It is 6pm on a Monday night on a highway outside Milan. The thermometer on the car dashboard says it is two degrees below zero, but every few metres our headlights pick out figures waiting along the roadside, some hunched with their palms splayed over makeshift fires. Silvio Berlusconi outlawed soliciting on the street three years ago, but the estimated 20,000 Nigerian women who work as prostitutes in Italy are easy to find. Even in winter, there is no shortage of customers.
This is one of hundreds of highways throughout Europe where Nigeria's trafficking victims are forced to work. We could be in Barcelona or Madrid, Paris or Berlin, Glasgow or London. There are 100,000 trafficked Nigerians in Europe, and 80 per cent come from Edo – a southern state that is home to only three per cent of Nigeria's population. It is the trafficking capital of Africa, and home of the traditional West African religion they call juju.
The condom-strewn lay-by near Bergamo where Rita picks up clients is a far cry from the Europe she imagined five years ago when traffickers approached her in Edo. "I was happy that I was going to Europe to feed my family," explains Rita, 27. "I didn't know it would turn out to be like this." She now sleeps with about 10 men a day, seven days a week, for €20 (£17.50) a time. She will work even if she feels ill, even if she has her period, even though she has been badly beaten in the past.
Rita says she has no choice but to carry on working. Before she left Nigeria, she swore an oath of loyalty to her traffickers in a traditional religious ritual, a practice I was investigating for Channel 4's Unreported World programme. She promised to pay back the cost of her transportation to Europe and offered up her soul as collateral for the debt. When she arrived in Italy, she was told she owed her traffickers €50,000 (£44,000), as well as extortionate living costs, including €300 a month in "rent" for the right to solicit from her particular patch. "I can't escape this unless I pay," she says. "Africans have very strong charms that can destroy someone in the twinkle of an eye."
Nigeria's human traffickers are using black magic to trap thousands of women like Rita into a life of sex slavery in Europe. Eastern European gangs use violence to coerce the women they transport, but the "madams" at the top of the Nigerian trafficking chain don't need muscle – they have juju on their side. It is a form of ritualised extortion that allows Nigerian women to be both perpetrators and victims of the exploitation.
Three thousand miles away in the small Edo village of Ewhoini, I meet 23-year-old Vivian Peter – intelligent, beautiful and full of aspirations that are hard to realise in rural Nigeria. The £2 a day she earns selling tomatoes at the market isn't enough to put her younger brothers and sisters through school, and buy a home where she can live with her boyfriend, Elonel. But he says he has the answer to their problems: he is arranging for Vivian to go and work for someone he says is his sister in Italy.
Paved roads and reliable electricity may not have reached this part of rural Nigeria, but the myth of the "Italos" – the women who have made a fortune in Italy – has permeated every household. It is an open secret that the Italos earn their money by selling sex, and there is no shame in it – Nigerian women who travel are stigmatised only if they return home penniless. But many do, often beaten and HIV-positive, and are rejected by their families.
Vivian doesn't know exactly where she will be taken, or how much she will owe her traffickers, but she imagines her debt will be paid within a few months. "I won't have any idea until I get there," she tells me. Her boyfriend has no qualms about sending her to sell sex on Italy's streets. "A lot of people do it over there," Elonel, 27, says matter-of-factly, "I'm not going to stop her." All the arrangements are in place: he has bought her plane ticket to Rome and booked her in to see Doctor Stanley, the local juju priest. He says the ritual will "help her out" and bring her luck in Italy. Juju has been practised in West Africa for centuries, and it would be hard to find anyone in Edo who is prepared to say they don't fear it. Believers say invisible spirits govern the earth and control every aspect of human existence, and nothing can be hidden from their scrutiny. The spirits can be called on to protect people, but they can also destroy them.
"If she breaks the promise she makes at my shrine, we need blood from her," Dr Stanley tells me on the morning of Vivian's ritual. "I can use my power to destroy anything I want. I can throw any type of sickness to a person, whether cancer or stroke." He boasts that "uncountable" trafficked women have sworn oaths at his shrine. I ask if he feels responsible for compelling so many to a life of prostitution. He fixes me with a stern gaze. "When you promise this is what you will do, unfailingly you must do it."
Tall and muscular, with crimson robes adorned with talismans, Dr Stanley strikes an imposing figure next to Vivian's small frame. While not officially part of the trafficking chain, he provides the most important component: the oath that makes women compliant. It is a lucrative source of business for him. He is making £120 from today's ritual – a serious amount of money here.
The shrine is filled with juju fetishes: rattles, idols made out of feathers, bones and sea shells, crucibles filled with bright powders. Dr Stanley commands Vivian to undress and wash in the hut outside the shrine, and when she emerges he blows chalk dust over her body and smears clay over her forehead, marking her out so the spirits can identify the soul that is being offered to them. Then he asks her to kneel before him to swear the oath. Elonel watches impassively, smoking a cigarette. The ritual over, Dr Stanley lifts Vivian to her feet. "I feel safe in his hands," she says, visibly relieved.
A few days later, in a bar an hour's drive away, Elonel says he is doing another piece of business: he claims his sister has found two other women to travel alongside Vivian, and he is arranging for them to swear their oaths tomorrow so they can all go and work for her in Italy. "When they get there, she will make money. A lot of money," he says blankly, "and if things are going well, they will send me money." Poverty has absolved him of any moral responsibility for the women he's trafficking, he says. "I don't have to feel bad. I need money."
Vivian has been outside Edo only once – when Elonel took her to Lagos to get her travel papers – but the myth of the Italos has convinced her she belongs in Italy. "I know it will be a better place for me," she says when we meet for the last time. I tell her about the women I saw at the roadside outside Milan, about the cold, the beatings, and the €50,000 debt that Rita is still paying off, five years on. "I don't think so. Mine won't be like that," Vivian frowns. "If you are hard-working, you won't suffer. I know how to plait hair. There are lots of things I know how to do," she insists. Then she pauses. "I've made up my mind that I will go there, and I must go there. I chose it."
Europe's trafficking statistics are made up of Edo women like Vivian who do not conform to the stereotype of passive "victims". It is the most determined and driven who fall prey to Nigeria's traffickers – those without dreams to exploit are left alone. No matter how strong these women might be, the juju oath leaves them manipulated, abused and utterly trapped. Without faith in ancient, traditional beliefs, this modern form of slavery would not exist. And without a thriving market for their services, no Nigerian woman would be trafficked to Europe in the first place.
An ancient African ritual
* Little is known about the origins of juju – a West African tradition which encompasses a range of rituals and supernatural entities from auras, spirits and ghosts, to magical properties believed to be bound to objects.
* It is not uncommon for Nigerians from all walks of life to carry amulets to ward off evil spirits and bad luck. But it is also believed that the powers of juju can be summoned and used only by a witch doctor. Contrary to popular belief, juju is not related to voodooism.
* Believers hold that juju can be used for 'good' purposes, such as curing ailments, but 'bad' juju can also be used to impose a host of misfortunes, such as madness, disease and death.
* Dried chameleons and chickens are often used in juju rituals.
Jenny Kleeman's film for 'Unreported World', called 'Nigeria: Sex, Lies and Black Magic', will be broadcast on Channel 4 tomorrow at 7.30pm. It can also be watched at channel4.com