Science and Policy

Guest blog: Multi-disciplinary interactions under the Mexican sun – reflections from the ISVEE conference

Guest blog by Tiziana Lembo and Liliana Salvador with contributions from Rowland Kao and Louise Matthews.

What is the role of scientific conference? Is it to present our research and expound upon our scientific philosophies? Is it to hear people talking about the interesting research that they are developing? Or is it to meet old friends and make new ones while also traveling to interesting places? All of these aims and more were fulfilled when a group of us left umbrellas and raincoats behind to travel to sunny and warm Mérida, Mexico, for two stimulating weeks of ISVEE 14 (International Society for Veterinary Epidemiology and Economics) conference and workshops. The sun, heat, margaritas, “Jarana” tunes and dances, and the colourful decorations of the “Día de Muertos” created an ideal atmosphere for productive and enlightening scientific interactions.

Dia de muertos

The beginning of ISVEE 14 coincided with the “Dia de Muertos” (Day of the Dead), an ancient Mexican celebration to remember ancestors, family members and friends who have died. Traditionally, altars (“ofrendas”) are built that are laden with decorations, and favourite foods and beverages of teh departed. Above an altar dedicated to the famous Mexican painter Frida Kahlo de Rivera at La Casa Azul in Mexico City, where Frida Kahlo lived and worked most of her life (photo: Tiziana Lembo)

Every three years, ISVEE provides opportunities for academics from a range of different disciplines, policy-makers and stakeholders from the private sector to come together to share their expertise in innovative research, technological developments, and policy health agendas. By blending a wide range of disciplines to address health issues of global importance, the Boyd Orr Centre has a major role to play in all these discussions. What were our contributions to the ISVEE agenda this year?

 

Let’s start with our research on the very topical bovine Tuberculosis (bTB), caused by Mycobacterium bovis. Rowland Kao discussed a subject that is very close to his heart – the transformative role of Whole-Genome-Sequencing (WGS) in elucidating complex transmission dynamics and disease maintenance patterns in multi-host systems. He provided examples of how the approach has been used by the Glasgow team and collaborators to expose the role of wildlife in the maintenance and transmission of bTB to cattle in different parts of the world, including Great Britain, the United States, and New Zealand. He contrasted currently available data with optimal data and listed some of the key features of an ideal dataset for WGS approaches, most importantly dense, representative sampling across all important hosts; representative samples across populations, but also the way that evolutionary analyses and model-based epidemiological approaches complement each other in interpreting these data.

 

Joseph Crisp and Liliana Salvador provided examples of the use of WGS to tackle bTB in New Zealand and US wildlife and cattle populations. Joe showed that the evolutionary substitution rates of M. bovis in his study populations, including cattle, possums and other wildlife are higher than previously thought and that non-cattle reservoirs were heavily involved in the maintenance of M. bovis in the sampled population. Liliana focused on bTB transmission amongst elk, deer and cattle in Michigan, US, and demonstrated that elk is the only one of these species with spatial and temporal clustering of M. bovis. In addition, for the available data, she showed that there is no evidence of transmission between elk and cattle and that cross-species transmission in Michigan is likely due to deer.

 

Liliana also presented her work on surveillance of bTB in Low Risk Areas (LRAs) in England. She showed that larger herds and herds that receive a high number of animals from high-risk areas are most exposed to infection. She also demonstrated that in LRAs there is no clear advantage of testing herds for bTB more frequently, since it would give no increase in the number of detected breakdowns, but the number of false positive would rise considerably. However, adopting risk-based surveillance, where herds that are at higher risk of infection are targeted, can improve the efficiency of the testing regime by increasing the number of identified cases and reducing the number of herds tested.

 

An entire session of the conference was dedicated to foot-and-mouth disease (FMD) with a focus on the latest research efforts in Africa, Asia and Latin America. The work of the Boyd Orr Centre on endemic FMD in Tanzania featured prominently. Findings from micro-econometric studies investigating impacts of FMD outbreaks on individual livestock-owning communities were presented by Tom Marsh, a collaborator from Washington State University. These analyses have revealed that FMD outbreaks in cattle cause reductions in milk production, traction capacity and income from livestock sales, and that households would spend more on child education if they were not affected by milk losses due to FMD. Tiziana Lembo’s talk focused on epidemiological studies investigating temporal and spatial FMD virus dynamics in East Africa to devise appropriate control strategies. She showed that four different serotypes (A, O, SAT 1 and SAT 2) are responsible for FMD outbreaks in cattle in northern Tanzania, and that there is a pattern of serotypic dominance over time across Tanzania and Kenya, which allows us to predict the timing of epidemics of specific serotypes. The implications are that livestock vaccination could target given serotypes ahead of expected outbreaks, using monovalent vaccines, which are much more readily available than polyvalent vaccines needed to cover all of the wide range of serotypes circulating in these areas.

