Food-borne Parasitic Zoonosis Research Articles

Optimization method for biomolecular identification of muscle larva of Trichinella species.

Trichinellosis is a food-borne parasitic zoonosis with a yearly incidence of about 10,000 clinical cases worldwide. It is one of the most serious zoonotic diseases in Romania with more than 28,000 human cases reported over the last 25 years. In this context Romania remains the country with the highest infestation with Trichinella from the word. The aim of the paper it is to identify the simple repetitive sequences from Trichinella genus through a biomolecular analysis of isolates. After conducting the DNA extraction from 50-100 muscle larvae of the six selective strains (jackal, wolf 1, wolf 4, 7.97, 7.42 and 7.29) using the “ QIAamp DNA” (Qiagen, Germany) the amplification with ESV primers (forward and reverse) using the “mi-Taq Mix Kit ”(Metabion, Germany) followed, obtaining in this manner a positive amplification for all the six strains taken into study, revealing also the method's efficiency in the biomolecular identification of Trichinella strains. The goal of this research, in perspective, is to improve the DNA extraction from one LM, in order to reduce the chemical and biological reagents. The positive amplification of the genomic DNA from one larva may have favorable repercussions on the genetic variability analysis in the population of Trichinella studied, which can be applied on various individuals belonging to the same population.

Use of Nuclear Microsatellites in Genetic Variability Assessment of Trichinella Isolates

Trichinellosis is a food-borne parasitic zoonosis with a yearly incidence of about 10,000 clinical cases worldwide. It is one of the most serious zoonotic diseases in Romania with more than 28,000 human cases reported over the last 25 years. Trichinella species and genotypes are present on all continents, from the tropical regions to the cold ones. Up to date, there have been identified four Trichinella species in Europe: T. spiralis, T. nativa, T. britovi and T. pseudospiralis. In order to identify a genetic variability in ecologically distinct species of Trichinella, which may lead to a potential geographical disposition of Trichinella isolates, we test the variability of nine nuclear microsatellite loci, in a small population of Trichinella isolates of Romania. As a result, we obtained a positive amplification for most of the microsatellites studied for Trichinella strains belonging to different species (T.spiralis, T.britovi). We noticed a size-difference between the amplicons generated by the DNA of various Trichinella species (T.spiralis vs T.britovi).We identify a genetic variability inside the same Trichinella population (T.spiralis), differentiating 3 strains (7.97, 7.42,7.29) by 2 microsatellites (TP43, TP32). For a more detailed analysis of the differences obtained in this study, we plan to use the fluorescently (6-FAM) marked primers, for sequencing and genotyping of the amplification products.

