Northern Nigeria has seen signs of a resurgence of polio cases, threatening to erase gains that had led to the near eradication of the disease in the country, UNICEF officials said Tuesday. "In recent times, we have made some commendable strides in our commitment to kick polio out of Nigeria...," said deputy head of the UN children's fund for Nigeria, Jacques Boyer. "However, there are challenges in sustaining the progress made in polio eradication as Nigeria is currently experiencing new polio outbreaks." Polio cases in Nigeria dropped to 21 in 2010 from a staggering 338 cases in 2009. But "as at this month, 20 cases of wild polio virus were reported in six states" in the north, Boyer told a gathering of traditional and religious leaders in the northern city of Kano. "It is clear from the figures that we are beginning to lose some of the grounds covered in our polio eradication efforts." The World Health Organisation has pledged to stop polio transmission by the end of the year and to stamp out the crippling virus worldwide by 2012. "We have come too far in our fight against polio to contemplate a relapse. Complacency is probably the biggest danger that might jeopardise success in eradicating polio," Boyer told the community leaders. The change has been blamed on a decrease in vaccinations for the highly contagious virus, which has been a problem in the past in Nigeria. Between 2003 and 2004, the Nigerian state of Kano suspended polio immunisation for 13 months following allegations by some Muslim clerics that the virus was laced with substances that could render girls infertile. They alleged it was part of a US-led Western plot to depopulate Africa, and the resistance to vaccines made Kano the epicentre of the transmission of the crippling wild polio virus. Such conspiracy theories prompted immunisation and sensitisation campaigns by health officials and international donors in collaboration with local political leaders, traditional chiefs and clerics. As a result, Kano recorded only one polio case in 2010, with five recorded so far this year, according to Boyer. Danjuma Al-Mustapha, UNICEF monitoring and evaluation officer, said the apparent current drop off in vaccinations appeared to be due more to a lack of public health facilities than conspiracy theories. He said parents are also frustrated by government's insistence they immunise their children against polio while drugs for more rampant diseases like malaria and cholera are lacking in government-run hospitals.