Bubonic Plague: An Airborne Toxic Event

by Alena M. James

Yersinia pestisis a gram negative, bacillus shaped bacteria that prefers to reside in an environment lacking oxygen (anaerobic). It is typically an organism that uses the process of fermentation to break down complex organic molecules to metabolize.  However, the organism is commonly referred to as being a facultative anaerobe, because it can live in the presence of oxygen and undergo respiration to generate energy for its cell. Its facultative capability is one reasons the organism can induce infection in highly oxygenated lung tissue.

This organism, primarily a zoonotic pathogen, has been held responsible for causing the bubonic form of plague responsible for the Black Death, the 14th century event that lead to the death of millions of Europeans. For years, the cause of the Black Death Plague pandemic has been linked to fleas. In much of Europe at this time, unsanitary living conditions provided the perfect breeding grounds for flea infested rats to flourish; while the fleas served as the perfect arthropod vector for Y. pestis to flourish.

The route of transmission of Y.pestis, from fleas to humans, was thought to occur via the urban cycle—when an urban rat becomes infected with fleas from a wild animal. Crowding in cities, poor hygiene, and unsanitary living conditions attracts large rat populations to the area. When a flea carrying Y.pestis bites a rat, the rat becomes sick and dies. No longer able to parasitize the rat, the flea moves from the rat to a new host. In crowded cities, the fleas from the dead rat will jump to humans to feed. When the flea bites the human it releases Y. pestis into the human’s cardiovascular system. Once in the cardiovascular system, the bacterial organism makes its way to the lymph nodes.  There it replicates and spreads throughout the body causing septicemia. As Y. pestis proliferates within the lymph nodes it also forms hemorrhagic necrosis throughout the body.  Painful swelling arises and the definitive painful symptom, the bubo,appears.  After infection, a patient develops a high fever and the organism can target specific organs of the body like the lungs, liver, and spleen. Without treatment, a patient has a 75% mortality rate.


Last week, British scientists performed comparative DNA analysis on bacterial samples collected from 25 excavated skeletons found in the Clerkenwell area of London. These remains dating back to the 14th century contained samples of Yersinia pestis, the bacteria responsible for the Black Death. In an attempt to evaluate the virulent nature of the pathogen, the Y. pestis DNA collected from these remains were compared to DNA from the Y. pestis responsible for the deaths of more than 30 people in Madagascar back in December 2013. Researchers concluded that the DNA of both organisms revealed a high percentage of similarity and that the pathogenic nature of the 14th century Y. pestis is no more powerful than the Y.pestsis responsible for the Madagascar killings.

After considering this information and examining the plausible death of the skeletons, scientists believe that the fast-acting killing capabilities of Y.pestis are only likely to take place through airborne transmission. This conclusion undermines the urban cycle transmission method and suggests that the Black Death was mostly caused by pneumonic plague and not bubonic. British scientists are determined to examine more modern cases to confirm this new hypothesis. If confirmed, we may see pneumonic plague identified as the causative agent for the 14th century plague pandemic thus altering our historical account of the Black Death.

For British scientists, the transmission of Y. pestsis through respiratory droplets is a much more likely scenario for achieving rapid kills versus the urban cycle transmission method. Bubonic plague is not infectious and there is no human to human transmission from the buboes that form.  However, pneumonic plague can be caused by bubonic plague if the Y. pestis pathogen makes its way via the lymph nodes to the lungs inducing infection. While in the lungs, the organisms are caught in respiratory droplets and are then disseminated into the air when an infected person sneezes or coughs. This quickly makes the host very infectious and a threat to those not yet infected.  The mortality rate for patients suffering from pneumonic plaque without treatment is 100%.

 

Image Credit: crossrail.co.uk

The Pandora Report 12.13.13

Highlights include pneumonic plague in Madagascar, ricin as a biological weapon, H7N9 in live markets in Hong Kong, Myanmar’s ratifying the BWC, and destroying sarin at sea. Happy Friday!

