andy shinn parasites of fish and shrimp - fish vet...
TRANSCRIPT
Andy Shinn
Parasites of fish and shrimp
The eyelash mite (Demodex
folliculorum), or the
demodicid, lives harmlessly
in the eyelash follicles of
around 98% of us.
Examined 21,787 hosts
137,230 metazoan parasite species
Man561
6.3 parasite species per host
Sheep388
Dog377
Cow356
Duck342
Horse264
Fox217
Common carp 300Roach 222Bream 190Tuna 174
Nile tilapia 60Pangasius 16
Penaeus monodon 2
There are a lot of parasites out
there!
So how many parasites are there? 32,000 species of fish3,000 caridean species
Pre-harvest mortalities result from the complex interplay of broad range of factors, including:
Stock source / genotype Developmental defectsPredation /cannibalism Impaired nutritionPhysical damage Sub-optimal /hostile Disease environmental conditions
Economic losses, in addition to mortalities, can result from:
Impacts on growth / food conversionPost-harvest downgrading of productsFish escapesManagement decisions that impact on profitability
e.g. delayed decisions to treat, grade, harvestCosts of husbandry and management practices
e.g. fallowing, grading, vaccination, treatment etc
…. and parasites of course!
The frequent association of disease with other pre-disposing,such as poor water quality and the broad range of events thatmight stress farm populations, also means that untangling theimpacts of disease from those linked to other causes becomesvery difficult or near impossible.
So in many cases the economic impact of parasitic diseases can only be estimated. Their role in subsequent infections is equally difficult to estimate, i.e. through the action of parasites, they facilitate subsequent viral, bacterial and fungal infections.
Anisakid nematodes
90
80
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50
40
30
20
10
0
Glo
bal
aq
uac
ult
ure
pro
du
ctio
n(m
illio
ns
of
ton
s)Blue: Global production
Red: Asian production
Asian and global aquaculture has been consistently
increasing at 6.4% p.a. over the last 5 years and at 7.2%
since 2010.
90.4 M t
82.1 M t
92
90
88
86
84
82
80
Asi
a co
ntr
ibu
tio
n t
o g
lob
alaq
uac
ult
ure
pro
du
ctio
n (
%)
Asia, for the past 20+ years, accounts for over 90% of
global aquaculture production
90.78% in 2012
1980 1990 2000 2010Year
Blue: Global aquaculture production
Red: Asian aquaculture production
Data from FAO FishStatJ
Here we see the impact of certain
disease events on the Asian shrimp industry, as an example of one
industry, with estimates of the resultant losses.
Global (blue line) and Asia’s (red line) year-on-year growth presented as a percentage
Costs of shrimp disease
1. US$ 0.3 B: YHV and WSSV in Indonesia;2. US$ 30-40 M p.a.: YHV in Thailand;3. US$ 0.5 B: WSSV in China;4. US$ 100 M: WSSV, YHV and MBV in
Vietnam;5. Losses in Thailand due to WSSV and
THV rise from US$ 240 M to 650 M p.a.; 6. US$ 160 M p.a.: WSSV in Sri Lanka;7. US$ 25 M: WSSV in Malaysia;8. US$ 80 M: WSSV in India;9. US$ 0.4 B: All shrimp diseases;10. US$ 3 B : “EMS” in Thailand. Exports
down 32% year-on-year. The value has declined by 17% to US$ 1.16 B.
So what about the impacts of parasitic diseases?
These can be divided into two categories:
Unpredictable / sporadic
Predictable / regular
For both, there may be costs in treating and managing infections once established, but for predictable infections there will also be costs associated with prophylactic treatment / management.
Perennial costs, e.g. associated with the management and control of sea lice (Lepeophtheirus and Caligus), can be largely predicted throughout a production cycle as they pose a continuous threat to captive stocks of fish.
The life-cycle, timings and dynamics of the parasiteare well understood.
Parasite numbers are continuously monitored to ensure they do not cross threshold levels.
Sea lice can be controlled through the employment of an integrated pest management strategy involving the use of a broad range of management tools in addition to direct treatment interventions.
Photo © J. Bron
Sea lice control in Norway in 1996 was about US$ 33.4 M, by 2009 this was US$ 206 M. Over the same time period, Norwegian salmon production increased by 248% (298 TT to 738 TT) and yet, the price of salmon increased only 20% (US$ 3.08-3.71 kg-1).
As sea lice impose this consistent threat, infections can be predicted and factored into farm business plans and farm-level treatment strategies.
Over the same time, there have been sig. improvements in salmon welfare, and the number of sea lice-related mortalities and the number of fish downgraded as a consequence of sea lice damage has fallen dramatically. To achieve this, the basic costs of sea lice control have increased from 3·64% in 1996 of total production costs to 7·53% in 2008.
For many new or less-established industries (esp. those restricted to a smallnumber of production sites), the parasite threats may be largely unknown andemerging, and new infections can have a devastating impact. The impact andseverity of Paramoeba perurans (AGD) infections on the early Tasmanianproduction of rainbow trout serves as an appropriate example.
