Overview
Fish and wildlife are susceptible to naturally-occurring and introduced diseases caused by a variety of pathogens, including viruses, bacteria, fungi, prions, and protozoans. Animals exposed to pathogens may exhibit illness or death or show no signs of disease if the pathogen is cleared by the animal’s immune system, or they may serve as carriers or reservoirs of the pathogen. In susceptible individuals and species, disease spreads quickly when large numbers of animals are concentrated naturally during migration, when they are artificially fed, or when they congregate during breeding or due to limited habitat. Emerging and novel diseases can have devastating effects on wildlife, human health, and local economies. Climate change may increase susceptibility of fish and wildlife to disease by altering ecosystem dynamics, increasing opportunities to spread disease, and raising animals’ stress response, potentially making them more susceptible to disease and illness if they become exposed. Although not a disease, ocean hypoxia and acidification may have similar effects on populations of some marine species (see the Oregon Nearshore Strategy).
People can help to prevent unnatural disease outbreaks by remembering not to feed wildlife, vaccinating pets, and providing and managing natural habitat. Licensed Oregon wildlife rehabilitators care for sick or injured wild animals with the goal of returning them to their natural habitat, and provide valuable educational information and outreach to the public. In addition, accredited Association of Zoos and Aquariums facilities in Oregon (e.g., Oregon Zoo, Wildlife Safari, Oregon Coast Aquarium) provide valuable public education, outreach, and conservation projects related to the health of Oregon’s fish and wildlife and their native habitats.
Endemic disease is a natural part of every ecosystem. However, introduced and emerging diseases not only threaten the balance of ecosystem health but can be very difficult and costly to eradicate once established. The best action to avoid unwanted disease outbreaks is prevention. The ODFW’s biologists, veterinarians, and wildlife administrators make every effort to protect the state’s fish and wildlife through surveillance, monitoring, training, response plans, policy, and regulation. Listed below are the diseases that present the greatest management concern or that present significant or recurring health risk to Oregon’s fish and wildlife. This list includes diseases that occur naturally or are endemic in Oregon, as well as diseases that are introduced or emerging. The list is not inclusive of all diseases identified in Oregon fish and wildlife.
Wildlife Diseases of Management COncern
| Disease or Disease-Causing Organism | Vulnerable Species | Conditions that Promote Disease Issues | Management Approaches |
|---|---|---|---|
| Ranavirus | All amphibians and reptiles | Conditions that weaken immune response (e.g., UV-B light, pesticides). Movement of infected animals. | Maintain high water quality. Investigate the natural distribution of ranavirus to determine if it is spreading to new areas. Avoid human-caused movement of amphibians and reptiles to new areas. |
| Chytrid skin fungus (Batrachochytrium dendrobatidis) | All amphibians, although some species may be more vulnerable | Conditions that weaken immune response (e.g., UV-B light, pesticides). Movement of infected animals. | Maintain high water quality. Investigate the natural distribution of chytrid fungus to determine if it is spreading to new areas. Avoid human-caused movement of amphibians to new areas. |
| Egg-destroying pathogen (Saprolegnia ferax, a watermold) | All amphibians, although some species may be more vulnerable | Conditions that weaken immune response (e.g., UV-B light, pesticides) | Maintain high water quality. Investigate the role of introduced fish in spread between water bodies. |
| Amphibian deformities (multiple legs and other deformities caused by a trematode, Ribeiroia sp.) | All amphibians, but seen most often in some frog species | High nutrient levels that increase densities of intermediate hosts (snails) | Maintain high water quality. Monitor incidence of amphibian deformities. Avoid human-caused movement of amphibians to new areas. |
| Septicemic cutaneous ulcerative disease | Aquatic native turtles | Movement of infected animals. Cause presently unknown but occurrence highest in headstart turtles. | Avoid human-caused movement of turtles to new areas. Continue research to identify cause and determine population impacts. |
