Plague outbreak in remote Madagascar puzzles investigators
Plague, though terrifying, is nothing new in Madagascar, where around 600 cases are reported annually. But there was something different about a suspected plague outbreak reported last December. The outbreak’s location was far away from recent outbreaks and implied plague had spread to new parts of the island nation, but health officials couldn’t explain it.
In December 2016, the Ministry of Public Health of Madagascar (MoPH), in line with the International Health Regulations (2005), alerted WHO to an outbreak of plague in Befotaka district in south-eastern Madagascar. The IHR requires countries to report to WHO any situation that might constitute a public health event of international importance. The outbreak began in August, but Befotaka is so remote and lacking in basic services – such as telecommunications and health facilities – that health officials only learned about the outbreak in December.
“Plague is a disease of poverty, because it thrives in places with poor sanitary conditions and health services,” said Dr Arthur Rakotonjanabelo, WHO health emergencies focal point in Madagascar. “Befotaka district is one of the poorest, most remote, dangerous and inaccessible places in Madagascar, but we hadn’t seen plague there since 1950.”
Getting to the Befotaka district is arduous. The trip from the capital in Antananarivo to Befotaka begins with two days on bumpy paths only accessible by four-wheel drive vehicles followed by three days of walking. Extremely isolated, the district is also dangerous because of insecurity.
Representatives from the MoPH and Institut Pasteur de Madagascar (IPM) travelled overland to investigate the outbreak on 2 December 2016 with the financial support of IPM and Commission de l’Océan Indien. WHO helped to plan this mission.
“Upon our arrival after almost 1.5 days of walking, rapid diagnostic tests for plague, developed at IPM, were carried out on a person with suspected bubonic plague, on a person who was suspected to have died from plague, and on a dead rat. All revealed positive results,” reported Dr Charles Emile Ramarokoto, an IPM epidemiologist.
However, after collecting some samples for laboratory analysis, treating some people and starting pest control efforts, the team’s mission had to be cut short because of insecurity and direct threats to team members.
On a second attempt on 15 December 2016 for Befotaka, the team was transported by a military helicopter funded by Le Bureau National de Gestion des Risques et Catastrophes, Madagascar’s office for disaster risk management. The second try was also shortened due to insecurity and threats.
What is plague?
Plague is an infectious disease caused by the bacterium Y. pestis, usually found in small mammals and their fleas. It is transmitted between animals and humans by the bite of infected fleas, direct contact with infected tissues, and inhalation of infected respiratory droplets. It is a very severe disease in people, with a case-fatality ratio of 30%-100% when left untreated.
In Madagascar, the black rat constitutes the main animal reservoir of plague. In Befotaka and other parts of Madagascar, black rats often live in people’s straw-roofed houses. Fleas carry the plague bacterium among rats, but they can also infect humans. Pest control is vital in stopping and preventing the spread of a plague outbreak.
People infected through flea bites usually develop flu-like symptoms after an incubation period of 3-7 days. Typical symptoms are the sudden onset of fever, chills, head- and body-aches and weakness, vomiting and nausea. Common antibiotics are efficient to cure plague, if they are delivered very early, because the course of the disease is usually rapid.
Bubonic plague is the most common form of plague, but cannot be transmitted human-to-human. However, out of the human cases with bubonic plague, around 10% develop pneumonic plague, meaning the infection continuing to spread in the organism gets into their lungs. The occurrence of such clinical forms makes the control of an outbreak much more challenging because people in close contact with pneumonic cases can be directly contaminated by respiratory droplets, such as from coughing.
“You can become contaminated in the morning and be dead by the evening,” said Dr Eric Bertherat, a WHO epidemiologist who joined the second mission. “Untreated plague can kill that fast and that’s why we knew we urgently needed to get back to Befotaka.”
Determined to succeed
Deeply concerned that the two first missions were cut short, partners, including WHO, made arrangements for a follow-up mission to investigate the outbreak in Befotaka along with another suspected outbreak in the neighbouring Ihorombe region. WHO joined the second mission in late January 2017 with participants from the MoPH, IPM and Red Cross Madagascar.
In an effort to cut down on travel time, reduce security risks, and quickly bring samples back to the IPM’s laboratory, the team returned to the area via helicopter. Transportation was arranged by WHO, with funding from the UN Office for Coordination of Humanitarian Affairs. Added security and logistical support were provided by Madagascar’s disaster risk management bureau.
“The only way this mission happened was through the cooperation and support of many partners bringing their different strengths, skills and assets together,” said Dr Maherisoa Ratsitorahina, Director of Epidemiological Surveillance of the MoPH. The joint investigation found 126 cases of plague, including 30 deaths, out of which 7 cases were confirmed as plague, 11 were considered probable and 108 suspected. Laboratory confirmation was completed by the Plague Research Unit at IPM, a WHO Collaborating Centre. The mission also provided treatment to people infected or suspected to be infected and increased pest control efforts.
Outcomes of the investigation
For investigators, this event shows an expansion of the natural plague focus of the central plateaux, which has been observed for several years. Human activities, including deforestation, may have triggered this outbreak.
“Scientific investigations conducted on the circulating plague strains should provide key insights in the coming months,” said Dr Minoarisoa Rajerison, Head of Plague Research Unit at IPM.
The at-risk population for plague in Madagascar has now increased by at least several thousand. Plague remains a top-ranked public health issue in the country.
Treatments and next steps beyond plague
Next steps for WHO and its partners will include continued medical support and prevention measures for plague, as well as ramping up pest control and placing greater disease surveillance capabilities in the new plague-prone areas. Beyond the plague, investigators encountered a population with limited access to clean water, electricity, basic health and nutrition needs.
“We saw many needs and have called in other partners, requesting they return with us to help the people in various ways, such as ensuring greater access to basic health care, routine vaccinations and nutrition,” said Dr Charlotte Ndiaye, WHO Representative for Madagascar.