Enzootic Angiostrongyliasis in Shenzhen, China

To the Editor: Angiostrongylus cantonensis is a zoonotic parasite that causes eosinophilic meningitis in humans after they ingest infective larvae in freshwater and terrestrial snails and slugs, paratenic hosts (such as freshwater fish, shrimps, frogs, and crabs), or contaminated vegetables. With the increase of income and living standards, and the pursuit of exotic and delicate foods, populations around the world have seen angiostrongyliasis become an important foodborne parasitic zoonosis (1–9). Shenzhen municipality is situated in the most southern part of mainland People’s Republic of China between the northern latitudes of 22°27′ to 22°52′ and eastern longitudes of 113°46′ to 114°37′; it shares a border with the Hong Kong Special Administrative Region, China, in the south. The climate is subtropical, with an average annual temperature of 23.7°C. The city is 1,952.84 km2 and has a population of 10 million. Since 2006, thirty-two sporadic cases of human eosinophilic meningitis caused by consumption of undercooked aquacultured snails have been documented in Shenzhen (Shenzhen Center for Disease Control and Prevention, unpub. data). To identify the source of these infections and assess the risk for an outbreak of eosinophilic meningitis, we conducted a survey to investigate whether A. cantonensis occurs in wild rats and snails in Shenzhen. To examine A. cantonensis infection in intermediate host snails, 302 terrestrial snails (Achatina fulica) were collected from 10 investigation sites across Shenzhen, and 314 freshwater snails (Pomacea canaliculata)were sampled from 6 investigation sites. We examined the snails for A. cantonensis larvae by using pepsin digestion standardized procedures (3). To survey the prevalence of adult A. cantonensis in definitive host rats, we collected 187 Rattus norvegicus rats and 121 R. flavipectus rats collected from 4 sites where positive snails positive for A. cantonensis were found. These rats were examined for the presence of adult A. cantonensis in their cardiopulmonary systems. A. cantonensis larvae were found in 96 (15.6%) of 616 examined snails. Of these, P. canaliculata had an average infection rate of 20.7% (65/314), significantly higher (p<0.01) than that of A. fulica (10.3%, 31/302), an indication that P. canaliculata may be the principal intermediate host for A. cantonensis in Shenzhen. A. cantonensis adults were recovered from the cardiopulmonary systems of 37 (12%) of 308 examined rats. Infection rate for R. norvegicus rats was 16.6% (31/187), significantly higher (p<0.01) than that for R. flavipectus (4.9%, 6/121), an indication that R. norvegicus may be the principal definitive host for A. cantonensis in Shenzhen, possibly due to the rat’s preference for eating snails. Infection rates were higher for female rats (25.6% for R. norvegicus and 7.8% for R. flavipectus) than for male rats (8.9% for R. norvegicus, 2.9% for R. flavipectus), possibly because female rats eat more snails to supply proteins for reproduction. This report of enzootic A. cantonensis infection in wild rats and snails in Shenzhen demonstrates the existence of natural origins of infection with A. cantonensis for humans in this city. Persons in Shenzhen eat raw or undercooked freshwater and terrestrial snails and slugs. This practice provides opportunities for infection with A. cantonensis, particularly given that P. canaliculata has been aquacultured intensively for human consumption. The prevalence of A. cantonensis in wild rats and snails in Shenzhen poses substantial risk for future outbreaks of human eosinophilic meningitis. Moreover, public health officials, epidemiologists, researchers, clinical technicians, medical practitioners, parasitologists, and veterinarians, as well as the general public, should be aware of such risks, and integrated strategies should be taken to reduce or eliminate such risks.

Transmission risk of human trichinellosis

Trichinella is a food-borne parasitic zoonoses and human cases are still reported in Europe mainly due to the consumption of pig meat originating from small backyard farms. Infections originating from industrialized pig farming have not been reported for decades in Europe, due to control measures to prevent the transmission of Trichinella from wildlife by indoor housing and good management practices. Therefore, risk-based monitoring programs might replace individual carcass control in industrialized pig farming as described in EU legislation SANCO 2075/2005. Transmission of Trichinella species between wildlife and the risk that may pose to humans via consumption of contaminated pork meat has not been studied quantitatively. One pathway by which human trichinellosis can occur is the rat–pig–human route. To evaluate the transmission risk though this pathway the dose responses of rat, pig, and human were studied. Experimental T. spiralis infection was performed in rats with doses of as few as 10 parasites and the data set was analysed using a newly developed dose response model that describes larvae per gram (LPG). Experimental T. spiralis infection in pig was analysed in a similar way. Furthermore nine published outbreaks of human trichinellosis were analysed to determine the dose response in humans. The risk of human trichinellosis via the rat–pig–human transmission was simulated by the Monte Carlo method. A pair of female and male parasites representing the lowest infection pressure from the environment, led to the probability of human trichinellosis by consumption of 100g of raw pork meat equal to 5% via the studied rat–pig–human pathway. In the absence of rodent control near the farm, a low infection pressure from wildlife presents a relatively high risk of human trichinellosis via consumption of uncooked pork meat.

