High Shedding Potential and Significant Individual Heterogeneity in Naturally-Infected Alpine ibex (Capra ibex) With Brucella melitensis

Abstract

Wildlife reservoirs of infectious diseases raise major management issues. In Europe, brucellosis has been eradicated in domestic ruminants from most countries and wild ruminants have not been considered important reservoirs so far. However, a high prevalence of Brucella melitensis infection has been recently identified in a French population of Alpine ibex (Capra ibex), after the emergence of brucellosis was confirmed in a dairy cattle farm and two human cases. This situation raised the need to identify the factors driving the persistence of Brucella infection at high prevalence levels in this ibex population. In the present paper, we studied the shedding pattern of B. melitensis in ibex from Bargy Massif, French Alps. Bacteriological examinations (1–15 tissues/samples per individual) were performed on 88 seropositive, supposedly infected and euthanized individuals. Among them, 51 (58%) showed at least one positive culture, including 45 ibex with at least one Brucella isolation from a urogenital sample or a lymph node in the pelvic area (active infection in organs in the pelvic area). Among these 45 ibex, 26 (30% of the total number of necropsied animals) showed at least one positive culture for a urogenital organ and were considered as being at risk of shedding the bacteria at the time of capture. We observed significant heterogeneity between sex-and-age classes: seropositive females were most at risk to excrete Brucella before the age of 5 years, possibly corresponding to abortion during the first pregnancy following infection such as reported in the domestic ruminants. The high shedding potential observed in young females may have contributed to the self-sustained maintenance of infection in this population, whereas males are supposed to play a role of transmission between spatial units through venereal transmission during mating. This heterogeneity in the shedding potential of seropositive individuals should be considered in the future to better evaluate management scenarios in this system as well as in others.

Investigation of Brucella melitensis in Sable Antelope (Hippotragus niger) in South Africa

“…Infections were first identified in sable bulls in both Outbreak 2 and 3; they were the index cases, the putative source of infection brought for the ranches, with B. melitensis also being isolated from the testes of bulls in Outbreak 3. This is consistent with the potential venereal transmission, as has been reported in the Alpine ibex [ 48 ]. The Bovine Brucellosis Manual of South Africa stipulates that “should semen from an infected sable bull be used for artificial insemination, the risk of spread of the disease is great, but if used for natural service sable bulls do not appear to play a role in the spread of the disease” [ 11 ].…”

Brucella melitensis Rev.1 vaccination generates a higher shedding risk of the vaccine strain in Alpine ibex (Capra ibex) compared to the domestic goat (Capra hircus)

“…No major hyperthermia, polypnea, tachycardia, prostration, anorexia, weight loss or complaints were observed in the animals. Furthermore, in both live animals and at autopsy, no gross lesions suggestive of brucellosis infection (such as described by Freycon et al and Lambert et al [46, 47]) were observed in vaccinated or contact animals, particularly in the genitalia, udder or joints. No loss of appetite or body condition, trauma, or aggressive behavior were observed, despite close contact between individuals of the same batch over an extended period of 3 months.…”

Genetic epidemiology of the Alpine ibex reservoir of persistent and virulent brucellosis outbreak

“…Here, we studied the genetic and immunogenetic characteristics of 262 ibex captured between 2012 and 2017 by the French Hunting and Wildlife Agency in accordance with legal and ethical regulations (French environmental code, 2005, 2006; Préfecture de Paris, 2009; Préfecture de la Haute-Savoie, 2013, 2015a,b; French Minister of Ecology Sustainable Development and Energy, 2014). Animals were captured by dart-gun xylazine-ketamine anesthesia (Rompun ® , Bayer, Leverkusen, Germany and Imalgène ® , Merial, Lyon, France; 100 mg/individual) following protocols described in Lambert et al 67 . During captures, test-and-cull was implemented on the basis of serological tests (see below for further details on the serological method) as part of management measures decided by the French Authorities (Hars et al, 2013).…”

“…Further details on the validation method and the congruence of the FLIA with reference tests (Rose Bengal Test, Complement Fixation Test, iELISA) were provided in Anses (2014). Seropositive ibex were considered as infected by B. melitensis, but not necessarily infectious at the time of capture 67 .…”