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Elevated Strandings of Harbor and Gray Seals in New England August 2018

August 23, 2018

Frequently Asked Questions

Q: What are the symptoms displayed by the seals?

A: In live seals, symptoms include lethargy, sneezing, coughing, discharge from the eyes and nose, seizures, skin abscesses, and poor body condition. In dead seals, necropsy findings have been consistent with pneumonia.

Q: What is the Influenza A virus?

A: There are three types of influenza viruses: A, B and C. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics. Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: hemagglutinin (H) and the neuraminidase (N). There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes. Influenza A viruses can be further broken down into different strains. Subtypes can be species specific, so not all subtypes are found in all species. (For more information, visit the CDC website). Both Influenza A and Influenza B have been documented to cause illness in seals.

Q: What is canine influenza virus (dog flu)?

A: This is a contagious respiratory disease that originated with H3N8 infecting horses and then spread to dogs. It is unknown if seals can get canine influenza.

Q: What is the risk to humans from the influenza virus?

A: Some Influenza viruses can be shared between animals and people. Additionally, influenza viruses are constantly changing and it is possible for a virus to change so that it could infect humans and spread easily between humans. For this reason, the Centers for Disease Control, the National Wildlife Health Center and other organizations monitoring this event and other animal influenza viruses very closely.

Q: Has influenza virus ever been detected in seals in the northeastern US before?

A: Yes, influenza has been detected in seals in New England:

  • 1979-1980 harbor seal mortality event in the NE USA: H7N7
  • 1982-1983 harbor seal mortality event in the NE USA: H4N5
  • 1991- 1992: Influenza A viruses isolated from seals that died of pneumonia in Cape Cod, MA - H4N6 isolated from lung of 2 seals;  H3N3 isolated from lung of three seals. The H3N3 strain identified here was more closely related to one that infects birds than any other species (see Callan et al. 1995).
  • 2006: H3N8 isolated from a by-caught harp seal with no clinical disease
  • 2011: H3N8 isolated from harbor seals during the Unusual Mortality Event in Maine, New Hampshire and Massachusetts

Q: What is phocine distemper virus?

A: Phocine distemper virus is a type of morbillivirus. Morbilliviruses are in the family Paramyxoviridae and specific morbilliviruses cause measles (in people), canine distemper (in dogs, coyotes, wolves, and seals), rinderpest (in cattle), and peste-des-petits-ruminants (goats and sheep). Five types of morbilliviruses have been detected in marine mammals in the United States: canine distemper virus and phocine distemper virus in seals and sea otters, and dolphin morbillivirus, pilot whale morbillivirus, and Longman’s beaked whale morbillivirus.

Q: What is canine distemper virus?

A: Canine distemper virus is a morbillivirus that can cause disease in dogs, coyotes, wolves, and seals. It is a common virus in dogs and most dogs are vaccinated against this virus.

Q: What is the risk to humans from the phocine distemper virus?

A: Phocine distemper virus is not a zoonotic virus and therefore is not considered capable of being transmitted to humans. To date, there has never been a single reported case of human infection with phocine distemper virus. It is unknown if phocine distemper virus to be transmitted to your dog, so it is best to prevent contact between your dog and seals. 

Q: Has phocine distemper virus ever been detected in seals in the northeastern U.S. before?

A: Yes, phocine distemper virus is routinely detected at low levels in seals along the northeastern U.S. coast. However, large mortality events from this virus have only occurred previously in the northeastern U.S. during the 2006 seal Unusual Mortality Event. Other seal die-offs due to phocine distemper virus have occurred globally, especially in the North Sea.

Q: How do the influenza and phocine distemper viruses spread among seals?

A:  Influenza and phocine distemper viruses are usually spread through inhalation of respiratory particles or direct contact between animals, including between mothers and pups. Animals can also be exposed to the virus through other entryways such as the eyes, mouth, stomach, skin wounds, and the urogenital tract.           

Q: How do the influenza and phocine distemper viruses affect seals?

A: The most common organs affected are the lungs and brain. Sick animals may appear thin, have respiratory difficulties due to pneumonia, and/or exhibit abnormal behavior. When exposed to influenza and phocine distemper viruses, some animals mount an antibody response, which usually protects against future infections and clinical disease. Other animals may not acquire this protection and can succumb to the disease or to secondary infections that arise as a result of immunosuppression from the infection.

Q: Is there anything you can do to protect the seals?

A: One of the challenges of wildlife management is managing large, healthy populations, and harbor seals in this region are one such group of wildlife. As is the case in many deer populations, diseases can spread quickly within large, dense populations. Typically, the best course of action is to let nature run its course in wild, free ranging robust animal populations. We will be instituting testing and management within our rehabilitation facilities to reduce the potential spread of the disease in rehabilitation centers and to reduce exposure for employees. The public can also help by keeping themselves and pets far away from seals in the wild.

Q: What should I do to protect myself and my pets against these viruses?

A: You should never approach or allow a pet to approach a live or dead marine mammal. Seals, like other marine mammals (dolphins, whales, and sea lions), are protected under the Marine Mammal Protection Act. It is important that people and their pets maintain a safe distance from these animals so as not to disturb the animal, which may be just resting on the beach. Keeping a safe distance will help avoid injury to people, pets, and seals. While seals look cute, they are wild animals and can transmit disease. Some safe viewing tips:

  • Stay at least 100 yards away from seals or other marine mammals.
  • Keep dogs on a leash and don’t allow them to approach seals. Seals and dogs can easily infect each other with diseases since they are closely related species.
  • Call NOAA Fisheries’ stranding hotline at 1-866-755-NOAA (6622), or a local marine mammal stranding network member or visit our Stranding Network web page for local contact information.

Q: What guidance has been provided to the marine mammal stranding response teams regarding handling seals and potential human health impacts?

A: The Network normally follows safety precautions for handling stranded seals as provided in each organization's safety plans and NOAA Fisheries' "Best Practices for Marine Mammal Stranding Response, Rehabilitation, and Release." In addition, we will be distributing an infectious disease prevention fact sheet to our network responders. We have already provided the Network with the option to be involved in the CDC occupational risk assessment.

Q: Does eating seafood pose a risk?

A: Influenza virus and/or phocine distemper virus do not cause disease in fish so there is no risk of catching this virus by eating fish.

Q: Are there any risks to pets?

A: Pets should also be kept away from marine mammals. Dogs and cats also share infectious diseases with marine mammals and therefore should not be allowed to approach live or dead marine mammals or to consume dead marine mammals or their parts. Additionally, sick seals may be more prone to bite you or your pet if you get too close as they do not feel well. NOAA Fisheries recommends contacting your pet’s veterinarian to discuss the potential risk to pets in your local area. You can also find more info on the CDC website.

Q: Where can I find additional information on harbor seals?

A:  You can visit the national NOAA Fisheries Protected Resources website. You can also learn about seal viewing guidelines.

Q:  What should I do if I see a person or animal harassing a seal?

A:  To report violations or for more information on NOAA’s Office of Law Enforcement call the toll-free number: 1-800-853-1964.