A number of parasites (including worms and insects) are associated with central nervous system disease. Diagnosis requires eliminating other possible causes of illness and identifying the specific parasite responsible.

Tapeworms

Coenurosis (also called gid, sturdy, or staggers) is caused by Taenia multiceps, an intestinal tapeworm of dogs and people. Other animals, such as sheep, goats, deer, rabbits, horses, and cattle can carry and spread this parasite to dogs. The larval stage of the parasite can invade the nervous system and lead to swelling of the brain and spinal cord. The adult worm may grow to more than 2 inches in diameter and cause increased pressure on the brain, which results in loss of motor control, blindness, head tilting, stumbling, and paralysis.

Roundworms

Several types of roundworms are found in domestic animals.

Setaria digitata is found in Asia and is a common parasite of cattle. Mosquitoes are intermediate hosts. In horses, the developing worms invade the central nervous system and cause weakness, lack of coordination, lameness, drooping eyelids or ears, and paralysis.

Migrating larvae of strongyles (Strongylus vulgaris and Draschia megastoma) and rhabditids (Halicephalobus gingivales) have been reported in the central nervous system of horses.

Disease Caused by Insects

Myiasis is the development of larval dipteran flies (bots and warbles) within the body's tissues or organs. Hypoderma subspecies have been found in horses. Organophosphate drugs can eliminate certain dipteran larvae from the nervous system, but they can also cause nervous system damage. Corticosteroid drugs are often recommended to prevent additional inflammatory damage and pressure on the brain during treatment (see Skin Disorders of Horses: Flies and Mosquitoes of Horses).

Last full review/revision July 2011 by William B. Thomas, DVM, MS, DACVIM (Neurology); Daniela Bedenice, DrVetMed, DACVIM, DACVECC; Kyle G. Braund, BVSc, MVSc, PhD, FRCVS, DACVIM (Neurology); Cheryl L. Chrisman, DVM, MS, EDS, DACVIM (Neurology); Caroline N. Hahn, DVM, MSc, PhD, DECEIM, DECVN, MRCVS; Charles M. Hendrix, DVM, PhD; Maureen T. Long, DVM, PhD, DACVIM; Robert J. Mackay, BVSc, PhD; Karen R. Munana, DVM, MS, DACVIM (Neurology); Charles E. Rupprecht, VMD, MS, PhD; Josie L. Traub-Dargatz, DVM, MS, DACVIM; Susan L. White, DVM, MS, DACVIM