Food-Borne Parasitic Zoonoses: Fish and Plant-Borne Parasites (World Class Parasites)

With >4,000 biomedical journals currently available, and more being added seemingly every month, one of the most overwhelming and daunting tasks for any health professional is to stay current with the literature. A welcomed lifeline has been the World Class Parasites series of publications that have made this challenge much easier to manage. The latest text (Volume 11), Food-Borne Parasitic Zoonoses: Fish and Plant-Borne Parasites, is a superb addition to this series. Murrell and Fried have brought together a stellar group of contributors in a comprehensive and up-to-date review of the helminthic zoonoses that are transmitted through fish and plant consumption. Given that the distribution and effect of these zoonoses remain woefully underappreciated, they are deserving of the justifiable attention brought by this book. The first 9 chapters provide a thorough discussion of intestinal, liver, and lung flukes; fish-borne tapeworms; and tissue nematodes. Two superb chapters on immunologic aspects and molecular epidemiology of these parasites complete the text. There is much to extol in this volume. In an era of justifiable focus on molecular biology and genetics, it is heartening to see the broad-based and integrated approach taken by the editors and collaborators. This approach successfully accomplishes the stated objective of the editors to “… celebrate the diversity of approach that comprises modern parasitological research.” The chapters are clearly written and well organized with a balance of both classic, historic articles as well as important recent work. The editors and authors have obviously made a priority of ensuring that the material is widely accessible to scientists and health professionals in diverse disciplines. They have presented detailed information on the biology, life cycles, natural history, diagnosis, treatment, epidemiology, and control of the agents or infections discussed. Current diagnostic techniques are thoroughly addressed. Insightful discussion is provided at the end of each chapter on current gaps in knowledge and research needs that offers a coherent roadmap for future studies. The chapter on intestinal capillariasis by Cross and Belizario is particularly noteworthy. Abundant images of exceptional quality are included and this adds substantially to the text. More color images would have been of value, but they may have made the text prohibitively expensive. Some chapters could have had additional discussion of epidemiologic aspects and a few typos can be found, but these do not diminish the value of this outstanding work. Food-Borne Parasitic Zoonoses: Fish and Plant-Borne Parasites is a text of exceptional quality that should have broad appeal and utility for health professionals, researchers, medical and public health students, and policy makers. Given the increasing interest in neglected tropical diseases, this book is a timely and commendable work that will promote efforts to reduce the effects of these parasitic agents.

Food-borne parasitic zoonoses in China: perspective for control

Food-borne parasitic zoonoses (FBPZs) cause death and serious diseases in humans and animals worldwide, and are of both public health significance and socioeconomic importance. The FBPZ problem is severe in mainland China, where approximately 150 million people are suffering from FBPZs and more people are at risk. Here, the current status of the FBPZ problem in mainland China is reviewed and strategies and measures for effective control of FBPZs are proposed. Major parasitic zoonoses transmitted through consumption of infected or contaminated meat, fish, plants and/or water will be discussed.

Food-borne parasitic zoonosis: Distribution of trichinosis in Thailand

Trichinosis is among the most common food-borne parasitic zoonoses in Thailand and many outbreaks are reported each year. This paper investigates the distribution of the disease in regions of north, north-east, central and south Thailand. Between the earliest recorded of outbreak of trichinosis in Mae Hong Son Province in 1962 and 2006, there have been 135 outbreaks involving 7340 patients and 97 deaths in Thailand. The highest number of cases, 557, was recorded in 1983. Most infected patients were in the 35-44 year age group, and the disease occurred more frequently in men than women during 1962-2003, with no significant sex difference during 2004-2006. Outbreaks were most common in the northern areas, especially in rural areas where raw and under-cooked pork and/or wild animals are eaten. Human infections occur annually in northern Thailand during communal feasts celebrating the Thai New Year. Trichinosis causes have been reported every year, supporting the need for planning education programs.

Commentary

Spirometra erinaceieuropaei is an important diphyllobothriid cestode whose larval plerocercoid (sparganum) can parasitise humans, causing sparganosis. In China, sparganosis is an important foodborne parasitic zoonosis and poses a serious threat to human health. However, our knowledge of the taxonomic classification of S. erinaceieuropaei and its relationship with other diphyllobothriid cestodes, such as Diphyllobothrium, remains fragmentary. In this study, we determined the complete sequences of cytochrome b (cytb) and cytochrome c oxidase subunit I (cox1) genes from 61 isolates of S. erinaceieuropaei collected from 11 geographical locations in eastern China and compared them to the sequences of Diphyllobothrium species from the GenBank database. Then, we evaluated the genetic variation of S. erinaceieuropaei and the phylogenetic relationship between S. erinaceieuropaei and Diphyllobothrium. Both negative Tajima’s D and Fu’s FS values of neutrality tests and unimodal curve of mismatch distribution analyses supported demographic population expansion. Bayesian skyline plot (BSP) analyses indicated that a population expansion occurred in the Pleistocene. Phylogenetic analysis based on cytb, cox1, and cytb + cox1 under all three methods tested (neighbour-joining, maximum parsimony, and maximum likelihood) suggested that the S. erinaceieuropaei isolates from eastern China and the genus Diphyllobothrium are separate monophyletic groups. Furthermore, the uncorrelated log-normal relaxed molecular-clock model suggested that divergence between Spirometra and Diphyllobothrium began in the late Miocene.

