by Stacy Matthews Branch, DVM, PhD, FACFE, DABFM
What you Need to KNOW!
There is no cure for pug dog encephalitis. The outlook is not very good for dogs diagnosed with PDE. However, some can survive for more than a year with anticonvulsant treatment (anti-seizure drugs).
Research at the University of California, Davis led to the development of a new DNA test to determine the risk for a pug dog of developing PDE and to facilitate breeding programs that can produce puppies that are at lower risk of developing the disease (3).
Pug dog encephalitis (PDE) is a form of granulomatous meningoencephalitis (GME). The term GME describes an inflammation of the central nervous system (CNS). More specifically, it is an inflammation of the brain and meninges. The term meninges refers to the membrane covering the brain and spinal cord. The term granulomatous refers to the specific type of inflammation that consists of a nodular or ulcerative nature.
Granulomatous meningoencephalitis can be observed in young and middle-aged toy breeds. Pug dog encephalitis does not have a sex predilection per se, but tends to affect females more frequently. The specific form known as PDE is also referred to as necrotizing meningoencephalitis (NME). The clinical NME condition can affect Maltese, Yorkshire Terrier, and other breeds, but primarily affects Pugs. It can be acute or chronic and is often without a known cause (idiopathic). This discussion will focus on chronic NME (PDE).
Pug dog encephalitis appears to be hereditary and littermates are often affected. It is thought that the condition is associated with an abnormal immune response. In this case, the immune system cells (white blood cells) attack the affected dogs’ own brain and other CNS cells (autoimmune response). Studies are ongoing to identify the genetic basis of the disease and may have some similarities to multiple sclerosis in humans (1). NME is associated with a region (called dog leukocyte antigen) of one chromosome (chromosome 12) (1). This region is important in the animal’s immune response. The human counterpart of this chromosomal region is associated with various autoimmune diseases.
Just over 1% of dogs with PDE ultimately die from the disease very soon after onset. Overall, the time from disease onset to death varies greatly and can be as soon as 1 day to well over a year. Death is often preceded by coma or a seizure. Affected dogs have symptoms associated with the severe inflammation of the brain tissue. Research is somewhat limited for this disease and not much is known regarding optimal pug dog encephalitis treatment options. The disease is difficult to prevent due to the primary genetic cause of the disease.
What clinical signs (symptoms) are observed with pug dog encephalitis?
Pug dog encephalitis symptoms are associated with the inflammation/lesions of the CNS, primarily the brain tissue. Symptoms can include signs of lethargy and depression. However, common pug dog encephalitis symptoms also include seizures, walking in circles, abnormal or atypical behaviors, and signs that indicate blindness. One may also notice that the dog’s head is consistently tilted to one side. The dog may stagger (ataxia) or can be seen pressing the head against solid objects (walls, doors, etc.). The dog may also walk or move as if the neck is stiff or in pain.
How is pug dog encephalitis diagnosed?
The history and the veterinarian’s general physical and neurological examinations are important in determining the cause of abnormal behaviors and other symptoms. The breed, age, and gender are taken into account when assessing the history and exam results. The progression of the observed symptoms is also a factor in arriving at an accurate diagnosis.
The neurological examination entails examining the dog’s attitude and behavior and examining the reactions to specific stimuli. In addition to assessing these reactions, the gait and posture are also observed. The dog’s ability to change position as needed or respond to balancing manipulations are also assessed. These approaches help determine the part of the nervous system likely to be affected.
Routine tests are needed to determine the overall health status (blood tests, urinalysis, etc.). Tests associated with nervous system health include analysis of the spinal fluid (i.e., spinal tap). The spinal fluid will often show an elevation of protein and increased numbers of specific types of white blood cells called monocytes. Magnetic resonance imaging can reveal specific lesions associated with the necrotizing and inflammatory brain and meninges (2). If an animal dies or is euthanized, the brain tissue can be submitted to the laboratory for microscopic analysis (histopathology). The specific cellular lesions can be identified to confirm a diagnosis.
What are the treatment options for pug dog encephalitis?
Pug dog encephalitis treatment may include immunosuppressive approaches used in the granulomatous form of meningoencephalitis. This approach entails the use of corticosteroids or certain cytotoxic agents. The corticosteroids (i.e., prednisone) may help decrease the inflammatory and aberrant immune responses. Immunosuppressive agents such as cyclosporine A have been also been used alone or with a corticosteroid. Anticonvulsants (anti-seizure drugs) may help to control the seizures (the most common pug dog encephalitis symptom). Given the genetic basis of PDE, affected dogs should not be bred. Also, the parents of the affected dogs should not be bred further.
1. Greer KA, Wong AK, Liu H, Famula TR, Pedersen NC, Ruhe A, Wallace M, Neff MW. (2010) Necrotizing meningoencephalitis of Pug dogs associates with dog leukocyte antigen class II and resembles acute variant forms of multiple sclerosis. Tissue Antigens. 76(2):110-8.
2. Young BD, Levine JM, Fosgate GT, de Lahunta A, Flegel T, Matiasek K, Miller A, Silver G, Sharp N, Greer K,Schatzberg SJ. (2009) Magnetic resonance imaging characteristics of necrotizing meningoencephalitis in pug dogs. J Vet Intern Med. 23(3):527-35.
3. Skernivitz S. (2011, July 1). DNA assessment identifies NME risk
in pugs. DVM Newsmagazine, from http://veterinarynews.dvm360.com/dvm/article/articleDetail.jsp?id=729107