| Avian cholera (caused by the bacterium Pasturella multocida) | Waterfowl especially, but can also impact gulls, terns, coots, and crows | Seen primarily in southern wetlands of state in winter from concentration of waterfowl during migration. Waterfowl concentrations increase when the amount of open water is reduced (e.g., during drought, freezing temperatures, or due to habitat loss). Freezing temperatures also increase vulnerability by weakening immune systems. | Maintain and restore wetland habitats important for migratory waterfowl. Manage major die-offs through carcass removal and appropriate disposal to reduce local point sources and minimize impacts to populations. |
| Bird feeder diseases (salmonellosis, mycoplasmal conjunctivitis, avian poxvirus, trichomoniasis) | Songbirds, primarily finch species | Concentration of birds at bird feeders. Contaminated feeder surfaces and fecal-contaminated bird food. | Conduct outreach regarding prevention methods. Implement sanitation measures at bird feeders or cessation of wild bird feeding. |
| Newcastle virus | Double-crested Cormorants, many bird species at risk | Occurs in breeding colonies along the Columbia River and Northwest coast. Appears to occur on an every other year cycle, typically in odd-numbered years (2013, 2015, etc. ). | Monitor and conduct surveillance of colonies. Work with wildlife rehabilitators to avoid and manage potential disease risk in facilities. |
| West Nile virus | Birds in the family Corvidae and sage-grouse, other bird species, some mammals (squirrels) | Conditions conducive for mosquito production and over-winter survival | Zoonotic disease passed by mosquito vectors. Reduce mosquito breeding areas in urban environments. Follow Centers for Disease Control and Prevention recommendations. Place warning guidance at wetland management areas. |
| Avian influenza (highly pathogenic) | Many wild bird species are hosts. Waterfowl and shorebirds are the principal hosts to highly pathogenic (HPAI H5, H7) strains; harbor seals may serve as hosts in marine habitats. | Waterfowl, shorebirds, and other wild bird species serve as hosts to most of the 144 strains of the virus. Mutated or highly pathogenic strains can have devastating impacts to the poultry industry and to human health, and may cause wild bird deaths. Poor bio-security in backyard ponds, with falconry birds, rehabilitation facilities, and hunt clubs can contribute to spread of avian influenza. | Monitor and conduct surveillance of captured or translocated birds, including waterfowl (duck banding), Mountain Quail, turkeys, grouse, and farmed game birds. Increase biosecurity education to landowners, poultry owners, falconers, rehabilitators, and hunt clubs. Consider HPAI surveillance in harbor seals during capture events and unusual mortality events. |
| Botulism (caused by a nerve toxin produced by the bacterium Clostridium botulinum) | Waterfowl and shorebirds | Associated with shallow wetland habitats during warm weather. Botulism can be made worse by fluctuating water levels. It is often associated with carcasses (waterfowl, fish kills). Fly larvae can bioconcentrate this toxin. | Manage water levels, flow, flushing, and changes at important migration areas to prevent botulism. Manage major die-offs by carcass removal and proper disposal to minimize further impacts to local populations. |
| Mycoses (diseases caused by fungi, including toxins produced by mold), Aspergillosis (aflatoxins) | Many bird species. Aspergillosis is most common in waterfowl, gulls, corvids, and raptors. | Transmitted from moldy corn or acquired from soil or damp organic materials. Stressed or diseased animals may have increased susceptibility. | Aspergillosis: Monitoring and surveillance. Minimize access to source sites, such as moldy silage piles. Manage major die-offs by carcass removal to minimize impacts to local populations. |
| Cryptococcus gattii | C. gattii has been identified in harbor porpoises, Dalls porpoises, Roosevelt elk, domestic animals, and humans along the coast and Willamette Valley. | Geographic and local environmental factors are important in development of infection. | Additional research is needed to understand the location of environmental hot spots. |
| Algal blooms (toxic) | Waterfowl and other wildlife species associated with contaminated water sources. Algal bloom toxins in marine habitat can affect shellfish safety for human consumption and cause disease in shorebirds and marine mammals. | Warmer, stagnant water bodies with high nutrient content, in particular, can cause anoxic conditions for fish and toxic algal blooms for avian and terrestrial species. Factors that influence harmful algal blooms in marine waters are not well understood. | Maintain good water quality, flushing, and flow. Reduce high nitrogen/phosphate/nutrient runoff. Manage major die-offs by carcass removal and appropriate disposal. Sample marine waters for levels of harmful algae present and to determine safety of shellfish for human consumption. |
