Foodborne Parasites (eBook)

Preface 6
Contributors 10
Contents 12
1 Amoeba and Ciliates 17
1.1 PREFACE 17
1.2 AMOEBA 17
1.2.1 Entamoeba histolytica 18
1.3 DIENTAMOEBA FRAGILIS 22
1.3.1 Morphology and Transmission 22
1.3.2 Therapy 23
1.4 NONPATHOGENIC AMOEBA 23
1.4.1 Entamoeba hartmanni 23
1.4.2 Entamoeba coli 23
1.4.3 Endolimax nana 23
1.4.4 Iodamoeba butschlii 23
1.5 FREE-LIVING AMOEBAE 24
1.6 CILIATES 24
1.6.1 Life Cycle and Morphology 25
1.6.2 Clinical Significance 25
1.6.3 Diagnosis and Treatment 27
1.6.4 Epidemiology and Prevention 27
REFERENCES 27
2 The Biology of Giardia Parasites 31
2.1 PREFACE 31
2.2 BIOLOGY 32
2.3 DETECTION AND CLASSIFICATION OF GIARDIA 33
2.3.1 Detection Methods 33
2.3.2 Classification of G. intestinalis 35
2.3.3 Genotyping of G. intestinalis 36
2.4 TRANSMISSION AND EPIDEMIOLOGY 39
2.4.1 Human 39
2.4.2 Environmental 40
2.5 CONTROL AND TREATMENT 41
REFERENCES 44
3 Coccidian Parasites 49
3.1 PREFACE 49
3.2 BACKGROUND/HISTORY 49
3.3 BIOLOGY 52
3.4 CLINICAL SIGNIFICANCE 54
3.5 TRANSMISSION AND EPIDEMIOLOGY 55
3.5.1 Cyclospora 55
3.5.2 Isospora 58
3.5.3 Sarcocystis 58
3.6 DIAGNOSIS 61
3.7 TREATMENT AND CONTROL 62
REFERENCES 63
4 Cryptosporidium and Cryptosporidiosis 73
4.1 PREFACE 73
4.2 TAXONOMY 73
4.3 LIFE CYCLE AND DEVELOPMENTAL BIOLOGY 76
4.4 EPIDEMIOLOGY AND TRANSMISSION 77
4.4.1 Cryptosporidiosis in Immunocompetent Persons 77
4.4.2 Cryptosporidiosis in Immunocompromised Persons 78
4.4.3 Transmission Routes and Infection Sources: Anthroponotic Versus Zoonotic Transmission 79
4.4.4 Waterborne Transmission 80
4.4.5 Foodborne Transmission 82
4.5 DETECTION AND DIAGNOSIS 85
4.5.1 Serologic Methods 85
4.5.2 Methods for Detection of Cryptosporidium in Stool Specimens 85
4.5.3 Methods for Detection of Cryptosporidium Oocysts in Environmental Samples 93
4.6 TREATMENT 97
4.7 CONTROL OF CRYPTOSPORIDIUM CONTAMINATION IN WATER AND FOOD 98
REFERENCES 102
5 Toxoplasmosis 125
5.1 PREFACE 125
5.2 PARASITE DESCRIPTION 125
5.3 LIFE CYCLE 126
5.4 TRANSMISSION 128
5.5 IDENTIFICATION 128
5.5.1 Molecular Assays 129
5.5.2 Riboprinting 130
5.6 PATHOGENICITY 131
5.7 EPIDEMIOLOGY 131
5.7.1 Humans 131
5.7.2 Swine 134
5.7.3 Poultry 136
5.7.4 Sheep and Goats 137
5.7.5 Other Animal Species 138
5.8 TREATMENT 139
5.9 INACTIVATION 140
REFERENCES 141
6 Food-Borne Nematode Infections 151
6.1 PREFACE 151
6.2 TRICHINELLA SPP. 151
6.2.1 Background 151
6.2.2 Speciation 152
6.2.3 Life Cycle 152
6.2.4 Epidemiology 153
6.2.5 Human Trichinellosis–Epidemiology 156
6.2.6 Clinical Manifestations 158
6.2.7 Diagnosis and Treatment 159
6.2.8 Prevention and Control 159
