Risk of Anisakidosis related to Fish consumption

Risk of Anisakidosis related 

to Fish consumption 

Stefano D’Amelio 

Parasitology Section, Dept. of Sciences of Public Health, Sapienza University 

of Rome, Italy

Anisakids are of medical and 

economic significance. Larval 

forms of anisakid nematodes of 

the genera Anisakis Dujardin, 

1845 and Pseudoterranova 

Mozgovoi, 1951 are in fact the 

principal aethiological agents of 

human anisakidosis.

This fish-borne zoonosis occurs 

when the larvae are taken alive 

after the consumption of raw, 

undercooked or improperly 

processed fish or cephalopods 

that serve as paratenic hosts in 

the life cycle of these 

nematodes.

Human anisakidosis is becoming of 

major health and economic 

importance and it is particular 

relevant in countries, such as Japan, 

where the number of human cases 

reach significant peaks owing to the 

widespread custom of eating 

preparations based on raw fish, such 

as sushi and sashimi. Human cases 

are increasingly reported from United 

States and many European countries.

Life cycles 

Anisakids are ascaridoid nematodes dependent upon 

aquatic hosts for the completion of their life history, 

which generally involves an array of invertebrates 

and fish as intermediate or paratenic hosts, and 

marine mammals or fish-eating birds, reptiles and 

fishes as definitive hosts.

A simple life cycle?

A complicated life-cycle? 

Anisakid nematodes are 

heteroxenous and their life 

cycles involve small 

crustaceans as first 

intermediate or paratenic 

hosts, where maybe second 

stage larvae (L2) mutate to 

L3, thus becoming 

potentially infective to their 

definitive hosts. According 

to new studies, anisakids 

reach the third stage within 

the egg. 

From Abollo, 1999.

Calanus finmarchicus 

Paraeuchaeta norvegica 

A study on 

Maurolicus muelleri

A very complicated life-cycle! 

? 

? 

?

The life cycle of 

Pseudoterranova decipiens s.

Parasite biomass in the life cycle 

of Anisakis and Pseudoterranova 

P = 100% 

I = up to 10,000 

P = 50-80% 

I = up to 200 

P = 2-20% 

I = up to 5-10 

P = 0.2% 

I = 1 

marine mammals - 

definitive host 

large fishes/cephalopods - 

paratenic host 

small fishes - paratenic host 

crustacean - intermediate hos

Epizootiology 

Anisakid larvae have been detected worldwide in a large 

variety of fish species. Among teleosts, they have been 

found in Gadiformes, Perciformes, Clupeiformes, 

Pleuronectiformes, Scorpaeniformes, Zeiformes, 

Bericiformes, Lophiiformes, Anguilliformes and 

Atheriniformes.

Third stage larvae of anisakids are commonly found in the 

flesh and the body cavity of a large number of fishes as 

well as in cephalopods that serve as paratenic hosts. 

From aquatic.unizar.es/n3/art1401/anisakis.htm

Anisakis sp. larva in the 

flesh of blue whiting 

(Micromesistius poutassou) 

after light candling 

(from www.usc.es/banim/doc/tppanisa.htm)

Anisakid larvae have been also detected in elasmobranchs 

and in a variety of cephalopods. Among these, they have 

been found in Octopodidae, Sepiidae, Loliginidae and 

Ommastrephidae.

Adult forms of Anisakis spp. are usually found in cetaceans 

(whales and dolphins). Pseudoterranova spp. matures mainly 

in pinnipeds (phocids and otariids). Some members of the 

genus Contracaecum reach maturity in pinnipeds, others in 

fish-eating birds (e.g cormorants, pelecans and herons). 

Phocascaris species become adults in pinnipeds of the 

northern hemisphere.

Histopathology 

Histopathological studies in 

fish revealed damages mostly 

at the level of stomach wall, 

liver, gonads and muscles. 

These includes mechanical 

damages, necrosis, tissue 

compression and castration. 

Clinical signs in fishes are 

mainly cellular infiltration, 

and hemorrhage. 

