| Laboratory Diagnosis and Differential Diagnosis of Rinderpest | |
| - the role of the Reference Laboratories | John Anderson |
| Diagnostic technology support to GREP by the FAO/IAEA Division | Martyn Jeggo |
| Training field veterinarians in recognition of tropical epidemic diseases | Gavin Thomson |
John Anderson7
1. Introduction
The Institute for Animal Health, Pirbright was appointed as the FAO World Reference Laboratory for Rinderpest (WRLR) in October 1994. The WRLR not only provides a diagnostic service but also acts as an interface between individual countries, the Regional Reference Laboratories, Regional Co-ordinating Units (e.g. PARC), FAO and the Joint Division FAO/IAEA in Vienna. The role of the Regional Reference Laboratories and the WRLR is constantly changing to adjust to the ever changing needs at different phases of the eradication campaign.
2. Diagnostic service
The most obvious role is to offer a diagnostic service. Rapid, accurate diagnosis followed by swift implementation of suitable control measures are the key factors in rinderpest eradication. Staff in the field must be trained in clinical diagnosis and also in the collection of suitable clinical specimens. One of the main constraints to obtaining good clinical specimens has been the lack of suitable containers or boxes to transport the specimens in good condition to the Regional or World Reference Laboratories. Boxes suitable for transportation of specimens will now be supplied by the WRLR along with instructions on the samples required and details of shipping requirements. These boxes fulfil all the airline (IATA) requirements for transportation of biological samples and are licensed for use with dry ice.
Some national laboratories may have diagnostic capability and undertake laboratory diagnosis before submitting samples to the Regional or World Reference Laboratories. Other laboratories may have no diagnostic capability and may always submit samples to their Regional laboratory. The assays used in national and regional laboratories may vary from agar gel immunodiffusion test through to the polymerase chain reaction (PCR). Regardless of the national laboratory's diagnostic capability, it is essential that samples are submitted as quickly as possible to the WRLR for molecular characterisation. This may allow tracing of the origin of the outbreak and greatly affect the choice of control measures. Ideally, duplicate samples should be submitted simultaneously to the Regional laboratory and the WRLR. This is not to circumvent the national laboratory, but to speed up the response time to any new outbreak. If samples are examined in national and regional laboratories before being sent to the WRLR not only does this cause a delay, but there is always the risk of contaminating the sample. The WRLR also rely on the regular submission of samples to build up their library of nucleotide sequence data, essential to the mapping and tracing of outbreaks.
At present the main emphasis is being placed on rinderpest diagnosis. As the eradication campaign moves into the later phases, differential diagnosis will become more important. Countries which have declared themselves free from disease should not be satisfied with a “rinderpest negative” result and should endeavour to identify the cause of the “suspect” outbreak. The reference laboratories will in future be developing greater differential diagnostic capability. One of the main advantages of the WRLR being based at IAH, Pirbright is the excellent secure large animal accommodation allowing experimental infection of suitable animals.
3. Communication interface
A further role is to act as a communication interface. In the past, one of the main problems has been the difficulty of communicating between the many organisations involved in the eradication programme. At any one time FAO, IAEA, OIE, PARC, WRLR, EMVT, the Regional Laboratory, National Laboratory, National Veterinary Authority and the field officer, plus many other interested parties, all have the need to communicate. This another problem which is being addressed by FAO, Telos and the WRLR. We are in the process of designing a disease information and communication network which will allow “real time” access to the WRLR database to give information on current sample status.
4. Training role
All staff involved in the eradication campaign must be trained to a suitable standard and have access to “international standard” information. The IAH, Pirbright has a long history of training scientists in rinderpest diagnosis and sero-monitoring and continues to both train visiting scientists in diagnostic techniques and also run training courses overseas.
