kiRci-lives

FISHERIES AND MARINE SERVICE

Translation Series No. 3671

Infestation of sea fishes with larval nematodes and its significance for nutritional hygiene

by K. Priebe

Original title: Die lebensmittelhygienische Bedeutung des Nematoden-larvenbefalls bei Seefischen

From: Archiv Lebensmittelhyg. 22(9): 193-200, 1971

Translated by the Translation Bureau(KMF) Multilingual Services Division

Department of the Secretary of State of Canada

Department of the Environment Fisheries and Marine Service

Pacific Biological Station Nanaimo, B.C.

1976

25 pages typescript

TRANSLATED FROM - TRADUCTION DE

German INTO - EN

English

PUBLISHER- ÉDITEUR

not shown

22 1971

TRANSLATION BUREAU NO. NOTRE DOSSIER N0 1089423 REQUESTING DEPARTMENT

MINISTÉRE-CLIENT Environment

SECRÉTARIAT D'ÉTAT

BUREAU DES TRADUCTIONS

DEPARTMENT OF THE SECRETARY OF STATE

MULTILINGUAL SERVICES

TRANSLATION BUREAU

DIVISION DES SERVICES

tr* Fq /n • t.r

11,.."•„a CANADA

DIVISION MULTILINGUES

tr •- VY■ t-t- 3 G, (

AUTHOR - AUTEUR

K. Priebe

TITLE IN ENGLISH - TITRE ANGLAIS

Infestation of sea fishes with larval nematodes and its significance for nutritional hygiene.

TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÈRE (TRANSCRIRE EN CARACTÉRES ROMAINS)

Die lebensmittelhygienische Bedeutung des Nematoden-larvenbefalls bel Seefischen.

REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGN CHARACTERS.

RÉFÉRENCE EN LANGUE ÉTRANGÈRE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTÈRES ROMAINS.

Archiv ftir Lebensmittelhygiene

REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS

Archives for Food Hygiene

DATE OF PUBLICATION DATE DE PUBLICATION

PAGE NUMBERS IN ORIGINAL NUMÉROS DES PAGES DANS

L'ORIGINAL

193 - 200 YEAR

ANNÉE VOLUME

PLACE OF PUBLICATION LIEU DE PUBLICATION

not shown

ISSUE NO. NUMÉRO

9

NUMBER OF TYPED PAGES NOMBRE DE PAGES

DACTYLOGRAPHIÉES

2 5

BRANCH OR DIVISION TRANSLATOR (INITIALS) Fisheries & Marihe Service KMF

DIRECTION OU DIVISION TRADUCTEUR (INITIALES)

Pacific Biological Stqtion e Nanaimo, B.C.

PERSON REQUESTING DEMANDÉ PAR Dr. L. Margolis

YOUR NUMBER VOTRE DOSSIER NO

DATE OF REQUEST DATE DE LA DEMANDE January 7, 1976

MAR 1 9 1 97(ei

7 ;),

FfO I1 r,cAil:2rocni

SOS.200.10.8 (REV. 2/60 7530.21-02D•5333

'‘ DEPARTMENT OF THE sEcreLTARY or srArr. TRANSLATION BUREAU

TARIAT D'ÉTAT

BUREAU DES TRADUCTIONS

MULTILINGUAL SERVICES

DIVISION

DIVISION DES SERVICES

MULTILINGUES

CLI ENIS -170. • N° DU CLIENT

10891123

MINISTÙIE

Env ir onme nt

LANGUAGE

LANGUE

German

DIVISION/BRANCH CITY

DIVISION/DIRECTION VILLE

Fisheries Parine Servie Pacific Biological Staipn Nanaino, B.C.

BUREAU NO.

N° DU BUREAU TRANSLATOR (INITIALS)

TRADUCTEUR (INITIALES)

IÇIÎF MAR 1 9 1976

Archly fuer Lebensmittelhygiene 22, 9 (1971) pp. 193 — 200

Infestation of sea fishes with larval nematodes

and its significance for nutritional hygiene*

K. Priebe

(From the Federal Veterinary Bureau in Bremerhaven, Director: Vet. Dir. Dr. U. Kietzmann)

Sea fishes fulfill tha function of intermediate host for the

development cycle of numerous species of nematodes which parasitize

animals of marine biotopes. In marine species caught by maritime

fishing operations one frequently finds the third larval stage of

nematodes from the family of Heterocheilidae, which represent the

stage ready for invasion of marine mammals and birds feeding on sea

fishes which serve as the final host.

Morphologically, this third larval stage is only little

differentiated which explains why these larval nematodes were until

recently assigned to various other genera or species and why the

*Based on a lecture on the occasion of the 14th work session of the Sector "Food Hygiene" of the DVG (German Veterinary Society) on Sept. 29, 1971 in Freiburg/Breisgau.

