herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

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Veterinary Science Communications, 2 (1978) 63--72 Elsevier Scientific Publishing Company, Amsterdam --Printed inThe Netherlands ECSC, EEC, EAEC, Luxembourg, 1978 63 EUROPEAN COMMUNITY PREVIEW ARTICLE HERD TESTS ON MEAT LIVESTOCK TO PROTECT CONSUMERS FROM ZOONOTIC PATHOGENS AND CHEMICAL RESIDUES D. GROSSKLAUS Federal Health Department, Institute of Veterinary Medicine, (Robert von Ostertag Institute), Berlin, Dahlem, (Federal Republic of Germany) ABSTRACT Grossklaus, D., 1978. Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues. Vet. Sci. Commun., 2: 63-72. Clinical veterinary work is of prime importance for the task of the veterinary food hygienist. This is particularly true of early clinical, allergological, serological and bacteriological examination of herds of meat livestock, as proposed by Bartels, Kampelmacher, Grossklaus and others. Such investigations would make it possible to diagnose latent types of zoonosis which would otherwise remain undetected during official meat inspection. The pathological and anatomical findingsduring meat inspection are also of clinical importance. To these must be added the necessary measures to eliminate toxicologically significant residues of pharmacologically active substances. On ~he basis of his own research the author presentsproposals for herd tests which could help to promote, with improved safety, international trade in animal products for human consumption. INTRODUCTION The changing disease situation among meat livestock in many countries, the trend towards factory farming and the continued extension of international trade in animals and animal foodstuffs mean that food hygienists must examine new ways of developing trade and protecting consumers against pathogens and harmful chdmical residues. One way of doing this under existing national and supranational meat hygiene regulations is to carry out regular examinations of slaughtered animals at source, as discussed by * This article was originally written in German. Copies of the German version maybe obtained free of charge by writinq to: Mr. j. Rodesch, Corimission of the European Communities, DG XIII, B~timent Jean Monnet, Rue Alcide de Gasperi, Kirchberg, Luxembourg.

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Page 1: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

Veterinary Science Communications, 2 (1978) 63--72 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands �9 ECSC, EEC, EAEC, Luxembourg, 1978

63

EUROPEAN COMMUNITY PREVIEW ARTICLE

HERD TESTS ON MEAT LIVESTOCK TO PROTECT CONSUMERS FROM ZOONOTIC PATHOGENS AND CHEMICAL RESIDUES

D. GROSSKLAUS

Federal Health Department, Institute of Veterinary Medicine, (Robert von Ostertag Institute), Berlin, Dahlem, (Federal Republic of Germany)

ABSTRACT

Grossklaus, D., 1978. Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues. Vet. Sci. Commun., 2: 63-72.

Clinical veterinary work is of prime importance for the task of the veterinary food hygienist. This is particularly true of early clinical, allergological, serological and bacteriological examination of herds of meat livestock, as proposed by Bartels, Kampelmacher, Grossklaus and others. Such investigations would make it possible to diagnose latent types of zoonosis which would otherwise remain undetected during official meat inspection. The pathological and anatomical findingsduring meat inspection are also of clinical importance. To these must be added the necessary measures to eliminate toxicologically significant residues of pharmacologically active substances. On ~he basis of his own research the author presentsproposals for herd tests which could help to promote, with improved safety, international trade in animal products for human consumption.

INTRODUCTION

The changing disease situation among meat livestock in many

countries, the trend towards factory farming and the continued

extension of international trade in animals and animal foodstuffs

mean that food hygienists must examine new ways of developing trade

and protecting consumers against pathogens and harmful chdmical

residues. One way of doing this under existing national and

supranational meat hygiene regulations is to carry out regular

examinations of slaughtered animals at source, as discussed by

* This article was originally written in German. Copies of the German version maybe obtained free of charge by writinq to: Mr. j. Rodesch, Corimission of the European Communities, DG XIII, B~timent Jean Monnet, Rue Alcide de Gasperi, Kirchberg, Luxembourg.

