SPF and SPR seed it's important in aquaculture

1. Principles of SPF and SPR
Presented by
R. Bharathi Rathinam

2. SPF
• SPF status is gained by specific management
conditions where pathogens are excluded from
the culturing facilities.
• This is a common strategy for domestication
programs.
• SPF animals are free of one or more specific
pathogens, but this health status does not refer
to their susceptibility to infection or disease.
• In addition to being SPF, animals may or may not
also be resistant or tolerant to the same or other
pathogens.

3. Non-SPF broodstock
• There are many problems involved with the use of non-SPF
broodstock.
• The first and foremost has already been discussed which is
the possibility of importing novel pathogenic viruses and
other diseases into new or clean areas. This has already been
seen in Asia with the introduction of P. vannamei into
Mainland China, Taiwan Province of China and Thailand.
• The problem here is that non-SPF shrimp tend to be cheaper
and more easily available (pond-reared broodstock in Asia
currently sell for US$8–10, while SPF broodstock from Hawaii
cost US$23–25 delivered) and are hence initially attractive,
but may have long-term negative consequences.

4. • In addition, without strict biosecurity and disinfection
protocols for treating non-SPF broodstock, eggs and
nauplius, any pathogens infecting the broodstock tend to
be passed to the larvae which increases the possibility of
serious disease problems during on-growing.
• Another problem is that it is extremely difficult to
ascertain whether the stocks bought in are really SPF or
not. Often competent testing facilities do not exist in
Asian countries and many unscrupulous dealers will sell
supposedly SPF stocks with false certificates to unwary
farmers.
• A final problem is that while SPF stocks are almost
certainly domesticated lines which have been selected
for growth and disease resistance over a long period,
non-SPF stocks may not have been selected and are of
often uncertain parentage. This makes their use as
founder populations for genetic selection and
domestication programmes undesirable.

5. INTRODUCTION
• The status of Specific Pathogen Free should
signify that the shrimp have passed through a
rigorous quarantine and disease screening
process that determined them to be free from
specified pathogens of concern to culturists.

6. • This characteristic means that countries or
regions which still do not have this species can be
reasonably sure that the importation of SPF
animals will not result in the introduction of the
specified pathogens for which the animal is
declared “free”.
• This does not, however, guarantee against the
animal being infected with unknown pathogens
or known pathogens which are not screened
against.

7. • Genuine SPF shrimp are those which are produced
from biosecure facilities, have been repeatedly
examined and found free of specified pathogens
using intensive surveillance protocols, and originate
from broodstock developed with strict founder
population development protocols.
• These founder populations are generated by
extensive quarantine procedures that result in SPF F1
generations derived from wild parents (Lotz, 1997).
Only when raised and held under these conditions
you can have true SPF stocks.

8. • Once the animals are removed from the SPF
production facilities, they should no longer be
referred to as SPF, even though they may
remain pathogen free. Once outside the SPF
facility, the shrimp may be designated as High
Health (HH) as they are now subject to a
greater risk of infection, but only if they are
placed into a well-established facility with a
history of disease surveillance and biosecurity
protocols.

9. • If the shrimp are put anywhere else, for example
into a non-biosecure maturation unit, hatchery or
farm, they can no longer be called SPF or HH as
they are now exposed to a high risk of infection.
• The primary goal of SPF facilities is to produce
strains of shrimp that are disease-free,
domesticated and genetically improved for
aquaculture. Example : P. vannamei and P.
stylirostris.

10. Drawback of SPF
• One potential drawback of SPF animals is that they are only
SPF for the specific diseases for which they have been
checked.
• Typically this will consist of the viral pathogens which are
known to cause major losses to the shrimp culture industry,
including WSSV, YHV, TSV, IHHNV, BPV and HPV as well as
microsporidians, haplosporidians, gregarines, nematodes
and cestodes.
• Despite this screening, new, hidden or “cryptic” viruses may
be present, but because they are as yet unrecognized, may
escape detection. Thus, it is believed that SPF shrimp shipped
from Hawaii resulted in the contamination of shrimp in Brazil
and Colombia with TSV (Brock et al., 1997). This was because,
at the time, TSV was not known to have a viral cause and
therefore went unchecked in SPF protocols.

