Abstract

Phocine herpesvirus-1 (PhHV-1) is an important pathogen of harbor seals (Phoca vitulina), causing clinical disease and contributing to mortality in neonatal harbor seals in the wild and in rehabilitation centers in both the Atlantic and Pacific Oceans.³ Treatment of people and cats for closely-related human herpesvirus (HSV) and feline alpha herpesvirus (FeHV-1) respectively with L-lysine has shown promising results, suggesting that similar treatment should be investigated for harbor seals infected with PhHV-1.^1,2,4 L-lysine has been demonstrated to inhibit herpes viral activity by blocking host absorption of arginine, which is essential for HSV and FeHV-1 replication. Although the exact mechanism of action is unknown, it is hypothesized that L-lysine reduces viral replication by acting as an analog of arginine or by competing with arginine for cellular transport mechanisms, or both.⁵ Oral administration of L-lysine to FeHV-1 infected cats has been associated with significant reduction in viral shedding and decrease in the severity of clinical signs.^4,5 A reduction of PhHV-1 shedding could significantly slow or decrease virus spread in harbor seal rehabilitation facilities, potentially allowing time for pups to recover from existing medical problems before being exposed to the virus.

A study was therefore made to determine the in vivo effects of L-lysine on PhHV-1 infection, arginine absorption, and general health of stranded harbor seal pups undergoing rehabilitation. Five harbor seal pups were given oral L-lysine supplements for a minimum of 58 days at a ratio of approximately 2.25g/kg diet. Serum levels of L-arginine and L-lysine in this group of seals were then compared with a control group of five harbor seal pups that had not been given L-lysine supplements. Amino acid analysis at the end of the test period showed that the mean ratio of L-lysine to L-arginine in the treatment group (1.52) was not significantly different from the control group (1.54, t-test, p=0.93). All animals in the control group and L-lysine supplemented group tested positive for PhHV-1 antibodies at the end of the study period. It would therefore appear that L-lysine supplementation at a dose of 2.25g/kg diet does not trigger a reduction in L-arginine levels in harbor seals nor prevent infection with PhHV-1.

References

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