Page 2: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

64

Bartels (1963, 1966), Dutschke (1966), Grossklaus (1968),

Kampelmacher (1969) and others. There &re two purely technical

reasons for carrying out herd tests.

i. Many animals are carriers of zoonotic pathogens but have at

the time of slaughter no clinical signs of disease. During

examinations of the living animal and the meat, it is not as

a rule possible to identify such animals. This loop-hole in

the system of official meat inspection may have adverse effects

on consumers.

2. The inspection of slaughtered animals for harmful residues of

chemical substances in meat and organs is pointless unless it

is possible to check on the situation in the herd of origin

when results are positive. Early random sampling of the

environment, feed and excreta (urine and faeces) of the animals,

however, could reduce the risk of undesirable contamination

in the meat produced. Finally, advice to the owner Of the

animals and supervision of the use of drugs on and in the

animal would ensure that 'waiting periods' are observed before

slaughter.

Figure 1 shows the most important zoonotic pathogens which often

remain undetected in slaughtered animals at the official meat

inspection as a result of latent infection and the absence of

pathologic anatomical changes in the organs. The list is based

mainly on the situation in the Federal Republic of Germany where

cattle and pig stocks are free of tuberculosis and brucellosis:

Infectio~s diseases

Tuberculosis

Brucellosis

Salmonellosis

Listeriosis

Leptospirosis

Toxoplasmosis

Rickettsiosis

Trichinosis

Incidence

Cattle, pigs, poultry

Cattle, pigs, sheep and goats

Cattle, pigs, sheep and goats, poultry

Cattle, sheep, goats, pigs, poultry

Pigst cattle, sheep

Pigs, poultry

Cattle, sheep, goats

Pigs

Cysticercosis (G. inermis) Cattle

Fig. 1. Types Qf zoonosis relevant to meat hygiene. Note underlining indicates those animals for which herd tests to determine the infected state are desirable.

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85

Figure 2 reviews the source of various residues in a, nimal foodstuffs:

Additives to feedstuffs

Drugs > A n i m a 1

Eggs

Pesticides

//Substances from

r contaminated

environment

Milk

Meat

Fig. 2. Origin of various residues in animal products for human consumption.

It is certain that most residues come from drugs which are

legally or, unfortunately, illegally administered. There are three

main reasons for the use of drugs by laymen without veterinary

precription:

a. diseases of iyoung animals

b. mastitis

c. growth promotion

During the past three years concern about the residues of

pharmacologically active substances has led legislators in the

Federal Republic of Germany to amend a number of laws or to

pass new ones. Laws on foodstuffs, drugs and animal feeding

stuffs have thus been improved and certain chemical substances

are now not permitted as residues in foodstuffs while maximum

levels have been set for others, (acceptable levels). The central

idea of these statutory provisions is the introduction of waiting

periods, viz. the time during which residues of harmful substances

may be expected in feedstuffs obtained from animals treated with

drugs in accordance with regulations. Until a waiting period has

been determined from detailed tests on the elimination rates of

the particular chemical substance a transitional ruling requires

a five day delay. FortuNately similar drug and feedstuffs laws are

being considered for all European Community countries with the

result that no one competitor wiil have an unfair advantage.

Page 4: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

66

Methods of identifying zoon0tic pathogens and residues in the source stock

The veterinary surgeon treating farm animals will in future have

an important part ~ to play in the hygienic production of animal

foodstuffs. He will increasingly be concerned not only with

maintaining the health of the animals in his care but also with

guaranteeing the quality of foodstuffs obtained from the animals.

In our opinion, he can do this by means of regular stock tests if

research helps him by providing practical methods for reliable

detection of pathogens and residues in the living animal. In

addition, the clinical veterinary surgeon knows the health conditions

of the animal stocks and can prevent inappropriate or even illegal

use of drugs. Close contact with the owner of the animals also

helps him to ensure the observance of waiting periods and to

provide only animal drugs which do not result in harmful residues.

For example Figure 3 demonstrates contamination pathways following

------- Insecticide

Insects on the animal

(Lice, fleas, mites, flies)

Insects in animal housing Contamination of

(air, walls, floor) feed

Animal bodies~ ~'~

Animal products for human consumption

Fig. 3. Uptake of insecticides by animals

the incosrect use of insecticides, which are mostly chlorinated

hydrocarbon derivates. In this case it is clear that only the

clinician can eliminate the causes and demonstrate the effects.

