EVALUATION OF A SYSTEMS-BASED APPROACH TO CONTROLLING BLOWFLY INFESTATION OF TRADITIONALLY PROCESSED FISH AT SMALL-SCALE PROCESSING SITES by J.R. Esser, A.T. Marriott and V. Salagrama NR International, United Kingdom Abstract Blowfly infestation is a complex process. Levels of infestation can be influenced by a number of factors including processing techniques, fish species being processed, season, location and standards of hygiene. The situation is further complicated by fish processing sites being highly variable, both in terms of types of fish and methods of processing. No two processing sites are the same, which means that a blowfly control measure that is effective at one site may be inappropriate at another. Successful blowfly control therefore depends upon the use of control measures that are appropriate to the particular circumstances at each processing site. Recent research suggests that if control measures are to succeed they must be based on a detailed understanding of infestation modes, external factors, variations in processing techniques and the socio-economic context within which the processing takes place. The most effective and sustainable way to control blowfly infestation of traditionally cured fish is through applying a systematic approach based on Hazard Analysis Critical Control Point (HACCP) principles. This is because the timing, mode and causes of the infestation vary considerably between processing sites and can even alter at a particular site if the processing practices or the external conditions change. The best way to control the infestation will also vary, according to the particular circumstances of the infestation. Approaching the problem of blowfly control systematically allows a control measure to be chosen that is appropriate to the infestation problem at any given site. The systems-based approach to blowfly control has recently been evaluated during community-based field trials conducted at small-scale fish processing sites located along the eastern coast of India. This research has clearly demonstrated that the systems-based strategy offers a safe, efficient and cost-effective remedy to the problem of blowfly infestation at small-scale traditional fish processing sites. The outputs of this research and potential for transferring the systems-based approach to controlling blowfly infestation at small-scale fish processing sites in Africa are discussed in this paper. Résumé L’infestation par les mouches constitue un processus complexe. Les niveaux d’infestation peuvent être provoqués par des facteurs différents tels que les techniques de transformation, les espèces de poisson transformé, la saison, la localité et les conditions d’hygiène. La situation se complique davantage à cause de la haute variabilité des sites de transformation du poisson, soit en termes de types de poisson que de méthodes de transformation. Il n’existe pas deux sites de transformation qui soient similaires, cela signifiant que les mesures de maîtrise de la mouche qui soient efficaces dans un site, se révèlent inappropriées dans un autre. Une maîtrise réussie donc de la mouche dépend de l’emploi de mesures de contrôle appropriées aux conditions particulières de chaque site de transformation. La recherche récente nous révèle que si les mesures de maîtrise réussissent, elles sont basées sur une compréhension des modalités d’infestation, des facteurs externes, des variations des techniques de transformation, comme du contexte dans lequel la transformation a eu lieu. La façon plus efficace et soutenable pour maîtriser l’infestation des mouches du poisson traité traditionnellement se montre l’application d’une approche systémique basée sur les principes de système d’analyse des risques-maîtrise des points critiques (HACCP). Cela à cause des variations considérables de la durée, des modalités, des raisons de l’infestation, qui sont très aléatoires entre les différents sites de transformation, et peuvent changer dans le même site avec les changements des pratiques de transformation et des conditions extérieures. La meilleure façon de maîtriser l’infestation, présente aussi des différences, selon les circonstances particulières de l’infestation. Une approche systématique du problème de maîtrise de la mouche nous permet d’appliquer des mesures de maîtrise qui soient appropriées au problème particulier d’infestation dans un site donné. 121 L’approche basée sur le système pour la maîtrise de la mouche a récemment été évaluée pendant des essais de terrain au niveau des communautés, effectués dans des sites de transformation à petite échelle situés le long des côtes orientales de l’Inde. Cette recherche a clairement montré comme la stratégie basée sur les systèmes se révèle un remède sûr, efficace et convenable, pour résoudre le problème dû à l’infestation des mouches dans les sites de transformation traditionnelle du poisson à petite échelle. Le résultat de cette recherche et le potentiel pour transférer l’approche de système basé sur le contrôle de l’infestation des mouches dans les sites de transformation de poisson à petite échelle en Afrique sont discutés dans ce rapport. 