A report published in the August 1 issue of Pediatrics presents three possible cases of HIV transmission from caregivers to children by premastication, or prechewing, of food. This is the first report that premastication may lead to HIV infection.

Premastication is sometimes done to soften food for infants with few teeth or who are just starting to eat solid food. In each of the three cases presented in the study, the caregivers were HIV positive and were known to have prechewed food for the children. All three children had previously tested negative for HIV.

Although the cases do not definitively show that premastication was the method of transmission, researchers felt the possibility was strong enough to warn caregivers of the potential risk. “These cases do not provide definitive evidence,” said the authors of the article in email correspondence, “but they are persuasive enough that we feel compelled to investigate further pre-chewing as an under-recognized mode of transmission and to not wait to make recommendations that might reduce HIV transmission pending further research.”

In two of the cases, the children’s mothers were HIV positive but had not breastfed, consistent with the Centers for Disease Control’s (CDC) guidelines for HIV-positive mothers. After developing symptoms, both children were found to be infected with their mothers’ strains of HIV, despite previously testing negative.

In a third case, a child whose mother was not infected with HIV tested positive after being fed premasticated food by a great-aunt with HIV. Since the great-aunt was deceased at the time of the study, the viral strain from her HIV-positive partner was tested and compared to the child’s. The strain was not a close match, casting doubt on the method of transmission; however, no other obvious sources of HIV infection could be found.

Although there is no evidence that HIV can be passed through saliva, in this case two of the three caregivers were known to have had bleeding gums during the period they were prechewing food for the children. Researchers suspect this blood may be the source of HIV infection, and that the virus passed either through mucous membranes in the children’s mouths or through wounds in their mouths or digestive tracts from teething or illness. Additionally, in two of the three cases, the caregivers had high viral loads during premastication, which likely increased the risk of passing on HIV since more copies of the virus would have been present in the caregivers’ blood.

As a result of these possible cases of transmission of HIV by premastication, researchers are reviewing previous cases in which HIV-negative children later tested positive for HIV. “The CDC is in the midst of planning additional efforts to evaluate whether prechewing can be identified as a risk factor for transmission among other perinatally HIV-exposed infants who were previously ruled out for HIV infection and then presented with a late case of HIV-infection, “ said the authors of the study. In the meantime, the CDC recommends that HIV-infected caregivers not prechew food for infants.

The results of this study were first reported in February 2008 at the Conference on Retroviruses and Opportunistic Infections in Boston. For more information, please see the abstract in the journal Pediatrics or the press release at the Web site for St. Jude Children’s Research Hospital.