9706

• UCREFRP Catalog Number: 9706
• Author: Ward, D.L.
• Title: Removal and quantification of Asian tapeworm from bonytail chub using Praziquantel.
• USFW Year: 2007.
• USFW - Doc Type: North American Journal of Aquaculture
• Copyright Material: YES

COMMUNICA nON

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TABLE 3.-Number of bony tails found to contain at least one live Asian tapeworm after treatment and number of live
tapeworms detected per fish at I d and 30 d posttreatment. Bath treatments were conducted for 12 h or 24 h at four different
dosages of praziquantel.

Treatment 1 d after treatment 30 d after treatment
Dosage Duration Number of Tapeworms per Number of Tapeworms per
(mg/L) (h) infected fish individual fish infected fish individual fish
0.7 12 2 6, 2 2 1,2
0.7 24 5 1,7,5,2,4 2 1,2
1.5 12 2 1,6 0 0
1.5 24 0 0 0 0
6.0 12 4 7,7,4,6 1 1
6.0 24 0 0 0 0
6.0 (adult) 24 0 0 0 0
36.0 12 3 2, 1, 1 0 0
36.0 24 1 3 0 0

the dosage and time required to achieve 100% Asian
tapeworm removal.
The percentage of Asian tapeworms that established
in the new host was calculated by dividing the number
of tapeworms that were expelled during treatment plus
the number of tapeworms detected upon dissection by
the number of tapeworms initially inserted into each
fish. The difference in TL and weight (g) from the
beginning of the study to the end of the study was
compared with two-sample (-tests for fish exposed to
the highest concentration of praziquantel (36.0 mg/L)
compared with controls.

R,esults and Discussion

No treatment or control bony tails died at any of the
praziquantel concentrations used in laboratory tests. No
fish showed signs of stress or loss of equilibrium
during treatment. At 1 month posttreatment, there were
no significant differences in TL (two sample (-test: l' >
0.82) or weight (1' > 0.29) for fish exposed to 36.0 mg/
L praziquantel when compared with control fish. Initial
sizes of fish in the treatment and control groups did not
differ (1' > 0.44). This indicates that a 24-h exposure
of up to 36.0 mglL praziquantel did not have impacts
on growth of bony tails during this time period. The
percentage of Asian tapeworms that were successfully
transferred from red shiners into bony tails was highly
variable, ranging from 2% to 63% (Table 2). Success in
transferring live adult Asian tapeworms from red
shiners into bony tails indicates that transmission of
Asian tapeworms from one fish to another as a result of
predation probably occurs in natural systems.
Commonly used low dosages of praziquantel (0.7
mglL) are inadequate to remove 100% of Asian
tapeworms from bony tails. Although Asian tapeworms
are removed at these dosages, some survive treatment
within the host C[able 3). A praziquantel treatment of
1.5 mg/L or higher for 24 h was effective at removing

100% of Asian tapeworms. A 12-h treatment at 36.0
mglL was also effective at removing all Asian
tapeworms, but treatments of 12 h at 6.0 mg/L and
24 h at 0.7 mg/L were not (Table 3). At the highest
dose of 36.0 mglL, bony tails were found to harbor live
Asian tapeworms at both 1-d posttreatment in the 12-h
and 24-h but not after 30 d (Table 3). This indicates
that not all Asian tapeworms are killed and evacuated
from the host fish within 24 h. Although Asian
tapeworms may die later as a result of praziquantel
treatment, any unhatched eggs are still viable (J. Kline,
University of Arizona, personal communication). To
prevent transfer of viable Asian tapewbrm eggs into
new environments, fish should not be transported after
treatment until sufficient time has elapsed for all
tapeworms to be expelled. This can take more than 48
h (Mitchell 2004) and is probably dependent on
evacuation rate, which can vary with water temperature
(Specziar 2002).
At 36.0 mglL, one bony tail still had three live Asian
tapeworms after a 24-h treatment (Table 3). This
indicates that, even at high doses, a single praziquantel
bath treatment may not be 100% effective, indicating
more than one treatment is necessary (Sanmartin Duran
et al. 1989). The bony tails used in these experiments
had relatively low rates of Asian tapeworm infestation.
This could result in treatments appearing more
effective than they would be in fish with high Asian
tapeworm loads. Fish density, Asian tapeworm density,
and infestation rate are all factors that can lower
praziquantel treatment efficacy (Mitchell 2004). These
factors indicate the need for caution when using
praziquantel to remove Asian tapeworms. Praziquantel
bath treatments can effectively and safely remove
100% of Asian tapeworms from bony tails if dosages
and treatment durations are adequate; however, in some
cases, repeated treatments may be necessary to ensure