In an effort to improve technology transfer, the IAH instigated the formation of the Advanced Veterinary Information System (AVIS) - a consortium consisting of IAH, FAO, OIE and Telos. The aim of AVIS is to provide world class information relating to all aspects of animal health in the form of multi-media interactive computer soft-ware programmes. A suite of modules will be written for each disease covering all aspects of clinical diagnosis, field control, laboratory diagnosis, epidemiology and public awareness. The complete set of modules on rinderpest are now available and further modules on foot and mouth disease, poultry diseases, lumpy skin, PPR, CBPP and bluetongue are underway. The programmes can be used as training tools, for raising public awareness, as reference material for laboratory techniques and in general for standardising the knowledge base throughout the eradication campaign.
5. Research and Development
Reference laboratories also have a major role in research and development. This may involve the development or validation of improved diagnostic assays or vaccines.
During the early stages of the eradication campaigns the emphasis was on mass vaccination and assessing the success of the campaign by measuring herd immunity levels. The reference laboratories developed and validated sensitive, specific assays required for sero-monitoring. The technology was transferred and scientists trained in the new techniques through a fruitful collaboration between the Reference Laboratories and the Joint Division FAO/IAEA in Vienna.
As the campaign progresses and fewer countries are reporting disease countries are being encouraged to cease vaccination and change to active disease surveillance. If countries are to take this major step the provision of rapid, sensitive, specific pen-side diagnostic tests may allay their fears and reduce the response time in implementing control measures in what may be a predoninantly susceptible population. Funded through ODA and in collaboration with scientists from Unipath, the WRLR have developed such a pen-side diagnostic test. The test is rinderpest-specific and using eye-swab material will give an answer within 5 minutes. Further devices are being developed for the diagnosis of PPRV, FMDV, BVD and BTV. Preliminary field trials are underway in Ethiopia and full scale trials are planned in other rinderpest endemic areas. Once an outbreak has been identified, it is important that the correct control measures are implemented. A further AVIS programme on strategic planning and emergency preparedness is envisaged which, being fully interactive, will guide national co-ordinators through the correct procedures.
Further research has centred on the development of improved thermostable vaccines. In this case the Regional Laboratory in Kenya have been invaluable for running field trials of the capripox recombinant vaccine.
The WRLR also acts as a research facility. Many overseas scientists have worked at IAH, Pirbright either as fellowship students or on collaborative research projects using our unique facilities. One of the fruits of these collaborative projects has been the development of the homologous PPRV vaccine produced in conjunction with Adama Diallo from CIRAD-EMVT.
6. External quality control and laboratory accreditation
Some form of external quality control system is essential for all the laboratories involved in the eradication campaign. This ensures tests are working within acceptable limits, instils confidence in other laboratory's results and highlights any local problems such as water quality or lack of training. In collaboration with the Joint Division FAO/IAEA, Vienna, the WRLR will provide suitable panels of sera for external quality control to all laboratories involved in their “Seromonitoring Network”. The results of the QC exercise will be analysed by the Animal Health and Production Section. A similar service should be provided for those laboratories which are not included in the IAEA Network.
International acceptance of the standard of work carried out in all laboratories will become even more important as the eradication campaign progresses. In the final stages of the OIE Pathway to Eradication, countries must supply documentation to prove that there has been an efficient disease surveillance system in place and that test results have been of an approved standard. In a collaborative effort with Telos, Joint Division FAO/IAEA, OECD and world leaders in laboratory accreditation we are hoping to devise a system for setting world standards for veterinary laboratories. This will eventually lead to a further multi-media programme to lead laboratories through the complex process of laboratory accreditation.
7. Conclusions
The primary diagnostic role of the Reference Laboratories will always remain but the other roles of research and development, external quality control, training and technology transfer are equally important. It is imperative that the Reference Laboratories are maintained and funded adequately to allow them to respond to the ever changes requirements as we move towards the final stages of eradication.
