It is important to note that the aquarium snail contains bacteria that can cause infections to man when the snail meat is not properly cooked and when the processing is not done under sanitized condition (Fagbuaro et al., 2006). Aquarium snails are found majorly in southern parts of Nigeria, North African coast area, Central and South Africa where the weather is most favourable for their proliferation (Herbert et al., 2001).
It has been observed that edible snails obtained from swamps in North African coast for consumption in North America carry with them Salmonella species (Andrews et al., 1975). Many kinds of aquatic snails make excellent additions to an aquarium.2.3 Aetiology of Human Bacterial Infections from the Consumption of Snails
Pathogenic and potentially pathogenic and enteric bacteria associated with aquarium snail include Staphylococcus auerus, Escherichia coli, Klebsiella species and Aeromonas species, vibro species, pseudomonas species and others (Chattopadhyay, 2000). People most often get infected as follows (Acha and Szyfres, 2003).
Through contact with infected aquarium snails while handling them, water or other constituents of snail life environment; the following cases of trans- missions have been recorded so far: after injury by cleaning aquarium with bare hands (Alinovi, 1993), after exposure to snail tank water (Kern, 1989), by handling tropical snail ponds (Guarda, 1992), by contact with rare tropical snail (Bhay, 2000), by contact with a fresh- or salt-water environment (Hayman, 1991; Jernigan and Farr, 2000), infection of young children who are in contact with a snail (Bleiker, 1996; Speight and Williams, 1997), through processing snail in the food industry and preparation of dishes (Notermans and Hoornstra, 2000) or Orally by consumption infected snail or related products or food contaminated with water or other constituents of water environment. Apart from factors relating to the living environment (exposure), the development of an infectious disease is markedly affected by internal factors such as the physiological status of consumer, particularly by immune suppression and stress as in the case of HIV/AIDS (Von Reyn, 1996).
2.4 Enteric Bacteria and Food Borne Pathogens Associated with Aquarium Snails
From the standpoint of microbiology, snails and related products are a risk food stuff group. Particularly, Clostridium botulinum type E and Vibrio parahaemo lyticus rank among pathogenic bacteria associated with snails and fish. Other potentially pathogenic and enteric bacteria associated with aquarium snails include Staph. species, Klebsiella species, E.coli, Salm. Species, Shigella species, V. cholerae and other vibrios. Outbreaks usually occur due to the ingestion of insufficiently heat treated snails or products contaminated after/during their processing. Freezing snails and related products in the sea- water, intensive handling, long-time transport or cooking in snail containers straight on the deck contributes to their contamination with microorganisms. Temperature and pH are limiting factors for the survival of bacteria in snail products; these facts are used during the processes of pasteurization and heat treatment (Whipple and Rohovec, 1994). In the technology of marine animal processing by cooking, the following critical aspects of marine animals are significant: the duration of cooking, temperature of steam, water and other media used for the cooking, thickness of the cut cooked, accuracy of thermometer and other monitoring and timing devices.
Microbiological criteria for snails and its products, and molluscs have been elaborated both on international (Codex Committee on Food Hygiene) and European levels (competent European institution). The mandatory requirements on hygiene of foodstuffs are given in Regulation (EC) No. 852/2004 of the European Parliament and of the Council of 29 April, 2004. Since this Regulation replaces Directive 93/43/EEC, the later should be repealed. Microbiological criteria, including samples plans and methods of analysis, are laid down when there is a need to protect public health. Microbiological criteria for snail and snail products include quantification of the counts of Escherichia coli, thermo tolerant coliform, mesophilic aerobic bacteria and pathogenic V. parahaemolyticus is performed during the production. At the finished product stage, the measure monitored is the quantification of the count of Staph. aureus and detection of bacteria of Salmonella genus as their presence indicates recontamination of a finished product (Council Directive 91/493/EEC).
2.5 Escherichia coli
E. coli is a gram-negative, facultatively, anaerobic, rod-shaped bacterium of the genus Eschericha that is commonly found in the lower intestine of warm-blooded organism (Ryan & Ray, 2004). Most E.coli strains are harmless, but some serotype can cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination (Groopman, 2008) E. coli (Escherichia coli) is the name of a germ, or bacterium, that lives in the digestive tracts of humans and animals. There are many types of E. coli, and most of them are harmless. But some can cause bloody diarrhea. Some strains of E. coli bacteria (such as a strain called O157:H7) may also cause severe anemia or kidney failure, which can lead to death. Other strains of E. coli can cause urinary tract infections or other infections.
One can get an E. coli infection by coming into contact with the feces, or stool, of humans or animals. This can happen when you drink water or eat food that has been contaminated by feces. E. coli can get into meat during processing. If the infected meat is not cooked to 160°F (71°C), the bacteria can survive and infect you when you eat the meat. This is the most common way people in the United States become infected with E. coli. Any food that has been in contact with raw meat can also become infected.
Other foods that can be infected with E. coli include: Raw milk or dairy products. Bacteria can spread from a cow's udders to its milk. Check the labels on dairy products to make sure they contain the word "pasteurized." This means the food has been heated to destroy bacteria. Raw fruits and vegetables, such as lettuce, alfalfa sprouts, or unpasteurized apple cider or other unpasteurized juices that have come in contact with infected animal feces. Human or animal feces infected with E. coli sometimes get into lakes, pools, and water supplies. People can become infected when a contaminated city or town water supply has not been properly treated with chlorine or when people accidentally swallow contaminated water while swimming in a lake, pool, or irrigation canal. The bacteria can also spread from one person to another, usually when an infected person does not wash his or her hands well after a bowel movement. E. coli can spread from an infected person's hands to other people or to objects.
E. coli is a classic example of enteric bacteria causing gastroenteritis. E. coli including other coliforms and bacteria as Staphylococcus species and sometimes enterococci are commonly used as indices of hazardous conditions during processing of snails. Such organisms should not be present on fresh-caught snail (Chattopadhyay, 2000). The contamination of food snail origin with pathogenic E. coli probably occurs during handling of snails and during the production process (Ayulo, 1994; Asai, 1999). An outbreak of diarrhoeal illness caused by ingestion of food contaminated with enterotoxigenic E. coli was described in Japan (Mitsuda, 1998). The illness was strongly associated with eating tuna paste. Brazilian authors (Vieira, 2001) isolated 18 enterotoxigenic strains of E. coli (ETEC) from 3 of 24 samples of fresh snail originating from Brazilian markets; 13 of them produced a thermolabile enterotoxin. The authors explained the presence of toxic strains of E. coli in samples collected from snail (not from water) from one snail market by a longer survival of bacteria on an adequate substrate, i.e. inside the living organism. The isolation of 317 E. coli isolates tested for thermostabile (ST) and thermolabile (LT) toxins has been described in another Brazilian study Infection with verocytotoxin-producing strains of E. coli (VTEC) after ingestion of snail was recorded in Belgium (Pierard, 1999).
2.6 Morphological of Escherichia coli
E. coli is a Gram-negative bacterium which does not retain crystal violet dye, facultative anaerobic that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation anaerobic respiration if oxygen is absent and nonsporulating bacterium (Groopman, 2008) Cells are typically rod-shaped, and are about 2.0 micrometers long and 0.25-1.0 micrometer in diameter.
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