Meningeal Worms & Neuropathy in Dogsby Heather Beach
Neuropathies in dogs are disorders of the peripheral nerves of the body -- these are the nerves that exit the spinal cord, controlling the conscious and unconscious processes of the body. The meningeal worm is a parasite that causes disease mostly in llamas and alpacas. Fortunately, it is not known to infect dogs. Dogs may suffer from a peripheral neuropathy following a protozoal infection, however.
Peripheral Neuropathies in Dogs
"Neuropathy" is a broad term that describes diseases that affect the peripheral nerves as they exit the spinal cord. Diseases of the peripheral nervous system are different from diseases of the central nervous system, which is composed of the brain and spinal cord. Peripheral neuropathies are classified by their underlying causes and by the function of the nerves affected by the disorder. Causes of peripheral neuropathies include inflammatory diseases, degenerative diseases, metabolic diseases, toxic disorders and direct trauma to the nerves. The types of nerves impaired by a neuropathy include nerves responsible for coordination and voluntary movement in the dog and nerves responsible for unconscious body functions such as breathing or digestion.
Meningeal Worm Infections
If you or a friend own farm animals like llamas or alpacas, you might be familiar with a parasite called the meningeal worm. The meningeal worm, Parelaphostrongylus tenuis, is a parasite that normally resides in the connective tissue and blood capillary network surrounding the brain or meninges of its definitive host, the white-tailed deer. This parasite causes no clinical signs in the definitive host; but when it infects aberrant hosts such as llamas, alpacas, sheep or goats, it will migrate throughout the central nervous system of the animal and cause dramatic neurological symptoms. No case reports of meningeal worm infection in dogs are known; the parasite has been found only in species more closely related to deer, including small ruminants, camelids, cattle, horses and other wild cervids.
One specific type of neuropathy in dogs is caused by a protozoal parasitic infection, referred to as protozoal polyradiculoneuritis. This form of neuropathy is caused by infection by Neospora canis or, less commonly, by Toxoplasma gondii. Neospora canis infections are more likely to affect puppies and younger dogs than older dogs, but dogs of all ages are susceptible. Dogs become infected with Neospora canis by eating raw meat containing Neospora sporocysts. This infection can be transmitted from mother to puppies through the placenta, even if the mother is not showing symptoms of the disease. Treatment with medication is possible, but the disease is often fatal in severe infections. Signs of protozoal polyradiculoneuritis include weakness, lack of coordination, paralysis and difficulty swallowing.
Diagnosis, Treatment, and Prognosis
It can take some time to definitively diagnose the underlying cause of a dog's neuropathy. Your veterinarian may refer you to a specialist in veterinary neurology for additional tests and treatments. A specific treatment plan and accurate prognosis cannot be made for your dog until a definitive diagnosis is found for the neuropathy. Some neuropathies, such as coonhound paralysis or those secondary to metabolic disorders like hypothyroidism, tend to respond well to treatment. Degenerative causes of neuropathy generally have a poor prognosis for return to full function.
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