Nigerians make up more than half of Italy's 19,000 to 25,000 street prostitutes
Many flock to Turin in wealthy northern Italy, which has had strong business and trade links with Nigeria since the 1980s. Today, there is a large Nigerian community.
Women are typically recruited in their late teens or early 20s by a friend or relative in a poor Nigerian town like Benin City. Most of them know they will work as prostitutes.
They are flown to Turin or smuggled overland via North Africa, then bought by a female pimp, or "madam", who tells them they have to pay off up to €50 000 in debt to regain their freedom.
With oral sex costing as little as €5 on a bad day, this can take a while.
Some prostitutes even become madams themselves:
Madams are increasingly recruiting in small villages rather than towns, targeting girls who are more submissive, uneducated and often unaware of even basic health issues.
Some women do succeed in paying off the debt, become madams themselves and wow people back home with their wealth. Others are picked up by police and deported, returning home with the stigma of having failed to make their families rich.
A few come forward to denounce their madams and enter a special witness protection programme; prostitution is not illegal in Italy, but pimping and human trafficking are.
In 1998, Italy became the only European country to offer migrant prostitutes a residence permit if they file charges against their traffickers. That helped the number of charges filed by Nigerian women jump to 111 in 2000, from 27 in 1997.
There are still plenty of reasons for Nigerian prostitutes not to turn to the police: fear of witchcraft, fear that loved ones back home will be harmed, fear of punishments such as being burned with a hot clothes iron.
For the campaigners, it is also hard to tell the exploited from the exploiters, making it dangerous to give the women in the street direct advice on denouncing their masters.
Amid a cluster of Nigerians with corsets and bulging cleavages, a short, cross-eyed woman with a chipped tooth and a mop of frizzy, bleached hair recalls her own experience with violent clients.
On another road, a 28-year-old wipes her running nose with a tissue as she fondly talks about her children back in Nigeria.
Saporta and Baldo suspect both women are madams.
"Some of the girls buy another girl even as they're still paying off their debt," Saporta says.
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