678 Modern Food Microbiology 136 Warnken, M.B., M.P Nunes, and A.L.S Noleto 1987 Incidence of Yersinia species in meat samples purchased in Rio de Janeiro, Brazil J Food Protect 50:578–579, 583 137 Wright, A.C., and J.G Morris, Jr 1991 The extracellular cytolysin of Vibrio vulnificus: Inactivation and relationship to virulence in mice Infect Immun 59:192–197 138 Wu, V.C.H., D.Y.C Fung, and R.D Oberst 2004 Evaluation of a -nuclease (TaqMan) assay with the thin agar layer oxyrase method for the detection of Yhersinia enterocolitica in ground pork samples J Food Protect 67:271–277 139 Yamamoto, K., Y Ichinose, H Shinagawa, K Makino, A Nakata, M Iwanaga, T Honda,and T Miwatani 1990 Two-step processing for activation of the cytolysin/hemolysin of Vibrio cholerae 01 biotype E1 Tor: Nucleotide sequence of the structural gene (hlyA) and characterization of the processed products Infect Immun 58:4106–4116 140 Yamamoto, K., A.C Wright, J.B Kaper, and J.G Morris, Jr 1990 The cytolysin gene of Vibrio vulnificus: Sequence and relationships to the Vibrio cholerae E1 Tor hemolysin gene Infect Immun 58:2706–2709 141 Yamamoto, T., and T Yokota 1989 Adherence targets of Vibrio parahaemolyticus in human small intestines Infect Immun 57:2410–2419 142 Yuki, N., T Taki, M Takahashi, K saito, T Tai, T Miyatake, and S Hande 1994 Penner’s serotype of Campylobacter jejuni has a lipopolysaccharide that bears a GM1 ganglioside epitope as well as one that bears a GD1a epitope Infect Immun 62:2101–2103 143 Zen-Yoji, H., Y Kudoh, H Igarashi, K Ohta, and K Fukai 1975 Further studies on characterization and biological activities of an enteropathogenic toxin of Vibrio parahaemolyticus Toxicon 13:134–135 Chapter 29 Foodborne Animal Parasites The animal parasites that can be contracted by eating certain foods belong to three distinct groups: protozoa, flatworms, and roundworms Several of the more important members of each group of concern in human foods are examined in this chapter along with their classification In contrast to foodborne bacteria, animal parasites not proliferate in foods, and their presence must be detected by direct means, as they cannot grow on culture media Because all are larger in size than bacteria, their presence can be detected rather easily by the use of appropriate concentration and staining procedures Because many are intracellular pathogens, resistance to these diseases is often by cellular phenomena similar to that for listeriosis (see Chapter 25) Finally, another significant way in which some animal parasites differ from bacteria is their requirement for more than one animal host in which to carry out their life cycles The definitive host is the animal in which the adult parasite carries out its sexual cycle; the intermediate host is the animal where larval or juvenile forms develop In some instances, there is only one definitive host (e.g., cryptosporidiosis); in others, more than one animal can serve as definitive host (e.g., diphyllobothriasis); and in still other cases, both larval and adult stages reside in the same host (e.g., trichinosis) PROTOZOA The protozoa belong to the kingdom Protista (Protoctista), which also comprises the algae and flagellate fungi They are the smallest and most primitive of animal forms, and the five genera of concern in foods are classified as follows: Kingdom Protista Phylum Sarcomastigophora Phylum Sarcomastigophora Class Zoomastigophorea Order Diplomonadida Family Hexamitidae Genus Giardia Subphylum Sarcodina Superclass Rhizopoda Class Lobosea 679 680 Modern Food Microbiology Order Amoebida Family Endamoebidae Genus Entamoeba Phylum Apicomplexa (= Sporozoa) Class Sporozoea Class Lobosea Order Eucoccidiida Family Sarcocystidae Genus Toxoplasma Genus Sarcocystis Family Cryptosporidiidae Genus Cryptosporidium Genus Cyclospora Giardiasis Giardia lamblia is a flagellate protozoan that exists in environmental waters at a higher level than Entamoeba histolytica The protozoal cells (trophozoites) produce cysts, which are the primary forms in water and foods The cysts are pear shaped, with a size range of 8–20 µm in length and 5–12 µm in width The trophozoites have eight flagella that arise on the ventral surface near the paired nuclei and give rise to “falling-leaf” motility Upon ingestion, Giardia cysts excyst in the gastrointestinal tract with the aid of stomach acidity and proteases and give rise to clinical giardiasis in some individuals Excystation of the trophozoites occurs somewhere in the upper small intestine, and this step is regarded as being equivalent to a virulence factor.9 The trophozoites are not actively