Far from Lima, the coastal capital of Peru, where a thriving middle-class Jewish community of roughly 3,000 Ashkenazim is anchored by a web of institutions, a tiny grouping of Jews in the rainforest is just about clinging on.

In Iquitos, a remote jungle city of more than 400,000 people that is unreachable by road, one of the last Jewish communities in the vast Amazon basin is under threat - despite an inspirational rebirth only a few years ago.

"It's saddening; the community is getting smaller and smaller," Rabbi Rubén Saferstein, who has led hundreds of conversions in Iquitos in recent years, said. "Only a small nucleus will live on."

Today, there are 100 to 150 Jews in Iquitos, some of whom regularly gather on Jirón Próspero Street for impassioned Shabbat and holiday services.

Most of the Jews are descendants of Sephardic traders from Morocco and other parts of the diaspora, including England and France. They joined an emigration wave to the Peruvian jungle more than a century ago in the hope of becoming rich during a rubber boom that metamorphosed Iquitos; in just a few years, it was turned from an outpost into a prosperous city.

The Jewish immigrants were chiefly men who married Amazonian women courted during expeditions into the rainforest. Though their children were rarely ever Jewish according to halachah, they would often seek to raise families according to Jewish traditions and values.

But the rubber boom lasted just three decades. As the industry collapsed in the 1920s, some Jews left for Lima. Others returned home. And against this backdrop, many of those that stayed in the city turned to Catholicism.

A decaying cemetery endured as one of the only vestiges of Iquitos' once flourishing Jewry.

During the 1990s, however, there was a reawakening. The great-grandchildren of the immigrant traders, with surnames like Levy and Ben-Haim, were keen to reconnect with their Jewish ancestry. They began to congregate, observing ceremonies as best as they could and reviving customs that had become hazy.

Their story reflects other such Jewish renaissances, such as those of the so-called crypto-Jews in southern United States and northern Mexico, and the Bene Israel in India.

Soon, members of the Iquitos community decided to cement their progress by converting. But the conversions would emerge as a double-edged sword - while they ensured the reawakening would not be fleeting, they also sparked a modern-day exodus.

Rabbi Guillermo Bronstein, a prominent leader of Lima's Jewish community, was enlisted to organise the first conversions. It was not easy.

Rabbi Bronstein, an Argentine, recalled the difficulties of directing the efforts in such an isolated corner of the world: sending Hebrew texts by post from Lima; the impossibility of finding a mohel, referring instead to a non-Jewish physician; and the troubles of establishing an official kehila.

"It was all so slow that it took about 10 years to finalise the first conversions in 2003," Rabbi Bronstein said, adding: "but they were already insufflated with Jewishness." He was referring to the community's residual spiritual connection to their forefathers.

Having reclaimed their Jewish identity, however, the group of converts did not stay long in Iquitos, making aliyah soon after.

A pattern had emerged. Following the next two waves of conversions, hundreds more converts moved to Israel, mostly settling in Ramla, between Jerusalem and Tel Aviv.

Rabbi Saferstein, an Argentine who has travelled between Buenos Aires and Iquitos regularly over the past decade, led what might be the final set of conversions.

"The motivation is not there anymore," he said, recalling with enthusiasm his forays into smaller conurbations away from Iquitos, like Pucallpa and Tarapoto, where he helped descendants of Jews to rekindle their faded heritage.

And, so, for the handful of Jews that stayed behind in Iquitos, the future is uncertain. Dozens of them still gather for Shabbat in the makeshift shul annexed to Jorge Abramovitz's mattress shop on Jirón Próspero Street, where a flag of Israel drapes from the back wall.

The Lima community has been loathe to embrace the Iquitos Jews - some of whom have lower-end jobs, like auto-rickshaw drivers - tending to view them as little more than a curiosity.

However, the quirky services at the back of Mr Abramovitz's shop should in no way be considered inferior to those at traditional shuls in Lima, Rabbi Saferstein said.

He pointed to "the devotion of the congregation… the way they sing a capella," adding: "Their Kabbalat Shabbat is the most emotive I've ever attended."

Now there is latent hope of a secondary resurgence.

"There are dozens of Levys and Ben Haims still out in the jungle," Rabbi Saferstein said. "You just have to find them."