The Committee reviewed the recommendations made at the last meeting in April 1998, and notes that the majority have been carried forward. A small number of items require further development including items 3) RENDERING, 4) GELATIN MANUFACTURE and 6) CONTINGENCY PLANS. Further recommendations on these aspects are given below.

The Committee agreed to provisionally book dates for the fourth meeting, to be held in April 2001.

In regard to diagnosis the Committee notes the further progress made and particularly commends the attendance of Argentine experts at centres of excellence to further enhance the quality of their diagnostic capability.

In regard to surveillance the Committee commends the further development of animal and human TSE surveillance.

As regards to scrapie (item 10) the Committee noted that the OIE had produced a new International Animal Health Code chapter on scrapie and Argentina has responded by producing a new document detailing the risk factors in Argentina and which concluded that Argentina is, for practical purposes, a scrapie-free country.

In regard to ITEM 12 the suspected case of FFI is now reported to be due to a codon 200 mutation and is a case of CJD with insomnia as a clinical feature.

The Committee has thoroughly reviewed and discussed the presentations made according to the programme. Dr. Kihm reviewed the international situation with regard to the course of the epidemic of BSE, which showed a continued and steady decline in the number of cases in the UK and Switzerland. In other continental countries the epidemic is still rising. International regulations with regard to BSE were also reviewed, in particular the new version of the OIE International Animal Health Code chapter 3.2.13 on BSE referred to establishing the BSE status for a given country, and the Geographic Risk Assessment in train by the EC by establishing the parameters of stability and challenge.

Dr. Detwiler discussed the new tests used in the diagnosis of TSE and noted significant improvements of new tests undergoing validation procedures. Some of these tests can be used in living animals and some can be applied for the detection of asymptomatic PrP^Sc-positive animals. Some of the tests were able to detect PrP^Sc in the tonsils of sheep as young as 4 months old. Studies of natural scrapie in sheep have confirmed the importance of 3 amino acid codons in the sheep PrP gene (136, 154, 171). These were originally shown to be associated with different incubation periods following experimental challenge with different strains of scrapie agent. Currently it is thought that certain alleles may confer a certain degree of resistance or susceptibility. It is unknown as to whether the resistance is for infectivity as well as for clinical disease.

Dr. Heim reported on the Swiss experience on the additional active targeted surveillance system with the Prionic test in order to improve the detection of infected animals. They have used three target populations (>15,000 samples/year) fallen animals, emergency slaughtered cows and routinely slaughtered cattle >24 months old. In all three categories infected cows were found. The results showed that most positive cows were found in the fallen stock and emergency slaughtered cows confirming that these are the high-risk cohorts. It was concluded that a targeted surveillance scheme, applied particularly to all fallen stock and emergency slaughtered animals, is the most effective approach to detect a rare disease such as BSE on a country wide scale.

Dr. Piccardo summarized molecular aspects relevant for the diagnosis of prion diseases in humans and presented a brief report on aspects discussed at the recent US Food and Drug Administration meeting on the risk of blood and blood-derived products in relation to TSE.

Dr. Bradley reviewed many of the obscure points related to the TSE, and especially scrapie, including the role of parasites in the causation of animal TSE, studies on the pathogenesis of experimental rodent scrapie, maternal transmission in sheep and goats, optimum conditions for long term storage of tissues for SAF detection and immunoblotting, PrP^Sc and SAF detection in tissues other than brain, surgical treatment and CJD risk, stunning, pithing and BSE, the possibility of in vitro infectious PrP production and infectivity in skeletal muscle.

The presentation of Argentina reviewed the chronology of activities performed since the initiation of the TSE prevention project in 1989, the latest documents prepared for publication and the presentation of geographic risk to the EC, the results of the surveillance on brains from TSE-susceptible species, the detection of PrP genotypes in sheep breeds in Argentina, the continuous updating of the legal framework, the profile of the animal feed industry and its surveillance programme and the surveillance programme for human TSE.

CONCLUSIONS

The Committee concludes that in accordance with the OIE recommendations and for practical purposes, Argentina can be regarded as a free country for animal TSE.

In regard to the outstanding items from recommendations made in April 1998 the following comments and recommendations are made:

Item 3) RENDERING: the Committee notes the previous recommendations have been partially completed and recommends the outstanding information should be collected.

Item 4) GELATIN MANUFACTURE: the Committee notes that no gelatin is imported for use in animal feed and recommends outstanding information should be collected. The Committee recommends that information should be gathered and received by the Department of Health in respect to importation of gelatin prepared from bovine bones for human uses, (e.g., capsules).

In regard to item 6) CONTINGENCY PLANS, the Committee notes these have been initiated for several diseases including BSE and recommends progress is continued.

The Committee recommends that, in regard to breeding sheep for "resistance" to scrapie, a careful watch is kept on the world literature on this subject and at present an open mind on encouraging or discouraging this practice is kept.

The Committee recommends that, in regard to TSE surveillance of sheep, past efforts be continued and particular emphasis be placed on breeds known to develop scrapie including those used to improve meat quality notwithstanding the country or flock of origin.

The Committee emphasises that there is a need to continue the focus on the collection of high quality data regarding the prevention and surveillance programme in Argentina.

THE COMMITTEE FURTHER RECOMMENDS TO:

• continuously update the documental basis of the TSE Assessments.
• incorporate new technology for TSE diagnosis as appropriate.
• maintain and improve the measures to mitigate the endogenous risk from feed.
• maintain a close contact with the human TSE programme.
• extend the project to neighbouring countries in order to facilitate trade between participating countries and between these countries and others.

The Committee notes that the current excellent TSE status of Argentina depends upon the continued high level of surveillance of human and animal TSE and can only be maintained if adequate funds are provided.

Volver al índice