C. LeAnn White

Spatial variation in risk and consequence of Batrachochytrium salamandrivorans introduction in the USA.

A newly identified fungal pathogen, Batrachochytrium salamandrivorans(Bsal), is responsible for mass mortality events and severe population declines in European salamanders. The eastern USA has the highest diversity of salamanders in the world and the introduction of this pathogen is likely to be devastating. Although data are inevitably limited for new pathogens, disease-risk assessments use best available data to inform management decisions. Using characteristics of Bsalecology, spatial data on imports and pet trade establishments, and salamander species diversity, we identify high-risk areas with both a high likelihood of introduction and severe consequences for local salamanders. We predict that the Pacific coast, southern Appalachian Mountains and mid-Atlantic regions will have the highest relative risk from Bsal. Management of invasive pathogens becomes difficult once they are established in wildlife populations; therefore, import restrictions to limit pathogen introduction and early detection through surveillance of high-risk areas are priorities for preventing the next crisis for North American salamanders.

PATHOGEN EXPOSURE AND BLOOD CHEMISTRY IN THE WASHINGTON, USA POPULATION OF NORTHERN SEA OTTERS (ENHYDRA LUTRIS KENYONI)

Abstract Northern sea otters (Enhydra lutris kenyoni) from Washington State, United States were evaluated in 2011 to determine health status and pathogen exposure. Antibodies to Brucella spp. (10%) and influenza A virus (23%) were detected for the first time in this population in 2011. Changes in clinical pathology values (serum chemistries), exposure to pathogens, and overall health of the population over the last decade were assessed by comparing 2011 data to the data collected on this population in 2001–2002. Several serum chemistry parameters were different between study years and sexes but were not clinically significant. The odds of canine distemper virus exposure were higher for otters sampled in 2001–2002 (80%) compared to 2011 (10%); likelihood of exposure significantly increased with age. Prevalence of exposure to Sarcocystis neurona was also higher in 2001–2002 (29%) than in 2011 (0%), but because testing methods varied between study years the results were not directly comparable. Exposure to Leptospira spp. was only observed in 2001–2002. Odds of Toxoplasma gondii exposure were higher for otters sampled in 2011 (97%) than otters in 2001–2002 (58%). Substantial levels of domoic acid (n = 2) and saxitoxin (n = 2) were found in urine or fecal samples from animals sampled in 2011. No evidence of calicivirus or Coxiella burnetii exposure in the Washington population of northern sea otters was found in either 2001–2002 or 2011. Changes in exposure status from 2001–2002 to 2011 suggest that the Washington sea otter population may be dealing with new disease threats (e.g., influenza) while also increasing their susceptibility to diseases that may be highly pathogenic in naïve individuals (e.g., canine distemper).

Serologic evidence of influenza A(H1N1)pdm09 virus infection in northern sea otters.

