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Central Nervous System Disorders Caused by Parasites in Cats

By William B. Thomas, DVM, MS, DACVIM (Neurology), Professor, Neurology and Neurosurgery, Department of Small Animal Clinical Sciences, University of Tennessee
Kyle G. Braund, BVSc, MVSc, PhD, FRCVS, DACVIM (Neurology), Director, Veterinary Neurological Consulting Services
Cheryl L. Chrisman, DVM, MS, EDS, DACVIM (Neurology), Professor of Veterinary Neurology, College of Veterinary Medicine, University of Florida
Caroline N. Hahn, DVM, MSc, PhD, DECEIM, DECVN, MRCVS, Senior Lecturer in Veterinary Clinical Neuroscience, Royal (Dick) School of Veterinary Studies, University of Edinburgh
Charles M. Hendrix, DVM, PhD, Professor, Department of Pathobiology, College of Veterinary Medicine, Auburn University
Karen R. Munana, DVM, MS, DACVIM (Neurology), Associate Professor, Department of Clinical Sciences, College of Veterinary Medicine,North Carolina State University
T. Mark Neer, DVM, DACVIM, Professor and Hospital Director, Center for Veterinary Health Sciences, Oklahoma State University
Charles E. Rupprecht, VMD, MS, PhD, Director, LYSSA LLC
Robert Wylie, BVSc, QDA,

Also see professional content regarding CNS diseases caused by parasites.

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


Two species of Paragonimus lung flukes can migrate to the nervous system and produce cysts in the brain and spinal cord of cats, dogs, and people.

Schistosomes, or blood flukes, normally deposit their eggs in the blood vessels of the gut and urinary bladder, from which they pass into the external environment via the feces or urine. Some eggs, however, may get into the bloodstream and reach the central nervous system where they form capsules. This condition has been seen in people and domestic animals.


Several types of nematodes are found in domestic animals.

The larvae of some ascarid roundworms, including Toxocara species, can invade the central nervous system and cause localized damage in cats. Toxocara larvae may also invade the eye and cause vision loss in people.

Baylisascaris procyonis is a roundworm found in the small intestine of raccoons. Its larvae can infect people and domesticated animals and migrate to the central nervous system. This parasite can also cause central nervous system and eye damage in people, particularly children.

Dirofilaria immitis is more commonly known as the canine heartworm, but it can also affect cats. In addition to the heart and lungs, other parts of the body, including the central nervous system and the eye, can be infected.

Gurlita paralysans is found in the spinal veins of cats and has reportedly produced a high incidence of paralysis.

Disease from Insects

Myiasis is the development of certain types of larval flies (bots and warbles) within the body’s tissues or organs. The larvae of Cuterebra, which are deposited under the skin in dogs or cats, have been known to wander into the central nervous system and affect the cerebrum or cerebellum. Organophosphate drugs can eliminate certain insect 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.