11. • Additionally, new diseases may emerge from mutations
of previously non-pathogenic organisms - i.e. the highly
mutable RNA viruses.
• Hence, it remains a possibility that importation of SPF
shrimp may not rule out simultaneous importation of
pathogens. Another possibility is that if SPF shrimp are
stocked into facilities with high viral loads, substantial
mortality can result as they are not necessarily more
resistant to these diseases than non-SPF shrimp, and in
some cases, less so.
• They may thus be more suited to culture in biosecure
systems, which may explain the reliance of the big,
non-biosecure pond farms of Latin America on SPR,
rather than SPF shrimp.

12. • In any case, the use of SPF stocks is only one part of a
complete plan for minimizing disease risks in shrimp
culture. The development of SPF strains is really
designed to help ensure that PL stocked into grow-
out ponds are free of disease, one of, if not the most
serious source of contamination.
• Other areas of this strategy that must be
implemented include: strategies to ensure
broodstock, eggs, nauplius, larvae and juveniles
derived from SPF stock remain SPF such as:
• Farm biosecurity, early warning surveillance and
rapid response to disease outbreaks.

13. SPR
• Recent research work by some state and private
companies has focused efforts on the development of
SPF strains that are also resistant to specific pathogens
(SPF/SPR). This is a long process, and usually focused
on one pathogen at a time. Thus, although the
development of pathogen resistant strains is a long-
term goal of SPF breeding programmes, it is unlikely
that they will ever result in strains that are unaffected
by all disease organisms (Lotz, 1997).
• SPR shrimp usually result from a specific breeding
programme designed to increase resistance to a
particular virus.
• SPR strains of shrimp, however, do not necessarily have
to be SPF

14. SPR Production
• This is accomplished by challenging sub-lots of
shrimp families to a particular pathogen (or
combination of pathogens) and then selecting the
most resistant families as broodstock for the next
generation

15. • These strains are typically resistant to only one
pathogen, currently largely either TSV or IHHNV, but
some work has indicated that strains with multiple
resistance to TSV and WSSV (at up to 25 percent
survival to challenge tests) may be possible (Jim
Wyban, per. com.).
• SPR status for a particular pathogen is not lost due to
management practices, although it can be lost in
subsequent generations through poor animal-
breeding and selection strategies.

16. Hawaii history SPR
• A selective breeding programme for P. vannamei was initiated
in 1995 in the Oceanic Institute in Hawaii.
• Original work was based on a selection index equally for
growth and TSV resistance (the major disease problem in the
Americas at that time).
• Confirmation that growth and survival (to TSV challenge)
responded well to selection was obtained, but there appeared
to be a negative genetic correlation between these traits.
• However, selected shrimp (Growth and TSV resistant) were 5
percent smaller than control shrimp, revealing a negative
genetic correlation between mean family growth and mean
family survival to a TSV challenge.

17. • This negative correlation between growth and disease
resistance must therefore be taken into account when
developing breeding plans for these shrimp.
Hawaii SPR
• Using the Hawaii specific pathogen resistance (SPR)
healthy P. Vannamei to increase the possibility of a more
successful production.
• This SPR Vannamei not only show negative for
TSV,WSSV,BPV,IHHNV,YHV and HPV, but also get 81~88%
high survival rate under the TSV attack, conducted by the
University of Arizona and Oceanic Institute.
• Like other animal, the virus-resistant ability of SPR
healthy Vannamei may decrease after three to four
generations. From time to time, it is needed to introduce
new parent prawn to keep the virus-ability standard.

18. SPT
• The vast majority of SPR being sold are SPT.
• They are tolerant to the specific pathogen at a certain level of
exposure to the particular pathogen.
• SPT animals either do not develop the disease, or it has a
lower impact than in normal animals, when they are infected
with the specific pathogen for which tolerant status is
conferred.
• Tolerance is a quantitative characteristic. For example, there
might be different degrees of tolerance to the pathogen.
• If SPT animals have not been exposed to pathogens, they can
also have SPF status, but being susceptible to infection, they
cannot be SPR for that same pathogen. Unless these animals
are also SPF, they are potential carriers of pathogens and
therefore present a risk to spread diseases.