Tag: plague

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Body Lice may be Bigger Plague Spreaders than Previously Thought

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Study could challenge widespread view that fleas, rats are the only contributors to outbreaks

Fluorescent image of a human body louse with Yersinia pestis infection (orange/red) in the Pawlowsky glands.
Image Credit: David M. Bland (CC0)

A new laboratory study suggests that human body lice are more efficient at transmitting Yersinia pestis, the bacterium that causes plague, than previously thought, supporting the possibility that they may have contributed to past pandemics. David Bland and colleagues at the United States’ National Institute of Allergy and Infectious Diseases present these findings in the open-access journal PLOS Biology on May 21st.

Y. pestis has been the culprit behind numerous pandemics, including the Black Death of the Middle Ages that killed millions of people in Europe. It naturally cycles between rodents and fleas, and fleas sometimes infect humans through bites; thus, fleas and rats are thought to be the primary drivers of plague pandemics. Body lice – which feed on human blood – can also carry Y. pestis, but are widely considered to be too inefficient at spreading it to contribute substantially to outbreaks. However, the few studies that have addressed lice transmission efficiency have disagreed considerably.

To help clarify the potential role of body lice in plague transmission, Bland and colleagues conducted a series of laboratory experiments in which body lice fed on blood samples containing Y. pestis. These experiments involved the use of membrane feeders, which simulate warm human skin, enabling scientists to study transmission potential in a laboratory setting.

They found that the body lice became infected with Y. pestis and were capable of routinely transmitting it after feeding on blood containing levels of the pathogen similar to those found in actual human plague cases.

They also found that Y. pestis can infect a pair of salivary glands found in body lice known as the Pawlowsky glands, and lice with infected Pawlowsky glands transmitted the pathogen more consistently than lice whose infection was limited to their digestive tract. It is thought that Pawlowsky glands secrete lubricant onto the lice’s mouthparts, leading the researchers to hypothesise that, in infected lice, such secretions may contaminate mouthparts with Y. pestis, which may then spread to humans when bitten.

These findings suggest that body lice may be more efficient spreaders of Y. pestis than previously thought, and they could have played a role in past plague outbreaks.

The authors add, “We have found that human body lice are better at transmitting Yersinia pestis than once appreciated and achieve this in more than one way.  We describe a new bite-based mechanism in which a set of accessory salivary glands unique to lice, termed the Pawlowsky glands, become infected with Y. pestis and secrete lubricant containing plague bacilli onto the insect’s mouthparts prior to blood feeding.”

Provided by PLOS

Categories : Diseases, Syndromes and ConditionsTags :

Human Transmission in Antibiotic-resistant Plague Outbreak

On By ModernMedia
Scanning electron micrograph of Yersinia pestis, which causes bubonic plague, on proventricular spines of a Xenopsylla cheopis flea.
 
Credit: National Institute of Allergy and Infectious Diseases/NIH


Analysing a recent outbreak of plague in Madagascar, a team of researchers uncovered evidence of human transmission of antimicrobial-resistant plague.

While COVID dominates the global awareness of infectious diseases, others are still out there, such as Yersinia pestis, which causes plague. Even though plague has been largely eradicated in the developed world, hundreds of people globally contract it each year.

When a human is infected with bubonic plague from a flea bite and it goes untreated, the infection can progress, spread to the lungs and resulting in pneumonic plague. Pneumonic plague is usually lethal if not treated quickly, and infected patients can transmit the disease to others via respiratory droplets. A team of scientists from Northern Arizona University’s Pathogen and Microbiome Institute, led by professor Dave Wagner, recently published their findings from a remarkable study involving antimicrobial resistant (AMR) plague.

Plague is considered to be a reemerging and neglected disease, particularly in the East African island country of Madagascar, which reports the majority of annual global cases. There is no vaccine for it, so preventing mortality from plague requires rapid diagnosis followed by antibiotic treatment. In Madagascar, the antibiotic streptomycin is usually the first-line treatment for plague. The researchers isolated a streptomycin-resistant AMR strain of Y. pestis from a pneumonic plague outbreak that occurred there in 2013, involving 22 cases, including three fatalities. The study was recently published in Clinical Infectious Diseases.