| Rodent control poisons (anticoagulants, metal phosphides, hypercalcemia products, zinc phosphide toxicosis) | Non-target species, particularly raptors and wild canids and felids, geese and pasture-based migratory songbirds in the Willamette Valley | Application during high rodent population seasons and cycles, and when applied off-label by inappropriate methods of delivery and during periods identified as high-risk for non-target species. | Applicators must follow label restrictions for legal application and avoidance of primary and secondary toxicity to non-target species. |
| Canine distemper | Raccoons, foxes, skunks, coyotes, wolves, and seals | Observed in raccoon and fox populations when population densities are high. Spillover from domestic dogs can occur. Infected wildlife also put unvaccinated dogs at risk. | Continue to promote prevention (e.g., by not feeding raccoons). Use caution when moving nuisance raccoons. Promote vaccination programs in domestic pets. |
| Rabies | Bats, raccoons, skunks, foxes, wolves, and any mammalian species. Unvaccinated dogs and domestic cats are at highest risk. Human rabies is rare in the U.S. Bat strain rabies is the only documented variant identified in Oregon. | Handling of sick or dead bats, exposure of pets to sick bats or other wild mammals resulting in contact or a biting incident, and unvaccinated domestic pets can result in transmission. Bat strain rabies occurs naturally at very low prevalence levels (<1%) in bat populations in Oregon. In 2010, a spillover event occurred in the fox population in southwest Oregon. | Continue to promote vaccination programs in domestic pets. Conduct outreach and education to teach people to avoid sick wild mammals or those with unusual behavior. Follow zoonotic disease guidance by the Centers for Disease Control and Prevention. |
| Canine parvovirus (includes several closely-related viruses, such as feline panleucopenia) | Raccoons, foxes, coyotes, and wolves, principally. Canine parvovirus can infect unvaccinated domestic cats. | Exposure to unvaccinated dogs and domestic cats (e.g., outdoor cats, abandoned cats, and feral cat colonies) | Promote pet vaccination programs. Promote benefits to cats, wildlife, and people when cats are kept indoors. Discourage community feral cat colonies. |
| Leptospirosis | All mammalian wildlife but especially marine mammals (seals, sea lions, porpoises) | A multi-serotype bacterial disease transmitted from contaminated urine of infected animals | Conduct outreach regarding the importance of avoiding contact with sea lions and sea lion carcasses along Oregon's coast. Leptospirosis is considered a zoonotic disease. |
| Tularemia | All mammals but especially rodent and lagomorph species | Tularemia is generally transmitted through the bite of a flea or tick. This bacterial disease can be more prevalent when mammalian hosts occur at higher population densities. | Tularemia is a zoonotic disease with a worldwide distribution. Sick or deceased rodents or rabbits should not be handled without gloves and additional protective equipment. |
| Plague | Rodent species (particularly mice) can serve as hosts and can suffer high rates of mortality (i.e., prairie dogs). Many mammals are susceptible; canids are refractory. | Fleas act as vectors. Conditions are most conducive to transmission during high rodent population cycles. Birds, lagomorphs, and carnivores may maintain or disseminate the disease by transporting fleas or ticks or infected prey. | Plague is widespread in wild rodent populations west of the 100th meridian. Control can be achieved through an oral vaccination program or burrow dusting with insecticides. Plague is a zoonotic disease. |
| Notoedric mange | Western grey squirrels, northern and southern flying squirrels | Transmission is primarily through direct contact of affected and unaffected animals and transfer of the mite Notoedres centrifera. Increased squirrel densities associated with competition for sparse food resources can be conducive to spread. | Minimize artificial feeding and movement of animals. |
