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Infectious Diseases

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1. Canine Distemper
Also known as Hard Pad Disease, this is a highly contagious, systemic, viral disease of dogs and is the leading cause of  infectious disease deaths in dogs worldwide.
It is most common in unvaccinated puppies prior to 3-8 months of age, because these puppies have lost the protection of Maternal antibodies.
Etiology & Symptoms
Canine Distemper is caused by Paramyxovirus, closely related to Measles virus
It has a special affinity for attacking epithelial cells
Symtoms : 1st Stage: Begins with fever, loss of appetite, listlessness and a watery discharge from eyes along with diarrhoea. Dog continues to run a fever, gets better for a day or two and then seems to get worse. 2nd Stage: 2-3 weeks after the onset of the diseases some dogs develop signs of brain involvement - attacks of slobbering, head shaking and chewing movements followed by epileptic seizures.
Hard Pad: This is a form of distemper in which the virus attacks the skin of feet and nose, causing a thick horny layer to form on the nose, and callus like pads to form on the feet.
Treatment & Prevention
This is directed at limiting secondary bacterial infection.. Antibiotics, Electrolyte solutions, dietary supplements and anti-convulsants are used. Prevention is the best approach by using Modified Live Vaccines from 6-8 weeks of age.

2. Canine Hepatitis
This is caused by Canine Adenovirus Type I  and is a highly contagious viral disease transmitted only to dogs. Ingestion of saliva, urine or faeces of infected dogs is the main route by which the infection is spread. Recovered dogs shed the virus in their urine for over 6 months.
Clinical Symptoms vary from slight fever to death. The first sign is fever (biphasic) followed by annorexia, thirst, conjuctivitis and serous discharge from the eyes and nose.
Treatment & Prevention
Extensive fluid therapy, broad spectrum antibiotics and symptomatic treatment is given. But the disease is best prevented by modified live vaccines.

3. Parvo
This is one of the most dreaded diseases in dogs, as the onset is rapid, and the morbidity and mortality are very high. It is an enteric (intestinal) disease, caused by the Canine Parvovirus, which mostly affects puppies because it has a special affinity for rapidly dividing cells. But dogs of all ages can be affected, but puppies less than five months are most prone.
There are 2 forms of the disease.
Enteric form: Severe depression, loss of appetite, vomiting, tucked up appearance, high fever followed by profuse diarrhoea which is usually bloody.
Cardiac form: Muscles of the heart are affected in puppies less than 3 months of age. There could be sudden death.
Treatment & Prevention
Treatment may be successful or not depending on the severity of the disease and the age of the dog. Fuid therapy with electrolytes is usually combined with antibiotics and symptomatic therapy.
A vaccination schedule including a series of vaccinations given to young puppies with the advice of your vet, can prevent this deadly disease. Annual vaccinations are required to maintain the immunity.

4.Corona Virus Enteritis:
This is a highly contagious disease worldwide. It is very similar to Parvo, but less severe. It spreads rapidly and the severity depends on the condition of the dog. The mode of infection is through the infected faeces.
Symptoms include vomiting, diarrhoea with soft faeces that maybe yellow or mixed with blood.
the disease is more severe in puppies though it may affect dogs of any age.
Some veterinarians feel that Canine Corona Viral enteritis is underdiagnosed because the symptoms in the dog closely resembles that of parvo and also there maybe an actual concurrent infection by parvo virus.
It should be suspected whenever there is rapid spread of gasdtrointestinal disease among dogs.
Treatment & Prevention
Fluid therapy, electrlytes and antibiotics are used to treat the symptoms. Prevention is by the use of Modified Live vaccines.

5. Leptospirosis
This is caused by L. Coanicola and L. Icteohaemorrahgiae, it spreads by the urine of infected animals.
The dogs get infected either by a break in the skin or when it drinks water or food that is contaminated by infected urine. Most cases are mild.
Though it affects many organs the kidneys are most affected.
A hunched gait because of pain in the kidneys, formation of ulcers in the mouth and tongue, bleeding from the mouth, passage of bloody stools and severe thirst with increased urination are the main symptoms.
Sometime the liver is involved causing jaundice. This disease is realtively rare these days
Treatment & Prevention
Treatment is by fluid therapy and broad spectrum antibiotics. It is found that dogs which have been vaccinated, still get affected sometimes.

6. Parainfluenza
Parainfluenza and Canine Adenovirus-2 are highly infectious diseases of the respiratory tract. They are transmitted by air, and readily cause localised infections.
The disease itself is mild, but secondary bacterial infections cause a more severe manifestation.
Coughing of various intensity and frequency, along with fever is the common symptom.
The dogs usually recover within 3-7 days.
There is no specific anti-viral treatment, but antibiotics are used to control the secondary bacterial infection.

7. Rabies
One of the most feared diseases, rabies is an acute viral encephalomyelitis (affecting the brain), that particularly affects carnivores and insectivore bats although it can affect any mammal.
Once the clinical signs appear, the disease is almost invariably fatal.
Many countries have managed to become free of rabies through successful eradication programmes.
Transmission is by the introduction of the virus laden saliva into the tissues. The incubation period maybe prolonged and variable.
After entering the muscle cells, the virus replicates itself, and travels via the peripheral nerves to the spinal cord, and ascends to the brain. From here it once again travels through the peripheral nerves to the salivary glands.
Rabid animals of all species exhibit typical signs of CNS disturbance. The most reliable signs are unexplained behavioural changes and paralysis. Clinical disease has 3 forms.
Prodromal Stage: Lasts for 1-3 days. Typical signs are vague CNS symptoms progressing rapidly.
Furious form: This is classical Mad Dog Syndrome. The animal becomes irrational and with the slightest provocation, viciously and aggressively uses its teeth, claws (and horns or hooves in the case of other animals). The posture gives an appearance of alertness and anxiety with dilated pupils. Such dogs when allowe to roam, frequently attack people, or any moving object. They chew the wire and frames of their cages. Muscular incoordination and seizures develop. Death is the result of progressive paralysis.
Paralytic form: This presents with paralysis of the throat and muscles of trhe jaw, with profuse salivation and inability to swallow. The lower jaw drops down. The paralysis progresses to all parts of the bodyand coma and death follow in a few hours.
Features of the various Anti-Rabies vaccines used currently.
a) Modified Live Vaccines (MLV)
b) Killed Vaccines
c) Subunit vaccines
Modified Live Vaccines:
Micro organisms used in the vaccine are altered in such a way that they are no longer virulent to the majority of host species. But they still retain their antigenic properties to stimulate a protective immune response.
Strong systemic immunity and local immune response are produced by local administration of certain MLV vaccines.
MLV must replicate after innoculation to produce enough antigen to induce interferon in the next few days after immunization, providing early protection against some virulent viral infections.
Certain MLV can induce immunosuppression, may be shed into the environment and may revert to virulence or cause vaccine induced disease.
Killed Vaccines:
Safer than MLV
To induce a protective immuno response, killed vaccines require a large antigenic dose, multiple immunizations and use of an adjuvant.
More costly than MLV
Local and systemic vaccine reactions may occur.
Provide a strong immune response and a long duration of immunity.
Killed vaccines work by using more antigen (since killed products can not grow in the body of the recipient) and contain an adjuvant which mimics a live replicating vaccine by releasing the antigen slowly over a period of time and by stimulating WBC's to produce a better immune response.