Considering Camelids?

Here’s what you need to know about Meningeal Worm

By Kristi Murdock, RVT

If you own or are considering ownership of alpacas and/or llamas – “camelids” – in our area, you need to know about Meningeal Worm.  A lot of new owners don’t know about this disease, and there is a lot of misinformation about it, especially on the internet.  I’ve pulled this information together from research I’ve done to try to ensure the safety of my own herd, in hopes that it will be useful to others.

What did you call it, again?

“Meningeal worm,” “Brain Worm,” “Deer Worm.”  These are all names for a parasite that is common in White Tail Deer, and you know that White Tail Deer are all too common around here!  The scientific name for the parasite is paraelaphostrongylus tenuis, usually abbreviated as p. tenuis for obvious reasons!   

How does it spread?

White Tail Deer carry this parasite without problems, very much as most farmyard animals have at least some worms some of the time.  When infected deer eliminate, the infection is present in their poop pile.  Certain types of snails or slugs crawl over the poop, since part of their job is to start breaking the stuff down into compost.  They “pick up” the infection.  Inside the body of the snail or slug, the infection “matures” into another stage, and this second stage infection is then shed in the slime trail of the snail or slug.  Any animal grazing on the slime trail can then “catch” this infection (they don’t have to actually eat an infected snail or slug).   In deer, the infectious organism matures into larval form and then heads out of the stomach and up into the spinal fluid, then on to the brain.  The worms then live quite happily on the surface of the brain.  The worms lay eggs, which then travel through the bloodstream into the lungs, where they are coughed up and swallowed, and then deposited in that poop pile. 

Can my kids get it?  How about my dog?  my horse?

P. tenuis has only been identified in even-toed herbivores – “ungulates”: sheep, goats, llamas, alpacas, camels, moose, caribou, reindeer, wapiti, fallow deer and mule deer.  Interestingly, while sheep and goats are obviously grazing amongst the same pastures from which llamas and alpacas contract the disease, they seem to be must more resistant  to the parasite, at least in most parts of the country.  Most sheep and goat producers are only marginally aware that it exists.   In other words, until you start keeping exotic livestock, i.e. pretty much anything other than cows, horses, sheep, goats and pigs, you probably won’t hear much about p. tenuis.

So what’s the big deal?

For deer, the parasite is incidental -- it doesn’t matter.  This is because the deer is the definitive host for this parasite, the one the parasite evolved to co-exist with (only a really stupid parasite kills off its host!).  It doesn’t hurt the snail or slug – they are a secondary host and only serve as an incubator for the parasite.  But for most other ungulates (split-hoofed animals like moose, antelope, llamas, alpacas and even sheep and goats) it can be bad news.  They are considered to be a dead-end host, and you know from the name that isn’t going to end happily.  We don’t know why, but in these species, the parasite migrates into the nervous system tissue – into the spinal cord and the brain, itself.  Everywhere the parasite tunnels, it leaves a path of destruction through this vital tissue.

 That sounds awful.  What happens?

Alpacas and llamas infected with meningeal worm have widely varying symptoms, depending on what part of the nervous system has been affected by the worm.  The most commonly scene symptom is ataxia (clumsiness, lack of coordination).  This will often be seen in the hind legs first, since they are controlled by the area of spinal cord closest to the stomach.  However, this symptom may not be present.  At the University of Wisconsin School of Veterinary Medicine, the doctors told us that 80% of camelids they see with any neurological symptoms at all have been found to have meningeal worm.   In one animal, we saw no signs of coordination problems, only what seemed to be respiratory symptoms – green mucous from the nose, a cough and lethargy.  It turned out meningeal worm had attacked the portion of the nervous system that controlled the esophagus, and so the llamas had difficulty swallowing as well as with bringing up and chewing his cud.  Food got into his sinuses and his lungs, causing pneumonia.  The ataxia did not develop enough to be seen until the other symptoms were a week old.  The animal was euthanized.