“By characterising the outbreak using epidemiology, clinical diagnostics and DNA-fingerprinting approaches,” Prof Wagner said, “we determined—for the first time—that AMR strains of Y. pestis can be transmitted person-to-person. The AMR strain from this outbreak is resistant to streptomycin due to a spontaneous point mutation, but is still susceptible to many other antibiotics, including co-trimoxazole. Luckily, the 19 cases that were treated all received co-trimoxazole in addition to streptomycin, and all of them survived.

“The point mutation, which also is the source of streptomycin resistance in other bacterial species, has occurred independently in Y. pestis at least three times and appears to have no negative effect on the AMR strain, suggesting that it could potentially persist in nature via the natural rodent-flea transmission cycle. However, AMR Y. pestis strains are exceedingly rare and the mutation has not been observed again in Madagascar since this outbreak.”

Source: North Arizona University

Categories : Diseases, Syndromes and Conditions General InterestTags :

Study Reveals Mediaeval Plague Victims Buried With Care and Attention

On By ModernMedia
Photo by Peter Kvetny on Unsplash

Mediaeval plague victims in the UK were mostly buried with care and attention, according to a new study from Cambridge University. 

In the mid-14th century, Europe was devastated by the Black Death which killed between 40 and 60 per cent of the population. For centuries afterward, waves of plague would continue to strike the region.

Due to the rapid onset of death in the absence of antibiotic treatment (less than a week for bubonic plague and under 48h for pneumonic plague), the disease leaves no visible evidence on the skeleton, so until now archaeologists have been unable to identify individuals who died of plague unless they were buried in mass graves.

Although it has been long believed that most plague victims in fact received an individual burial, this has been impossible to confirm until now.

By studying DNA extracted from the teeth of individuals who died at this time, researchers from the Wellcome Trust-funded After the Plague project, based at the Department of Archaeology, University of Cambridge, have identified the presence of Yersinia Pestis, the bacterial pathogen that causes plague. The study is available to read online in the European Journal of Archaeology.

These include people who received normal individual burials at a parish cemetery and friary in Cambridge and in the nearby village of Clopton.

Lead author Craig Cessford of the University of Cambridge explained: “These individual burials show that even during plague outbreaks individual people were being buried with considerable care and attention. This is shown particularly at the friary where at least three such individuals were buried within the chapter house. The Cambridge Archaeological Unit conducted excavations on this site on behalf of the University in 2016-2017.”

The individual at the parish of All Saints by the Castle in Cambridge was also buried with care; this stand in contrast to the apocalyptic language used to describe the abandonment of this church in 1365 when it was reported that the church was partly in ruins and ‘the bones of dead bodies are exposed to beasts’.”

The study also shows that some plague victims in Cambridge did, as expected, receive mass burials.

Yersinia Pestis was also identified in several parishioners from St Bene’t’s, who were found buried together in a large trench in the churchyard excavated by the Cambridge Archaeological Unit on behalf of Corpus Christi College.

Soon afterwards, this part of the churchyard was transferred to Corpus Christi College, which was founded by the St Bene’t’s parish guild to commemorate the dead including the victims of the Black Death. For centuries, the members of the College would walk over the mass burial every day on the way to the parish church.

Cessford concluded, “Our work demonstrates that it is now possible to identify individuals who died from plague and received individual burials. This greatly improves our understanding of the plague and shows that even in incredibly traumatic times during past pandemics people tried very hard to bury the deceased with as much care as possible.”

Source: University of Cambridge

Journal information: “Beyond Plague Pits: Using Genetics to Identify Responses to Plague in Medieval Cambridgeshire” – Craig Cessford, Christiana L. Scheib, Meriam Guellil, Marcel Keller, Craig Alexander, Sarah A. Inskip and John E. Robb. European Journal of Archaeology, https://doi.org/10.1017/eaa.2021.19