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| Location of Island of Madagascar |
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Outbreaks of plague have become yearly occurrence in Madagascar, and in recent years this small island nation has reported between 30% and 50% of the world's cases. Outbreaks generally occur in the rural highlands - above the 800m level - and usually peak between October and December.
We've looked at plague in Madagascar before (see 2014's ECDC Rapid Risk Assessment: Plague In Madagascar and 2013's Bubonic Plague: Forgotten, But Not Gone).A 2013 study, published in the Journal PLoS Neglected Tropical Diseases suggests that resistant black rats, endemic fleas, and certain cultural practices may all play a part in Madagascar's unusually high incidence of plague.
PLoS Negl Trop Dis. 2013 Nov 7;7(11):e2382. doi: 10.1371/journal.pntd.0002382. eCollection 2013 Nov.
Understanding the persistence of plague foci in Madagascar.
Andrianaivoarimanana V1, Kreppel K, Elissa N, Duplantier JM, Carniel E, Rajerison M, Jambou R.
Abstract
Plague, a zoonosis caused by Yersinia pestis, is still found in Africa, Asia, and the Americas. Madagascar reports almost one third of the cases worldwide. Y. pestis can be encountered in three very different types of foci: urban, rural, and sylvatic. Flea vector and wild rodent host population dynamics are tightly correlated with modulation of climatic conditions, an association that could be crucial for both the maintenance of foci and human plague epidemics.
The black rat Rattus rattus, the main host of Y. pestis in Madagascar, is found to exhibit high resistance to plague in endemic areas, opposing the concept of high mortality rates among rats exposed to the infection. Also, endemic fleas could play an essential role in maintenance of the foci. This review discusses recent advances in the understanding of the role of these factors as well as human behavior in the persistence of plague in Madagascar.
Bubonic Plague (Yersinia Pestis) - carried by rats and transmitted by fleas - sets up in the lymphatic system, resulting in the tell-tale buboes, or swollen lymph glands in the the groin, armpits, and neck.
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| Credit CDC |
Bubonic plague is the most common presentation, however in rare cases, Pneumonic Plague may develop. Here the infected person develops a severe pneumonia, with coughing and hemoptysis (expectoration of blood), and may spread the disease from human-to-human.
Since plague is fairly easily treated with antibiotics, it isn’t much of a public health menace in the developed world. In areas where treatment isn’t readily available, however, mortality rates run 40%-60% and untreated pneumonic plague is almost always fatal.
Based on numbers alone, Madagascar's annual plague outbreaks would be troubling, but in recent years we've seen:
- an increase in the number of cases reported from lower elevations, and in urban areas
- an earlier start to the (historically) fall plague season
- and an increase in the number of pneumonic plague cases
From 23 August to 30 September 2017, a total of 73 suspected, probable, and confirmed cases of pneumonic plague, including 17 deaths have been reported in Madagascar. The diagnosis was confirmed by the Institut Pasteur de Madagascar by polymerase chain reaction test or using rapid diagnostic test.
The outbreak started following the death of a 31-year-old male from Ankazobe District in the Central Highlands (Hauts-Plateaux), a plague-endemic area. Since then, the Ministry of Public Health of Madagascar enhanced field investigations, contact tracing, surveillance, and monitoring all close contacts.
As of 30 September, 10 cities have reported pneumonic plague cases and the three most affected districts include: the capital city and suburbs of Antananarivo (27 cases, 7 deaths), Toamasina (18 cases, 5 deaths), and Faratshio (13 cases, 1 death).
On 27 September, during the Coupe des clubs champions de l'océan Indien (a basketball championship held between 23 September and 1 October), a Seychellois basketball player, died in a hospital in Madagascar by pneumonic plague. The Ministry of Public Health of Madagascar immediately started an investigation and there is ongoing contact tracing of all the individuals he came into contact with. Chemoprophylaxis as a precautionary measure has been given to all close contacts.
In addition to the 73 cases of pneumonic plague, from 1 August to 30 September, 58 cases of bubonic plague including seven deaths have been reported. One additional case of septicaemic plague has also been reported, and one case where the type is not specified.
Public health response
The Ministry of Public Health of Madagascar activated crisis units in Antananarivo and Toamasina and all cases have been provided access to treatment at no cost.
There are public health response measures which include:
- Ongoing investigation of new cases
- Isolation and treatment of all pneumonic cases
- Active finding and tracing of contacts and provision of chemoprophylaxis
- Strengthening of the epidemiological surveillance in the affected and surrounding districts
- Disinsection of affected areas, including rodent and vector control
- Raising public awareness on prevention
- Raising awareness among health care workers and providing information to improve case detection, infection control measures
- Providing information about infection control measures during burial practices
(Continue . . . )WHO risk assessment
Plague is an infectious disease caused by the bacteria Yersinia pestis, a zoonotic bacteria, usually found in small mammals and their fleas. It is transmitted between animals from their fleas. Humans can be contaminated by the bite of infected fleas, through direct contact with infected materials or by inhalation.
There are three forms of plague infection, depending on the route of infection: bubonic, septicaemic and pneumonic (for more information, see the link below).
Pneumonic plague-or lung-based plague is the most virulent form of plague and can trigger severe epidemics through person-to-person contact via droplets in the air. The incubation period can be as short as 24 hours. Typically, the pneumonic form is caused by spread to the lungs from an advanced bubonic plague. However, a person with secondary pneumonic plague may form aerosolized infective droplets and transmit plague via droplets to other humans. Untreated pneumonic plague is always fatal.
Plague is an endemic disease in Madagascar; cases (predominantly bubonic plague) are reported nearly every year, during the epidemic season (between September and April).
However, the ongoing pneumonic plague event has been reported in a non-endemic area and in densely populated cities for the first time.
A pneumonic plague is a form of plague that is transmissible from person-to-person, with a potential to trigger severe epidemics if inadequately controlled. Detection of this outbreak occurred more than two weeks after the first case died during which cases travelled to different parts of the country, including the capital Antananarivo. Therefore, the overall risk at the national level is high. The overall regional risk is moderate due to frequent flights to neighbouring Indian Ocean islands. The global risk is low.
The last major urban outbreak of plague in the United States occurred in 1924-25 in Los Angeles. Since then, only scattered cases have been reported, with about 7-15 cases each year in the U.S..
According to the CDC: Between 1,000 and 2,000 cases each year are reported to the World Health Organization (WHO), though the true number is likely much higher.
I confess to having a particular interest in Plague, which stems from my working as a paramedic in Phoenix, Arizona where Bubonic plague cases are still occasionally found, and my reading – around the age of 11 – of James Leasor’s The Plague and The Fire which recounts two incredible years in London’s history (1665-1666) - which began with the Great plague, and ended with the Fire of London.
A fascinating read (if you can find a copy) for both history and epidemic aficionados.
