Climate and emerging infectious diseases

Global climate change and varying uses of the land are related and can alter the geographic reach of certain infectious diseases. A group of Brazilian researchers is studying alterations in the epidemiological map of two emerging infectious diseases in the Western Amazon.

By Fábio de Castro

Agência FAPESP – Global climate change and varying uses of the land are related and can alter the geographic reach of certain infectious diseases. A group of Brazilian researchers is studying alterations in the epidemiological map of two emerging infectious diseases in the Western Amazon.

The objective is to develop an Early Warning System for Emerging Infectious Diseases, which will make it possible to adapt to the negative impacts of climate change on human health.

The Thematic Project, financed by the FAPESP Research Program on Global Climate Change, is coordinated by Manuel João Cesário, professor at Universidade de Franca.

The project monitors changes to the epidemiological map of Bartonellosis and Cutaneous Leishmaniasis in the tri-national frontier region between Brazil, Bolivia and Peru. The two diseases are transmitted by same vector: the Phlebotomus sand fly of the Lutzomyia genus.

Bartonellosis, a disease originating from the Andes, is caused by the Bartonella bacilliformis bacteria and causes weakness, anemia, fever and chills. The illness, also known as the “Peruvian wart” may present itself as “warty bartonellosis”, producing skin lesions resembling tumors.

Leishmaniasis, a zoonosis common to humans and dogs, is caused by protozoan parasites from the genus Leishmania and appears in both the visceral and cutaneous forms. The cutaneous form, also known as “Bauru ulcer” causes skin lesions and can also cause inflammatory lesions in nasal and oral mucous membranes.

“The objective of the study is to develop an early warning system for these diseases, given the severe socio-environmental changes that this region is experiencing. Aside from the impacts of global climate change and deforestation, there are impacts caused by deep social change brought on by development projects and heavy migrational flow in the region,” Cesário told Agência FAPESP.

Cutaneous Leishmaniasis, abundant in regions closest to the Brazilian seacoast, still hasn’t reached the region under study but is on its way west. In contrast, Bartonellosis is prevalent in Peru and theoretically exists neither in Brazil nor Bolivia, but is advancing eastward.

 “There was a significant increase in Bartonellosis between 2004 and 2005. It is believed that this was related to the El Niño phenomenon, which changes rainfall patterns and temperature in the region during some months of the year. This change could have some impact on vector reproduction and, with more flies, transmission is easier and the illness increases. However, it still isn’t clear whether the illness spread because the vectors moved or if new vectors appeared,” he explained.

Nevertheless, according to Cesário it is unlikely that the changes were caused by a single factor. One of the main goals of the project in coming years is to investigate which factors most influence the spread of the diseases to new regions.

 “The region we studied has undergone considerable socioeconomic change with the construction of the BR 364 and BR 317 highways and implantation of two hydroelectric plants that brought over 100,000 people to the state of Rondônia in the last three years. These last two huge projects caused the population of Porto Velho, which had 500,000 inhabitants, to increase by 20% over this period,” said Cesário.

Highway construction, on the other hand, affects vegetation according to the professor. “Studies show that 80% of all deforestation in the Amazon happens within 50 kilometers of a highway,” he pointed out.

Aside from the demographic explosion spurred by the infrastructure projects, Cesário says that the region’s vegetation has also suffered radical change directly influencing the regional climate, also affecting distribution of vectors of the illnesses.
 
“On the other hand, changes in climate also influence changes in vegetation because, for example, the forest becomes more susceptible to fire. It’s possible that all this directly affects the biology of the vectors. Because of this, at the same time that we investigate the causes of the changes, we also investigate their consequences,” affirmed the scientist.