1. INTRODUCTION Traditionally processed fish is a nutritionally and economically important commodity in many tropical, developing countries. Throughout processing and early storage, fish are exposed to infestation by blowflies (Diptera: Calliphoridae). This is a significant cause of post-harvest losses in the traditional fish processing industry, exacerbated by the basic, unhygienic conditions under which much of the fish is processed, particularly at the small-scale level. While few detailed quantitative studies of insect related losses of cured fish have been carried out, losses of 25 percent are thought to be common and, in the authors’ experience, losses in excess of 90 percent can occur in situations where no preventative measures are used. Such frequent and extensive losses cannot be sustained and therefore some processors have responded to the problem by applying unsuitable, toxic household and agricultural insecticides directly to their fish, jeopardizing not only their own health, but also the health of fish consumers. A range of methods of infestation control have been developed and promoted for use at fish processing sites over the past 15–20 years. These include, among others, the use of solar driers, mesh screens erected over drying racks to prevent gravid females from gaining access to the fish, improved salting methods to render the fish unacceptable to ovipositing blowflies and feeding larvae, and the application of approved insecticides. Despite extensive research and promotion of remedial techniques, uptake of recommended control measures by fish processors has been poor and therefore insect infestation of traditionally processed fish remains a major cause of losses. The apparent failure to successfully promote recommended control measures is generally attributed to two factors. The first is socio-economic, whereby implementation of the suggested measures may be too costly or culturally unacceptable. The second is poor extension of research findings to the fish processors. While the first is difficult to overcome, the second can be improved with good training of extension workers and better incentives. The success of the control measures must, however, also depend upon a detailed understanding of the various modes of infestation, and the influence of external factors – such as climatic variations, fish species processed, processing practices followed and insect species present – on infestation patterns and levels. It has become apparent that a reduction in insect infestation of traditionally processed fish may only be achieved by developing a systematic and holistic control strategy that is adaptable to the many different fish processing systems and takes into account limiting socio-economic factors. The systems-based control strategy outlined in this paper was a principal output of the Department for International Development (DFID) funded project “Adaptation of a Systems-based Approach to Insect Control, R7971”. The design of the strategy was fully informed by the findings of a comprehensive review of insect infestation (Johnson and Esser, 2000), which was also an output of the project. The review indicated that effective and sustainable control of infestation is only likely to be achieved if a more systematic approach, which fully takes into account infestation modes, external factors and variations in processing parameters, is used. The idea of a systematic approach is to study when, how and why the fish have become infested and then to select an appropriate method of controlling the infestation based upon these findings. The 122 strategy is applied by conducting an on-site infestation audit that follows the five simple steps shown in Figure 1. 1.1 Determine the method of processing, the processing steps followed and their sequence A systematic approach involves studying exactly when the fish are becoming infested and what processing risk factors may be influencing the infestation. It is therefore necessary to determine exactly how the fish are processed, including what order the processing steps are carried out in. The simplest way to identify and describe how the fish are processed is to draw a flow diagram of the process. 1.2 Determine when in the process the fish are being infested and by what mode It is important to find out when the fish is becoming infested. It is possible that the infestation is occurring at more than one point in the process, or even before the fish arrives at the processing site. Using the process flow diagram as a guide, samples of the processor’s fish should be examined at each processing stage for signs of blowfly eggs and larvae. The earliest stage in the process where blowfly eggs or larvae are found on the fish is the point at which the infestation has first occurred. If there are fresh egg batches or egg cases present on the fish at a later stage, or if larvae of different ages or sizes are infesting the fish, it is possible that the fish is being infested at more than one point in the process. It is also important to find out what mode of infestation is occurring.