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Worming : Worms: Misdirected hysteria~Sue Reith

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Information copied here with permission of Sue Reith Thanks once again Sue

By Sue Reith.

Many of us assume, when we read something in print from what we consider an authoritative source, that it's going to be accurate, and based on fact. Sometimes we need to step back for a moment and consider the innate potential for human error that may have contributed to less-than-accurate conclusions made in what we've just read.

Case in point: Over the last 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 now being given that once a goat is determined to have Haemonchus contortus, the answer is not to treat, but to CULL!!! Good grief!

I'm sharing my own experience here, combined with research I have done, with the hope that I can provide a little insight to help readers allay their fears, and 'get a grip'!

There are two major factors being overlooked by those propounding the concept that Haemonchus contortus is now so resistant to available wormers as to be out of control, and that owners running into it should cull those animals afflicted with it. They are:

(1) Misidentification of eggs (by confusing the eggs with those of other worm species that are quite similar in appearance to Haemonchus contortus, but do not respond to the same wormers) in the fecal sample reports that are the basis for determination of Haemonchus contortus in goats,


(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 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 that appeared anemic and was weakening fast despite having received treatment with ivermectin. Haemonchus contortus was the villain that had been determined in the vet's report on the fecal sample. The owner brought a sample over to me to double-check. It was loaded with what surely appeared to be Haemonchus. But when I looked at it, a red flag popped up in my mind!

(I will take a moment here to explain that I have a wonderful set of reference photos of specifically goat/sheep parasite eggs, found in the Veterinary Clinical Parasitology book 5th Ed., 1978, by Sloss and Kemp, that I refer to when doing a fecal egg analysis... This book, and the 4 previous editions that preceded it, are 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... While viewing what the vet's office had reported to be Haemonchus contortus eggs, and there were many in the field of vision, something said "NO!" to me! I started studying the details of the eggs carefully... The Haemonchus contortus photo x410 is on Page 46 of the aforementioned book. The Fasciola hepatica (liver fluke) egg x410, found on Page 41, is almost identical in appearance... Excepting that on close examination the Fasciola hepatica 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. This careful scrutiny took quite a while! It took time that a veterinarian, or his/her assistant, on a busy workday, sitting at a lab table with 20 other samples lined up to analyze, does not have. No wonder Haemonchus was the determination on the lab report! And most interesting of all was 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 had started to recover. 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!

Without beleaguering the reader with the numerous additional anecdotes I could share of similar experiences, I will cite one more, to give yet another slant on vet office misidentification of the contents of the microscope slide on the report to the owner...

This next anecdote is about a friend in Texas that bought a new 2 month old Nubian buckling for her herd, and had it shipped to her farm. 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 he 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 continued for a couple of additional times, and I finally urged my friend, since the kid was so young, to treat for coccidiosis instead, as in my view that would be a more logical culprit due to his age and the suppression of his immune system with the change of environment he had undergone. She treated with Albon for coccidiosis and the scouring stopped. She later said, in defense of the vet (in whom she really tried to maintain faith), that 'maybe the ivermectin just took a long time to work'! And that vet no doubt reported yet another case of 'resistant' Haemonchus contortus! 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 noted... One little variation... The size of the Eimeria Ovina oocyst is ~ 17x13mcg, and the Haemonchus contortus egg size is ~ 70x41mcg! Is there a pattern developing here?

While I do not suggest that all identifications of Haemonchus contortus during fecal analysis are erroneous, it does seem logical that an undetermined percentage may be, and that they may well wind up as part of the report on resistant populations of Haemonchus contortus!

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

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 able to do in the 4th stage as well, 4th stage being just a short time away from adulthood, so the wormer is still in the system when it becomes one...)

Does it not stand to reason that, particularly in the southern areas where the warmer climate seems to allow greater numbers of the parasite to develop, when the worming that kills off only the adults of the species has been completed, there still may be many, many offspring of that parasite, in egg and larval form, left alive? With some exceptions, most internal parasites develop from the laying of the egg to the adult, able to lay its own eggs, in about a 14-day period. It has been, therefore, my own recommendation to the people I help that they do an initial whole-herd worming (at normal doses, not at 2 or 3 x the normal doses!) on day one, and then ten days later, when many of the left-alive larvae have become adults and many of the left-alive eggs have become larvae, to do a 2nd whole-herd worming. And yet again, ten days after that second worming, repeat the process with yet a 3rd whole-herd worming, to wipe out the eggs that became larvae by the 2nd worming and are now adults! My personal experience tells me that at the end of this 3-stage process, with normal, manufacturer-recommended doses of the correct wormer (as determined by accurate identification of the worm eggs under the microscope) the egg population should be at an extremely low level, to the degree that the microscope slide may well appear clear! There should, however, be just enough worms remaining in the system so that the immune system can create antibodies to the proteins those remaining few produce, allowing immunity to develop in the now-less-compromised herd members. Careful management from then on, particularly in the area of 'cleaning up' new animals in isolation before turning them loose with the herd, should keep the worm population of any group of adult goats under control after that, with due vigilance in the form of periodic fecal analysis and proper maintenance procedures conducted from then on.

Given the potential for occasional error in identification of the eggs of Haemonchus contortus, and its eggs' similarity to such other parasites as Liver fluke and coccidia (and while initially I argued with myself that the presence of Liver fluke would be impossible unless, according to reference books, the animal lived near a swamp, I found that NOT to be the case after all), those facts, coupled with the reticence of many owners to accept even the possibility of error in reports their vets give them that indicate Haemonchus contortus is the troublemaker in their herds, I think that if I were an owner in such a situation, and Haemonchus contortus had been determined to be the culprit in my herd, I would treat, not with plain ivermectin, but instead with Ivomec Plus (or its generic if there is one) 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... This is a very important reason why I encourage all goat owners to learn to run their own goats' fecals to check for internal parasites...

(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.)

Sue Reith
Carmelita Toggs
Bainbridge Island WA
[email protected] <mailto:[email protected]>
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