In this issue: Finding sand lance hidden in salmon data – Should we be concerned when a seal gives birth to a two-headed pup? – How disease could impact the Salish Sea – Four new SeaDoc board members – SeaDoc-funded scientist honored by Seattle Aquarium – Serge Dedina speaks February 24th
This is a transcript of a talk given on March 27, 2015 to the Puget Sound Partnership Leadership Council by Joe Gaydos of the SeaDoc Society and Linda Rhodes, Ph.D of the Marine Microbes & Toxins Program of NOAA Fisheries Northwest Science Center.
Did you know that diseases like canine distemper virus can spread from domestic dogs to wildlife? It’s a problem around the world, with infections in lions, tigers, hyenas, ferrets, North American river otters, raccoons, bears, and more. Two seal species, Baikal and Caspian seals, have also experienced distemper outbreaks.
In January 2015, Joe Gaydos presented a paper titled Canine Distemper in Wildlife: How Private Practitioners Can Help at the North American Veterinary Conference in Orlando, Florida.
Proper vaccination of domestic animals can help contain outbreaks. A similar virus, Rinderpest, which circulated between wild and domestic animals in Africa, was eradicated after a massive campaign to vaccinate domestic livestock.
In 2008, SeaDoc published a paper investigating whether the Giardia and Cryptosporidium parasites in harbor seals in the Salish Sea were connected with canine parasites.
Video of lion with distemper:
SPILLOVER FROM DOMESTIC ANIMALS TO WILDLIFE
There are multiple documented cases where CDV has been transmitted from domestic dogs to wildlife and additional instances where CDV in wildlife is believed to have come from domestic dogs. Both of the 1987 and 2000 CDV epizootics in Baikal and Caspian seals, respectively, likely originated from CDV epizootics in domestic dogs. Viral homology of the CDV H gene in a CDV-infected wild wolf and domestic dog suggest that domestic dogs were responsible for transmitting CDV to wild wolves in Portugal in 2007-2008.6 Between 2001 and 2003 an epizootic of CDV in black-backed jackals and other wild carnivores in Namibia was attributed to domestic dogs based on viral sequence data from the P and H genes. A CDV epizootic in domestic dogs in Kenya between 1990 and 1992 is believed to have been responsible for the disappearance of known packs of African wild dogs in the region. Also, it has been hypothesized that domestic dogs could have transmitted CDV to wild giant pandas in Wolong Reserve, China.
VACCINE-INDUCED DISEASE IN WILDLIFE
Vaccine-induced canine distemper has been demonstrated in numerous wildlife species including the African wild dog, black-footed ferret, kinkajou, lesser panda, maned wolf, and gray fox. Suspected vaccineinduced canine distemper has occurred in raccoons, fennec fox, and the South American bush dog. All have been associated with administration of various modified live vaccines.
Populations of at least 20 asteroid species on the Northeast Pacific Coast have recently experienced an extensive outbreak of sea-star (asteroid) wasting disease (SSWD). The disease leads to behavioral changes, lesions, loss of turgor, limb autotomy, and death characterized by rapid degradation (“melting”). Here, we present evidence from experimental challenge studies and field observations that link the mass mortalities to a densovirus (Parvoviridae). Virus-sized material (i.e., <0.2 μm) from symptomatic tissues that was inoculated into asymptomatic asteroids consistently resulted in SSWD signs whereas animals receiving heat-killed (i.e., control) virus-sized inoculum remained asymptomatic. Viral metagenomic investigations revealed the sea star-associated densovirus (SSaDV) as the most likely candidate virus associated with tissues from symptomatic asteroids. Quantification of SSaDV during transmission trials indicated that progression of SSWD paralleled increased SSaDV load. In field surveys, SSaDV loads were more abundant in symptomatic than in asymptomatic asteroids. SSaDV could be detected in plankton, sediments and in nonasteroid echinoderms, providing a possible mechanism for viral spread. SSaDV was detected in museum specimens of asteroids from 1942, suggesting that it has been present on the North American Pacific Coast for at least 72 y. SSaDV is therefore the most promising candidate disease agent responsible for asteroid mass mortality.