UNEDITED TRANSLATION

For information only

TRADUCTiON Information sculemour

SC:15-2, 00-I 0-31

-, 1•2

— 2 —

question as to specificity of the intermediate and final host frequent-

ly remained unanswered. Larvae of the same morphology occur in

different species of sea fishes (e.g. Anisakis in herring, salmon,

mackerel, redfish ), while, on the other hand, various species of

larval nematodes infect one and the same species of sea fish ((e.g.

Terranova sp. and Porrocaecum sp. in Gadus callarias (Templeman et

al., 1957; Grainiger, 1958)).

The larva occurring in the herring (Clupea harengus) of the

North Atlantic is classified as belonging to the species Anisakis

marina which, in its adult form, can be found particularly in the

stomach of the Gr3y Seal (Halichoerus grypus) , the White—beaked

Dolphin (Lagenorhynchus albirostris) and the Common Porpoise (Phocaena

phocaena)(van Thiel, 1966). The Japanese literature reports on

Anisakis—type larvae which are found primarily in the cod (G , morhua

macrocephalus) , in the Alaska Pollack (Therogra chalcogramma) , in

the Japanese Mackerel (Pneumatophorus japonicus japonicus) , the Horse-

mackerel (Trachurus japonicus), in the herring (Clupea harengus pallasi)

as well as in the cuttlefish of the Pacific (Todaro pacificus) (Kagei,

1968). We, ourselves, determined an almost 100% infestation with a

larval nematode in imports of several hundred tons of Pacific herring

(Clupea harengus pallasi) which clearly differed in size from Anisakis

marina of the Atlantic herring (Clupea harengus harengus).

The reports concerning the frequency of infestation of sea fish

with larval nematodes are numerous. As a rule, the proportion of in-

fested sea fishes of the catch is surprisingly high, percentages close

to 100 not being rare (Kietzmann et al., 1969). On the other hand,

3

populations of sea fishes in which no larval nematodes were detected

or if so, only in a few specimens, are much less frequent. The wide

distribution of larval infestation in the fishes of the open sea is

therefore comparable to the parasitic infestation of domestic live-

stock raised under unsanitary conditions. One promoting factor is

undoubtedly life in dense schools as well as the migratory habits of

the fishes. As a rule, the life span of the larval nematodes exceeds

that of the intermediate host, the sea fish, resulting in an accumula-

tion in the sea fishes (stock host) which manifests itself in the in-

tensity of infestation per fish relative to its age.

In spot-check examinations carried out in Bremerhaven during

the years 1969 to 1971 on 10 herrings each of a total of 85 herring

catches from different fishing areas, or imports from various countries,

only 10 samples (= 11.8%) were found to be free from larval nematodes,

while in 42 samples (= 49.4%) 50% and more of all examined herrings

and in 33 samples (= 38.8%) less than half of the examined herrings

were infected.

Localization of the larvae within the'sea fishes varies. In

the main, the following conditions are observed:

1. Occurrence in the body cavity. In this case, the larvae,

surrounded by thin membranes resembling connective tissues, lie between

the mesentery or below the more or less curved, serous covering of

the organs or the wall of the body cavity. This form of occurrence

is observed most frequently in sea fishes, such as in herring, cod,

redfish, pollock. Due to the proper motility and the migratory abi-

lity of the larvae after the death of the sea fish, the larvae are

.ei-N • •

Se.

55 b

often found freely moving in the body cavity. This condition is there-

fore encountered mainly in fishes which reach the market only partly

or not at all eviscerated (e.g. smoked or salted herring). A method

of examination which leaves the fish intact in unknown (Fig. 1).

Fig. 1

Coiled agglomeration of Anisakis marina between the lobes of the roe in the body

cavity of a herring

Inspection is possible only by opening the body cavity of

selected random samples. Due to the generally high degree of in-

festation, a small number of samples is sufficient to provide an

overview. With medium or low intensity of infestation a greater

number of random samples would have to be selected; however, in-

fection of individual fishes belonging to the samples group cannot

be excluded in this case.

2. Occurrence in the muscles. Here too, the larvae are im-

bedded in a thin membrane of connective tissue formed by the body of

the intermediate host from which the larvae emerge after the death

of the fish. Of the main species of sea fish brought ashore in

Germany, this condition can be found primarily with the Brosme and

the Bluefish. The larvae occur deep within the filet as well as in on

that part which isiethe side of the body cavity and frequently also

on the side of the dermis (Fig. 2).

Fig, 2

Larval nematodes on the dermis side and deep within the filet of a Brosme.

Fig. 3 Larval nematodes under the intact skin of a smelt,

visible from the outside.

— 6 —

In fishes with transparent skin (smelt) the larvae can shine

through the skin, in which case the infestation with larval nematodes

in the fishes is recognizeable from the outside (Fig. 3).

The detection of larval nematodes in skinned filets, depending

on their thickness, is possible on a sufficiently illuminated back-

ground (intensity of illumination at filet height approx. 10,000 lux).