From Abollo, 1999.

Histopathological studies in 

cephalopods revealed 

damages mostly at the level 

of stomach wall, mantle 

muscle, nidamentary 

glands, testicle and ovary. 

These includes mechanical 

damages, necrosis, tissue 

compression and castration. 

Cellular infiltration is often 

found associated to 

encapsulated larvae. 

From Abollo et al., 1998.

In the stomach of cetaceans, 

anisakid adults are often 

found in clusters of 

individuals embedded in the 

mucosa and submucosa. 

Ulcers of 5x3 cm sized 

associated to anisakids are 

found in the fundic portion of 

the stomach. From Abollo et al., 1998.

Taxonomy 

Eukaryota 

Metazoa 

Nematoda 

Secernentea 

Ascaridida 

Ascaridoidea 

Anisakidae 

The most frequently recovered anisakid species in fish 

belong to the following genera: 

Anisakis, Pseudoterranova, Contracaecum, Phocascaris

Anisakid larvae can 

be identified at 

genus level by light 

microscopy, mainly 

on the basis of the 

morphology of 

digestive tract and 

of excretory system. 

A-C Pseudoterranova decipiens; D-F Anisakis sp.; G-I Hysterothylacium 

aduncum; J-L Contracaecum rudolphii. (From Anderson, 2000)

The taxonomy of anisakids is mainly based on the 

morphology of male adult specimens. The most 

significant structural characters for species 

identification are the distribution and pattern of caudal 

papillae, the spiculae and the morphology of cephalic 

end (Fagerholm, 1991). 

From Abollo et al., 1998.

However, anisakid nematodes tend to be very 

conserved in gross morphology and molecular 

techniques have shown that many presumed 

monospecific species consists of several cryptic 

species (Nascetti et al., 1993; Paggi et al., 1991; 

Orecchia et al., 1994; Mattiucci et al., 1997). 

Molecular markers in the ribosomal DNA spacers 

have been recently established for the correct 

identification of Anisakis cryptic and 

morphospecies, irrespective of their sex or life 

history stage (D’Amelio et al., 2000)

Species of Anisakis (two main clusters) 

One corresponding to larvae Type I (7 species) 

A. simplex (s.s). 

A. pegreffii 

A. simplex C 

A. ziphidarum 

Anisakis sp. A (sensu Pontes et al 2005) 

corresponding to Anisakis sp. (sensu Valentini et al 2006) 

A. typica 

A. schupakovi 

The other corresponding to larvae Type II (3 species) 

A. physeteris 

A. brevispiculata 

A. paggiae

Anisakis simplex s.s. 

• mainly in the North Atlantic and North 

Pacific Oceans 

• found frequently in Balaenoptera 

acutorostrata, Delphinus delphis, 

Globicephala melaena, Lagenorhynchus 

albirostris, Orcinus orca, Stenella 

coeruleoalba (rare), Phocoena phocoena,

Anisakis pegreffii 

• mainly in the Mediterranean Sea and the 

South Atlantic Ocean 

• found frequently in Delphinus delphis, 

Ziphius cavirostris, Tursiops truncatus

Anisakis simplex C 

• mainly in the South Atlantic and North 

Pacific Oceans 

• found frequently in Pseudorca crassidens, 

Ziphius cavirostris

Anisakis ziphidarum 

• mainly in the Mediterranean Sea and the 

South Atlantic Ocean 

• found frequently in Mesoplodon layardii, 

Mesoplodon mirus, Ziphius cavirostris all 

of them members of the family Ziphiidae

Anisakis sp. A (sensu Pontes et al. 

