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Nutrition, disease, biodiversity: do we need a new relationship with animals?

Zoonoses, diseases passing from animals to humans, have tripled in the last century

James Bowers, Chief editor at Polytechnique Insights
On December 15th, 2021 |
5 mins reading time
3
Zoonoses, diseases passing from animals to humans, have tripled in the last century
Thierry LeFrancois
Thierry Lefrançois
Director of Biological Systems Department at CIRAD
Key takeaways
  • The health crisis has sped up the “One Health” movement whose objective is to combine the study of human health, animal health and ecosystem health.
  • Today, 75% of infectious diseases affecting humans are of animal origin. These are called “zoonoses” and are due to microorganisms (viruses, bacteria, or parasites) capable of infecting both humans and animals.
  • Human activities such as deforestation, intensive farming and urbanisation bring domestic animals and wild animals closer to each other, which favours the emergence of zoonotic diseases.
  • New technologies capable of detecting the places and times where new epidemics are likely to appear are under development. These can help to identify circulating pathogens that could represent a pandemic threat.

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.

1https://​mood​-h2020​.eu/
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 
3https://​pre​zode​.org/​T​h​e​-​i​n​i​t​i​ative
4https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00265–8/fulltext