According to Canadian investigations on the cod, a maximum of 25% of

infected filets can be recognized due to the thickness of commercially

sliced filets, whereas the rate of detection can be raised to 95% and

over if sliced lengthwise to a filet thickness of 143 cm (Power, 1961).

According to our own observations the detectability of larval nematodes

in transmitted light is limited also in such species of fish (e.g.

Bluefish) whose silvery dermis which adheres to the filet is very

pronounced (Fig. 4).

Fig. 4

Table with illuminated glass plate for the detection of parasites, fishbones, etc., in filets during the processing of fishes.

- 7 -

The occurrence of larval nematodes in the bodyis muscles can

also be caused by a migration of the larvae from the natural location

which they occupy in the body cavity into the muscles after the death

of the fishes. This can frequently be observed where the fishes are

not eviscerated soon after they have been caught. Thus, for instance,

no larvae were detected in the muscles of mackerels whose entrails

were removed immediately after they were caught. However, if a period

of 24 hours elapsed until the fishes were gutted, larvae were detected

already in the muscles of 0.5% of the mackerels. This proportion was

increased to 10 - 13% if the entrails were removed only 3 - 4 days

after the catch (Vik, 1966) . .

The same phenomena can also be observed in herring. The

of herrings in whose muscles larval nematodes are imbedded

depends on the period of time which elapses until gutting and on the

number of larvae present in the body cavity. As a rule, no larval

nematodes are detected in the herring muscles, immediately after the

catch. With an average number of larval nematodes in the body cavity

of 3 per herring, almost e of the fishes. showed an infection of the

muscles after storage on ice for 4 - 8 days (calculated according to

the experimental results by Kuipers et al. (1960) and provided that

the muscles of each herring were only infected with one larval nema-

tode). On the other hand, Houwing (1969) determined 27 larval nema-

todes in machine-sliced filets in a catch of 50 herrings with an

average number of 15.4 larval nematodes per herring. We t ourselves,

examined 1,000 machine-sliced, washed herring lobes with the serous (195)

covering of the wall of the body cavity removed by machine,by thorough

4.

—8

visual inspection and, in suspicious cases by dissection, for the

presence of larval nematodes; this material originated from a herring

catch with an average number of 5 larval nematodes per herring. In

12 herring lobes we determined 1 larval nematode each (1.e). The

larvae were present mainly in the depth of the muscles of the gastric

lobes and were noticeable either by a blood—reddish or brownish colour

of the surrounding muscle tissue or by parts of the larval nematode

which protruded from the surface of the lobe. The detection of larval

nematodes in herring lobes must be considered difficult. On the other

hand, it is certain that a relatively large proportion of larval nema-

todes can be found on herring lobes whose serous wall of the body

cavity has not been removed because the larvae sometimes occur sub-

serously already in vivo on the wall of the body cavity. Evisceration

of the herrings for the purpose of removal of larval nematodes would

therefore have to include also the parietal lobe of the serous membrane

of the body cavity.

3. Infection of the visceral organs. The liver of the cod is

frequently affected. While larval nematodes are normally found alive

in freshly—caught sea fishes — possibly because of the relatively

short life—span of the fishes — the cod liver contains mainly dead

larvae, frequently in conjunction with extensive liver necroses. This

probably involves the larval invasion of a non—adapted species of

nematodes (Fig. 5).

-9

Fig._5

Surface of a cod liver with roundish necrotic areas caused by larval nematodes.

Approximately 10 years ago a Dutch group of researchers

(Kuipers et al. 1960) found that the consumption of raw or half—raw

fish dishes causes disorders in man through the ingestion of live

larval nematodes; these disorders exhibit symptoms of eosinophilic-

infiltrated granulomas tending to abscess formation in the wall of

the stomach or the intestine, or in organs of the adjacent abdominal

cavity (literature survey by Ruitenberg 1970). It became obvious that

these larval nematodes possess an active boring capacity long after

the death of their intermediate host, the sea fish, which enables them

to penetrate the gastro—intestinal wall which is, however, quite un-

specific with respect to the animal species or its tissue to be in-

vaded. This ability to penetrate is therefore retained not only in

the specific final host in whose gastro—intestinal wall the larva

undergoes its final development to return as an adult worm into the

-10 -

intestinal lumen which it then parasitizes, but also in non-adapted

false hosts (e.g. man) where, however, larva III soon dies due to

the body's defense mechanism and where, as a foreign substance, it

produces the above-mentioned symptoms. Thus the histological profile

frequently shows foreign body giant cells (Asayama, 1967). In the

specific final host, on the other hand, only slight, eosinophilic

cell infiltration is caused which heals again after the larvae leave

the gastro-intestinal wall. The same symptoms as observed in humans

can also be reproduced in experimental animals (rat, rabbit, guinea

pig, dog). They can also be observed in marine mammals in zoological

gardens if sea fishes are offered as feed which contain larval nema-

todes not adapted to the particular animal species (Gembardt et al.,

1971; Young and Lowe, 1969).