2005) 

• from the coasts of Madeira and Galicia 

• found in Mesoplodon densirostris

Anisakis typica 

• mainly from warm/temperate waters of the 

Atlantic Ocean 

• found in Sotalia fluviatilis, Stenella 

coeruleoalba, Stenella attenuata, Stenella 

longirostris, Steno bredanensis, 

Lagenodelphis hosei

Anisakis physeteris 

• mainly in the Mediterranean and the 


• found frequently in Kogia breviceps, Kogia 

sima, Physeter macrocephalus, rarely in 

Ziphius cavirostris

Anisakis brevispiculata 

• mainly in the Mediterranean and the central 



sima, Physeter macrocephalus

Anisakis paggiae 

• mainly in the central Atlantic Ocean 


sima,

Anisakis schupakovi 

• endemic to the Caspian Sea 

• found only in Phoca caspica

The identification of anisakid nematodes can be performed 

by morphological study and by genetic characterisation by 

PCR-RFLP analysis. The genomic region of the ribosomal 

DNA spanning the ITS-1, the 5.8S and the ITS-2 is 

amplified by PCR. Amplicons are subjected to restriction 

analysis using those endonucleases that provides 

diagnostic patterns in anisakids.

HhaI 

HinfI 

TaqI 

1 2 3 4 5 6 7 L 

1 2 3 4 5 6 7 L 

1 2 3 4 5 6 7 L 

< 500bp 

< 500bp 

< 500bp 

1 A.pegreffii 

2 A.simplex s.s. 

3 A.simplex C 

4 A.physeteris 

5 A.schupakovi 

6 A.ziphidarum 

7 A.typica 

L 100 bp ladder

Species of Pseudoterranova 

Five members of the Pseudoterranova decipiens complex 

P. krabbei, 

P. decipiens (s.s.) 

P. bulbosa, 

P. azarasi 

P. decipiens E 

P. cattani 

P. ceticola 

P. kogiae

Pseudoterranova krabbei 

• mainly from the coasts of Scotland, 

Norway, Iceland 

• found frequently in Halichoerus grypus

Pseudoterranova decipiens s.s. 

• mainly from the coasts of Scotland, 

Norway, Iceland, but also in Pacific Canada 

and Japan 

• found frequently in Phoca vitulina

Pseudoterranova bulbosa 

• mainly from the coasts of North Norway, 

Iceland and Greenland but also in Northern 

Pacific Canada and Japan 

• found frequently in Erignathus barbatus

Pseudoterranova azarasi 

• mainly from the coasts of Japan 

• found frequently in Eumetopias jubatus but 

also in Erignathus barbatus

Pseudoterranova decipiens E 

• mainly from the coasts of the Antarctica 

• found frequently in Leptonychotes weddelli

Pseudoterranova cattani 

• mainly from the Pacific coasts of South 

America 

• found frequently in Otaria byronia

Pseudoterranova kogiae and P. 

ceticola 

• mainly from the Gulf of Mexico and 

adjacent waters 

• found in Kogia sima, Kogia breviceps

The species of 

Pseudoterranova 

can be 

distinguished by 

SSCP analysis

Anisakis in fish (paratenic hosts) and 

marine mammals (definitive hosts) 

Results from a large survey carried 

out by Lia Paggi and collaborators

Prevalence, abundance and intensity of Anisakis spp. in the Mediterranean 

Sea

Prevalence, abundance and intensity of Anisakis pegreffii in the Southern 

Atlantic Ocean

Prevalence, abundance and intensity of Anisakis simplex s.s. in the Northern 

Atlantic Ocean

Prevalence, abundance and intensity of Anisakis simplex s.s. in the Northern 

Pacific Ocean

arine mammalsasdefinitive hostsforAnisakis spp.

Portugal 

(Marquez et al., 2006)

Portugal 

(Marquez et al., 2006)

Portugal 

revalence, intensity and abundance of anisakid larvae in Pagellus 

ogaraveo, relative to fish length, from Madeiran waters. (Costa et 

., 2004) 

Length 

class 

(cm) 

≤ 25 

25-35 

≥ 35 

n fish 

examined 

16 

34 

27 

n. 

infected 

fish 

13 

30 

26 

Prevalence 

(%) 

81.3 

88.2 

96.3 

n parasites 

(min-max.) 

47 (1-10) 

144 (1-36) 

90 (1-17) 

Mean 

Intensity 

±S.E. 