It also shows the close links between clinical and veterinary

food hygiene work and how both equally serve the consumer.

Since the introduction of official inspections of both livestock

and meat the veterinary surgeons responsible for clinical work and

meat inspection have cooperated closely, particularly when animals

have been slaughtered because of illness or other emergencies.

Identification of pathogens

Figure 4 show~ how latent infections may be identified in the

living animal. In general, this is possible by means of additional

Page 5: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

67 ~

Method Disease Relia~bility

AP,-FBSA (poultry)

AP (LA, ABR, KBR)

BU droppings (LA)

(see original)

Tuberculosis +

Brucellosis +

Salmonellosis +

Listeriosis (+)

Leptospirosis +

Toxoplasmosis +

Rickettsiosis

Trichinosis

Cysticercosis (§

Fig. 4. Methods of detecting zoonoses relevant to meat hygiene.

allergological, serological and bacteriological tests some of which

are still relatively expensive and must be carried out in the

laboratory.

The intracutaneous test using tuberculin has proved to be the

ideal method for diagnosing tuberculosis in cattle. A member of

our research group has therefore attempted to use the intracutaneous

test for detecting brucellosis in pigs and sheep and has produced

a brucellin on a polysaccharide base. A fairly extensive field test

in Cyprus and in the Soviet Union is now being conducted to

investigate its suitability for mass testing. We did similar work

on the diagnosis of leptospirosis. Obiger and Sch~nberg (1972,

1973) developed a leptospirin from the most important pathogenic

serotypes for an intracutaneous test which is also undergoing field

tests at the moment. If it were possible to use an intracutaneous

toxoplasmin test for the diagnosis of toxoplasmosis in pigs great

progress will have been achieved. Additional tests would be

needed to determine, whether the antigen used could be improved.

An additional improvement would doubtless be the fluorescence

antibody techniques which could replace the laborious Sabin-

Feldmann test. It remains to be seen how far the fluorescence

antibody "technique which we are testing for the diagnosis of

trichinellosis, etc., in cooperation with other Member countries

of the European Community, could replace the microscopic inspection

of meat

Nor is it yet certain whether our tests (walter and GrossMlaus

1972) on the diagnosis of cysticercosis in living cattle by means

of latex agglutinationand indirect haemagglutination and using

Page 6: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

68

an antigen prepared specially from taenia can ultimately be

successfully developed for practical use. Itwill essentially

depend on whether there are suitable~dentification~methods

aVailable for the proposed herd tests.

Identification of residues

Since 1973 German meat inspection legislation has provided a

legal basis for random samples (1% of all animals) and examination

of suspect slaughter animals. All animal carcases subjected to

bacteriological meat examination are also tested for inhibitory

substances. Because of the importance and occurrence of certain

residues, identification methods for

i. antibiotics

2. oestrogenic substances and

3. anti-thyroid preparations

were developed as priorities and made compulsory. Since rapid

methods are needed, a bioassay using a B. subtilis strain was

prescribed for identifying antibiotics, the mouse uterus test for

identifying oestrogens and histological examination of the thyroid

for identifying anti-thyroid preparations (e.g. methylthiouracil,

propylthiouracil). Although these methods have certain shortcomings

as regards specificity, they have contributed to a marked reduction

in positive findings. In many cases followUup tests on animal

stocks have confirmed the findings. Also, the regular observations

of a veterinary surgeon in practice skouldbe able to prevent

unwanted residues in farm animals.

Analysis of a sample of urine by the agar diffusion test

(Terplan, 1974) will reveal whether inhibitory substances were

administered; The substance must of course be eliminated via the

kidneys; this is true of most antibiotics and sulphonamides,

although bacitracin, sulphaguanidine and a few others are

exceptions. Detection of inhibitory substances in urine is about

as reliable as the compulsory method for detection in meat and

organs. Oestrogenic substances administered parenterally can

be detected by analysis of urine from the living animal. Thin

layer chromatography by the Schuller method (Karg, 1971) is most

suit~l~ for determining diethylstilboestrol. Oestradiol and its

derivatives may be detected by fluorimetry. There is, however,

no reliable method for detecting inti-thyroid substances in the

living animal. It is therefore both necessary and possible for

Page 7: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

69

clinicians and food hygienists to cooperate closely in protecting

consumers against residues of pharmacologically active substances.

