Brucella abortus RB51 in milk of vaccinated adult cattle.

The aim of this study was to evaluate the shedding of Brucella abortus in the milk of cows vaccinated with a full dose of RB51 during lactation. Eighteen cows, nine previously vaccinated with S19 as calves and nine non-vaccinated, were immunized subcutaneously with 1.3×10(10)CFU of B. abortus RB51, 30-60days after parturition. Milk samples from all animals were collected daily until day 7, and at weekly interval for the next 9 weeks after vaccination. To evaluate the shedding of B. abortus, milk samples were submitted for culture and PCR. No B. abortus was isolated from any sample tested. Only one sample, collected on first day after vaccination from a cow previously vaccinated, was faintly positive in the PCR. In conclusion, the public health hazard associated with milk consumption from cows vaccinated with RB51 in post-partum is very low, despite vaccination with the full dose and regardless of previous S19 vaccination.

Imunidade inata da glândula mamária bovina: resposta à infecção / Innate immunity of the bovine mammary gland: response to infection

A imunidade na glândula mamária pode ser classificada, assim como em outros sistemas, em inata ou inespecífica e adaptativa ou específica. A imunidade inata é a defesa predominante durante os estágios iniciais da infecção. As respostas inespecíficas estão presentes no local da infecção ou são ativadas rapidamente por numerosos estímulos e não aumentam pela exposição repetida ao mesmo agente etiológico. O primeiro obstáculo enfrentado por um patógeno para adentrar o úbere é composto pela barreira formada pelo esfíncter do teto e pelo tampão de queratina formado pelo epitélio queratinizado. Uma vez que o microrganismo tenha atravessado o canal do teto e alcançado a cisterna mamária, passam a atuar diversos fatores solúveis e celulares. Dentre os fatores solúveis, estão presentes: lactoperoxidase, sistema complemento, citocinas, lactoferrina, lisozima e NAGase. As defesas celulares inespecíficas na glândula mamária são representadas pelos neutrófilos, pelos macrófagos e pelas células natural killer. Na medida em que esses mecanismos funcionam adequadamente, a maioria dos patógenos será rapidamente eliminada antes que o sistema imune específico seja ativado, sem resultar em alterações na quantidade ou qualidade do leite produzido. Uma melhor compreensão sobre os mecanismos de defesa da glândula mamária e suas alterações durante os períodos críticos da infecção é imprescindível para o desenvolvimento de métodos mais eficazes de profilaxia e controle da mastite, a principal doença dos ruminantes leiteiros. O presente estudo revisou os principais aspectos responsáveis pelo desenvolvimento da imunidade inata na glândula mamária bovina.

The immunity in the mammary gland can be, as in other systems, classified in innate or adaptive immunity. The innate immunity is the predominant defense during the initial periods of infection. The non-specifics answers are present or are quickly activated in the infection's site by numerous stimulations, and these answers are not enhanced by repeated exposure to the same agent. The first obstacle to be faced by the agent is the barrier represented by the teat sphincter and the keratin plug. When the pathogenic agent crosses the teat canal and reaches the teat cistern, starts to act the humoral factors and the phagocytic cells starts do act. Among the humoral mediators there are the lactoperoxidase, complement, cytokines, lactoferrin, lysozyme and NAGase. The non-specific cellular defenses are represented by neutrophils, macrophages and natural killer cells. If these mechanisms have been functioning adequately, the majority of pathogens will be eliminated in a short time, before the specific immune system be activated. The fast elimination of the microorganisms will not allow these alterations in the amount or quality of produced milk. The best understanding of the defense mechanisms of the mammary gland and its alterations during the critical periods of infection, is an useful tool in devising and developing methods to control the mastitis, the major illness of dairy ruminants. This paper overviewed the most important aspects of the innate immunity of bovine mammary gland.