Madagascar hit by ‘pneumonic and bubonic plague’

In addition to the death of approximately 20 villagers who died of bubonic plague last week, a further two cases of pneumonic plague have been discovered. Pneumonic plague can be spread via aerosol. It must be treated within 24 hours; any later and the fatality rate approaches 100%. Understandably, there is concern amongst health officials in Madagascar that the disease will spread to neighboring villages and towns.

BBC – “Pneumonic plague is caused by the same bacteria that occur in bubonic plague – the Black Death that killed an estimated 25 million people in Europe during the Middle Ages. But while bubonic plague is usually transmitted by flea bites and can be treated with antibiotics, pneumonic plague is easier to contract and if untreated, has a very high case-fatality ratio, experts say. Madagascar’s health ministry director-general Dr Herlyne Ramihantaniarivo confirmed to the BBC that two cases of the plague had been reported”

Texas woman pleads guilty to ricin letters sent to Obama, Bloomberg
A Texan woman has been charged in the case involving ricin-laced letters sent to President Obama and Mayor Bloomberg. We’ve discussed the debate surrounding the classification of  ricin as a weapon of mass destruction before, so we do think its interesting they’ve charged her with use of a biological weapon.

CNN – “A Texas woman pleaded guilty Tuesday to a biological weapons charge after she was accused of sending ricin-laced letters to President Barack Obama and New York City Mayor Michael Bloomberg, prosecutors announced. Shannon Guess Richardson, 35, pleaded guilty to possession of a toxin for use as a weapon, prosecutors said in a statement. She could be sentenced to up to life in prison. A sentencing date has not yet been scheduled. Richardson, an actress, was accused of sending the letters earlier this year.”

Shenzhen Finds H7N9 Flu Virus in Markets Near Hong Kong
Three of 70 samples taken from 13 of Guangdong’s  live poultry market have tested positive for H7N9. For some reason, one of the vendors whose stall tested positive for H7N9 was still allowed to sell chickens. China is usually extremely vigilant concerning containment and effective biosurveillance, so the hesitation to shut the live poultry markets is a little baffling.  However, the stalls are  apparently being disinfected daily.

Bloomberg Businessweek –  “The 12 live poultry stalls at the Hengan Paibang market in Longgan district, one of the markets where authorities found a positive sample, were open today. The stalls get their chickens from the Buji Poultry Wholesale Market in Longgan, according to the market’s manager. ‘There’s been no order yet to shut down,’ said Zhang Jinghui, manager of the Paibang market. ‘We need to wait for instructions from the village committee. We are disinfecting the stalls everyday.’ About 30 chickens, ducks, pigeons and geese were stored in metal cages at his stall, next to a shed for slaughtering the poultry and a metal-spinning vat for defeathering.”

Myanmar Prepares to Ratify Chemical, Biological Weapons Treaties
While Myanmar, formerly known as Burma, has signed both the Chemical Weapons Convention and the Biological Weapons Convention, it has yet to ratify either treaty. There is still some debate over whether the military junta previously in charge had used chemical weapons on the rebels. Myanmar has been cooperating with IAEA inspectors to increase overview of its nuclear program.

Radio Free Asia – “Myanmar’s government asserts the country has no chemical, biological, or nuclear weapons programs. But ethnic armed rebel groups including the Kachin Independence Army (KIA) have accused the Myanmar military of using chemical weapons as recently as last year in their long-running war in the country’s borderlands. In the 1980s and early 1990s, the U.S. government voiced suspicions of a possible chemical weapons program under the military junta in Myanmar, naming China and North Korea as possible suppliers. Since then the U.S. has been less vocal in its concern about the issue. According to global security nonprofit organization the Nuclear Threat Initiative, there is currently ‘no evidence’ to suggest Myanmar has a chemical weapons program.”

Scientists raise alarm over plan to destroy Syria’s chemical weapons at sea
The Department of Defense’s plan to neutralize Syria’s chemical weapons, through hydrolysis, at sea, is coming under sharp criticism. The use of the technology at sea is unprecedented, and requires a tremendous deal of very careful estimating. Of course, when dealing with agents like sarin and VX, very careful estimating is not always enough. News of the criticism comes at the same time as the UN confirmed the repeated use of chemical weapons in the Syrian conflict. 

