Ebola Virus Outbreaks and Veterinary Considerations

ebola virus

What is Ebola virus disease?

Ebola virus disease (EVD) is also known as Ebola haemorrhagic fever. EVD is a severe contagious disease affecting humans, non-human primates and some domestic species (e.g. pigs). It can be transmitted to humans through direct contact with blood, tissues, body fluids and secretions from an infected animal or human, and from the handling of wild animals hunted for food. The causative agent is classified in the genus Ebolavirus of the Filoviridae family. As members of the order Mononegavirales, filoviruses are filamentous enveloped viruses containing a non-segmented, negative-strand genomic RNA of approximately 19 kilobases.

The five known species in the genus Ebolavirus (EBOV) are: Zaire ebolavirus (ZEBOV); Sudan ebolavirus (SEBOV); Bundibugyo ebolavirus (BEBOV); Reston ebolavirus (REBOV) and Taï Forest ebolavirus (TEBOV). Their genomes can differ by 30-40%.

Base on available evidence, it is presumed that REBOV has a low pathogenicity or is non-pathogenic in humans whilst the ZEBOV and SEBOV strains are known for their virulence and high case fatality rate (53-90%) in humans. More information can be found in the OIE fact sheet.

What animals have been shown to shed Ebola virus?

Field studies and epidemiological surveys in Africa have demonstrated widespread antibody prevalence to Ebolaviruses in fruit bats suggesting that fruit bats may be natural hosts for EBOV. When bats and other vertebrate species were experimentally inoculated, only bats became infected and shed virus in feces without showing any clinical signs. Monkeys are not considered as natural hosts because of their high sensitivity to the virus and their high mortality rate when infected. Only mammals (for example, humans, bats, monkeys, and apes) have shown the ability to become infected with and spread Ebola virus.

The role of pigs in EVD epidemiology is unclear. Pigs infected with ZEBOV showed mild clinical signs, and were able to transmit the virus to non-human primates (Weingartl et al 2012). There is no evidence that domestic animals play an active epidemiological role in the transmission of the disease to humans, although field studies are non-existent. The related Marburg virus has been isolated from fruit bats (Roussettus aegyptiacus) in Uganda.

Can pets become infected with Ebola virus?

A study in 2005 identified an increasing seropositivity to ZEBOV in dogs sampled in regions of Africa that were proximate or distant from known ZEBOV outbreaks – the closer the dog was to the outbreak region, the more likely it was to have antibodies directed against ZEBOV. However, the authors failed to detect either RNA (by RT-PCR) or viral antigen (by viral isolation, although viral isolation failed in the positive control samples as well). The authors concluded that ZEBOV could induce an immune response in dogs, but could not determine if dogs could shed the virus.

Guinea pigs, goats, and horses remain subclinical or develop mild clinical signs after experimental infection, but Ebola virus infection has never been observed in these species in the wild.

Can pets transmit Ebola virus to people or other animals?

There is no evidence that domestic species, including dogs, can or ever have, transmitted Ebola virus to humans or other animals. Some investigators have questioned the role of dogs in transmission where no obvious source was identified in an outbreak; however, these outbreaks occur in regions where exposure documentation is limited, incomplete or inaccurate. Therefore, such hypotheses are speculative at best. On the other hand, rigorous investigation of potential canine infections in field situations is virtually non-existent.

Can dogs be subclinical carriers for Ebola virus?

There is no evidence currently that dogs can carry and shed Ebola virus. No virus has ever been isolated from a dog.

How long can a dog be infected with Ebola virus?

Since there is no evidence that dogs can become infected with Ebola virus, there is no way to estimate a duration of infectivity (which would involve viral replication and shedding).

Is a dog seropositive for anti-Ebola antibodies infected and can then transmit the virus?

No. Seroconversion only requires that antigen be presented by antigen-presenting cells to lymphocytes. Infection requires invasion of host cells, replication, and shedding.

Is Ebola transmitted via aerosol?

There is no evidence that Ebola virus is transmitted by aerosol, water or food. In two separate experimental studies—one with monkeys and the other pigs and monkeys—the authors suggest an airborne possibility of transmission. However, this route of transmission was not confirmed and other means of transmission were not ruled out. (Jaax et al, 1995, Weingartl et al 2012).

What should be done with a pet in the home of an Ebola patient?

CDC recommends that public health officials, in collaboration with a veterinarian, evaluate the pet’s risk of exposure to the virus (close contact or exposure to blood or body fluids of an Ebola patient). Based on this evaluation as well as the specific situation, local and state human and animal health officials will determine how the pet should be handled. Currently, a dog exposed to an infected health worker in Texas, is being quarantined at a decommissioned military base. A veterinarian who is caring for the animal of an Ebola patient or the animal of someone who has been in contact with an Ebola patient should contact their state health department for guidance.

What is the evidence about fomite (including fur) transmission and survival times of the virus?

While there is no evidence that the virus can be transmitted on the fur or saliva of dogs, there is some evidence that fomite-associated transmission might occur (Jaax N et al, 1995). Therefore, the CDC advises that the most prudent course of action is to keep pets away from people who have been exposed to, or are infected with, Ebola virus.

Can Ebola virus survive in the environment?

Ebola viruses are encapsulated viruses and therefore sensitive to dessication, detergents and disinfectants. They do not survive for long in the environment (hours, rather than days or weeks), and can be inactivated with exposure to many disinfectants. According to the Centers for Disease Control and Prevention (CDC): “The role of the environment in transmission has not been established. Limited laboratory studies under favorable conditions indicate that Ebolavirus can remain viable on solid surfaces, with concentrations falling slowly over several days. In the only study to assess contamination of the patient care environment during an outbreak, virus was not detected in any of 33 samples collected from sites that were not visibly bloody…There is no epidemiologic evidence of Ebolavirus transmission via either the environment or fomites that could become contaminated during patient care (e.g., bed rails, door knobs, laundry). However, given the apparent low infectious dose, potential of high virus titers in the blood of ill patients, and disease severity, higher levels of precaution are warranted to reduce the potential risk posed by contaminated surfaces in the patient care environment.”

What additional resources are there about Ebola virus exposure for pets?


Journal Articles

  1. Allela L, Bourry O, Pouillot R, Delicat A, Yaba P, Kumulungui B, Rouquet P, Gonzalez J-P, Leroy EM. Ebola virus antibody prevalence in dogs and human risk. Emerg. Infect. Dis. 2005;11(3):385-390.

  2. Jaax N, Jahrling P, Geisbert T, Geisbert J, Steele K, McKee K, et al. Transmission of Ebola virus (Zaire strain) to uninfected control monkeys in a biocontainment laboratory. Lancet. 1995;346:1669–71.
  3. Weingartl HM, Embury-Hyatt C, Nfon C, Leung A, Smith G, & Kobinger G. Transmission of Ebola virus from pigs to non-human primates. Scientific Reports Nov. 15, 2012.

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