BSE – World’s Situation and The Danger of Outbreak of the Disease in Israel
(Following the methodology of the Scientific Steering Committee of the EU
on the Geographical Risk of BSE, 6 July 2000)
Oded Nir (Markusfeld) BVSC, MRCVS
CVO, Israel

Since BSE first appeared in England in the late eighties, the Israeli veterinary Services (IVSAH) follows the developments outside Israel routinely, and reacts accordingly.

No cases of BSE have yet been diagnosed in Israel. The risk of an outbreak of the disease in Israel depends mainly on the:

(a) probabilities that the causative agent of the disease (the prion?) entered the country through infected live cattle or contaminated cattle meat and bone meal, MBM (the “external threat”); and

(b) the infected material being recycled (rendered) and introduced into the feed chain of the local cattle (the “internal risk”).

If vCJD in human is associated with BSE in cattle, such cases could be the result of eating contaminated meat either produced in Israel or imported into the country.

The External Threat

The external threat is the outcome of the probabilities that BSE actually entered the country through live cattle or MBM and the amounts imported since the late eighties.

Import of Live Animals into Israel

Live cattle have not been imported from GB since 1974. Import from all other countries, since 1992, was allowed only from herds, which had not been fed with MBMs, and - if from countries known to be infected with BSE (e.g. France) - only from areas free of BSE. The imports since 1980 are described in the Table 1.

Table 1:
 

Year

Country

Amount

Purpose (all beef)

1980

“Europe”

90

Bull calves for breeding

1981

“Europe”

115

Bull calves for breeding

1982

No import

 

 

1983

France

93

Bull calves for breeding

1984

France

114

Bull calves for breeding

1985

France

104

Bull calves for breeding

1986

France, Germany, Germany

130, 11, 500

Bull & female calves, heifers for breeding

1987

France, France, Germany

156, 68, 725

Bull & female calves, heifers for breeding

1988

France

67

Bull calves for breeding

1989

France

55

Bull calves for breeding

1990

France

55

Bull calves for breeding

1991

No import

 

 

1992

France

262

Bull calves for breeding

1993

France, Germany 

886, 94

Fattening, heifers for breeding

1994

Germany, France & Germany

70, 231

Fattening, bull calves for breeding

1995

France & Germany, France 

68, 394, 150

Bull calves for breeding, slaughtering*

1996

France

50, 63

Heifers, bull calves for breeding

1997

France

87

Bull calves for breeding

1998

France

110, 570

Bull calves for breeding, slaughtering*

1999

France

62

Bull calves for breeding

2000

Germany

132

Bull calves for breeding

* All bull calves for slaughtering were under the age of 18 months, slaughtered within 8 days of arrival to Israel.

Import of MBM into Israel

The import of MBM of mammalian origin from the UK and from all other countries was prohibited in 1988 and 1990 respectively. The import of poultry MBM was permitted only from plants authorised by the local veterinary authorities. The purpose of the authorisation was to ensure that the MBM is produced in the plant specifically allocated for poultry MBM, and follows the specified requirements set out by the IVSAH.

The imported MBMs have been tested since 1996 against mammalian antigens to ensure that the protein does not come from mammalian sources. It came to our notice only recently that mammalian antigens are destroyed in the process of rendering that involves heat treatment above 121oC. Prions, the agents possibly responsible for BSE, are only destroyed at 133oC. The test used could not therefore have guaranteed that imported “poultry” MBMs do not contain mammalians’ proteins. Shipments from GB (the most risky source) are accompanied by MAFF’s labs’ certificates based on tests, which diagnose mammalian antigens even after heating to 140oC for 90 minutes. The import of MBM (in tons),from all animal species, in the relevant period from European countries is described in the Tables 2:

Table 2:
 

 

United Kingdom 

France

Holland

Denmark

 


Year

Poultry
By-
Product

Feather
Meal

Poultry
By-
Product

Feather
Meal

Poultry
By-
Product

Feather
Meal

Poultry
By-
Product

Feather
Meal

Fish
Meal

1986

 