6.3 ANISAKIS SIMPLEX AND RELATED SPECIES 161
6.3.1 Background 161
6.3.2 Life Cycle 162
6.3.3 Epidemiology 162
6.3.4 Clinical Manifestations 163
6.3.5 Diagnosis and Treatment 163
6.3.6 Prevention and Control 164
6.4 ANGIOSTRONGYLUS CANTONENSIS AND ANGIOSTRONGYLUS COSTARICENSIS 164
6.5 GNATHOSTOMA SPP. 166
6.6 GONGYLONEMA SPP. 167
6.7 OTHER NEMATODE INFECTIONS WITH FOOD-BORNE ASSOCIATIONS 168
REFERENCES 169
7 Foodborne Trematodes 177
7.1 PREFACE 177
7.2 PARAGONIMUS SPP. 177
7.2.1 Introduction 177
7.2.2 Life Cycle 179
7.2.3 Epidemiology 181
7.2.4 Clinical Signs, Diagnosis, and Treatment 182
7.3 CLONORCHIS SINENSIS 184
7.3.1 Introduction 184
7.3.2 Life Cycle 185
7.3.3 Epidemiology 186
7.3.4 Clinical Signs, Diagnosis, and Treatment 187
7.4 OPISTHORCHIS VIVERRINI AND OPISTHORCHIS FELINEUS 190
7.4.1 Introduction 190
7.4.2 Life Cycle 190
7.4.3 Epidemiology 191
7.4.4 Clinical Signs, Diagnosis, and Treatment 192
7.5 NANOPHYETUS SALMINCOLA 193
7.5.1 Introduction 193
7.5.2 Life Cycle 193
7.5.3 Salmon Poisoning Disease 195
7.5.4 Clinical Signs, Diagnosis, and Treatment 196
7.6 FASCIOLA SPP. 198
7.6.1 Introduction 198
7.6.2 Life Cycle 198
7.6.3 Epidemiology 200
7.6.4 Clinical Signs, Diagnosis, and Treatment 200
7.7 FASCIOLOPSIS BUSKI 202
7.7.1 Introduction 202
7.7.2 Life Cycle 203
7.7.3 Epidemiology 204
7.7.4 Clinical Signs, Diagnosis, and Treatment 204
7.8 PREVENTION AND CONTROL 205
REFERENCES 207
8 Cestodes 213
8.1 PREFACE 213
8.2 TAENIA 213
8.2.1 Taenia solium 214
8.2.2 Taenia saginata 223
8.2.3 Taenia asiatica 225
8.3 DIPHYLLOBOTHRIUM 227
8.3.1 Diphyllobothrium Latum 227
8.3.2 Diphyllobothrium pacificum 230
8.4 SPIROMETRA 231
8.4.1 Spirometra mansoides 231
8.5 ECHINOCOCCUS 232
8.5.1 Echinococcus granulosus 232
8.5.2 Echinococcus multilocularis 237
8.6 HYMENOLEPIS 239
8.6.1 Hymenolepis nana 239
REFERENCES 241
9 Waterborne Parasites and Diagnostic Tools 247
9.1 PREFACE 247
9.2 PARASITES 248
9.3 CONCENTRATION AND ISOLATION TECHNIQUES 251
9.4 DETECTION METHODOLOGIES 253
9.4.1 Microscopic Techniques 253
9.4.2 Nucleic Acid Techniques 255
9.4.3 Immunological-based Techniques 264
9.4.4 Viability Techniques 266
9.5 PROPER EVALUATION (QA/QC) 269
REFERENCES 271
10 Risk Assessment of Parasites in Food 291
10.1 PREFACE 291
10.2 THE RISK ASSESSMENT FRAMEWORK 292
10.2.1 Defining the Hazard 292
10.2.2 Exposure Assessment 293
10.2.3 Hazard Characterization (Dose-response Assessment) 294
10.2.4 Risk Characterization 296
10.2.5 Assumptions, Assumptions, Assumptions 297
10.2.6 Emerging Applications of Microbial Risk Assessment 298
REFERENCES 298
Index 301

