Comparative Immunology, Microbiology and Infectious Diseases
Protection of Brucella abortus RB51 revaccinated cows, introduced in a herd with active Brucellosis, with presence of atypical humoral response
Introduction
Brucella is an intracellular gram-negative bacterium that causes Brucellosis in domestic and wild mammals; this disease is an important public health problem and can cause large economic losses in the farming industry.
Brucella abortus RB51 is a stable rough, attenuated mutant vaccine derived from the virulent strain 2308, the wboA gene in smooth B. abortus results in rough attenuated mutants which fail to produce the O polysaccharide chain [1]. The lack of the O chain of the LPS allows repeated use of RB51 vaccine without inducing antibodies that interfere with the serological diagnosis, due to this fact any positive reaction to standard tests is considered an infected animal [2].
The vaccination with reduced dose of RB51 protects adult cattle against abortion or infection caused by exposure to virulent B. abortus during the subsequent pregnancy [3]. The practice of vaccination and revaccination is permitted in endemic Brucellosis zones in Mexico, with the reduced dose of RB51 in females older than 8 months. Diagnosis is based on demonstration of specific antibodies to B. abortus antigen, the card test (CT) is for screening, rivanol test (RT), and complement fixation are used for confirmation. Serology and bacteriology combined, plus elimination of the infected animals from the herd reduces the incidence of this disease.
The objective of this work is to determine protection of RB51 reduced dose revaccination, against virulent B. abortus natural challenge in a herd with high Brucellosis prevalence and to determine if revaccinated cows had a response to serological tests.
Section snippets
Herds
Serum samples were collected from two cow herds in Mexico. Herd A. A Brucellosis-free herd of 160 Holstein-Friesian cows that has been monitored both by serology and milk culture repeatedly during the last 6 years. Herd B. A herd within a dairy area with endemic Brucellosis of 500 Holstein-Friesian cows; which had a serological Brucellosis prevalence of 38% at moment of work started. Vaccination and revaccination with B. abortus RB51 is routinely practiced in this herd.
Cattle and vaccination
In the Brucellosis free
Results
In herd A, the 35 vaccinated cows were CT and RT negatives until 405 days post-vaccination. The same serological tests were also negative for herd A total population. For the DTH at 350 post-vaccination day, 91% of 35 vaccinated animals were positives and 20 control group bovines were all negatives.
Once in herd B, the serum samples from 35 revaccinated cows at days 30, 60, 90 and 120 after revaccination, had up to 17% of positive results to CT, but all negatives to RT (Fig. 1). These cows
Discussion
It is well known that RB51 vaccination does not interfere with conventional serological techniques [2], [8]. In Brucellosis free herds, vaccination with a reduced dose of RB51 protects adult cattle against infection caused by exposure to virulent B. abortus. In previous experiments, all cows vaccinated with standard dose of RB51 remained seronegative to the tube agglutination test, but in the Dot-blot assay, vaccinated cattle had a detectable immune responses, although decline after 10 weeks
Acknowledgements
This work was supported by grant from CONACYT Mexico Grant: 36142 B. We thank Gerardo Flores-Gutiérrez for critically reading the manuscript.
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Brucellosis in Sub-Saharan Africa: Current challenges for management, diagnosis and control
2017, Acta TropicaCitation Excerpt :Both controlled studies and field observations with appropriate control groups demonstrate that S19 is superior to RB51 (Moriyón et al., 2004). Contrary to strain 19 that provides long-life useful immunity (Nicoletti, 1990) the “protective” lapse span of RB51 vaccine has not been investigated but RB51 revaccination, even of pregnant animals, has been used without success in attempts to bolster immunity (Herrera et al., 2008; Herrera-Lopez et al., 2010; Leal-Hernandez et al., 2005; Luna-Martinez and Mejia-Teran, 2002; Moriyón et al., 2004). Moreover, no controlled experiments have addressed the advantages of these expensive revaccination strategies.
The use of green fluorescent protein as a marker for Brucella vaccines
2011, VaccineCitation Excerpt :Similarly, animals vaccinated with rough B. abortus RB51 spontaneous mutant or rough B. melitensis punctual mutants, in addition to produce antibodies against many Brucella protein antigens, also generate antibodies against LPS core epitopes and in cases, to residual quantities of O chain determinants present in some of these rough bacterium, including RB51 [11,17,45]. These phenomena may be exacerbated after revaccination; a common practice in many low-income countries, mainly, when concomitant infections with field Brucella strains are present [17,18,46]. In addition, it has been argued that the level of protection of rough mutants is considerable lower than that conferred by smooth attenuated vaccines [10,11,18,20].
Epidemiological study of Brucellosis in cattle, immunized with Brucella abortus RB51 vaccine in endemic zones
2010, VaccineCitation Excerpt :In this low prevalence herd, at day 60 after vaccination, the number of new positive animals increased. This could be attributed to brucellosis incubation period, since it is reported that immunized cows with RB51 that present positive serology and can be indicative of an early infection of B. abortus field strains due to the fact that the incubation period can last until 253 days [21]. The work in our study do not support these earlier findings since the vaccinated animals with RB51 that resulted positive to CT, in their majority were not positive to Rivanol test, and when they did present positive generally showed titers of 1:25 to 1:100 in a transitory way.
Bovine Brucellosis
2010, Veterinary Clinics of North America - Food Animal PracticeCitation Excerpt :Like S19, RB51 can induce abortions under field conditions.41 Current data suggest that calfhood vaccinated cattle can be safely booster vaccinated with RB51 (1–3 × 109 CFUs) as pregnant adults.42,43 At present, the greatest controversy in regard to B abortus vaccination is whether calfhood vaccination with RB51 induces equivalent protection in cattle as compared with S19 vaccination.
Shedding of Brucella abortus rough mutant strain RB51 in milk of water buffalo (Bubalus bubalis)
2009, Preventive Veterinary Medicine