3.6 ±0.8 

4.8±2.0 

3.5 ±0.8 

Abundance 

±S.E. 

2.9 ±0.7 

4.2 ± 1.2 

3.3 ± 0.7

Portugal 

gain from Madeiran waters. (Costa et al., 2003) 

Host species 

Aphanopus 

carbo 

Scomber 

japonicus 

Trachurus 

picturatus 

n fish 

examined 

142 

150 

40 

Prevalence 

(%) 

97.2 

69.5 

62.5 

Mean Intensity 

69.6 

2.6 

2.5

Spain 

Abollo et al, 2001

VIGO 

PENICHE 

LASTRES ZUMAIA 

CADIZ 

SAMPLING 

MALAGA 

MOTRIL 

ALMUÑECAR

HinfI 

RG AP AS L 

RG: recombinant genotype 

AP: Anisakis pegreffii 

AS: Anisakis simplex s.s. 

L: 100 bp ladder

A. pegreffii 

A. simplex s.s. 

Recombinant genotype

. simplex s.s.: 84.0% 

. pegreffii: 4.0% 

ecombinant: 12.0% 

VIGO 

A. simplex s.s.: 62.0% 

A. pegreffii: 38.0% 

Recombinant: 0.0% 

PENICHE 




simplex s.s.: 12.5% 

pegreffii: 66.7% 

combinant: 20.8% 

LASTRES 

CADIZ 

ZUMAIA 

ALBORAN 

SEA 






Recombinant: 21.4%

Anisakis in Phycis from Andalucia

Anisakis in Phycis from Tunisia

Poland 

Two subspecies of herring from the Baltic Sea 

Clupea harengus membras (Baltic endemic subspecies) 

Clupea harengus harengus (spring-spawning migrations) 

Data on Anisakis spp. show that Baltic endemic herrings 

are virtually Anisakis-free, and that the risk is related to 

herrings migrating from the North Sea 

Multilocus allozymes provided data that support this 

hypothesis (Mattiucci et al., 1989).

Poland 

Analysis of Anisakis spp. from two geographically 

distinct areas (Western Baltic and Irish Sea) has 

found a total of eight polymorphic sites over a 250 

base sequence of the CO1 region. Three haplotypes 

were identified from Irish Sea parasites and six 

haplotypes from the Western Baltic samples. 

Geographical 

Region 

Poly Poly morp hic sites 

(nucleotide p ositions) 

Haplotype 88 89 94 115 140 182 201 243 

Irish sea A T T T C T C C C 

Irish sea B T T T T T C T C 

Irish sea C C T T T C C C C 

B altic sea D C C T C T C T C 

B altic sea E C T T C T C C C 

B altic sea F C T T T T T C C 

B altic sea G C T T T T C C A 

B altic sea H T T T T T C C C 

B altic sea I C T C T T C C C

Anisakids from Mexico 

(fish used for “cebiche”) 

ata from Laffon Leal et al., 2000 

Host species 

Epinephelus 

morio 

Sphyraena 

barracuda 

Gerres 

cinereus 

Prevalence 

(%) 

83 

33 

57 

Contracaecum spp. 

Mean Intensity 

6.5 

10.2 

7.6

Clinically, several different types of human anisakidosis have 

been defined based on the location (gastric, intestinal or 

extra-gastrointestinal) (Ohtaki and Ohtaki, 1989; Ishikura, 

1990; Yoshimura, 1990) and on histopathological 

classification (Kojima et al., 1966).

Gastric anisakidosis is characterized by a selflimited, 

self-healing episode of intense 

epigastralgia, nausea, and vomiting 2 to 5 hours 

after ingestion of raw fish. 

Endoscopic removal of the larvae is curative. 

Diagnosis of gastric anisakidosis can be made 

based on morphology of the whole worm when 

expectorated by the patient or after endoscopic 

removal.

Gastroendoscopic image showing a Anisakis larva 

extracted from the gastric tract of a 51 year old 

woman in Southern Italy (D’Amelio et al., 1999)

Section of Anisakis larva in the ileum of a patient. 

