By: Eliana Zhang
When you read the headline, “Deadly bacteria found in aromatherapy spray sold at Walmart,” you would think that it would be something like Staphylococcus, a bacteria that has the potential to cause a life-threatening infection but is relatively harmless most of the time. Unfortunately, far from being an exaggerated threat, the bacteria in question– Burkholderia mallei– resides on the first tier of biological weapon agents along with Bacillus anthracis, which causes anthrax, and Yersinia pestis, which causes bubonic plague.
B. mallei infection (“glanders”) is one of the oldest diseases known to mankind, having been described by the likes of Aristotle and Hippocrates as one that primarily affects horses, donkeys, and mules– animals that formed the backbone of human transportation. Gaining access to host cells through lysis of the entry vacuole, it is able to initiate host cell fusion and create multinucleated giant cells, which not only allow it to evade the host’s immune system but also facilitates its spread to different cells. By leaving the vacuoles early, it is able to efficiently replicate inside the cell, from which it leaves early again and evades lysosomal defenses and other pathogen-killing agents that would normally pose a serious force against bacterial infections. As a result, developing a vaccine against B. mallei is difficult and complex; it would need to create a cell-mediated immune response as well as a humoral response to the bacteria in order to be effective.
Though glanders is easily transmitted to humans through food, cut, and touch, it has historically posed a threat to the supply of convoys, troops, and artillery by afflicting the horses that delivered them. Its first significant appearance as a military disadvantage occurred when it tore through Marshal Tallard’s cavalry before the Battle of Blenheim in 1704, helping the Duke of Marlborough win the battle. Before long, humans realized B. mallei’s potential as a weapon of war; during World War I, Germany deliberately spread B. mallei to infect and kill the animals that were being sent to the Allies. Such biological sabotage also started in 1915 on the American East Coast and grew to encompass Russian horses and mules on the Eastern front; Romanian, Norwegian, and Spanish animal supplies; and even Argentina, a neutral country on the other side of the Atlantic Ocean— one of the only documented attacks of intentional biowarfare against neutral countries. As a possible consequence of this, cases of human glanders in Russia increased after World War I.
During World War II, Japan was believed to have used B. mallei in their biological warfare research units. They most notably infected horses, civilians, and prisoners of war with glanders at the Pinfang Institute in China, which you might know from its infamous Unit 731. Though they did not end up actually creating a biological weapon out of the bacteria, it proved to be effective in tests on water supply contamination. Russia’s biological weapons program also took an interest in B. mallei and conducted field tests with it, reportedly killing some researchers during the course of the study before they went on to deploy it in Afghanistan during the 1980s.
Besides its high morbidity rate, B. mallei is lauded as a plague-level bioweapon because of its particularly low infectious dose. One would need to ingest about a million Salmonella bacteria to get food poisoning; B. mallei can infect a host with only ten live bacterial cells.
As a result, a cluster of four cases and two deaths of melioidosis sprang up in the United States, warranting investigation by the Centers for Disease Control and Prevention (CDC). Samples from a bottle of the Walmart aromatherapy spray from a Georgia patient’s home soon yielded the presence of B. mallei, and further testing confirmed that the genetic fingerprint of the bottle’s bacteria matched those found in the patients. Given that it wouldn’t take a large accident with B. mallei to potentially kill someone, Walmart’s sale of an aromatherapy spray with such a dangerous agent was negligent beyond all counts.
What did you learn?
How does B. mallei infect its host? It enters the host cell by rupturing the membrane of the entry vacuole. After, it is able to initiate host cell fusion and create multinucleated giant cells, which not only allow it to evade the host’s immune system but also facilitates its spread to different cells. By leaving the vacuoles early, it replicates efficiently, which contributes to its low infectious dose. After sufficient replication, it leaves the cell early, evading lysosomal defenses and other pathogen-killing agents that would pose a serious force against other bacterial infections.
When has B. mallei been used as a bioweapon in the past? Germany used it to infect livestock being delivered to the Allies in World War I. Though Japan never officially used it, the Pinfang Institute did research on its effectiveness in bioterrorism, and Russia did the same then legitimately used it in Afghanistan in the 1980s with devastating effects. Because it easily infects its hosts (and because its hosts oftentimes provide crucial animal transportation,) B. mallei ranks among some of the ideal bioweapons along with that of anthrax and plague.
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