| Exotic biting lice (Cervicola (Damalinia) spp., Bovicola tibialis) | Black-tailed, white-tailed, and mule deer | Lice are passed through direct contact between deer and probably from common use of bedding sites. | Conduct public education to discourage congregating deer by feeding or baiting. Cervicola is widespread in the black-tailed deer population from Washington to central California. Bovicola is found in scattered pockets of mule deer in Oregon, Nevada, Idaho, Washington, and California. |
| Cervid adenoviral hemorrhagic disease | Black-tailed, white-tailed, and mule deer | Transmission is through direct nose to nose contact between infected and uninfected deer. Exposed animals may become diseased in acute or chronic state or mount an antibody response in the absence of disease. Outbreaks in deer fawns in rehabilitation facilities have resulted in high mortality. | Avoid movement of adult deer and deer fawns to unaffected populations or areas. Conduct public education to discourage congregating deer by feeding or baiting. Restrict rehabilitating deer fawns at facilities with consistent adenoviral hemorrhagic disease outbreaks. |
| Epizootic hemorrhagic disease | White-tailed deer are highly susceptible. Black-tailed and mule deer may also exhibit the disease. | Culicoides spp. gnats are the insect vectors of this virus. Drought and low water conditions with concentrations of susceptible animals at limited watering sites provide conditions conducive to amplification of the virus and disease outbreaks in riparian habitats. | Continue annual surveillance in previously affected areas (southwest Oregon). Conduct public education to discourage congregating deer by feeding or baiting. |
| Elk hoof rot disease (Treponema bacterial-associated syndrome) | Roosevelt elk | Found in northwest Oregon elk populations. Causal bacterial agent belongs to the genus Treponema. Wet pastures and environmental conditions are thought to facilitate Treponema-associated elk hoof rot disease. | Avoid movement and translocation of elk from infected areas. Consider research in novel habitat treatments. Continue monitoring with the aid of citizen science. |
| Respiratory disease in wild sheep | Rocky Mountain bighorn sheep, California bighorn sheep | Northwest Rocky Mountain populations are primarily affected. Mycoplasma ovipneumoniae and Manheimia and Pasteurella spp. respiratory pathogens are transmitted to wild sheep from domestic sheep and goats. This disease occurs primarily in northeast Hells Canyon populations of bighorn sheep shared with Washington and Idaho. | Maintain separation of wild and domestic sheep and goats. Implement management actions to enhance habitat and maintain or improve population densities. Support research designed to mitigate effects of respiratory disease on sheep populations. Consider population management manipulations of infected herds using adaptive management strategies. |
| Salmon poisoning disease. The disease in canids is caused by a rickettsial organism (Neorickettsia helminthoeca) present in a trematode parasite (Nanophyetus salmincola). | Salmonids and a restricted number of non-salmonid fish species acquire the rickettsial parasite, which infects a stream snail (Oxytrema silicula) commonly eaten by the fish. Canids and bears can then acquire the rickettsial infection upon eating infected fish. | This disease is primarily found in the Cascade Range and associated tributaries. Exposure of fish to the infective stage of the worm life cycle and increased snail populations promote the disease. | Educate pet owners about the potential risks for dogs eating parasitized salmon, clinical signs of the disease, and when to seek veterinary care for required antibiotic treatment. |
Fish DISEASES OF MANAGEMENT CONCERN
| Disease or Disease-Causing Organism | Vulnerable Species | Conditions that Promote Disease Issues | Management Approaches |
|---|---|---|---|
| Sea-star wasting-densovirus (Parvoviradae) associated with mortality | Many species of sea stars, urchins of concern | Unknown. Causes rapid degeneration of animal. Associated with high levels of mortality. Urchins carry disease but have not yet been detected expressing it. | Further research and monitoring are needed. |
| Infectious hematopoietic necrosis virus | Most salmonid stocks | Stress situations, such as spawning or adverse environmental conditions | Reduce movements of infected fish and track different isolates of the virus. |
| Erythrocytic inclusion body syndrome | Several salmonid stocks | Unknown, but condition depresses immune system and other diseases become patent | Nutrition may affect severity of infection. |
