Age-dependent prevalence of anti-Brucella antibodies in hooded seals Cystophora cristata

Abstract

Investigations of hooded seals Cystophora cristata have revealed high prevalences of Brucella-positive seals in the reduced Northeast Atlantic stock, compared to the increasing Northwest Atlantic stock. This study evaluated the relation between Brucella-serostatus in seals in the Northeast Atlantic stock and age, sex, body condition and reproduction. Bacteriology documented which animals and organs were B. pinnipedialis positive. No relationship was observed between Brucella-serostatus and body condition or reproductive traits. Pups (<1 mo old) had a substantially lower probability of being seropositive (4/159, 2.5%) than yearlings (6/17, 35.3%), suggesting that exposure may occur post-weaning, during the first year of life. For seals >1 yr old, the mean probability of being seropositive decreased with age, with no seropositives older than 5 yr, indicating loss of antibody titre with either chronicity or clearance of infection. The latter explanation seems to be most likely as B. pinnipedialis has never been isolated from a hooded seal >18 mo old, which is consistent with findings in this study; B. pinnipedialis was isolated from the retropharyngeal lymph node in 1 seropositive yearling (1/21, 5%). We hypothesize that this serological and bacteriological pattern is due to environmental exposure to B. pinnipedialis early in life, with a subsequent clearance of infection. This raises the question of a reservoir of B. pinnipedialis in the hooded seal food web.KEY WORDS: Pinniped · Pups · Brucellosis · Serostatus · Bacteriology · Infection clearance · Atlantic hooded seal stock · Food web Resale or republication not permitted without written consent of the publisherDis Aquat Org 106: [187][188][189][190][191][192][193][194][195][196] 2013 Greenland (NWS) (Andersen et al. 2009) and the Nordic Seas (Greenland, Norwegian and Icelandic Seas, NES) (Folkow et al. 1996(Folkow et al. , 2010.While estimates of abundance in the NWS have increased since the 1980s (Hammill & Stenson 2006), abundance of the NES appears to have decreased to only 10 to 15% of the 1946 population size, from 575 000 hooded seals in 1946 to approximately 85 000 hooded seals in 2011, and has remained stable at this low level since the 1980s (ICES 2011). Hooded seal hunts in the West Ice have been conducted since the 18th century, and after 1920 the hunt was of a significant extent. In 1958, agreements were made between Norway and the Soviet Union on time and activity restrictions on the hooded seal hunt in the West Ice, but it was not until 1971 that quotas were introduced (Bjørge 2010). The introduction of quotas did not alter the negative population development in the NES, and due to the decline of the NES, no commercial hunt has been conducted on the NES since 2007 (ICES 2011), and the hooded seal species has been classified since 2008 as 'Vulnerable' in the Red List of Threatened Species of the International Union for Conservation of Nature (IUCN) (Kovacs 2008).Brucella spp. were first isolated from marine mammals in 1994 (Ross et al....

Serologic evidence of Brucella infection in pinnipeds along the coast of Hokkaido, the northernmost main island of Japan

“…2). This result is very similar to that in a previous study of hooded seals (Cystophora cristata) in the north Atlantic population, which found that pups (<1 month old) had a lower percentage of seropositivity (2.5%) than yearlings (35.3%) (28). A similar agedependent pattern of anti-Brucella antibodies has also been reported for eastern Pacific harbor seals (P. vitulina richardsi) (29).…”

Modelling the population size and dynamics of the British grey seal

“…It seems likely that much of this occurs within the first few months at-sea: weaned pups have around a month to develop an effective foraging strategy before terminal starvation occurs (Bennett, Speakman, Moss, Pomeroy, & Fedak, 2007). There is evidence that juvenile seals may be more susceptaible to disease than adults, however, as energy is directed to growth at the expense of their immune system (Nymo et al, 2013). Thus, although such individuals may face a degree of competitive exclusion from the most profitable foraging patches (Breed, Bowen, & Leonard, 2013), there is no evidence that starvation-induced mortality would be higher in juveniles (aged 1-5 years) compared with adults (aged 6+ years).…”

The quest for a true One Health perspective of brucellosis

“…Recently, two independent studies suggest that hooded seals are not the definitive host of B. pinnipedialis (67,89). Indeed, gross pathology associated with B. pinnipedialis infection has not been described in seals and vertical transmission is not likely to occur, since B. pinnipedialis has never been isolated from females of reproductive age.…”