Mycotoxins (toxins produced by fungi) can readily contaminate agricultural produce during growth, processing, storage or transport. Many mycotoxins are poisonous and some are suspected carcinogens. In Vietnam, many of the higher-yielding maize and rice cultivars are harvested during the wet season, increasing the risk of fungal spread and possible mycotoxin contamination. As well as posing a direct health risk, mycotoxins can also cause indirect problems when contaminated feed is unwittingly given to livestock. In these cases, the toxins can accumulate in the flesh of the animal, being passed later to human consumers in a more concentrated form.
Pesticide contamination may also cause long-term human health problems, although concentrations in foodstuffs probably pose less of a risk than mycotoxins. However, because pesticides can be so highly poisonous, any misuse can cause immediate effects in farm workers as well as consumers. There may also be effects on other species. Increasingly, public attitudes towards pesticides mean that food for international sale must have very low pesticide levels. This requirement can have major economic ramifications.
Pesticides and mycotoxins are complex organic molecules that require sophisticated and expensive instruments and chemical techniques to detect them at very low concentrations. However, another way of detection involving the use of antibodies can also be accurate and sensitive but more portable. The tests commonly referred to as enzyme-linked immunosorbent assay (ELISA) are based on the use of mammalian antibodies. They could be incorporated into a kit rather than a large piece of hardware, but ELISA kits were thought too expensive for widespread use in developing countries. This project aimed to develop new ELISA kits for selected mycotoxins and key pesticides of concern in Vietnam. Experience in the development and use of these kits could lead to cheaper, in-country production.
The project's main aim was to quantify the incidence and severity of food contamination by fungal toxins and some pesticides - principally in Vietnam, but also in Australia. The project also sought to develop reliable new tests for contamination, which could be produced reasonably cheaply and used in both countries.
The project involved establishing priorities for significant contaminants from baseline surveys in Vietnam and Australia, extensive training activities related to development and application of ELISA in Vietnam and the establishment of a monitoring network for testing agricultural produce. The project started with a baseline study of the occurrence of mycotoxins and pesticides. Produce was sampled in Vietnam and Australia for analysis with existing technologies. The team then established a network in Vietnam based around existing provincial laboratories, to monitor mycotoxin and pesticide levels in various agricultural products.
Test kits employing the immunological ELISA techniques were developed, tested and calibrated, to improve detection of selected mycotoxins and pesticides. Vietnamese project staff members were trained in techniques of ELISA development and use. Finally, the team examine the potential for establishing ways of ameliorating mycotoxin and pesticide contamination of produce.
The project highlighted the landmark success in the effective transfer of analytical technology for cost-effective and rapid detection of mycotoxins and pesticides in various commercial food sources from Australia to Vietnam. The project's success can be gauged by the increased capability of both Australian and Vietnamese institutions and their personnel to deal with a wide range of food contamination problems and to meet new challenges into the future.
When the project commenced, the Vietnamese partner, the Southern Institute for Agricultural Engineering and Post-Harvest Technology (SIAEP) in Ho Chi Minh City had only limited experience with immunodiagnostic techniques. However, it had already demonstrated capability by preparing immunoafffinity columns for aflatoxin. SIAEP had also successfully modified for use in Vietnam the application of the acetylcholinesterase enzyme test developed in Taiwan for detecting organophosphates and carbamates in vegetables and fruits.
During the project SIAEP gained the following skills and training: 1) the ability to design and synthesise haptens (organic mimics of mycotoxins or pesticides) that could be conjugated to proteins or enzymes for antibody preparation or ELISA analysis; 2) the ability to purify antibodies and optimise assay for specificity and sensitivity; 3) the ability to format prototype ELISA kits, undertake stability testing and study their suitability for practical application; the ability to prepare and validate immunoaffinity columns.
The project's actual immunodiagnostic products and associated intellectual property included the following:
an ELISA to detect aflatoxin that is now routinely applied in feedmills in Southern Vietnam near Ho Chi Minh City; its use is expected to extend to other areas of Vietnam during 2005-6;
a cyclodiene pesticide test, mainly targeting contaminants endosulfan and heptachlor;
extraction methods that enable ELISA test users to overcome matrix effects in relation to the applicability of the tests, for monitoring pesticide residues in produce;
immunoaffinity columns for rapid isolation and concentration of aflatoxins, allowing subsequent quantitative ELISA or HPLC analysis of these contaminants;
a growing set of baseline data on aflatoxins and organochlorine insecticides using the developed tests, providing reference sets that will allow future improvements in food quality management to be assessed;
a test for Salmonella spp. in processed meat and fishery products for export certification.
In Australia, the project has allowed three institutions (University of Sydney, AgriFood Technology and CSIRO) to add to their expertise in this area relating to safety for food and feeds. It has also allowed the development of new immunodiagnostic tests in Australia, expanding the range of biotoxins that may be rapidly monitored in agricultural produce and in food. In addition, it has improved the capability of Australian personnel to deliver the immunodiagnostic technology needed in future to help guarantee the quality of Australian food and the Australian environment. These outcomes are highly consistent with national priorities for research.
The immediate impacts of the project are based on capacity building in technical expertise, better research facilities that lead to better research capabilities. Vietnam now has a better capacity to deal with the complex issues surrounding product quality and to meet international standards as it enters the World Trade Organisation. Australia has enhanced its capacity to maintain and further improve its own standards in this regard.
The project made a major contribution to an AusAID CARD project in Vietnam by undertaking a risk assessment for pesticides analysed by ELISA tests. This assessment also permitted the validation of these risk estimates. The CARD activity involved ground-breaking cooperation amongst four institutions in northern and southern Vietnam, to provide a valuable demonstration of local and international scientific goodwill.
Links:
[1] http://www.aciar.gov.au/country/Vietnam
[2] http://www.aciar.gov.au/programarea/Horticulture