| Viral hemorrhagic septicemia virus | North American strain causes little mortality in salmonids but can cause high losses in marine species like herring, sardines, and mackerel. | Young immuno-incompetent fish and spawning adults. Fish spread the virus horizontally. Virus may be passed on to progeny. | Avoidance by limiting exposure. Monitor for the presence of the European strain which is much more virulent. |
| Infectious pancreatic necrosis virus | Most salmonid stocks and a few other marine species | Fish to fish transmission and vertically transmitted from parent to progeny | Avoidance by limiting exposure. Screen spawning adults for virus and cull eggs from positive parental groups. |
| White sturgeon iridovirus, white sturgeon herpesvirus | White sturgeon and possibly other related species | Likely vertically transmitted from parents to progeny. High stress environmental conditions may lead to outbreaks. | Limit transfer of known carriers. Examine fish and stock history. |
| Bacterial kidney disease caused by Renibacterium salmoninarum | Salmonid stocks | Exposure to infected fish and transferred within the egg from infected females | In hatcheries, reduce the pathogen by culling eggs from infected females and using antibiotic injections and feedings. |
| Columnaris disease caused by the bacterium Flavobacterium columnare | Freshwater fish, relatively uncommon in coldwater marine fish | Warm water conditions, exposure to other infected individuals | Where possible, augment water flows to increase quantity and decrease temperature. |
| Furunculosis caused by the bacterium Aeromonas salmonicida | Salmonid stocks, some other species | Exposure to infected fish | Use antibiotic treatments where possible. |
| External fungal infections (water molds) caused by multiple species of fungi | Most common in freshwater fish | Stress situations, such as spawning, low water, low temperature (particularly a rapid temperature drop for freshwater fish), and body injuries | Fungal spores ubiquitous and no possible control of environmental conditions. Educate about condition. |
| Tapioca disease, caused by the myxosporean parasite Henneguya salminicola | Several species but most noted in Chinook and coho salmon | Unknown. Rarely detrimental to fish but a concern for anglers due to cysts in flesh. | Provide education on the parasite and the safety of consuming flesh. |
| Ceratomyxosis caused by the myxosporean parasite Ceratomyxa shasta | Salmonid stocks | Exposure to infectious stage of parasite that originates in a worm. Warm, slow water and low flows can increase contact with agent. | Where possible, augment water flows to increase quantity and decrease temperature. |
| White spot caused by the protozoan Ichthyophthirius multifiliis | Freshwater fish | Exposure to infected individuals, warm water conditions | Where possible, augment water flows to increase quantity and decrease temperature. |
| Black spot caused by Strigeid trematodes (Neascus) | All fish but more common in warmwater species | Exposure to infected snails. Complex life cycle involving birds, increased snail populations. | Provide education on the source of the parasite and that it does not affect humans. |
| Yellow grub caused by Clinostomum marginatum | All fish but more common in warmwater species | Exposure to infected snails. Complex life cycle involving birds, increased snail populations. | Provide education on the source of the parasite and that it does not affect humans. |
| White grub caused by Posthodiplostomum minimum | All fish but more common in warmwater species | Exposure to infected snails. Complex life cycle involving birds, increased snail populations. | Provide education on the source of the parasite and that it does not affect humans. |
| Tapeworms caused by Proteocephalus sp., Diphyllobothrium sp., Bothriocephalus sp. | All fish | Ingestion of intermediate host carrying infectious stage of the parasite | Provide education on the source of the parasites and the proper handling of fish for consumption. Zoonotic potential. |
| Copepods, fish lice, and anchor worms caused by Salmincola sp., Argulus sp., Lernaea sp. | All fish | Exposure to infected individuals, low water conditions, or overpopulation | Where possible, augment water flows to increase quantity and decrease temperature. |
| NIX (nuclear inclusion X) | Razor clams | Unknown. Affects gill tissue (branchial epithelium). Associated with high levels of mortality in Washington. | Further research and monitoring are needed. |
| Trematode | Razor clams | Unknown. Found in the gonad. | Further research and monitoring are needed. |
| Domoic acid diatom (Pseudo-nitzschia sp.) | Birds and mammals | Unknown environmental conditions | Involve Oregon Department of Agriculture, National Oceanic and Atmospheric Administration, Oregon State University, and Oregon Department of Fish and Wildlife in research and monitoring. |