Due to the fact that mostly larval nematodes of the species

Anisakis were found to be the cause for the disorder * this is designated

as anisakiasis by the majority of authors, while other names such as

heterocheilidiasis or herringworm disease are less common. The number

of cases in humans which were reported up to 1970 amounts to approxima-

tely 300. Of these, most cases occurred in Holland and in Japan. Only

few cases were mentioned from other countries, such as England and

Scandinavia. In Germany only one case of illness was reported to date

in a young man who, during a camping holiday on the Baltic Sea had pre-

sumably consumed a half-cooked herring (Schaum and Mueller, 1967).

Particular habits of consumption or manner of preparation carry the

sole responsibility for the cases of illness in the countries involved

in which the boring capacity of the existing larval nematodes is retained.

- 11-

Thus, in Holland it was the so-called "groene" (green) herring, an

incompletely eviscerated, very lightly salted and practically raw

herring which underwent a certain curing during cool storage. In

Japan many sea fishes are consumed raw or are merely subjected to a

light, short-term vinegar-salt treatment in the form of the dishes

II sashimi" or "sunomono" (Yokogawa and Yoshimura, 1967). In Norway, (196)

the fish dish "gravfisk" is considered dangerous; in this the fish

is kept lightly salted and sugared for 1 to 2 days and is then

served in a wine sauce (Vik, 1966).

Except in animal experiments, the boring capacity of larval

nematodes can easily be tested in vitro according to a suggestion by

Ruitenbera and Roskam (1969), by placing the larvae to be examined

onto the surface of semi-solid agar (1% in physiological salt solution)

roughened with tweezers in half-filled test tubes and by adding several

drops of herring blood or Ringer solution and by incubating the material

for 2 days at 37 0C. The larvae with boring capacity can then be found

deep in the column of agar. The effect of fish processing methods

on the viability and thus the boring capacity of larval nematodes can

therefore be tested in a relatively simple manner whereas in expensive

animal experiments the greater part of viable larvae, depending on

peristalsis and gastro-intestinal contents, passes through the intestine

without adhering to it.

Experimental investigations have shown that if the brine which

develops in the salting of herring reaches a density of over 200

Baume (corresponds to 20.9 weight % table salt) no live larval nema-

todes are found in these herrings after 10 days, whereas the lifespan

— 12—

of the larvae can be prolonged considerably at lower salt contents

(Souwing et al., 1967). In dry table salt the larvae die within 10

minutes, in a saturated sali solution (26.3 weight percent at 10°C)

within one day, while in a 5% salt solution the larvae remain alive

for weeks. Similarly, freezing to —20°C within 24 hours or to —100C

within 48 hours causes the loss of the boring capacity, whereas

shorter freezing times. and higher freezing temperatures result in a

large proportion of surviving larvae. Temperatures of 50 — 52°C also

result in loss of the boring capacity within 10 seconds (Houwing et al.,

1967; Houwing, 1969b; Khalil, 1968). During the production of cold-

marinated fish it became evident that in barrel curing, a curing

process which in Germany is used almost exclusively by industry,

where — due to the high starting concentration of vinegar (approx. 7%)

and table salt (approx. 15%) at a herring/curing bath ratio of about

2 : 1 — the herring floats in the liquid, the larvae are killed after

30 days; on the other hand, curing in open containers at lower con-

centrations of vinegar and table salt (4 and 6% respectively) and a

herring : curing bath ratio of 1 : I produced certain destruction of

the larvae only after 70 days (Houwing, 1969a). Radioactive irradia-

tion of 0.1 — 0.6 Mrad resulted in a loss of the boring capacity of

the larvae after 2 hours (Ruitenberg, 1970). When investigating the

question, to what extent mechanical damage to the larvae (act of chew-

ing, comminution during the processing of the fish) results in the loss

of the boring capacity, it was determined that of cross—sectioned larval

nematodes a mere 20% of the larval front ends exhibited a decreased

boring capacity for several hours, whereas the rear ends of the larvae,

—13—

i.e. all larvae whose front ends (length of esophagus and ventricular

section) had been severed, ceased to move. These larval nematodes

are therefore not endowed with any particular regenerative ability —

a characteristic which holds true for all representatives of the class

of roundworms (Nemathelminthes)(Jaeckel, 1955) (Table 1).

In accordance with this information and the customary manner

of preparation and consumption of the herring, "herring regulations"

were passed in Holland in 1968 and 1969 to protect human health; these

were designed to eliminate any health hazards through binding regula-

tions and strict control measures and to remove the fear of the public

of damages to health through consumption of herring. In accordance

with these regulations the caught herring which is intended for the

market as a fresh fish, must be deep—frozen within 18 hours after the

catch in such a manner that within 12 hours a temperature of —20°C is

attained within the herring which must be maintained for 24 hours.

This freezing method is mandatory also for those herring products

which will not undergo or have not been subjected to the following

treatment during processing:

1. In salt curing a density of at least 20 ° Baumé must be attained in the

brine after 10 days.

