By Nuru Ahmed
Despite several factors affecting diseases, climate change also contributes significantly to disease emergence.

“The survival, reproduction, abundance and distribution of pathogens, vectors and hosts can be influenced by climatic parameters affected by climate change,” a report by the United Nations Environment Programme (UNEP) and the International Livestock Research Institute (ILRI) said.

Climate change can particularly affect diseases transmitted by insects, ticks and other arthropod vectors, according to the report Preventing the Next Pandemic: Zoonotic disease and how to break the chain of transmission.

Warmer temperatures can increase the vector population size and distribution, along with the season duration when infectious vector species are present in the environment.

“Climate change can increase or decrease the incidence of the insect-transmitted Chagas disease, sand-fly transmitted leishmaniasis and other vector-borne and zoonotic diseases, generally with greater illness occurring at higher degrees of warming,” the report said.

Erratic weather events have an impact in the transmission of diseases as well. In 2010 in Africa, an outbreak of Rift Valley fever, a mosquito-borne zoonotic diseai, occurred with higher than average seasonal rainfall.

The report stated that emerging diseases in Brazil showed a relationship between infectious diseases outbreaks and extreme climate events such as El Niño, La Niña, heat waves, droughts, floods, increased temperature and higher rainfall, along with environmental changes such as habitat fragmentation, deforestation, urbanisation and wild meat consumption.

The frequency of extreme weather events can be affected by climate change, the report added.
The thawing of permafrost in the Arctic and sub-arctic region can significantly transforms soil structures, vegetation and habitats.

“Degradation of the permafrost can expose historic burial grounds, enabling the revival of deadly infections from the past. Rising temperatures increase the risk of zoonotic diseases in the vast Republic of Sakha (Yakutia), which makes up a fifth of Russia’s territories,” the report said.

It added that extended growing periods and expanded habitats are enabling more favourable living conditions for zoonotic pathogens and their vectors.

Bethan Purse, an Ecologist with the United Kingdom Centre for Ecology and Hydrology, an independent, not-for-profit research institute said, “Humans are changing zoonotic disease systems and increasing their impacts in many different inter-linked ways through habitat encroachment, human population pressure and settlement, intensive agriculture, forest loss and degradation, global trade, travel and climate change.”

He stressed on the need to understand how these changes bring people into closer contact with animals, arthropod vectors and pathogens and alter the dynamics of diseases.