MENINGEAL DEERWORM INFECTION IN GOATS
Goat producers who live in areas of high rainfall, whose land holds water, and where whitetail deer are abundant should be concerned about Meningeal Worm infection in their goats.
Sometimes called deerworm or brainworm, the parasite Parelaphostrongulus tenuis uses the whitetail deer as its host and passes through the deer's body without harming it. But with goats, the deerworm seems to "get lost" and winds up in the spinal canal . . . causing hind leg weakness and unsteadiness, progressing to hind leg dragging, inability to walk in a straight line, head wobbling from side to side, tremors, and finally inability to stand. Once the larvae migrate over the body, the goat oftentimes (but not always) experiences intense itching and may begin chewing holes in its hide. Shaving the hair off the sites where itching and chewing are occurring will usually reveal a straight line of hard nodules over which the skin has thickened leading from the spine. These are the subcutaneous larvae migrating throughout the goat's body. Pregnant does may abort from either the stress of the disease or the treatment given.
Goats who develop Meningeal Worm infection get it by ingesting the intermediate host, a slug or snail, while browsing in wet areas such as ponds or swamps or under dead leaves, branches, and trees. Warm weather in early winter and the resulting lack of snow cover has made this disease common in the eastern part of the United States. Goat producers who also raise alpacas, llamas, or related ruminants will find that these camelids are even more susceptible to Meningeal Worm infection than goats or sheep.
You should suspect Meningeal Worm disease if the goat displays bare patches of hide from quarter to palm size (generally on the flank or near the front leg), a bloody hole chewed in the hide, neurologic signs or any problem involving the spinal cord, from hind leg dragging to inability to get up. The disease can be a slow progression of symptoms or can strike suddenly. Neurological damage expresses itself with a wobbly hind end while the head is fine and the goat has a good appetite. Pneumonia is a common secondary problem, given that the goat is down and therefore inactive. The only good part of this disease is that most animals do not seem to be in pain (other than the itching); most eat and drink well until they die.
The curative treatment (treatment for infected goats displaying symptoms) has changed in 2013. Very high dosages of fenbenzadole (Safeguard/Panacur or equivalent) at a dosing rate of ten times the label dosage. Liquid Safeguard's label dose is 2.3 cc (ml) per 100 pounds bodyweight, which means that you must multiply this by 10 and dose at 23 cc (ml) per 100 pounds bodyweight. You can use Safeguard paste, also dosing at ten times the label's dosage rate based upon the goat's body weight. Treatment is given once a day for five consecutive days. Ivermectin was eliminated from the curative treatment protocol because researchers at Ohio State University found that it didn't penetrate the spinal column to kill the worms, so once neurological symptoms appeared, using Ivermectin was ineffective. If the goat is down and can't get up on its own, the chance for recovery is not good. An anti-inflammatory drug like Banamine can be useful in alleviating the inflammation of nerve tissue. Dexamethasone may also be used, but it will cause abortions in pregnant does.
This treatment, if utilized early in the disease, can stop its progression but cannot undo any nerve damage. Permanent spinal damage (including curvature), hindquarter weakness, and/or inability to deliver kids may be the residual effect of Meningeal Worm infection. Once the spinal cord is damaged, treatment can only do so much and the goat will never be back to full health. You should let at least one month pass after treatment is completed before deciding to euthanize the goat or being convinced that it has been successfully treated.
The preventative treatment for goats showing no symptoms whatsoever involves a one-time oral dosing of 1% injectable ivermectin given orally dosing at 1 cc per 55 pounds of bodyweight, OR a one time oral dosing of Safeguard/Panacur dosing at 2.3 cc per 100 pounds of bodyweight (either suspension or paste). Ivermectin paste and Ivermectin pour-on are not effective. Using Ivermectin preventatively (prophylactically) or to treat pre-neurological symptoms is effective.
If you need to treat preventatively and also want to avoid adding to worm resistance, why not do a check for fenbendazole (Safeguard/Panacur) efficacy/effectiveness? Collect fecal material from several of your goats, do fecal counts, then dose them with fenbendazole to see if there is a reduction in fecal egg counts. If there is a reduction in fecal egg counts, then fenbendazole works in your area and you should be careful about losing a "new tool" against worms. If there is no FEC reduction, then fenbendazole does not kill stomach worms in your area and you have nothing to lose by treating them monthly with it to prevent Meningeal Deerworm infection.
In the northern and eastern parts of the United States, most infections occur in late summer/early fall or early winter, following a wet summer and mild fall. The larval migration of P. tenuis can take from ten days to over three months, so some producers are using 1% injectable Ivomec preventatively on a monthly basis for up to four months during the at-risk seasons. If the expense of this preventative treatment is too high, then you should treat your goats preventatively at least one time during Meningeal Deerworm season and again if any symptoms occur in any goat. Keep in mind that frequent use of dewormers can result in worms developing resistance to the dewormer's ability to control the blood-sucking stomach worm Haemonchus Contortus, so you must constantly do FAMACHA field checks and fecal counts to keep this barberpole worm also under control.
Although laboratory testing of the cerebrospinal fluid produces an accurate diagnosis, the key to treatment of Meningeal Worm infection is early aggressive treatment. If all indications are that the goat is infected with P. tenuis, forget testing immediately start treatment.
Prevention is difficult. The only proven preventative medication is oral dosing of 1% injectable Ivomec in combination with Safeguard/Panacur given orally once a month during slug and snail season. Fence off ponds and swamps so goats cannot become exposed to slugs and snails. Treatment can be unsuccessful, even when the disease is caught in its early stages. Prevention is the key to avoiding this devastating disease. Remember that goats are a dry-land species, and other than needing to drink clean uncontaminated water, moisture is the goat's enemy.
My thanks go to Ray Kruse in Kentucky for the vital information and experience that he provided in putting this article together.
Suzanne W. Gasparotto, Onion Creek Ranch, Texas 5/8/14
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