Washington Times – “‘There’s no precedence. We’re all guessing. We’re all estimating,’ said Raymond Zilinskas, director of the Chemical and Biological Weapons Nonproliferation Program at the James Martin Center for Nonproliferation Studies, who worked as a U.N. biological weapons inspector in Iraq in 1994. ‘For example, you don’t know if the sarin is pure. The Iraqi sarin was rather impure, and had a lot of contaminants, and we don’t know if that’s amenable to hydrolysis,’ said Mr. Zilinskas, a professor at the Monterey Institute of International Studies at Middlebury College. Under the Pentagon plan, the toxic stockpile would be transported to the Syrian port of Latakia, loaded onto a non-U.S. vessel and shipped to a third country. From there, a U.S. cargo ship would take the arsenal to sea for destruction. Richard M. Lloyd, a warhead technology consultant at Tesla Laboratories Inc. who tracks weapons being used in Syria, said he has little confidence in the regime’s ability to transport the weapons safely.”

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Drug Resistant H7N9 Retains Pathogenicity

(image: Wmeinhart/wikimedia)

Bubonic Plague in Madagascar

In the latest outbreak of bubonic plague in the country, 20 people died from the disease last week in north-western Madagascar. Bubonic plague, caused by the bacteria Yersinia pestis, is endemic to the island nation, and resulted in 60 fatalities last year alone. The island’s prisoners are especially vulnerable, due to pervasive unsanitary conditions enabling a large rat population in local prisons. However, last week’s outbreak occurred in the relatively remote village of Mandritsara. Health authorities are currently investigating the outbreak.

Plague is spread to humans through infected fleas, often from rats. Bubonic plague is something we’ve written about extensively here on the Pandora Report, usually in a historical context. It’s easy to forgot that for many nations, outbreak of the disease remains a very real fear today.

(image: wikimedia commons)

Image of the Week: Plague

This week’s image shows us everyone’s favorite scourge – plague! Depicted below is Yersinia pestis, the causative agent of plague, sticking to  the spines of a flea. Throughout history, Y. pestis has contributed to some of the most serious pandemics, at one point killing nearly half of Europe’s population. While plague still pops up occasionally (it’s endemic in the prairie dog population of the American Southwest), prompt treatment with antibiotics prevents serious illness. However, in aerosol form, unless antibiotics are administered in the first 24 hours, infection is almost always fatal. This is a big part of why Y.pestis is considered a potential bioterrorist agent.

Image: NIAID
Image: NIAID

The Pandora Report 7.26.13

Highlights include Saudi Arabia’s hajj travel restrictions, zoonotic adenoviruses, PEDv, studying the 1918 pandemic, and plague in people you know. Happy Friday!

Virus fears, Mecca work downsizes hajj pilgrimage

Saudi Arabian officials, responding to fears over hajj contributing to MERS potential spread, have significantly cut the number of pilgrims allowed to perform the annual pilgrimage to Mecca. Numbers of pilgrims from within Saudi Arabia have been cut by half, and those travelling to Mecca from other countries by one fifth. Officials were quick to stress that the decision was based on “exceptional” circumstances, and may be revised as MERS’ spread is tracked. The decision is an interesting one, given that the WHO’s specially convened MERS committee just last week decided against travel restrictions.

Economic Times – “Fears of an outbreak of the deadly MERS virus in Saudi Arabia and construction in the holy city of Mecca have forced cuts in the numbers of pilgrims permitted to perform this year’s hajj. Millions of Muslims during the annual pilgrimage head to Mecca and Medina, Islam’s two holiest sites, providing a possible means for MERS to spread around the globe as pilgrims who may become infected return to their home countries.”