phagocytic, and they obtain their nutrients by absorption Occasionally, bile ducts are invaded, leading to cholecystitis Compared to some of the other intestinal protozoal parasites, Giardia trophozoites not penetrate deeply in parenteral tissues Environmental Distribution Water is the second most common source of giardiasis The first recorded outbreak occurred at a ski resort in Aspen, Colorado, in 1965 with 123 cases.22 Between 1965 and 1977, 23 waterborne outbreaks were recorded that affected over 7000 persons.23 Between 1971 and 1985, 92 outbreaks were reported in the United States.22 Giardia cysts are generally resistant to the levels of chlorine used in the water supply Beavers and muskrats have been shown to be the major sources of this organism in bodies of water In a study of 220 muskrat fecal specimens collected from natural waters in southwestern New Jersey, 70% contained Giardia cysts.59 It is estimated that up to 15% of the U.S population is infected with this organism Syndrome, Diagnosis, and Treatment The incubation period for clinical giardiasis is 1–4 weeks, and cysts appear in stools after 3–4 weeks Asymptomatic cyst passage is the most benign manifestation of G lamblia infection in humans, but when clinical giardiasis occurs, symptoms may last from several months to a year or more Up to 9.0 × 108 cysts are shed each day by patients, and they may survive as long as months in sewage sludge.3 Foodborne Animal Parasites 681 G lamblia is generally noninvasive, and malabsorption often accompanies the symptomatic disease.96 Growth of the organism is favored by the high bile content in the duodenum and upper jejunum.79 From an outbreak of giardiasis among 1400 Americans on the Madeira Island in 1976, the symptoms, along with the percentage incidence among victims, were as follows: abdominal cramps (75%), abdominal distention (72%), nausea (70%), and weight loss (40%) The median incubation period was days, and G lamblia was recovered from 47% of 58 ill patients The consumption of tapwater and the eating of ice cream or raw vegetables were significantly associated with the illness.66 The 29 victims of the 1979–1980 outbreak traced to home-canned salmon (see below) displayed the following symptoms: diarrhea (100%), fatigue (97%), abdominal cramps (83%), fever (21%), vomiting (17%), and weight loss (59%), among others.77 From another study of 183 patients, the five leading symptoms (and percentage complaining) were diarrhea (92%), cramps (70%), nausea (58%), fever (28%), and vomiting (23%).96 Weight loss of about lb or so is a common feature of giardiasis, and it was associated with the 1985 outbreak traced to noodle salad.78 Giardiasis is a highly contagious disease It has been documented in daycare centers where unsanitary conditions prevailed The human infection rate ranges from 2.4 to 67.5%.19 The minimum infectious dose of G lamblia cysts for humans is 10 or less.82 Giardiasis is diagnosed by the demonstration of trophozoites in stool specimen by microscopic examinations using either wet mounts or stained specimens G lamblia can be grown in axenic culture, but this does not lend itself to rapid diagnosis Effective enzyme-linked immunosorbent assay (ELISA) tests have been developed Both circulating antibodies and T lymphocytes are elicited during infection by G lamblia Because no enterotoxin has been demonstrated, diarrhea is caused by other factors.96 The drug of choice for the treatment of giardiasis is quinacrine, an acridine derivative Also effective are metronidazole and tinidazole.96 Incidence in Foods and Foodborne Cases Giardia has been shown to occur in some vegetables, and it may be presumed that the organism occurs on foods that are washed with contaminated water or contaminated by unsanitary asymptomatic carriers Of 64 heads of lettuce examined in Rome, Italy, in 1968, 48 contained Giardia cysts, and cysts were recovered from strawberries grown in Poland in 1981.3 As early as 1928, it was suggested that hospital food handlers were the likely source of protozoal infections of patients Of 844 private patients in an urban center, 36% contracted giardiasis, and it was believed the infections were acquired by eating cyst-contaminated raw fruits and vegetables These and some other early incidences of possible foodborne giardiasis have been discussed by Barnard and Jackson.3 Following is a list of suspected and proved foodborne giardiasis: Three of four members of a family who in 1960 ate Christmas pudding thought to have been contaminated by rodent feces became victims.21 Giardia-like cysts were found In their surveillance of foodborne diseases