(From http://www.stanford.edu/class/humbio103/parasitepages/ParaSites/anisakiasis/Diag.html)

Intestinal anisakiosis presents as low abdominal pain. 

Intestinal anisakiosis is extremely difficult to diagnose 

clinically because of the nonspecificity of the symptoms. 

In fact, the majority of cases are initially misdiagnosed as 

appendicitis, acute abdominal syndrome, cancer (gastric 

or intestinal), ileitis including Crohn disease, or 

tuberculous peritonitis. 

A history of raw marine fish ingestion is the most 

important clinical feature, and anisakiosis should be 

considered in anyone with a history of ingestion of raw 

marine fish and abdominal pain. Peripheral eosinophilia 

may be observed but it is not specific.

Cross section through the intestinal region of the nematode. 

Note the external cuticle (C) overlying a celomyarian and 

polymyarian muscle layer (M), lateral epidermal cords 

(LEC), and the digestive tract (DT) with a single layer of 

columnar epithelial cells determining a central tripartite

Recently, larval forms of A. simplex have 

been identified as responsable of IgEmediated 

allergic reactions, with 

symptoms ranging from urticaria, to 

asthma up to anaphylactic shock 

(Audicana et al., 2002). 

umber of papers in Pubmed 

ter a search under “Anisakis 

lergy” 

18 

16 

14 

12 

10 

8 

6 

4 

2 

0 

2000 2001 2002 2003 2004 2005 2006

Which treatment for make the larvae 

not harmful? 

• Heat (recommended at least 66°C, but … 

• Freezing (24h at -20°C) 

• Acid treatment 

• Salt, vinegar, smoke

Which treatment for make the larvae 

not harmful? 

• FDA recommends that all fish and shellfish 

intended for raw (or semiraw such as 

marinated or partly cooked) consumption be 

blast frozen to -35°C or below for 15 hours, 

or be regularly frozen to -20°C or below for 

7 days.

In the samples where the temperature rises (heat and 

microwaves), the surface of the parasites shows 

disrupted zones where the cuticle is damaged. 

Live larvae with a damaged cuticle may be 

susceptible to the action of enzymes and acid 

conditions of the gastric solutions when consumed, 

with the result of fragmentation and dissolution of 

the larvae and its death, before the attachment to and 

penetration of the mucosa (1). In this case, no 

anisakiasis occurs when the larva is ingested. 

However, the allergic response in sensitized 

individuals may increase due to the release of 

somatic allergens, some of them heat and pepsin 

resistant, which are not protected by the cuticle from 

the gastric juices. This would explain the cases of 

allergy in patients sensitized to Anisakis after the 

ingestion of well-cooked canned

Anisakis and Pseudoterranova 

• A nice model study? 

• A useful tool? 

only a risk?


a model study 

• Population genetics 

• Detection of sibling species 

• Detection of an hybrid zone 

• Host-parasite coevolution

0.02 

85 

100 

94 

100 

79 

29A.brevispiculata 

58 A.brevispiculata 

100 A. brevispiculata 

A. brevispiculata 

67A. 

brevispiculata 

A.physeteris 

100 A.physeteris 

A.paggiae 

100A.paggiae 

80 P.ceticola 

P.ceticola 

85 P.ceticola 

66 P.ceticola 

Anisakis sp from madeira 

A.ziphidarum 

50 A.simplexC 

A.simplexs.s. 

