Concerted and coordinated action can bring success in the field and enhance food security, says John Anderson.
Rinderpest was one of the most devastating virus diseases of livestock known to man. Closely related to measles in humans, rinderpest (from the German ‘cattle plague’) has probably been around since before the birth of Christ and devastated European powers in the 17th century.
With a mortality rate of up to 90%, major epidemics in the late 1890s killed over 80% of African cattle and other wildlife in southern Africa. Along the Horn of Africa, an estimated one-third of the population of Ethiopia and two-thirds of the Maasai people of Tanzania died of starvation.
In the 1980s the virus struck again, killing an estimated 100M animals from Senegal to Somalia in Africa and from Turkey to Bangladesh in Asia. Economic losses totalled US$2Bn in Nigeria alone.
Following the development of a live attenuated vaccine by British virologist Walter Plowright in 1962, early eradication efforts in the 1960s and 70s eventually stalled, but showed the war might be winnable.
As the UN’s Food and Agriculture Organisation (FAO) mobilised a new eradication campaign, the Global Rinderpest Eradication Programme, (GREP) in the 1990s, The Institute for Animal Health (IAH), Pirbright, UK, was designated the FAO World Reference Laboratory for rinderpest in 1994 and thereafter provided a global diagnostic service for all countries involved in the programme. This included rinderpest diagnosis, molecular characterisation, the provision of training and technical backup, and the production and quality control of diagnostic kits and research to further our understanding of rinderpest virus biology.
What lessons have been learned along the way?
The main factors in the success of GREP, from an IAH perspective, were the development of the right technology for field use in Africa and Asia, successful transfer of that technology along with technical backup, and the provision of standardised diagnostic kits that everyone could use.
The Plowright vaccine induces life-long immunity after a single vaccination, but only if the vaccine is maintained at the correct temperature before administration. The vaccine virus is rapidly inactivated at temperatures greater than 4C and so involved the strict use of a cold-chain. Seromonitoring was therefore essential to monitor the performance of the vaccination teams and to establish levels of herd immunity.
However, at the start of the Pan African Rinderpest Campaign and subsequently GREP, most laboratories were unable to carry out the virus neutralisation test to see if it had worked and mass testing was impossible.
To tackle this problem, IAH developed an indirect ELISA test (enzyme-linked immunosorbent assay) and underwent two-year field trials in Tanzania to make sure it worked under tough local conditions.
The test performed well and was later replaced with an improved test (a monoclonal antibody-based competitive ELISA) which gave greater specificity (>99.5%), sensitivity and reproducibility. It also greatly reduced the number of false-positive results which saved unwarranted and expensive field investigations. Furthermore, the use of this single test harmonised results and increased participants’ confidence when communicating during regional workshops.
Rapid diagnosis and detection was essential during the latter stages of the eradication programme. The development of a rapid pen-side test proved invaluable in countries such as Pakistan and Somalia and empowered the field veterinarians to take prompt action to stamp out the last remaining pockets of infection.
The Rinderpest Laboratory Network established by the Joint Division FAO-International Atomic Energy Authority with the assistance of IAH Pirbright proved the ideal vehicle for technology transfer.
Annual co-ordination meetings were always linked to training courses and updates in diagnostic techniques, software programs or epidemiological strategies.
The success of this process is highlighted by the fact that the project holders are now regarded as experts in their own right and have assisted many other countries in establishing similar technology.
The provision of standardised quality controlled reagents played a major part in the eradication programme, and large batches of antigen and control sera were produced to minimise test variation between laboratories.
This was further enhanced by the use of a monoclonal antibody-based assay, and a single batch of monoclonal antibody was used for all the competitive ELISA kits produced.
External quality assurance panels showed a 98% agreement between laboratories in Africa; a much higher figure than that reported for HIV testing at that time.
Recommendations for the future
The strategy used for rinderpest eradication, although not applicable to all diseases, could be used as a blueprint for other diseases such as peste des petits ruminants (meaning ‘disease of small ruminants’, known as PPR virus).
Key factors for success include the availability of an excellent vaccine (which we have), secure long-term funding, the establishment of a Secretariat in FAO Rome as a global co-ordination unit, and evolution of the OIE Pathway to Freedom from Rinderpest guidelines which gave clear advice to all countries at each stage of the process.
However, let it not be forgotten that the drive and determination of a few key people was also essential to this remarkable success.
This story highlights the importance of continued support for applied, problem-driven research in agriculture and food security.
Addressing significant animal health problems through appropriate research and development – allied to excellent technology transfer and empowerment of local scientists – has played a key role in this major achievement.
About John Anderson
John Anderson joined the Institute for Animal Health (then the Animal Virus Research Institute) in 1968 as a technician in the World Reference Laboratory (WRL) for foot-and-mouth disease (FMD) before being seconded to Nairobi, Kenya, in 1971 to work on FMD carrier status in local cattle and the role of wildlife in FMD epidemiology.
He returned to IAH Pirbright in 1977 and worked on FMD, rinderpest and bluetongue viruses and was designated Head of the WRL for rinderpest in 1994 where he developed the indirect and competitive ELISAs and pen-side test for rinderpest which were used throughout the Global Rinderpest Eradication Programme.
He was in charge of the serological testing during the 2001 FMD outbreak in the UK and was awarded the MBE for Services to Animal Health in 2003. In 2006, he was appointed Acting Head of IAH’s Pirbright Laboratory until his retirement in 2008.