A Tale of Two Viruses
Do dogs spread COVID-19 to people?
As the year 2020 draws to a close, let’s review what we know about the risk of dogs spreading the SARS-CoV-2 virus that causes COVID-19 in people. According to the Center for Disease Control (CDC), the exact source of the current outbreak of coronavirus disease 2019 (COVID-19) is unknown, but it is believed that it originally came from an animal, most likely a bat. At this time, there is no evidence that animals play a significant role in spreading the SARS-CoV-2 virus to people.
Coronaviruses are a large family of viruses. Some coronaviruses cause cold-like illnesses in people, while others cause illness in certain types of animals, including cattle, camels and bats. Canine and feline coronaviruses only infect animals and do not infect humans.
It is possible for a coronavirus to infect animals, spread to humans, and then spread between humans – but it is an extremely rare occurrence. This is what happened with SARS-CoV-2, which is thought to have originated in bats. The first reported infections were linked to a live-animal market, but the virus is now spreading from person to person.
SARS-CoV-2 spreads through respiratory droplets from coughing, sneezing and talking. In the early stages of the pandemic, there was concern that animals, especially pet dogs and cats that were in close contact with people infected with the virus, could be “fomites,” transmitting the virus to people on their fur. At the present time, studies are being conducted, and based on current information the risk of pet animals spreading COVID-19 to people is considered to be low.
A very small number of pet dogs and cats worldwide have been reported to be infected with the SARS-CoV-2 virus. Most of these pets became sick after being in close contact with people with COVID-19. Data from studies suggests that dogs can get infected but do not seem to spread the virus to other dogs as easily as cats and ferrets can spread the virus to animals of the same species.
We do not yet know all of the animals that can become infected. Several lions, tigers and pumas in captivity have tested positive for SARS-CoV-2 after showing signs of respiratory illness. It is suspected that these large cats became sick after being exposed to zoo employees with COVID-19.
The virus has been reported in mink on farms in the Netherlands, Denmark, Spain, Italy, Sweden, Greece and the United States. The signs of infection in farmed mink have been respiratory disease and death. There have been reports of thousands of mink euthanized after testing positive. It is likely that infected farm workers were the initial source of the mink infections.
The CDC, USDA, state public health and animal health officials, and academic partners are following the cases of SARS-CoV-2 in pets, including dogs, cats and other small mammals, that had contact with a person with COVID-19. These animals are being tested for SARS-CoV-2 infection and also tested to see whether the pet develops antibodies to this virus. This work will help us better understand how common SARS-CoV-2 infection is in pets as well as the possible role of pets in the spread of the virus. Based on the limited information available to date, the risk of animals spreading COVID-19 to people is low.
Is there a new treatment for canine parvovirus?
Yes, there is a newly tested monoclonal antibody that shows great promise for the prevention and treatment of the devastating canine parvovirus (CPV). CPV is a highly contagious virus that can affect all dogs, but unvaccinated dogs and puppies younger than four months old are at the highest risk. There are estimates of more than 250,000 reported cases of canine parvovirus in the United States annually. This number may actually be higher, as many cases may go undiagnosed. Some hospitals have seen a 70 percent increase in cases of CPV throughout the COVID-19 pandemic.
The virus attacks the dog’s gastrointestinal tract, causing severe, often bloody diarrhea. Dogs are unable to eat or drink and may die as a result of starvation and dehydration.
CPV is spread by dog-to-dog contact and exposure to contaminated feces, environments, food and water bowls, and people who handle infected dogs. The virus is resistant to heat, cold, humidity and drying, and can survive in the environment for long periods of time. CPV is easily transmitted from place to place on the fur and feet of dogs or by contaminated cages. People can spread the virus on their shoes and clothing.
Until now, no specific drug has been available that will kill the virus in infected dogs. Treatment has been directed at supporting the body systems until the dog’s immune system can fight off the viral infection. This consists primarily of intensive-care efforts to address dehydration by replacing fluid, electrolyte and protein losses, controlling vomiting and diarrhea, and preventing secondary infections.
Treatment for CPV can be very expensive, and the dog may die despite aggressive treatment. It is the most significant and contagious viral cause of intestinal disease in dogs, especially puppies. The mortality (death) rate can be as high as 91 percent. Even with proper vaccination, a small percentage of dogs do not develop protective immunity and remain susceptible to infection.
One way the body’s immune system attacks foreign substances like viruses is by producing large numbers of antibodies. An antibody is a protein that sticks to a specific protein called an antigen. Antibodies circulate throughout the body until they find and attach to the antigen. Once attached, they force other parts of the immune system to destroy the cells containing the antigen.
Researchers can design antibodies that specifically target a certain antigen, including types of viruses. They can then make many copies of the antibody in the lab. These are known as monoclonal antibodies.
Kindred Biosciences has developed a monoclonal antibody that binds to portions of CPV and prevents it from entering cells. A study they conducted demonstrated 100 percent effectiveness in the prevention of canine parvovirus. None of the dogs treated with the antibody developed the disease, while all the placebo-control dogs developed parvovirus infection as defined in the study protocol.
The antibody is currently being developed for two uses in dogs: preventive therapy to guard against clinical signs of CPV infection and treatment of cases of diagnosed CPV infection. The study is expected to be completed by the end of 2020, and the product available by early 2021.
Vaccination and good hygiene are critical components of canine parvovirus prevention. Bitches should be up to date on their parvo vaccinations before being bred, so they can transfer immunity to their puppies before they are born. In order to develop adequate protection, puppies should receive a dose of canine parvovirus vaccine between 14 and 16 weeks of age, regardless of how many doses they received earlier.
Adult dogs should be kept up to date on their CPV vaccinations as well. There are blood titers available that measure the dog’s level of antibodies against CPV, but the antibody level may not directly translate to protection if the dog is exposed to the virus. Talk to your veterinarian about a recommended prevention program for your dog.