To the Editor: Sporadic epizootics of pneumonia among marine mammals have been associated with multiple animal-origin influenza A virus subtypes (1–6); seals are the only known nonhuman host for influenza B viruses (7). Recently, we reported serologic evidence of influenza A virus infection in free-ranging northern sea otters (Enhydra lutris kenyoni) captured off the coast of Washington, USA, in August 2011 (8). To investigate further which influenza A virus subtype infected these otters, we tested serum samples from these otters by ELISA for antibody-binding activity against 12 recombinant hemagglutinins (rHAs) from 7 influenza A hemagglutinin (HA) subtypes and 2 lineages of influenza B virus (Technical Appendix Table 1). Estimated ages for the otters were 2–19 years (Technical Appendix Table 2); we also tested archived serum samples from sea otters of similar ages collected from a study conducted during 2001–2002 along the Washington coast (9). Of the 30 sea otter serum samples collected during 2011, a total of 21 (70%) had detectable IgG (>200) for rHA of influenza A(H1N1)pdm09 virus (pH1N1) strain A/Texas/05/2009. Four of 7 serum samples that showed IgG ≥6,400 against pH1N1 rHA also showed low cross-reactivity (IgG 200) against rHA of A/Brisbane/59/2007, a previous seasonal influenza A(H1N1) virus (Figure, panel A; Technical Appendix Table 1). No IgG was detected in any samples for any of the other 11 rHAs tested (IgG ≤100), and the sea otter serum samples collected during 2001–2002 did not react with any of the rHAs tested, including pH1N1 (IgG ≤100; Figure, panel A). Figure Results of ELISA and hemagglutination inhibition (HI) testing for influenza viruses in serum samples from northern sea otters captured off the coast of Washington, USA, during studies conducted in August 2011 (n = 30) and 2001–2002 (n = 21). A) ... Next, we tested serum samples by using a hemagglutination inhibition (HI) assay with whole influenza virus to detect strain-specific antibodies that inhibit receptor binding. Of the 30 samples collected during 2011, a total of 22 (73%) showed HI antibody titers of ≥40 against pH1N1 virus. Titers against all other human and avian viruses tested were ≤10 for all samples by HI assay using turkey red blood cells (RBCs) (Figure, panel B; Technical Appendix Table 3). No influenza A or B virus–specific HI antibodies were detected in the samples collected during 2001–2002 (data not shown). Although nasal swab specimens were collected from sea otters in the 2011 study, all specimens were negative for influenza virus by testing in embryonated eggs and by real-time PCR for detection of influenza A viral RNA (data not shown). These results suggest that sea otters were infected with influenza A virus sometime before the August 2011 sample collection date. Although none of the 2011 samples showed HI titers to influenza A/duck/New York/96 (H1N1) virus (dk/NY/96) by testing using turkey RBCs (Technical Appendix Table 2), titers against this strain were detected when using horse RBCs, which is a more sensitive means for the detection of mammalian antibodies against some avian influenza subtypes (10). Of the 22 samples that had HI titers >40 to pH1N1 virus, 16 also had HI titers >40 against dk/NY/96 by horse RBC HI assay (Technical Appendix Table 2). However, titers against this strain were on average ≈4–8-fold lower than those for the pH1N1 virus strain, which suggests that that the titers against dk/NY/96 were the result of serologic cross-reactivity with avian- and swine-origin pH1N1 viruses. To further test for cross-reactivity, 4 sea otter serum samples were adsorbed with purified pH1N1 and dk/NY/96 virions. Adsorption with pH1N1, but not dk/NY/96, removed HI antibodies to pH1N1, whereas adsorption with either virus removed HI antibodies against dk/NY/96 (Technical Appendix Table 4). A comparison of amino acid sequences comprising the known HA antigenic sites on the pH1N1 structure confirmed high sequence identity and structural similarity with dk/NY/96 HA in Sa (12/13 aa residues) and Sb (8/12 aa residues) antigenic sites (data not shown). These results indicate that HI antibodies detected in sea otters are the result of pH1N1 virus infection but cross-react with the avian influenza A(H1N1) virus. Although we cannot exclude the possibility that sea otters were infected with classical swine influenza A(H1N1) virus, which shares high HA genetic and antigenic similarity with pH1N1 virus, our serologic evidence is consistent with isolation of pH1N1 virus from northern elephant seals (1). Therefore, we conclude that these sea otters were infected with pH1N1 virus. The origin and transmission route of pH1N1 virus infection in sea otters remain unknown. Potential contact between northern elephant seals and sea otters is one possibility; elephant seals’ summer feeding ranges and breeding areas along the Northeast Pacific coast overlap with areas where the Washington sea otter population is distributed (1). In conclusion, our results show that sea otters are susceptible to infection with influenza A virus and highlight the complex nature of interspecies transmission of influenza viruses in the marine environment. Further surveillance, especially in other sea otter populations, is required to determine virus origin, potential pathogenesis, and consequences for the marine ecosystem. Technical Appendix: Titers for influenza A and B viruses detected in serum samples from northern sea otters captured off the coast of Washington, USA, during studies conducted in August 2011. Click here to view.(52K, pdf)

SPATIAL AND TEMPORAL PATTERNS OF AVIAN PARAMYXOVIRUS-1 OUTBREAKS IN DOUBLE-CRESTED CORMORANTS (PHALACROCORAX AURITUS) IN THE USA

Abstract Morbidity and mortality events caused by avian paramyxovirus-1 (APMV-1) in Double-crested Cormorant (DCCO; Phalacrocorax auritus) nesting colonies in the US and Canada have been sporadically documented in the literature. We describe APMV-1 associated outbreaks in DCCO in the US from the first reported occurrence in 1992 through 2012. The frequency of APMV-1 outbreaks has increased in the US over the last decade, but the majority of events have continued to occur in DCCO colonies in the Midwestern states. Although morbidity and mortality in conesting species has been frequently reported during DCCO APMV-1 outbreaks, our results suggest that isolation of APMV-1 is uncommon in species other than DCCO during APMV-1 outbreaks and that the cause of mortality in other species is associated with other pathogens. Populations of DCCO do not appear to have been significantly affected by this disease; however, because at least 65% of the APMV-1 outbreaks in DCCO in the US have involved APMV-1 strains classified as virulent to poultry (virulent Newcastle disease virus), its persistence and increased occurrence in DCCO warrants continued research and surveillance.