Tanzania and the Peste des petits ruminants virus, or ‘PPRV’

Camilla Benfield

I’m a Lecturer in Virology at the Royal Veterinary College. I’ve been there for 5 years now and it’s a role in which I balance research and teaching. I always had a strong zoological interest and my realisation that vets could make broad impacts on global health was what drove me back from the Bedfordshire fields into a lab at Cambridge Vet School to do my PhD in molecular virology. There’s more on my career path in a Veterinary Record article ‘From herpetology to virology: how did that happen?’.

I am delighted to have been chosen as a 2018 Soulsby Fellow. The project which the Fellowship supports exemplifies several core One Health principles. The pathogen I’ll be working on is Peste des petits ruminants virus, or ‘PPRV’. This virus doesn’t infect humans, i.e. its not zoonotic. Zoonotic diseases are of course one very significant topic covered under the One Health umbrella. However, many non-zoonotic pathogens also have profound impacts on humans, and ecosystems, and PPRV is a prime example.

PPRV is sometimes termed ‘goat plague’. That name is a clue to PPRV’s siblings- it is closely genetically related to rinderpest virus, now eradicated, which caused ‘cattle plague’.

PPRV causes severe gastrointestinal and respiratory disease in sheep and goats. 90-100% of the flock may succumb and mortality rates can reach 50-100%. PPRV occurs in over 70 countries in Africa, Asia and the Middle East where it threatens 1.7 billion sheep and goats, 80% of the global population. PPRV’s range is increasing. Recent outbreaks in North Africa and the European part of Turkey increase the risk of PPRV crossing into mainland Europe.

Small ruminants are often reared by the poorest most marginalised communities. Therefore PPRV has a disproportionate effect on the income, livelihood and food security of the most vulnerable people. According to the Food and Agriculture Organisation of the UN (FAO), PPRV has a direct impact on over 300 million families and an estimated annual global cost of 1.5–2 billion US dollars. Therefore, FAO and OIE, the World Organisation for Animal Health, have pledged to eradicate PPRV globally by 2030 via mass vaccination of sheep and goats. This will be a pricey process; estimated at 996 million US dollars just for the first 5-year phase.

To realize the benefits of this massive investment, it is crucial that research is done to fill the gaps in our knowledge around PPRV. One such is the potential role of wildlife in maintaining and transmitting PPRV to livestock. My Soulsby Fellowship project will address this topic.

We know that various captive and free-ranging wildlife species can be infected by PPRV. In the greater Serengeti ecosystem, where I will be working, 64% of wildlife have antibody evidence of PPRV infection.

Interestingly, disease in free-ranging sub-Saharan wildlife has not been documented. Whether this represents tolerance/ resistance to PPRV or whether disease simply hasn’t be noticed, we don’t yet know. However, PPRV can have significant impacts on biodiversity. This was grimly exemplified by a recent PPRV outbreak in Mongolia. The saiga antelope is an icon of the Eurasian steppe, already critically endangered. In 2017, PPRV killed 60% of the saiga population.

For my project, I will travel to Tanzania to take samples for molecular detection and analysis of PPRV. Sensitive PCR-based methods and strategic sampling- as I will do- is key for assessing the capacity of wildlife to shed and transmit PPRV. Samples will be taken from wildlife captured for another project, minimizing interventions. The work will be done in partnership with SACIDS, the Southern African Centre for Infectious Disease Surveillance. Establishing collaborations with SACIDS scientists is another key aim of this project.

The second element is to visit a UK research group which specializes ‘PPRV pseudotypes’. More on these in a later post, but they are a powerful tool I will use investigate the molecular basis of wildlife’s susceptibility to PPRV.

I’ve explained in this first blog how PPRV impacts wildlife, livestock and humans. We must understand the epidemiology of PPRV in wildlife to enable the benefits of eradication for human and animal health and welfare. The generous support of The Soulsby Foundation will enable me to make a contribution towards this goal.

Camilla Benfield MA VetMB PhD MRCVS