JANUARY 26, 2013

Greetings folks,

This week I’d like to address the issue of internal parasites and their effect on our small ruminant patients. This particular aspect of owning goats, sheep, llamas, alpacas, etc requires extensive attention to detail and thorough explanation of parasite life cycle, multi-drug parasite resistance, integral diagnostics, and important farm management strategies to name a few (*entire books are dedicated to this issue alone); thus, for the sake of reader-attention span, I will briefly touch on several of these aspects which are vital to a small ruminant deworming protocol.

  • Infection with the main nematodes of interest can be described as the HOTC complex (please excuse potential spelling errors!)  H=Haemonchus contortus  O=Ostertagia sp  T=Trichostrongylus sp  & C=Cooperia sp
  • Haemonchus contortus AKA “The Barber Pole Worm” is the main offender of all the previously named species.  This worm wreaks havoc on the inner lining of the abomasum (last compartment of the stomach) by attaching itself and subsequently feeding on the animal’s blood.  Clinical signs of infestation include but are not limited to weight loss, decreased appetite, poor hair coat, +/- diarrhea, and signs of anemia which include pale gums, brisket edema, and submandibular edema AKA “bottle jaw”.  Goats tend to develop bottle jaw more often than sheep and poor fiber quality is a common sign in llamas/alpacas.  Depending on the level of parasitism, Haemonchus worms can kill animals over the course of several weeks to as little as 48 hrs.
  • The other worms associated with the HOTC complex are not known to be blood-feeders, however these nematodes can still cause severe intestinal inflammation and depress the animal’s immune system drastically.  In most instances, parasitized animals aren’t infected with just one species, but most likely infested with several species of nematodes in the HOTC complex.  All of these worms are known to slip into a stage of their life cycle known as “hypobiosis” or arrested development where the larval stage of the worm ceases development during the cold winter months and resumes development when temperatures rise during the spring.  Unfortunately, we live in Tennessee where even in January, temperatures can reach 70 degrees Fahrenheit as we experienced merely 2 ½ wks ago.  When environmental temperatures are not consistently below freezing, these larvae continue to develop and the eggs rapidly disseminate especially during wet weather (which we’ve had PLENTY of here in Mid-TN).  Therefore, the key point here is:  Be cognizant of your animal’s health concerning parasites all year long.
  • I tell all of my small ruminant clients about FAMACHA.  Do a quick Google Image search of FAMACH and you’ll find countless color diagrams of how to subjectively grade anemia status.  Basically you pull down the lower eyelid of each animal and observe the color of the inner eyelid tissue.  Grade I-V is allocated to each animal and this grade coincides with the level of anemia that may or may not be present.  This test is only useful for determining infestation with The Barber Pole Worm.
  • All animals should be dewormed according to a fecal egg count, or the # of worm eggs in a single stool sample.  Fecal egg counts allow us  to determine which animals in your herd are shedding the majority of the parasites.  In the horse world, 20% of horses shed 80% of the worm eggs.  In small ruminants, 30% of the animals are responsible for shedding the majority of the worms and infesting pastures.  It is for this reason that total herd deworming, as is performed in cattle, is not effective.  We must strive to “Target Deworm”.  This involves utilizing the FAMACH method and deworming individual animals according to fecal egg counts.
  • The million dollar question continues to be “Well Doc, I’ve tried dang near every dewormer I can get my hands on and I’m still losing a few animals every year to worms.  What the heck can I use to successfully deworm my herd?”  Again, scenarios such as this need to start with a stool sample first and foremost.  Also, we must never continuously use the same wormer just because “it’s been working so far.”  Rotation of wormers prevents the nematodes from genetically developing anthelminthic resistance.  I  push for what’s called a healthy refugia, or the population of parasites on your farm that are susceptible to common dewormers.  Without a healthy refugia, you may have resistant parasites that reproduce with other resistant worms which in the end creates a crazy treacherous mutant super worm that laughs and shrugs its shoulders at every dewormer we throw at it.  That being said, there are combo dewormers that I use and specially formulated dosing schemes that can also be used to eradicate these nasty resistant alien worms, however no guarantee can be made.
  • Finally, I must mention that just because your animals may quickly become poor, weak, dehydrated, etc doesn’t mean the HOTC worms are to blame right off the bat.  A single cell organism known as Coccidia can also be a nightmare in our small ruminant patients.  Under normal circumstances it’s the young, old, and debilitated (pregnant females, lactating females, stressed animals) that succumb to coccidiosis.  Stool samples are paramount in diagnosing this nasty critter as well.  This bug can be prevented fairly easily by the addition of medication to drinking water and treated rather successfully with a short term coccidiostat therapy if the animal is not severely and chronically infected.

**Llamas and Alpaca owners must also be aware of the Meningial Worm which is carried by the white tail deer.  This particular parasite has not shown great drug resistance and can usually be prevented with Ivermectin-based products used regularly.

Stay warm and dry,

Dr. Steve Shirley

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