2. During heat treatment (smoking, baking, etc.) a minimum temperature

of 50°C must be attained.

3. During the curing process of cold marinades in which the fish re-

mains in the curing bath for at least 30 days, at a herring:

curing bath ratio of 2.2 : 1 at the most, a maximum pH value of 4.0

and a minimum salt concentration of 6.5% must be attained.

SA

- 14 -

In view of these Dutch regulations governing food hygiene

it is evident that there are a number of herring products also in

the Federal Republic of Germany which would be subject to strict

regulations in Holland. It should therefore be well worthwhile to

consider and examine whether such measures are necessary also in

Germany even if here a general distribution of this disease is un-

known in man and an acute danger is not evident at this time. No

doubt, such measures are also in the interests of the fish industry

if they will serve to remove any recurring uncertainty on the part

of the consumers through one-sided or unfactual reports by the mass

media.

These considerations refer particularly to the fresh, mildly-

salted herring seasoned with herbs as well as to cold-marinated fish

and products of cold-smoking which have not undergone adequate salt

treatment. On the other hand, products of hot-smoking, canned fish

and fish processed by baking and boiling seem to be free from danger

because these products are subjected to sufficient heating during

processing. It should further be pointed out that at least periodically

the major portion of all fish products is produced from deep-frozen

raw material and, furthermore, consists of those parts of the herring

(filet or lobes) where the incidence of larval nematodes can be re-

garded as low.

The fresh or green herring which is sold raw, eviscerated or

non-eviscerated is a popular item of consumption in Germany. Compared

to Dutch eating habits following curing in a mild brine, the green

114

— 15 —

herring — similar to other fresh sea fishes — is eaten in Germany

only after heating (usually baked). If the fish is marinated in

the kitchen the starting material is never raw, but always heat-

treated herring. A kitchen—technological marinating is to be con-

sidered not as a cooking process but rather as a special flavouring.

In this way, the fresh herring — just like any fresh fish — (197)

does not represent a health problem in Germany because any larval

nematodes which may be present are destroyed by processing in the

kitchen before consumption. Even from the point of food regulations,

a herring infected with larval nematodes cannot be regarded as a

health hazard because a foodstuff, according to the official reason-

ing behind Section 3 of the Food Regulations, is a health hazard

only if it possesses this characteristic in the edible state since

the consumption of many foods which are, in themselves, quite sound

may in a raw or improperly prepared state cause disorders for which

the person who markets such food cannot be made responsible.

Despite the legal implications of these food regulations one

should not, however, fail to inform the public that the consumption

of insufficiently cooked fish dishes (faulty product) can be dangerous

and that attention must therefore be paid to proper preparation (through

baking or boiling). The drafting of regulations covering the fresh

herring would therefore also require regulations governing the trade

with fresh sea fishes in general for which, however, no compelling

reason exists due to our customary aating habits because fresh fish

still seems to be considered nutritionally more valuable than thawed-

out deep—frozen fish.

-16-

Of the ready—to—eat herring products produced by the German

fish industry, the mildly salted herring (Matjes) and salads prepared

from it is much favoured by large parts of the German population.

These products can, in fact, prove a possible risk upon consumption

if they contain larval nematodes, a possibility which from a quanti-

tative point of view must be regarded as very slight. In order to

remove any such.doubts it should certainly be considered to eliminate

the possibility of the presence of live larval nematodes in these

foods by registering all producers and all imports of such products,

by stipulating the salt content and curing period or by freezing,

and by the application of suitable control measures.

No information is available to date concerning the behaviour

of larval nematodes in herb—flavoured herrings which were cured in

a salt brine with the addition of sugar and spices. The risk seems

to be small here because a period of over 6 weeks is estimated for

curing.

From the Dutch point of view, cold marinades also present a

danger for human health. Here too, one can proceed from the fact

that the slices cut from the herrings (marinated filet) as well as

the small herrings (Kronsild) contain only a very small number of

larval nematodes anyway. Although Dutch regulations requiring a

curing period of at least 30 days at a final maximum pH value of 4.0

and a minimum salt concentration of 6.5% seem to result in the loss

of the boring ability of any larvae present, the application of such

a curing time would reduce the usefulness of this method because

leaving the herring in the brine after curing is completed (approx.

-17-

4-6 days) decreases the keeping quality of the finished product due

to progressive protein hydrolysis. Here too, deep-freezing appears

to be the best method for practical purposes.

For the sake of completeness it should be mentioned in connec-

tion with the human anisakiasis that the occurrence of eosinophilic

meningoencephalitis in persons on Hawaii, Taiwan and French Polynesia

is caused by migrating larvae of the lungworm of the rat (AnziosIroAgylms

cantonensis) which are transmitted to man by the consumption of

mussels and prawns (Rosen et al., 1967); similarly, the human form of

gnathostomiasis should also be mentioned which manifests itself in

disorders of liver, eyes and skin and occurs in various parts of the

world (Japan, Thailand, China, Palestine) and is transmitted by the

consumption of raw or half-raw fresh-water fish which harbour these

larvae (Miyazaki 1960).