 

In her talk, Louise Matthews tackled the question of whether farmers would adopt a new diagnostic test for early detection of sheep scab at the subclinical stage. The advantages of using the test are that it would allow farmers to detect and treat the disease before clinical signs, reducing production losses, and also reducing transmission to other sheep and flocks. However, the farmers would need to pay for the test and may be reluctant to do so if they believe their flock to be at low risk of infection or if their neighbour is using the test, therefore not posing a transmission risk. These advantages and disadvantages can be assessed using a game theory framework that predicts whether farmers will adopt the test and how that uptake depends on test cost. The outcome was uptake of the test when farmers are at high risk (i.e. when they had experienced clinical sheep scab in the previous year), leading in the long term to a reduction in the proportion of infected farms by around 50%.

 

Harriet Auty, a collaborator from Scotland’s Rural College, presented research on human African trypanosomiasis caused by Trypanosoma brucei rhodesiense in Tanzania. She talked about the relative importance of different wildlife species in the reservoir community for human trypanosomiasis in multi-host populations of the Serengeti National Park. She showed that species such as bushbuck, reedbuck and impala, which are frequently infected with T. brucei, might play an important role in the reservoir community, even though they are not regular food sources for the tsetse vector. Conversely, elephant or giraffe are frequently fed on but rarely infected, indicating they may play a role in dampening transmission, and suggesting how changes in wild species composition could impact on human disease risk.

 

As always, ISVEE also provided a forum for conference delegates to update and strengthen their skills in a number of methods and topics through workshops run by academic colleagues from around the world. For instance, Tiziana Lembo benefited from training and discussions in data management and analyses in R organised by the Swedish National Veterinary Institute, as well as in the use of economics for animal health decision-making coordinated by the Royal Veterinary College and collaborators.

Back to the rain and grey skies now, we have many memories and knowledge to treasure from the land of revolution, music and art.

Zapata

Street mural depicting Emiliano Zapata in Tepoztlan, State of Morelos, Mexico during the Mexican Revolution. Zapata remains an iconic figure in Mexico to this day (Photo: Tiziana Lembo).

 

 

 

 

 

 

 

 

 

ode to life.png

An ode to life (“Viva la Vida”) by the Mexican painter Frida Kahlo de Rivera, La Casa Azul, Mexico City (Photo: Tiziana Lembo).

The research presented and our attendance were funded by: BBSRC / DFID / Scottish Government (Combating Infectious Diseases of Livestock for International Development initiative), MSD Animal Health, and Scottish Universities Life Sciences Alliance (Tiziana Lembo); BBSRC/DFID (Zoonoses in Emerging Livestock Systems) and EPIC (The Scottish Centre of Expertise in Animal Disease Outbreaks); Defra, NSF/BBSRC

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The irrationality of being rational.

http://marvel.com/universe/Blob

The Boyd Orr Blog is back! Hopefully with greater regularity than ever before.

Its now been over a year between posts, and it seemed like time to either put up (i.e. with my regular promises to self and other to restart the blog) or shut up – and those who were hoping for the latter, will be sorely disappointed! Many reasons for the hiatus, including the natural inertia that arises from not doing something regularly, through to the desire, as time between posts increases, to make the next one REALLY significant (a possible reason for some of the long-tailed distribution between correspondence times that has been observed in famous and ordinary people, through to realising that I was unsure about the direction that this blog should be taking – is it a personal view on science-related events, a blog meant to inform others, a blog to promote the Boyd Orr Centre, or … ? In the end I’ve decided that it perhaps doesn’t really matter too much, so long as there is some overall relevance to the scientific arena. After all, you as readers can quickly decide for yourselves if what is posted here is worth the time to read it. I would still encourage other Boyd Orr Centre members to contribute if you’ve the time – when I was blogging more regularly, there were a surprising number of views (though predictably, an awful lot of them seemed to be related to a post I did relating Star Wars Imperial Walkers to elephants).

And on to the post. Bovine TB has been in the news a lot over the last year, most recently because of a recent government strategy announcement. Badger culls have not only been continued, but rules for what is viewed as acceptable have also been relaxed. This has been supported by a seemingly innocuous statement that it is supported by the scientific evidence. Leaving aside any comment on the scientific debate itself, it is somewhat disturbing that such a blanket statement is made. Which scientists? And of course, such statements, in the face of the ongoing often vociferous debates going on in both the scientific community and in public, are a misrepresentation of the ongoing debate, refinement and synthesis that should be a defining process of science, and the scientific community itself.

