Got worms?
Parasites: Friends We Can Do Without
Even with warm weather waning, veterinary staff are on the
lookout for “wormy friends” hanging around the neighborhood. Roundworms,
heartworms, whipworms, hookworms… and then there are other parasites that
aren’t worms at all, but protozoa. Some parasites only affect our pets, but
several species are also quite happy to take up residence in humans if they
can. Especially with small children, it’s easy to imagine how this might happen
(child sees shiny object on ground, child puts object in mouth, worm eggs on
object are swallowed: voila!).
How common are these “friends?” It varies by region within
the US, by parasite, and by pet. In some situations, 1 in 4 (!!) pets will be
infected, in others only 1 in 21, or even fewer. If you’re curious for
specifics, check this out: http://www.petsandparasites.org/parasite-prevalence-maps/
Veterinarians have excellent treatments for parasites. We
also have excellent prevention for some, but not all parasites. For example,
there is excellent heartworm preventative available, and some medications also
cover hookworms and roundworms. However, there are not current preventatives for whipworms or protozoa, though there are effective treatments for them.
So, how do we know that our companion has parasites overstaying
their welcome?
A common idea is that you can see worms if the animal has
them. Unfortunately, adult worms prefer to live safe and warm deep inside of
animals, where we can’t see them. (Gross, right?) With intestinal worms, it is
the offspring in egg or larva form that go out by way of the fecal express.
With tapeworms, a sharp eye can see the eggs – they look like small
cream-colored grains of rice. http://avetsguidetolife.blogspot.com/2010/09/tapeworm-blues.html
With most others, though, the eggs are microscopic. And in the case of
heartworms, owners can have no way of knowing their animal is infected until
they become clinically ill – at which point their pet’s life may already be in
danger.
This leads us to testing: fecal tests for intestinal
parasites and blood tests for heartworms. Sometimes, we find that we are
testing without finding anything. Why might that happen? There are a few possibilities:
(1) Your pet doesn’t have worms. Hooray!
(2) In the beginning of an infection, the parasite may be to
“young” to have shed any eggs. A test in those early days may be an incomplete
negative.
(3) Many worms shed eggs intermittently, sometimes even
months passing between shedding events. A test in between shedding events may
show no eggs.
(4) The test may not be detecting the eggs. While only small
bit is needed for a fecal test, a too small sample can hinder effective
testing. Further, some parasites (like whipworm!) tend to show up poorly in
tests.
The good news is these issues can be addressed by
communicating clearly with your veterinarian and periodically double-checking.
If you pet is healthy, annual testing may be sufficient. However, if your pet
is ill, or has been diagnosed with parasites, more frequent testing will be
necessary. Typically two negatives in a row are considered enough, but remember
that other factors (such as the health of your other pets)
should also be considered.
In general, it’s important to keep an eye on our pets eating
and drinking, stools, and any weight changes. It’s also important to test
periodically, just in case your pet is hiding the signs. By doing those things,
we can help our veterinarian say “here’s your hat, where’s your hurry?” to our
wormy friends.
Jeanne Coffin
Masters of Conservation Medicine
Tufts University
Asheville, NC
Masters of Conservation Medicine
Tufts University
Asheville, NC
