Recent coverage of the Zika virus and its health impact on people and fetuses has raised questions among pet owners. The Zika virus was first identified in Africa more than 60 years ago. It is spread to people primarily by mosquito bites, and usually causes no or only mild symptoms in people. However, infection with Zika virus in pregnant women has been linked to microcephaly, a condition in which infants are born with abnormally small heads and incomplete brain development.
Dr. Ashley Mitek at the University of Illinois College of Veterinary Medicine in Urbana has compiled information available to date regarding the possible impact of Zika virus on pets.
Can my pet become sick from the Zika virus?
We have limited scientific information regarding how Zika behaves in animals. Dr. Maureen Long is an associate professor in the Department of Infectious Diseases and Pathology at the University of Florida College of Veterinary Medicine and an expert in Flaviviruses, the genus to which Zika belongs. She notes, “Disease caused by Zika has not been demonstrated in animals, and, in the short term, it is unlikely to become a problem in our animal population in the United States.”
Although there is a report of immune-compromised research mice becoming ill with Zika in one experimental model, Dr. Long notes that this research does not translate to our pet populations because the mouse model was genetically altered to have a weakened immune system.
The Centers for Disease Control and Prevention (CDC) reaffirms Dr. Long’s comments on its website, stating that, “There have not been any reports of pets or other types of animals becoming sick with Zika virus.” However, Dr. Long and the CDC agree that more research is needed before we can be absolutely certain that Zika will not affect animals.
Is it possible for animals to serve as a “reservoir host” for the Zika virus or transmit the virus to people?
A “reservoir host” is a long-term host of a disease, and typically, a reservoir host species does not become clinically ill from the disease – they just carry it in their body. For example, a reservoir host of the Ebola virus is the fruit bat. These bats can carry Ebola in their blood and transmit the virus to primates and humans, but the bats do not become sick from Ebola.
It is unknown whether animals will become reservoir hosts of Zika, but Dr. Long thinks it is unlikely. “To our knowledge, the only species that develop a very high viral load of Zika in their blood are humans and non-human primates.”
Thus, if an animal is bitten by a mosquito carrying Zika, it is unlikely that the animal will provide a hospitable environment in which the virus could thrive. The CDC website agrees, stating that, “At this time, animals do not appear to be involved in the spread of Zika virus.”
Will we start to see microcephaly (a baby born with an abnormally small head) in animals born to a Zika-infected mother?
It is unlikely. To our knowledge, there are no known cases of microcephaly linked to Zika in veterinary medicine. However, further research is needed on this topic. Other viruses of the Flavivirus genus are known to be “vertically transmitted,” meaning they tend to spread easily from mother to fetus.
Are pets being tested for Zika?
No. We are currently unaware of any diagnostic laboratories in the United States testing for Zika in animals.
“In speaking with many other veterinary diagnostic laboratories in the United States, I am unaware of anyone currently testing client animals for Zika,” says Dr. Rick Fredrickson, director of the Veterinary Diagnostic Laboratory at the University of Illinois. Dr. Fredrickson has monitored various viral disease outbreaks over his career as a pathologist, including the recent canine influenza virus outbreak in Bloomington, Ill.
Dr. Fredrickson says that experts will be keeping a close eye on the evolution of the virus, and if necessary, Zika testing may become available for animal patients in the United States. At present, available research does not warrant offering a Zika test for pets because there is no evidence that animals become sick from the virus.
Dr. Long notes that if veterinary diagnostic laboratories choose to start testing for the pathogen, strict biosecurity measures will be required because of Zika’s ability to make humans sick and cause birth defects in pregnant women.
“It’s important to remember that men are as high a risk as women because men have been shown to transmit the virus to their partners,” she says.
Do the tests used in human medicine for Zika work on animals?
Yes, some do. Although experts hypothesize that dogs and cats (and other domesticated mammals) will not become sick if bitten by a Zika-infected mosquito, it is likely that most animals would mount an immune response to the virus. Tests of blood from animals in Africa have demonstrated immune responses to Zika virus, but no clinical illness has been observed in these species.
Dr. Adam Stern, a pathologist at the University of Illinois Veterinary Diagnostic Laboratory, explains that, “Many animals will seroconvert [create antibodies that indicate exposure] when exposed to a virus, but that does not necessarily mean that that animal will become clinically sick. For example, some birds will seroconvert when exposed to the Rabies virus, but they do not become clinically ill from the virus.”
Thus, a dog in an endemic area could hypothetically test positive for antibodies to Zika (indicating exposure), but may test negative for the antigen (the actual virus replicating in the dog’s blood).
Can topical monthly flea and tick medications prevent Zika-infected mosquitoes from biting a dog or cat?
Some treatments will repel mosquitoes, but not all. K9 Advantix II is a topical product that will repel mosquitoes, according to the manufacturer’s label. This product is very toxic to cats.
Can I spray my pet with the same DEET-containing product I use on myself to repel mosquitoes?
No! According to the website of the ASPCA Animal Poison Control Center, “DEET can cause significant clinical signs in companion animals. It is an N,N-dialkyamide insecticide that is found in over 500 products in varying concentrations. The higher the concentration, the more risk to the pet.”
It is important to protect pets from diseases that are transmitted by mosquitoes, and heartworm disease is the most common of these, affecting millions of dogs and cats in the United States.
“Heartworm disease has been diagnosed in all 50 states,” notes Dr. Ryan Fries, a cardiologist at the University of Illinois Veterinary Teaching Hospital. “All dogs and cats should remain on year-round heartworm preventatives, especially those pets residing in Illinois – a hotbed for heartworm disease.”
Pets can also suffer from the pain and itch of mosquito bites the way people do. Dr. Jason Pieper, a veterinary dermatologist at the University of Illinois, says dogs and cats develop a similar red bump that usually goes away within a few days.
“You typically find mosquito bites on the ears and the nose, the less-haired areas of dogs’ and cats’ faces,” says Dr. Pieper. “Cats in particular develop substantial reactions to a mosquito bite on their nose as this is a hypersensitivity reaction.”
Can I travel with my dog to a part of the world that has an active Zika virus problem?
The CDC currently recommends that pregnant women not travel to areas where there is known transmission of Zika. This travel warning also extends to the male partners of pregnant women since Zika can be transmitted in semen. To our knowledge, there have been no travel warnings issued for animals. We recommend you speak with your local veterinarian if you have any specific concerns.
By Ashley Mitek, DVM