RVC has been engaged on research involving a viral pathogen causing peste des petits ruminants or goat plague for many years and over the last 7, Prof Richard Kock, Dr Bryony Jones and Dr Camilla Benfield have been exploring the complexity of PPR epidemiology in both Africa and Central Asia. This has required more of a focus on untypical hosts for the virus, given its emergence and spread into novel habitats and exposure of naïve populations and species, in addition to examining the transition from epidemic to endemic status in domestic small ruminant populations in newly infected regions. This work is aimed at supporting the strategies developed and developing for eradication of the virus globally.
The GCRF funded partnership in East Africa was started in 2017 and has completed all its field work, with laboratory studies near completion. This involved participatory epidemiology in the endemically infected areas of the Greater Serengeti Ecosystem of Kenya and Tanzania and wildlife research. Preliminary results confirm the wide circulation of the virus amongst small ruminants but with relatively low mortality in the endemic setting, nevertheless of concern, given losses in small stock are evident and vaccination programmes, as far as they have been applied, apparently ineffective. Wildlife disease in the region, if it exists, is cryptic and hard to find as no confirmed case has been found, although evidence from serology suggests widespread infection across the buffalo, antelope and wild pig (warthog) populations.
In Central Asia infection in wildlife is expressed and serious epidemics have resulted in mass mortality of some species such as critically endangered saiga antelope. In the process of this work it has been increasingly clear that the standard tests are not fit for purpose, at least for use amongst the untypical hosts and there may be weaknesses, also, in their use in domestic stock in natural settings. Only one readily available commercial competition ELISA is available for antibody detection as the other was withdrawn from the Market and a new ELISA is still relatively untested in the field. For eradication, serology is vital and the tests must be specific and sensitive to ensure the process can verify freedom from infection in all countries. Test accuracy is also important with cryptic disease, as in the African wildlife, to better understand their role and importance to the persistence of PPR.
The GRTA is a translational award following on from the GCRF PPR project with some new partners at Glasgow and IAEA. This project has been set up with the specific purpose of examining a number of new tests that have been developed for PPR serology, using novel methods, including pseudotype tests and Luminescence assays to address some of the issues arising from the earlier work. The latter two tests may well be equivalent to the gold standard virus neutralisation, which is largely unused due to its high cost and impracticability in many settings. In order to establish a more reliable screening, probably still based on ELISA, we need to validate these tests across a widely diverse spectrum of untypical host species serum. This will be a core activity of this project.
The GRTA partnership includes the main reference laboratories of Pirbright, CIRAD and IAEA Vienna and research groups in Glasgow (Virology) and RVC (PPS VEEPH) with close liaison with the PPR Global Eradication Programme (GEP) and research network (GREN), which is focused on this validation task and most importantly, in supporting the establishment of a regional research hub for PPR and diagnostics in Southern African Centre for Infectious Diseases, Morogoro Tanzania, based at the Sokoini University of Agriculture (SUA), East Africa. The latter, a key outcome of the GCRF overseas development principle. The partnership continues to work closely with the Director of Veterinary Services and wildlife authorities, the Kenya Wildlife Service and Tanzania Wildlife Research Institute in this project.