Hind leg weakness in dogs. Could it be canine distemper?
What is canine distemper?
It is a disease caused by an RNA virus of the genus Morbillivirus which belongs to the Paramyxoviridae family. It is one of the most common and lethal communicable diseases in dogs. It is transmitted by direct contact with sick animals. Distemper initially replicates in lymphoid tissue and causes a state of severe immunosuppression.
It then infects the rest of the viscera and the central nervous system, causing, among other signs, hind leg weakness in dogs. The incubation period is 14 to 18 days. There are different strains of varying virulence, which results in clinical pictures of distinct severities and evolutions. It mainly affects young dogs aged 3 to 6 months, although cases have been reported in elderly animals and it can cause chronic encephalitis in adult animals.
Canine distemper: clinical picture
Among the different clinical signs it is common to find fever, conjunctivitis, rhinitis, cough, diarrhoea, vomiting, anorexia, dehydration, weight loss, mucopurulent discharge, pneumonia (secondary bacterial infections due to Bordetella), paw pad hyperkeratosis and impetigo.
With regard to central nervous system involvement, dogs may show signs of encephalitis with myoclonus, ataxia, circling behaviour, hyperaesthesia, muscle stiffness, barking, seizures and blindness. Neurological signs can sometimes develop several weeks or months after recovery from an acute episode of distemper or after subclinical infections.
There are two forms of chronic encephalitis that affect adult animals.
- Multifocal encephalitis is characterised by a lack of coordination, hind leg weakness, menace reflex deficit, an inclined head, nystagmus, facial paralysis and head tremors without myoclonus. It occurs in dogs aged 4 to 8 years and has a slow, progressive course of approximately one year. The disease pattern usually develops into paralysis.
- Old dog encephalitis, an uncommon condition that is reported in dogs over 6 years old, is characterised by visual and menace reflex deficits, with the progressive onset of mental depression, severe personality changes, circling behaviour and inability to keep the head upright.
Canine distemper: treatment
Treatment is based on supportive treatment with broad-spectrum antibiotic therapy, vitamin complex, fluid therapy and forced nutrition. There is no treatment to eliminate the virus once the animal has been infected.
Prevention revolves around the vaccination of 6–8-week-old puppies, with boosters given after 3–4 weeks and annually. The vaccine is ineffective in dogs that have already been infected.
The prognosis is guarded, especially if there are associated neurological signs, as they indicate that the disease is in an advanced stage. The mortality rate is between 50–90% depending on the virulence of the strain. Dogs which survive distemper usually have behavioural disorders caused by damage to the nervous system.