1. Transmission is a key component of a pathogen's life history, but it is often difficult to obtain reliable ecological estimates of the dominant mode(s) of transmission and how host traits, such as sex, influence transmission dynamics.
2. Here, we have developed a robust system pairing the use of semi‐natural populations of house mice Mus musculus with modern molecular viral titering approaches to evaluate the transmission dynamics of Friend Virus Complex (FVC).
3. Semi‐natural populations were founded with female and male mice that were either ‘index’ (initially infected via intraperitoneal injection) or ‘contact’ (uninfected at the start of experiment). Three experimental population designs were implemented: female index only, male index only and both female and male index.
4. Utilizing these enclosures, we found male–male transmission to be the predominant mode of transmission, with low rates of horizontal female transmission and no evidence of vertical transmission. Additionally, contact males that became infected harbour higher titres than females while suffering a similar amount of spleen enlargement; this, paired with a strong correlation between titre and spleen size in males, and no correlation in females, indicates FVC viral dynamics differ between the sexes.
5. Lastly, natural transmission may be an impediment to FVC replication as infected contact animals have a lower viral titre than index animals. These results illuminate the complex life history of murine leukaemia viruses and demonstrate the important role of host sex on pathogen transmission dynamics.

中文翻译：

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鼠逆转录病毒的水平传播是由半自然环境中的雄性驱动的

1. 传播是病原体生命史的关键组成部分，但通常难以获得对主要传播方式以及宿主特征（例如性别）如何影响传播动态的可靠生态学估计。
2. 在这里，我们开发了一个健壮的系统，将家鼠半自然种群的使用与现代分子病毒滴定方法配对，以评估Friend Virus Complex（FVC）的传播动力学。
3. 用“索引”（最初通过腹膜内注射感染）或“接触”（实验开始时未感染）的雌性和雄性小鼠建立半自然种群。实施了三个实验人群设计：仅女性指数，仅男性指数以及女性和男性指数。
4. 利用这些围栏，我们发现男性-男性传播是主要的传播方式，水平女性传播率低，没有垂直传播的迹象。另外，被感染的接触的男性的滴度高于女性，同时脾脏肿胀程度也相似。这与男性的滴度和脾脏大小之间有很强的相关性，而女性没有相关性，表明FVC的病毒动力学在两性之间是不同的。
5. 最后，自然传播可能会阻碍FVC复制，因为被感染的接触动物的病毒滴度低于索引动物。这些结果阐明了鼠白血病病毒的复杂生活史，并证明了宿主性别对病原体传播动力学的重要作用。