How to manage zoonotic diseases early and save global health

Alice Kiyong'a, a research associate and biologist

Alice Kiyong'a, a research associate and biologist, analyses serum drawn from a camel's blood for the Middle East Respiratory Syndrome (MERS) virus at the International Livestock Research Institute (ILRI) laboratories, where scientists monitor for indications of possible transition of the microbes from animal to humans, in Nairobi on March 24, 2021.

Photo credit: AFP

Around three-quarters of emerging infectious diseases that affect people in low-income countries have their origins in wild and domestic animals.

It is estimated that 60 per cent of known infectious diseases in humans and about 75 per cent of all emerging infectious diseases are zoonotic – meaning that they are spread from animals to humans. For instance Ebola, Covid-19, the Zika virus and bird flu are all considered zoonoses, meaning they jumped from animals to people.

According to a 2022 report by the International Livestock Research Institute (ILRI), just 13 of the 200 known zoonotic diseases cause 2.2 million deaths a year, mostly in developing nations. 

The report titled “Preventing the next pandemic: Zoonotic diseases and how to break the chain of transmission” indicates that there is a need to fully understand the transmission of these infections, the threats they pose to human health and how to minimise the risk of more devastating outbreaks. 

To this end, a livestock-inclusive “One Health” agenda would go a long way in helping protect the whole world against pandemic diseases. 

“Investments in healthier and sustainable livestock systems would benefit the three interconnected areas of ‘One Health’ — animal, human and environment, and reduce the risk of disease spillovers,” says ILRI.

“It’s impossible to overstate the importance of livestock in countries across Africa, Asia and Latin America. Everything from food, and nutrition to gender equality, livelihoods and trade depends on farm animals,” said Jimmy Smith, director-general at ILRI.

“Healthy livestock means healthy people and environments, which not only enable low-income countries to sustainably grow their economies, but also to improve global health security, minimising the risk of disease outbreaks that spread worldwide.”

The playbook highlights the importance of improving the early detection of emerging zoonotic infections in animals both to protect the livelihoods of the poorest and to prevent pandemics. One such disease is the Middle East Respiratory Syndrome Coronavirus (MERS-CoV), a virus that is transmitted by camels, which is becoming increasingly popular in countries such as Kenya due to its climate resilience.

“As the World Health Organisation progresses a new pandemic preparedness treaty, it is critical that governments seize the opportunity to invest in livestock systems to improve public health. Tackling zoonotic diseases at source would dramatically reduce the number of human illnesses and deaths while saving trillions of dollars in future epidemic or pandemic control,” said Hung Nguyen-Viet, co-leader of the Animal and Human Health Programme at ILRI.

The emergence of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) at the end of 2019 and the vast global public health and economic impacts predicted consequences of how people source food, trade animals and alter environments. 

One Health approach

To manage emerging infectious diseases (EIDs), including zoonoses, and reduce the risk of them becoming epidemics and pandemics, there is a need to understand their origins, their various types and importance in different communities, and their drivers.

One Health is an integrated, unifying approach that aims to sustainably balance and optimise the health of people, animals and ecosystems.

To protect human health, the ILRI report has highlighted some practical ways to improve livestock systems and unlock benefits for global health and development while reducing pandemic outbreaks. These include:

1. Investing in vaccines and diagnostics to prevent disease transmission between animals and humans
Wider use of livestock vaccines, which obviates the need for antibiotic treatments to cure livestock diseases, limits the development of antimicrobial resistance in pathogens, thereby protecting humans as well as animals.

2. Investing in early detection of emerging zoonotic diseases, including Monkeypox and Covid-19 
Emerging zoonotic diseases can be detected in wildlife and controlled within livestock populations before they jump to humans and become pandemics, thus saving the global economy trillions of dollars.

3. Investing in understanding what drives the spread of livestock-mediated endemic diseases
The enormous health risk to animals and people alike is significantly reduced, thus reducing human illnesses and deaths and saving trillions of dollars by controlling zoonoses.

4. Investing in systems that control soil-transmitted infections
Intestinal worms (hookworms, whipworms, roundworms) that are transmitted to humans through soil contaminated by eggs or larvae of parasites are controlled and the number of children nutritionally and physically impaired by these infections are greatly reduced.

5. Investing in rational and fair use of antibiotics and other antimicrobials in livestock farming
The spread of antimicrobial resistance in pathogens is curbed, thus protecting the health and lives of millions of people and animals by prolonging the use of effective antibiotics and other antimicrobial drugs.

6. Investing in the control of pathogens that cause foodborne diseases
The use of livestock vaccines and other livestock disease control methods reduces the presence of foodborne pathogens in livestock and thereby reduces people’s risk of consuming contaminated foods.

7. Investing in food safety in markets
Focusing on informal markets, which benefit the poor, represents a shift from food safety investments that have focused in the past on formal and export markets, where safer food mainly reduces health risks for richer people.

8. Investing in evaluating how much greenhouse gases are produced by small livestock farms
The climate benefits and hazards of livestock-keeping are reliably accounted for, enabling countries to incentivise livestock keepers to minimise their livestock greenhouse gas emissions while also enabling them to reap rewards for capturing carbon in their soils.

9. Investing in smarter feeding that uses local forages, crop waste and other feedstuffs that is inedible to humans
Better livestock feeds raise livestock production yields of farmers while reducing the greenhouse gas ‘intensity’ of their cattle, sheep and goats (less gas is emitted per unit of milk or meat produced). New cultivars of so-called ‘all-purpose crops’ such as sweet sorghum yield food for people (via grains), feed for ruminants (via stover) and feed for soils (via nitrogen). 
Making use of cassava peels for livestock feed nourishes farm animals while reducing environmental waste.

10. Investing in farming systems which grow crops as well as raise animals
Mixed crop-and-livestock farms become ‘regenerative’ as well as profitable, with nutrients and other resources recycled, waste minimised and wildlife habitats and biodiversity protected.

11. Investing in making both human and animal health services available in pastoralist areas
Hard-to-reach pastoralist communities are now included in healthcare models. Mobile healthcare options targeting both humans and animals increase the uptake of health services in both sectors.

12. Investing in vaccines against neglected livestock diseases can reduce antibiotic use
Thermotolerant vaccines against ‘goat plague’ (peste des petits ruminants) and other neglected diseases protect livelihoods in marginalised communities. Broader use of vaccines would reduce community use of antibiotics thus contributing to the prevention of antimicrobial resistance.

13. Investing in compost and biodigest animal and human waste for fertiliser and biogas
Animal and human excreta are managed for healthier people, animals and environments in developing countries, where the reuse and recycling of waste for agriculture is important and where sanitation systems are often deficient; the resultant waste is used to fertilise soils or is turned into biogas, saving resources (including firewood) and reducing microbial contamination and thus risks to public health.

14. Investing in information and services for livestock keepers 
Care-giving farmers improve animal welfare, increase household incomes, improve human nutrition and reduce transmission of zoonotic diseases from livestock to humans. Women are encouraged and empowered to become leaders and drivers of One Health by enhancing the health of their families, the care of their animal stock (including rational use of antimicrobial drugs) and the stewardship of their environments.