What are zoonotic diseases?
Zoonotic diseases, also known as zoonoses, are diseases which are transmitted to humans from animals. They present a significant challenge to the public health of today and the future. Up to 60% of known human infectious diseases are of animal origin. A recent joint report by ILRI and UNEP states that 75% of new or emerging infectious diseases are zoonotic. The virus that has caused the COVID-19 pandemic is one example and current scientific evidence is compelling enough to indicate that the virus started in an animal host. The recent Ebola epidemics have also been linked to people becoming infected through contact with infected wild animals. One of the oldest pandemics in history, the “Black death” of 1350, was also of animal origin. According to the US-Centre for Disease Control (CDC), zoonotic diseases cause up to 2.5 billion cases of human disease and 2.7 million deaths globally, with resource-limited countries bearing the highest-burden. With these statistics, there is no doubt that accurate and timely diagnosis is critical.
Tuberculosis (TB) and its zoonotic potential
TB is one disease that has devastated humanity and among the three significant leading causes of mortality from an infectious disease. You may not be aware that a proportion of TB cases reported globally are of animal origin! Zoonotic tuberculosis (zTB) is acquired by consuming contaminated animal products and closely associated with extrapulmonary tuberculosis in humans. As a neglected re-emerging infectious disease, the exact proportion of zoonotic tuberculosis globally is unknown. The last estimates provided by WHO in 2016 indicate cases are high in resource-limited countries in Africa and Asia, though it is highly likely that cases are underreported because of the lack of availability of diagnostics for zTB and coordinated surveillance. It’s also possible that some countries may be reluctant to set up systems for zoonoses surveillance due to negative implications for international trade.
The role of animal health laboratories
Animal health laboratories are much like defenders in a game of football. In football, the defender provides the first line of defense against all attacks. Whatever the defender manages to block never goes to the keeper. The keeper can watch his defenders and has time to prepare in case the opponent’s strikers penetrate through the line of defense. Anything the defenders miss lands to the keeper, and in the worst-case scenario, the opponent scores. Animal health laboratories play an essential role in safeguarding human health by acting as the first line of defense against infectious diseases of animal origin. This is an important, yet often neglected mechanism for global public health security. Several studies have demonstrated that there is a very close correlation between the burden of zoonotic diseases in animals and humans. What this tells us, is if we can detect these emerging zoonotic infectious diseases in our animal health laboratories, we will be one step further in our quest to manage the incidence of these infectious diseases in humans. If shared with human health stakeholders and health providers, the information generated by these animal health laboratories can inform strategies for surveillance in humans and provision of appropriate countermeasures well in advance before cases increase and blow up to pandemic proportions. In the case of the COVID-19 pandemic, it’s only recently that scientific evidence has irrefutably implicated an animal to be the source of the virus. If this virus had been detected early, measures to counter its spread could have been put in place and millions of deaths could have been prevented.