Dog-Mediated Rabies Virus Variant (DMRVV) in the United States: New Rules from the CDC for Importing Dogs

Written by Dr. Zachary Glantz

Recently, the Centers for Disease Control (CDC) imposed strict rules for dog import. Many dog owners who travel outside of the United States may be confused about why this is happening.

Below is a rough outline of what has happened to help understand why the CDC rules have been changed.

Why Does the CDC Care About Rabies?

Rabies is a serious disease, with a 100% fatality rate if symptoms develop. All mammals, including humans, can contract rabies.

Rabies is endemic in the United States, meaning it's spread through many populations of wildlife with no clear path to eradication. Currently in the US, around 4,000 animal rabies cases are reported each year, with more than 90% occurring in wildlife like bats, raccoons, skunks, and foxes. This is a big change from the 1960s, when domestic animals, mainly dogs, represented most of the rabies cases.

Even though rabies is well-controlled in the US, over 4 million people are bitten by animals a year, with 800,000 seeking medical attention.

Why are the New Rules for Importing Dogs so Strict?

There are multiple virus variants of rabies, and the most contagious and dangerous are the Dog-Maintained Rabies Virus Variants (DMRVV). 99% of the estimated 60,000 human rabies deaths a year that occur worldwide are attributed to DMRVV. 

With tremendous public health measures, the United States eliminated DMRVV in 2007, so importation of an infected dog presents a risk for reintroduction to the United States. 

When a dog with DMRVV is discovered, state and federal public health responses are enacted to prevent the spread of DMRVV, costing between $400,000 to $800,000 per dog.

Those costs do not account for the worst-case scenarios, such as transmission of rabies to a person who dies from the disease, or ongoing transmission to other domestic animals or wildlife.

A previous campaign to eliminate domestic dog-coyote rabies in Texas from 1995 to 2003 cost $34 million dollars ($48 million in 2020 US dollars).

Re-establishment of DMRVV into the United States could result in costly efforts over several years to eliminate the virus again.

DMRVV control in the United States after 2007: What measures were in place for importing dogs?

The World Organization for Animal Health recommends that all countries verify adequate vaccination in dogs from countries with endemic rabies by requiring testing of antibody levels before entry. Most developed countries have that requirement. For example, rabies is endemic to the United States, and many countries (China, Japan, Australia, Korea, etc) require dogs arriving from the United States have blood titers to enter.

Until July 14th, 2021, all dogs admitted to the US were required to have a valid rabies vaccination certificate unless the dogs' owners or importers had evidence that either:

• The dog was under 6 months of age and had not been to a country high-risk for DMRVV, or

• The dog was older than 6 months and had not been in a country high-risk for DMRVV in the 6 months prior to arrival.

The US government estimates that approximately 1 million dogs per year are imported into the United States, and roughly 100,000 dogs are from countries high-risk for DMRVV.

Since DMRVV was eliminated from the United States, from 2007 to 2020, there were 3 instances of rabid dogs imported into the United States:

2015 - A rabid dog was part of a group of 8 dogs and 27 cats imported from Egypt by a rescue group. The dog had an unhealed leg fracture and developed signs of rabies 4 days after arrival. The rescue workers in Egypt admitted the dog's rabies vaccination certificate had been intentionally falsified to evade CDC requirements. Eighteen people received post-exposure prophylaxis, and 7 dogs underwent a 6-month quarantine.

2017 - Four dogs were imported from Egypt by a "flight parent" (person solicited through social media by a rescue organization to travel with an animal) on behalf of a rescue organization. One of the dogs appeared agitated at the airport and bit the flight parent prior to the flight. One day after arrival to the US, a veterinarian euthanized the dog due to neurologic symptoms and it tested positive for rabies. Four people received post-exposure prophylaxis and 3 dogs were quarantined. An investigation found the rabies vaccination certificate for all four dogs were falsified.

2019 - A rescue group imported 26 dogs from Egypt, all of which had rabies vaccination certificates and rabies titer documentation indicating appropriate response to vaccination. One dog developed signs of rabies three weeks after arrival to the United States and was euthanized, testing positive for rabies. Forty-four people received post-exposure prophylaxis, and 36 dogs were quarantined.

Why Did the CDC Import Rules Change?

Historically, about 60-70% of the CDC's dog entry denials (about 200 cases annually) are based on fraudulent, incomplete, or inaccurate paperwork. This is less than 1% of dog importations.

However, between January and December 2020, the CDC documented more than 450 instances of incomplete, inadequate, or fraudulent rabies vaccination certificates for dogs arriving from high-risk countries, two of which were reported by Dr. Glantz.

This number increased in the first 6 months of 2021, with 560 instances identified. 

