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“Disease transmission from animals to humans has tripled over the last century”

Thierry LeFrancois
Thierry Lefrançois
Director of Biological Systems Department at CIRAD

With the effect of Covid-19 being felt around the globe, it would seem now is as good a time as any to focus on pre­ven­tion of future pan­demics. A vast num­ber of emerg­ing infec­tious dis­eases in humans are of ani­mal ori­gin and, as such, the One Health approach has been thrust into the spotlight. 

In Novem­ber 2020, the One Health High-Lev­el Expert Pan­el Frame­work was announced at the Paris Peace Forum with the goal of inte­grat­ing human, ani­mal, and envi­ron­men­tal health sys­tems into one. Sym­bol­ic of this shift in think­ing from a human-cen­tred to all-encom­pass­ing approach, Thier­ry Lefrançois (Cirad) is the first vet­eri­nar­i­an to join the French Covid-19 sci­en­tif­ic advi­so­ry board. 

With the con­cept of One Health, it is hoped that researchers can iden­ti­fy emerg­ing dis­eases that could trans­fer from ani­mals to humans as ear­ly as pos­si­ble. Why is the focus on envi­ron­men­tal issues so important? 

Three-quar­ters of infec­tious dis­eases in humans are of an ani­mal ori­gin because some micro-organ­isms (virus­es, bac­te­ria, or par­a­sites) or par­a­sites, that can infect cer­tain ani­mals and also humans. The asso­ci­at­ed dis­eases, called zoonoses, include Ebo­la of which bats are sus­pect­ed hosts, avian influen­za in domes­tic and wild birds, Rabies in dogs or, of course, SARS-CoV­‑2 (Covid-19); even though we expect it to have orig­i­nat­ed in bats, we do not know which species allowed the trans­fer to humans (pan­glion, mink etc.). Zoonoses occur via a range of process­es that are large­ly affect­ed by the prox­im­i­ty between dif­fer­ent species and there­fore by the environment

It should be said that this infor­ma­tion is not new: the sci­en­tif­ic com­mu­ni­ty has warned of the dan­ger of zoonoses for years. Between 1940 and 2000, trans­mis­sion of dis­ease from ani­mals to humans has more than tripled. The rea­sons for such are quite sim­ple: virus­es spread much more eas­i­ly between ani­mals that are raised in dense, some­time unsan­i­tary, con­di­tions such as those in inten­sive farm­ing prac­tis­es – as the spread of the Covid-19 pan­dem­ic to Mink farms attests! On top of that, destruc­tion of habi­tats via defor­esta­tion or replac­ing nat­ur­al zones with agri­cul­tur­al or urban instal­la­tions push­es live­stock, domes­tic ani­mals, and humans clos­er to wild ani­mals, favour­ing the spread of dis­ease between species. Hence, the risk of infec­tious dis­eases is large­ly affect­ed by ecosys­tems, cli­mate fac­tors, agri­cul­tur­al prac­tices, and a range of oth­er socio-eco­nom­ic factors. 

We are see­ing devel­op­ment of new tech­nolo­gies that can help us detect where and when new epi­demics may be happening.

How close are we to being able to pre­dict future pandemics? 

It is extreme­ly dif­fi­cult to pre­dict which zoonoses [ani­mal-human dis­eases] will trans­fer from one species to anoth­er and, in the past, there has been lit­tle suc­cess in doing so. Rather, we are see­ing devel­op­ment of new tech­nolo­gies that can help us detect where and when new epi­demics may be hap­pen­ing by pin­point­ing where the spread of dis­ease is becom­ing prob­lem­at­ic. As such, we can antic­i­pate which pathogens already in cir­cu­la­tion are like­ly to become pandemic. 

In the Euro­pean project, MOOD1, which CIRAD is coor­di­nat­ing, we are study­ing how we can use arti­fi­cial intel­li­gence to detect epi­demics as ear­ly as pos­si­ble. The AI analy­ses tex­tu­al data avail­able on the Inter­net – from social media posts, for exam­ple – as opposed to look­ing at tra­di­tion­al epi­demi­o­log­i­cal data, which require bio­log­i­cal sam­ples and test­ing. Analy­sis of infor­ma­tion in this way can offer insights very ear­ly on in an epi­dem­ic. We can seek out rel­a­tive­ly infor­mal terms like “swine flu” or “fever”, for instance, and com­pare their occur­rences to iden­ti­fy where there may be clus­ters appearing.

More­over, we can car­ry out “syn­dromic sur­veil­lance” by using Google search­es for key­words or trends in phar­ma­ceu­ti­cal sales. ­Hence, the goal here is not com­plete­ly around pre­ven­tion, instead it is more about detect­ing emerg­ing pan­demics as ear­ly as pos­si­ble by tap­ping into the huge amount of infor­ma­tion already avail­able online. Exper­i­ments were done using this tech­nol­o­gy to study the arrival of bird flu, with pos­i­tive results show­ing that – had this type of approach been avail­able – it could have helped us act quicker.

