Abstract
Epidemiological investigations implemented in wild and domestic ruminants evidenced a reservoir for Brucella in Capra ibex in the French Alps. Vaccination was considered as a possible way to control Brucella infection in this wildlife population. Twelve ibexes and twelve goats were allocated into four groups housed separately, each including six males or six non-pregnant females. Four to five animals were vaccinated and one or two animals were contact animals. Half of the animals were necropsied 45 days post-vaccination (pv), and the remaining ones at 90 days pv. Additional samples were collected 20 and 68 days pv to explore bacterial distribution in organs and humoral immunity. Neither clinical signs nor Brucella-specific lesions were observed and all vaccinated animals seroconverted. Brucella distribution and antibody profiles were highly contrasted between both species. Proportion of infected samples was significantly higher in ibex compared to goats and decreased between 45 and 90 days pv. Two male ibex presented urogenital excretion at 20 or 45 days pv. The bacterial load was higher 45 days in ibexes compared to goats, whereas it remained moderate to low 90 days pv in both species with large variability between animals. In this experiment, differences between species remained the main source of variation, with low impact of other individual factors. To conclude, multiplicative and shedding capacity of Rev.1 was much higher in ibex compared to goats within 90 days. These results provide initial information on the potential use in natura of a commercial vaccine.
Highlights
Brucella melitensis is a Gram-negative facultative intracellular bacterium responsible for brucellosis in small ruminants, a widespread zoonosis in many sheep- and goat-raising countries worldwide [1,2,3,4].Brucellosis eradication in small ruminants has been achieved in most of European Union (EU) countriesPonsart et al Vet Res (2019) 50:100 observed in the Bargy area (38%) suggested the presence of an unexpected wildlife reservoir [11]
Despite the phylogenetic closeness of ibex and domestic goats (Capra hircus) [24], experts have highlighted the importance of confirming vaccine safety in Alpine ibex before its application in natura [13, 25], taking into account the other potential negative impacts of a live Brucella vaccine reported in other wildlife species [26,27,28,29,30], and potential interference with local monitoring and management programs [25]
Contrary to the experts’ expectations, our results revealed a highly contrasting vaccine outcome between the two species, which invalidated the hypothesis of comparable innocuousness of the Rev.1 vaccine between the Alpine ibex and the domestic goat
Summary
Brucella melitensis is a Gram-negative facultative intracellular bacterium responsible for brucellosis in small ruminants, a widespread zoonosis in many sheep- and goat-raising countries worldwide [1,2,3,4].Brucellosis eradication in small ruminants has been achieved in most of European Union (EU) countriesPonsart et al Vet Res (2019) 50:100 observed in the Bargy area (38%) suggested the presence of an unexpected wildlife reservoir [11]. Focused culling of seropositive or ill ibexes and mass culling have been implemented since 2013, which reduced the population by half [12], raising the question of the social acceptability of conducting mass culling in a protected species [11]. This management strategy did not result in a significant reduction in seroprevalence [11, 12]. A scientific expert appraisal suggested that vaccination with the B. melitensis Rev. strain of ibex could be considered for better control of this wildlife reservoir [13, 14]. It was decided to design a study aimed at checking the innocuousness of Rev. in non-pregnant sexually mature ibexes that are the most common captured/sampled age class (juveniles being, on the contrary, rarely captured) [12]
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