V.
VULNIFICUS3.3.1 GEOGRAPHIC DISTRIBUTION
V. parahaemolyticus was isolated for the first time in Japan in the ‘50s, in partially dehydrated
sardines called shirasu which were associated with an outbreak of foodborne illness (Fujino et al., 1953). This microorganism is the most frequent cause of foodborne illness in Japan, with an incidence of approximately 60% of all bacterial foodborne disease (Snydman and Gorbach, 1991). In the past it has caused (and still causes) frequent foodborne diseases in Asia: in Japan, between 1996 and 1998, 496 outbreaks occurred (IDSC, 1999).
Although, as mentioned, most outbreaks occur in Japan, with many cases surely due to high consumption of food products, especially raw fish, infection by this Vibrio species has been
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documented on global scale, suggesting the ubiquity of this microorganism throughout the world (Snydman and Gorbach, 1991).
In recent years, pathogenic strains of V. parahaemolyticus have been associated with outbreaks of gastroenteritis in countries like Spain, Taiwan, Japan, Russia, India, and in North America and South-East Asia (WHO, 1999; DePaola et al., 2000, Yamazaki et al., 2003). In the USA, about 2800 infections due to this bacteria occur every year, following oyster consumption (WHO, 1999). In Europe, three outbreaks caused by V. parahaemolyticus have been reported so far: one in France, with 44 cases in 1997, one in Spain, with 80 cases in 1999, and again in Spain, in 2004 (Suffredini, 2007). The majority of these outbreaks have been attributed to consumption of crustaceans and shellfish living in warm coastal waters (Werner, 1992).
V. cholerae infection has been first described by Pacini (1854) in the same year, later it was
described by Koch (1884). V. cholerae O1, biotype El Tor was isolated for the first time in Indonesia, in 1934, although before that date this microorganism has been isolated, but not well identified, in Sinai, in 1905.
The disease caused by V. cholerae has been pandemic in Asia until the ‘60s of last century. In 1970 this bacteria was detected in Russia and South Korea. The first case in Americas occurred in Peru in 1991, spreading to other South American countries within a few weeks. Until 1992, the toxigenic O1 serogroup has been associated with epidemics and pandemics of cholera, while the non-O1 serogroup has been mainly associated with extra-intestinal infections and limited outbreaks of gastroenteritis (Percival et al., 2004).
There have been many cases of cholera in the 19th century in Italy, like the epidemics in 1855 which has hit coastal cities, but also Milan, Florence and Bologna, causing over 25.000 victims (Pongetti, 2006). In recent times, last reports regard cholera outbreaks in Naples in 1973, as well as the outbreak in Bari at the end of 1994, representing an episode of the seventh cholera pandemic (Squarcione et al., 1996).
V. vulnificus is a bacteria originating especially from warm coastal waters of bays and estuaries,
mainly in the Atlantic and Pacific Oceans, albeit it has been isolated also in other regions, e.g. in the Adriatic Sea (Kelly, 1982; Kaysner et al., 1987; Serratore et al., 2006). This microorganism is responsible for serious wound infections and septicemia in humans (CDC, 1996; Finkelstein et al., 2002). Fortunately usually it is quite rare. In the USA, it is responsible only for a few dozen cases per year (Suffredini et al., 2007). Between 1988 and 1995, CDC (Centers for Disease Control and
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Prevention, USA) reported over 300 cases of V. vulnificus infection in states bordering the Gulf of Mexico (CDC, 2005).
3.3.2 ENVIRONMENTAL AND PHYSICAL FACTORS LEADING TO VIBRIO DISEASES
For Vibrio species like V. vulnificus and V. parahaemolyticus, temperature is the most common factor influencing outbreaks and cases of disease due to these bacteria, considering that their presence in marine environment is more abundant during warmer periods of the year.
Other environmental factor which frequently contributes to spread of these pathogens, especially in case of V. cholerae, is heavy rain which can lead to spread of sewage and contamination of drinking water sources or food products. Also hurricanes or cyclones can lead to contamination, as reported by Panda et al. (2011). These authors found V. cholerae to be responsible of gastroenteritis cases in India following the passage of AILA tropical cyclone.
3.3.3 TRANSMISSION
Typically, infections with V. parahaemolyticus are a consequence of consumption of raw or undercooked seafood, particularly oysters, which not only are eaten raw, but can concentrate pathogens present in surrounding water. Infections are frequently due to consumption of raw fish, especially crustaceans.
For V. cholerae, contaminated food is one of the predominant modes of transmission. In the USA; the majority of cholera cases was associated with consumption of raw or undercooked fish products, especially oysters (Percival et al., 2004). Also water is both a direct or indirect vector of transmission of V. cholerae, and it is of great epidemiologic importance especially in countries in the developing world which do not practice disinfection of drinking water, or when already treated water gets contaminated.
The reservoir of V. cholerae is usually represented by feces of carriers or patients with cholera. In fact cholera is considered a typical disease of overpopulated countries and communities where hygiene standards are poor and inadequate.
There have been reports of cholera acquired also from natural aquatic environments (Percival et al., 2004).
V. vulnificus is found in warm coastal waters, in oysters and other shellfish bivalve mollusks
mostly durng summer months. This pathogen enters the body through already existing wounds when exposed to marine water, or through wounds caused by lacerations and puncture caused by shellfish and other marine organisms, or rocks (Ervin et al., 1984). Also out of water, handling of bivalve mollusks, especially oysters, represents an entry portal for this organism (Ervin et al., 1984).
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Infections can occur also (albeit more rarely) by consumption of raw or undercooked shellfish, leading to severe sepsis. Person to person transmission has not been proven (CDC, 2005).
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