Mycobacterial Infections in Striped Bass from Delaware Bay

Abstract

Eighty striped bass Morone saxatilis were obtained from Delaware Bay using commercial gill nets set adjacent to Woodland Beach (n = 70) and Bowers Beach (n = 10) in December 2003. Fish were examined for gross lesions. Total lengths (TLs) and eviscerated weights were determined to calculate condition factors (K). Portions of spleens were aseptically harvested for bacterial culture, and portions of spleens, kidneys (anterior and posterior), livers, and gonads were obtained for histological examination. The size distribution of the striped bass was relatively homogeneous; the mean TL was about 600 mm for all samples. Mean K exceeded 0.95 in all samples and was not significantly different (P > 0.05) among samples. Significant differences in mycobacterial infection prevalence (P < or = 0.05) were observed among samples; samples obtained at Woodland Beach (WB) on December 10 (53.8%, n = 13) and December 17 (7.1%, n = 42) exhibited the most striking differences in prevalence. Mycobacterial infection intensity ranged from 1 X 10(2) to 1 X 10(7) colony-forming units per gram of spleen. Acanthocephalan infection prevalence and intensity, non-acid-fast bacterial infection prevalence, and fish sex ratio were also significantly different among the samples (P< or = 0.05). Similar to the mycobacterial infections, differences in sex ratio, acanthocephalan infection, and non-acid-fast bacterial infection were observed between the WB samples taken on December 10 and 17. However, no significant associations (P > 0.05) were observed between sex ratio or these infections and mycobacterial infection. The differences in bacterial and parasite infection prevalence and intensity and fish sex ratio in some samples indicate that these fish had a different history and that the epizootiology of mycobacterial infection in striped bass from Delaware Bay may be relatively complex.

Low prevalence of splenic mycobacteriosis in migratory striped bass Morone saxatilis from North Carolina and Chesapeake Bay, USA

“…Prevalence of mycobacteriosis > 50% has been reported from Chesapeake Bay (Overton et al 2003, Kaattari et al 2005, whereas prevalence ≤20% was observed in striped bass resident to estuaries outside Chesapeake Bay (Ottinger & Jacobs 2006, Ottinger et al 2007) and was 6.8% in coastal migratory fish (present study). In addition, granulomatous inflammation was mild in all diseased striped bass examined in the present study, but moderate and severe forms of disease are not uncommon in Chesapeake Bay (Kaattari et al 2005).…”

“…The recently described M. shottsii is by far the predominant isolate from Chesapeake Bay striped bass (Rhodes et al 2004, Stine et al 2010. Previously known only from Chesapeake Bay striped bass, M. shottsii was recently detected in striped bass from Albemarle Sound and Long Island (Stine et al 2009), Delaware Bay striped bass (Ottinger et al 2007), and from Chesapeake Bay white perch Morone americana (Stine et al 2009). It is interesting that this species is recovered from striped bass in other regions, yet disease prevalence is much lower, which may point to differences in disease susceptibility or disease-associated mortality between Chesapeake Bay fish and fish resident to other estuaries (Roanoke River, Delaware Bay, and Long Island).…”

“…Visceral granulomas (spleen, liver, and kidney) with acidfast bacilli were found in striped bass from Roanoke River (18% of 60 fish), North Carolina, in April 2003 (Ottinger & Jacobs 2006) and Delaware Bay (6.25% of 80 fish), Delaware, in December 2003 (Ottinger et al 2007), and ongoing efforts suggest approximately 20% in Long Island Sound (M. Fast pers. comm.).…”

“…comm.). Also, multiple species of Mycobacterium were isolated from striped bass from Albemarle Sound, Delaware Bay, and Long Island Sound (Ottinger et al 2007, Stine et al 2009). Chesapeake Bay stock contribute a high proportion of fish to the mixed coastal striped bass population (Berggren & Lieberman 1978, Wirgin et al 1993, and while transmission modes of mycobacteriosis are unknown, intermixing of fish from multiple stocks during annual migrations leaves open the possibility of transmission of this disease to Roanoke River and Hudson River populations.…”

“…Mycobacteriosis has been reported from Delaware Bay striped bass (Ottinger et al 2007), and Mycobacterium spp. infections have been reported from Roanoke River and Long Island Sound striped bass (Stine et al 2009), but mycobacteriosis has not been studied previously in the coastal migratory striped bass population.…”