CHAPTER 4 Cryptosporidium and Cryptosporidiosis (p. 57-58)

Lihua Xiao and Vitaliano Cama

4.1 PREFACE

Cryptosporidium spp. are apicomplexan parasites that inhabit the brush-borders of the gastrointestinal epithelium (Bird and Smith, 1980). Initially thought to be only a pathogen of young animals such as calves, lambs, piglets, and foals, cryptosporidiosis is now known to be an important cause of enterocolitis, diarrhea, and cholangiopathy in humans (Current et al., 1983). Several Cryptosporidium spp. are now recognized to infect humans and more to infect other vertebrates (Xiao et al., 2004a). Healthy children and adults and young animals with cryptosporidiosis usually have a short-term illness accompanied by watery diarrhea, vomiting, malabsorption, and weight loss. In humans and animals with immunodeficiencies, and snakes, however, the infection can be protracted and life-threatening (Hunter and Nichols, 2002).

Cryptosporidium oocysts are environmentally resistant, retain their infectious potential for considerable time in moist environments, such as water, soil, fresh seafood and produce (Rose, 1997), and survive most water disinfection treatments as well (Korich et al., 1990). Two important fecal-oral transmission routes include direct contact with infected persons (person-to-person or anthroponotic transmission) or animals (zoonotic transmission), and consumption of contaminated water (waterborne transmission) or food (foodborne transmission). Thus, Cryptosporidium spp. are well recognized water and food-borne pathogens, having caused many outbreaks of human diarrheal disease in the United States and other developed countries (Anonymous, 1984, Current et al., 1983, D’Antonio et al., 1985, Joce et al., 1991, MacKenzie et al., 1994b, Millard et al., 1994).Water and food probably also play an important role in the transmission of cryptosporidiosis in endemic areas, even though the disease burden attributable to them is not fully clear.

4.2 TAXONOMY

Cryptosporidium spp. belong to the family Cryptosporidiidae, which is a member of the phylum Apicomplexa. The exact placement of Cryptosporidiidae in Apicomplexa is uncertain. It was long considered a member of the class Coccidea, in the order of Eimeriida or Eucoccidiorida (Corlis, 1994). Recent phylogenetic studies, however, indicate that Cryptosporidium spp. are more related to gregarines than to coccidia (Carreno et al., 1999). Extra-celluar gregarine-like reproductive stages have been described in Cryptosporidium andersoni and Cryptosporidium parvum (Hijjawi et al., 2002). Thus, Cryptosporidium spp. are no longer considered coccidian parasites.

Cryptosporidium spp. were first recognized by Tyzzer in 1907, who described Cryptosporidium muris in the stomach of laboratory mice (Tyzzer, 1907, 1910). Later in 1912, Tyzzer described a second species in laboratory mice, C. parvum (Tyzzer, 1912). This new species differed from C. muris not only by infecting the small intestine instead of the stomach, but also by having smaller oocysts, the environmentally robust stage of the parasite (Upton and Current, 1985). Over the next 50 years following the initial description of Cryptosporidium, these parasites were commonly confused with sporocysts of Sarcocystis. Several new Cryptosporidium species were described during the period, mostly based on sporocysts of Sarcocystis spp. Subsequently, it was thought that because Cryptosporidium was closely related to Eimeria, Cryptosporidium spp. also could not normally be transmitted from one species of animals to another (Levine, 1980). This erroneous concept of strict host specificity led to the description and report of multiple new species during the 1960–1980s, which are no longer considered valid, such as Cryptosporidium anserinum in geese (Proctor and Kemp, 1974), Cryptosporidium agni in sheep (Barker and Carbonell, 1974), Cryptosporidium bovis in neonatal calves (Barker and Carbonell, 1974), Cryptosporidium rhesi in monkeys (Levine, 1980), and Cryptosporidium cuniculus in rabbits (Inman and Takeuchi, 1979). Infection and cross-transmission studies conducted in the 1970s and 1980s demonstrated that Cryptosporidium isolates could indeed frequently be transmitted from one host species to another (Tzipori et al., 1981a, 1981b, 1982). These findings led to the synonymization of many species into C. parvum, and were the basis for proposing the monospecific structure of the genus Cryptosporidium. As a result, C. parvum was used extensively for the description of Cryptosporidium spp. from most mammals including humans (Tzipori et al., 1980, Upton and Current, 1985).

The recent use of molecular methods in the characterization of Cryptosporidium has helped to resolve existing confusions in the taxonomy of this genus (Fayer et al., 2000a, Morgan et al., 1999b, Xiao et al., 2000b, 2004a). These molecular tools have been very valuable when used in conjunction with morphological, biological, or host specificity studies. This has resulted in the validation of several Cryptosporidium described earlier, such as Cryptosporidium meleagridis in birds, Cryptosporidium wrairi in guinea pigs, and Cryptosporidium felis in cats. It is now well known that various Cryptosporidium isolates do have differences in host specificity, but one Cryptosporidium sp. usually infect a limited spectrum of animals, especially if the host animals are related. This new Cryptosporidium taxonomic paradigm has also led to the establishment of several new Cryptosporidium species, such as Cryptosporidium hominis (previously known as C. parvum genotype 1 or the human genotype) in humans, C. andersoni (previously known as C. muris-like or C. muris bovine genotype) and C. bovis (previously known as Cryptosporidium bovine genotype B) in weanling calves and adult cattle, Cryptosporidium canis (previously known as C. parvum dog genotype) in dogs, and Cryptosporidium suis (previously known as Cryptosporidium pig genotype I) in pigs.