Another problem is the presence of larval nematodes in fishes

or fish products as a nausea-arousing factor as such. The nausea-

causing condition of a food is regarded as a considerable deviation

from the normal condition which greatly impairs edibility. Such foods

are considered spoiled according to Section 4, Paragraph 2 of the Food

Regulations and if not sufficiently identified as such, are therefore

excluded from the market as a food item. Undoubtedly; the nauseous

quality of infestation with larval nematodes depends on the subjective

attitude on the part of the consumer. The degree of nausea aroused

by nematode infestation in animal foods is frequently felt more keen-

ly than in plant foods. The reactions by the consumer are by no means

uniform. Apart from the fact that nobody will experience an increase

—18—

in appetite upon finding larval nematodes when eating a dish, the

following main reactions are possible depending on attitude, experience

and knowledge of the consumer:

1. Total refusal of an y future consumption of sea fishes.

2. The dish just objected to is not eaten, but a sound meal

is again consumed at any time.

3. The dish is eaten if it is possible to remove the larval

nematodes.

To investigate the reactions of the consumers seems to be the

task for a public—opinion poll during which not questions but fish

dishes infested bith larval nematodes should be presented. The number

of larvae found while eating seems to be of secondary importance for

a complaint. One larva seems to be just as nauseating as many. Apart

from this, the distribution and localization of the larvae in the fish

seem to be of decisive significance whether the dish is eaten or not.

Upon presentation of the objective evidence, namely the larval nema-

todes, the complaints voiced by the consumer because of nausea are in-

contestable. For this reason fish and fish products have repeatedly

been rejected as spoiled according to Section 4, Paragraph 2 of the

Food Regulations and correspondingly, preliminary— and criminal pro-

ceedings were instituted. Of 38 known preliminary proceedings in the

years 1963 — 1971 (Marwitz, 1971) where the infestation of sea fishes

with larval nematodes was criticized, 34 were dismissed by the pro-

secution already before arraignment. Only in 4 cases a verbal trial

took place. Of these, two cases were dismissed, while one case re-

sulted in an acquittal and another in a sentence. It becomes clear

‘11,

— 19 —

from this number that even prosecuting authorities such as courts in (198)

the main see no cause for punishment when dealing with such complaints.

If one proceeds from the fact that the Food Regulations as a

penal by—law serve, among other things, the purpose of protecting the

food consumer from fraud and cheating, it becomes clear that this ob-

jective where it concerns complaints because of nausea in cases of

larval nematode infestation in sea fishes has certainly not been

accomplished nor, it is safe to say, will it be accomplished in the

future. The inadequate detection of nematode infestation — with

respect to examining of filets in transmitted light as well as random

testing of uneviscerated sea fishes — and the heavy and wide—spread

infection of sea fishes with larval nematodes in most fishing areas

will continually lead to complaints even though it is not always

possible to lay the blame on any one individual. Although prudent,

general identification of nematode infestation when trading with sea

fish products solves the problem from a legal point of view so as to

prevent lawsuits under the present laws, it does not take into account

the importance of the sea fish as a food inasmuch as most products do

not possess this shortcoming; its occurrence is limited to special

products (salted, smoked herring) or to individual cases where de-

tection and removal of the larvae during processing was not possible.

The consistent legal prosecution in cases of trade with sea-

food infested with larval nematodes would have to be equated with

the prohibition of these products for which there exists no substitute.

The ocean fishing industry which catches sea fish at great expense

and must process the catch on board ship in order to land it in as

—20 —

fresh a condition as possible would, if larval nematodes were detected,

be forced to dump the catch into the sea or to land it as raw material

for fish meal at prices which would in no way cover the costs of the

catch.

Herring Salt content etc. Storage Maximum life Product Recipe of brine or final tempera— span of larval

curing bath ture nematodes

Matjes 11 kg salt Herring 20 litres 17% (immature salt solution 15.5% salt 0°C 14 days herring) 95 kg headed herring

Matjes 9 kg salt Herring 20 litres le

salt solution 18.6% salt 0°C 20 days 95 kg headed herring

Matjes 14 kg salt Herring 30 litres 17% Nordic salt solution 17.8% salt 0°C 23 days Variety 2 kg sugar

95 kg headed herring

Spiced 14 kg salt Herring 13 litres 17%

o 26 days salt solution 19.7% salt 0 C 4 kg sugar 1 kg spices

95 kg headed herring

riSat.Ler, 35 litres brine with 5e salt 4 0 eyL n 7.% acetic acid and 2.1% acetic

14% salt acid 4°C 37 days 84 kg headed herring pH 4.6 .

Table 1

Experimental results on the maximum lifespan of larval nematodes in herring products

-21—

Even proposals which call for the eviscerating of herring

or of certain herring products as a binding requirement would only

partly solve the problem even for herring without eliminating it in

a satisfactory and permanent manner for all sea fishes.

