Malaria is a major threat to public health worldwide. The culprits behind this threat are the four contributing members of the genus Plasmodium. The deadliest amongst the four parasites is Plasmodium falciparum.
Resistance to chloroquine - the cheapest and the most used drug - is spreading in almost all the endemic countries. Such resistance is the result of strong selection pressure exerted by large scale use of the drugs in treating patients. It appears that the parasite is able to tolerate the drugs used against it.
Resistance to chloroquine was first reported in 1988 in Dakar. Mutations in the gene that codes for transmembrane protein P.falciparum chloroquine resistance transporter (pfcrt) have been largely associated with chloroquine resistance. A study conducted by researchers from Harvard School of Public Health on isolates obtained from West Africa identified several markers of chloroquine resistance. The pfcrt 76T allele has been linked with chloroquine resistance.
Resistance to Sulfadoxine-pyrimethamine combination therapy which replaced chloroquine is spreading rapidly in the African continent. Studies on this combination therapy are producing revealing insights into the development of resistance to malarial parasites. Around five origins of resistance have been reported in the dhps locus. As per the gene maps of the African parasites generated by Cally Roper and colleagues, codon 436, 437 and 540 in dhps show the presence of mutation.
Failure of classic antimalarial drugs and their combination therapies in controlling the spread of malaria has put the focus on another anti-malarial drug - artemisinin. Yet from May 2009 reports started to emerge about artemisinin resistance in P.falciparum. It is the world's most powerful anti-malarial and so signs that the parasite may be developing resistance to it is worrying health officials. It has lead to renewed calls for people to be better educated about how to use the therapeutics once they are prescribed.
Researchers are also heading back to their lab benches to try and find out how the parasite might be able to combat this powerful weapon.
At the time of writing (June 2009) a vaccine against the disease is at last entering the final stages of trials, and may be ready for use in a few years time.