Laurie Anne Walden, DVM
Feline infectious peritonitis (FIP) is a serious disease caused by a coronavirus infection in cats. The disease is usually fatal, although a new antiviral drug under investigation has had promising results in some cats.
Cats very commonly carry a strain of feline coronavirus that lives in cells of the intestines. This virus, feline enteric coronavirus, does not cause disease in most cats. In some cats, though, the virus mutates into a disease-causing strain that invades a type of white blood cell and spreads through the body. This strain is FIP virus (FIPV). The disease it causes, FIP, results from the body’s immune response to the infection.
Feline enteric coronavirus spreads easily among cats housed together, especially in shelters and catteries. This virus is shed in the feces, and cats can be infected if they share litter boxes or have close contact with infected cats. Cats with no symptoms can spread the virus to other cats. Cats are often exposed to feline enteric coronavirus as young kittens.
Why feline enteric coronavirus mutates into FIPV in some cats is not fully known. Virus genetics and individual cat factors (genetics, immune function, and possibly environment) are likely to be involved. Most cats that develop FIP are kittens or young adults. Cats housed in groups, male cats, purebred cats, and cats that have not been spayed or neutered are at higher risk than others for FIP.[1,2]
The mutated virus strain, FIPV, does not appear to spread directly from cat to cat. Feline enteric coronavirus and FIPV are not known to infect humans.
Most cats exposed to feline enteric coronavirus do not become ill. Some cats have an episode of diarrhea or vomiting, which is usually mild.
Because FIPV spreads throughout the body, FIP affects many body systems and can cause a wide range of symptoms. The clinical signs are not specific; they can be caused by diseases other than FIP.
Typical FIP signs are caused by fluid accumulation in the abdomen and chest, by inflammatory changes in various parts of the body (such as kidneys, nervous system, liver, heart, or eyes), or both. The symptoms depend on the body system affected and can change over time in the same cat. These are some of the possible symptoms of FIP:
Diagnosing FIP is not straightforward and can’t currently be done with a simple blood test. Because so many cats have been exposed to feline enteric coronavirus, a positive antibody test (indicating virus exposure) doesn’t mean that a sick cat has FIP. The diagnosis is usually based on a combination of clinical signs, results of baseline blood and urine tests, and analysis of abdominal fluid and samples taken from affected organs.
Until recently, the prognosis for cats with FIP was uniformly bleak. Conventional treatments, including various antiviral medications and drugs to manage the immune response, have had variable success at prolonging cats’ survival times. Cats are usually treated with supportive measures to maximize their comfort for as long as possible.
A new antiviral drug, GS-441524, successfully treated some cats with FIP in a study published in 2019. This drug is closely related to remdesivir, which was originally developed as a treatment for Ebola virus infection and is now being studied as a potential treatment for coronavirus disease 2019. GS-441524 may prove to be effective for some cases of FIP, but it is not currently approved by the US Food and Drug Administration.
Preventing FIP is difficult because feline enteric coronavirus spreads so easily among cats and because the factors that cause it to mutate to FIPV aren’t known. A vaccine for FIP has been marketed, but it is not very effective and is not currently recommended for use in cats. Practicing good husbandry in high-density environments like shelters and keeping individual cats in good health might reduce the risk.
1. Levy JK, Hutsell S. Overview of feline infectious peritonitis. Merck Veterinary Manual. Updated January 2014. Accessed May 6, 2020. https://www.merckvetmanual.com/generalized-conditions/feline-infectious-peritonitis/overview-of-feline-infectious-peritonitis
2. Felten S, Hartmann K. Diagnosis of feline infectious peritonitis: a review of the current literature. Viruses. 2019;11(11):1068. doi:10.3390/v11111068
3. Pedersen NC, Perron M, Bannasch M, et al. Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis. J Feline Med Surg. 2019;21(4):271‐281. doi:10.1177/1098612X19825701
4. Scherk MA, Ford RB, Gaskell RM, et al. 2013 AAFP Feline Vaccination Advisory Panel Report. J Feline Med Surg. 2013;15(9):785‐808. Published corrections appear in J Feline Med Surg. 2013;15(11):NP2 and J Feline Med Surg. 2014;16(1):66. doi:10.1177/1098612X13500429
Photo by Timothy Warrington
Laurie Anne Walden, DVM
New information about coronavirus disease 2019 (COVID-19) continues to emerge as the pandemic progresses. The information in this article is current on the date of posting (April 1, 2020). For the most recent updates, see the resources linked at the end of the article.
Can pets get sick with COVID-19?
This question is still being investigated. A vast number of pets have lived with people with COVID-19 without getting sick, so the risk of human-to-animal transmission is probably extremely low. The Centers for Disease Control and Prevention (CDC) has not had any reports of animals in the United States getting sick with COVID-19.
