WORMS: MISDIRECTED HYSTERIA???

By Sue Reith

Reprinted with premission
(This artcile was not written by Molly Nolte/Fias Co Farm)

Most of us reading something from what we consider an authoritative source will assume that it's accurate and based on fact. But occasionally we have to allow for potential human error along the way that can lead to the final product being less accurate than intended.

Case in point: Over the past few years there has been a rising hysteria over a seemingly out-of-control internal parasite, the worm called Haemonchus contortus (aka Barberpole worm), purportedly now resistant to any of the wormers designed to eradicate it. This hysteria has reached the point that (according to an article in the current AASRP Bulletin) classes called FAMACHA (a clinical-on farm system), are being held to teach people how to recognize its presence in their animals by specifically giving field tests for anemia, and advice is apparently being given that once a goat is determined to have shown resistance to treatment for Haemonchus contortus, the answer is to CULL!!! Good grief!

The information I’m sharing here comes from personal experience in combination with much research on my part, with the hope that I can provide a little insight into this rising hysteria and help readers to assess the situation rationally.

Two major factors are apparently being overlooked by those declaring that Haemonchus contortus is now so resistant to available wormers as to be out of control, and that owners treating for it should cull those animals not showing improvement after worming. They are:

(1) Misidentification of eggs in the fecal sample reports that are the basis for determining the levels of Haemonchus contortus in goats, an error being made by technicians who mistakenly identify as the eggs of Haemonchus contortus those actually from other worm species that appear quite similar to it but do not respond to the same wormers it does,

and:

(2) Failure to use proper worming techniques so as to achieve successful eradication of Haemonchus contortus when it is actually present.

 

I'll start with Factor # 1, misidentification of the culprit egg...

I have been fortunate to be able to run my own goats' fecal samples for many years now. I also teach others how to do this. My first introduction to misidentification of another species of egg as that of Haemonchus contortus came in the mid 90's, in a lamb a friend brought to me that appeared anemic and was weakening fast despite having received treatment with ivermectin. The vet's fecal sample report had labeled Haemonchus contortus as the villain. The owner brought a sample for me to double-check, and indeed it was loaded with what at first glance certainly appeared to be Haemonchus. But closer examination told me that something just wasn’t right!

(I will interrupt my story here to explain that I’m fortunate to have a wonderful set of reference photos of specifically goat/sheep parasite eggs from the Veterinary Clinical Parasitology book 5th Ed., 1978, by Sloss and Kemp, to refer to when doing a fecal egg analysis... This book, and the 4 previous editions that preceded it, are sadly no longer in print. The current, 6th Edition, updated by one Ann Sajac, is completely changed and no longer useful as a reference when doing fecal egg analysis, nor is any other book available to my knowledge today. In my view, this lack of clear, specific reference photos could be a big part of the problem of misidentification of the culprit eggs.)

Now, back to my story... I began to analyze the details of the purported Haemonchus contortus eggs to determine what wasn’t right about them... The Haemonchus contortus photo x410 is on Page 46 of the aforementioned book. The Fasciola hepatica (liver fluke) egg x410, found on Page 41, appears almost identical to it... Excepting that on close examination the Fasciola hepatica egg is shaped like a football, with pointy ends, whereas the Haemonchus egg on Page 46 is shaped like the football field, with more rounded ends! Aha! I had the other people in the room check this out to verify that in fact I was correct in my observation of this rather minute detail, and to a person, they agreed. But this careful scrutiny took quite a while… time that a veterinarian, or his/her assistant, on a busy workday, sitting at a lab table with several other samples lined up to analyze, does not have. No wonder Haemonchus was ID’d on the lab report! And most interesting part is that the symptoms of severe infestation with Fasciola hepatica in a young lamb like that, with no functioning immune system yet in place, would indeed be anemia and extreme weakness!

Well, since ivermectin has no effect upon liver fluke we treated lamb immediately with Ivomec Plus, in which ivermectin is combined with clorsulon, a rather recently discovered anthelmintic designed specifically to eliminate Liver fluke. Within a very few days the lamb showed signs of recovery. A short time later we again checked a fecal sample, and what had been previously identified by the vet's office as full of Haemonchus contortus eggs, but we had re-determined to be Fasciola hepatica, was now a clear field!

Not wishing to bore the reader with anecdotes of many similar experiences, I will cite just one more, to give an additional slant on vet reports’ misidentification of what’s seen under the microscope...

