History of CDV infections in wild populations
by ÖBK
I have chosen to write about cases of canine distemper virus outbrakes in wild populations. I started out working with Kristian Franer on this essay about the CDV outbrake in the Serengeti lions in 1994, when i discovered that this particular virus has caused damage to other carnivore populations throughout the world. I got curious about these cases, since I have only heard of CDV in domesticated dogs. I have gathered some information about outbrakes in the north american black-footed ferret, the peruvian giant otters, caspian seal and mediterrean monk seals.
What is CDV?
Canine distemper is a systemic disease caused by canine distemper virus (CDV). CDV is highly contagious, and seen around the world. Traditionally, CDV was thought to only infect members of the families Canidae (dogs, foxes, wolves), Mustelidae (ferret, mink, skunk), and Procyonidae (raccoon, coati mundi). In 1994, it was discovered that lions living on the Serengeti Plains were serotypically positive for CDV as well, despite previous assumptions that members of the Felidae family were not susceptible to canine distemper virus. CDV belongs to the Paramyxoviridae family. A morbillivirus, it is closely related to both rinderpest and the measles virus. CDV is a double stranded, negative RNA virus with an external envelope. This envelope makes it very sensitive to lipid solvents and most disinfectants, heat, desiccation and UV light. The virus is thus relatively unstable outside the host. The main route of infection is via direct contact with infected animals, and infected animals may actively shed virus in their aerosol excretions for several months. Initial virus replication is in the respiratory tract's lymphatic tissue. Cell associated viremia leads to infection of all lymphoid tissues in the body. Eventually, respiratory, GI, and urogenital epithelium are infected, as is the CNS. Death occurs in up to 80% of all infected dogs, but this differs with the species.
Black-footed ferret, Mustela nigripes
In 1985, the last remnant of the black-footed ferret (Mustela nigripes) population in North America was reduced from an estimated 58 individuals in 1985 to 16 individuals in 1986. This catastrophic decline in numbers was attributed partly to infection by CDV and partly to losses during juvenile dispersal. This severely affected the captive breeding program, which is still running. Contact with contamiated dogs is believed to be the way of contamination.
Peruvian giant otter
The giant Peruvian otter in Manu national park in south america have also had problems with CDV. Mustelids are susceptible to lethal infection with CDV. Since Peruvian giant otters are large mustelids they are probably susceptible to CDV and it is possible that this virus has been responsible for the extinction of the giant otter populations in the Amazon Basin. In some places giant otters live in close proximity to human settlements. In this case, also dogs (their faeces) could well provide a source of infection for the giant otters. Dispersing giant otters, locally known as "solitaries", may travel long distances and so could carry CDV to distant, immunologically naive populations, very vulnerable to this disease.
Mediterranean monk seal, Monachus monachus
The mediterrean monk seal is one of Europe's most endangered marine mammals. In 1997, a mysterious mass mortality event wiped out two thirds of the world's largest surviving colony of Mediterranean monk seals in Mauritania-western Sahara. Although the precise cause was never conclusively established, the most believed theory was a morbillivirus outbreak. Seals are vulnerable to a series of different mobilliviruses, CDV and and its variant, PDV (phocine distemper virus) being the worst threats. DVM, the dolphin morbillivirus. A similar historical case in 1955 occured amongst crab-eating seals in Antarctica, when the Americans mounted an expedition to the South Pole using non-vaccinated dogs. The dogs were dying of CDV and they probably dumped them in the water, causing an enormous mortality among the seals.
Caspian seals, Phoca caspica
During the spring of 2000, high death rates were reported in Caspian seals which live only in the Caspian Sea and are listed as a vulnerable species by the International Union for the Conservation of Nature. The die-off was first reported near the mouth of the Ural River, Kazakhstan, in late April; it subsequently spread south to the Mangistau region. More than 10,000 seals are estimated to have died during April and May along the Kazakhstan coast. High death rates were also reported in May and June along the Apsheron peninsula of Azerbaijan and the Turkmenistan coast. Evidence have been presented that canine distemper virus infection was the primary cause of these deaths.
Conclusion
CDV is a widespread and dangerous viral disease that will keep on threatening different populations of Canidae, Mustelidae, Procyonidae and Felidae all over the world. It has long occured as a dangerous virus, in the wild, in zoos, as well as in domesticated species. It has caused severe problems for a lot more species than i have listed, for exaple, it is believed by some to have caused the extinction of the Tasmanian wolf, (Thylacinus cynocephulus) in the first decade of the last century. Great precautions and much resources must be used to prevent total exticion of different species because of this virus. One thing is to vaccinate susceptible domesticated animals to prevent them being vectors towards wild animals as in the Serengeti case.
Sources
ÖBK collected material from various websites and made his own conclusion. The problem is that copy-pasting from various sources is still patchwork plagiarism.
Please, note copy-right information at one of his sources:
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