Adenoviruses May Pose Risk for Monkey-to-Human Leap

Most of the world’s deadliest viruses are zoonotic (ebola, anyone?) When a new virus is determined to spread from animals to humans, it’s therefore not surprising, but it’s often troubling, as humans often have little to no immunity to such bugs. The ongoing outbreaks of H7N9 and MERS are both recent examples. Now, researchers at the University of San Francisco have determined that a novel adenovirus – identified just four years ago – may be able to cause disease in humans. In a study involving adenovirus C, the researchers were able to trace the virus’ spread from an enclosed Californian baboon colony to the human staff members caring for them.

UCSF – “‘This study raises more concerns about the potential of unknown viruses to spread from animals to humans,’ said Chiu, who is an assistant professor of medicine at UCSF. ‘We still don’t understand the full extent of viruses that exist in the world and their potential to cause outbreaks in human populations.’ Last year, Chiu and colleagues also identified another new adenovirus, named simian adenovirus C, which sickened four of nine captive baboons and killed two of them at a primate facility in 1997. Several staff members at the facility also complained of upper respiratory symptoms at the time of the outbreak. Re-examining the samples many years later, Chiu and his colleagues found antibodies targeted to simian adenovirus C in the human samples.”

Deadly Pig Virus Slips through U.S. Borders

The porcine epidemic diarrhea virus (PEDv) continues to rage in the United States, having now spread to 14 states, including outliers like North Carolina. With the virus’s fatality rates occasionally approaching 100% in piglets, its spread has USDA and the US pork industry both (understandably) very nervous. The virus’ source in the United States remain unknown, and efforts to sequence it have been hampered by a couple things. First, it is notoriously difficult to culture – unsurprisingly, pig viruses tend to grow best in pigs. Second, the restrictions the US had in place to prevent the virus entering the US in the first place are making acquisition of the right lab materials to culture it difficult. With the virus’ apparent preference for cooler temperatures, and Autumn approaching, scientists are racing to determine the source before the outbreak spreads further.

Scientific American –  “‘How this virus got here, that’s the million-dollar question,’ says James Collins, director of the Veterinary Diagnostic Laboratory at the University of Minnesota in St Paul. The pathogen, a type of coronavirus called porcine epidemic diarrhea virus (PEDV), was first identified in the United Kingdom in 1971, and it caused mass epidemics in Europe in the 1970s and 1980s…The virus can spread quickly by a fecal–oral route and infect entire herds. And although adult pigs typically recover, PEDV can kill 80–100% of the piglets it infects. The virus poses no health threat to humans. The US Department of Agriculture (USDA) had tried to keep PEDV and other diseases out of the country by restricting imports of pigs and pork products from certain nations, such as China. But on 10 May, the Veterinary Diagnostic Laboratory at Iowa State University in Ames confirmed that PEDV had infected pigs in Iowa, the leading producer of US pork.”

New Light Shed On Cause of Pandemic Influenza

After using mathematical models to analyze the 20th century’s worst pandemics, the 1918 Spanish flu pandemic.  Researchers have developed three key factors which exacerbated the pandemic’s impact – school openings and closing, temperature fluctuations, and human behavioral changes.

Science Daily – “Dr He and the researchers further applied this model to the reported influenza mortality during the 1918 pandemic in 334 British administrative units and estimate the epidemiological parameters. They have used information criteria to evaluate how well these three factors explain the observed patterns of mortality. The results indicate that all three factors are important, but behavioural responses had the largest effect.”

My Friends Got the Plague, and This New Test Could Have Helped Them

It’s easy to believe that the bacteria and viruses we write about exist only in distance countries or highly secure labs. As the above blog piece illustrates, sometimes all it takes is a vacation to New Mexico. The piece also discusses the importance of science’s ugly stepchild – basic research.

Motherboard (VICE) – “Despite very low incidence and the availability of treatment with modern antibiotics, the plague is still a very deadly illness whose prognosis becomes worse by the minute when it strikes. This technique is useful because it provides a quick way of, at the very least, ruling out the illness, which is so often overlooked. Importantly, the researchers note that their technique would not have been possible without previous basic research, which many consider a lesser priority than corporate-sponsored applied research.”

(image courtesy of Al-Hijr)