Bonamia parasites: a rapidly changing perspective on a genus of important mollusc pathogens

Abstract

Organisms of the genus Bonamia are intracellular protistan parasites of oysters. To date, 4 species have been described (B. ostreae, B. exitiosa, B. perspora and B. roughleyi), al though the status of B. roughleyi is controversial. Introduction especially of B. ostreae and B. exitiosa to naïve host populations has been shown to cause mass mortalities in the past and has had a dramatic impact on oyster production. Both B. ostreae and B. exitiosa are pathogens notifiable to the World Organisation for Animal Health (OIE) and the European Union. Effective management of the disease caused by these pathogens is complicated by the extensive nature of the oyster production process and limited options for disease control of the cultured stocks in open water. This review focuses on the recent advances in research on genetic relationships between Bonamia isolates, geographical distribution, susceptible host species, diagnostics, epizootiology, host− parasite interactions, and disease resistance and control of this globally important genus of oyster pathogens.KEY WORDS: Bonamia ostreae · Bonamia exitiosa · Oyster disease · Phylogenetics · Geographical spread · Diagnostics · Epizootiology · Host−parasite interaction · Bonamiosis Resale or republication not permitted without written consent of the publisher Contribution to DAO Special 7 'Microcell parasites of molluscs'

Bonamia ostreae in the New Zealand oyster Ostrea chilensis: a new host and geographic record for this haplosporidian parasite

“…typically infect flat oysters Ostrea of the bivalve family Ostreidae (Engelsma et al 2014), with O. edulis considered as the type-host for B. ostreae. To rule out the possibility of a New Zealand incursion of O. edulis and, therefore with it, an incidental incursion of B. ostreae, the species of the oyster host was identified by DNA barcoding.…”

“…Bonamia microcells are small (typically 1−3 µm), uninucleated, and infect oyster hemocytes causing a disease known as bonamiosis (Hine & Jones 1994, OIE 2012. Molecular and ultrastructural studies have identified 4 Bonamia species from a number of hosts and locations throughout the world (Hine et al 2001 and to the European Union (OIE 2012, Engelsma et al 2014.…”

“…However, the discovery of a Bonamia-like parasite in Crassostrea ariakensis in North Carolina, USA (Burreson et al 2004), and the description of another parasite as B. perspora from O. stentina from the same area , in combination with the discovery of B. exitiosa and B. exitiosa-like parasites in O. stentina from the Mediterranean (Hill et al 2010), O. chilensis from Chile (Campalans et al 2000, Lohrmann et al 2009, O. puelchana from Argentina (Kroeck & Montes 2005), O. angasi from Australia, and O. edulis from Europe (Abollo et al 2008, Longshaw et al 2013) have initiated a change in perception of the distribution of Bonamia (Engelsma et al 2014). Some Bonamia species are now reported with overlapping geographic ranges (Abollo et al 2008, Narcisi et al 2010, Carrasco et al 2012, Longshaw et al 2013) and in one case to the point of a concurrent infection of B. exitiosa and B. ostreae within the same O. edulis host (Abollo et al 2008).…”

“…The reported infection of B. ostreae in O. chilensis occurred after the oyster host had been transferred to a B. ostreae endemic area in Cornwall, England (Bucke & Hepper 1987); however, there are still limited scientific data on the susceptibility of O. chilensis to infection by B. ostreae (Engelsma et al 2014). Moreover, it is also uncertain if B. ostreae can infect other oyster species such as O. angasi (see Bougrier et al 1986), O. puelchana (see Pascual et al 1991) and C. gigas (see Lynch et al 2010).…”

Managing marine mollusc diseases in the context of regional and international commerce: policy issues and emerging concerns

“…The case of OsHV-1 mvar highlights an additional issue related to emerging diseases: it can be challenging to place [42,43]. One unexpected report was the detection of the parasite in O. edulis from Limfjorden, Denmark, a zone that gained its free status regarding bonamiosis in 2004 [44].…”