This next anecdote is of a friend in Texas that bought, and had shipped to her farm, a 2-month-old Nubian buckling for use in her herd. Shortly after it arrived it began to scour profusely. My friend took a fecal sample to the vet's office for analysis. The report came back that the kid was full of Haemonchus contortus, and the vet advised that it should be wormed with ivermectin. Well, after the worming the kid continued to scour profusely, unabated. My friend sent yet another sample to the vet, who responded once again that there was Haemonchus contortus present, and to worm with ivermectin. This pattern was repeated 2 more times, after which I finally urged my friend to treat for coccidiosis instead, since the kid was young and in my view a better candidate for coccidiosis due to his age and the suppression of his immune system from the stress of having had his environment changed. She treated with Albon for coccidiosis and the scouring stopped. In defense of the vet (in whom she really tried to maintain faith) she later said that 'maybe the ivermectin just took a long time to work'! If the reader looks on Page 52 of the 5th Ed. of Clinical Veterinary Parasitology, an amazing similarity between the Eimeria Ovina x410, a coccidia oocyst, and the Haemonchus contortus egg can be observed... One little variation... The size of the Eimeria Ovina oocyst is ~ 17x13mcg, and the Haemonchus contortus egg size is ~ 70x41mcg! The owner, of course, did not mention the misidentification of the fecal slide’s contents to the attending veterinarian… And that vet may well have reported yet another case of 'resistant' Haemonchus contortus!

In addition to simple misidentification of the parasite eggs by a busy vet or AHT, this problem may well be even more prevalent in many vet labs due to lack of access to a good set of reference photos specifically oriented to goat/sheep internal parasites, largely because of the out-of-print status of Editions 1 thru 5 of Clinical Veterinary Parasitology mentioned above, with (to my knowledge) no other source of quality reference photos available.

While I don’t suggest that all identifications of Haemonchus contortus from fecal analysis are wrong, there’s really no way to know what the percentage of mistaken ID’s might be in the final calculation, thus the report of widespread resistance to treatment for Haemonchus contortus may well contain a significant margin of error.

Now on to Factor #2, Failure to use proper worming techniques to achieve successful eradication of the seemingly-out-of-control Haemonchus contortus worm...

Pick up any container of wormer, and read the label. All of the ones being routinely cited for use in eradication of Haemonchus contortus have something in common, which is that they only wipe out the adult form of the worm! (A wormer or two may claim to be effective against the 4th stage as well, as that stage is just a short time from adulthood, so the wormer is still in the system when it becomes one...)

Doesn’t it stand to reason, particularly in the South where the warmer climate encourages greater numbers of parasites to develop, that after doing a worming that kills off only adults of the species many offspring of that parasite will still be present in egg and larval form? With some exceptions, most internal parasites develop from the newly laid egg to the adult stage, able to lay their own eggs, in about 14 days. For that reason I recommend to the people I guide that they do an initial whole-herd worming at normal doses (not at 2 or 3 x the normal doses!) on day one, and follow that ten days later, when many of those larvae have become adults and many of the eggs have become larvae, with a 2nd whole-herd worming. And ten days after that 2nd worming, the process should be repeated with yet a 3rd whole-herd worming, thus systematically wiping out all the eggs and larvae that were still lurking when the 1st worming was done.

My personal experience in using this approach, which includes successfully treating adult goats that their owners have brought to me because they were clearly at death’s door, tells me that at the end of this 3-stage process, using the Pharmaceutical company’s recommended doses of the correct wormer (as determined by accurate identification of the worm eggs under the microscope) the egg population should have been reduced to such a low level that a microscopic fecal check shows a clear slide, with just a small number of worms remaining. At that point the immune systems of the now-far-less-compromised goats will once more be functional enough to create antibodies to the proteins the worms produce, developing a normal level of resistance to future re-infestation. Careful management from then on, particularly in the area of isolation and 'cleaning up' of new animals before turning them loose with the herd, should keep the worm population of any group of adult goats under control, with due vigilance in the form of periodic fecal analysis and proper maintenance procedures conducted in the future.

Given the similarity of the Haemonchus contortus’ eggs to those of other internal parasites such as Liver fluke and coccidia (and while initially I argued with myself that Liver fluke could not be present unless, according to reference books, the goat in question lived near a swamp, I found that NOT to be the case after all), the potential for occasional error in identifying the eggs of Haemonchus contortus does exist. Understandably, given that many owners find it difficult to accept the possibility that their vets’ reports indicating that Haemonchus contortus is the troublemaker in their herds might be in error, I think that if I were the owner, and Haemonchus contortus had been determined to be the culprit in my herd, I would simply treat, not with plain ivermectin, but instead with Ivomec Plus (or its generic) just to be on the safe side. The results should be highly rewarding, and in that case what does it matter who is right and who is wrong?

And a final word on the subject... To avoid any confusion about who is correct about what, I encourage all goat owners to learn to run their own goats' fecals to check for internal parasites...

 

Sue Reith
Carmelita Toggs
Bainbridge Island WA

(While I urge you to share this information with other individual goat owners, please do not reproduce the article for publication without my specific permission. Thank you. Sue Reith.)

Reprinted with permission. Thank you Sue, for allowing me to reprint your article on this site.