low, but if they are
>high and not going down, that seems problematic.

It would suggest to me that they were looking at a herd/flock with a
population of worms resistant to Ivermectin.

Gastrointestinal parasites are, without a doubt, the #1 killer of sheep
and goats in the southern and southeastern US - we have a long warm, moist
growing season which favors prolonged persistence of active larvae on
pasture, and our winters are rarely cold enough to adversely impact
larval/ova numbers in the environment.
As far as I'm aware, fecal egg count reduction is the ONLY accurate method
for determining whether an anthelmintic is effective.
Collect fecal samples for egg counts, deworm, then sample again in 7-10
days; if fecal egg counts are not reduced by 90% or more, it pretty much
indicates that the treatment was ineffective.
Anthelmintic resistance is a MAJOR problem. Unfortunately, we only have 3
classes of anthelmintics to work with, the benzimidazoles(TBZ, Tramisol,
Panacur/Safeguard, Valbazen, etc.), the morantel/pyrantel group, and the
ivermectin types(Ivomec, Dectomax, etc.).
At this point in time, resistance to every one of these, with the exception
of moxidectin, has been documented in small ruminants in the US and
abroad. Since moxidectin is related to and works in a similar fasion to
ivermectin, it's probably just a matter of time before we start seeing some
resistance to it, as well. Resistance usually cuts clear across the entire
class; for instance, if a herd has a population of parasites that are
resistant to Tramisol, they are also resistant to Panacur/Safeguard,
Valbazen, and any other members of the benzimidazole group of dewormers -
and once you get a population of worms that are resistant to that class, it
may be IMPOSSIBLE to ever eliminate them to the point that that class of
dewormers is useful in that flock or on those premises again.
Far too many producers and veterinarians alike don't really understand
proper management and 'rotation' of dewormers for small ruminants -
rotation of dewormers does NOT mean using a different drug every time you
deworm! This is one practice that has probably significantly contributed
to the level of resistance we currently see. A proper rotation scheme
will incorporate doing fecal egg reduction counts(FERC) to determine
when/if an anthelmintic has ceased to be effective, and it's time to switch
to a different CLASS of compounds.

Pasture rotation, co-grazing with cattle/horses, introduction of
nematophagic fungi are all management tools that can be used to help
diminish parasite problems with sheep and goats, but some - particularly
rotation - won't/can't work well for small producers, as you would have to
have exceedingly long (3-6 months or longer, depending on temp & moisture)
pasture/paddock rest periods in order for nematode larval populations to
die out.

Goats and sheep are not small cows. I've rarely, if ever, seen 'worms'
actually kill a cow; impact production, yes, but kill, no. However, I'd
say that well over 85% of the sheep and goats that I've seen over the past
25 years have been victims of parasitism.
It's largely a management problem. Both species evolved in environments
that were not necessarily conducive to heavy parasite burdens. Goats are
principally browsers, consuming mostly leaves, buds, twigs, but once
they're relegated to having to graze(that's where all the feces and
parasite larvae/ovae are!) they rapidly become heavily
parasitized. Similar deal with sheep; they do well in areas where 'it's a
long way between blades of grass', but here in the Southeast, that's
usually not the case, and with heavy stocking rates on small pastures, we
rapidly see infective larval populations reach epidemic levels.
One thing that I tell my students(I teach a parasitology course to
AHT/Pre-Vet students) is that the old-time shepherds really had something
going by bringing the sheep into the 'fold' at night - in addition to being
able to better protect them from predators, it also got them off the
pastures when dew was heavy on the forages - the infective nematode larvae
crawl up the blades of grass in the dew film, and are just waiting there
for that goat/sheep to come along and ingest them. As the sun comes up,
and the dew dries off, those larvae migrate back down to the soil interface
and are less available for ingestion. It's a management tool that's
largely overlooked today. Don't know if those shepherds 'knew' what they
were doing, but it helped, regardless.


Louis L. "Lucky" Pittman, Jr., DVM
Veterinary Pathologist/Asst. Prof.
Murray St. Univ.-Breathitt Veterinary Ctr.
Hopkinsville, KY


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Mark P. Ludwig
Poultry Research Lab
University of Wisconsin -Madison
608-262-1730 WK
608-846-7125 HM





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