Goal: Estimating accumulated tetrodotoxin in some aquacultural species fed by Vietnamese toxic puffers with the aim of awareness on potential human poisoning

Objectives:

Obj. 1: Experiment of rearing the snail Babylonia areolata and white leg shrimp Litopenaeus vannamei fed by marine toxic puffer:

• Experiment of rearing for adaptation in aquacultural area, Institute of Oceanography with 2 tested species
• Estimating of suitable toxic food for tested species (no mortality and normal growth)
• Rearing experiment for toxin accummulation in B. areolata and L. vannamei

Obj. 2: Verify TTX accummulated in rearing specimens fed by toxic puffer (control fed by non toxic fish):

• Sampling: 30 specimens/ tank (both control and experiment)/month in each species.
• Extract TTX and analyse TTX individually by HPLC, convert into toxicity (MU/g) accorrding to Nakamura and Yasumoto (1985).
• Verify TTX accommulated in each species after experiment.

Obj. 3: Estimate TTX in B. areolata and L. vanamei collected from local aquacultural farms which suspected to fed by puffers:

• Sampling: 30 specimens/farm
• Extract TTX and analyse TTX individually by HPLC, convert into toxicity (MU/g) accorrding to Nakamura and Yasumoto (1985).
• Verify TTX accommulated in each species after experiment.

Obj. 4: Awareness on potential human poisoning by consumption of TTX contaminated aquacultural species

Theoretical results:

1. Determine TTX in Babylonia areolata and Litopenaeus vanamei collected from local aquacultural farms which suspected to fed by toxic puffers

No TTX was detected in almost of all specimens of B. areolata collected from Nha Trang and Van Ninh. With max value was quite low (0,4 MU/g in Nha Trang and 1,3 MU/g in Van Ninh), it is considered as no TTX contamination in sampling time. In contrast, white leg shrimp showed certain level of contaminated TTX. Northerworlly, 4 out of 28 B. areolata specimens (10%) from Nha Trang exhibited toxicity higher than 10 MU/g (safety limit for TTX).

2. Estimating of suitable TTX amount in the food for rearing species

The lowest toxicity from puffer pellet was in the 1st month of the experiment (0,46 MU/g for B. areolata and 0,63 MU/g for L. vanamei), which almost equal or higher tan level of 0,5 MU/g in Noguchi’s (2004) experiment. From that, it is clear that suppliment toxicity from food in our experiment is enough to cause TTX accummulation for tested species.

During whole experiment, no death found in both B. areolata and L. vanamei, it is showed that amount of toxin in food pellet is lower than TTX resistant level of tested animals. Therefore, liver/muscle of T. gloerfelti is suitable for study aim of evaluation of toxin accummulation.

3. Accummulated TTX in perfume snail Babylonia areolata and white leg shrimp Litopenaeus vanamei fed by toxic puffer

There was increasing of toxicity significantly in B. areolata by rearing time (month). After 2 months of rearing condition, toxicity excessed safety limit for TTX (10 MU/g; Kodama and Sato, 2005). When experiment ended (after 5 months), toxicity in B. areolata showed avarage toxicity as 23,78 ± 29,77 MU/g, 2,3 higher than value of 10 MU/g. Similar to B. areolata, there is well corellation between toxicity in L. vanamei and rearing time, means that with the supplimental toxin from food, more time of rearing, more toxicity accummulated in this species. Although accummulated slower than B. areolata, after 3 months in rearing condition, toxicity in L. vanamei was in the safety limit value and beyoned (1,5 time) after 4 months.

Northyworlly, a ratio of specimens exhibited toxicity higher than safety limit for TTX is quite high (column 5 - table 8 và column 5 - table 9). After one month of rearing, 25% of B. areolata specimens and 23,3% of L. vanamei were recored with toxicity higher than level of 10 MU/g. Especially, after 2 months of rearing, some specimens exhibited very high toxicity (> 100 MU/g). Acorrding to Nakamura and Yasumoto (1985)’s calculation, if sample contained such amount of toxin, only 80-100g of soft tissue may cause poisoning and death for human. After 4 rearing months, 57,1% B. areolata specimens and 33,3% L. vanamei specimens contained TTX > 10 MU/g.

4. Aareness on potential human poisoning by consumption of TTX contaminated aquacultural species

From this studied result, it is considered that using toxic puffer for food of aquacultural species is not suitable, not safe for human consumption. It is neccesary to have action from governmental offices about awareness of using toxic puffers in aquacultural food without scientific evidence.

Scientific data from this study indicated that using toxic puffers as aquacultural food is dangerous for human consumption.

Scientific papers in referred journals (list):

• Toxicity of tetrodotoxin in a white legs shrimp Litopenaeus vanamei (Boone, 1931) feed by toxic puffer. Journal of Science and Technology. 2013 (accepted).
• Toxicity of tetrodotoxin in Babylonia areolata feed by toxic puffer. Proceedings of “Bien Dong 2012” conference (accepted).

The Ministry of Health, the Ministry of Agriculture and Rural Development, Universities, local administration in coastal provinces, Fishermen communities.