The serological BHV1 status of dams determines the precolostral status of their calves

Role of Infection and Immunity in Bovine Perinatal Mortality: Part 2. Fetomaternal Response to Infection and Novel Diagnostic Perspectives

Simple Summary

Bovine perinatal mortality (death of the fetus or calf before, during, or within 48 h of calving at full term (≥260 days) may be caused by noninfectious and infectious causes. Although infectious causes of fetal mortality are diagnosed less frequently, infection in utero may also compromise the development of the fetus without causing death. This review presents fetomaternal responses to infection and the changes which can be observed in such cases. Response to infection, especially the concentration of immunoglobulins and some acute-phase proteins, may be used for diagnostic purposes. Some changes in internal organs may also be used as an indicator of infection in utero. However, in all cases (except pathogen-specific antibody response) non-pathogen-specific responses do not aid in pathogen-specific diagnosis of the cause of calf death. But, nonspecific markers of in utero infection may allow us to assign the cause of fetal mortality to infection and thus increase our overall diagnosis rate, particularly in cases of the “unexplained stillbirth”.

Abstract

Bovine perinatal mortality due to infection may result either from the direct effects of intrauterine infection and/or the fetal response to such infection, leading to the fetal inflammatory response syndrome (FIRS). Both intrauterine infection and FIRS, which causes multi-organ damage and involution of immune organs, compromise fetal survivability, sometimes fatally. Organ injury associated with FIRS may, in addition to causing fetal mortality, irreversibly compromise extrauterine adaptation of the neonate, a recognized problem in human fetuses. Diagnosis of intrauterine infection and of FIRS requires related, but independent analytical approaches. In addition to detection of pathogens, the immune and inflammatory responses of the bovine fetus may be utilized to diagnose intrauterine infection. This can be done by detection of specific changes in internal organs and the measurement of antibodies and/or elements of the acute phase reaction. Currently our ability to diagnose FIRS in bovine fetuses and neonates is limited to research studies. This review focuses on both the fetomaternal response to infection and diagnostic methods which rely on the response of the fetus to infection and inflammatory changes, as well other methods which may improve diagnosis of intrauterine infection in cases of bovine perinatal mortality.

Studies of embryo transfer from cattle clinically affected by bovine spongiform encephalopathy (BSE)

Semen from 13 bulls, eight with clinical bovine spongiform encephalopathy (BSE), was used to artificially inseminate (AI) 167 cows with clinical BSE, and their resultant embryos were collected non-surgically seven days after AI. The viable and non-viable embryos with intact zonae pellucidae were washed 10 times (as recommended by the International Embryo Transfer Society) then frozen. Later, 587 of the viable embryos were transferred singly into 347 recipient heifers imported from New Zealand, and 266 live offspring were born of which 54.1 per cent had a BSE-positive sire and a BSE-positive dam. The recipients were monitored for clinical signs of BSE for seven years after the transfer, and the offspring were monitored for seven years after birth. Twenty-seven of the recipients and 20 offspring died while being monitored but none showed signs of BSE. Their brains, and the brains of the recipients and offspring killed after seven years, were examined for BSE by histopathology, PrP immunohistochemistry, and by electron microscopy for scrapie-associated fibrils. They were all negative. In addition, 1020 non-viable embryos were sonicated and injected intracerebrally into susceptible mice (20 embryos per mouse) which were monitored for up to 700 days, after which their brains were examined for spongiform lesions. They were all negative. It is concluded that embryos are unlikely to carry BSE infectivity even if they have been collected at the end-stage of the disease, when the risk of maternal transmission is believed to be highest.