Image © C. Matthews
Of course, established industries can also be hit, e.g. an outbreak of AGD inScotland in 2011 resulted in the loss of 13,600 tons of Atlantic salmon worth anestimated US$ 81 M.
Image © C. Matthews
Kingfish, Seriola lalandi, SE AustraliaPhoto: I. Ernst / C. Chambers
Parasite Host Country Year US$ (M)Kudoa yasunagai Japanese amberjack Japan 2011 1.6Paramoeba perurans Atlantic salmon Tasmania 2001 5-10Uronema nigricans S. bluefin tuna Australia 2003 2.13
Benedenia seriolae Amberjacks Japan/Aus 2001-14 214Benedenia seriolae Amberjacks Australia 2010 3.7*Caligus chiastos & S. bluefin tuna Australia 2008 1.4Cardicola forsteriHeteraxine heterocerca Japanese amberjack Japan 1963 1Neobenedenia melleni Amberjacks Japan 2014 >200Neobenedenia melleni Cobia Taiwan 2001 1.8Neobenedenia melleni Cobia Taiwan 2003 0.9
If we consider some major parasite events on fishin Asia
And some on crustaceans ….
Parasite Host Country Year US$ (M)
Haplosporidian sp. Whiteleg shrimp Indonesia since 2007 >5
Hematodinium sp. Indo-Pac. sw. crab Guangdong 2005-08 11.6-12Scylla serrata Prov., China p.a.
National, China 2005-08 352 tot
Hematodinium sp. Swimming crab Shandong, China 2004-12 6.7-13 p.a.P. trituberculatus National, China 2004-12 31.6 p.a.
National, China 2004-12 285 tot
‘Cotton shrimp disease’ in cultured penaeid shrimp
uninfected
infected
microsporidian pathogen
500 nm
TEM: spore of Spraguea sp. from anglerfish Lophius spp.
Lamellar
polaroplast
Anchoring
disk
Polar
filament
Tangprasittipap et al. (2013)
Enterocytozoon hepatopenaei and others!
Enterocytozoon hepatopenaei (EHP)First described from Thailand in 2009 in farmed, giant tiger shrimp P.monodon and then later P. vannamei;Confined to the hepatopancreasFound in slow growing shrimp but statistically so?Does not cause mortality;Direct transmission from shrimp to shrimp by the oral route;
Can be tested for using specific primers in our labNon-destructive testing
Speak to Pikul
There are a number of concerns associated with the expansion of
global aquaculture:
.
Rio de Janeiro, Brazil
Global population is currently 7.17 B and expected to be 9.55 B (i.e.
33% increase) by 2050.
Expansion of global aquaculture within the coastal zone.
Human migration to the coast (53% of the US population reside in
17% of coastal land area). Population living in the coastal zone is
expected to increase by 24.4% by 2025.
Increased human activity and increased nutrient inputs in an era of
changing climatic conditions is likely to have further impacts on
water quality, aquaculture production and the prevalence and
severity of disease events.
A significant proportion of stock losses occur within the hatchery / nursery phasesof production and in many industries these are factored into and “accepted” aspart of normal operational practices.
A significant proportion of stock losses occur within the hatchery / nursery phasesof production and in many industries these are factored into and “accepted” aspart of normal operational practices.
Such fatalistic acceptance of their inevitability means that they are frequently underreported, hiding the severity and impact of certain parasites.
Zoothamnium duplicatuminfestation of cultured
horseshoe crabs(Limulus polyphemus)
Shinn et al. (2015)
Mortality of 40,0002nd/3rd instar larvae
(i.e. 96%)
10 20 30 40 50
25
20
15
10
5
0
Mill
ion
s
Weeks
Eggs Swim-up21 d postmonosex
1” postnursery
Survival metrics across one cluster of Oreochromis niloticus sites (n = 4)
Survival metrics across one cluster of Oreochromis niloticus sites (n = 4)
Eggs
14.85 M month-1
Hatch rate 77.5%
11.50 M month-1
s.e. = starting egg number
Swim-up
77.8% survival(60.85% of s.e.)
9.0 M month-1
21 d postmonosex
78.9% survival(48.0% of s.e.)7.1 M month-1
1” postnursery
83.3% survival(40.0% of s.e.)
5.9 M month-1
Economics of juvenile loss
Eggs toswim-up
Monosexto nursery
Swim-up tomonosex
2.47 M 1.91 M 1.19 M
0.1 THB 0.3 THB0.2 THB
Farm data suggests that approx. 20% of stockare lost to parasites
US$ 3075 US$ 3560 US$ 2950
So this collection of site are losing
US$ 9,585 month-1
Causes of juvenile loss
20%parasites
Viral, bacterial,
other
Parasitesfacilitating 2ndry
infections ??