 

40*

 

 

 

 

 

1730

1987

 

 

 

 

 

 

 

 

1680

1988

17

 

20*

 

597*

22

 

 

1092

1989

3844

29

 

 

 

343

3947*

 

489

1990

3590

1629

**40

399

**1470

1419

**1076

 

461

1991

8937

3726

173

1028

 

 

 

 

244

1992

7928

4482

165

409

 

91

***2594

 

223

1993

8164

6423

328

1031

 

93

1157

 

82

1994

2064

3131

598

2048

294

1015

898

21

167

1995

2002

3096

305

840

 

766

180

 

175

1996

443

1288

 

 

 

 

 

 

 

1997

3247

881

485

1593

145

1940

 

 

177

1998

5258

1334

541

956

 

619

 

 

1311

1999

6137

339

337

535

 

405

 

 

125

2000

1111

623

430

 

 

850

 

 

117

  

 

Belgium

Germany

Italy

Spain

 


Year

Poultry
By-
Product

Feather
Meal

Poultry
By- Product

Feather
Meal

Poultry
By- Product

Feather
Meal

Poultry
By- Product

Feather
Meal

Fish
Meal

1986

810*

 

 

 

1200*

 

1450*

790

 

1987

1150*

10

1771*

 

1000*

 

1752*

47

 

1988

802*

 

1053*

 

6737*

 

2808*

1298

 

1989

1100*

5

6374*

264

1820*

 

2929*

2410

 

1990

1220**

5

2688**

470

300**

 

1110**

689

 

1991

 

 

343

 

3548

98

316

191

 

1992

 

 

507

 

3872

304

 

 

75

1993

 

 

 

 

 

 

 

 

 

1994

 

 

 

 

3572

55

 

 

 

1995

 

 

 

 

1866

 

 

 

 

1996

 

 

 

 

 

 

 

 

 

1997

 

 

55

 

18

 

 

 

 

1998

 

 

110

 

 

 

 

 

 

1999

 

 

 

 

 

 

 

 

 

2000

 

 

****23

 

 

 

 

 

 

*Poultry by-product might have included mammalian MBM before 1989.

** A total ban on all mammalian MBM was imposed in 07/1990.

*** Porcine MBM (from a plant dealing exclusively with pig material).

**** Poultry blood meal.

The external threat, if exists, could be summed up in the penetration of unknown quantities of BSE agents in into Israel, through MBM exported as “poultry MBM”, if in spite of the certification of the veterinary authorities in the exporting countries, the poultry MBMs were contaminated to various degrees with mammalian MBMs (and therefore possibly with the BSE agents). A complete fraud (selling cattle MBM as poultry one) is practically impossible because of the different contents of mammalian MBMs, poultry MBMs and feathers’ meals, which are obviously checked by the importing feed mixtures manufacturers (Table 3):

Table 3:
 

 

Ruminant meals

Poultry Meals

 

Meat

Meat & Bone

Feather 

By-Product

Crude Protein (%)

55.0

50.0

80.0

60.0

Crude Fat (%)

10.0

10.0

6.0

12.0

Crude Ash (%)

15.0

28.8

2.8

15.5

Calcium (%)

8.5

10.1

0.3

3.0

Phosphorus (%)

3.5

5.0

0.6

1.7

The risk of introduction of the disease through the imported bulls could be estimated as negligible.

The Internal Threat or the System Stability

The ability of the Israeli internal system to minimise the spread of the agent responsible for BSE, were it to enter the country, depends on preventing the recycling of infected material (rendering) into the feed chain.

Since 1996, Israel prohibits by law (and in practice) recycling of mammals. Recycling of poultry is allowed. All mammalian wastes (carcasses and organs) are buried in authorised sites, and since December 2000 are directed to one central incinerator. Cattle in Israel are not fed with mammalian MBM, in practice since the early seventies due to economical considerations, and by law since August 1996. Poultry and fishmeals are still allowed to be fed to cattle.

