世界各地的牛群中有许多病毒性疾病是地方性疾病。许多病毒穿过胎盘并导致流产和胎儿畸形的能力是众所周知的。还有大量证据表明，病毒感染对于奶牛还有其他影响，反映在受胎率的降低上。但是，这些影响很大程度上取决于单个动物首次感染该疾病的时间，因此难以量化。本文介绍了5种可能影响奶牛繁殖力的病毒，以及它们的潜在作用机制。妊娠中期非细胞病变型牛病毒性腹泻病毒（bovine viral diarrhea virus, BVDV）的急性感染会使流产率升高或导致持续感染的犊牛出生。在临近配种期感染BVDV会直接影响卵巢和子宫内膜，导致发情周期不规律和早期胚胎死亡。BVDV诱发的免疫抑制也可能降低繁殖力，从而增加对细菌的易感性。牛疱疹病毒（bovine herpesvirus, BHV）-1型在青春期前的小母牛中最常见，会导致它们生长减缓，延迟繁殖并提高首次产犊的年龄，先前受感染的动物继而表现出繁殖力的降低。尽管这可能与肺损伤有关，但也有卵巢病变的相关报告。初次感染后，BHV-1和BHV-4都潜伏在宿主中，并且可能在以后由于应激而重新激活，如与产犊和早期泌乳有关的应激。虽然仅感染BHV-4可能不会降低繁殖力，但它似乎与已建立的细菌病原体（如大肠杆菌和化脓隐秘杆菌）共同作用，促进子宫内膜炎的发展并延迟产犊后母牛的子宫修复机制。施马伦贝格病毒（Schmallenberg virus, SBV）和蓝舌病病毒（bluetongue virus, BTV）均以昆虫作为媒介传播，导致流产率和先天畸形的增加。BTV-8同时还损害孵出囊泡的发育；此外，任何一种病毒在繁殖前后的感染基本都会降低受胎率。尽管受胎率的降低通常难以量化，但足以造成经济损失，这有助于衡量疫苗接种和根除方案的效益。

Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence that viral infections have additional actions in dairy cows, which are reflected in reduced conception rates. These effects are, however, highly dependent on the time at which an individual animal first contracts the disease and are less easy to quantify. This paper reviews the evidence relating to five viruses that can affect fertility, together with their potential mechanisms of action. Acute infection with non-cytopathic bovine viral diarrhea virus (BVDV) in mid-gestation increases abortion rates or causes the birth of persistently infected calves. BVDV infections closer to the time of breeding can have direct effects on the ovaries and uterine endometrium, which cause estrous cycle irregularities and early embryo mortality. Fertility may also be reduced by BVDV-induced immunosuppression, which increases the susceptibility to bacterial infections. Bovine herpesvirus (BHV)-1 is most common in pre-pubertal heifers, and can slow their growth, delay breeding, and increase the age at first calving. Previously infected animals subsequently show reduced fertility. Although this may be associated with lung damage, ovarian lesions have also been reported. Both BHV-1 and BHV-4 remain latent in the host following initial infection and may be reactivated later by stress, for example associated with calving and early lactation. While BHV-4 infection alone may not reduce fertility, it appears to act as a co-factor with established bacterial pathogens such as Escherichia coli and Trueperella pyogenes to promote the development of endometritis and delay uterine repair mechanisms after calving. Both Schmallenberg virus (SBV) and bluetongue virus (BTV) are transmitted by insect vectors and lead to increased abortion rates and congenital malformations. BTV-8 also impairs the development of hatched blastocysts; furthermore, infection around the time of breeding with either virus appears to reduce conception rates. Although the reductions in conception rates are often difficult to quantify, they are nevertheless sufficient to cause economic losses, which help to justify the benefits of vaccination and eradication schemes.