Infectious diseases have the potential to play a role in the decline of threatened wildlife populations, as well as negatively affect their long-term viability, but determining which infectious agents present risks can be difficult. The southern resident killer whale, Orcinus orca, population is endangered and little is known about infectious diseases in this species. Using available reference literature, we identified 15 infectious agents (bacteria, viruses, and fungi) reported in free-ranging and captive killer whales, as well as 28 additional infectious agents reported in free-ranging and captive odontocete species sympatric to southern resident killer whales. Infectious agents were scored as having a high, medium, or low ability to affect fecundity or reproductive success, to cause disease in individual animals, and to cause epizootics. Marine Brucella spp., cetacean poxvirus, cetacean morbilliviruses, and herpesviruses were identified as high priority pathogens that warrant further study. Using identified pathogens to develop a standardized necropsy and disease testing protocol for southern resident killer whales and sympatric odontocetes will improve future efforts to better understand the impacts of priority and non-priority infectious agents on southern resident killer whales. This model can be used to evaluate potential infectious disease risks in other threatened wildlife populations.
Feces of harbor seals (Phoca vitulina richardsi) and hybrid glaucous-winged/western gulls (Larus glaucescens / occidentalis) from Washington State’s inland marine waters were examined for Giardia and Cryptosporidium spp. to determine if genotypes carried by these wildlife species were the same genotypes that commonly infect humans and domestic animals. Using immunomagnetic separation followed by direct fluorescent antibody detection, Giardia spp. cysts were detected in 42% of seal fecal samples (41/97). Giardia-positive samples came from 90% of the sites (9/10) and the prevalence of positive seal fecal samples differed significantly among study sites. Fecal samples collected from seal haulout sites with over 400 animals were 4.7 times more likely to have Giardia spp. cysts than samples collected at smaller haulout sites. In gulls, a single Giardia sp. cyst was detected in 4% of fecal samples (3/78). Cryptosporidium spp. oocysts were not detected in any of the seals or gulls tested. Sequence analysis of a 398 bp segment of G. duodenalis DNA at the glutamate dehydrogenase locus suggested that 11 isolates originating from seals throughout the region were a novel genotype and 3 isolates obtained from a single site in south Puget Sound were the G. duodenalis canine genotype D. Real-time TaqMan PCR amplification and subsequent sequencing of a 52 bp small subunit ribosomal DNA region from novel harbor seal genotype isolates showed sequence homology to canine genotypes C and D. Sequence analysis of the 52 bp small subunit ribosomal DNA products from the 3 canine genotype isolates from seals produced mixed sequences at could not be evaluated.
In the Florida Panhandle region, bottlenose dolphins (Tursiops truncatus) have been highly susceptible to large-scale unusual mortality events (UMEs) that may have been the result of exposure to blooms of the dinoflagellate Karenia brevis and its neurotoxin, brevetoxin (PbTx). Between 1999 and 2006, three bottlenose dolphin UMEs occurred in the Florida Panhandle region. The primary objective of this study was to determine if these mortality events were due to brevetoxicosis. Analysis of over 850 samples from 105 bottlenose dolphins and associated prey items were analyzed for algal toxins and have provided details on tissue distribution, pathways of trophic transfer, and spatial-temporal trends for each mortality event. In 1999/2000, 152 dolphins died following extensive K. brevis blooms and brevetoxin was detected in 52% of animals tested at concentrations up to 500 ng/g. In 2004, 105 bottlenose dolphins died in the absence of an identifiable K. brevis bloom; however, 100% of the tested animals were positive for brevetoxin at concentrations up to 29,126 ng/mL. Dolphin stomach contents frequently consisted of brevetoxin-contaminated menhaden. In addition, another potentially toxigenic algal species, Pseudo-nitzschia, was present and low levels of the neurotoxin domoic acid (DA) were detected in nearly all tested animals (89%). In 2005/2006, 90 bottlenose dolphins died that were initially coincident with high densities of K. brevis. Most (93%) of the tested animals were positive for brevetoxin at concentrations up to 2,724 ng/mL. No DA was detected in these animals despite the presence of an intense DA-producing Pseudo-nitzschia bloom. In contrast to the absence or very low levels of brevetoxins measured in live dolphins, and those stranding in the absence of a K. brevis bloom, these data, taken together with the absence of any other obvious pathology, provide strong evidence that brevetoxin was the causative agent involved in these bottlenose dolphin mortality events
Bacterial cultures collected over 12 yr from stranded harbor seal (Phoca vitulina) pups and weanlings located in the North Puget Sound and San Juan Islands region of Washington were analyzed retrospectively to determine the most common pathogenic isolates and to describe their antimicrobial resistance patterns. Culture attempts (n = 58) from wounds, umbilici, ears, conjunctiva, nares, oral lesions, and feces yielded 134 pathogenic isolates that represented 17 genera. The majority of isolates were Gram-negative (n = 87; 65%) and of the tested isolates were most susceptible to amikacin (n = 76; 99%) and gentamicin (n = 76; 97%) and least susceptible to ampicillin (n = 76; 26%). Of the Gram-positive isolates tested (n = 29), all were susceptible to amoxicillin/clavulanic acid. The most frequent isolates were Escherichia coli(17%), β-hemolytic Streptococcus spp. (15%), Enterococcus spp. (11%), and Pseudomonas aeruginosa (11%), with all four exhibiting resistance to more than 50% of the antimicrobials tested. The variety of organisms isolated, the variation in either Gram-negative or Gram-positive predominance, and the multiple drug resistance patterns observed suggest that when treating stranded harbor seals, culture and sensitivity testing are warranted and that antibiotic therapy should be based on results.