There is no test that definitively diagnoses meningeal worm in a living animal.  It is completely undetectable before it gets into nervous tissue. After that, you might get incredibly lucky and pick up a larva during a spinal tap, but that is extremely rare.  Thus, the disease is usually diagnosed based on neurological symptoms, as well as on the presence of white blood cells in spinal fluid (requiring a spinal tap, of course), a sign that the body has detected an invader and is trying to fight it off.  Sadly, the llama’s immune system is no match for the marauding worm.  Meningeal worm can be diagnosed upon necropsy by examining the neural tissue. L

Can it be cured?

By the time we see symptoms in a llama or alpaca, damage has already been done.  Even if all the worms are killed off at this point, that damage may well be irreversible.  Thus, treatment must be begun immediately when meningeal worm is even suspected .  Treatment involves giving dewormers to kill the worms and anti-inflammatories to try to control swelling around the damaged neural tissue.  The treatment protocol may also include the kinds of drugs you would get if you were gravely ill – medicine to protect the stomach from acid when you don’t feel like eating, medicine to relieve pain and anxiety, medicine to control any potential secondary infections (like the pneumonia in the llama we talked about earlier).    I’m not a Veterinarian so I can’t tell you how to treat your animal, and advances are being made in treatment protocols all the time.  If you suspect meningeal worm, my recommendation would be to have your Veterinarian call the large animal department at a Veterinary teaching hospital – U. Wisconsin or U. Minnesota (Iowa State will not treat alpacas or llamas) and ask them for their most current recommendations.  Even if you decide to take your camelid to an expert for treatment, the protocol should be started as soon as possible – even a 3-4 hour drive can make a difference!

Then can we prevent it?

Technically, if you prevent a disease, you vaccinate against it.  So that’s what we’d really like to see – a vaccination against meningeal worm.  Although promising research has been done, the sad economic truth is that even if a vaccine could be created, no drug company would want to spend the money required to manufacture and sell it, because the population of potential patients – and the associated revenue – is so low.   In other words, do not expect a vaccine to be developed.  Ever. 

What we do have is like a preventative – the idea is to kill the larva before they get to the nervous system.  The only scientifically proven protocol is from a challenge test done by Dr. Julie Jarvinen at Iowa State (she works there; if she wants to have her alpacas treated, she has to go to U. Minnesota, though!)  Dr. Jarvinen deliberately infected alpacas with meningeal worm and found that by injecting Ivermectin sub-cutaneously at a rate of 60 ml. per 100 pounds every 30 days, she could prevent symptoms of the disease.  Her study has not yet been published so most people are unaware of it.  However, Dr. Steven Purdy, a camelid specialist at U. Mass, confirms that the dose they use on their herd is comparable – 100 ml per 100 pounds every 30 days of subcutaneous Ivermectin – and, although they know the slugs and snails in their pastures carry the disease because they take those little guys in and look at them under a powerful microscope, their herds remain unaffected.  Thus, both anecdotally and scientifically, this protocol is proven. 

One caution – there are a lot of “myths” available on the internet, some of them authored by distinguished camelid specialists,  that talk about preventative methods.  If you read them carefully, they talk about hypothetical results from using estimated dosages of medicines.  In particular, many Veterinarians will recommend using Dectomax ™, which is Doramectin, an extended-release dewormer.   They will say that Doramectin at 1 cc per 110 pounds will “last” 6 weeks as a p. tenuis preventative in camelids.  This has been shown repeatedly to be untrue.  The length of action of Doramectin in all species has been found to vary unpredictably.  Further, no one has ever proven that Doramectin reliably works against meningeal worm at all (it seems likely, but we don’t know for sure and we don’t know how long it does, if it does).    Other things that have been proven not to work include pour-on dewormers, oral dewormers, herbal/naturopathic remedies, and, of course, doing nothing.

I know people who have camelids.  They never give these dewormer shots and their animals are fine. 

It’s so unfair, isn’t it?  Here’s the thing – you have to have infected deer; you have to have the right kind of snails and slugs (which ones?  No one knows, exactly!);  the snails and/or slugs have to be hiking around your pastures and not hibernating somewhere (when do they do that?  We aren’t sure!) you have to have conditions where the slime trail remains friendly to the parasites (how cold or hot or dry does it have to be to kill the infection in the slime trail – no one knows!) 

And then you’ve got sheep and goats, who don’t get the disease just because they are exposed to it.  It may be that SOME llamas or alpacas also develop what seems to be a sort of immunity.  Maybe.  Might happen.  Which ones?  When?  We don’t know!

