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- Title
Detection and virulence of Lactococcus garvieae and L. petauri from four lakes in southern California.
- Authors
Abraham, Taylor; Yazdi, Zeinab; Littman, Eric; Shahin, Khalid; Heckman, Taylor I.; Quijano Cardé, Eva Marie; Nguyen, Diem Thu; Hu, Ruixue; Adkison, Mark; Veek, Tresa; Mukkatira, Kavery; Richey, Christine; Kwak, Kevin; Mohammed, Haitham H.; Ortega, Cesar; Avendaño‐Herrera, Ruben; Keleher, William; LePage, Véronique; Gardner, Ian; Welch, Timothy J.
- Abstract
Objective: The first objective of the study aimed to detect the presence of Lactococcus petauri, L. garvieae, and L. formosensis in fish (n = 359) and environmental (n = 161) samples from four lakes near an affected fish farm in California during an outbreak in 2020. The second objective was to compare the virulence of the Lactococcus spp. in Rainbow Trout Oncorhynchus mykiss and Largemouth Bass Micropterus salmoides. Methods: Standard bacterial culture methods were used to isolate Lactococcus spp. from brain and posterior kidney of sampled fish from the four lakes. Quantitative PCR (qPCR) was utilized to detect Lactococcus spp. DNA in fish tissues and environmental samples from the four lakes. Laboratory controlled challenges were conducted by injecting fish intracoelomically with representative isolates of L. petauri (n = 17), L. garvieae (n = 2), or L. formosensis (n = 4), and monitored for 14 days postchallenge (dpc). Result: Lactococcus garvieae was isolated from the brains of two Largemouth Bass in one of the lakes. Lactococcus spp. were detected in 14 fish (8 Bluegills Lepomis macrochirus and 6 Largemouth Bass) from 3 out of the 4 lakes using a qPCR assay. Of the collected environmental samples, all 4 lakes tested positive for Lactococcus spp. in the soil samples, while 2 of the 4 lakes tested positive in the water samples through qPCR. Challenged Largemouth Bass did not show any signs of infection postinjection throughout the challenge period. Rainbow Trout infected with L. petauri showed clinical signs within 3 dpc and presented a significantly higher cumulative mortality (62.4%; p < 0.0001) at 14 dpc when compared to L. garvieae (0%) and L. formosensis (7.5%) treatments. Conclusion: The study suggests that qPCR can be used for environmental DNA monitoring of Lactococcus spp. and demonstrates virulence diversity between the etiological agents of piscine lactococcosis. Impact statementSalmonids are a keystone species in the Pacific Northwest, given their key role in nutrient cycling and as a vital food source for humans and animals. Gaining a better understanding of the distribution, prevalence, virulence, and diversity of emerging pathogens in wild and captive fish is important for the development of containment and preventative protocols.
- Subjects
CALIFORNIA; RAINBOW trout; LACTOCOCCUS; LARGEMOUTH bass; FISH farming; BLUEGILL; KEYSTONE species
- Publication
Journal of Aquatic Animal Health, 2023, Vol 35, Issue 3, p187
- ISSN
0899-7659
- Publication type
Article
- DOI
10.1002/aah.10188