One often overlooked alternative feeding option is to use the mother’s own expressed breast milk once it has been heated to kill HIV. Heat treating expressed milk could prove safer than formula feeding in many settings where there is no reliable access to clean drinking water or a consistent supply of formula.
But there are problems with the two techniques — boiling and Holder pasteurisation — listed by WHO infant feeding resources. Boiling breast milk directly causes significant nutritional damage to it. Holder pasteurisation, on the other hand, is a low temperature slow heating method that has been reported to inactivate HIV while maintaining most of the milk’s nutritional properties. The method involves heating the milk to 62.5 degrees Celsius for 30 minutes and has been used in breast milk banks. But this isn’t a simple method that most women can do in their own homes since it requires temperature gauges and timing devices that simply aren’t available in most at-risk communities.
However, several studies at the World AIDS Conference reported that a new pasteurisation technique, flash heating, could be a practical method that mothers could perform on their own stoves or over a fire.
According to Kiersten Israel-Ballard, a doctoral student at the University of California, Berkeley, the method is based upon flash pasteurisation, a technique that involves heating at 72 degrees for only 15 seconds, which is used in commercial food science because it protects the nutrients while killing pathogens more effectively than Holder pasteurisation.
In the modified flash-heating breast milk technique, mothers wash their hands with soap and water and then manually express 75-150mL of breast milk into a sterile jar such as a peanut butter, jam, or honey jar — something that a mother would already have in her home. The jar is then placed in a simple aluminium pan containing around half a litre of water. The water and the jar of milk are then heated together over very high heat. When the water — not the milk — reaches 100 degrees and is therefore at a visible rolling boil, the milk is immediately removed from the water and allowed to cool.
When testing this method, Israel-Ballard and colleagues monitored the temperature of the milk and water in 15 second intervals and found that the breast milk typically reached a peak temperature of 72.9 degrees Celsius.
So far, several studies have evaluated the safety, effectiveness and acceptability of the method. Previously, pilot safety studies found that the flash heat method was capable of inactivating HIV in spiked breast milk samples from healthy mothers while retaining most of the milk’s nutritional and anti-microbial properties.
“Inactivating HIV is really just one of the issues in maintaining the safety of the breast milk,” said Israel-Ballard. In one study, presented as a poster at the conference, flash heat was capable of destroying any type of contaminant that was in the milk and destroyed the growth of any such microbes for up to eight hours after flash heating when stored at room temperature (23 Celsius). In contrast, there was substantial bacterial growth (including E.coli and S. aureus) by 8 hours in unheated breast milk controls (Israel-Ballard). She also noted that the treated breast milk can be frozen and thawed once, but only once (the thawing process is destructive to milk products).
The objective of the other study Israel-Ballard presented was to confirm that flash heating was also capable of inactivating HIV in naturally infected breast milk samples from HIV positive mothers. The study recruited 84 HIV-positive lactating mothers at a PMTCT clinic in Durban, South Africa. These women provided 94 breast milk samples which were immediately placed in an ice water bath and transferred to the laboratory. 50 ml of the breast milk was aloquoted to the flash heated and the remaining volume used as a unheated control.
Only about 31% of the mothers had detectable HIV in their breast milk. After controlling for other maternal characteristics, detectable breast milk viral load was significantly associated with low CD4 counts, increased likelihood of vitamin use and lower volumes of breast milk expressed (which is possibly a sign of mixed feeding or weaning).
30 of the 98 breast milk samples collected had detectable HIV. To determine the impact of flash heat on breast milk viral load, the unheated and flash heated aliquots of these 30 samples. The samples had a mean (sd) value of 8,078 (15,154) copies/mL; a median value of 1,895 copies/mL; and a range from 617 to 65,101 copies/mL.
After flash-heating, none of the samples showed detectable levels of HIV.
Israel-Ballard noted a number of limitations of the study, for example, the ExaVir RT assay used in the study is limited to detection of cell free virus only. Cell-free virus refers to "free-floating" virus or the parts of the virus not associated with a cell. Cell-associated virus refers to HIV that is inside a cell, and Israel-Ballard noted, “there has been data that has shown that cell-associated HIV could be the culprit for more of the transmission to the infant. We are very much concerned with this. Our virologist and our food scientist hypothesised that cell associated-infectivity would be destroyed along with the cell [by flash-heating]. Our preliminary data is promising with the cell-associated virus that we have been looking at, and we will be exploring this further.”
She also noted that additional research is needed to determine if variations in milk, water volumes, jar or pan size, shapes, heating source maybe even altitude would impact the effectiveness of flash heat. “We begun to address these issues in several field conditions and we currently confirming the nutritional, immunological and anti-microbial safety.”
“We have confirmatory data where we actually spiked the heating milk with high concentrations of E. coli and Staph. aureus to then see if, even after heating, if the milk were to be contaminated, are the antimicrobial properties still active. Because in raw unheated breast milk, the breast milk is like live tissue. It is antiviral, it is antimicrobial. These data are also very promising and we hope to expand upon this soon,” she said.
If nutritional safety and anti-HIV activity is confirmed, Israel-Ballard believes that flash heat should be included in comprehensive infant feeding counselling.
However, the practice may not be acceptable in every culture. Israel-Ballard shared this concern and said that one of the first studies that they did was in Zimbabwe where they found that the majority of participants felt that manually expressing and heat treating breast milk could be a potentially acceptable option — given that support was provided and that the safety could be confirmed. However, during the PATH Symposia, Dr. Tavengwa reported that another group of Zimbabwean mothers said that flash-heating would not be “culturally acceptable.” This indicates, at the very least, that there would have to be significant efforts to educate and reassure mothers about the process.
But it may be possible for heat treated breast milk to be used from birth (and this should be clinically evaluated given the high mortality rates reported on formula). However, Israel-Ballard believes that “it may be most feasible during times of high risk, such as mastitis and perhaps more practically during or after abrupt weaning. There are risks from the sudden onset of complimentary foods without the immune protection from breast milk. There is also the lack of adequate nutrition available that could result in malnutrition and soberingly, there is the recent data confirming the significant increase in breast milk viral load during the weaning period, suggesting that if a mother were to breast feed during this time, the risk of transmission would actually be increased.
“Perhaps heat treated breast milk could be used during this time and could be viewed as another complimentary food — one that is HIV-free, nutritious, affordable and available.”