Five zoonotic diseases you need to know about
It’s estimated that there are 150 zoonotic diseases in the world , and each year, they sicken over two billion people. Because they’re transmitted from animal to human their movement across the globe poses a significant and at times, devastating risk to human health.
The impact of Ebola in recent years has served as a powerful reminder that we can only secure human health if we can keep animal health under control by adopting a ‘One Health’ approach.
We focus on five of some of the most important zoonotic diseases in the world right now and what is being done to limit their impact.
1. Rift Valley Fever
Despite the first cases of the Rift Valley Fever (RVF) being first reported in 1930, it was the epidemic in 1997 that made headlines when it infected 90,000 people in East Africa in just three months . And just last month (June 2018) , the first significant outbreak of RVF was reported in East Africa for more than a decade.
Mosquitoes carry the disease, making it difficult to control because infected mosquito eggs can survive for years in the soil. The infection is then transmitted to humans through the blood, tissue or organs of livestock infected with the virus through mosquito bites.
The majority of human infections result from direct or indirect contact with the blood or organs of infected animals
But research has found that RVF outbreaks correlate with years of unusually heavy rainfall because it provides the perfect environment for the eggs to hatch. This has enabled scientists to use satellite images to monitor changes in sea temperatures which impact rainfall.
Although there is no vaccination against RVF in humans, vaccinating livestock is an effective way to control the disease. The International Livestock Research Institute (ILRI) is working with key stakeholders in East Africa to create a proactive vaccination framework.
Probably the most well-known zoonotic disease in the world, rabies was originally discovered in the 1600s. The fatal disease has been feared for centuries. The symptoms are painful and the disease is 100% fatal if left untreated.
It is usually passed to humans from dogs in saliva or other bodily fluids through a bite or scratch, although many domestic or wild animals can carry the disease.
Despite the availability of an inexpensive and effective animal vaccine, rabies is responsible for over 55,000 deaths every year — most of which occur in Africa and Asia.
But there are many big projects targeting 2030 for the eradication of human rabies from dogs using One Health approaches. One example is in Guinea, where global health agencies, including the Global Alliance for Rabies Control, are working to implement a canine vaccination program. And in Ethiopia new One Health initiatives are being adopted to better control the disease.
It is thought this disease could be as old as the Bible. Many scholars believe that in the story of Moses, the fifth plague may actually be describing anthrax, which causes sickness in livestock.
Animals contract the illness through inhaling or ingesting spores in contaminated soil, plants or water. The disease is then transmitted from animals to humans via direct contact with spores, inhalation of spores or ingestion of contaminated food or water.
Anthrax can be controlled by animal vaccination but, unfortunately, the disease is still one of the most common zoonotic diseases found across the globe .
In areas where the disease is endemic, such as in East Africa, the FAO (Food and Agriculture Organization of the United Nations) is working with stakeholders to encourage local veterinary and health services to improve tracking and prevention.
Human brucellosis cases reach as many as 500,000 each year . The disease is mainly transmitted to humans through undercooked meat or raw dairy products, although it is possible to become infected by handling an infected animal too.
According to the Global Alliance for Livestock Veterinary Medicines (GalvMed), the annual impact of Brucellosis on smallholder farms across Sub-Saharan Africa and South Asia is estimated at $501 million per year.
Although a vaccination exists, it is not effective against strains in many developing countries. As a catalyst, in 2016 GalvMed launched a competition to find a vaccination with a $30m prize. Find out how the competition has been received in our interview.
5. Middle East Respiratory Syndrome
Known as MERS, Middle East Respiratory Syndrome is a relatively new disease. The first case was reported in Saudi Arabia in 2012 and although a connection with camels has been established, the original source of the pathogen is still unknown.
Since the first reported cases there have been over 2000 cases and 722 deaths from the infection, with travel-related cases reported in Europe and the US.
But the world is attempting to tackle the disease – 130 experts gathered in Geneva last year to understand how they can control the pathogen. Meanwhile, funding has recently been awarded to the University of Saskatchewan in Canada to develop a vaccine for the disease.
The eradication of Rinderpest and Smallpox has demonstrated that we can stamp out zoonotic disease. But eradicating all zoonotic disease will be impossible. Only by implementing a collaborative One Health approach across human and animal health will we be able to control zoonoses effectively.
Find out how disease surveillance is helping to forecast where the next outbreak might happen.