Abstract

Over a five day period in late October of 1997 five hundred marine birds, predominately western grebes (Aechmophorus occidentalis), Clark's grebes (A. clarkii ), common loons (Gavia immer) and surf and white-winged scoters (Melanitta perspicillata and M. fusca ), became fouled with a nonpetroleum oil. This product appeared nontoxic, but caused water saturation and hypothermia, as well as hypoglycemia and shock. Significant numbers of affected birds that were necropsied showed gross and/or histologic evidence of enteritis, septicemia, or pneumonia and airsacculitis, and four species of salmonella were isolated from one or more tissues: Salmonella typhimurium, S. anatum, S. saint paul and S. thompson.

Salmonella typhimurium was isolated from air sac, lung, liver and/or gastrointestinal tract of several birds with gross or histologic evidence of enteritis, bacterial pneumonia or sepsis. Salmonella typhimurium sometimes occurred in air sac infections and pneumonia in combination with Pseudomonas aeruginosa or Aspergillus fumigatus, especially in loons. Salmonella isolates other than S. typhimurium were less frequently associated with the above lesions. Additional salmonella isolates were obtained from cloacal swabs from clinically normal birds, as well as occasional surveillance swabs from work surfaces and other sites within the rehabilitation facility. Pending data includes comparison cultures of spleen, lung or air sac, ileum and proventriculus from eleven frozen-thawed birds that were picked up at the site of the spill and never entered the rehabilitation facility, as well as cultures from a limited number of freshly dead birds from an unrelated, geographically distinct oil spill off the California coast. A further complication was that many of the birds, especially loons, were in poor nutritional condition at the time of oiling. The combination of physical fouling with oil and acute stress due to recent migration or molt in the various species affected, combined with bacterial and fungal infections resulted in many birds, particularly loons, being euthanized, with a release rate of approximately 50%. The source of the oil may be rancid fish, which are commonly, but illegally dumped when not marketable.

Acknowledgements

The authors wish to thank U.C. Davis veterinary pathologists, residents and students, as well as volunteers from the community who assisted with necropsy of oiled birds.