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HISTORY:
- EXTINCTION VS. SURVIVAL -
(page 3)
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Disease (continued):

    In an article entitled "Wild Dogs and Tigers", published in the Examiner newspaper of the 19th October 1934 (p. 4), comment is made on both the distemper epizootic in wild dogs, and the illness described as being mange or distemper-like that decimated thylacine numbers:

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    "The time came, said the speaker, when the whole of the country was ravaged by wild dogs.  It was said that these creatures were in many instances descendants of dogs which had got away from the aboriginals and were reverting to the type from which they had evolved.  They were a terrible nuisance.  Assistance eventually had come to the rescue of the pastoralists in a form of what
Beaumaris Zoo (QD)
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An image from a film made at the Beaumaris Zoo (QD) in early 1928.  The footage shows a group of three thylacines interacting; an adult female and two juveniles (which incidentally, are not directly related to her).  Sadly, she and both of her cubs (not shown here) died of an unspecified disease shortly after this film was made.
was known as common distemper in dogs, and this wiped out the whole population of the wild dogs and most of the tame dogs as well.  The number of native tigers increased tremendously after the destruction of the wild dogs, probably because they had been freed from their natural enemies.  In the late (18)70's and early (18)80's these animals became a big menace to the sheep owners.  Experienced pastoralists were forced to throw up thousands of acres of magnificent sheep country because of the ravages of the tigers.  But once again nature had taken a hand, and a disease which was a kind of mange appeared and cleaned the tiger out from most of the pastoral country.  It was several
years now since a single specimen had been seen in populated parts of the state.  It was thought that some were to be found in parts of the north-west and west.  The Fauna Board was taking steps to prevent the complete extermination of the tiger, which was one of the wonders of the fauna world.  It was an animal of its own kind and there was no more like it.  Its complete extermination would be a national calamity".
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   Dr. Bob Paddle (2000), when referring to the epizootic disease in his book "The Last Tasmanian Tiger", states:

    "In the wild it was anecdotally described as 'distemper' or 'mange' and distressed individuals, exhibiting significant hair loss or scabs over the head or body, were easily killed, and when snared, frequently made little attempt to free themselves, and often died as a result of the additional trauma of capture".

    Paddle's research on captive thylacines suggests the disease was episodic and debilitating, with symptoms varying depending on severity, rather than always having a fatal outcome.  Bleeding skin lesions, together with hair loss to the body, limbs and tail were the outward manifestations found in both the mild and severe forms, with the extent varying according to severity.  In the worst affected cases, loss of appetite and diarrhoea were also present.  Paddle (2012) notes: 

    "These symptoms could persist for up to four days.  On occasions when a captive animal survived a first bout of illness, it reoccurred at two to three month intervals".

    With reference to the possible cause of the disease, Sleightholme & Campbell (2015) state: "The canine distemper virus (CDV) is an enveloped, single stranded, negative RNA virus of the family Paramyxoviridae, genus Morbillivirus that is closely related to the measles virus.  There is no evidence to suggest that marsupials can contract CDV.  Feline panleukopenia virus (FPV) or feline distemper is an entirely different disease to canine distemper, and is not transmissible to dogs or marsupials.  Distemper in either its canine or feline form can therefore be eliminated as a cause of the epizootic disease.  From Paddle's description of the symptoms, certain outward manifestations of the disease are those one would commonly associate with sarcoptic mange, a highly contagious infestation of Sarcoptes scabiei canis, a burrowing mite.  The canine sarcoptic mite can also infest cats, pigs, horses, sheep and various other species. Marsupials known to be prone to infection include the Common wombat (Vombatus ursinus), Southern Hairy-nosed wombat (Lasiorhinus latifrons), koala (Phascolarctos cinereus), Agile wallaby (Macropus agilis) and Common Ringtail possum (Pseudocheirus peregrinus).  The incubation period for clinical signs to develop is around 14 days, but can be as short as 24 hours in cases of re-infection.  The mites burrow into the skin, causing intense itching which results in scratching and biting.  Scab formation and hair loss frequently appear first on the elbows and ears.  Secondary skin infection is common.  Animals infected with sarcoptic mange are often emaciated and in poor condition.  In advanced stages, sarcoptic mange has a devastating effect on internal organs, including the heart, liver, kidneys, lungs and reproductive organs.  Mange can also have a negative impact on the reproductive capacity of infected animals - e.g., absence of lactation, reduced litter size and weight, and reduced pup viability and growth rates.  Heavy infestations can also result in anaemia in the young".

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canine sarcoptic mite
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Canine sarcoptic mite (Sarcoptes scabiei canis) under high magnification.
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canine sarcoptic mange
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Scab formation and hair loss with mange infection on a domestic dog (Canis lupus familiaris).
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References
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back to: Extinction vs. Survival (page 2) return to the section's introduction forward to: Extinction vs. Survival (page 4)


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