In mid-nineteenth century Algeria, a French bishop sought to share the Gospel among the local Africans living in his diocese by forming a community that adopted the traditional dress in Algiers -- a white cassock with a red fez.

One hundred and fifty years later, the Missionaries of Africa, commonly called the "White Fathers" for their distinctive attire, have grown to have more than 1,500 vocations in 22 African countries -- 95 percent of which come from Africa.

Pope Francis welcomed members of the Missionaries of Africa and Missionary Sisters of Our Lady of Africa to the Vatican's Apostolic Palace Friday, and encouraged them to continue their mission on their 150th anniversary of their community's founding.

"It is always for Him, with Him and in Him that the mission is lived. Therefore, I encourage you to keep your eyes fixed on Jesus Christ, so as never to forget that the true missionary is above all a disciple," Pope Francis told the missionaries Feb. 8.

Founded by Cardinal Charles Lavigerie of Algiers in 1868, the White Fathers went on to evangelize in sub-Saharan Africa. Their priests notably brought Catholicism to Uganda, catechizing and baptizing St. Charles Lwanga and his 22 companion martyrs in the 1880s.

Today the White Fathers work to provide clean for orphanages in Tanzania, education for women in Burkina Faso, mental trauma aid for refugees in Burundi, and healing for victims of human trafficking in Kenya. They continue to be known for their dialogue with Muslim communities in Africa.

Pope Francis thanked the White Fathers and Sisters "in particular for the work you have already done in favor of dialogue with Islam, with our Muslim sisters and brothers."

"May the Spirit make you builders of bridges among men. Where the Lord has sent you, may you help to grow a culture of encounter, be at the service of a dialogue that, while respecting differences, can draw wealth from the diversity of others," he said.

The pope commented on the community founder's zeal for abolishing slavery.

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Called the "the apostle of the slaves of all Africa," Cardinal Lavigerie was an outspoken opponent of the European slave trade in the 19th century. He traveled around Europe campaigning against the practice of slavery in Africa and elsewhere.

Today the White Fathers continue to fight slavery in the form of human trafficking with the establishment of the "Human Trafficking Rescue Center" in Ngong, Kenya.

"In the wake of Cardinal Lavigerie, you are called to sow hope, fighting against all today's forms of slavery; making you close of the little ones and the poor, of those who wait, in the peripheries of our society, to be recognized in their dignity, to be welcomed, protected, raised, accompanied, promoted and integrated," Pope Francis said.

"With this hope, I entrust you to the Lord, through the intercession of the Virgin Mary, Our Lady of Africa," he added.