The Forgotten Disease of the Andes

The Andes range forms the backbone of the South American continent. It is bounded on one side by the endless Amazonian rainforest and the interminable plains of Argentina and on the other by the semi-arid coastal regions of Chile and Peru to the south and by Ecuador and Colombia to the north. Tourists do not venture into the high valleys of the Andes—vibrant green landscapes bordered by incredible icy plateaus—as all one can find there are simple people, hats made from woven palm, herds of free-roaming black pigs, small chacras or farms, mining towns, and wide-eyed children who smile overjoyed at the gift of a humble lollipop. And it is here in these valleys that we find  Carrión’s disease (Bartonellosis), an infectious disease that is particularly prevalent in Peru but is also found in parts of Ecuador and southern Colombia.

The history of Carrión’s disease, which was described by the chroniclers of Pizarro’s army of conquistadores, is a tale told in black and white, as old as the pre-Incan huaco figurines that display its symptoms, fascinating but unknown. The story includes such dramatic episodes as the death of 70% of the workers who laid the railway track between Lima and La Oroya. It also features examples of heroism, or perhaps folly, such as the story of Daniel Alcides Carrión, the medical student who died after he asked a colleague to inoculate him with infected material to establish the relationship between the acute and chronic forms of the disease that was later named in his honour. And chance has also intervened: in 1913 the etymologist Charles Townsend fortuitously discovered the transmitting vector after one of his assistants was bitten by a local species of sand fly called the titira.

Carrión disease can have three different presentations: a febrile acute phase known as Oroya fever that mainly affects people who have had no previous contact with the pathogen; an eruptive phase, affecting those who have had some prior exposure and have developed a certain immunity, which takes the form of skin lesions known as “Peruvian warts”; and an asymptomatic form found in carriers, people who are infected but exhibit no clinical signs or symptoms. Carriers have often had Oroya fever and have been clinically cured but are still infected with the bacteria.

Carrión disease can have three different presentations: a febrile acute phase known as Oroya fever that mainly affects people who have had no previous contact with the pathogen; an eruptive phase, affecting those who have had some prior exposure and have developed a certain immunity, which takes the form of skin lesions known as “Peruvian warts”; and an asymptomatic form found in carriers, people who are infected but exhibit no clinical signs or symptoms. Carriers have often had Oroya fever and have been clinically cured but are still infected with the bacteria.

The disease tends to affect the most disadvantaged populations and is found particularly in poor communities. Even in areas where it is endemic, prevalence is higher in the more impoverished sectors of the population, among those who live on the outskirts of urban areas in almost rural areas—places where town and country come together and intertwine. Moreover, even within these communities, its greatest impact is on the most vulnerable members, such as children and pregnant women.

The truth is that nobody knows for sure how many people are affected. Cases often remain unreported. The condition is frequently misdiagnosed in small clinics equipped with little more than a microscope, a small centrifuge, and a box with a light bulb for drying slides. And nor is it a disease to be taken lightly. The fatality rate is over 40% among patients in the acute phase who do not receive treatment. In fact, the acute phase of Carrión’s disease has the unhappy honour of being the most deadly bacterial infection in the world. Left untreated, it is more deadly than the plague that devastated Europe in the Middle Ages, although fortunately today it is easily treatable with antibiotics.

It is a potentially eradicable disease since there is no known non-human reservoir. However, few people are aware of the disease outside the affected areas. It is not discussed and does not figure on international research agendas. It is not even included in the list of neglected diseases recognised by the World Health Organisation. Despite the fact that Carrión’s disease meets nearly all the criteria for inclusion on that list, it paradoxically lacks the principal characteristic: notoriety. It is, as yet, too little known.

Photos: Sandra Martínez & Claudia Gomes