100 A.pegreffii 

67 A.pegreffii 

A.typica 

A.typica 

85 A.typica 

A.typica 

56 A.typica 

Atypica 

A.typica 

Sperm whales 

Kogia and Physeter 

Beaked whales 

Baleen whales 

and dolphins 

Dolphins


a model study 

• Anisakis species as indicators of fish stock 

biology

Mattiucci et al., 2004

References: 

Abollo E (1999). Anisaquidos en aguas de Galicia: del gen al ecosistema (PhD Thesis, Universidade de Vigo) 

Abollo E, Gestal C, Lopez A, Gonzalez A, Guerra A, Pascual S (1998). Squids as trophic bridges for parasite flow within marine 

ecosystems: the case of Anisakis simplex (Nematoda: Anisakidae) or when the wrong way can be right. In Payne AIL, Lipinsky MR, 

Clarke MR, Roeleveld MAC eds. S Afr J Mar Sci 20: 207-223 

Anderson RC (2000). Nematode parasites of vertebrates, their development and transmission. CABI Publishing 

Audicana MT, Ansotegui IJ, Fernandez de Corres L, Kennedy MW (2002). Anisakis simplex: dangerous - dead and alive? Trends 

Parasitol 18: 20-25. 

D’Amelio S, Mathiopoulos KD, Brandonisio O, Lucarelli G, Doronzo F, Paggi L (1999). Diagnosis of a case of gastric anisakidosis by 

PCR-based restriction fragment length polymorphism analysis. Parassitologia 41: 591-593. 

D’Amelio S, Mathiopoulos KD, Santos CP, Pugachev ON, Webb SC, Picanço M, Paggi L (2000). Genetic markers in ribosomal DNA 

for the identification of members of the genus Anisakis (Nematoda: Ascaridoidea) defined by PCR-based RFLP. Int J Parasitol 30 (2): 

223-226. 

Fagerholm, HP (1991). Systematic implications of male caudal morphology in ascaridoid nematode parasites. Syst Parasitol 19: 215- 

228 

Ishikura H (1990). Clinical Features of Intestinal Anisakiasis. In: Intestinal Anisakiasis in Japan (Ishikura H, Kikuchi K Eds) Springer- 

Verlag Tokio pp. 89-100. 

Kojima K, Koyanagi T, Shiraki K (1966). Pathological studies of anisakiasis (parasitic abscess formation in gastrointestinal tracts). Jpn 

J Clin Med 24: 134-143. 

Mattiucci S, Nascetti G, Cianchi R, Paggi L, Arduino P, Margolis L, Brattey J, Webb S, D’Amelio S, Orecchia P, Bullini L (1997). 

Genetic and ecological data on the Anisakis simplex complex with evidence for a new species (Nematoda, Ascaridoidea, Anisakidae). J 

Parasitol 83: 401-416. 

Nascetti G, Cianchi R, Mattiucci S, D’Amelio S, Orecchia P, Paggi L, Brattey J, Berland B, Smith JW, Bullini L (1993). 

Three sibling species within Contracaecum osculatum (Nematoda, Ascaridida, Ascaridoidea) from the Atlantic Arctic-boreal region: 

reproductive isolation and host preferences. Int J Parasitol 23: 105 120. 

Ohtaki H, Ohtaki R (1989). Clinical Manifestation of Gastric Anisakiasis. In: Gastric Anisakiasis in Japan (Ishikura H, Namiki M Eds) 

Springer-Verlag Tokio pp. 37-46. 

Orecchia P, Mattiucci S, D’Amelio S, Paggi L, Plotz J, Cianchi R, Nascetti G, Arduino P, Bullini L (1994). Two new 

members in the Contracaecum osculatum complex (Nematoda, Ascaridoidea) from the Antarctic. Int J Parasitol 24: 367-377. 

Paggi L, Nascetti G, Cianchi R, Orecchia P, Mattiucci S, D’Amelio S, Berland B, Brattey J, Smith JW, Bullini L (1991). Genetic 

evidence for three species within Pseudoterranova decipiens (Nematoda, Ascaridida, Ascaridoidea) in the North Atlantic and 

Norwegian and Barents Seas. Int J Parasitol 21: 195-212. 

Yoshimura H (1990). Clinical Patho-Parasitology of Extra-Gastrointestinal Anisakiasis. In: Intestinal Anisakiasis in Japan (Ishikura H, 

Kikuchi K Eds) Springer Verlag pp. 145-154.

Risk of Anisakidosis related to Fish consumption

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