Thus the expedient of manufacturers of smoked herring to de-

viate from the tradition of herring smoking which dates back to the

13th century, namely to smoke the herring in an eviscerated state

(without larval nematodes) was not appreciated by the consumer be-

cause a herring sliced up in this manner suffers losses of oil and

moisture during smoking and lacks the usual taste of smoked herring.

For thesc,. reasons it is proposed to refrain from the applica-

tion of Section 4, Paragraph 2 of the Food Regulations in the case

of infestation of sea fishes with larval nematodes and to ensure

within the framework of the revised German Food Regulations that re-

course to criminal charges is not intended in the case of deviations

in foods due primarily to natural causes which cannot be influenced

when acquired or processed and remain concealed depending on the pre-

vailing state of the art but which detract from the enjoyment of the

food due to arising nausea when detected by the consumer. Rather,

it should be considered adequate if such complaints are settled by

civil law (extent, concealment at time of sale) so that the person

who introduces such foods into the market is not absolved from his

responsibility to avoid such shortcomings. On this basis it seems

reasonable that no confusion would ensue in this food sector because

of this deficiency nor would the consumer be less well protected. As

far as it is known from the practical side of the fish trade, fish

stores are willing to make refunds in cases of such complaints. (199 )

-22—

In my opinion it is more important to explain the true facts

to the consumer. In the sale of smelts (Osmerus eperlanus) whose

infection with larval nematodes is well known by the coastal popula-

tion, complaints are virtually unknown, despite the fact that the

degree infestation of the smelt with larval nematodes is very high

and the worms (Porrocaecum decipiens) can hardly be overlooked because

of their size. The degree of information of the coastal population

by itself solves the problem in such a manner that one part of the

population abstains from eating smelts on its own accord while others

appreciate the taste of the fish and accept to carefully examine the

fish (which is commercially available mainly in uneviscerated state)

during preparation and remove the worms themselves.

It would be important to explain the following points to the

consumer:

1. Infestation of sea fishes with nematodes is natural and is

not rare. It is not a sign of decomposition and has nothing to do

with pollution — in particular that of ocean fishing grounds.

2. For technological reasons and in connection with biological

factors such infestation can frequently be observed in certain fish

products (smoked or salted herring) or in certain species of fish,

whereas other products can be considered as virtually free of larval

nematodes because the entrails which harbour the larvae are removed

soon after the catch.

3. With the preparation of sea fishes (boiling, baking) common

in Germany and the customary procedures in the processing of fishery

products (particularly cans, products of hot—smoking, boiled and baked

- 23 -

fish products) and - where it is deemed necessary - upon observance

of certain processing specifications such as deep-freezing or keeping

a certain period of time during curing or marinating while monitoring

the salt concentration etc., the consumption of such food does not

constitute a health hazard because the larval nematodes are killed.

However, it should be pointed out that such a hazard may ensue

from the consumption of raw or half-raw herrings if they contain live

larval nematodes. When cooking these, attention should be paid to

uniform heating.

4. Recause fish or fish products infected with larval nematodes

may induce nausea, a refund may be requested from the seller according

to civil law.

Summarx

The occurrence of larval nematodes in sea fishes is not rare.

Due to inadequate detection methods in the processing of fish and

despite observance of the necessary care in the trade, it cannot be

prevented entirely that sea fish products may at times be infected with

larval nematodes. Disorders in man may occur when live larval nema-

todes are ingested during the consumption of fish dishes (anisakiasis).

This possibility can be ruled out for the form of consumption of fresh

sea fish including fresh herring common in Germany (boiling, baking)

as well as for most ready-to-eat fishery products (deep-frozen, canned,

fried, boiled, salted, smoked fish products). In mildly salted herring

products (salt content of the water in the fish tissue under 20e) and

cold marinades any larvae present are not necessarily destroyed so

' 1 t,

- 24 -

that a health hazard cannot be excluded when eating these products.

It is therefore proposed to examine whether these herring products

should be produced from deep,—frozen herrings or whether the products

themselves should be deep—frozen or whether — e.g. in the case of

cold marinades — a curing duration of at least 30 days, a final

maximum pH value of 4.0 and a final salt content of at least 6.5

should be ovserved. It should be in the interest of the public at

large if such measures would eliminate with certainty all possibility

of a health hazard through the consumption of fish products infested

with larval nematodes. It is further proposed not to prosecute

(according to the Food Regulations) the marketing of sea fishes and

fish products infested with larval nematodes for causing nausea sinch

according to present experience and because of the lack of suitable

examination methods in connection with the widespread infestation of

sea fishes with larval nematodes, the threat of punishment according

to Section 4, Paragraph 2 of the Food Regulations was not successful

in the sense of effective consumer protection.

