In my last post I referred to a report from WHO and WMO, ATLAS OF HEALTH AND
CLIMATE, where are mentioned a number of diseases that would be affected in
one way or another by climate change, among them Malaria.
Malaria (probably meaning “bad air” as it was
thought to be produces by air from marshy areas) is an illness caused by
parasites transmitted to humans by specific mosquitoes. There are about 3,500
species of mosquitoes (grouped in 41 genera) (CDC) but it is
the female of
genus Anopheles which causes the main malarial problem. Malaria is mainly
present in tropical and subtropical countries, infecting over 300 million
people per year and causing the death of more than 1 million in the same period
(MedLinePlus). By
the way Anopheles means “useless,
hurtful, harmful”
This kind of transmission is denominated vector-borne
disease (VBD), i.e. the infectious disease is transmitted to human from another
human or from an animal through a living entity (WHO)
From now on I will introduce Notes in my blog, they are trying to aim you, the
reader, to check about certain points that seems interesting to me but are not
in line with the main course of this blog.
Note
1: if we consider the countries
between the tropics we would have about 40% of the total world population
and the same percentage of the world´s surface, it would mean that making some
very basic numbers the portion of the people infected by malaria between the
tropics would be approximately over 10% of the population of the region.
Recent research by Murdoch el al. shows that
global warming could reduce the effect of malaria in some regions. They explain
that some studies have shown the potential increase of the illness in cooler
countries due to the increase in temperature. However, they show that this
change, in the warm countries, would reduce the capacity of some of the vectors
(the type mosquito carrying the parasite that produces the illness) to act as
such and of the parasite itself due to distancing of the optimal temperature
conditions. This is very interesting; in case this is proven to be realistic, it
would mean that global warming would change the current health/diseases map of
the world.
Note
2: Did you know that Europe is the first region in the world to be
declared malaria free? WHO
says so.
But let´s go back to malaria and climate change, other
publications from a number of scientist from Europe and USA of 2015 (Perham et al.) expresses “While this is likely to take many forms (they refer to climate change), the implications for future transmission
of vector-borne diseases (VBDs), given their ongoing contribution to global
disease burden, are both extremely important and highly uncertain” i.e. the
problem is so complex that so far any estimation is very uncertain, meaning
they can take any path in the future. For me this is even more dangerous than
having a clear consequence as in this last case it is clear what steps need to be
followed to overcome the problem and the real possibility of accomplish these
steps. The article mentions a series of challenges/variables/aspects
to consider when trying to understand the effect of climate change in VBDs
(vector-borne diseases), among them:
1.
Socio-economic and socio-cultural aspects
2.
Selecting the appropriate way of measuring the
illness
3.
Data availability
4.
Appropriate models
5.
Ecological aspects
So we have two investigations, one saying that global
warming would reduce malaria in a part of the world and the other saying it is
extremely hard to know the real effect.
Not being this confusing enough there is another study
published in 2014 (Carminade
et al.) in it the authors running a series of computational models found
that changes in global temperature will favour the transmission of malaria in
the tropics but they understand that there are other variables to take into
account in future investigations.
If we go deeper in the methodology used by Murdoch et al., we can see
they worked under laboratory condition isolating mosquitos from other external
variables what makes very difficult to compare it with the other papers and
maybe these results should be taking into consideration as a kind of feedback
for a major model that includes the mosquito life dynamics.
At this stage I can say that for me the study by Parham
et al. seems to express the status of the current climate change –
illnesses affair. The problem, not only for malaria but for any vector-borne
disease and probably for any other disease, is extremely complex with a great
number of variables affecting it and with a high level of uncertainty, making
very hard to get a real and quantitative evaluation of future consequences and associated
problems.
