Using antiretroviral (ARV) therapy to restore the immune system may substantially reduce the risk of malaria in countries where both HIV and malaria are endemic, according to new data presented Tuesday, July 21, at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town.

HIV and malaria can breed severe combined epidemics. It has been well documented that malaria, a protozoal infection transmitted via the bites of infected mosquitoes, boosts a person’s HIV viral load. Similarly, people living with HIV appear to be more vulnerable to the parasite Plasmodium and to severe disease.

Malaria is endemic throughout Africa and southern Asia, regions with high HIV rates. Yet little is known regarding the effects of ARV therapy on the incidence of malaria and its risk factors.

To explore this important question, Ronald Kasirye, MD, of the UVRI Uganda Research Unit on AIDS in Entebbe and his colleagues analyzed data involving 1,020 people living with HIV enrolled at the Entebbe research unit participating in the large Development of Antiretroviral Therapy for Africa (DART) trial.

Kasirye’s group tracked DART participants for four years after they began therapy, evaluating any fever-inducing illness for possible malaria as well as for other possible infectious illnesses.

In total, 524 (51 percent) patients experienced at least one episode of malaria. The incidence—new infection rate—of malaria fell with each year of ARV therapy use, from 59 percent after one year of treatment, to 48 percent after two years, 26 percent after three years and 16 percent beyond three years.

Statistical analyses conducted by Kasirye’s group determined that a lower CD4 count—notably fewer than 10 cells per cubic millimeter—when starting ARV therapy independently raised the risk of a new malaria diagnosis.

For Kasirye, the implications of this study are clear. The indirect effect of ARV therapy in combination with other control measures could help reduce disease and death caused by HIV infection and malaria.