Even though antic­i­pa­tion is key, are there still things that we can do in terms of prevention? 

Yes. And, actu­al­ly, pre­ven­tion is high­ly impor­tant because it involves look­ing into socio-cul­tur­al sys­tems in a way that will allow us to avoid emer­gences and pre­vent cir­cu­la­tion of pathogens in ani­mals before they can be trans­mit­ted to humans. We are keep­ing close tabs on a num­ber of dis­eases around the world includ­ing the African Swine Flu, rabies or Nipah (an infec­tion found in bats in South-East Asia). Stud­ies show that efforts are like­ly to pay­off: invest­ment in pre­ven­tion costs 100 times less than a future pan­dem­ic2

To do this, there isn’t much point in tar­get­ing spe­cif­ic ani­mals because trans­mis­sion varies depend­ing on the species. Rather, we need to find a way of pre­vent­ing fac­tors that favour trans­mis­sion, which tend to be loca­tion depen­dent. As such we have iden­ti­fied high-risk zones where we are focus­ing much atten­tion from Mex­i­co to Zim­bab­we to Viet­nam. In an ide­al world, we would be able to take bio­di­ver­si­ty into account in human urban and agri­cul­tur­al devel­op­ment. If we are expand­ing a town or city, then could we cre­ate path­ways for nature to move through? Will there be domes­tic ani­mals or live­stock? Will it be zone of inten­sive farm­ing? Answer­ing these ques­tions can help analyse the risks and con­sid­er envi­ron­men­tal health with that of ani­mals and humans. 

The con­cept of One Health has become an inter­na­tion­al col­lab­o­ra­tion. What kind of the coop­er­a­tion are we see­ing happen?

Gen­er­al­ly, States have been reliant on sep­a­rate insti­tu­tions to deal with health, envi­ron­ment and agri­cul­ture. But with One Health, we pro­pose an inte­grat­ed approach on the very high­est lev­el. In mid-April 2021, the call for experts closed and the select­ed inter­na­tion­al coun­cil will bring ~20 inter­na­tion­al experts togeth­er in May this year to work togeth­er and pro­vide mul­ti­dis­ci­pli­nary exper­tise to inter­na­tion­al organ­i­sa­tions involved in One health issues (WHO, OIE, FAO, UNEP). 

How­ev­er, top-lev­el coop­er­a­tion is not where our atten­tion is need­ed most. One Health needs to be tak­en seri­ous­ly by the state, yes, but we need work in the field too. To iden­ti­fy the right indi­ca­tors we should be study­ing, we need to keep a close eye on what’s hap­pen­ing on the ground. That isn’t only the job of researchers; it involves farm­ers, nation­al parks, civ­il ser­vices and so forth. 

Hence, we need things to hap­pen on the ter­ri­to­r­i­al scale: “think glob­al, act local.” For exam­ple, there is a shift in focus from pro­tect­ed zones in the form of nat­ur­al parks to “land shar­ing”. The lat­ter takes into account the fact that nature doesn’t recog­nise the bound­ary between a nation­al park and a human-occu­pied zone. Instead, the two need to be merged so that bio­di­ver­si­ty can be main­tained intelligently. 

At the One Plan­et Sum­mit in France on the 11th Jan­u­ary 2021, Pres­i­dent Macron announced the Pre­zode Project, with the aim “to reduce the risk of emer­gence and ensure the rel­e­vance of sur­veil­lance and ear­ly detec­tion sys­tems at the local, region­al and glob­al lev­els 3,4.” This is a very ambi­tious inter­na­tion­al ini­tia­tive, polit­i­cal­ly sup­port­ed at the high­est lev­el in France and will be finan­cial­ly sup­port­ed by French Min­istry of research, Min­istry of Europe and for­eign affairs. Also, in the future by many more coun­tries and foun­da­tions and organ­i­sa­tions around the world; we are mov­ing things for­ward with over 1,000 sci­en­tists involved from 50 countries.

Interview by James Bowers
2Smith KF, Gold­berg M, Rosen­thal S, Carl­son L, Chen J, Chen C, Ramachan­dran S., 2014, Glob­al rise in human infec­tious dis­ease out- breaks. J. R. Soc. Inter­face 11: 20140950. http://​dx​.doi​.org/​1​0​.​1​0​9​8​/​r​s​i​f​.​2​0​1​4​.0950 


Thierry LeFrancois

Thierry Lefrançois

Director of Biological Systems Department at CIRAD

Thierry Lefrançois has worked at CIRAD on the diagnosis, epidemiology and control of tropical infectious animal diseases in Burkina Faso, Kenya and Guadeloupe. His research activities have focused on disease emergence and the development of interactions between research and surveillance in the framework of regional health networks in the South. He currently heads the Biological Systems Department (BIOS) at CIRAD, which groups together research units working on animal health, plant health, plant adaptations and biodiversity, and promotes an integrated and interdisciplinary approach to health within the framework of the "One Health" concept. He is currently a member of the Covid scientific advisory board in France.