"In other countries where MSF has started HIV/AIDS projects, people are banging at the door to get treatment," said Dr Pat Campbell, part of the MSF team. "Here it sometimes feels like we are begging patients to take drugs."

Mamay says he is 29, but he looks at least ten years older, with an already heavily lined face and a hesitant, laboured walk. He normally works on a smallholding, farming sorghum and sesame to support a wife and two year old son, but for the past 23 days he has been living in an MSF shelter 122 kilometres from home. He will have to stay there another week before he can finally leave and get back to harvesting his crops.

Mamay is being treated for kala azar, a disease virtually unknown in - and therefore ignored by - much of the world. Like the other two million people who contract kala azar each year, mainly in Sudan, Brazil and South Asia, he caught the disease when he was bitten by a sandfly carrying a parasite called Leishmania donovani.

Once inside the victim's body, the parasite multiplies and invades the immune system. The disease tends to develop in people living in poor and rural regions, especially those whose immune systems have already been weakened by malnutrition or other diseases, particularly HIV/AIDS. If left untreated, close to 95% of those who contract kala azar die.

Since 1997, MSF has been tackling the disease in the Ethiopian town of Humera, where the Ethiopian, Eritrean and Sudanese borders meet. It is a flourishing town which comes as something of a surprise at the end of the bumpy and sparsely populated road from the airport, some six hours away. The bustle of the market and noise from the bars contrasts sharply with the stillness of Eritrea, which lies on the far bank of the nearby river.

Because of a border dispute between the two countries, a 'no-go' zone is in place on the Eritrean side, monitored by two tall UN watchtowers looming over the water.

Kala azar treatment is painful and treatment is fairly undignified, involving a 30-day course of injections in the buttock. At 10am each morning, the main room of the MSF shelter is full of patients lying on their fronts and clutching their behinds, their faces contorted with pain. The drug in the syringe, sodium stibogluconate (SSG), was developed in the 1930s and, although it is still largely effective in Ethiopia, it is a daily dose of agony.

It is also toxic and on rare occasions it can actually cause sudden death. Nonetheless, it is currently the best treatment that doctors have available in the country.

The vast majority of the patients gritting their teeth each morning are male migrant workers who have come to Humera to find seasonal work on the huge cotton, sorghum and sesame farms in the surrounding countryside. With little money to spare, they often sleep outside on the bare earth in the fields and so are easy prey for sandflies.

"I came to Humera in a truck with many others from my village 400 kilometres away," explained Nagash Mula, on his third day of treatment. "There were no jobs in Tsalemt, my home town. I found work here quite easily. I did all sorts of things, from harvesting sesame to carrying stones for construction work. Sometimes I stayed at a house in town, and sometimes I just slept in the fields.

"I got ill about a month ago. I had fever and had leg cramp, and I felt very weak. At first I thought I had malaria but when I came to the hospital I was diagnosed with kala azar. Today is my third day of injections - they are really painful, but I'm getting used to it now."

Co-infection complications

Despite the painful injections, kala azar on its own is a relatively straightforward disease to treat. However, for people who have kala azar combined with HIV/AIDS it is unfortunately a different story.

"We think that about twenty percent of those with kala azar are co-infected with HIV," says Carolyn Gee, a British doctor working for MSF in Humera. "People who have kala azar on its own and are treated generally recover and never get the disease again. However, some patients either don't respond to the treatment, or they relapse repeatedly. That's a strong indication that they've got HIV as well."

The MSF project in Humera is the only programme in Ethiopia, and one of very few in the world, which is treating people co-infected with kala azar and HIV. As such, it is breaking new ground in terms of developing the best medical approach for tackling the problem. Kala azar, like HIV, attacks and weakens the immune system. This makes treating patients infected with both diseases complicated and there is still a huge amount to learn.

"For people with HIV, you use the CD4 count to decide when you are going to start them on anti-retroviral (ARV) treatment," explained Carolyn. "The CD4 count measures the strength of the immune system by counting the amount of T-lymphocytes, a type of white blood cell, in the blood."

"But patients with kala azar have a CD4 count which is low anyway so you might end up putting people on ARV treatment too early. It's a catch that you have to look out for. Generally, we treat the kala azar first, and try and wait before putting them on ARVs so that we can disentangle the effects of the kala azar and the effects of the HIV on the CD4 count.