Martyn Jeggo8
The FAO/IAEA support programme in animal health focusses on providing assistance to national veterinary laboratories to utilize ELISA and molecular based technologies to conduct epidemiologically studies for developing soundly based control/eradication programmes and measuring the effectiveness of such programmes. This programme commenced 10 years ago and now has activities in some 70 countries involving primarily rinderpest, brucellosis, foot-and-mouth disease, trypanosomiasis, tick-borne diseases and bovine leukosis.
Diagnostic support to GREP for disease diagnosis and surveillance through the Animal Production and Health Section of the Joint FAO/IAEA Division aims to assist national authorities to conduct sero-monitoring for assessing effectiveness of national vaccination programmes, to assist national and regional authorities to carry out disease surveillance as part of completing the OIE pathway and ensuring final eradication of rinderpest and to assist in ensuring reliability and assurance of results generated from the above activities.
In providing this support a variety of diagnostic tools have been developed and others are being developed as the needs of GREP change. Such development work is carried out primarily at research institutes such as the Pirbright Laboratory of the Institute for Animal Health, UK, but are adapted for use in developing countries through our own laboratories in Austria (the FAO/IAEA Central Laboratory for ELISA and Molecular Techniques in Animal Disease Diagnosis) and counterpart scientists. Central to our support during the past 10 years has been the development of a number of ELISA kits for rinderpest and PPR antibody and antigen detection. Such assays are now internationally standardized and validated and are available (both through FAO and commercially sources) to all GREP countries. This unique approach of standardization of assays throughout all GREP countries is considered a key element in ensuring the effectiveness of our programme, in being able to operate an external quality assurance programme and enabling comparison to be made between different countries and regions.
As countries cease vaccination and move down the OIE Pathway it is clear that they need effective tools for rapid confirmation of a field diagnosis of rinderpest, both at farm and in national and regional laboratories. A dip stick for pen-side confirmation of rinderpest has been developed and is currently being validated by the World Reference Laboratory for Rinderpest, Pirbright Laboratory, and it is anticipated that this will form a key component of our diagnostic armoury in the near future. Equally important is the need to rapidly confirm a diagnosis in the laboratory and isolate the causative virus to enable molecular-based epidemiological mapping of virus activity to be carried out. Central to this approach is the use of the polymerase chain reaction (PCR) and the transfer of this technology and support for its use in selected national and regional laboratories is now a component of our support programme.
Linked to the supply of diagnostic tools are a number of crucial ancillary support activities that are aimed at ensuring the effective use of these tools. These include the development and supply of standardized computer software for ELISA data storage and management, the development and use of defined epidemiological approaches and specific software programs in this area, the use of extensive internal and external quality assurance protocols and the publication of reports from the regions on an annual basis. It is foreseen that in the future the external quality assurance programme will result in an FAO/IAEA laboratory accreditation system that will help ensure to all interested parties (national Governments, donor and other international organizations, trading partners) that the results emanating from a particular laboratory can be relied upon as valid and correct.
8 Head, Animal Production and Health Section, Joint FAO/IAEA Division, Vienna, Austria.
Support is provided for these activities through two main mechanisms. Firstly through the award of FAO/IAEA Research Contracts to individual institutes. Such contracts usually form part of an FAO/IAEA Coordinated Research Programme which can be funded both internally using FAO/IAEA regular budget funds or through external funding sources (e.g. Swedish International Development Agency, European Commission). Secondly through IAEA Technical Cooperation Projects which can be national, regional and even global. Significant further support is now to be provided directly from FAOs own programmes such as EMPRES.
