MICROBIOLOGICAL STUDY OF THE INTESTINAL AND CROP CONTENTS OF WILD AND CULTIVATED EDIBLE SNAIL

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study
The terrestrial snails like Achatina fulica, Achatina achatina and Archachatina marginata are large‐sized terrestrial mollusks that can grow up to 20 cm in length and 10 cm in diameter. In these snails, the brownish shell having dark stripes generally covers half of the body (Ohlweiler, et. al., 2010). Among these, the shell of A. fulica is smaller and can grow up to 3–4 inches, while A. achatina has a larger shell size of 10–11 inches (Uyoh et. al., 2013).
The calcareous shell of the snail when burnt, ground into powder and mixed with oil and has been applied to boils by many indigenes of Africa as a form of treatment. Snail products such as the haemolymph are also being exploited as a cure for ailments. The invasive land snail Achatina fulica, is a species known to carry parasites and harbours a dense and metabolically active microbial community, the diversity and composition of which is however unknown (Cardoso et. al., 2012).
Apart from the conventional sources of protein; which are mainly meat and fish, snails (molluscs) are excellent sources of protein and mineral elements for many families. Snail meat is a nutritious food that is high in protein, low in fat and a good source of iron (USDA, 2006). Snail meat is high in protein, iron, calcium and phosphorus, but low in sodium, fat and cholesterol, and contains almost all the amino acids needed by man. The meat is high in health benefiting essential fatty acids such as linoleic and linolenic acids (Su, et. al, 2004). Furthermore, African giant snails (Archachatina marginata and Achatina achatina) are considered as a delicacy in Nigeria and they command high demand in the market. Archachatina marginata is the largest known snail in Africa. Snails have high rate of productivity or fecundity (Olawoyin and Ogogo, 2006). Though they are hermaphrodites, they practice sexual reproduction and snails are selective in their mating partners and sometimes uninterested in mating with other snails of the same species originating from a considerable distance away (Omole and Kehinde, 2005). The natural habitat of snails are mostly found in the forest, farms and gardens where they have unlimited vegetation to feed on. The most dominant types of vegetation in Africa are the tropical forest and the savannah where a wide variety of the African terrestrial Gastropods inhabit. Most land snails, especially, the African giant land snails that are eaten and exported are usually picked from their natural habitat. However, with the large market for the meat, many concerns have been raised about the reduction in their natural population. With challenges such as depletion of the stock of wild snails, over population, high cost of conventional animal protein and also for health reasons, the demand for snails has increased such that commercial production is necessary. This led to the introduction of snail breeding farms with the farm purpose of supplying snails to meet the market demands (Raut and Barker, 2002). The close contact of wild snails with soil and their uncontrolled feeding pattern make the snail susceptible to microbial contamination. Snails inherently have high populations of indigenous bacteria coliforms and other poisonous substances which they ingest (ICMSF, 2005). The meat can be easily contaminated by pathogens and serve as vehicle of transferring infectious agents to consumers (Kiran, et. al., 2006). Despite the rich nutritional values of snail, the involvement of the molluscs in the transmission of infection mostly as secondary host for pathogens makes it necessary to study the microbiology of the resident snail. The fact that consumption of field collected snails may lead to bacterial infection, the provision of a systemic farming of snails will help solve both the problem of depletion of snail populations as well as provision of a relatively wholesome meat with less microbial contaminations (Samia, et. al., 2017).

1.2 Statement of the Problem
Microorganisms have various functions and potentials and they are found everywhere (ubiquitous). The health of humans and that of the environment is highly dependent on the surroundings, particularly the food consumed. Many bacterial and fungal species inhabit the intestinal tract and crop of snails and thus, are introduced into food chain where they are capable of causing infections if not properly processed.

1.3 Justification of the Study
Snails serve as meat and are highly proteinous for human diet. Snails can be gotten from the wild which is their natural environment such as bushes, or from breeding farms where they are cultivated. These environments give them different feeding habits. The wild type snails feed freely from the plants, soil, and other components of the environment while the cultivated ones eat only special feeds from different manufacturers. This is likely to make their intestinal flora different. Examination of the intestinal tract and crop contents of these snails therefore become importance in understanding the microbial attributes as well as the health significance of the isolates since they can be introduced into food chain.