This review addresses the biodiversity, biology, distribution, ecology, epidemiology, and consumer health significance of the so far known species of Anisakis, both in their natural hosts and in human accidental host populations, worldwide. These key aspects of the Anisakis species' biology are highlighted, since we consider them as main driving forces behind which most of the research in this field has been carried out over the past decade. From a public health perspective, the human disease caused by Anisakis species (anisakiasis) appears to be considerably underreported and underestimated in many countries or regions around the globe. Indeed, when considering the importance of marine fish species as part of the everyday diet in many coastal communities around the globe, there still exist significant knowledge gaps as to local epidemiological and ecological drivers of the transmission of Anisakis spp. to humans. We further identify some key knowledge gaps related to Anisakis species epidemiology in both natural and accidental hosts, to be filled in light of new 'omic' technologies yet to be fully developed. Moreover, we suggest that future Anisakis research takes a 'holistic' approach by integrating genetic, ecological, immunobiological, and environmental factors, thus allowing proper assessment of the epidemiology of Anisakis spp. in their natural hosts, in human populations, and in the marine ecosystem, in both space and time.

Molecular Epidemiology of Anisakis and Anisakiasis: An Ecological and Evolutionary Road Map.

We present the first human case of anisakidosis acquired from eating locally caught fish in Australia. A 41-year-old woman experienced gastrointestinal pain, vomiting and diarrhoea of increasing severity over 3 weeks. All symptoms resolved spontaneously after a worm was passed in her faeces. Microscopic examination showed that it was a Contracaecum species larva of the family Anisakidae. Anisakidosis should be considered in patients with gastrointestinal symptoms who have recently eaten seafood.

First report of human anisakidosis in Australia.

Effects of anisakid nematodes Anisakis simplex (s.l.), Pseudoterranova decipiens (s.l.) and Contracaecum osculatum (s.l.) on fish and consumer health ☆

Anisakiasis is one of the most common fishborne helminthic diseases in Japan, which is contracted by ingesting the larvae of the nematode Anisakis spp. carried by marine fish. Anisakis simplex sensu stricto (s.s.) and A. pegreffii are the dominant species in fish caught offshore Japan. The present study aimed to identify the anisakid species infecting Japanese patients and determine whether there is any difference in the pathogenetic potential of A. simplex (s.s.) and A. pegreffii. In total, 41 and 301 Anisakis larvae were isolated from Japanese patients and chub mackerel (Scomber japonicus), respectively; these were subjected to molecular identification using polymerase chain reaction targeted at a ribosomal DNA internal transcribed spacer region. Chub mackerel larvae were further examined for survival in artificial gastric juice (pH 1.8) for 7 days and for invasiveness on 0.75% solid agar over a 24-h interval. All clinical isolates, including those of asymptomatic, acute, and chronic infections as well as those from the stomach, small intestine, colon, and stool, were identified as A. simplex (s.s.). Chub mackerel harbored A. simplex (s.s.) and A. pegreffii larvae, together with a few larvae of other anisakid species. A. simplex (s.s.) larvae from chub mackerel tolerated the artificial gastric juice better than A. pegreffii, with 50% mortality in 2.6 and 1.4 days, respectively. In addition, A. simplex (s.s.) penetrated the agar at significantly higher rates than A. pegreffii. These results show that A. simplex (s.s.) larvae have the potential to survive acidic gastric juice to some extent and penetrate the stomach, small intestine, or colon in infected humans.

Anisakis simplex sensu stricto and Anisakis pegreffii: Biological Characteristics and Pathogenetic Potential in Human Anisakiasis

Foodborne anisakiasis and allergy.

Risk factors for human Anisakis infection and association between the geographic origins of Scomber japonicus and anisakid nematodes.

Morphological and molecular characterization of Anisakis larvae (Nematoda: Anisakidae) in Beryx splendens from Japanese waters.

Detection rate of diarrhoea-causing Kudoa hexapunctata in Pacific bluefin tuna Thunnus orientalis from Japanese waters.

Kudoa hexapunctata n. sp. (Myxozoa: Multivalvulida) from the somatic muscle of Pacific bluefin tuna Thunnus orientalis and re-description of K. neothunni in yellowfin tuna T. albacares

Human Sarcocystis infections are known to be caused by the ingestion of raw or undercooked beef or pork containing mature sarcocysts of Sarcocystis hominis or S. suihominis, respectively. In addition, several cases of parasitic food poisoning in Japan have recently been reported after consumption of raw horsemeat containing sarcocysts of S. fayeri. In this study, the presence of sarcocysts in 28 horsemeat and 121 beef samples collected in Tokyo was investigated. Sarcocysts of S. fayeri were found in 16 horsemeat samples. Sarcocysts of S. hominis were not detected in beef samples, while sarcocysts of S. cruzi were detected in 60 beef samples. In addition, S. hirsuta and S. bovini were isolated only from New Zealand beef samples. Bradyzoites in sarcocysts collected from 62/73 sarcocyst-positive refrigerated horsemeat and beef samples were determined to be viable. Molecular analysis of S. fayeri 18S rRNA gene sequences revealed that intraspecific variation among eight individual bradyzoites from a single sarcocyst was as high as 9.8%. In contrast, mitochondrial cytochrome c oxidase subunit 1 (mtDNA cox1) gene sequences from the six fragments of a single sarcocyst were 100% identical. Sarcocysts of S. bovini isolated from beef also exhibited intraspecific variation in 18S rRNA gene sequences and had to be cloned before sequencing, while mtDNA cox1 gene sequences were obtained by direct sequencing. Therefore, we conclude that molecular analysis of the mtDNA cox1 gene is the most useful for identification of Sarcocystis species. This study provides the first published partial sequence of the S. fayeri mtDNA cox1 gene.

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Jun Suzuki

Papers

Risk factors for human Anisakis infection and association between the geographic origins of Scomber japonicus and anisakid nematodes.

Morphological and molecular characterization of Anisakis larvae (Nematoda: Anisakidae) in Beryx splendens from Japanese waters.

Detection rate of diarrhoea-causing Kudoa hexapunctata in Pacific bluefin tuna Thunnus orientalis from Japanese waters.

Kudoa hexapunctata n. sp. (Myxozoa: Multivalvulida) from the somatic muscle of Pacific bluefin tuna Thunnus orientalis and re-description of K. neothunni in yellowfin tuna T. albacares

Molecular identification and characterization of Sarcocystis spp. in horsemeat and beef marketed in Japan.