Trichinosis: Epidemiology in Thailand

Trichinosis is one of the most common food-borne parasitic zoonoses in Thailand and many outbreaks are reported each year. This paper reviews the history, species, and epidemiology of the disease and food habits of the people with an emphasis on the north, northeast, central and south regions of Thailand. The earliest record of trichinosis in Thailand was in 1962 in the Mae Sariang District, Mae Hong Son Province. Since then, about 130 outbreaks have been reported involving 7392 patients and 97 deaths (1962-2005). The highest number of cases, 557, was recorded in 1983. The annual epidemiological surveillance reports of the Bureau of Epidemiology, Department of Disease Control, Ministry of Public Health, Thailand, show that trichinosis cases increased from 61 in 1997 to 351 in 1998. In contrast to these figures, the number of reported cases decreased to 16 in 1999 and 128 cases in 2000. There was no record of trichinosis in 2001, but then the figures for 2002, 2003 and 2004 were 289, 126 and 212 respectively. The infected patients were mostly in the 35-44 years age group and the disease occurred more frequently in men than women at a ratio of 1.7-2.0:1. There were 84 reported cases of trichinosis in Chiang Rai, Nan, Chiang Mai, Si Sa ket, Nakhon Phanom, Kalasin, Nakhon Ratchasima, Nakhon Nayok, Nakhon Pathom and Surat Thani, provinces located in different parts of Thailand in 2005. The outbreaks were more common in the northern areas, especially in rural areas where people ate raw or under-cooked pork and/or wild animals. This indicates the need for health education programs to prevent and control trichinosis as soon as possible in the high-risk areas.

Taeniasis, cysticercosis and echinococcosis in Thailand

Taeniasis is one of the major food-borne parasitic zoonoses in Thailand. During the years 1957–1997, the prevalence was low in most parts of the country. Recent (2000–2005) country prevalence was lower than 1%. A high prevalence (5.9%) was found among 1450 villagers from 30 villages in the North, and among 1233 stool samples from 19 provinces in the Northeast (2.8%). Taenia saginata was the dominant species. Cysticercosis in Thailand is somewhat under-reported/recorded. During the period 1965–2005, diagnosis was based on techniques other than serodiagnosis, giving a total of cysticercosis cases of less than 500. However, an immunoblot technique using delipidized cyst antigen showed 314 positive cases out of 754 samples tested in 2000–2005. Reports of neurocysticercosis appeared more often than cutaneous cysticercosis. A total of 24 cases of echinococcosis, mostly hydatid cysts (only 2 cases of alveolar cysts), were recorded during 1936–2005. These records included 3 cases of foreigners seeking surgery in hospitals in Bangkok. Most Thai patients were migrant workers from the Middle East, and only a few cases were indigenous. The prevalence of cysticercosis and echinococcosis is increasing resulting from sensitive modern diagnostic tests. Taeniasis will persist in Thailand as the consumption of raw/half-cooked meat dishes is still a normal practice for Thai people.