There have been rare reports of pets in other countries having positive tests for SARS-CoV-2, the virus that causes COVID-19. (A positive test for a virus doesn’t necessarily mean the virus will cause illness in that animal. It also doesn’t show whether the animal can pass the virus to another animal.) These animals each lived with a person with confirmed COVID-19 and were almost certainly exposed by the infected person. Two dogs in Hong Kong had positive tests for SARS-CoV-2 but had no symptoms (they didn’t actually get sick with COVID-19). One cat in Belgium reportedly had a positive test and symptoms, but because of missing or questionable evidence about this cat, the World Organisation for Animal Health has not confirmed this as an infection.
Can pets spread COVID-19 to people?
Multiple infectious disease experts and international health organizations say there is currently no evidence that dogs and cats can spread the COVID-19 virus to people.
There is no need to avoid, neglect, or surrender pets out of fear of COVID-19. (This has reportedly been happening in some places.)
Pets and people live in close contact and can share other diseases, so health organizations recommend washing your hands after handling animals and practicing good hygiene in general.
Can pet hair or accessories (leashes, food bowls, etc) transmit the COVID-19 virus to people?
According to the most recent data and guidance, transmission through pet accessories is theoretically possible but hasn’t been shown to actually happen. SARS-CoV-2 mainly spreads from person to person. Touching an object that has virus particles on it and then touching your face could possibly transmit the virus, but this route is not considered a major source of infection.
If the virus can be transmitted through pet hair or accessories at all, transmission is probably more likely with smooth, solid objects like food bowls than with porous or fibrous objects like hair. Coronaviruses can stay on surfaces for hours or days, according to the World Health Organization. The virus particles might or might not be able to infect a person during that whole time, depending on the environmental conditions.
Although it seems unlikely that the virus would be transmitted by a leash, food bowl, or pet hair, it’s always a good idea to clean pet accessories regularly and wash your hands after handling an animal.
If someone in my household has COVID-19, how should I protect my pets?
The CDC recommends that people who have COVID-19 stay separated from pets. CDC guidance states that people with COVID-19 should “avoid direct contact with pets, including petting, snuggling, being kissed or licked, sleeping in the same location, and sharing food.” This guidance does not apply to service animals, who can stay with their handlers.
If possible, someone who does not have COVID-19 should take over the pet care. People with COVID-19 who have to continue caring for their pets (including service animals) should wash their hands before and after handling their pets. The American Veterinary Medical Association adds that people with COVID-19 should wear a face mask around their animals and shouldn’t share food, dishes, or bedding with them.
No one is recommending that pets wear face masks, in case you were wondering. Face masks could actually harm animals by hindering their breathing.
How should I prepare for pet care in case I get sick with COVID-19?
Plan ahead, just as you prepare for natural disasters like hurricanes. Identify someone who can take care of your pets if you’re unable to. Make sure you have a couple of weeks’ worth of pet food and medications. Check your supply of monthly heartworm and flea preventives and contact your veterinarian if you need a refill. If your pet has medical needs, be ready to provide a list of instructions for another caregiver. Consider preparing a letter for your veterinarian authorizing your backup caregiver to approve treatments.
If my pet needs to see a veterinarian, what should I do?
Contact your veterinarian to find out if your pet should go the clinic. Depending on local guidance, the clinic might be postponing non-urgent procedures to help reduce community spread of COVID-19. Some clinics might be able to treat established patients through telemedicine (virtual visits).
Under North Carolina’s current stay-at-home order, veterinary clinics are considered essential businesses. Your pets can still get the care they need. If your pet needs to be seen at the clinic, you will probably be asked to stay outside the building while your pet is taken inside to help keep you and the clinic staff safe.
If I am (or might be) sick with COVID-19 and my pet needs to see a veterinarian, what should I do?
Call the clinic. Your clinic might not have sufficient personal protective equipment for staff to use when handling animals from a household with COVID-19. Your veterinarian might be able to treat your pet via telemedicine or refer you to a clinic with available protective equipment. If your veterinarian confirms that your pet should come to the clinic, have someone else (ideally not living in your household) transport your pet to the clinic.
For more information and updates:
Image: colorized scanning electron micrograph of cell infected with SARS-CoV. Credit: National Institute of Allergy and Infectious Diseases, NIH; https://www.flickr.com/photos/nihgov/49680300342/.
Laurie Anne Walden, DVM
Coronaviruses cause disease in many animal species. Most coronaviruses affect either the respiratory tract or the digestive system. Some coronaviruses cause no symptoms or only mild illnesses like the common cold. Others cause serious disease.
New information continues to emerge about SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). At this time (early March 2020), there is no evidence that this virus can spread between humans and companion animals like dogs and cats.
For updated information about COVID-19, see these resources:
Coronaviruses got their name from spike proteins that cover the surface of the virus particles and look like a crown (corona in Latin) on electron microscopy images. Coronavirus spike proteins bind to receptors on the host animal’s cells and allow the virus particles to fuse with the cells. Spike proteins and the receptors they target vary according to the type of coronavirus.
