Seroprevalence of Toxoplasma gondii in mainland and sub-Antarctic New Zealand sea lion (Phocarctos hookeri) populations

Abstract

AIMS: To investigate the seroprevalence of antibodies to Toxoplasma gondii in New Zealand sea lions (Phocarctos hookeri), as a potential contributor to reproductive failure.

METHODS: Archived sera were sourced from New Zealand sea lions from two recolonising mainland populations in the Otago Peninsula (n=15) and Stewart Island (n=12), as well as a declining population at Enderby Island (n=28) in the New Zealand sub-Antarctic. Sera were tested for antibodies to T. gondii using a commercially available ELISA (with samples considered positive if the sample to positive ratio was >30%), and latex agglutination test (LAT; with titres ≥1:32 considered positive). Western blot analysis was used to validate the results of a subset of 14 samples.

RESULTS: Five samples from sea lions in mainland locations were confirmed positive for antibodies to T. gondii. Two adult females exhibited high LAT antibody titres (min 1:2048, max 1:4096) on both occasions when sampled 1 and 2 years apart, respectively. No animals from Enderby Island were seropositive.

CONCLUSIONS: Toxoplasma gondii infection is unlikely to be a major contributor to poor reproductive success in New Zealand sea lions. However, continued surveillance is pertinent to assess subclinical and clinical impacts of the parasite on these threatened populations. The commercial tests evaluated here, with further species-specific threshold refinement could provide a fast, inexpensive and reliable indicator of T. gondii exposure in New Zealand sea lions.

KEY WORDS:

• ELISA
• latex agglutination test
• Phocarctos hookeri
• pinniped
• Toxoplasma gondii
• western blot

Acknowledgments

This project was funded in part by the IVABS Research Fund, Massey University. The data presented in this paper were collected under permit from the New Zealand Department of Conservation. The authors wish to thank the teams involved with collecting samples in the field.

Notes

1 B.L. Chilvers, Department of Conservation, Wellington, New Zealand.

2 B. Lenting, Veterinary Resident in Avian, Wildlife and Zoo Animal Health, Massey University, Palmerston North, New Zealand.

3 W.D. Roe, Veterinary Pathologist, Massey University, Palmerston North, New Zealand.