An ecosystems view on PPRV, from Rome… Camilla Benfield reports

Delegates at the first expert meeting on PPRV at the livestock-wildlife interface, held at FAO Headquarters
Acknowledgement ©FAO/Giuseppe Carotenuto

The FAO (Food and Agriculture Organisation of the UN), whose mandate is to build a world without hunger, has set PPRV high on its agenda. Eradicating PPRV will help achieve the Sustainable Development Goals, particularly SDG1, to end poverty and SDG2, to end hunger. Removing the scourge of goat plague will enhance resilience of communities and empower women, who in many cultures are in charge of small ruminant farming.

Eradicating PPRV will also help realise another SDG, Life on Land (SDG 15). This was a key message at an expert meeting I attended at FAO Headquarters in Rome, funded by my Soulsby Fellowship. This was the first FAO meeting on PPRV at the livestock-wildlife interface. Why do wildlife need a place at the UN’s table? First, because we now have stark evidence for the impact of PPRV on biodiversity. Second, if we hope to eradicate PPRV from the globe, and use resources wisely to this end, our strategy must take into account the virus’s broad range of host species, both wild and domestic.

Rome is the site of the FAO Headquarters, whose Animal Production and Health Division helps to combat transboundary animal diseases

Thus, our recommendation from the first meeting ‘Controlling PPRV at the livestock-wildlife interface’ is that wildlife be explicitly integrated into the implementation of the PPR Global Eradication Program (GEP), the next GEP Phase being 2022-2027. 

One issue that came to the fore at the meeting was the lack of validated serological diagnostic tests for detecting PPRV infections in wildlife. Different species immune systems will ‘see’ PPRV differently and mount different immune responses. A test (ELISA for example) that detects anti-PPRV antibodies from a sheep cannot be assumed to work equivalently to detect anti-PPRV antibodies made by an infected antelope. There is a gap- which hopefully our research will soon fill – in understanding the relative performance of the various different tests in the various different host species. We badly need this information. For basic questions on PPRV epidemiology, but also for very applied reasons in support of the eradication campaign. The current PPRV vaccine does not enable discrimination of vaccinated from infected livestock. However, testing unvaccinated wild species to determine antibody presence can indicate if PPRV is still circulating in an area. Thus wildlife can act as ‘sentinels’ in the later stages of the vaccination campaign. But only if we apply the correct diagnostic tests!

New technologies can help us here, and at the meeting I presented on one of them- ‘PPRV pseudotypes’. My Soulsby Fellowship funded a trip to Glasgow University earlier in the year, where I learnt how to make and use these. PPRV pseudotypes are hybrid virus-like particles with surface proteins from PPRV, but their ‘innards’ from another virus. They enter cells (using their PPRV-derived proteins) but they can’t replicate i.e. make offspring. They are not an actual virus. However, they are a very useful tool for serological testing for PPRV: if a blood sample contains antibodies against PPRV, these antibodies will latch onto the PPRV proteins on the pseudotyped particle and ‘neutralise’ it i.e. prevent it from entering cells. Pseudotypes don’t require the high biosecurity containment facilities needed to handle PPR virus. They also don’t employ species-specific reagents (such as secondary antibodies used in many ELISA kits). In a recent grant application, we have proposed a multi-centre collaborative grant, with the Sokoine University of Agriculture, my Soulsby Fellowship host in Tanzania, as a key partner. Its aim is to provide recommendations for researchers and policy-makers on how to reliably test for PPRV across the range of wild and domestic species that this virus infects, in order to help research to combat PPRV and achieve eradication. It’s critical we lay the research and scientific foundations now – and are honest about our knowledge gaps – in order to support the huge logistical, practical and political task of PPRV eradication. The Rome FAO meeting and amendments to the PPR GEP are a very positive move in acknowledging the need for an ecosystemic ‘One health’ view on PPR that includes wildlife in the PPRV equation we are all trying to solve.