The settlement of such deficiency rulings should be left to

the civil law (refunds). For the rest, it is commensurate with the

importance of the food item "sea fish" and appears to be in the in-

terest of all concerned that the consumer should be thoroughly in-

formed of all facts, honestly and without bias.

-25-

Literature

Asaml. K. und F. Inosh I t a (1 ,17). Experimental anIsaklards in guinea pigs. Jap. J. Pare,..1. 16, 417-42:. — ASaytna, If. (1967 ): Ein Fall von parrvaterern cosinnishi• tern Maneneranulam Ynnago Acta Merl!. t t, 54.—e8. — Gemba r cl t C.. 13. Hildebrand und R. Gotten-bot h (197Ir Ourdi AnIsakis-Befall hervorneruferie Pylorus-stennse bet einern See•Elephenten (Mirminea Iconinai. 13 , r-liner Milnehener Tierateil. Wschr. SI, 19.1—,J5 — Graint• g e r , J. N. R. (1958). The identity u( the larval Nematode.: found in the body muscles ot the cod 'Gaut, eallarms L.). PararoterIngy 19, 121-131. — 11 pos.:in,. IL (1969 at Het inactIv , ren van de harlintneinatncle door keukenenut en aztineuur. Visserilwereld 28, Nr 21) — derselbe t1959 tri Het Inactiveren van haringneinatoden tiidens het rookproce, \'is-sertJwi 28. Cr. 20 —liousetnn. If rl loem sm a tend C. J. Weber (1967)• Technologische mogellikneden ter vonrkrionng van de eit, bai ir.i wormmetke Institute for Fisher, Products T 4(). Hr.:linden The Netherland,. Re-port 188. — Ja eck el, S. (19551: Uns Tierrroch. Wurmer. Snnttflhiiiig Goschen Eland 439. W. tie Gruyter u. Co., Berlin. — Kaget, (1969) Infection and prevention of Anisakis. Kagaku-Asakt 28. 97.1.0 S. Zit, n Ituitenherg. E. J. 1970. — Khalil. 1- F (1988): Anisaklasts — „Herine-worin Disea1e" — The Antsakls-tYPe larval in the tiering of the North Sei. Trans. Royal Soc. Trop. Med. Ilyg. 62, II. — K I e t n ni s n n , tl., K. Pr ie be, D. )takosr und K. RelChStvIn 1191■9,. Seefisch ais Lebensnuttel. Verlag Paul Carey. Berhil und Hamourg. — K utpers, F. C.. P. 11. van Thiel and R. Th. R osk a ru (1969), Eostnoflele tlegnione van de donne Carol. verooreankt door een niet aan hot lichaarn aangepaste won. Ned. T. Geneesk. 101, 422-427. — Mar sell e. — (1571): Per-sonliche Mittedung v. 14. 7 1971, -- Mt >rasa': 1, J (treat. On th, Genus Gnathostoina and Human Grialluvrtomiasts. with Site-chat Reference to Japan. Experimental Parasou-lOgy 9, 338-370. -- Myers, B. J. Mtn) The tmeranon nf Anisakts-type larvae in experimental animais. Canad. J Zool. 11. 147-116. — Power. If. E. (1961), Slicing of Fillets as an Aid In Detection and Removal of Codonrins 1rorn At-lantic Cod Fillets. J. Fish. ReS. Bd. Canada IS, 157-110. — Rose n, Lb LOI-soit. J. Latgret and C.D.Wal. lace (1967): Studies un eosInophille meningitis. Amer. J. of EpIdennology SS, 17-44 — flut tenberg. E. J. (1970): Ant-saklasis. Vet. Med. Dias. Utrecht. — li u 1 ten be r g, E. J. und R. Th. Rush a ni (1989> Ken eenvnudige controlerne-thode op de tribnringseapacitelt van Anisakis larven. Con-serva 17.236-237. — Schaum, E. und W Muller (19571. Die HeterochetIldiasis. Otsch. med. Wschr. 95, 2230-2253. — Tcmp)entan, W.. IL J. Squires and A. M. Fle-ming (1957). Nematodes in the Fillets of Cuit and other Fishes In Newfoundland and Neighbouring Areas. J. Fish.

Asayama: A case of parasitic, eosinophilic stomach granuloma.

Gembardt et al.:Pyloric stenosis in a sea elephant (Mirounga leonina) caused by Anisakis infestation.

Houwing: The inactivation of herring nematodes during smoking.

Houwing, et al: Technological possibilities of preventing the so-called herringworm disease.

Jaeckel: The Animal Kingdom. The Worms. Collection GBschen Vol.439.

Kietzmann: The sea fish as food.

Kuipers: Eosinophilic phlegmon of the small intestine caused by a worm not adapted to the host organism.

Marwitz: Private Communication ,

Ruitenberg: A simple method of measuring the boring capacity of Anisakis larvae.

Schaum: Heterocheilidiasis.

Author's Address: OVR Dr. K. Priebe, 285 Bremerhaven-F Halle 10

FEDERAL REPUBLIC OF GERMANY