Abortions in pregnant dairy cows after vaccination with Brucella abortus strain RB51

Abstract

The Rose Bengal test, Wright test and 2-mercaptoethanol test (OIE 2004) on the dams' serum showed negative results at the time of abortion and three to four weeks later. Commercial indirect ELISA kits (SVANOVA Biotech) were used for the detection of antibodies to bovine viral diarrhoea virus (BVDV), and bovine herpesvirus type 1 (BHV-1) in serum, according to the manufacturer's instructions (Kampa and others 2004). Serum samples from the aborted cattle were BVDV antibody-positive at the time of the abortion and showed a decrease in the antibody titre within four weeks after the abortion. All the serum samples were negative for antibody to BHV-1.Colonies morphologically resembling Brucella species were isolated from the abomasal contents of a fetus that was aborted from a vaccinated cow. No bacteria grew from culture of the remaining fetuses. Brucella species were not isolated from milk samples from any of the cows. The isolated colonies were Gram stained, and were subjected to serological and biochemical tests. Biomolecular typing by PCR was also carried out. The colonies were identified as B abortus strain RB51 by standard microbiological procedures (Alton and others 1988, Schurig and others 1991). Similar results were obtained by molecular typing using a specific PCR method (Vemulapalli and others 1999) to distinguish RB51 from both Brucella field isolates and from its parent virulent strain, 2308 (Fig 1). This PCR method has been approved by the World Organisation for Animal Health (OIE) for the definitive identification of strain RB51 (OIE 2004). In addition, the Brucellosis Reference Laboratory of the Razi Vaccine and Serum Research Institute, Tehran, Iran, confirmed the identity of the isolate as vaccine strain of B abortus RB51.Although RB51 has been reported to cause fetal infection and abortion, when two heifers less than 12 months of age were inadvertently vaccinated during pregnancy with a full dose of the RB51 vaccine strain (Van Metre and others 1999), the occurrence of abortion after vaccination of pregnant cattle with a reduced dose of RB51 has not previously been reported. Most published evidence suggests that RB51 does not cause abortion in cattle and is less abortifacient than S19 if administered during pregnancy (Palmer and others 1997). Samartino and others (2000) reported that the vaccination of pregnant cattle that had been vaccinated with strain S19 as calves with 1·5 x 10 9 cfu RB51 appears to be a safe procedure. Palmer and others (1997) reported that subcutaneous vaccination of pregnant cattle at six months' gestation with a Abortions in pregnant dairy cows after vaccination with Brucella abortus strain RB51

Clinical Presentations of Brucellosis Over a Four-Year Period at Sultan Qaboos University Hospital and Armed Forces Hospital, Muscat, Oman

“…Studies have confirmed that the live vaccine may cause abortions and premature births in pregnant dairy cows. 32,33 Thus, the burden of prevention lies on raising public awareness and curtailing unsafe practices with regard to raw dairy consumption.…”

Analysis of the risk factors for bovine brucellosis in dairy herds of the Rio Branco microregion, Acre, Brazil

“…However, they showed considerable seropositivity, which was justified by the expectation of the 80% protection that the vaccine gives to herds. The RB51 vaccine sample has been alternatively used in several countries in animals aged over 8 months old or as a booster of B19, demonstrating greater resistance to infection and reducing abortion rates (YAZDI et al, 2009;BASTOS et al, 2012). However, it is still not used in the state.…”

Sustained antigen release polyanhydride-based vaccine platform for immunization against bovine brucellosis

“…However, RB51 has some drawbacks. Although less virulent than other vaccine strains and generally safe for use in pregnant cattle (Palmer et al., 1997), RB51 can be abortigenic (Yazdi et al., 2009). Additionally, recent reports have shown that RB51 can be shed in milk of previously-vaccinated cattle and infect humans through the consumption of unpasteurized milk (Cossaboom et al., 2018).…”