My neighbors give the dose you described as you describe and their animals still got sick.  Are you sure it works?

Right now, it’s the best thing we’ve got.   One problem is that it is surprisingly easy to mess up on the injection.  Perhaps you don’t have a scale and have estimated weight incorrectly (or your scale is wrong, or the animal was leaning against the wall).  Assuming you draw up the correct dose, it’s easy to punch “through and through” the camelid’s thick skin and dense hair when you tent the skin for a subcutaneous injection, pushing some or all the dewormer out the other side of the skin fold.  Alternatively, you may get the needle into muscle rather than under the skin and the injection will be metabolized faster and won’t protect for as long.  If you have a big animal and are injecting 4-7 ml or more, the subcutaneous space may not be big enough and some or most of the fluid may leak back out (many folks split these big doses into smaller ones at several locations.  I know, owie.  Be sure to apply pressure and massage the spot after the shot, too, to help absorption). 

Experts also recommend things like putting gravel around the outside of your pasture fence to try to discourage snails and slugs from coming in (but you know some are already there!).  Some places use the usual slug and snail deterrents like salt (the llamas and alpacas love that one!) or beer (some llamas and alpacas love that one).   Use deer-proof fence (assuming you can afford it!).

A couple of other notes

There aren’t a lot of large animal Vets around any more, relatively speaking.  Not all large animal Vets will treat camelids.  Before you get too serious about owning camelids, you need to locate the Vet you will use and make sure he or she will treat your animals.  Once you do that, I strongly recommend that you provide all the support you can to your Vet in terms of making him/her aware of educational opportunities and technical books on the subject, perhaps even helping to fund some of those things.  Vets are wonderful, but you have a responsibility to be an advocate for your animal’s health, and that is more important than ever with an exotic pet like a camelid.  The work doesn’t end in the barn! J

Some states do not have meningeal worm.  We don’t know why, but are guessing that the snails and slugs are the “wrong” kind (whatever that is) or the climate is unfavorable or…?  It is unknown whether the parasite may spread to them in the future.  Iowa is definitely NOT one of those states.

There is a very justified concern that dosing camelids every month with a relatively high amount of dewormer may contribute to the creation of dewormer-resistant parasites.  Some doctors would like us to not give so much dewormer so frequently (very similar to the way that they no longer give out antibiotics for just anything, afraid that by doing so they are creating bacteria that are resistant to the antibiotics we have).  Here’s the thing – if we don’t do it, the camelids die.  Some doctors argue that p. tenuis is treatable so it’s a “fair” risk, but it is not really treatable – you may just be able to prevent the animal from dying and possibly even from having too much damage to live successfully… but you can’t “fix” the nerve damage that has been done.    Anyone who has seen a beloved pet suffer from p. tenuis will never accept this argument.   Thus, some folks compromise, trying to give the dewormer “when the slugs/snails” are active,” i.e. not when it’s too cold or too hot or too dry…  the problem is, we don’t even know exactly which snails and slugs are the problem, let alone exactly when they are on the move.  Also, when is it hot or cold or dry or wet enough to kill the infectious stuff in the slime trail?  Again, we don’t know. 

So, now you know what I know.  While it’s definitely not what you’d call good news, at least we know what we have to do to protect our animals.  I’m sure not going to tell you what you should do – I change my mind about how best to care for my own herd on a regular basis.  But knowledge is power, and we should all be the heroes our animals think we are (at feeding time, anyway)!

Kristi Murdock lives near Cedar Rapids with her family, which has included a small herd of extremely spoiled llamas since 2001.  In 2003, concerned about how much she didn’t know about her charges, Murdock enrolled in the local community college, and she passed her Board exams to become a Registered Veterinary Technician in the state of Iowa two years later.  Murdock isn’t a Vet nor does she even play one on TV, and the information in this document is intended only to supplement the care provided by your large animal Veterinarian.  Murdock presently teaches part-time in the Animal Health Department at Kirkwood Community College, and provides The Camelid Experience, a lecture and wet lab for the Veterinary Technician students each spring.  She has been known to dye the white llamas with pink Kool-Aid to spice up the occasional parade entry. 

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