The human ecology of climate change - Climate Change: Biological and Human Aspects - page 406

would be to avoid the use of single-drug treatment (monotherapy) and instead use
cocktails of pharmaceuticals or artemisinin combination therapies (sometimes known
as ACTs). So, in January 2006 the WHO appealed to all pharmaceutical companies to
stop marketing oral artemisinin monotherapies and 13 countries over the subsequent
3 months agreed to withdraw marketing authorisation for such monotherapies (WHO,
2006).
The ranges of many other diseases are likely to change with climate. Among
those of major concern is Chagas' disease or American trypanosomiasis, a South
American variation of the sleeping sickness (trypanosomiasis) that affects central
Africa. Chagas' disease is named after the doctor who researched the affliction in
northern Brazil during the building of a railway in 1909. About 18-20 million people
in Central and South America and the USA are at risk of contracting Chagas' disease.
Its geographical distribution ranges from the southern USA to southern Argentina
and Chile. It is transmitted by the blood-sucking insect Triatoma infestans , and other
species, which carry the protoctistan Trypanosoma cruzi . It originally affected rodents
and marsupials but has adapted to human encroachment. Unlike African sleeping
sickness, the trypanosomes do not multiply in the blood but become localised in
various organs. The disease causes long-term, essentially untreatable debilitation
and, by affecting heart muscle, it is a major cause of chronic heart disease and sudden
death in apparently healthy young people.
Conversely, with the related African sleeping sickness the brain and the meninges
(the covering of the brain and spinal cord) become infected with Trypanosoma brucei
and, if treatment is delayed, it usually proves fatal. The WHO estimates that between
300 000 and 500 000 people are affected worldwide, and that the disease threatens
60 million people in the poorest underdeveloped countries. As for treatment, relatively
drastic measures are required. In the acute stage of the disease pentamidine is given.
If the parasite is also in the central nervous system, the drug melarsoprol is used,
so exposing patients to serious risk, especially of arsenic encephalopathy, of which
almost 1000 people die each year. Both substances are administered directly into the
bloodstream. There is no vaccine or chemical prevention due to the relative toxicity of
the drugs, so it is necessary to prevent bites from the tsetse fly (of the genus Glossina )
and control the places where the fly lives.
Dengue, which covers both the milder 'breakbone fever' and the more serious
but rarer haemorrhagic fever, is caused by arboviruses that are transmitted by Aedes
mosquitoes. Dengue fever can be caused by any one of four types of dengue virus:
DEN-1, DEN-2, DEN-3 and DEN-4. A person can be infected by at least two if
not all four types at different times during their lifetime, but only once by the same
type. Symptoms of typical uncomplicated dengue usually start with fever of up to
40.5 ◦ C within 5-6 days of a person being bitten by an infected mosquito. Other
symptoms include severe headache, retro-orbital (behind the eye) pain, severe joint
and muscle pain, rash, nausea and vomiting. Of interest to clinicians is that most
infected children never develop typical symptoms. There is no specific treatment
for dengue fever, and most people recover completely within 2 weeks. Dengue is of
particular concern because the vectors are associated with human environments and,
unlike many anopheline mosquitoes, they prefer to feed on humans. Consequently,
when epidemics take place they do so rapidly.