As a child, I was fascinated by a scar on my grandfather’s cheek. “How’d you get that?” I asked, touching the shallow depression as we settled into a comfortable chair to read a book.
“Where I grew up, everyone had a scar like that,” replied my grandfather, a native of southern Turkey. “First a fly would bite, then you got a sore. After a few months, the skin healed, and you never got the sore again.”
Twenty-five years later, as a researcher in Boston, I learned that my grandfather, with no science education, had grasped the biology and immunology of that sore surprisingly well. But I’m getting ahead of my story.
Kabul, Afghanistan, 2000. To escape the heat, Majeeba and Naieda Fazly flopped down on a striped mattress in the large, open-air balcony of the family home they had not seen for almost a decade.
Seven years earlier the Fazly family had suffered a blow. Mr. Fazly, 58, died of a heart attack, leaving behind a widow and 11 daughters. Only one good thing came of the tragedy. Lacking a male protector in a harshly conservative society, the Fazly women were eligible for international asylum. For several years they waited in Pakistan. Finally, the family was granted refugee status, and they returned to Kabul one last time before leaving forever.
Majeeba and Naieda were the youngest Fazly daughters and mere schoolgirls when they left Kabul for the first time in the early 1990s. Things were bad enough then. But now the streets were filled with trash, mangy dogs, and loud men with beards. And insects. Majeeba and Naieda had never seen so many sand flies in the city. Even in the covered sleeping porch, their bites were incessant.
A year later in Los Angeles, that memory of sand flies was the final clue to their diagnosis. Why? On their hands and forearms, both girls had fleshy, crusted ulcers. Just like the ulcer my grandfather once described.
In one stage of its life cycle, the parasite Leishmania swims freely in the saliva of the sand fly, propelled by its tail, or flagellum.
In some parts of Afghanistan, leishmaniasis has become so common that it is nicknamed “little sister.” In Kabul alone, some 200,000 people are thought to be infected. To curtail transmission, the World Health Organization is trying to distribute medicine and bed netting to patients.
Leishmaniasis is a protozoan infection transmitted by the bite of a sand fly. Protozoa are single-celled microbes that can develop exotic shapes and accessories: amoebas with crawling pseudopods, ciliates bristling with hairs, and flagellates sporting wavy antennae.
Leishmania assume two shapes during their life cycle. In the first stage, they take the shape of a flagellate that multiplies in the sand fly’s gut and eventually swims free in sand fly saliva. In the second stage, found exclusively in humans and animals, they lose their tails and become ovoid bull’s-eyes inhabiting immune cells called macrophages. The cycle starts anew when a virgin sand fly siphons parasitized macrophages from a skin ulcer or blood. During the next several days, the ovals morph back into creatures with tails, replicate in the sand fly’s gut, and finally migrate to the fly’s proboscis, ready to enter their next mammalian host.
The earliest descriptions of skin ulcers containing microscopic bull’s-eyes can be found in medical journals from the late 1800s. Then, in 1903, a Scottish army pathologist named Leishman described the same bull’s-eye pattern in cells taken from the spleen of a soldier who died after trying to fight off a fever for seven months while stationed at Dum Dum, outside Calcutta. The 23-year-old recruit, Private J. B. of the Second Royal Irish Rifles, became the first-ever reported case of a distinct strain of Leishmania that invades blood, bone marrow, and internal organs. Today the disease is known as visceral leishmaniasis. While people can recover without treatment from leishmaniasis that affects only the skin, untreated visceral leishmaniasis is still fatal.
Following Leishman’s discovery, names like “dum dum fever” and “kala azar” (both referring to visceral leishmaniasis) and “Baghdad boil,” “Biskra button,” “Aleppo evil,” and “oriental sore” became synonyms for subtypes of Old World leishmaniasis. On the other side of the globe, “uta,” “bay sore,” and “forest yaws” were linked with New World leishmaniasis of the skin. In time, even the scalloped scar that followed leishmaniasis of the outer ear acquired its own nickname. Because this ragged defect was common in Latin American men who harvested chicle for making chewing gum, it was called “chiclero’s ulcer.”