Friday 6 October 2017

Plague outbreak kills at least 30 In Madagascar.

An outbreak of Plague has killed at least 30 people in Madagascar since late August this year, according to the World Health Organisation, with many more having contracted the disease. Plague outbreaks are common in the Malagasy dry season (from May to October), with about 400 cases of the disease reported each year, however the rapidity with which this outbreak has spread, combined with the high mortality rate, has concerned medical authorities on the island. This is largely due to the fact that the majority of the cases reported, including 21 of the fatalities, have been of the Pneumonic variety of the disease, which infects the lungs and is spread through coughing, rather than the more usual Bubonic variety, which infects the lymph-nodes and is typically spread via the exchange of bodily fluids via a parasite vector such as a Flea. The majority of those who have died are thought to have been Malagasy citizens, though one is reported to have come from the Seychelles.

A health-worker spraying a classroom with insecticide in Antanarivo in order to stop the spread of Plague via Insect vectors. Anadolu Agency/Getty Images.

Plague is caused by Yersinia pestis, the same Bacterium that causes Bubonic Plague. The Bacterium is indigenous to Madagascar, with outbreaks of Plague being a regular occurrence during the dry season (May to October). The Pneumonic form of the illness is considered particularly worrying, as in this instance the lungs become infected with the disease, leading to coughing, which can spread the disease, and pneumonia, which can rapidly kill patients. Yersinia pestis generally responds well to antibiotics, but the alarm caused by the diseases it causes can provoke excessive use, leading to shortages when they are most needed.

Mass of Yersinia pestis Bacteria. Wikipedia.

Yersinia pestis is a Gram-negative, facultatively anaerobic (i.e. capable of using oxygen, but not needing it), rod-shaped Gammaproteobacteria, related to other pathogenic Bacteria such as Vibrio cholerae (Cholera), and Esherchia coli (food poisoning).It is a zoonotic disease, naturally occurring in a variety of Rodents, but capable of infecting Humans, typically via Fleas, which spread the disease by biting both their regular Rodent hosts and Humans. Zoonotic diseases can be particularly dangerous, as Humans are not part of their natural life-cycle, with the effect that they are not under evolutionary pressure to keep Human hosts alive in order to perpetuate themselves. Such diseases typically have short duration and a high fatality rate, though epidemics usually burn out quickly.

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