As the world observes World Zoonoses Day, it’s important to remember that human health is intimately tied to the health of animals, wild and domesticated. 

Five years after Covid-19, the world remains alert to health threats that can cross over from animals to people. 

Alongside growing concerns over high-profile spillovers like avian influenza, the silent threat of everyday zoonoses – from salmonella in poultry to leptospirosis in livestock – continues to affect hundreds of millions each year. These infections may not all make front-page news, but their impact on human health is significant and largely preventable. 

Furthermore, these zoonotic diseases are on the rise. Virus jumps from animals to humans are increasing around five per cent annually, meaning these pathogens are forecasted to cause four times the number of spillover events in 2050 than in 2020.

Given the interconnectedness of human and animal health, the best way to prevent zoonotic disease in people is to stop it from spreading in animals. However, we are currently falling short in this task as the threat of zoonoses appears to be increasing. 

Despite the recent adoption of the world’s first pandemic agreement at the May World Health Assembly, which explicitly recognized the need for integrated approaches known as “One Health”, gaps remain in veterinary infrastructure worldwide. This leaves the door open to another devastating cross-species outbreak. 

To address this, the world must strengthen the veterinary sector, from improved use of animal vaccines and other medicines to increased training and services. Importantly, recruiting and empowering veterinarians on the frontline is a practical and cost-effective way to reduce these risks and protect public health. 

Overall, zoonotic disease incidence represents 60 per cent of infectious diseases in humans. Common zoonotic diseases, such as salmonella, can originate in unprotected animals. Thankfully, these types of risks can be controlled through veterinary tools, but only if they are available.

Meanwhile, just 13 zoonoses are responsible for 2.4 billion cases of human illness and 2.2 million deaths per year. For example, more than a million people globally are affected each year by leptospirosis, a dangerous and sometimes deadly disease caused by bacteria that transfers from animals to humans.

According to a new report from the World Organisation for Animal Health (WOAH), cases of avian flu in mammals doubled last year compared to 2023, for instance. In the EU, zoonotic diseases have been found to be on the rise. 

WHO pandemic agreement missed animal health reference – despite high human costs of spillovers

Despite opportunities to agree on and implement preventative measures, they have not been sufficient to address the risk at hand. The World Health Assembly recently adopted the first pandemic agreement, yet the agreement is missing any mention of veterinary medicine and animal health. Without this inclusion, the agreement can never fully fulfil its aim to prevent pandemics.

Disruptions from zoonotic disease outbreaks carry a significant cost to the global economy. The estimated direct cost of the loss of life due to zoonotic diseases is $212 billion annually, not including the costs associated with long-term treatment or ulterior damages. 

Conversely, the estimated cost of preventative measures, including monitoring and surveillance of risks as well as landscape management, is around $20 billion. In other words, preventing these diseases is more than ten times cheaper than dealing with the consequences.

Protecting food security and farmers’ livelihoods, especially in developing countries, is another reason to take a proactive approach to preventing zoonoses. When livestock contract a disease, farmers often must cull their flock or herd to prevent further spread of the illness. This impacts food availability and prices and creates massive losses for farmers. While difficult to calculate, the estimated loss of animals due to disease varies from 20 per cent globally to 50 per cent in developing countries. Furthermore, the burden of zoonotic disease falls heavily on low- to middle-income countries, where health infrastructure is limited and communities rely heavily on livestock.

Countries must invest in veterinarians and proactive disease control strategies

To build more resilience to zoonotic disease outbreaks, there are fundamental actions that must be undertaken. First, countries must invest in their veterinary workforces, training, and infrastructure. Investing in this field allows for well-resourced, trained, and capable veterinary services that can effectively address threats and protect animal health before an outbreak occurs. In the UK, for instance, a new initiative offers farmers subsidised veterinary visits for multiple herds or flocks to help prevent disease.

It must also adopt proactive, rather than reactive, disease control strategies. Improving proactive strategies such as monitoring, detection, and vaccination can prevent or at least minimize the impacts of an outbreak. 

Furthermore, we must enhance public-private partnerships. Taking advantage of the speed at which the private sector can develop urgently needed technologies, such as vaccines, diagnostics and treatments, alongside the expertise of veterinarians and reach of public institutions, can ensure more effective measures against zoonoses.

With diseases like avian flu on the rise and everyday threats like salmonella continuing to impact public health, the world must adopt a coordinated approach to avoid zoonotic outbreaks. The losses caused by animal disease outbreaks are compounded by an order of magnitude when they spread to people. Improving animal health is the best way to protect the health of all.

Carel du Marchie Sarvaas is the executive director of HealthforAnimals, the global animal health association representing manufacturers of veterinary pharmaceuticals, vaccines and other animal health products.  He is a Dutch national and holds degrees from the University of Leiden and Johns Hopkins University.

John de Jong is the president of the World Veterinary Association, and a small animal practitioner in Boston, MA. He is also a former board member of the American Veterinary Medical Association serving as Chair (2015-2016) and as President (2018-2019).

Image Credits: FAO, BMJ, November 2023, ILRI/FLICKR, Sebastien Assoignons/ Wildlife Conservation Society, International Federation of Red Cross and Red Crescent Societies / The Kenya Red Cross Society.