Interference with Reproduction

In breeding colonies, changes in fertility may be the cause of serious trouble. Infections giving rise to clinical disease in a major part of the population are likely to reduce fertility. It is also quite obvious that infections such as rotaviruses207 or mouse hepatitis virus208 causing high mortality in newborn animals will reduce the outcome of breeding or disturb experiments with newborn animals. Also, direct effects of the infection on reproduction such as the change in sex hormones, pathological anatomical changes in the reproductive tract, or infection of the embryo causing abortion and stillbirths are observed, as, for example, may be the case for parvoviruses.100 Many microorganisms, e.g., retroviruses, lymphocytic choriomeningitis virus,163 parvoviruses,105 ectromelia virus,209 cardioviruses,139 and Clostridium piliforme30,31 posses the ability to cross the placenta barrier. Uterine infections — probably without passage of the placenta barrier — have been observed for many bacteria, e.g., Salmonella spp.70 and Pasteurella pneumotropica.210 However, with the exception of the retroviruses and lymphocytic chorio-meningitis virus, spontaneous infections of fetuses are rare. Mycoplasma pulmonis is known to be harmful to reproduction, altering a number of reproductive parameters,211 and infection with Mycoplasma spp. and certain purulent bacteria is a risk in embryo transfer, for which the application of aseptic principles is essential.212

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