Shrimp were observed for clinical signs
of microsporidian infection from the feeding trays
daily during the first 40 days after stocking the
PL. At day 45, shrimp were first sampled by cast
net and then were sampled every 15 days until
harvested. At each sampling event, at least 600
shrimp were randomly sampled from three
different areas in the pond to determine the
prevalence of microsporidian infection. Shrimp
specimens were classified into three groups: (a)
microsporidian infection in the hepatopancreas and
abdominal striated muscles, (b) muscle infection
only and (c) uninfected healthy shrimp (Figure 1).
Shrimp from the three groups were weighed and
recorded. After shrimp were harvested at day 120,
data of shrimp weights from the three groups at
each sampling time were statistically compared
using Duncan’s multiple range test (Steel and
Torrie, 1980).