In summary the key features of this support programme that are considered crucial for an effective achievement of GREP and final rinderpest eradication are:
international coordination of this activity
the establishment and support of regional networks
the use throughout GREP of internationally standardized and validated diagnostic assays and procedures
the routine operation of an External Quality Assurance Programme
routine and standardized reporting (at least annually)
regular regional meetings and workshops (at least annually)
Gavin R. Thomson9
INTRODUCTION
One of the problems that confronts developed and developing nations alike is the need to have veterinarians deployed in the field who are in a position to recognize potentially serious epidemics at an early stage and who are able to take appropriate action immediately. In developed countries the problem is often that the disease is exotic to the country concerned and therefore although field veterinarians may be well trained in the theoretical aspects of disease diagnosis and control, they have not previously “seen” these diseases. There are, however, courses in a number of countries, eg. USA, Australia, Spain and UK., which address this problem. In general though these courses deal with these diseases from the point of view that they pose an external threat. In developing countries, on the other hand, although the diseases may not be exotic, few young veterinarians have first-hand experience of them because of (i) a lack of visual material during their undergraduate training and (ii) the infrequent and episodic nature of disease prevalence and lack of resources to move people around the (often large) country to expose them to interesting and important diseases as and when they occur.
In South Africa some currently important epidemic diseases in the region such as rinderpest and contagious bovine pleuropneumonia (CBPP) were eradicated many years ago and therefore few people in the country have detailed knowledge of these diseases. Others such as foot and mouth disease (FMD) occur so infrequently (the last outbreak in domestic animals was in 1983) that a somewhat similar situation exists with this disease. African swine fever (ASF) occurs almost every year but in only a small part of the country so that veterinarians from the south of the country, for example, never encounter it although, of course, potentially it could occur anywhere at any time.
It was recognized about 10 years ago that training of veterinarians in South Africa was inadequate in the field of infectious diseases in general and epidemic diseases in particular and in order to correct this a reference book entitled “Infectious Diseases of Livestock with Special Reference to Southern Africa” was published through Oxford University Press in 1994. An attempt was made to provide adequate colour photographs and other illustrations to support the text. Thus there is now an authoritative reference source on important animal diseases in southern Africa.
Following the completion of the above book a course dedicated to training veterinarians in the field in the recognition of important diseases was developed jointly by the Faculty of Veterinary Science, Department of Veterinary Tropical Diseases, the Onderstepoort Institute for Exotic Diseases (OIED) and the Onderstepoort Veterinary Institute. This course, the duration of which is a week, is aimed primarily at providing visual material and practical instruction in the recognition and control of diseases important to southern Africa.
Initially the course was aimed only at South Africans and addressed only a limited number of diseases. Through the generous support of the FAO, it has been possible in the two most recent courses to invite veterinarians from other countries in the region to attend and to expand the number of diseases covered. In addition, foreign experts are used where sufficient expertise is not available in South Africa - once again through the support of FAO. For foreign students, especially those from relatively poor countries, all their expenses are paid through sponsorship, viz., travel, accommodation, course fees and a small daily allowance. This amounts to about $3 000 per student and so far has been generously donated by FAO.
As far as possible, we attempt to reproduce diseases in the high security stables of the OIED but this, of course, is sometimes impossible, for example, in the case of zoonotic diseases such as Rift Valley fever or those that are difficult to reproduce eg. CBPP. For these as well as ethical considerations the use of live animals is being phased out as far as possible by the production and use of videos and other visual material. It is hoped that there will be increasing use of interactive computer programmes such as the Advanced Veterinary Information Systems (AVIS) produced by Telos.
For the next course scheduled for September 1996 the following diseases will be addressed:
foot and mouth disease
African swine fever
rinderpest - with the help of foreign expertise
peste des petits ruminants - with the help of foreign expertise
CBPP - with the help of foreign expertise
rabies
anthrax
Rift Valley fever
lumpy skin disease
African horsesickness
theileriosis
Newcastle disease
Perhaps the most heartening result of the courses conducted so far has been the interaction of students, not only South African but also those from other African countries. In the future it is hoped also to accommodate students from developed countries where training in foreign animal diseases is inadequate or difficult. In this way we aim to promote awareness and competence in the control of serious epidemic animal diseases in the region while at the same time fostering international co-operation and understanding.
