University College London (UCL) researchers have developed a model to predict outbreaks of diseases that can be spread between animals and humans such as Zika and Ebola. The new method takes into account climate change, population growth, and land use.

Zoonotic diseases caused by viruses, parasites, fungi and bacteria, can be transmitted from animals to humans, and vice versa. According to the Centers for Disease Control and Prevention (CDC), 6 out of 10 infectious diseases in humans come from animals.

Kate Jones, Professor at UCL Genetics division, said the new model gives a significant step towards understanding how diseases are transmitted from animals to people. She hopes it could be used to prevent disease outbreaks among communities.

University College London researchers have developed a model to predict outbreaks of diseases that can be spread between animals and humans such as Zika and Ebola. Photo credit: ABC 7 Chicago
University College London researchers have developed a model to predict outbreaks of diseases that can be spread between animals and humans such as Zika and Ebola. Photo credit: ABC 7 Chicago

The model would also help governments to take action against environmental change, which could be triggering the development of an individual illness. While Zika and Ebola are heavily investigated, other zoonotic diseases are hard to control.

For instance, Rift Valley fever and Lassa fever are currently affecting thousands of people, although it can be prevented by altering some environmental elements, researchers said. Detailed results of the study were published Monday in Methods in Ecology and Evolution.

“Our model can help decision-makers assess the likely impact of any interventions or change in national or international government policies, such as the conversion of grasslands to agricultural lands, on zoonotic transmission,” Professor Jones said.

The presence of fever transmitted from rats may increase in Africa by 2070

According to Professor Jones, the model can understand how global change affects the development of various diseases at the same time.

“It aims to understand any trade-offs that decision-makers may have to be make,” he added in a press release issued Monday.

Researchers have used the new model to better understand the factors that interfere with the development of Lassa fever. The latter mostly occurs in West African countries such as Sierra Leone, Liberia, Guinea and Nigeria, said the CDC.

Lassa fever is transmitted by rats and causes symptoms which are usually mild such as fever, headache, and weakness. However, 20 percent of cases can develop hemorrhaging and even shock until death. It kills an estimated 5,000 people per year in Africa.

The team analyzed data from locations where 408 Lassa fever outbreaks took place in West Africa between 1967 and 2012. They considered the following factors: land use, temperature, rainfall, crop yields and access to health services.

The model determined that rates of people with the disease would increase from 195,125 to 406,725 cases. The primary cause of such an increment would be climate change and growing human population, said UCL researchers alongside partners in the Dynamic Drivers of Disease in Africa Consortium.

Researchers also made a map, to determine the location of the “multimammate rat Mastomys natalensis” against environmental elements. They added data from future population density, calculus of climate change and changes in soil caused by land-use.

How often are people likely to come into contact with disease-carrying animals?

The recently developed approach is capable of predicting the appearance of disease. It matches “changes in the host’s distribution” and environmental variations, with the implications that interfere in the spreading process, of a disease from an animal to a human.

Dr. David Redding, first author and fellow at UCL Genetics, emphasized that population increases and future climate change will have a significant impact of Lassa Fever over areas in West Africa. Especially in regions nearby Senegal and Guinea, and the coastline of Cote d’Ivoire and Ghana.

“The model allows us to calculate how often people are likely to come into contact with disease-carrying animals and their risk of the virus spilling over,” said Dr. David Redding on Monday.

Researchers said the new model could be enhanced, given that it achieved to calculate the future impact of Lassa Fever. For instance, they could add factors such as travel infrastructure, human-to-human contact rates, and poverty, to better understand how zoonotic disease are transmitted.

Governments should invest in research to prevent future outbreaks of zoonotic disease

Thousands of U.S. citizens are affected each year by zoonotic diseases transmitted by mosquitoes or ticks, such as Rocky Mountain, West Nile virus, dengue, malaria, and chikungunya.

However, other significant zoonotic disease such as Ebola and Zika have been present around the world over the last three years. The first has killed more than 11 thousand people in Guinea, Liberia, and Sierra Leone, while the second has been linked to the development of microcephaly in thousands of babies.

Jonathan Ball, professor at the University of Nottingham, told the BBC that future outbreaks of zoonotic disease will continue to be present. He remarked the importance of research, to prevent “diseases and their consequences.”

NASA researchers developed a similar model in April, to map which regions would be most affected by Zika disease during summer months in the United States. They considered temperature, rainfall and socioeconomic status, and numbers of mosquitoes.

Source: University College London Press Release