Three Litopenaeus vannamei families, from a breeding program in Panama and with possible WSSV resistance,
were challenged per os with a reference isolate of White spot syndrome virus originally obtained from China
in 1995 (WSSV-CN95). These F8, F9 and F12 generation families were developed from founder stocks a decade
ago and were survivors of white spot disease. Juvenile shrimp used for WSSV challenge averaged
1.5 g, and they were stocked at 50 to 96 animals per tank into nine 1000 L fiberglass tanks containing artificial
seawater at 30 ppt salinity and 26 °C. Three of the 1000 L tanks were used as negative control tanks, with
one tank for each family. Six 1000 L tanks were used for challenging the three families with WSSV, with two
replicate tanks for each family. A positive control consisting of 20 “Kona” SPF reference line L. vannamei (average
weight 1.5 g)was included and challengedwithWSSV in a 90 L glass aquarium. The Kona stockwas fed the same
batch ofWSSV infected tissue as the three Panamanian families to confirminfectivity and to provide a basiswith
which to compare final survival. WSSV infected minced frozen shrimp tissue was fed at a rate of 5% of average
body weight one time on day 0. All tanks were equipped with air diffusers to provide sufficient aeration and
an acclimated crushed oyster shell internal recirculating biological filter. Each tank was covered with a plastic
sheet to contain aerosols and minimize water temperature fluctuations. The experimental tanks were checked
daily and moribund animalswere collected when observed and preserved in Davidson's AFA fixative.Mortalities
in the three Panamian families ceased at 17 days post challenge. Two survivors from each tank were preserved
for histology and five shrimp per tankwere individually tested by qPCR to determine theirWSSV status and viral
load. Survival at termination in the negative control families was 95%, 98% and 100%. Survival in the Kona line
WSSV positive control was 0% with all the Kona line shrimp dead by day 6 post infection. At termination on
day 17, survival of Panamanian selected families in theWSSV challenged groups was 23%, 57% and 26% for families
LP-1, LP-2 and LP-3, respectively. This is the first time in the scientific literature that significant resistance of
L. vannamei against WSSV under controlled conditions is reported.
© 2012 Elsevier B.V. All rights reserved.
Three Litopenaeus vannamei families, from a breeding program in Panama and with possible WSSV resistance,were challenged per os with a reference isolate of White spot syndrome virus originally obtained from Chinain 1995 (WSSV-CN95). These F8, F9 and F12 generation families were developed from founder stocks a decadeago and were survivors of white spot disease. Juvenile shrimp used for WSSV challenge averaged1.5 g, and they were stocked at 50 to 96 animals per tank into nine 1000 L fiberglass tanks containing artificialseawater at 30 ppt salinity and 26 °C. Three of the 1000 L tanks were used as negative control tanks, withone tank for each family. Six 1000 L tanks were used for challenging the three families with WSSV, with tworeplicate tanks for each family. A positive control consisting of 20 “Kona” SPF reference line L. vannamei (averageweight 1.5 g)was included and challengedwithWSSV in a 90 L glass aquarium. The Kona stockwas fed the samebatch ofWSSV infected tissue as the three Panamanian families to confirminfectivity and to provide a basiswithwhich to compare final survival. WSSV infected minced frozen shrimp tissue was fed at a rate of 5% of averagebody weight one time on day 0. All tanks were equipped with air diffusers to provide sufficient aeration andan acclimated crushed oyster shell internal recirculating biological filter. Each tank was covered with a plasticsheet to contain aerosols and minimize water temperature fluctuations. The experimental tanks were checkeddaily and moribund animalswere collected when observed and preserved in Davidson's AFA fixative.Mortalitiesin the three Panamian families ceased at 17 days post challenge. Two survivors from each tank were preservedfor histology and five shrimp per tankwere individually tested by qPCR to determine theirWSSV status and viralload. Survival at termination in the negative control families was 95%, 98% and 100%. Survival in the Kona lineWSSV positive control was 0% with all the Kona line shrimp dead by day 6 post infection. At termination onday 17, survival of Panamanian selected families in theWSSV challenged groups was 23%, 57% and 26% for familiesLP-1, LP-2 and LP-3, respectively. This is the first time in the scientific literature that significant resistance ofL. vannamei against WSSV under controlled conditions is reported.© 2012 Elsevier B.V. All rights reserved.
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