Related to this, my group recently published a paper that looked at how evidence of disturbance of badger setts (from a cross-Northern Ireland survey) was related to incidence of farm breakdowns due to bovine TB. We found that (while somewhat less important than cattle herd related risk factors), a combination of sett disturbance and high badger sett density was a significant and important risk factor. In my view an interesting and useful finding, and one that broadly speaking is in line with studies in England showing that, while badger-related risk factors were important for starting outbreaks, cattle-related factors were primary factors in continuing them. It was also the subject of a rather intense peer review, which our lead author, David Wright, handled with impressive thoroughness (as he did with the entire paper – well done David). The paper received some media attention (including some good radio coverage on the Today Programme on BBC Radio 4 and on BBC Scotland) and there was also a fair bit of controversy over the use of the term ‘persecution’ to describe the unauthorised and illegal activities referred to in the paper. While in no way abrogating my responsibility as senior author for the content of the paper, I must admit that I was initially uncomfortable with this usage, however one of our co-authors insisted that this was, in fact, the standard term used for such activities, and it was on this basis that I was convinced. And indeed, it would in some ways seem to be a reasonable way to describe an activity that is both illegal and for which there is no evidence that it is even creating a positive outcome. And yet even while agreeing, I was well aware how emotive such a term really is (and perhaps, at least subconsciously, seeking out controversy). Insistence on being ‘right’ even when you are aware that it is likely to provoke a response that ends up obscuring the larger, more important debate (I don’t suppose you are reading, Richard Dawkins?) would appear to be a form of irrationality that is not exactly peculiar to scientists, but one which I suspect scientists are unusually susceptible to. Including, apparently, me.

Back to the badgers – the evidence base for bovine Tuberculosis control policies in England and Wales

Wildlife reservoirs for disease make control difficult.

Badgers are just one of many wildlife reservoirs for bovine Tuberculosis around the world.

So the badgers are back in the news, along with cats, of course. The Secretary of State for the Environment, Food and Rural Affairs, Owen Paterson, presented a government statement on strategy for eradication of bovine TB. In brief, his statement acknowledged the severity of the problem facing farmers, the rapid increase in the number of herds affected, the cost of the epidemic as well as the issues associated with any single control measure, none of which present a ‘magic bullet’ solution. As such, multiple measures are being pursued simultaneously, including cattle vaccination trials following EFSA recommendations that are scheduled to start in the near future, badger vaccination already being tested in the field, and programmes to enhance on-farm biosecurity. And of course badger culling.

Mr. Paterson’s statement pointed out that, in countries with a serious wildlife problem, reduction in cattle disease has followed from comprehensive approaches tackling the disease in both the wildlife reservoir and cattle, and indeed, it is likely that such an approach in England and Wales provides the best chance of achieving control. Proper consideration much also be given to the social, cultural and economic factors influencing the epidemic, including both the farming community and the wider public, and with a fuller appreciation of the ecological context of any single control measure, or suite of measures. An intriguing aspect of the problem is the role of legislation governing international trade that represents a considerable cost at the national level, was largely developed in the context of countries seeking eradication when human cases were a greater issue, but now many decades old. How this legislation will stand up in the face of increased evidence of wildlife problems across multiple EU nations including Spain and France and of tuberculosis caused by Mycobacterium caprae in Austria remains to be seen.

Consideration of bovine TB control in England and Wales must consider many inter-related factors

Consideration of bovine TB control in England and Wales must consider many inter-related factors

What makes the control of the problem particularly difficult in England and Wales is the now well accepted evidence that badger culling has the potential to result in both a positive and negative impact on cattle disease. To my knowledge, this makes it considerably different from known wildlife problems in other countries such as New Zealand or for that matter, in the Republic of Ireland, where no such perturbation problem has been observed. While well studied in the context of the randomised badger culling trial or RBCT, whether or not culling results in a positive or negate outcome is likely to be dependent in a complex and as yet poorly understood way on the underlying badger density, existing human interventions (illicit culling, sett disturbance, etc.), the as yet poorly quantified relationship between badger infection prevalence and cattle disease, and the impact of the disease in cattle on the badger population, and possibly other factors. These complex factors mean that any attempt to confidently extrapolate the results of the RBCT at a national scale are at best problematic.

So is there a solution? The statement by Mr. Paterson suggested control of bTB by 2038 would be viewed as success. In order to achieve even such a long term goal, continued investment in not just tackling the problem but understanding it is essential. Policy of course cannot wait for science to come up with definitive answers, but must be sufficiently nimble to respond when scientific evidence changes – the badgers may not have moved the goal posts, but not knowing where those posts are makes scoring that goal even more difficult.