By Adama Diouf Ly (APS)
Dakar, March 31 (APS) – Climate change, at the same time as it contributes to degrading the environment, is a factor in the resurgence of certain diseases, including dengue fever, Rift Valley fever or fever Zika, as researchers and scientists now attest.
The scientific world and medicine consider as already obvious the link between certain diseases – malaria, respiratory diseases and waterborne diseases – and climatic phenomena characterized by a rise in temperatures, air pollution and flooding.
The resurgence of certain diseases such as dengue fever, Rift Valley fever or Zika fever disease adds to this picture of the links to be established between the evolution of meteorological conditions and their impact on human health.
According to the Global Strategy on Health, Environment and Climate Change, a draft submitted to the 68th session of the Regional Committee for Africa of the World Health Organization (WHO), held in Dakar in August 2018, ‘ ‘Climate change is having an increasing impact on people’s health and well-being, as are other global environmental changes such as the loss of biodiversity’.
This phenomenon ”increases the frequency of heat waves, droughts, extreme rains, violent storms and cyclones in many regions and alters the transmission of infectious diseases, which has important implications for health”, notes the committee.
Changing weather patterns have effects on sea level rise, which increases the risk of flooding, making the consequences of climate change global in effect and scale.
In Senegal, for example, the extreme climatic conditions are not unrelated to the dengue fever epidemic which affected certain regions of the country a few weeks ago.
A clearly established link
Worse, it is feared that global warming will continue to create favorable conditions for the development of dengue fever vectors, but also Rift Valley fever, chikungunya and Zika fever disease.
Until then, there was “a lack of relevant and concordant observations” on climate variability, linked to the emergence and re-emergence of certain diseases, but now the link between climate change and certain epidemiological factors is clearly established, argues Massamba Sylla, professor of medical entomology at the University of Sine-Saloum El Hadj-Ibrahima-Niass, in Senegal.
This link is attested to by several works on borreliosis, a common condition caused by a bacterium transmitted to humans by bites from hard ticks and long confused in Senegal with bouts of malaria, said this researcher.
Similarly, the work carried out on Crimean-Congo hemorrhagic fever and Rift Valley fever are a good illustration of the emergence of diseases linked to climate change, notes Massamba Sylla.
He notes on this subject that the emergence in Senegal, in the 1980s, of Rift Valley fever, of an epidemic type, was linked to the drought and the massive influx of small ruminants from the west and southeast of Mauritania in Rosso, on the Senegal River watershed, in an area where the pathology has never been reported before.
Floods, a major variable
Floods are at the same time a major variable in the appearance of vector-borne diseases such as malaria, dengue fever and bilharzias, which can all be linked to the rainfall process and floods.
With the recurrence of floods for several years in Senegal, there has been a resurgence of dengue fever epidemics in the urban area of Dakar, but also in Touba, Fatick, Rosso, Ziguinchor, in localities facing a sanitation deficit. above all, the mosquito favoring the development of dengue can live in stagnant sewage for a long time.
Cholera, in particular, seems to have the most obvious link with the floods in Senegal, with vibrio cholera, the pathogen responsible for this disease, having appeared every time there has been flooding, such as in 2003 , 2009, 2012, 2015 and 2019.
There are generally fears to be had and a set of diseases with epidemic potential to be monitored, in relation to climate variability.
These diseases can be linked to specific climatic parameters such as rain and relative humidity, not to mention that Senegal is under the threat of pathologies linked to heat wave phenomena, according to researchers.
Temperatures can equal or exceed 45°C between March and June in northern Senegal, the regions of Saint-Louis and Matam, as well as in the region of Tambacounda, in the east of the country.
The impact of current climate change on human health was integrated by researchers from the beginning of the 1990s, recalls Massamba Sylla, who gave the example of the Intergovernmental Panel on Climate Change, established in 1988 to provide detailed assessments of the state of scientific, technical and socio-economic knowledge on climate change, its causes, potential impacts and response strategies.
Analysis of research on infectious diseases transmitted by vectors (mosquitoes and ticks) has shown that temperature variability and noted changes in the intensity and distribution of precipitation have a definite effect on the distribution of vectors and , consequently, on the areas of incidence of many viral, bacterial and parasitic diseases.
Human action may certainly have favored the proliferation of the vectors of these diseases, but there are also “probably factors linked to the climate, in particular temperature, humidity and precipitation”, explains the environmentalist Ibrahim Sy, researcher at Cheikh-Anta-Diop University in Dakar.
Mr. Sy is of the opinion that “we cannot rule out the possibility of a link between the appearance of certain diseases with high heat, floods, air pollution, the most frequent manifestations climate change or climate change, depending on the name”.
Towards an increase in climate-sensitive diseases
”These are conditions that exist in tropical Africa, and this is one of the reasons why today we have an increasingly important development of certain vectors such as the Aedes mosquito, in particular the species known as Aedes aegypti, vector of dengue fever in Senegal,” said Ibrahima Sy.
”We also believe that change, and especially global warming, will continue in the years to come to create favorable conditions for the development of these vectors which cause dengue fever, but also yellow fever, chikungunya and the disease Zika fever,” he added.
According to him, the projections of several scientists relate to the fact that climate-sensitive diseases “will increase by 2030-2050”.
These are mainly malaria, which is mainly present in the southern regions of Senegal, but also dengue fever which is likely to appear more often around Thiès, Touba and Dakar, not to mention Rift Valley fever in Louga and in the Senegal River Valley, cholera in areas like Touba and Dakar.
With regard to diseases linked to heat waves, they should mainly concern the northern and western zones, ”with an associated mortality, much higher in the western zone, in September, October and November, with a feeling of heat much more high,” says the environmentalist.
“The relative humidity will increase, the oceans will warm and [engendrent des conséquences] on the continent, and that’s where there will be many more health risks linked to heat waves,” explained Ibrahim Sy, collaborator of the Dakar Ecological Monitoring Center.
Climatic variables linked to flooding will be increasingly taken into account by the scientific world, including ”rain [qui] is a major variable in the appearance of vector-borne diseases such as malaria, dengue, intestinal schistosomiasis”, continues the environmentalist.
”It is the relative humidity that is put forward, sometimes it is a problem of development or planning, since globally, we notice that it is in the zones where the rainfall is more abundant that we find a certain dynamism of the anopheline mosquito responsible for malaria”, points out Ibrahim Sy.
Conversely, Rift Valley fever is a disease that appears in areas where there is not much water, such as the Ferlo. Ponds can thus constitute favorable places for the reproduction of Aedes, the vector of this disease.
Water and soil contamination
Finally, there is the case of waterborne diseases linked to water stagnation such as diarrheal diseases, in particular cholera, dermatoses and intestinal parasites, also linked to climate change.
The researcher informs that in this case, ”the problem is water pollution”, since with the floods and the absence of a proven mechanism for managing this phenomenon, ”surface water and the tablecloth may be contaminated”.
With floods, the risk of emergence of these diseases increases, the most determining factor being water contamination and soil contamination with helminthiasis, which cause intestinal schistosomiasis.
Ibrahim Sy also asserts that for agricultural products, it is impossible to achieve “traceability” of production conditions (type of water, fertilizer and phytosanitary treatment).
”It’s a whole chain that we don’t always control, and it’s the final actor, namely the consumer, who must take steps to clean thoroughly before use,” he said. advised.