Herd tests in practice

In an earlier publication (Grossklaus, 1973), an attempt was made

to provide a guide to stock tests for veterinary surgeons in practice.

This guide took into account the incubation time of various types

of zoonosis with the aim of providing stock destined for human

consumption with a valid certificate of health before slaughter.

By taking random samples and where necessary repeating tests,

especially in certain bacteriological and serological cases,

(e.g. 3 tests on faeces at three monthly intervals to detect

salmonella, and determining a titration curve in toxoplasmosis),

stock tests do seem feasible. In addition tests for residues would

need to be repeated shortly before slaughter.

But a number of conditions must still be fulfilled before these

tests reach the practical stage. This has led the food hygiene

section of the German Association of Veterinary Medicine to form a

working group concerned exclusively with these problems. It would

be most useful if the World Association of Veterinary Food

Hygienists (WAVFH) could also work on the problems. Figure 5

shows in diagrammatic form the different stages of a herd test.

Veterinary surgeon

Herd

V e t e r i n a r y i n s p e c t i o n o f f i c e and s l a u g h t e r - house l a b o r a t o r y

Therapeutic measures Waiting period Possible postponement Clinical, of slaughter

allergological, serological, and ---}Diagnosis bacteriological "~ examinations Health certificate for

slaughterhouse

Rejection of Approval of diseasedanimals healthy stock

Slaughter animal examination Meat examination

Fig. 5. The different stages of a herd test and the consequences for meat hygiene.

CONCLUSIONS

In considering "The CorrelatiOn of activities in veterinary food-

hygiene work and yeterinary-clinilcai practice"~ .I think that the

comments on existing cooperation and what will be necessary in future

Page 8: Herd tests on meat livestock to protect consumers from zoonotic pathogens and chemical residues

70

have shown when herd tests should be used for the early detection

of latent infections and harmful residues of chemical substances in

meat livestock. Figure 6 clearly shows how much clinicians and

food hygienists or clinical and food hygiene knowledge complement

one another in consumer protection. It also shows the many aspects

of the veterinary surgeon's work in helping to protect both the

environment and the health of the general public. Training should

therefore be increasingly concentrated on these tasks.

National and international legislation

Animal hygiene Control of livestock (breeding, housing epidemics and zoonoses disease)

E x a m i n a t i o n o f E n v i r o n m e n t a l p r o t e c t i o n a n i m a l s f o r slaughter and ) and health protection of q Animal nutrition

the general public meat inspection / / ~ I

Foodstuffs inspection Removal of dung and waste water

Removal of carcases

Fig. 6. Participation of various special fields of veterinary medicine in environmental protection and health protection of the general public.

REFERENCES

Bartels, H., 1963. Lecture to the German Association of Veterinary Medicine, 6: iO. 1962. Special edition Parey Verlag, Berlin and Hamburg.

Bartels, H., 1966. Schlacht-Viehhof-Ztg., 66: 508-514. Dutschke, G., 1966. Schlacht-Viehhof-Ztg., 66: 4-8. Grossklaus, D., 1968. Schlacht-Viehhof-Ztg., 68: 461-468. Grossklaus, D., 1973. Fleischwirtshaft, 53: 1721-1725. Kampelmacher, E.H., 1969. Paper read to the 5th Symposium World

Ass. Vet. Food Hyg., Opatija (Yugoslavia). Karg, H., 1971. Paper read to the Conference of the German

Association of Veterinary Medicine on 30.9 in Freiburg. Obiger, G. and Sch~nberg, A., 1972. Fleischwirtschaft, 52:

1458-1460. Obiger, G. and Sch~nberg, A., 1973. Fleischwirtschaft, 53: 1452-1456 Scheibner, E., 1970. Unpublished studies. Terplan, G., 1974. Paper read to the 16th meeting of the Food

Hygiene Section of the German Association of Veterinary Medicine, Garmisch-Partenkirchen 24-27 September.

