Vector potential of the salmon louse Lepeophtheirus salmonis in the transmission of infectious haematopoietic necrosis virus (IHNV)

Abstract

To better understand the role of vector transmission of aquatic viruses, we established an in vivo virus−parasite challenge specifically to address (1) whether Lepeophtheirus salmonis can acquire infectious haematopoietic necrosis virus (IHNV) after water bath exposure or via parasitizing infected Atlantic salmon Salmo salar and if so, define the duration of this association and (2) whether L. salmonis can transmit IHNV to naïve Atlantic salmon and whether this transmission requires attachment to the host. Salmon lice which were water bath-exposed to 1 × 10 5 plaque-forming units (pfu) ml −1 of IHNV for 1 h acquired the virus (2.1 × 10 4 pfu g ) and remained viruspositive for 12 h. IHNV-positive salmon lice generated through water bath exposure or after parasitizing infected Atlantic salmon successfully transmitted IHNV, resulting in 76.5 and 86.6% of the exposed Atlantic salmon testing positive for IHNV, respectively. In a second experiment, only salmon lice that became IHNV-positive through water bath exposure transmitted IHNV to 20% of the naïve fish, and no virus was transmitted when IHNV-infected salmon lice were cohabitated but restrained from attaching to naïve fish. Under laboratory conditions, adult L. salmonis can acquire IHNV and transmit it to naïve Atlantic salmon through parasitism. However, the ephemeral association of IHNV with L. salmonis indicates that the salmon louse act as a mechanical rather than a biological vector or reservoir. 97: 155-165, 2011 156 ing the last epidemic (2001−2003) the average cumulative mortality of Atlantic salmon on infected farms was 58% (Saksida 2006), highlighting the significant economic cost of this disease. KEY WORDS: Sea lice · Lepeophteirus salmonis · Infectious heamatopoietic necrosis virus (IHNV) · Disease vector · Virus transmission · Atlantic salmon · Salmo salar Resale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESSDis Aquat OrgQuestions concerning the epidemiology of IHNV, such as the source of infection, mode of transmission, and mechanism that perpetuates the virus among salmonid populations, are yet to be fully addressed (Bootland & Leong 1999). Laboratory studies have clearly demonstrated water exposure as an effective mode of IHNV transmission to both Pacific and Atlantic salmon in salt-and freshwater (Traxler et al. 1993, Wolf 1988. Moreover, epidemiological investigation of the spatial and temporal occurrence of IHNV in saltwater-farmed Atlantic salmon suggest that waterborne transmission may have played a role in the spread of virus between farms located in close proximity to each other (Saksida 2006). However, alternative modes of IHNV transmission, including the potential for transfer by aquatic invertebrates, cannot be discounted.The topic of piscine ectoparasites as vectors for pathogens has been reviewed by Cusack & Cone (1986), focusing on tissue feeding species with monoxenous life cycles. The authors hypothesize that while moving between hosts such species may contribute to dis...

Parasitism perturbs the mucosal microbiome of Atlantic Salmon

“…ref. 33). Vibrio , a genus comprising several major fish pathogens6, amongst other commensal taxa, was highly abundant in louse samples, although also present among fish and environmental samples in test and control tanks.…”

Investigations on the role of the salmon louse, Lepeophtheirus salmonis (Caligidae), as a vector in the transmission of Aeromonas salmonicida subsp. salmonicida

“…A study by Jakob et al . () was conducted in parallel to the present study and they also reported dose and exposure time as key determinants of longevity of IHNV associated with L. salmonis ; however, that association was more ephemeral (12–24 h). Similarly, Oelckers et al .…”

“…Similarly, Jakob et al . () observed successful transmission of IHNV via L. salmonis when it was able to attach to a host, but virus transmission was not detected when the parasites were confined within a fine mesh box preventing attachment. A similar experiment was conducted (using the same mesh constraint) in the present study, with similar results, but the data were not included due to low sample size associated with tank space logistic constraints.…”

“…Similarly, Elgendy, Abdelsalam & Moustafa () have isolated Photobacterium damselae from Caligus elongatus parasitizing sea bass ( Dicentrarchus labrax ). Jakob, Barker & Garver () were the first to provide experimental evidence that adult L. salmonis can act as vectors of infectious haematopoietic necrosis virus (IHNV) and transmit it to naïve Atlantic salmon ( Salmo salar L.) through parasitism. Recently, Oelckers et al .…”

Caligus rogercresseyi: posible vector en la transmision horizontal del virus de la anemia infecciosa del salmon (ISAv)

“…La tasa de mortalidad más alta (86%) se presentó en los Caligus recién extraídos de los peces portadores del virus ISA, luego con aquellos Caligus que permanecieron 12 h en el laboratorio (76% de mortalidad) y finalmente con los peces que fueron infestados con Caligus que permanecieron en el laboratorio por 48 h (45% de mortalidad). En salmón del Atlántico infestado con L. salmonis portadores de IHNV se observó que hay una mayor mortalidad de los peces a medida que la carga viral de los parásitos es mayor, ya que es retenida por más tiempo al interior del parásito (Jacob et al, 2011).…”