Many internal and external parasites can cause central nervous system disorders. After ruling out other illnesses like rabies that have similar symptoms of central nervous system involvement, the veterinarian tries to detect the parasite that may be causing it.
Some of the common parasitic infestations with central nervous system involvement are:
Tapeworm infestation known as Coenurosisby Taenia multiceps is commonly found not only in dogs, but in other domestic animals such as horses, sheep, cattle, goats, and rabbits also. Taenia multiceps is a parasite in the small intestine of people too.
As an intestinal parasite, the adults do not do much damage to its hosts, but the larvae of the worm migrates to other parts of the body, including the brain and the spinal cord, causing inflammation. As they grow increasingly large in the brain tissue, it causes trauma to the brain by exerting pressure. The symptoms include loss of balance, stumbling, head tilting, loss of motor control, and paralysis. The dog may become blind also.
Regular deworming may help keep the dog free of severe infestation. Dogs should not be allowed to eat the flesh and organs of infected animals.
Another tapewormEchinococcus granulosuscauses the parasitic disease echinococcosis in dogs. They typically live in the small intestine, and the eggs are passed along with the feces. Humans and several animals such as cattle and sheep that ingest the eggs become the intermediate hosts for this worm.
The infestation by the adult worm doesn’t usually cause severe symptoms, but the larvae invade other tissues including the brain of dogs and form cysts. They are thick-walled and large in size, and cause brain tumor-like symptoms.
Besides controlling the tapeworm infestation by drugs, the dog may require a surgery for removing the cysts.
Two types of lung flukes belonging to the Paragonimus genus are known to form cysts in the dogs’ brain as well as spinal cord. They infect not only dogs, but cats and humans too.
Blood flukes or Schistosomes, infect humans and many domestic animals, including dogs. Their eggs are usually laid in the blood vessels of the gastrointestinal tract or the urinary bladder and get excreted along with urine and feces. But occasionally the eggs may reach the brain or the spinal cord through the blood stream and form capsules, causing symptoms of central nervous system disorders.
Roundworms are very common in domestic animals including dogs. The larvae of the roundworm Toxocara which are known to cause blindness in people by invading the eyes, as well as those of other ascarid worms can cause damage to the central nervous system of dogs if they invade the brain or the spinal cord during their migration.
The larvae of Baylisascaris procyonis, an intestinal parasite of raccoons, can cause damage to the central nervous system of many domestic animals, including dogs, if as they invade the brain and the spinal cord. They are known to infect humans and cause damage to the eyes. Children are the most affected.
The heartworm Dirofilaria immitis may infect the brain and the spinal cord of dogs, besides their heart and eyes.
Disease Caused by Insects
The larvae of dipteran flies such as botflies, blowflies and warbles may develop inside the skin and other tissues of dogs and other animals, causing a condition called myiasis. For example, the fly Cuterebra, deposits its larvae in the subcutaneous skin tissue of dogs and cats, but they may wander to other tissues including the brain, causing central nervous system disorders.
Drugs containing organo phosphates are effective against most types of dipteran larvae, but they have severe toxic effects on the nervous system. To prevent damage to the brain by the inflammation that follows the presence of the larvae, anti-inflammatory medication, including corticosteroids are also used.