Flashcards in Lecture 20- Conservation issues: Disease Deck (42):
Why is understanding disease important?
-diseases affect population size and conservation
When was tasmanian devil facial tumour disease(DFTD) first discovered and when did it get bad and why?
-sweeping epidemic by 2003
-by 2010 spread across 60% of Tas
-moving at about 7-20km/year
-7-20 km is really fast in a mammal population
-carnivores= tend to move in larger areas
-the biology of the animal affects the spreading speed
What is tasmanian devil facial tumour?
-cancer cell line, transmitted by bites
-100% mortality within 6 months of appearance of clinical lesions
-catastrophic decline of devil populations, a species that was widespread and of low conservation concern in the 1980s
-they bite each other when arguing over roadkills( food= very abundant)
How are they trying to save the Tasmanian devil?
-set up insurance populations= so they do not get infected
-breeding in captivity is difficult, need lot of space
-tas devil= keystone predator so very important for the ecosystem
What are population dynamics?
-processes that make populations rise or decline
-these are mortality, fecundity and migration
-disease may impact these
What are the ways of detecting a disease? (6)
1. Clinical evidence (when you can see the damage= unusual in the wild)
2. Abnormal blood profiles
3. Blood antibodies
4.-ve population growth (population decline)
5. Low fecundity
6. High mortality
What should you try to find out about a disease? (7)
1. Identify the cause= may be very difficult
2. Impact on individuals
3. Transmission (bite? air?)
6. Impact on population
7. Disease distribution
What is the rubware disease?
-disease, of brushtail possums, where they lose some of their fur
- not high mortality, can impact on energetic requirements= as there is less fur especially in cold environments
-then it may impact survival or fecundity
What do transmission rates change with?
1. with changing environmental conditions
2. with population density and health (density of animals impacts the transmission rates
-higher densities= usually higher transmission rates
-also when higher density= less nutrition so may be more susceptible to disease)
What is prevalence?
-number of diseased animals in a population at the time if survey e.g. 40% infertile from disease
What is incidence?
-changes in the number of diseased animals in a population with time
-over several years or so
-high incidence causes population decline
What are causes of diseases? (6)
3.Parasites (protists, worms, arthropods)
5.Nutritional (deficiencies, imbalances, toxins)
6.Captive related diseases
What does endemic disease mean?
-in population for a long time
-usually more benign so it doesn't lose all its hosts
What does epidemic disease mean?
-often recent and high impact
-population is naive
In what animals is the Pteropid or Australian Bat Lyssavirus found and what is it related to?
-related to classic rabies
-recorded in mega and micro bats
-more common in mega bats
-when it is in a group of bats, only some animals will suffer from it
What are the Australian Bat Lyssavirus (ABL) symptoms? (5)
1. Initially enters muscle via bite usually
2.Travels along nerves to CNS,and then nothing can save you once it is there
4. Meningitis= swelling of the brain
5.Paralysis,convulsions and death
What is the treatment for Australian Bat Lyssavirus?
-standard rabies vaccine
How is Australian Bat Lyssavirus transmitted?
What is the impact of the Australian Bat Lyssavirus on bat populations?
-probably not huge
-but impact on humans so it is researched
What causes chlamydia in koalas?
-widespread in vertebrates
Where do koalas get chlamydia? (4)
1. Eye- will scar and usually blind on one or both eyes, function normally with one eye(conjuctivitis)
2.Urinary tract-then they will die
3.Reproductive tract- won't die but female reproductive system is damaged and are infertile
4. Respiratory tract
How prevalent is chlamydia in koalas?
-85-90% of adults exposed (surveyed for antibodies in blood)
-widespread: Qld to Victoria
-transmission: venereal in Vic
What is chlamydia like in males?
- if in reproductive tract then usually asymptomatic
What is the impact of chlamydia on koala populations?
-female fertility in infected population= 10-55%
-in uninfected population= 60-95%
-reduced fertility= lower population growth
-chlamydial infection alone is not a threat to the population
-in combination with climate change and increased mortality can wipe out populations
What is a parasite?
-dependent on host
-parasites environment is another organisms
-cause some harm
-may have multiple hosts in life cycle
What is Coccidia?
-in orphaned marsupials
-common in feral cats that then infect others
What is Giardia?
-in vertebrate intestine
-common in marsupials (Tas and Vic)
-transmission: contaminated water or food
-get diarrhea and vomiting
What are the Cestoda?
=2 hosts in life cycle
--but hypatid tapeworm: in kangaroos, they are the secondary hosts, originally from sheep, very bad, impacts the kangaroos
What are the Digenia (flukes)
-in liver, feed on blood, damage host tissue
-debilitating to animals as makes them more susceptible to predators etc.
What are the nematoda?
-occasionally damage host gut tissue but many species are benign
-they live in the gut, but do not attach to the wall of the gut
What arthropods cause diseases in animals? (3)
What disease do ticks cause?
-Ixodes holocyclus, tick
-causes paralysis in marsupials
-can be very bad for small animals if they have many ticks on= cause anaemia
What disease do mites cause?
-mange in wombats
What disease do mosquitos cause?
-act as vectors
-transmit Ross River Virus to marsupials and other mammals including humans
Are there seasonal patterns in parasite loads on koalas?
-seasonality in ticks
What are koala ticks like?
-3 different life stages
-larval and nymph stages not on koalas, unclear what the intermediate host is
What is mange in wombats?
-cause by the mange mite
-loss of fur and eggs under skin, dry etc. these then split and get infected...death is likely if untreated
-can be treated
-differences in regional populations
-the distribution of wombats may be contracting if mange caused local extinction in small populations
What is an example of a fungal caused disease?
-platypus: abscesses (Tasmania), much more distributed than it used to be, , in 1995 only in one river system, now spreading
-frogs (Qld, NT, NSW): mortality
What is chytrid fungi responsible for?
-responsible for declines in some species of Australian frogs
-1st discovered 1993
-infects skin,= keratinised tissue of adults
What are the clinical signs of chytrid fungus?
-sloughing skin, depressed, sluggish, no appetite, fail to display avoidance behaviour
-causes mortality of adults including mass die offs in some frog species= population threat
What is the ecology of the chytrid fungus?
-distribution east coast + other sites
-spread mainly in water?
-greater impact in stream dwelling frogs
-greater impact at higher elevation