Walther, M. and Grossklaus, D., 1972. Zbl. Vet. Med. (B), 19: 309-319.

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71

KuRZFASSUNG

Grossklaus, D., 1978. Bestandsuntersuchungen bei Schlachttieren zum zum Schutze des Verbrauchers vor Zoonoseerzegeen und chemischen Ruckst~nden. Vet. Sci. Commun., 2: 63-72 (in Englisch).

Die klinische T~tigkeit des Tierarztes beeinflusst wesentlich die Arbeit des tier~rztlichen Lebensmittelhygienikers. Dies trifft besonders for die rechtzeitige klinische, allergologische, serologische und bakteriologisch-virologische Untersuchung von Schlachttieren in ihren Best~nden zu, wie sie u.a. von Bartels, Kampelmacher und Grossklaus vorgeschlagen wurde. Sie soll u.a. die Diagnose inapparent verlaufender Zoonosen erm6glichen, die sonst im Rahmen der amtlichen Fleischuntersuchung unerkannt bleiben. Der pathologisch-anatomische Befund aus der Fleischuntersuchung ist zudem wichtig fflr den Kliniker. Hinzu kommen erforderliche Massnahmen zur Ausschaltung von toxikologisch relevanten R~ckst~nden~ pharmakologisch wirksamer Substanzen. Anhand eigener Untersuchungen web, den Vorschl~ge f~r sog. Bestandsuntersuchungen unterbreitet die in der Lage sein k~nnten, den internationalen Handel mit vom Tier stammenden Lebensmitteln sicherer zu gestalten und zu f~rdern.

REsuME

Grossklaus, D., 1978. Inspection v~t~rinaire des animaux de boucherie au niveau des @l~vages pour protEger les consommateurs contre les agents de zoonoses et les residus chimiques. Vet. Sci. Commun., 2: 63-72 (en anglais).

L'action du v~tErinaire praticien a une influence primordiale sur le travail du v~tErinaire hygiEniste. Cela est particuli~rement vras pour l'examen clinique, allergologique, sErologique et bactEriologique des animaux de boucherie, au niveau des ~levages, propose par des auteurs comme Bartels, Kampelmacher et Grossklaus. Il doit rendre possible le diagnostic des zoonoses inapparentes qui risqueraient de passer inapercues au stade de l'inspection des viandes. Du reste, le diagnostic anatomo-pathologique resultant de l'inspection des viandes est important pour le clinicien. Ii faut ajouter les mesures n~cessaires pour ~liminer les r~sidus toxiques provenant de substances pharmacologiques actives. En se basant sur ses propres Etudes, l'auteur fait des propositions pour des examens dits des "troupeaux" qui pourraient rendre plus sQr et plus efficace le commerce international des dentEes d'origine animale.

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7~

RIASSUNTO

Grossk!a~s,~.~.~i1978.~ Ispezione veterinaria degli animali da macell~ neglial~evamenti~p~ la protezione dei consumatori contro gli agenti di~z!oon~si~ed!i residui chimici. Vet. Sci. Commun., 2:: 63-72 (in Inglese).

L'at~iVit~ del medico veterinario influenza sensibilmente il lavoro~dell'~ge~ista Veterinario-alimentare. QuestO vale in partlcolere per: l'4same clinico, allergico, sierologico e batteri61ogfCodegi~ animali da macello negli allevamenti, proposti da aut'or~ quali Bartels, Kampelmacher e Grossklaus. Gli esami'debbono permettere la diagnosi delle zoonosi inapparenti che rischierebbero di passare inosservate in fase di ispezione delle carni. Pertanto la diagnosi anas risultante dall'isPezione delle carni ~ importante anche per il clinico. A cio' sl devono aggiungere misure atte ad eliminare i residui tossici provenienti dalle sostanze farmacologiche attive. Basandosi sui suof studi, l'autore fa proposte relative agli esami dett• di "mandria" che potrebbero rendere pi~ sicuro e efficace il commercio internazionale ~egli alimenti di origine animale.