During the COVID-19 pandemic, canine rabies vaccination campaigns were suspended in many high-risk countries, resulting in an increase in canine and human rabies cases. This pause, along with the delay in re-establishing pre-COVID rabies vaccination rates, combined with insufficient veterinary controls in place to prevent export of inadequately vaccinated dogs, resulted in a significant public health risk.

Prior to the CDC suspension of dog imports in 2021, dogs arriving from high-risk countries without appropriate paperwork were denied entry and returned to the country of origin on the next available flight. While the costs associated with housing, care for, and return of the dogs are the responsibility of the importer, in most cases, the importer abandons the dog, leaving the airline responsible. Many airlines and importers were reluctant to pay these costs, requiring the US government to pay approximately $1000 to $4000 per dog. From May through December 2020, the CDC spent an estimated $270,000.

There was also an animal welfare concern. Due to the increased number of dogs and reduced frequency of flights, some airlines housed dogs in cargo warehouses that created an unsafe environment, with inadequate cooling and heating, poor cleaning and sanitization, and inability to physically separate the animals from areas of the warehouses where other equipment, machinery, and goods were used and stored. Cargo warehouse staff who were not trained to house, clean, and care for live animals with appropriate personal protective equipment were at risk of bites, scratches, and exposures to potentially infectious bodily fluids.

In August 2020, a dog denied entry based on falsified paperwork died while in the custody of an airline at O'Hare International Airport. Despite the CDC's request to find appropriate housing at a local kennel or veterinary clinic, the airline left the dog, along with 17 others, in a cargo warehouse without food and water for more than 48 hours.

All of this prompted the CDC to evaluate and improve the dog import requirements.

Why Did the CDC Import Ban Go into Effect so Suddenly?

Just before the CDC planned to announce new restrictions on dog entry, on June 10th, 2021, a shipment of 33 dogs and one cat arrived at O'Hare International Airport from Azerbaijan, a country known to be high risk for DMRVV. All 34 animals were imported by a rescue for adoption, and had valid rabies vaccination certificates and appeared healthy on visual inspection by the CDC quarantine station staff. Entry requirements at the time were minimal, and were met, so the animals were allowed entry and were transferred to caretakers, then relocated by ground transportation to California, Florida, Illinois, Michigan, New Jersey, New York, Ohio, Pennsylvania, and Washington.

Three days later, one of the dogs (a 5 month-old puppy), was hospitalized at a veterinary clinic in Pennsylvania due to diarrhea and neurologic issues starting the previous day, including biting invisible objects (fly-biting behavior), hypersalivation, and agitation. While hospitalized, the dog developed seizures and then cardiac arrest. The dog was stabilized with CPR and resuscitated and intubated, but was later euthanized. Due to the neurologic signs, the dog was submitted for rabies testing.

On June 16th, the Pennsylvania Department of Health Bureau of Laboratories confirmed rabies virus infection, and on June 18th the CDC Rabies Laboratory confirmed it was DMRVV. Complete rabies virus nucleoprotein and glycoprotein sequences matched 99.5% with a reference rabies virus isolate collected from a dog in Azerbaijan in 2002, confirming the infection did not originate in the United States.

The CDC immediately led a multi-state investigation to implement prevention and control measures and worked with the Chicago Department of Health and the Pennsylvania Department of Agriculture. From June 10th to 13th, the dog had been in the adopted family's home, two pet stores, and the veterinary clinic. Thirty-seven people were identified as potentially exposed, resulting in 15 people receiving 18 rabies postexposure prophylaxis.

Blood samples from the dog were tested for rabies antibodies, and the results were 0.3 IU/mL, which is below the cut-off value of 0.5 IU/mL established by the World Organization for Animal Health for adequate response to rabies vaccination.

All of the other 33 animals in the shipment were considered exposed, and their vaccination status was considered unreliable. They all had blood drawn and rabies vaccination administered, then blood drawn again 5-7 days later. Antibody titers were measured, and 14 of the 33 animals had values below 0.5 IU/mL, indicating inadequate titers at the time of importation. Eight had titer levels of 0 IU/mL and were likely unvaccinated. All of the animals were quarantined and thankfully none developed rabies symptoms, and they were all released from quarantine on December 29th, 2021.

The eight unvaccinated dogs had all been housed at the same rescue location in Azerbaijan and were all reported to have been vaccinated at the same veterinary clinic. The CDC investigation revealed that a new employee at the veterinary clinic had been responsible for administering the vaccinations, and an internal review of their workstation revealed numerous rabies vaccination vials with higher than expected residual volume, with the single-dose vials containing approximately 25-33% of the original volume. The failure of vaccine response was likely due to the staff member only administering 66-75% of the vaccine volume, resulting in a high vaccine failure rate.

This led to the CDC's emergency ban on importation of all dogs from countries high-risk for dog rabies on July 10th, 2021, which has been modified and developed into the finalized rules in effect August 1st, 2025.

For more information on the current dog entry rules for the United States, please review our blog post on the topic here.