Marines deploying to remote areas of Australia encounter numerous diseases not commonly found in North America. One of the diseases is Burkholderia pseudomallei (B. pseudomallei) which causes the disease melioidosis.
A team of researchers from Naval Medical Research Center (NMRC) began conducting an observational study to understand the disease risks associated with B. pseudomallei to service members deployed to Australia. The team works in collaboration with Dr. Bart Currie of the Menzies School of Health Research, headquartered in Darwin and one of the world's foremost authorities on melioidosis.
U.S. Marines have been deploying to Australia since 2012 as part of Marine Rotational Force-Darwin (MRF-D) to participate in joint training exercises. According to the Center for Disease Control (CDC) Australia is one of the countries with the greatest number of cases of Melioidosis.
B. pseudomallei is a pathogen of humans and animals that enters the body through skin abrasions, burns, or wounds infected by contaminated soil or through inhalation of contaminated dust. Melioidosis is not contagious and can take different forms from localized skin infection to an infection of the lungs associated with high fever, headache, chest pain, and coughing, as well as infection of bones and pus-filled abscesses in the skin, lungs, or other organs. Acute melioidosis is characterized by a rapid onset while chronic melioidosis is characterized by symptoms lasting longer than two months.
The study’s principle investigator, Dr. Kevin Schully, from NMRC’s Biological Defense Research Directorate has a wealth of experience in human clinical studies. He has studied B. pseudomallei for 14 years and was inspired to follow the MRF-D rotations since learning of their existence in 2014.
“It was important to understand the risks to MRF-D. This is the first major presence of U.S. forces in a B. pseudomallei endemic area since the Vietnam War. During that time, there were hundreds of melioidosis cases that we know of and numerous dormant infections that manifested years later,” said Schully.
“We are very cognizant of the level of seriousness that the Northern Territory of Australia takes in preventing and mitigating infectious disease, especially in light of their handling of the COVID-19 pandemic during our last two rotations. We have remained compliant with all regulations set forth by NT Health and remain committed to maintaining the safety of the community in which we live and work,” said Col. David Banning, MRF-D commanding officer.
Biosurveillance is a key component of the military’s approach to prevent infections during deployments. Vector surveillance is credited for characterizing the threat of leishmaniasis to coalition forces in Iraq, where mitigation strategies dramatically decreased the incidence of leishmaniasis cases.
Recently the CDC reported cases of melioidosis in the United States. This could be an indication of a new emergence of this disease and sheds light on the importance of infectious disease research and surveillance.
Since the beginning of the study, NMRC has followed five rotations of MRF-D Marines and Sailors from 2016-2020 to study B. pseudomallei risks and is currently following the 2021 rotation. 1,488 voluntary participants provided blood samples before, during and after the deployment.
“There was one serious B. pseudomallei infection in MRF-D so far and there have also been numerous asymptomatic infections. The analysis is ongoing so we are unable to attach an exact number right now,” said Schully. Melioidosis is not contagious but because of its ability to lie dormant for long periods of time, it is important to understand the frequency with which MRF-D participants are experiencing these asymptomatic infections.
Force Health Protection measures are essential and in place to protect service members overseas. The study protocol is structured to allow the addition of surveillance studies for other diseases. The study was expanded to include Ross River Virus (RRV), Australia’s most common and widespread mosquito-borne pathogen along with Coxiella burnetti C. burnetti is also found in Australia. Both C. burnetti and B. pseudomallei are categorized as “Category B bio-terrorism agents by the CDC increasing the importance of including them in the research.
“Our medical readiness is absolutely critical to maintaining an operational capable force, ready to respond to crises and contingencies in the Indo-Pacific region. Our robust medical staff are essential for ensuring the Marines and Sailors of Marine Rotational Force - Darwin are cared for and medically prepared to carry out their duties,” added Banning.
The global pandemic had a significant effect on the study and NMRC included SARS-CovV-2 testing. Pre-COVID, the MRF-D participants arrived and left at the same time. Due to COVID restrictions, the MRF-D participants arrived in waves followed by 14-day quarantine periods creating a challenge for the research team in comparing the different groups. Due to restrictions the team was not permitted to travel to Australia to continue the study there.
“They also have different experiences while they are there. Each rotation usually has elements in a variety of training areas around Australia. Since the pandemic, the MRF-D members are restricted to Darwin and the Northern Territory. It will be difficult to compare results from these rotations to the earlier ones,” said Schully.
COVID also presented an additional unique opportunity for the study since the majority of Marines enrolled in February of 2021 were vaccinated with the Moderna COVID-19 vaccine. Due to the timing and age restrictions during the initial vaccine rollout, this provided the researchers the possibility to expand the study platform even further.
“Once they return from Darwin, we will leverage this unique group to examine the magnitude, durability and trajectory of the immune response to the Moderna COVID-19 Vaccine in this young, healthy American population,” said Schully.
While the study team is unable to travel to Australia, pre- and post-deployment activities at the Battalion’s home base in California have allowed the study to continue to follow the 2020 and 2021 rotations.
“The fact that we are able to continue, while it hasn’t been ideal, has been invaluable. Our hope is that 2022 rotation looks more like the pre-pandemic rotations and we can continue. That being said, the 2020 and 2021 rotations have been productive and produced valuable information,” said Schully.
MRF-D deploys to Australia and trains to designated expeditionary operation task, enhances U.S.-Australian interoperability, and conducts regional engagement in order to prepare for crisis and contingency response, advance USMC warfighting concepts, enhance regional security, and demonstrate the strength of the U.S.-Australian Alliance,
NMRC's eight laboratories are engaged in a broad spectrum of activity from basic science in the laboratory to field studies at sites in austere and remote areas of the world to operational environments. In support of the Navy, Marine Corps, and joint U.S. warfighters, researchers study infectious diseases, biological warfare detection and defense, combat casualty care, environmental health concerns, aerospace and undersea medicine, medical modeling, simulation and operational mission support, and epidemiology and behavioral sciences.