Environmental Engineering Reference
In-Depth Information
pathogen have increased, as well as broadened the geographical distribution. Cases have
also been reported in FW recirculation systems as well as in open-flow and estuary. The
disease shows high prevalence increasing from 19% in 2006 to 31.96% of total diagnoses in
the year 2007 (Sernapesca, 2008a). In 2008, the monthly mortality average associated with
IPNv in Coho Salmon was below 0.01%, in Atlantic salmon 0.01% and in rainbow trout
0.03% (Intesal, 2009). In 1999, ISA virus (ISAv) was first detected in SW farmed Coho salmon
in Chile (Kibenge et al., 2001). In contrast to the classical presentation of ISAv in Atlantic
salmon, the presence of ISAv in Chile was associated with a clinical condition characterized
by jaundice in Coho salmon (Smith et al., 2002, 2006) and the virus isolation was
sporadically and unsuccessful. During the winter of 2007, unexplained mortalities occurred
in market-size Atlantic salmon in a grow-out site located in Chiloé (Sernapesca, 2008b). The
outbreak was caused by a virulent variant of ISAv different from common European ISAv
isolates. The clinical signs and lesions were consistent with the classical descriptions of the
disease in marine farmed Atlantic salmon in Europe and North America (Godoy et al.,
2008). The re-emergence of ISAv in Chile has resulted in one of the largest ISAv epidemics
reported in the world (Mardones et al., 2009).
Upon analyzing the susceptibility of Chilean farmed salmon to the mentioned diseases,
there are important differences in pathogen prevalence as well as associated losses between
the three cultivated species. In terms of mortality rates, the Coho salmon is mainly affected
by piscirickettsiosis during SW phase, and secondly by BKD, especially in the southern
areas. The Atlantic salmon is affected mainly by IPN in FW and when first transferred to
SW. After being established in SW the most relevant pathogen is ISAv, since it causes
significant mortalities among infected groups (Subpesca, 2010) and secondly by
piscirickettsiosis. In some cases, related to specific environmental conditions in certain
geographic areas, there are important losses of Atlantic salmon due to
Caligus
sp. and
atypical
A. salmonicida
and other bacterial diseases. The impact of diseases may significantly
differ among farming companies, cultured species, farm sites and geographic locations.
3.2 Commercial vaccines in Chile
Nowadays 44 commercial vaccine formulations have been authorized for the use in
salmonids in Chile (Servicio Agrícola y Ganadero, SAG, 2011). In Chile, the use of vaccines
began in the early 1980´s, with vaccines against vibriosis (Bravo & Midtlyng, 2007). Then,
after the occurrence of ERM in 1992, vaccines to protect Atlantic salmon came into use
(Bravo, 1993). In 2010 a total of 6,4 million doses were used more than 6 times compared to
the doses used in 2009 (Sernapesca, 2011c, 2011d). Vaccines against IPNv in Chile were
rapidly available, because they were already in use in salmon farming countries. Since 2002,
bivalent vaccines came into the market and were used to provide protection against IPNv
and atypical furunculosis or IPNv and SRS. Currently, bivalent, trivalent, quadruple and
quintuple formulations are available from international and local laboratories (SAG, 2011).
More than 10 years have passed since the first vaccine against
P. salmonis
was launched in
the Chilean market. The vaccines against this bacterium apparently have no effect on
reducing mortalities (Bravo et al., 2005). As of today, 26 vaccines against
P. salmonis
, both
monovalent and polyvalent, have been registered in Chile (SAG, 2011), and amount of doses
have increased since 2005 (Table 4). Spite the use of vaccines, piscirickettsiosis still remains a
major sanitary threat for salmon farming in Chile. After the crisis caused by ISA virus, the
Search WWH ::
Custom Search