Air & Water Borne Diseases
Open Access

Zoonosis; Zoonotic diseases; One Health; Interdisciplinary; Spillover events; Transmission pathways; Ecological factors; Epidemiology; Surveillance; Mitigation strategies; Public health; Wildlife trade; Land-use change; Climate change; Global health security

Introduction

Zoonosis, derived from the Greek words "zoo" (animal) and "nosos" (ailment), refers to diseases and infections that can be transmitted from animals to humans, also known as zoonotic diseases or zoonoses [1]. These diseases have been an integral part of human history, shaping societies and cultures across the globe. From the bubonic plague to COVID-19, zoonotic diseases have left indelible marks on human civilization, often causing significant morbidity, mortality, and socioeconomic disruptions [2]. Zoonoses, diseases transmitted from animals to humans, have been an integral part of human history since the dawn of civilization [3]. From ancient times to the modern era, the interplay between humans and animals has facilitated the transmission of various pathogens, leading to outbreaks, epidemics, and pandemics with significant implications for public health, economies, and ecosystems worldwide [4]. The term "zoonosis" itself underscores the interconnectedness of human and animal health, highlighting the intricate web of interactions that shape the dynamics of infectious diseases.

The origins of zoonotic diseases can be traced back to the earliest domestication of animals, when humans began living in close proximity to livestock, creating opportunities for pathogens to cross species barriers [5]. Over millennia, agricultural practices, trade routes, urbanization, and globalization have further intensified this interaction, facilitating the spread of zoonoses across geographic boundaries and between diverse populations. Zoonoses encompass a broad spectrum of pathogens, including bacteria, viruses, parasites, and fungi, each with unique characteristics influencing their transmission dynamics, clinical manifestations, and control measures [6]. Examples range from well-known diseases such as rabies, influenza, and tuberculosis to emerging threats like Ebola virus disease, Zika virus infection, and COVID-19 [7]. The emergence and re-emergence of zoonotic diseases are influenced by a myriad of factors, including ecological changes, land-use patterns, climate variability, human behavior, and socioeconomic drivers. Deforestation, habitat destruction, wildlife trade, intensive livestock farming, and urbanization can disrupt ecosystems, alter wildlife populations, and bring humans into closer contact with potential reservoirs of pathogens, increasing the risk of spillover events.

In addition to their immediate health impacts, zoonoses also pose long-term threats to global health security, necessitating a holistic One Health approach that recognizes the interconnectedness of human, animal, and environmental health [8]. By addressing the root causes of zoonotic disease emergence, promoting interdisciplinary collaboration, and strengthening surveillance and response capabilities, One Health initiatives aim to prevent, detect, and mitigate the impact of zoonoses at the human-animal-environment interface [9].

As the world continues to confront emerging infectious disease threats, understanding the complex dynamics of zoonotic transmission is paramount for effective preparedness and response [10]. By elucidating the ecological, social, and biological factors driving zoonotic spillover events, researchers, policymakers, and healthcare professionals can develop evidence-based interventions to safeguard human and animal health while promoting sustainable coexistence in an increasingly interconnected world.

Historical perspectives

The relationship between humans and animals has been a double-edged sword throughout history. While animals have provided companionship, food, labor, and various other benefits to humans, they have also been the source of numerous infectious diseases. The domestication of animals, a crucial milestone in human history, facilitated the transmission of pathogens between species. The close proximity and interactions between humans and domesticated animals created ideal conditions for the emergence and spread of zoonoses.

One of the most infamous examples of a zoonotic disease is the Black Death, which ravaged Europe in the 14th century, claiming millions of lives. The causative agent, Yersinia pestis, primarily infects rodents such as rats and is transmitted to humans through flea bites. Another notable zoonotic disease is influenza, which has a long history of interspecies transmission. The 1918 influenza pandemic, often referred to as the Spanish flu, is estimated to have killed between 50 to 100 million people worldwide. The virus responsible for the pandemic, H1N1 influenza a virus is believed to have originated from avian sources.

Mechanisms of transmission

Zoonotic diseases can be transmitted to humans through various routes, including direct contact with infected animals, consumption of contaminated food or water, inhalation of infectious aerosols, and bites from infected vectors such as mosquitoes, ticks, and fleas. The transmission dynamics of zoonoses are influenced by factors such as the pathogen's biology, host specificity, environmental conditions, and human behavior.

Some zoonotic pathogens can directly infect humans without the need for an intermediate host. For example, rabies virus, transmitted through the saliva of infected animals, can cause fatal encephalitis in humans following a bite from a rabid animal. In contrast, other zoonotic diseases require an intermediate host to complete their life cycle. Lyme disease, caused by the bacterium Borrelia burgdorferi, is transmitted to humans through the bite of infected black-legged ticks, which acquire the pathogen by feeding on small mammals such as mice and squirrels.

Emerging zoonotic diseases

The emergence of new zoonotic diseases poses significant challenges to public health and global stability. Factors contributing to the emergence of zoonoses include encroachment into wildlife habitats, deforestation, urbanization, climate change, globalization, and agricultural practices such as intensive farming and wildlife trade. These activities can disrupt ecosystems, alter host-pathogen dynamics, and facilitate the spillover of pathogens from animals to humans.

