Upload
danganh
View
216
Download
0
Embed Size (px)
Citation preview
Global movement of pathogens
linked to free-ranging and captive wildlife
Howard PharoAnimals Risk Analysis
Global movement?• Wild animals move – with their pathogens• Locally, usually within environmental limits
• Might be across international borders • Migration over long distances = global• Human-mediated
– Translocations into the wild are rare– Mostly movement of pet or zoo animals
• Pathogens emerge & spread – often without clear cause
• How good is our current knowledge?– Surveillance gaps
• Role for risk analysis
Classical swine fever in European wild boar• Outbreaks are self limiting in most wild boar populations• But the virus may circulate for years in others• Recognised as a reservoir and possible source of
infection for domestic pigs– Considered source of ~ 100 outbreaks in Germany
1993-2002 • Considerable surveillance investment in the EU
– Database development• Mapping• Spatial modelling
Rabies in Europe
• Predominantly sylvatic– Wildlife account for 80% of cases
(WHO)– Red fox (Vulpes vulpes) 80% of
these– Raccoon dog in Eastern Europe
• Oral vaccine developed 25 yrs ago– Highly effective– Aerial distribution– Many European countries now
free
Rabies in Northern Italy• October 2008 – fox rabies reappears in NE Italy after 13 yrs
absence• 2009 – a number of oral vaccination campaigns• Further spread Westward
– To Veneto region• Recording of GPS data
– culled/dead foxes • Analysis of clustering
Slide courtesy of Paulo Mulatti
Istituto Zooprofilattico Sperimentale delle Venezie
• Upper altitude limit for baiting increased to 2300 m
White nose syndrome
Discovered in a single New York cave in February 2006
Spread South & West
More than a million hibernating bats of nine species have been killed by the disease in 14 states
Geomyces destructansProbably spread by spores on bats themselves
Present in Europe without disease; co-evolution?
Pteropid fruit bats - Flying foxes• Hendra (Queensland 1994) – bats – horses – humans
– 13 outbreaks in horses, 4 spread to humans• Bat lyssavirus (Australia 1996)
– 7th member of the lyssavirus genus – 2 human deaths
• Nipah (Malaysia 1999) – bats – pigs & humans – 105 human deaths, 1 million pigs culled
Is this global movement or the inevitable result of man encroaching further on previously undisturbed environments?
Pilchard mortalitiesAustralia & New Zealand 1995
Slide courtesy of Richard Whittington, University of Sydney
Huge losses – up to 60% in some populations
WESTERN
AUSTRALIA
NORTHERN
TERRITORY
SOUTH
AUSTRALIA
QUEENSLAND
NEW SOUTH
WALES
VICTORIA
TASMANIA
22 March20 April3 May
6 May
30 May
31 April2 May
5 May10 May12 May
15 May19 May
24 May30 May
2 June3 June5 June
Pilchard deaths 1995
16.06 Hauraki Gulf
20.06 Bay of Islands15.07
29.08
17.09 Wellington Harbour
19.06 Firth of Thames
05.09
03.07
3000 km
NNinety Mile
Beach
Southern bluefin tunaSea cage aquaculture
-fed imported frozen pilchards
Slide courtesy of Richard Whittington, University of Sydney
Herpes virus observed by EM
No culture systems
30 km /d, against current
Newly emerged latent virus?Exotic introduction into a naïve population?
West Nile virus• Flavivirus – same group as JE• 1937 Uganda• Africa, E Europe, W Asia, Mid East• Corvidae family (crows, jays, magpies) • 1999 outbreak New York City
– Infected mosquitos on aircraft or ships?– Viraemic human?– Infected birds most likely
• Spread in the US was probably by seasonal migrations of birds
• 1999-2000 spread along Atlantic seaboard• 2000-2002 rapid spread westward – 47 states
affected by 2008
Avian influenza and migratory waterbirds• Ducks – USA - 1970s
– Dabbling ducks positive (esp Mallards) )– LP virus in faeces of up to 60% ducks
• 1mg faeces contains infectious dose• Migrate south for winter• Stopover at ponds on poultry farms • Contamination of water supply• LP virus mutates to HP after introduction into
poultry• But duck migrations do not cross
the equator
Most outbreaks involve humans• US live bird markets• Asia - interface b/t domestic & wild ducks• Wild bird reservoir of HPAI unlikely• Intensive broiler production has become
the new focus in Asia – density of farming
• H5N1 probably endemic in much of Asia
• Biosecurity is the key– Implementation
challenges
Flubird - Database on Influenza viruses in migratory birds in Europe Slide courtesy of Christoph Staubach
Friedrich Loeffler Institut, Germany
Geographic distribution of samplesSlide courtesy of Christoph StaubachFriedrich Loeffler Institut, Germany
NZ migratory shorebirds
• Bar tailed godwit (Limosa lapponica)– 100,000
• Red knot (Calidris canutus)– 70,000
• Ruddy ternstone (Arenaria interpres)– 5000
• Pacific golden plover (Pluvialis fulva)– 1200
• Red-knecked stint (Calidris ruficolis)– About 500
• A number of other sandpipers, curlews, whimbrel etc in low hundreds
Surveillance in NZ waterbirds• No evidence of any AI viruses in migratory waders• Duck surveys show a low prevalence of LPAI viruses• Where did these duck viruses come from?• Perhaps with the originally imported ducks
