In 1993 in the Serengeti of Tanzania, there was an epidemic of canine distemper virus in lions and spotted hyenas. Canine distemper virus is a disease in carnivores that is similar to the disease of measles in humans. It attacks the lymph nodes, respiratory, urogenital, gastrointestinal, and nervous systems. Fever, eye discharge, coughing, vomiting and diarrhea are the common symptoms of this disease. A team of international scientists in part with the German Leibniz Institute for Zoo and Wildlife Research discovered why the canine distemper virus outbreak in 1993 was so disastrous for spotted hyenas and lions. This strain of canine distemper virus differentiated from the domestic canine distemper virus due to three rare mutations. Two out of the three rare mutations in the lethal canine distemper virus were found to increase the ability of canine distemper virus in lion and spotted hyena cells. When the canine distemper virus epidemic first occurred in Tanzania, it reduced the lion population by 30% and killed a large amount of spotted hyena pups. After the initial outbreak, the lethal canine distemper virus continued to affect and be fatal toward canines of the Serengeti but did not effect lions and spotted hyenas in later years. This led to a very long debate in scientists about why this canine distemper virus was no longer fatal to lions and spotted hyenas, and why is was so lethal in the original outbreak in 1994. Scientists collected canine distemper virus strains in a range of carnivores since 1993 to 2012 and discovered that in the 1993 strain of canine distemper virus there was a new genetic lineage.
This strain of canine distemper virus had a rare mutation in the CDV-H protein and the CDV-V protein. The CDV-H protein plays an important part in facilitating virus entry into host cells and the CDV-V protein enables the virus to manipulate the immune response of the host. This left those infected more vulnerable to the virus and made it more fatal for lions and spotted hyenas. The difference between the strains found in canines of Tanzania and spotted hyenas and lions were that the canine distemper virus also had a rare amino acid sequence in lions and spotted hyenas. This made a clear distinction of the canine distemper virus that was in canines of the Serengeti and the spotted hyenas and lions. The mutation made it easier to infect cat cells rather than dog cells which is why it had a harder effect on lions and spotted hyenas, who are not canid species with dog-type cells. The reason that this strain of canine distemper virus did not continue in lions and spotted hyenas was because it was so deadly that it completely died out. The current canine distemper virus in Tanzania and all over the world is more effective in invading canid or dog cells.
This was the most interesting article I have read since this blog post assignment. I am a veterinary technician and one of the vaccines that veterinarian practices must administer to their dogs is a canine distemper virus vaccine for the canine parvovirus-2/canine adenovirus-2 (CAV-2) strain. This is a required vaccination for dogs in the state of New Jersey, as well as many other states, along with the rabies vaccine. This disease is highly contagious and is air-borne as well. I have seen dogs enter in the hospital with this disease and there is no cure. More times than not, the result is eventually that the owner decides to euthanize their pet because the symptoms can not be alleviated and their pet is in constant pain. Usually anorexia develops in the dog while the virus attacks it's whole system. Although this virus can be controlled with antibiotics and medication, the overall outcome of the situation is unfavorable for any canine that contracts it. Due to the nature of the animal hospital I work at, we see small animals as well. Ferrets are effected by canine distemper virus as well, and the vaccine used in dogs is the same that we use to vaccinate ferrets. It is extremely lethal in ferrets and most owners, although not required by the state, get this vaccination for their pet. Canine distemper virus effects more animals than it's name suggest and this article is further proof of it's presence in wild animals as opposed to domesticated dogs. I was surprised that this strain effected non-canid species despite knowing it effected an array of other carnivores, I was always told cats were the exception to the rule. With more genetic information being available and biotechnology continuing to make great strides, one can hope that eventually canine distemper virus will have a cure.
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