The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, highlights the profound impact of emerging zoonotic diseases on human health and society. The exact origins of SARS-CoV-2 are still under investigation, but it is believed to have originated in bats and transmitted to humans through an intermediate host, possibly a wild animal sold at a seafood market in Wuhan, China. The rapid spread of the virus globally underscores the interconnectedness of our modern world and the importance of proactive surveillance, early detection, and coordinated responses to emerging infectious threats.

One health approach

Addressing the complex challenges posed by zoonotic diseases requires a multidisciplinary approach that recognizes the interconnectedness of human, animal, and environmental health. The One Health approach emphasizes collaboration among various sectors, including public health, veterinary medicine, environmental science, wildlife conservation, agriculture, and policy-making, to promote holistic solutions to zoonoses and related issues.

Key components of the One Health approach include surveillance and early warning systems for detecting emerging threats, research on the ecology and transmission dynamics of zoonotic pathogens, vaccination and other preventive measures in both human and animal populations, improved hygiene and biosecurity practices, sustainable land use and wildlife management strategies, and enhanced communication and collaboration between stakeholders at the local, national, and global levels.

Conclusion

Zoonotic diseases represent a significant and evolving public health challenge with profound implications for human well-being, economic stability, and ecological integrity. Understanding the dynamics of disease transmission between animals and humans is essential for mitigating the risks associated with zoonoses and preventing future pandemics. By adopting a One Health approach and embracing interdisciplinary collaboration, we can work towards a healthier and more resilient future for both humans and animals. Zoonoses, the diseases transmitted from animals to humans, present a complex and ever-evolving challenge to public health, environmental conservation, and socioeconomic stability worldwide. The interconnectedness of ecosystems, human-animal interactions, and globalization has facilitated the spread of zoonotic diseases with unprecedented speed and scale. As evidenced by historical pandemics like the Black Death, Spanish flu, and, more recently, HIV/AIDS, SARS, MERS, and COVID-19, zoonoses have the potential to cause catastrophic human suffering, disrupt economies, and strain healthcare systems.

As we confront the ongoing threat of zoonosess, it is imperative to acknowledge the intrinsic link between human, animal, and environmental health. By embracing a One Health approach that recognizes the interconnectedness of these domains, we can foster a more sustainable and resilient future for both people and planet. Through concerted efforts and collective action, we can strive towards as world where zoonotic diseases no longer pose a significant threat to public health, and where humans and animals coexist in harmony, safeguarding the well-being of present and future generations.

1. Yagupsky P, Peled N, Riesenberg K, Banai M (2000)Exposure of hospital personnel to Brucella melitensis and occurrence of laboratory-acquired disease in an endemic area. Scand J Infect Dis 32: 31-35.

Indexed at, Google Scholar, Crossref

2. Baldwin CL, Parent M (2002) Fundamentals of host immune response against Brucella abortus: what the mouse model hasrevealed about control of infection. Veterinary Microbiology 90: 367-382.

Indexed at, Google Scholar, Crossref

3. Ko J, Splitter GA (2003) Molecular host-pathogen interaction in brucellosis: current understanding and future approaches to vaccine development for mice and humans. Clinical Microbiology Reviews 16: 65-78.

Indexed at, Google Scholar, Crossref

4. Yagupsky P, Peled N, Press J, Abu-Rashid M, Abramson O (1997)Rapid detection of Brucella melitensis from blood cultures by a commercial system. Eur J Clin Microbiol Infect Dis 16: 605-607.

Indexed at, Google Scholar, Crossref

5. Shasha B, Lang R, Rubinstein E (1992) Therapy of experimental murine brucellosis with streptomycin, cotrimoxazole, ciprofloxacin, ofloxacin, pefloxacin, doxycycline, and rifampin. Antimicrobial Agents and Chemotherapy 36: 973-976.

Indexed at, Google Scholar, Crossref

6. Prior S, Gander B, Irache J M, Gamazo C (2005) Gentamicin loaded microspheres for treatment of experimental Brucella abortus infection in mice. Journal of Antimicrobial Chemotherapy 55: 1032-1036.

Indexed at, Google Scholar, Crossref

7. Izadjoo MJ, Mense MG, Bhattacharjee AK, Hadfield TL, Crawford RM, et al. (2008) A study on the use of male animal models for developing a live vaccine for brucellosis. Transboundary and Emerging Diseases 55: 145-151.

Indexed at, Google Scholar , Crossref

8. Shemesh AA, Yagupsky P (2011)Limitations of the standard agglutination test for detecting patients with Brucella melitensis bacteremia. Vector Borne Zoonotic Dis 11: 1599-1601.

Indexed at, Google Scholar, Crossref

9. McFarlane PA, Bayoumi AM (2004) Acceptance and rejection: cost-effectiveness and the working nephrologist. Kidney International 66: 1735-1741.

Indexed at, Google Scholar, Crossref

10. Okosun KO, Rachid O, Marcus N (2013) Optimal control strategies and cost-effectiveness analysis of a malaria model. Bio Systems 111: 83-101.

Indexed at, Google Scholar, Crossref