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Application of Receptor Binding Assays for Mapping and Monitoring of Shellfish Toxins

Project Number: CHI/7/010


Objectives:

To develop and transfer robust application formats of a receptor binding assay (RBA) for the detection of paralytic shellfish toxins (saxitoxins) in shellfish and water samples in remote laboratories of regional health services and hospitals, and shellfish processor plants.


Background:

This project is a continuation of a Programme Reserve project CHI/7009.
One of the more serious and visible problems facing coastal waters relates to the phenomena known as harmful algal blooms, or HABs, commonly called "red tide". These blooms produce toxins that can accumulate in seafood products (predominantly shellfish and fish) that then pose a risk to human consumers. The effects on humans range from mild discomfort to long-term illnesses and even death from the poisoning syndromes. In the last 10 years, high levels of paralytic and diarrhetic shellfish poisoning (PSP and DSP) have been reported in southern Chile, resulting in the closure of some natural shellfish beds south of the country and costly monitoring programmes. As a consequence, most seafood-exporting countries have established mandatory screening programmes for PSP in toxins.
The mouse bioassay is a widely used screening method which measures the time to death after injection of seafood extract. Although the mouse bioassay has proven to be an effective and reliable tool, it has significant limitations. For example, the method cannot detect toxins at low concentrations, or in certain tissue types. Therefore, the availability of reliable high throughput methods of PSP (and DSP) detection is mandatory for: a) screening of large number of samples, b) early warning monitoring in affected areas, c) certification of leased aquaculture sites, d) clinical analysis of human and animal samples, and e) regulatory control. Since the vast majority of monitoring samples that are typically tested are negative, considerable cost savings could be realized if a rapid, accurate, and inexpensive assay could be used to pre-screen samples.
A key application of nuclear technologies that can circumvent the problems highlighted in the preceding paragraphs is RBA. Like the animal bioassay, RBA provides an estimate of the integrated toxic potency of a sample. It is highly sensitive and has very low detection that is nearly three orders of magnitude less than the current mouse bioassay thereby simplifying sample treatment. In addition, RBA can provide early warning information to both regulatory authorities and producers as it can detect subtoxic levels of PSP well before the mouse bioassay. In addition to higher throughput, RBA offers cost advantages per sample analyzed. The RBA for Paralytic Shellfish Toxins is a mature technique and was successfully applied in Chile in 1995-97 as part of a Shellfish Sanitation Programme to certify aquaculture sites. Through this project, the local capabilities for rapid assessment of saxitoxins will be developed and transferred to the laboratories of the Instituto de Salud Pública and of the three Regional Health Services located in Puerto Montt, Puerto Aysén and Punta Arenas.


National Commitment:

The Government has committed human resources and laboratory capabilities of the main counterpart institution, the Laboratory of Marine Toxins of the University of Chile as well as the Chilean Nuclear Energy Commission.


Agency Input:

The development of local capabilities for RBA will be supported through expert services and training programmes. This also includes the upgrade of laboratory facilities to enhance the development of capabilities for laboratory and field detection of toxin levels.


Performance Indicators:

Non-commercial production of radio-labelled saxitoxins.
Reports on analysis of results comparing RBA and live-mouse bioassay.
Increase in the number of trained staff on RBA.
Capabilities in local laboratories developed for RBA


Expected Results:

Rapid generation of results by RBA to warn regulators and producers on the toxic levels in shellfish.


Project Impact:

Restored domestic and international confidence in Chilean shellfish will enhance the country's economy, as well as the development of a national capability that allows rapid assessment of toxic levels.