Southeast Asian tropical medicine and parasitology network

The SEAMEO TROPMED Network is a regional cooperative network established in 1967 for education, training and research in tropical medicine and public health under the Southeast Asia Ministers of Education Organization. The Network operates through four Regional Centers with respective areas of specialization and host institutions: Community Nutrition/Tropmed Indonesia; Microbiology, Parasitology and Entomology/Tropmed Malaysia; Public Health/Tropmed Philippines; and Tropical Medicine/Tropmed Thailand. To train health workers, to support research on endemic and newly emerging diseases, and to advocate relevant health policies are the main functions of these centers. SEAMEO TROPMED Network in collaboration with the Faculty of Tropical Medicine, Mahidol University and other institutions has regularly organized the Seminar on Food-borne Parasitic Zoonoses every 3–5 years over the past 15 years. The Faculty of Tropical Medicine has organized the annual Joint International Tropical Medicine Meeting since 1996. Full papers of the presentations at these two meetings have been published as supplementary issues to the Southeast Asian Journal of Tropical Medicine and Public Health, an in-house journal of SEAMEO TROPMED Network. Recently, the Parasitology Association of ASEAN Countries has rotated the hosting of the ASEAN Congress of Parasitology and Tropical Medicine. These institutional and conference networks will enable closer links, to promote the health of people in the Southeast Asian region.

Sushi Delights and Parasites: The Risk of Fishborne and Foodborne Parasitic Zoonoses in Asia

Because of the worldwide popularization of Japanese cuisine, the traditional Japanese fish dishes sushi and sashimi that are served in Japanese restaurants and sushi bars have been suspected of causing fishborne parasitic zoonoses, especially anisakiasis. In addition, an array of freshwater and brackish-water fish and wild animal meats, which are important sources of infection with zoonotic parasites, are served as sushi and sashimi in rural areas of Japan. Such fishborne and foodborne parasitic zoonoses are also endemic in many Asian countries that have related traditional cooking styles. Despite the recent increase in the number of travelers to areas where these zoonoses are endemic, travelers and even infectious disease specialists are unaware of the risk of infection associated with eating exotic ethnic dishes. The aim of this review is to provide practical background information regarding representative fishborne and foodborne parasitic zoonoses endemic in Asian countries.

Fasciolopsiasis: is it a controllable food-borne disease?

Fasciolopsiasis, endemic to the Orient and Southeast Asia, is a snail-transmitted, intestinal, food-borne parasitic zoonosis caused by a trematode, Fasciolopsis buski, which also infects farm pigs. Fasciolopsiasis remains a public health problem despite changes in eating habits, alterations in social and agricultural practices, health education, industrialization, and environmental alterations. The disease occurs focally and is most prevalent in school-age children. In foci of parasite transmission, the prevalence of infection in children ranges from 57% in mainland China to 25% in Taiwan and from 50% in Bangladesh and 60% in India to 10% in Thailand. Control programs implemented for food-borne zoonoses are not fully successful for fasciolopsiasis because of century-old traditions of eating raw aquatic plants and using untreated water. Fasciolopsiasis is aggravated by social and economic factors such as poverty, malnutrition, an explosively growing free-food market, a lack of sufficient food inspection and sanitation, other helminthiases, and declining economic conditions.

Human gnathostomosis in Spain: first report in humans

Gnathostomosis has been known since 1836, when the parasite was discovered in the stomach of a tiger in London Zoo. Today it is considered an important food-borne parasitic zoonosis, endemic mainly in Asian countries where some people prefer to eat raw fish, amphibians or reptiles. In its mammal definitive host the adults are located in the stomach wall, even in granulomes. The eggs leave the definitive host with the faeces and develop further in an aquatic environment. Larva 1, mobile, is ingested by a copepod, in which it evolves to immature larva 3. The larvae become infectious for mammals in a second intermediary non-specific host, which ingest the copepod. These may be a number of crustaceans, cold-blooded vertebrates, birds or mammals. The infective larva can pass from one host to another within different food chains of the biotope in question. Maturation to the adult stages takes place only in the definitive specific hosts (canids and felids in G. spinigerum). It is a slow process of some 6.5 months in duration. This is due to a migration followed by the infectious larval stage, which involves: perforation of the gastric wall, entry into the liver, migration to muscles and connective tissues, and, again, perforation of the gastric wall from the outside in order to reach its final destination. This internal migration often leads to ectopic locations, especially in uncommon hosts, such as humans, where Gnathostoma larvae are not able to reach sexual maturity. The most dangerous locations are the brain and spinal cord, while others include the eye, lung, pleura, urinary tract and intestine (Oriel and Ash, 1994). In some patients with eosinophilic myeloencephalitis, G. spinigerum has been found in the eyes, suggesting a possible migration via the optic nerve. External gnathostomosis usually comes from the therapeutic application of reptile or amphibian flesh or the manipulation of raw meat. Most human cases, both external (cutaneous migration) and internal (visceral migration), have been diagnosed in Thailand and Japan, or in * Corresponding author. Present address: Departamento de Parasitologia, Facultad de Ciencias, Universidad de Granada, E-18071, Granada, Spain. Tel.: +34-58-243263; fax: +34-58243174. E-mail address: cmascaro@goliat.ugr.es (C. Mascaro).