"One of the harder problems is when you have people on ARVs who relapse with kala azar. The question is whether their CD4 count is dropping because their ARV drugs are no longer working, or because they are relapsing with kala azar. That's one of the trickiest things because we can't do viral load tests here."

There are also important issues related to the drugs available to treat patients suffering from both diseases. The first problem is that both SSG and one of the anti-retroviral drugs used to treat HIV can cause inflammation of the pancreas.

In addition, if patients relapse repeatedly with kala azar, eventually SSG may stop working. If this happens, they will need alternative treatment. Currently the only option is a quite toxic drug which has to be given very carefully in order to avoid damaging the patient's kidneys. The safer, less toxic version of the drug cannot be imported into Ethiopia because it is not yet registered in the country. MSF is pushing for registration, but it's a torturously bureaucratic process.

Stigma

In addition to the medical challenges of dealing with kala azar and HIV, there are striking social barriers to tackling AIDS in Humera. For a start, there is widespread discrimination against HIV positive people, which prevents many from wanting to be tested for the disease.

"I was told about the possibility of being tested for HIV, but I'm not sure I want to do it," says Mamay at the kala azar shelter. "I need to discuss it with my wife. Where we live, people don't want to have anything to do with you if they know you are HIV positive. Even your family refuse to be seen with you. People think that they can catch AIDS through breathing the same air as someone who is HIV positive, so they are very scared. If my wife agrees that I should be tested, then I might do it. But I'm doubtful at the moment."

Part of the problem is that people worry they will loose status and, importantly, business if they are even seen attending the HIV test centre.

"People are afraid of being isolated from the community," explained an HIV-positive MSF staff member who works as a 'peer educator', sharing his experiences with others. "Everybody in Humera town knows what HIV is and the ways it can be transmitted. But many people have come here to find work - agricultural workers, sex workers, people who run small businesses selling tea or bread at the market. If people see someone going to be tested for HIV it damages their business - no one wants to buy stuff at their shop anymore.

"People have seen AIDS patients become bedridden and die, so of course they are scared. Now things are changing slowly because people have seen the effect that treatment can have - they see people on ARV treatment getting better, which means that stigmatisation of HIV positive people is gradually decreasing. But there is still a long way to go - attitudes are changing in the town, but in the countryside discrimination is still strong."

One of the main challenges currently facing the MSF team is the large number of people who come to be tested, get a positive result,then disappear and do not seek medical treatment. In 2004, of the 7,000 people tested, 1,200 were found to be HIV positive. Only about half of these came to their first medical consultation, and only about 200 came to their third.

"In other countries where MSF has started HIV/AIDS projects, people are banging at the door to get treatment," said Dr Pat Campbell, part of the MSF team. "Here it sometimes feels like we are begging patients to take drugs. We don't yet have a good understanding of why this is: it could be because it is a very mobile population. It may also be because people don't want to accept their diagnosis or are afraid of the stigma of attending the clinic. In some cases, people may not show symptoms, in others they may feel so ill that they simply want to go home to die."

On the other hand, once those who seek treatment actually start taking ARV drugs, there is a strikingly low drop-out rate. This represents an unexpected success, since many had assumed that keeping marginalized migrant workers with a mobile lifestyle on treatment would be extremely difficult. In fact, it seems that the fact that they are strangers in town actually makes it more likely that they will stick with treatment, since they don not fear being stigmatised by their families and home communities.

As Nagash Mula explained, "I don't have any family here - they are 400 kilometres away. Two years ago, I got sick and was offered an HIV test, so I decided to go. I tested positive and now I am taking anti-retroviral treatment. It's going fine, but I don't know where I will live after I leave the MSF shelter later this month."

Sadly, the lack of social support for people like Nagash is an overwhelming problem and something too big for MSF to handle alone. Providing drugs is all very well, but what if the patients taking them do not have a place to sleep or anything to eat? How can they be expected to survive if they don't have a family willing to support them or a job?

A large refuge built by MSF and run through a local organisation provides those who have nowhere to go with short-term shelter and regular food. But it can only offer temporary respite from the harsh reality of the outside world - there are simply too many people in need of help. The enormous challenge now is to get the Ethiopian authorities is to engage with these issues and tackle them head on.