Detection of Cytopathic Bovine Viral Diarrhea Virus in the Ovaries of Cattle following Immunization with a Modified Live Bovine Viral Diarrhea Virus Vaccine

Abstract

Abstract. Economic loss from infection with bovine viral diarrhea virus (BVDV) is of worldwide concern.The unique pathogenesis and antigenic variability of BVDV have made this virus challenging to control. Vaccination programs are a major component of control and prevention strategies. Both killed and modified live vaccines are commercially available. Choice between killed and modified live vaccines is controversial. Of major concern is the safety of modified live vaccines. Little information is available on their tissue tropism and potential for causing pathology, especially with respect to the reproductive system. The objective of this study was to determine if BVDV could be detected in the ovary of cattle following immunization with a modified live BVDV vaccine. In 2 separate trials, 6 heifers and 4 mature cows were immunized with a modified live BVDV vaccine and ovaries were removed between 7 and 30 days postvaccination. Cytopathic BVDV was isolated from ovaries removed on days 8, 10, and 12. BVDV antigen was detected using immunohistochemistry on days 10-30. These findings are significant because replication of virus in the ovary could cause ovarian dysfunction, resulting in reduced fertility.Bovine viral diarrhea virus (BVDV) is one of the most important viral pathogens of cattle, 2,7 and its control and prevention are of worldwide concern. Because of its complex pathogenesis and antigenic diversity, control and prevention of BVDV infections has been extremely challenging. Control programs center around elimination of cattle persistently infected with BVDV, biosecurity, and vaccination. 2,7 The role of vaccinations in the prevention of BVDV has become extremely controversial. Much of the debate revolves around the use of modified live or killed BVDV vaccines. Modified live BVDV vaccines have been available since 1961. 6 Currently, these vaccines use cytopathic BVDV strains, which have been attenuated through multiple cell culture passage. 4 It is generally felt that modified live vaccines provide higher levels of protective immunity that are of longer duration. 2,4 However, the safety of these vaccines is of concern. 2,10 Postvaccination mucosal disease, 16,20 immunosuppression, 21 and fetal infection resulting in abortion and congenital anomalies 14,23 have been reported following modified live BVDV vaccination. Also, disease resulting from the contamination of modified live vaccines with noncytopathic BVDV strains has been

The effects of vaccination on serum hormone concentrations and conception rates in synchronized naive beef heifers

“…A previous study showed that naïve heifers vaccinated with a MLV vaccine on the day of second PGF injection, only had a 30% first service conception rate and a 57% second service conception rate, whereas control heifers had a 78% first service conception rate and a 100% second service conception rate [7]. In another study, seronegative heifers vaccinated with a MLV vaccine containing BVDV had virus isolated from white blood cells in three of six heifers between 6 and 10 days postvaccination; from the ovary 8, 10, and 12 days postvaccination; and BVDV antigen was detected in the ovary 10, 20, and 30 days postvaccination [23]. Heifers infected with BHV-1 at or near estrus had disrupted luteal function, but in most heifers, the next estrous cycle was normal [24].…”

Priming Cross-Protective Bovine Viral Diarrhea Virus-Specific Immunity Using Live-Vectored Mosaic Antigens

“…The MLV vaccines are not considered to be safe since the attenuated virus can revert to wild type virus, cause in-utero infections and mucosal disease, carry the risk of vaccine contamination with adventitious viruses, and are immunosuppressive [41, 42]. Furthermore, MLV strains may cause ovarian lesions leading to infertility in cows [43]. Both killed and MLV vaccine virus are traditionally grown in MDBK cells and recent findings show that calves fed colostrum from some dams vaccinated with killed BVDV vaccine formulated with adjuvant have a high incidence of a syndrome characterized by spontaneous bleeding, severe anemia with heavy bone marrow damage.…”

Fetal protection in heifers vaccinated with a modified-live virus vaccine containing bovine viral diarrhea virus subtypes 1a and 2a and exposed during gestation to cattle persistently infected with bovine viral diarrhea virus subtype 1b

“…Thus, vaccination should be performed prior to this period for effective immunity to develop; however, vaccination of naïve heifers or cows with MLV products must be performed prior to breeding because these vaccines may have an adverse effect on the ovary or conceptus or on embryonic implantation. 33,34 Demonstration of efficacy is important for the assurance of protection afforded by commercial vaccines, which is necessary for licensure of products as well as for the initiation and continued use by producers. Efficacy studies providing evidence of protection against fetal infections and PI calves initially used aerosol administration of laboratory-prepared challenge virus into the nasal cavity of vaccinates and control cattle.…”