In this issue: Learning more about stranded killer whales, marine bird declines featured in the news, thank you for supporting SeaDoc at our auction, Salish Sea book is coming soon, join SeaDoc for a once-in-a-lifetime Salish Sea trip, slideshow on coastal cutthroat trout, SeaDoc presents on wildlife diseases.
Eelgrass (Zostera marina) plays a key role in the health of the Salish Sea ecosystem. It stabilizes sediments, reduces the impact of wave action, provides habitat, and is an important nursery and foraging area for multiple species, some of which are endangered.
SeaDoc’s involvement in eelgrass issues goes back to 2003, when we convened a meeting of eelgrass experts, resource managers, and land-use specialists to analyze the sudden disappearance of 35 acres of eelgrass in San Juan Island’s Westcott Bay.
Eelgrass can be damaged by pollutants, by shading from docks and structures, and by physical damage from improper anchoring or badly placed moorings. It’s also susceptible to disease, particularly from a slime mold-like organism called Labyrinthula zosterae. And it’s no small threat. This disease wiped out 90% of the eelgrass along the Atlantic coasts of North America and Europe in the 1930s.
We know that the organism is found in the Salish Sea, but the mere presence of a pathogen does not always mean disease. So what are the other factors? A recent publication by Maya Groner and numerous colleagues (supported in part by SeaDoc) used field surveys and experimental manipulations to find out how the age of eelgrass leaves impacts disease prevalence.
The upshot: mature beds and shallow eelgrass beds could be especially susceptible to outbreaks of wasting disease.
View the publication here:
Photo from NOAA Photo Library via Flickr.
Many marine pathogens are opportunists, present in the environment, but causing disease only under certain conditions such as immunosuppression due to environmental stress or host factors such as age. In the temperate eelgrass Zostera marina, the opportunistic labyrinthu-lomycete pathogen Labyrinthula zosterae is present in many populations and occasionally causes severe epidemics of wasting disease; however, risk factors associated with these epidemics are unknown. We conducted both field surveys and experimental manipulations to examine the effect of leaf age (inferred from leaf size) on wasting disease prevalence and severity in Z. marina across sites in the San Juan Archipelago, Washington, USA. We confirmed that lesions observed in the field were caused by active Labyrinthula infections both by identifying the etiologic agent through histology and by performing inoculations with cultures of Labyrinthula spp. isolated from observed lesions. We found that disease prevalence increased at shallower depths and with greater leaf size at all sites, and this effect was more pronounced at declining sites. Experimental inoculations with 2 strains of L. zosterae confirmed an increased susceptibility of older leaves to infection. Overall, this pattern suggests that mature beds and shallow beds of eelgrass may be especially susceptible to outbreaks of wasting disease. The study highlights the importance of considering host and environmental factors when evaluating risk of disease from opportunistic pathogens.
At the 2014 North American Veterinary Conference, in Orlando, Florida, Joe Gaydos presented on Salmonella in wildlife. About 10% of the Salmonella outbreaks between 2006 and 2013 were caused by wild animals, and most of these were caused by reptiles and amphibians.
Salmonella infection can be prevalent in wild birds, and has been seen in many wild mammal species including white-tailed deer, raccoons, and river otters.
Relatively little is known about Salmonella in free-ranging marine mammals. It has been isolated from harbor porpoise (Phocoena phocoena), a killer whale (Orcinus orca), sea otters (Enhydra lutris nereis), northern elephant seals (mirounga angustirostris), California sea lions (Zalophus californianus), Northern fur seals (Callorhinus ursinus), and harbor seals (Phoca vitulina). Far more isolations have been made than actual documentation of disease. Salmonella Newport-associated septicemia has been documented in a harbor porpoise and a killer whale. Salmonella also has been isolated from marine birds such as Western gulls (Larus occidentalis). While one study found prevalence of Salmonella in 40% of California sea lion pups and 33% of northern fur seal pups on San Miguel Island, the prevalence in most marine wildlife populations is unknown but probably highly variable.
Download a copy of the paper: Salmonella in Wildlife by J. Gaydos