In 2012, there was a total of 43.59 M tons of fish produced of which 4.506 M tons was tilapia
Photo © R. Meyer / FVG
Using our earlier estimates, we can calculate juveniles losses as:
Lower (US$ M) Upper (US$ M)Nursery 4.48 6.17Monosex 5.41 7.43Swim-up 4.75 6.53
Total loss 14.64 20.12 (global tilapiaindustry only)
If we assume an av. sale weight of between 0.4-0.5 kg fish-1
8.2 to 11.3 billion tilapia being sold each year
If adjust for a further est. loss of 10% loss between nursery and harvest then we can estimate 9.0 -12.4 billion post-nursery fish
If apply this across global fish production, then the cost of parasites on juvenile production is somewhere between US$ 141.63 - 194.64 M
If we consider global production:
tons (M) US$ (M)FW prod 37.76 62,270Mar+Brackish prod 5.83 25,231Total 43.59 87,501
Parasite losses can be estimated at US$ 1070 – 4570 M
… and losses in growout (US$ M), then we can consider:
1.0% 2.5% 5% Juvenile141.63-194.64 *
Total growout 875 2188 4375Total (lower) 1017 2329 4517
(upper) 1070 2382 4570
Again applying 20% loss due to parasites
So we can see parasites can be costly but how do we begin to address these parasite problems?
Disease surveillance
A system of periodic monitoring of fish health should be implemented.
This monitoring has three levels of observations:
Level 3 – Samples sent to Level 2 could, additionally, be analyzed by advanced diagnostic techniques molecular biology techniques, PCR, qPCR, etc, where appropriate and guided by the findings from Level 2. This level of health assessment should be undertaken in specialised laboratories.
Level 1 - Macroscopic examination of the fish and wet mount analysis of fresh tissues under a light microscope / stereoscope. This level of observation can be done at the farm on a weekly basis by trained technicians. If the observations at level 1 reveal some anomalies, then specimens should pass to Level 2.
Level 2- Histological analysis. Samples of fish showing anomalies showed be fixed in 10% neutral buffered formalin and sent for histological analysis. This technique is carried out in specialized laboratories.
Before embarking on a course of treatment, it is important to have a proper identification ofthe causative disease agent and a clear understanding of its life-cycle.
This process involves a thorough examination of a sample of infected hosts as well as consideration of data concerning the fish’s environment, in order to collect all the information necessary to make aclear diagnosis.
An inaccurate diagnosis can either lead to the true problem going undiagnosed and becoming worse or can lead to an inappropriate course of treatment being used.
“Know thy enemy and know yourself; in a hundred battles, you will never be defeated"(Sun Tzu, 496 BCE)
Images from internet
The management and control of parasitic infections in aquaculture are a constant challenge, highly complicated by:
the current limited availability of efficacious licensed products
the development of resistance (to certain anti-parasitic drugs)
requirement to consider environmental, water quality and host parameters
the constraints of economics
the requirement for aquaculture sustainability and environmental protection
Treatment considerations
Delivering the right dose
“The right dose of the right drug to the right patient at the right time”
Sidney Taurel, 2005 (former CEO of Eli Lilley)
Having made an appropriate identification and decided upon a treatment, itis imperative that the pathogen is exposed to the correct target dose.Overdosing, in addition to imposing unwarranted additional expense andincreasing potential environmental impacts, can lead to the loss of stock,particularly when using chemicals with narrow safety margins.
Images from internet
While parasite impact in aquaculture is considerable, efficacious options for intervention other than anti-parasitic drugs remain limited
Fallowing and liming
Single year class stocks Non-chemical interventions
Feed management/ organic loading
Removal of reservoirs of
disease
Proper biosecurity and disinfection
protocols
Which treatment strategy to use?“…. let your methods be regulated by the infinite variety of circumstances”
(Sun Tzu, 496 BCE)
Image from internet
Experience has shown that while there are some rules of thumb that can be applied to the
treatment of certain parasitic infections, it is vital that the particulars of each situation are carefully
considered before a course of treatment is recommended.
Such “particulars” might include a diagnostic evaluation of:the current health status of the population to be treated; the severity of the infection(s); the pathology induced;water quality;the size of the fish population; and,the environment to be treated.
Image from internet
All of these need to be considered how we treat, when we treat, and what we treat with
Use and control of medicines and chemicals.
Technicians should know and understand when, how and
where to use licensed chemicals and medicines.
Ideally these responsibilities should fall on the
veterinarian in charge of the Aquatic Health Plan.
FVG Asia wet lab in Chonburi
Challenge room
Nursery
Lab External tank area
FVGAL main site
FVGAL wet lab
Premises were acquired in November 2014Renovated throughout Dec 2014Facility includes a small labHatchery room currently housing 3 × 400 L tanksAn external area with 32 × 200 L tanksA challenge room that can accommodate 50 × 10 L tanks
Wet lab in mid-Dec
The first major trial is already running
Flexibility for bespoke design to meet individual experimental needs.
External temperature regulation using a double skinned insulated roof with recirculating sprinkler system.
Experienced staff / 24 hour cover.
Back-up generator and air blowers.
On site challenge work and disease testing using iiPCR for known pathogens.
Electronic instrumentation, DO meters, data loggers.
Microscope with image capture.
A range of trials can be conducted at the wet lab including:
Bacterium / viral challengeGrowth / feed trialsPalatabilityParasite culture and infectionTreatment chemotherapy trialsLC50 / toxicity trialsHistopathology
Parasitology
498
Freshwater study is in prep
Whiteleg shrimp on sale at a market in Chonburi
Thank you for your kind attention
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