Refugia - Secret Weapon Against Drug Resistant Worms
"Refugia" Definition by University of Namibia in South Africa The word "refugia"
is used to denote parasitic populations that have not been exposed to a particular
drug and hence still contains a large proportion of susceptible organisms.
"Refugia" is a word that is rarely heard or mentioned in the goat industry. I ran
across it in a research paper while I was trying to better understand the worm problem
and all of the recommendations for "pasture rotation" that I kept seeing. No one
was describing exactly how to do the pasture rotation, especially when a breeder
only has a small amount of acreage. I was totally surprised when I started reading
about refugia and worm immunity in goats. This article will only discuss the refugia
I believe that there is a vast amount of bad information being given word of mouth
and through goat chat groups about worming and I have never read any of the chat
group experts discuss or recommend breeders need to understand refugia. Below are
some examples of worming recommendations coming from goat chat groups with a heavy
emphasis on "worming the heck out of the goats and moving to a clean pasture". NOTE
- there is no such thing as a "worm free" goat after worming.
"I worm them 3 weeks prior to kidding when I booster vaccinations, I also worm the
heck out of them when I am doing vaccinations. For me it is more practical to do
all of them ahead of time."
"Horn peeling can occur in response to stress from worms or nutrition or both. I
would worm the heck out of them and get them on good feed and pasture until they
"usually you worm after a 4" rain"
Now, what does refugia mean to you and how does it work.
Before we discuss refugia related to parasites and pastures, it is good to have a
basic understanding of how "biological warfare germs" are created. A scientist starts
out with some germ being selected. In our example, we will take the flu germ. The
scientist will take whatever the strongest antibiotic against the flu, significantly
dilute it down and then put the diluted medicine in with the flu germ. This will
kill most of the flu germ but a small sample will survive. The scientist allows the
germ to grow and then more antibiotic is placed with it but less diluted. Again,
most of the germ dies. The surviving germs are allowed to grow and other rounds of
antibiotics are added with less and less dilution until the antibiotic is added full
strength. It soon results in the antibiotic having no affect on the flu germ and
the germ is now a serious problem because there is no known medicine for the drug
Worm larvae in a pasture can follow the same result. Initially, the worms were not
resistant to any drugs. As more and more of the first drugs were used, the worms
became resistant to that drug and the breeders started using the next drug. Again,
the worm becomes resistant to the next drug and breeders continue to move to another
drug until there are no more new drugs to use. At that time, breeders were recommended
to rotate to "clean" pastures. Breeders were told to "worm the heck" out of the goats,
hold them in the barn area for 24-48 hours and then rotate them to a "clean" pasture.
Here is the problem. Worms only breed in the goat's rumen. If you "worm the heck"
out of all of your goats and then put them in a "clean" pasture, the only worms the
goats will pick up as they graze, are the worse ones. The ones that the best de-wormers
in the industry could not kill. What is even worse is, there can be 4-5 generation
of worms in a single year.
Lets take an example of assigning a number to indicate how drug resistant the worms
are. 0 = no drug resistance and 4 = the strongest worm resistance. We have already
discussed the "0" resistant worms and how continual worming has now created the "4"
resistant worm. Now if you worm with multiple de-wormers, increased strength or wormed
over several days, you have killed much of the "4" resistant worms and now you are
rotating the animals to a clean pasture where only "4.5" resistant worms will be
and that is generation 1. Generation 2 will create "5" resistant worms. Generation
3 will create "5.5" resistant worms. Generation 4 will create "6" resistant worms.
This all occurred in just one year.
With "refugia", you try to maintain as many low resistant worms in your animals and
pastures as possible. This is done by ONLY DE-WORMING when it is absolutely necessary
and culling the goats that have the biggest problem with worms. 20% of your goats,
produce 80% of the worm problem. Now, when the animals go to the "unclean" pasture,
there will be more of the low resistant worms and the goats are adding fewer of the
most resistant worms. This means the goats are much more likely to pick up low resistant
worms than the most resistant worms. When the "0" resistant worm breeds with the
"4" resistant worm, the result will be "2" resistant worm eggs. You have reduced
the resistance in the worms on your farm. Plus, the research states that the less
resistant worms are more likes to attach to the goats rumen while the most resistant
worms just coming from the drenching will still be weak from the treatment.
The other concept that goes along with this as stated in one of the research articles
is related to worm immunity in goats. It states that goats have to have some worms
in their system to maintain their immunity. Without any worms, the goats system will
lose its immunity. Think about what you are doing when you vaccinate annually with
your CD/T vaccines. If it is not done annually, to keep it in the goats system, the
immunity goes away.
We totally believe in this concept of "refugia". Our total management program is
now based around
Worming only as the last resort
Culling the goats with the most worm problems
Selecting goats with high worm resistance or immunities