Ortega Foodborne Parasites

1. Auflage 2006
ISBN: 978-0-387-31197-5
Verlag: Springer US
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 284 Seiten, eBook

Reihe: Food Microbiology and Food Safety

Microbiologists are being challenged as foodborne outbreaks are increasingly being observed worldwide. Most of these outbreaks are associated with viral and bacterial pathogens such as Campylobacter, Salmonella, and lately Escherichia coli O157:H7, which emerged in the 1990s. Although parasites have been evolving with Man since antiquity, the control and eradication of these diseases are still far from being achieved. They are more frequently being reported in the literature as causative agents of food and waterborne illnesses. Foodborne Parasites examines the two major parasite groups that are transmitted via water or foods: the protozoa, which are single celled organisms, and the helminths. The helminths are classified in three sub groups: cestodes (tapeworms), nematodes (round worms), and trematodes (flukes). To better understand their significance, each chapter covers the biology, mechanisms of pathogenesis, epidemiology, treatment, and inactivation of these parasites. This important new text is crucial to a better understanding of the biology and control of parasitic infections necessary to reduce and eliminate future outbreaks in the U.S. and elsewhere.

Zielgruppe

Professional/practitioner

Autoren/Hrsg.

Ortega, Ynes R.

Inhaltsverzeichnis

Amoeba and Ciliates.- The Biology of Giardia Parasites.- Coccidian Parasites.- Cryptosporidium and Cryptosporidiosis.- Toxoplasmosis.- Food-Borne Nematode Infections.- Foodborne Trematodes.- Cestodes.- Waterborne Parasites and Diagnostic Tools.- Risk Assessment of Parasites in Food.

Leseproben

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.