– British stock from Australia– Many introductions, from 1860s to about 1920
• Very little movement of ducks over the Tasman– Generally populations in both Australia and New
Zealand are sedentary• Conclusion: Risk from HPAI in migratory birds negligible
Not all animal movement is natural dispersal or migration
• Human-mediated animal movements pose risks• New Zealand example
– Endemic mammals only bats• First humans arrived ~ 1000 yrs ago
– Polynesian rat, dog• European colonisation 200 yrs ago
– Many species of animal introduced
200 years of introductions to New Zealand• Livestock
– sheep, cattle, pigs, horses, poultry)
• Wild animals (for hunting)– Deer (7 spp)– Thar– Chamois– Wallaby (5 spp)– Rabbit– Hare– Waterfowl (ducks, swans)
• Biocontrol agents– Hedgehog– Stoat, Ferret, Weasel
• Birds – 30 spp– mainly passerines– Parrots
• Mistakes– Rats, mice– Possums
• Pets– Cat, dog, cagebirds etc
Introduction of pathogens?• Most normal livestock pathogens were introduced• Numbers of wildlife introduced were generally low
compared to livestock• No wild canines introduced • Many introduced livestock became environmental pests
– Possum, goat, thar– Rabbit, hare
• Ferret, stoat, weasel
Avian malaria in New Zealand• Plasmodium relictum - 3 strains present
– 1 endemic (Polynesian strain)– 2 introduced (sparrows, blackbirds)
• Introduced to Hawaii from Europe 200 yrs ago– Key role in bird extinctions
• Few effects in New Zealand – colder climate limiting mosquito
density?• May be involved in some deaths of
saddlebacks and yellow-eyed penguins
PRRS emergence in Europe & USA• Disease emerged Nth America & Europe ~ 1990
– Arterivirus identified 1991• Seropositives back to 1979 in Canada, 1988 in E Germany • European & American genomes distinct
• 40% divergence• Most recent common ancestor of PRRS? - LDV of mice? • Hypothesis (Forsberg, 2005)
– Mutant LDV jumps species to wild boar (in Sachsen-Anhalt, ~1880)
– Infected wild boar imported Carolina 1912– Independent evolution for 70 years– From wild boar to pigs synchronously?
Pathogen spill-back in NZ – possums and bovine tuberculosis• 60-70 million possums by 1990s• Major vector for bovine TB by
1970s
Photos courtesy of Paul Livingstone, AHB
Other wildlife vectors of bovine TB• Ferrets in New Zealand
Photos courtesy of Paul Livingstone, AHB
Other wildlife vectors of bovine TB• Ferrets in New Zealand• Badgers in UK• Feral buffalo in Australia
Photos courtesy of Graham Wilson
Hydatids – Echinococcus spp• New Zealand and Tasmania
– No wild or feral canids– Dog-sheep cycle – Eradication achieved by dog registration
and anthelminthic treatment
Echinococcus granulosis - Australia• Highly susceptible wildlife hosts• Definitive hosts
– Dingos– dog-dingo crosses– foxes
• Intermediate– Marsupials – Wild boar
• Eradication not feasible
Photos courtesy of David Jenkins
Echinococcus multilocularis in Germany • Endemic in wildlife ; fox – mouse cycle• Brandenberg, Germany
– GPS records for 6000 foxes shot 1995-2001• Spatial modelling
– Identification of potential risk factors for infection in foxes
– Vegetation type– Wetness
Prediction map of the distribution of E. multilocularis(using a GEE model)
Notifications 2005-2009
#
###
# #
#
#
#
#
#
#
###
##
#
#### #
##
#####
#
# # ###
##
#
## # ##
###
##
###
###
##
##
# ## ###
##
#
#####
# #
#
####
#
#
#
### #### ##
# ###
# ##
##
#####
###
#
##
###
###
##########
##
####
#
##
####
#
#
#
# ##
#
####
# ##
#
##
#
##
##
# #
##
#
# ##
#
#
##
#
#
###
###
## #
#
#
# #
#
##
##
######
##
##
###
#
##
##
#
##
#
##
#####
### ###### #
##
##
###
###
###
###
###
## #
# ##
## #
###
##
###
##
#
### ##
###
#####
# ##
##
##
#### # ####
#
##### ##
##
#
#
#
#
#
## #
# #
##
#
#
##
#
##
#
###
##
#
##
#
#
######
#
#
#####
# ## ##
### #
##
############
###
## ##
##
#
#
###
###
## #
#
#
#
##
#
#
## #
#
##
# ### ###
## #
# ##
#
#
##
##
#
##
##
#
#Slide courtesy of Christoph StaubachFriedrich Loeffler Institut, Germany
Risk Analysis for captive wild animals
• Exotic wild animals prohibited – environmental risk assessment needed
• New Zealand’s history of pest animals– Possums, rabbits etc– Approval very rare
• Zoo animals for containment– Normal IRA process
Diversity of Zoo animal IRAs• Tasmanian devils• White rhinos• Primates• Marsupials & monotremes• Rodents• Sharks• Tapirs• Elephants• Pandas
Characteristics of zoo animal IRAs• Volume of trade likely to be very low• Source known (rarely considered from wild)• Benefits difficult to argue against
– Public interest– Conservation of international biodiversity– Cooperative breeding programmes
• Risks are potentially quite different– Analytical investment may be high
• Risks can be managed
Conclusions• Local movements of wild animals may be important for
some diseases• Long-distant migration important for LPAI but HPAI
develops after global movement• Role of movement for fish diseases not well
understood• Surveillance of wildlife expensive, data often scarce• Captive wildlife risks can be managed• Risk analysis can be applied in many situations to
guide decision-making