Detection of parasites in food.

The importance of foodborne parasitic zoonoses remains high in many regions of the world. Although control efforts have been exerted for quite some time, overall progress has not been satisfactory, even in many well developed countries. An important drawback in control programmes for parasites such as Trichinella, Toxoplasma and Taenia has been the absence of rapid, accurate and sensitive diagnostic tests for these meatborne parasites. However, the rapid advances in the molecular biology of these organisms has yielded concomitant gains in precision of detection. This review highlights these advances and their impact or potential application to the control of foodborne parasites.

Short report: gnathostomiasis in Mexico.

Gnathostomiasis is an important food-borne parasitic zoonosis that is endemic mainly in Asian countries where some people prefer to eat raw freshwater fish. In North America, the first recorded case of gnathostomiasis was in Mexico in 1970, and the numbers of gnathostomiasis patients in Mexico seems to be increasing dramatically with time. However, the epidemiology of this disease in Mexico has never been described in detail. Here we review the current status of gnathostomiasis in Mexico.

Parasites associated with exotic food

The short description of parasites associated with “exotic food” is by no means inclusive. Many others, such as Toxoplasma gondii, Spirometa spp. (sparganosis), Taenia saginata (cysticercosis), and Echinostoma malayanum, are transmitted via food. Raw sheep liver “sowda” is commonly consumed in Lebanon. Many people developed human toxocariasis after eating this dish (19). The economic loss associated with food-borne parasitic zoonoses is of significant consequence. The estimated impact of Opisthorchis viverrini infection in northern Thailand alone is estimated at 120 million U.S. dollars. Medical costs in the U.S. associated with trichinellosis alone are estimated at 1.5 to 2 million dollars annually (20). in addition to the economic impact of these parasites, significant morbidity and mortality can occur. Also the discomfort and presence of worms migrating through the body is certainly distressful. However, to completely avoid many, if not all, parasitic infections, thoroughly cook all food before ingestion. In addition, if the fish or meat has been frozen, then the larvae could be killed.

Food-borne parasitoses in Malaysia epidemiological assessment and research needs.

Food-borne parasitic zoonoses have emerged as a major public health problem in many countries and are posing a medical challenge. They are not only important from the economic point of view but also because of their severe sequelae. In Malaysia, these parasitoses are a tip of an iceberg problem. The article documents all the food-borne parasitic zoonoses reported in Malaysia. An epidemiological assessment of the diseases with research needs is highlighted.

Emerging problems in seafood-borne parasitic zoonoses: Jeffrey W. Brier summarizes reports presented at the First International Conference on Foodborne Parasitic Zoonoses, Chiang Mai, Thailand

The First International Conference on Foodborne Parasitic Zoonoses, 14–17 November 1990, at Chiang Mai University in Chiang Mai, Thailand, was organized by the Southeast Asian Ministers of Education as their thirty-third seminar entitled Emerging Problems in Foodborne Parasitic Zoonosis: Impact on Agriculture and Human Health. It was attended by 120 representatives of 26 countries. The major objectives of the conference were to assess the current status of foodborne parasitic illness throughout the world, to describe current research activities in foodborne parasitic zoonoses, to discuss the impact of zoonotic and other foodborne parasitic illnesses on economics and industry, and to establish collaborative research efforts between conference attendees with similar interests. This article summarizes reports presented at the conference which relate specifically to seafood-borne parasitic zoonoses.