The 28th of September marked the 10th World Rabies Day, and this year’s theme was “Rabies; Educate. Vaccinate. Eliminate.” While most global efforts aimed at rabies control focus on spread by dogs and other carnivores, the Streicker lab working in the MRC-University of Glasgow Centre for Virus Research, and the Institute of Biodiversity, Animal Health and Comparative Medicine at the University of Glasgow, are looking at how the rabies virus is transmitted from blood feeding vampire bats in Latin America, which are the major source of rabies in this region, in a bid to establish more effective strategies to prevent rabies transmission, which will aid global efforts to eradicate the virus as a public health concern.
For the Contagious Thinking podcast, we spoke with University of Glasgow’s Dr Daniel Streicker – a Wellcome Trust fellow and 2015 National Geographic Emerging Explorer – and Dr Julio Benavides – a postdoc in Daniel’s lab and recent recipient of the George Baer Latin American Investigator Award from the international group, ‘Rabies in the Americas’.
The Bat Problem
Classical rabies is a very dangerous viral disease, which is nearly always fatal in humans and other mammals if symptoms show. Aside from a handful of cases contracted overseas, the UK – along with many countries across Western Europe – has been rabies free since the 1920s, through the use of widespread vaccination of dogs and other carnivores, such as foxes (although you can find a very closely related virus to rabies virus in British bats, it is extremely rare and does not cause as serious a disease). To find out more about how Europe is trying to keep its rabies free status, read this blog post from our sister IBACHM blog about how University of Glasgow researchers are helping this fight through the use of vaccine-loaded chicken heads. Yet across Asia and Latin America, rabies continues to be a huge problem for public health, and is responsible for the deaths of tens of thousands of people every year.
Here’s a video of Daniel and rabies from a few years ago:
A major host of rabies virus in Latin America is the common vampire bat, and for the last few decades routine culling programmes have been implemented by local authorities in an attempt to curb the spread of the disease. To learn more about vampire bats, watch this video narrated by Daniel on their biology and how they bite animals. Despite this, rabies remains a significant burden on the local health systems and the economy, as the bats can pass the lethal rabies infection to farm animals, such as cattle. Even the bites of the bats themselves are cause for concern for the farmers. One of the reasons that we are struggling to combat the virus is that we have a limited understanding of its basic biology and transmission in local vampire bats. In fact, it’s been shown that bat culling may actually increase the spread of rabies virus.
Tracking the wave
Our inability to control vampire bat rabies suggests that we are missing something. Through the use of viral and bat genetic data, serological investigations of bats, local public health data and questionnaires of local farmers (OA), the Streicker lab and collaborators have shown that vampire bat rabies virus in Peru is traveling in a predictable wave-like pattern across time and space, driven by the movement of male bats infected with the virus.
While the vampire bats are found all across Peru, not all the bats harbour rabies virus; the Pacific coast remains rabies-free, for now. However, rabies virus isn’t staying still in the bat populations – it’s moving, or emerging, into never-before seen territories (for rabies). This fact had not been appreciated by scientists or even local public health authorities but now this level of detail and understanding should allow for the forecasting of where and when rabies appear.
The Peruvian Andes have classically been viewed as a barrier to this movement, as their altitude reaches beyond a vampire bat’s physiological tolerance. However, valleys form natural routes across the Andes and the Streicker lab predicts that rabies could reach the pacific coast of Peru by June 2020. When here – aside from the serious implications it would have on human health and livestock – it could even potentially be transmitted to other wildlife, including local sea lions. Watch a video of a vampire bat feeding on a sea lion here.
The Streicker lab are now working with the Peruvian farmers and public health agencies to help to protect local populations and their livestock in regions ahead of the wave, by allowing the focusing intervention strategies. Vaccination of livestock is one option that farmers could do – if and when – a wave of rabies virus is predicted to reach a particular area. Another way to help may be in being able to test whether or not bat culling has a significant effect on preventing rabies, or whether a vaccine for bats could be useful.
Epidemiology of vampire bat rabies in Peru across time and space (taken from Benavides et al., 2016).
From rabies to Ebola
One implication following from the detailed study of rabies in vampire bats – and in bats of all kinds – is its use as a model to understand virus cross-species transmission in general. No other animal is probably associated more with cross-species transmission of viruses and viral emergence than bats. Bats have been implicated in the spread of many other viral pathogens – excluding rabies – to humans and our livestock, such as the filoviruses, Marburg virus (and probably Ebola virus), the paramyxoviruses Nipah virus and Hendra virus and of course SARS coronavirus.
Daniel’s work in studying the transmission of rabies virus between bat species aims to provide a tractable model system to study how – and why – viruses jump from one species to another, a process known as ‘zoonosis’. What are the barriers to species jumps? What are they? Are they viral or are they host?
Whether or not vampire bat rabies may act as a model for further scientific study, rabies remains a significant global health problem despite a safe and effective vaccine. This is in part due to the complex nature of its geographic spread and ecology, and our limited understanding of it, especially in areas like Latin America.
Through the close study of rabies virus in vampire bats in Peru, the Streicker lab provides the world with a fascinating and ever-clearer picture of rabies transmission, epidemiology and evolution, all with a very tangible real-world benefit that could help save the lives of thousands of individuals across Latin America. Now, it is a case of watchful waiting to see how Peru deals with the impending wave of rabies that is crashing through the Andes, and heading for the Pacific Ocean.
By Josie Bellhouse and Dr Connor Bamford (@cggbamford)
Daniel and Julio wish to extend their thanks to those not mentioned directly in this podcast, unfortunately due to time constraints. They mentioned their collaborators – especially those in Peru; local governments who helped facilitate their work as well as colleagues in Latin America and those back here in Glasgow who helped carry out the research and who inspired them to do such important science; and of course those who helped to mentor them throughout their training.
For more information on Daniel and Julio’s work described here, check out these other articles: NPR; NSF; University of Georgia; University of Glasgow and the Glasgow Insight into Science and Technology (GIST) magazine, by Michaela Maya local Phd student and science communicator. You can follow Daniel on twitter here @danielstreicker .
The CVR and IBACHM at the University of Glasgow conduct research into many areas of rabies, viral epidemiology and emergence, from evolutionary, population and cellular backgrounds. Groups include those of Roman Biek, Sarah Cleaveland, Katie Hampson, Daniel Haydon, the CVR’s arbovirus group and emerging viruses programme.