in the United States for 1968–1969, Gangarosa and Donadio39 recorded an outbreak of giardiasis with 19 cases for 1969 but provided no further details In December 1979, 29 of 60 school employees in a rural Minnesota community contracted the disease from home-canned salmon prepared by a worker after changing the diaper of an infant later shown to have an asymptomatic Giardia infection.77 This was the first well-documented common-source outbreak 682 Modern Food Microbiology In July 1985, 13 of 16 individuals at a picnic in Connecticut met the case definition of giardiasis, and the most likely vehicle food was a noodle salad.78 Although most victims developed symptoms between and 20 days after the picnic, the salad preparer became ill the day after the food was eaten by others This was the second well-documented common-source outbreak traced to a food product In 1988, 21 of 108 members of a church youth group in Albuquerque, New Mexico, were victims Taco ingredients were the most likely vehicles from dinners prepared by parents at a church.18 The U.S Centers for Disease Control and Prevention (CDCP) recorded foodborne giardiases outbreaks in 1985 and 1986, with outbreak and 13 cases in 1985 and outbreaks and 28 cases in 1986.5 The common occurrence of this organism suggests that it may be a more frequent cause of foodborne infection than is reported The incubation period of days plus could be a factor in the apparent underreporting Another possible factor is the need to demonstrate the organism in stools and leftover foods by microscopic examination, a practice that is not routine in the microbiological examination of foods in foodborne gastroenteritis outbreaks Amebiasis Amebiasis (amoebic dysentery), caused by Entamoeba histolytica, is often transmitted by the fecal– oral route, although transmission is known to occur by water, food handlers, and foods According to Jackson48 there is better documentation of food transmission of amebic dysentery than for the other intestinal protozoal diseases The organism is unusual in being anaerobic, and the trophozoites (ameba stages) lack mitochondria It is an aerotolerant anaerobe that requires glucose or galactose as its main respiratory substrate.69 The trophozoites of E histolytica range in size from 10 to 60 µm, whereas the cysts usually range between 10 and 20 µm The trophozoites are motile; the cysts are not It is often found with Entamoeba coli, with which it is associated in the intestine and stools In warm stools from a case of active dysentery, E histolytica is actively motile and usually contains red blood cells that the protozoan ingests by pseudopodia Although generally outnumbered in stools by Entamoeba coli, the latter never ingests red blood cells Although the trophozoites not persist under environmental conditions, the encysted forms can survive as long as months in sewage sludge.3 A person with this disease may pass up to 4.5 × 107 cysts each day.3 The possible transmission of cysts to foods becomes a real possibility when poor personal restroom hygiene is practiced The incidence of amebiasis varies widely, with a rate of 1.4% reported for Tacoma, Washington, to 36.4% in rural Tennessee.19 It is estimated that 10% of the world’s population is infected with E histolytica and that up to 100 million cases of amebic colitis or liver abscesses occur each year In its trophozoite stage, the organism induces infection in the form of abscesses in intestinal mucosal cells and ulcers in the colon Its adherence to host-cell glycoproteins is mediated by a galactose-specific lectin It reproduces by binary fission in the large intestine It encysts in the ileum, and cysts may occur free in the lumen The organism produces an enterotoxic protein with molecular weight of 35,000– 45,000 Da.19 Syndrome, Diagnosis, and Treatment The incubation period for amebiasis is 2–4 weeks, and symptoms may persist for several months Its onset is often insidious, with loose stools and generally no fever Mucus and blood are characteristic ... it may be presumed that the organism occurs on foods that are washed with contaminated water or contaminated by unsanitary asymptomatic carriers Of 64 heads of lettuce examined in Rome, Italy,... in human foods are examined in this chapter along with their classification In contrast to foodborne bacteria, animal parasites not proliferate in foods, and their presence must be detected by direct... 36% contracted giardiasis, and it was believed the infections were acquired by eating cyst-contaminated raw fruits and vegetables These and some other early incidences of possible foodborne giardiasis