Miao et.al.
Breast milk transmission and involvement of mammary glands in tick-borne flavivirus infected mice. J Virol. 2024 Mar 19;98(3):e0170923. doi:10.1128/jvi.01709-23

Even though alimentary TBE virus infections have been known for more than 70 years, the exact mechanism of transmission of this virus is still unknown. There has not yet been conclusive evidence that breast feeding can result in an infection. It has been demonstrated that mother-to-child transmission of flaviviruses during breast-feeding is possible for Zika virus, and one instance of interhuman transmission of TBE virus has recently been reported (see Snapshot week 20/2022). By analyzing the closely related (attenuated) Langat virus (LGTV) in a mouse model using a bioluminescent NanoLuc (NLuc) LGTV reporter virus, the transmission of TBE virus by breast milk-feeding was investigated.

Compared to wild-type LGTV, NLuc-LGTV is less effective and slower in infecting mice via the intragastric route and other routes of infection (weight loss and mortality are delayed). In dams infected with NLuc-LGTV, the virus was detected in milk and mammary glands, and experimental data confirmed the infectiousness of milk from LGTV-infected dams and the possibility of LGTV transmission through consumption of contaminated milk.

Virus transmission from dams to pups through breastfeeding was shown, and a high mortality rate was observed among infected pups. It has been demonstrated that LGTV can cause an infection of the gastrointestinal tract. The virus spread through the intestinal M cells of Peyer’s patches, which transport the virus into the intestinal lymphoid tissue, where it is replicated.

As a result of their findings, the authors conclude that educating the public about the risks associated with non-pasteurized dairy products is crucial.

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