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Canine Distemper (Hardpad Disease)

By Otto M. Radostits, CM, DVM, MSc, DACVIM (Deceased), Professor Emeritus, Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan ; David A. Ashford, DVM, MPH, DSc, Assistant Area Director, International Services, APHIS, USDA ; Craig E. Greene, DVM, MS, Professor, Department of Small Animal Medicine, College of Veterinary Medicine, University of Georgia ; Eugene D. Janzen, DVM, MVS, Professor, Production Animal Health, Faculty of Veterinary Medicine, University of Calgary ; Bert E. Stromberg, PhD, Professor, Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota ; Max J. Appel, DMV, PhD, Professor Emeritus ; Stephen C. Barr, BVSc, MVS, PhD, DACVIM, Professor of Medicine, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University ; J. P. Dubey, MVSc, PhD, Microbiologist, Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, USDA ; Paul Ettestad, DVM, MS, State Public Health Veterinarian, Epidemiology and Response Division, New Mexico Department of Health ; Kenneth R. Harkin, DVM, DACVIM, Associate Professor, College of Veterinary Medicine, Kansas State University ; Delores E. Hill, PhD, Parasitologist, U.S. Department of Agriculture ; Johnny D. Hoskins, DVM, PhD, Small Animal Consultant ; Jodie Low Choy, BVSc, BVMS, IVAS Cert, Menzies School of Health Research; University Avenue Veterinary Hospital, Northern Territory, Australia ; Barton W. Rohrbach, VMD, MPH, DACVPM, Associate Professor, Department of Comparative Medicine, Veterinary Teaching Hospital, University of Tennessee ; J. Glenn Songer, PhD, Professor, Department of Veterinary Science and Microbiology, University of Arizona ; Joseph Taboada, DVM, DACVIM, Professor and Associate Dean, Office of Student and Academic Affairs, School of Veterinary Medicine, Louisiana State University ; Charles O. Thoen, DVM, PhD, Professor, Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University ; John F. Timoney, MVB, PhD, Dsc, MRCVS, Keeneland Chair of Infectious Diseases, Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky ; Ian Tizard, BVMS, PhD, DACVM, University Distinguished Professor of Immunology; Director, Richard M. Schubot Exotic Bird Health Center, Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University

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Canine distemper is a highly contagious, whole body, viral disease of dogs. It is characterized by fever, loss of white blood cells, and inflammation of the lungs and brain. The disease is seen worldwide in Canidae (dogs, foxes, wolves), Mustelidae (including ferrets, mink, and skunks), and several other species of wild animals.

Most cases of canine distemper develop after an animal breathes in the virus from droplets of moisture exhaled by an infected animal (aerosol route). Some infected dogs may spread the infectious virus for several months after outward signs of the disease have passed.

A short fever usually occurs 3 to 6 days after infection. During this stage of the disease, blood tests might show low white blood cell counts. These signs may go unnoticed or be accompanied by loss of appetite. The fever subsides for several days before a second fever occurs. The second fever lasts less than 1 week and may be accompanied by a discharge from the nose and eyes and loss of appetite. Gastro-intestinal and respiratory signs may follow and are usually complicated by bacterial infections. Overgrowth of the skin of the footpads (“hardpad” disease) and the nose may be seen. Signs of central nervous system involvement are frequently seen in dogs with this overgrowth. These signs often include: 1) localized involuntary twitching of a muscle or group of muscles, such as in the leg or face, 2) slight or complete paralysis, often most noticeable in the hind limbs as failure of muscle coordination, followed by weakness and paralysis in all 4 legs, and 3) convulsions with drooling and chewing movements of the jaw (“chewing-gum fits”).

The seizures become more frequent and severe as the disease progresses. The dog may fall on its side and paddle its legs. Involuntary urination and defecation often occur. Infection may be mild with few or no signs, or it may lead to severe disease showing most of the above signs. The course of the disease may be as short as 10 days, but the onset of neurologic signs may be delayed for several weeks or months.

Inflammation of the brain in longterm distemper is often marked by lack of coordination and compulsive movements such as head pressing or continual pacing. These signs may be seen in adult dogs without a history of signs related to canine distemper. The development of neurologic signs is often progressive. Dogs with this form of the disease do not spread it to other dogs.

Your veterinarian will consider distemper infection any time a puppy is feverish and has signs of widespread infection. While the typical case is not difficult to diagnose, the characteristic signs sometimes fail to appear until late in the disease. The infected dog may have other viral and bacterial infections that can complicate the picture Thus, blood work and other tests may be required to confirm the diagnosis.

Treatment is designed to limit bacterial invasion, support fluid balance, and control nervous system problems. Antibiotics, fluids, dietary supplements, medication to reduce fever, analgesics, and anticonvulsants are used as appropriate for the individual dog. No single treatment is specific or uniformly successful. Dogs may recover completely from the infection, but good nursing care is essential. Even with intensive care, some dogs do not make a satisfactory recovery. Unfortunately, treatment for the neurologic problems of distemper is usually not successful. If the neurologic signs are severe or continue to worsen, it may be appropriate to have the dog euthanized. Dogs with some of the longterm, progressive forms of neurologic distemper have responded to immune system treatment with anti-inflammatory drugs or steroids.

Vaccination is the most widely used and best available prevention for canine distemper. Puppies should be vaccinated when they are 6 weeks old and then at 3- to 4-week intervals until they are 14 to 16 weeks old. Annual revaccination has been suggested because of the breaks in neurologic distemper that can occur in stressed or diseased dogs or those with weakened immune systems. Your veterinarian will recommend an appropriate vaccination schedule for your pet taking into consideration the health of your pet, the frequency of the disease in your area, and other risk factors.

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