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Eliminating Plague Reservoirs

650 years ago the Plague wiped out one third of the global population in just 5 short years. This period is known as the Black Death, as if it was the result of the grim reaper himself. Yet it wasn’t supernatural punishment. It was the work of the tiny Yersinia pestis; a Gram-negative, facultative anaerobic, rod-shaped coccobacillus. Which simply means it’s a bacteria that is kinda circular/kinda rod shaped, can survive without oxygen if need be, and has an extra membrane.

If you were to look at it under a microscope, you would find something that looks like this:

Scanning Electron Micrograph of Yersinia Pestis

The microscopic Yersinia pestis leads to plague in humans by hitching a ride when a flea bites an infected rodent. The gut of this flea then gets blocked by a buildup of Y. pestis’ biofilm. When the flea attempts to feed again, Y. pestis is regurgitated into the second flea bite, spreading the infection.

Humans bitten by an infected flea usually develop the bubonic form of plague, which produces the characteristic plague bubo (a swelling of the lymph node). If the bacteria reach the lungs, the patient develops pneumonia (pneumonic plague), which enables the plague to spread from person to person through coughing.

Plague Reservoirs

It is thought that Y. Pestis circulates at low rates within populations of certain rodents without causing excessive die-off.  Many types of animals – rats, squirrels, prairie dogs, chipmunks, mice, voles, and rabbits, to name a few-can all be affected by plague. These infected animals and their fleas serve as long-term reservoirs for the bacteria. This is called the enzootic cycle.

Occasionally, other species become infected, causing an outbreak among those animals called an epizootic. Humans are usually more at risk of contracting a Y. Pestis infection during, or shortly after, a plague epizootic outbreak.

Plague in the modern age

It is because of these cycles that, 650 years later, people are still falling victim to the Plague.

If caught early, bubonic plague can be successfully treated with antibiotics. Pneumonic plague, on the other hand, is one of the most deadly infectious diseases; patients can die in as few as 24 hours after infection. In fact, in November 2014 there was a plague outbreak in Madagascar which infected 114 people, killing 40 of them. Globally, over 1000 people die from the plague each year.

How to eliminate plague reservoirs

With current antibiotics, we could completely cure everyone of plague. Then the next day someone could still come down with a fresh infection. Such is the nature of endemic infectious disease–another outbreak is always lurking just one small flea bite away.

If we consider this alongside the rising prevalence of antibiotic resistant strains, it is entirely possible that another Plague pandemic could occur. Even in this era of modern medicine.

To prevent a sudden outbreak, we need an alternative approach to infection control: intervention at the reservoir level.

By taking a proactive approach and attacking the infectious agents at the source, we can remove pathogens such as Yersinia pestis from the wild and remove the chance of a new surprise outbreak.