# Prevalence of Mouse Mammary Tumor Virus-Like Virus in Breast Milk and Associated Factors of Exposure Among Healthy Nursing Women in Morocco

## TL;DR

This study found that nearly half of breast milk samples from healthy nursing women in Morocco contained a virus similar to the mouse mammary tumor virus, possibly linked to henna use.

## Contribution

The study is the first to report a potential link between henna use and MMTV-like virus presence in breast milk.

## Key findings

- MMTV-like virus was detected in 45.5% of breast milk samples from healthy nursing women in Morocco.
- Use of henna was significantly associated with the presence of MMTV-like virus in breast milk.
- Possible contamination of henna by mouse urine and feces during storage is suggested as a transmission route.

## Abstract

Background: The mouse mammary tumor virus (MMTV) has been identified as potentially oncogenic, and its presence in milk was reported and discussed. However, with respect to breast cancer etiology, the transmission routes for these viruses are not known. In this context, the objective of this study is to assess the presence of MMTV-like virus in breast milk and to explore the associated factors of its presence among healthy lactating women in Morocco.

Methods: In this prospective study, milk samples were collected from 44 lactating women recruited from the Souissi Maternity Hospital of Rabat in Morocco. MMTV-like DNA was identified by polymerase chain reaction amplification using specific primers targeting the env gene.

Results: The prevalence of the MMTV-like virus was 45.5% (20/44). Statistical analysis revealed a significant association with the use of henna. It seems that it increases the risk of the presence of MMTV-like virus in breast milk. The hypothesis could be the possible contamination of henna sold in bulk in local markets by urine and feces of mice during storage.

Conclusion: Nevertheless, these results need to be confirmed by multicenter studies to thoroughly investigate the impact of other factors and the potential contamination of henna with the virus through urine and feces of mice during storage.