| Paralytic shellfish toxin -dinoflagellate | Birds and mammals | Unknown environmental conditions | Involve Oregon Department of Agriculture, National Oceanic and Atmospheric Administration, Oregon State University, and Oregon Department of Fish and Wildlife in research and monitoring. |
| Shrimp barnacle (Sylon sp.) | Pink shrimp (Pandalus jordani), spot prawns (Pandalus platyceros) | Unknown. Widely distributed in shrimp and prawns in Northern Hemisphere but only recently noted by Oregon shrimpers fishing in southern Washington. Parasite generally kills host. | Further research and monitoring are needed. |
| Needle disease-microsporidian (Nadelspora canceri) | Dungeness crab | Unknown. More prevalent in Dungeness crab living in bays and estuaries. Needle-shaped spores are found in the muscle. Can greatly increase crab mortality. | Further research and monitoring are needed. |
| Vibrio pathogen (Vibrio tubiashii) | Oysters and clams | Causes premature death in larvae. | Further research and monitoring are needed. |
| Parasitic isopod (Orthione griffenis) | Mud shrimp (Upogebia pugettensis) | Probable introduction from Asia. Gill parasite associated with population decline. | Further research and monitoring are needed. |
Emerging DISEASES OF MANAGEMENT CONCERN
| Disease or Disease-Causing Organism | Vulnerable Species | Conditions that Promote Disease Issues | Surveillance and Management Recommendations |
|---|---|---|---|
| Chronic wasting disease of cervids | Deer, elk, moose | A fatal neurological prion-associated disease transmitted via direct contact between infected and non-infected susceptible cervids through saliva, urine, and feces. Indirect contact infection is possible from long-term environmental contamination of susceptible animals. | Not presently identified in Oregon. Conduct surveillance of hunter-harvested animals and animals observed with clinical signs. Ban importation of live cervids and hunter-harvested neural tissues from wild cervids taken in affected states. |
| Meningeal worm (Parelaphostrongylus tenuis) | White-tailed deer. Moose, elk, caribou, mule deer, black-tailed deer, and antelope are aberrant hosts. | Non-pathogenic to white-tailed deer but causes severe neurologic signs and death in aberrant hosts. | Prevent movement of wild cervids from meningeal worm endemic areas. |
| Meningoencephalitis associated with Carnobacterium maltaromaticum-like bacteria | Juvenile salmon sharks | Unknown. Documented in juvenile salmon sharks breeding along the California coast during late summer and early fall. | Further research and monitoring are needed. |
| Morbillivirus (phocine and cetacean) in marine mammals | Seals, dolphins, whales | Unknown | A number of unusual mortality events documented along the eastern U.S. in dolphins. Further research and monitoring are needed. |
| Pigeon paramyxovirus (PPMV-1) | Pigeons and doves | Congregation of birds at feeders or watering sites promotes spread of the disease since it is spread via direct contact and feces. | Currently not identified in Oregon, but has caused massive die-offs of Eurasian Collared Doves in western states, such as Colorado, Arizona, and Montana. Surveillance and monitoring are needed. |
| Salamander chytrid fungus (Batrachochytrium salamandrivorans) | Salamanders, especially newts | Unknown. Globalization and lack of biosecurity, importation of infected species via the pet trade, and internet shipments of amphibians likely promote spread. | Maintain strict biosecurity and importation protocols. Evaluate novel biosecurity measures. Increase public awareness and education of risks to conservation, species impacts, and global health. Further research and monitoring are needed. |
| Snake fungal disease (Ophidiomyces ophiodiicola) | Fungal dermatitis in snake species currently in nine states, including Illinois, Florida, Massachusetts, Minnesota, New Jersey, New York, Ohio, Tennessee, and Wisconsin. | Unknown | Further research and monitoring are needed. |
| White-nose syndrome | Cave-dwelling, hibernating bat species (13 of 15 Oregon species) | Low temperatures and high humidity; bat hibernacula in caves are affected. Potential effects on migratory tree bats are unknown. Primary cause of mortality is skin infection by Pseudogymnoascus destructans, but the process is unknown and exact conditions for infection and mortality are unknown. | Conduct active monitoring of susceptible bats and habitats. An interagency plan and decontamination protocols have been developed. |