Use of serology and real time PCR to control an outbreak of bovine brucellosis at a dairy cattle farm in the Nile Delta region, Egypt

Abstract

BackgroundBovine brucellosis remains one of the most prevalent zoonotic infections affecting dairy cattle in developing countries where the applied control programs often fail. We analyzed the epidemiologic pattern of bovine brucellosis in a dairy cattle herd that showed several cases of abortions after regular vaccination with RB51 (B. abortus vaccine). In 2013 thirty dairy cows, from a Holstein-Friesian dairy herd with a population of 600 cattle, aborted five months post vaccination by a regular RB51 vaccine. Blood samples were drawn from milking cows and growing heifers, as well as heifers and cows pregnant up to 6 months. These samples were collected in June 2013 (n = 257) and May 2014 (n = 263) and were tested by real time (rt)-PCR as well as serological tests, in particular Rose Bengal Test (RBT), Enzyme-Linked Immunosorbent Assays (ELISA) and Fluorescence Polarization Assay. Tissue specimens were also collected from an aborted fetus and cultured. Isolates were subjected to bacteriological typing tests at the genus and species levels.ResultsFive months post vaccination with RB51 vaccine, Brucella (B.) DNA was detected in blood samples of cows by rt-PCR. The serological tests also revealed the spread of Brucella field strains within the herd in 2013. Four Brucella isolates were recovered from specimens collected from the aborted fetus. These isolates were typed as follows: one B. abortus RB51 vaccine strain and three isolates of B. abortus field strain. The seropositive cows with positive rt-PCR might indicate an infection by the Brucella field strain; while the positive rt-PCR results from seronegative animals may either be due to circulating RB51 vaccine DNA in vaccinated animals or to circulating field strain in infected animals before seroconversion.ConclusionThe results herein suggest that PCR can be a good supplementary tool in an outbreak situation, if an assay is available that can differentiate vaccine and field strains with a high analytical sensitivity. We recommend using RBT and ELISA in parallel in outbreak situations, to identify as many infected animals as possible during the initial screenings. This test procedure should be repeated for at least three successive negative tests, with one month interval.

Detection and characterization of Brucella spp. in bovine milk in small-scale urban and peri-urban farming in Tajikistan

“…If this is the case, it might partially explain the discrepancy between the serology and qPCR results observed in the current study. Another plausible explanation for the discrepancy between the serology and qPCR results might be previous vaccination against brucellosis [33]. However, in this study, the information given from the local official veterinarians that none of the cattle had been vaccinated against brucellosis is considered reliable because there is no national control programme for brucellosis among livestock in Tajikistan.…”

Seroprevalence of brucellosis among cattle slaughtered in three municipal abattoirs of Gombe state, Northeastern Nigeria

“…The risk of bovine brucellosis is not only restricted to the animal husbandry alone but also represent significant zoonotic implications characterized by debilitating and severe complications in humans [1]. Serological studies have shown that bovine brucellosis is a common problem in many grazing zone in Nigeria [7].…”

“…Bovine brucellosis is a disease with a significant economic and public health importance due to losses incurred as a result of infertility in animals and extensive chronic morbidity in humans [1]. In Nigeria, bovine brucellosis is a major animal health problem affecting the growth of the cattle industry.…”

Outbreak of Occupational Brucellosis at a Pharmaceutical Factory in Southeast China

“…1 is used in sheep and goats (Rubach et al., ). The vaccines still have a drawback as they retain pathogenicity and sometimes cause abortion in vaccinated animals and debilitating illness in humans (Gwida et al., ). Human vaccine against brucellosis has been adopted for many years, but vaccines are not widely available and concerns exist about their safety (Godfroid et al., ) sheep placentas from Inner Mongolia province, which the vaccination rate for sheep was previously only 31.6% (Chen et al., ).…”