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Brain Inflammation Due to Parasitic Infection in Dogs

Encephalitis Secondary to Parasitic Migration in Dogs

Encephalitis, or inflammation of the brain, can arise from various causes in dogs. One potential cause is the migration of parasites into the central nervous system (CNS). These parasites can enter the CNS through the bloodstream or through adjacent tissues such as the middle ear, natural openings in the skull, nasal cavities, the cribriform plate (a part of the skull), or open fontanelles, which are also known as “soft spots.”

These parasites may typically affect another organ system within the same host, such as Dirofilaria immitis, Taenia, Ancylostoma caninum, Angiostrongylus, or Toxocara canis. Alternatively, they may come from different host species, such as raccoon roundworm (Baylisascaris procyonis), skunk roundworm (B. columnaris), Coenurus spp., or Cysticercus cellulosae. Dirofilaria immitis is commonly found in adult dogs, while the other parasites generally infect younger pups that spend time outdoors.

Symptoms and Types

Symptoms associated with this form of encephalitis can vary depending on which part of the central nervous system (CNS) is affected. For instance, Cuterebriasis typically occurs between July and October in the United States and presents with sudden changes in behavior, seizures, and vision problems. On the other hand, Angiostrongylus cantonensis, a common rat parasite in Australia, may induce lumbosacral syndrome in puppies, resulting in paralysis or weakness in the hindlimbs, tail, and bladder. Moreover, parasite infections often manifest asymmetrically, affecting one side of the body more than the other.


The primary route through which a dog contracts this form of encephalitis is by inhabiting a cage previously occupied by an infected host, such as raccoons or skunks.


When consulting the veterinarian, it’s crucial to provide a comprehensive history of your dog’s health, detailing the onset and characteristics of the symptoms. The veterinarian will conduct a thorough physical examination along with a biochemistry profile, urinalysis, and complete blood count (CBC). Typically, these tests yield normal results unless the parasites have spread to other organs.

Computed tomography (CT) or magnetic resonance imaging (MRI) of the brain might uncover a focal lesion or cerebral tissue damage resulting from blockage of cerebral blood vessels, both indicative of parasitic infections. Another common diagnostic method involves a cerebrospinal fluid tap to confirm parasitic infection, although results may appear normal despite the presence of encephalitis.


Administration of medications like anthelmintics (dewormers) is often employed to eradicate the parasites, although this approach may entail potential complications. It’s imperative to seek guidance from your veterinarian regarding the most suitable treatment plan. Puppies afflicted with a mild manifestation of angiostrongylosis might achieve full recovery with supportive care and corticosteroid therapy alone. Alternatively, in certain instances, surgical extraction of intracranial parasites (such as Cuterebra) might be required.


The majority of parasitic infections affecting the central nervous system are untreatable and worsen over time. To shield your dog from such infections, it’s advisable to keep them indoors and away from wild animals. Additionally, the administration of dewormers, anthelmintics, and dirofilaricides can serve as preventive measures against infection.

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