It is possible to estimate the system stability as good, and the internal threat as minimal.

The Actual Hazard (the Interaction of the Total Threat and Stability in Time)

The risk of an outbreak of BSE in Israel is the result of the interaction of the system stability and the external threat in the relevant period. In a stable system exposed to an external threat, the internal threat will be minimal, because without recycling the penetrating disease agent is bound to disappear with time. In an unstable system exposed to an external threat, the agent will spread through the cattle MBM. Some of the cattle, when reaching the “right” age, will turn out to be clinical cases of BSE. Others will be recycled, magnifying the amount of infected material and developing the disease into an epidemic.

The minimal period needed to diagnose the internal threat in an unstable country exposed to BSE is at least one “incubation period” of 5 years. The period could be the multiplication of few such periods and longer according to the extent of exposure to the BSE agent (the system stability, the size of the cattle population, the age dynamics of the population) and the quality of the monitoring system.

Of the four possible combinations, we estimate that the expected one in Israel is either [a stable system * none or a minimal external threat] or [a stable system * a high external threat]. The first alternative is the less hazardous, but even in the second one the system is able, with time, to remove the BSE agents. The choice between those two alternatives (the actual situation in Israel) depends in our case on the credibility of the British, French and German Veterinary Services and the efficiency of the control measures applied by the IVSAH.

It can not be over-emphasised that all mutual veterinary activities that accompany international trade, regarding BSE as well as all other diseases, are necessarily based on that credibility and certification.

The Actual Situation, the Efficiency of the Monitoring System

The efficiency of the monitoring system depends on the efficiency of the clinical system, the validity of the sample monitored, and the diagnostic methods applied.

The clinical monitoring and reporting system in the Israeli cattle industry is probably among the most efficient in the world, due to the fact that over 90% of the bovine veterinary practice in Israel is comprehensive, given under contract, and provided by a central, country-wide organisation ("Hachaklait"). Compensation for wastes and fallen stock is regulated by a state-compulsory insurance scheme, so that clinical follow up of fallen stock is guaranteed. The awareness of the system to the disease is well developed through lectures and pamphlets; the first of them described the symptoms of the disease to all the parties involved as early as 1989. The disease is notifiable in Israel since April 1992.

The present diagnostic methods allow diagnosis of the BSE agent only after death, and only when the disease is in its clinical stage or towards the end of the incubation period. The Pathology Department of the Kimron Veterinary Institute (KVI) is able to diagnose the disease since 1992 and maintains active surveillance.

In the years 1997 to 1999 for example, the KVI examined 586 brains of cows older than 36 months, all proved to be BSE negative. The Israeli bovine population in that age group is about 120,000; it is possible to calculate the probabilities of diagnosing infected cows if the disease actually exists in Israel. In a random sample, 2800 brains of cattle should have been examined annually to establish that the disease incidence in Israel is smaller than 0.1%. In Israel most of the brains of cattle showing nervous symptoms are sent to the KVI because of the compulsory obligation to examine it for rabies. 162 cows that showed nervous symptoms before their death were examined in the KVI in the period 1997 through 1999. It is possible to estimate on basis of that selected sample that the disease incidence of BSE, if exists, is smaller than 0.01%.

Import of Bovine Meat

It is believed that the prions responsible for BSE are not found in cattle younger than 30 months. No meat from Britain was allowed import since - the latest - 1986 (an official ban was applied in 1989). Import from other countries was allowed after evaluating the quality and credibility of the exporting country's State Veterinary Services by means of a detailed questionnaire with special emphasis upon BSE surveillance and the use of MBMs, and receiving a valid BSE risk analysis as demanded by the guidance of the OIE until mid December 2000. In practice we set an age limit for imported meat (36 months from South America, and 24 months from Europe).   

Updated 1 March 2001