An IOM study has found that farm workers in South Africa's Limpopo and Mpumalanga provinces have the highest HIV prevalence among any working population in Southern Africa.

Conducted over three months (March to May 2010) on 23 commercial farms in the Malelane, Musina and Tzaneen areas, the Integrated Biological and Behavioural Surveillance Survey (IBBSS) involved 2810 farm workers who anonymously gave blood specimens for HIV testing.

The survey found that an average of 39.5 percent of farm workers who tested were HIV positive.  This is more than twice the UNAIDS estimated national prevalence for South Africa of 18.1 percent.

"This study has reported an extraordinarily high prevalence of HIV among farm workers on commercial farms.  I am not aware of any published literature in Southern Africa that has reported a higher prevalence than this," says Doctor Mark Colvin from Maromi Health Research, who led the survey.

HIV prevalence was significantly higher among female employees with almost half of the women (46.7%) testing positive compared to just under a third (30.9%) of the male workforce.

The Malelane site recorded the highest prevalence at district level, with nearly half the agricultural workforce (49.1%) testing HIV positive. This figure is much higher than the government's data on the district which puts the prevalence at 34.9 percent. Malelane shares borders with Mozambique and Swaziland, thus the farm worker population in the area is roughly 60 percent South African, 24 percent Mozambican and 14 percent Swazi.

The Musina site that borders Zimbabwe registered an HIV prevalence of 28.1 percent, nearly twice as high as the surrounding Vhembe district's HIV prevalence of 14.7 percent. This site comprises of mostly cross border migrants, with roughly 60 percent being Zimbabwean nationals and 38 percent South African.

Tzaneen recorded the lowest prevalence of 26.3 percent, although it's slightly higher than that of the general population in the district (25.2%). Its labour force was made up of mainly internal South African migrants.

The study could not pin-point a single factor causing this high rate of HIV infection on these farms but points instead to a combination of factors such as multiple and concurrent partnerships, transactional sex, irregular condom use, presence of Sexually Transmitted Infections (STIs) and/or TB and high levels of sexual violence.

"While new HIV infections among adults and young people have dropped nationally, it is very worrying that the epidemic remains shockingly high in the commercial agricultural sector.  Even more disturbing is the fact that no existing research can explain what is making the farm workers more vulnerable to HIV infection. More research is clearly needed," says Dr. Erick Ventura, IOM's Regional Coordinator for Migration Health in Southern Africa.

The report makes several recommendations including increasing farm worker access to healthcare; implementing prevention programmes that don't just raise awareness but also reduce transmission of the disease by HIV positive people; addressing gender norms which increase risky behaviour and vulnerability to HIV such as the belief that a man has to have multiple partners, as well as including both permanent and seasonal farm workers in workplace health and safety policies.

This study was conducted with support from the United States Agency for International Development (USAID), the President's Emergency Plan for AIDS Relief (PEPFAR) and the Swedish International Development Cooperation Agency (SIDA) in partnership with the Norwegian Ministry of Foreign Affairs (MFA).