Because animal species don’t all have the same molecular receptors and different coronaviruses have different surface proteins, coronaviruses tend to be species specific. A coronavirus that causes disease in cows, for example, doesn’t normally cause disease in cats. This is also why your dogs don’t catch your cold even if you sneeze in their faces.
Some coronaviruses are zoonotic, meaning they can be transmitted between animals and humans. Coronaviruses jump to a new host species through genetic mutation. Mutation changes the virus proteins and creates a genetically different coronavirus that can infect a different host. Jumping to a new species might also be easier if the molecular receptors in the new host species are similar to those of the original host species.
Coronavirus infections in livestock and companion animals can be severe. However, until 2002, coronaviruses usually caused only mild disease in people with fully functioning immune systems. In 2002, an outbreak of severe acute respiratory syndrome (SARS) occurred in China, and in 2012, Middle East respiratory syndrome (MERS) emerged. Both of these outbreaks were caused by coronaviruses thought to have begun as bat viruses. Bats and people don’t have much contact, so the viruses that caused SARS and MERS spread to people through intermediate hosts: civets for SARS and camels for MERS. COVID-19 is the third coronavirus disease to cause serious outcomes in humans.
Animal Diseases Caused by Coronaviruses
Diseases caused by coronaviruses have been identified in many mammal and bird species. Some examples of coronaviruses that cause serious disease in livestock are transmissible gastroenteritis virus and porcine epidemic diarrhea virus in piglets, infectious bronchitis virus in chickens, and bovine coronavirus in cows.
The coronaviruses of most concern in cats and dogs are feline coronavirus, canine coronavirus, and canine respiratory coronavirus. Feline coronavirus usually causes such mild symptoms they aren’t noticed at all. In some cats, though, infection leads to feline infectious peritonitis, a devastating disease that is nearly always fatal. (Feline infectious peritonitis will be covered in more detail in another article.) Canine coronavirus is passed through the feces and causes vomiting and diarrhea, especially in groups of dogs in kennels and animal shelters. Infection usually carries a low risk of death, but a more severe strain of canine coronavirus can be fatal to dogs. Canine respiratory coronavirus is one of the causes of canine infectious respiratory disease (kennel cough).
The emergence of SARS and MERS in humans prompted more research into coronaviruses, so new therapies for coronavirus diseases may be available in the future.
1. Cui J, Li F, Shi ZL. Origin and evolution of pathogenic coronaviruses. Nat Rev Microbiol. 2019;17(3):181-192.
2. Coronaviruses. National Institute of Allergy and Infectious Diseases website. Updated March 2, 2020. Accessed March 5, 2020. https://www.niaid.nih.gov/diseases-conditions/coronaviruses
3. Fehr AR, Perlman S. Coronaviruses: an overview of their replication and pathogenesis. Methods Mol Biol. 2015;1282:1-23.
4. Decaro N, Buonavoglia C. Canine coronavirus: not only an enteric pathogen. Vet Clin North Am Small Anim Pract. 2011;41(6):1121-1132.
Image source: https://phil.cdc.gov/Details.aspx?pid=15523
Laurie Anne Walden, DVM
Kennel cough, the common term for canine infectious respiratory disease (or infectious tracheobronchitis), is a contagious disease that causes a hacking cough. The infection spreads quickly among dogs. Kennel cough is usually a mild illness, but some dogs develop more serious disease.
Many bacteria and viruses cause canine infectious respiratory disease. Most dogs with the disease are infected with more than 1 organism at the same time.[1,2] Some of the organisms involved are the following:
Not all dogs get sick after being exposed to an agent that can cause respiratory disease. Some of these organisms are unlikely to cause illness on their own but can cause symptoms when combined with other organisms. Whether a dog develops respiratory disease is also affected by environmental factors (such as crowding and poor ventilation) and the dog’s immune system.
Kennel cough spreads through respiratory secretions from an infected dog. Dogs with no symptoms at all can spread the infection. Droplets containing bacteria or viruses become airborne after a dog coughs or sneezes and are deposited on surfaces, water bowls, toys, and other objects. The higher the number of dogs housed together, the higher the chance of a dog coming into contact with infected respiratory secretions.
Crowding increases stress, which reduces a dog’s protective immune response against infection. Some infectious agents can hinder the immune response, making infection with additional organisms more likely.
Bordetella bronchiseptica can infect cats and possibly humans. Infection in humans is probably of most concern in people with impaired immune function.
Because of the variety of organisms and differences in individual dogs, symptoms can vary. Typical symptoms of the mild form of disease include the following:
Some dogs, especially young puppies, elderly dogs, and dogs with poor immune function, develop more severe bronchitis and pneumonia. These dogs have more serious symptoms:
For dogs with mild disease, kennel cough is usually presumed from physical examination findings and history of exposure to other dogs. Dogs with a persistent cough or signs of more serious disease need diagnostic testing, which can include chest radiographs, blood tests, and (in some cases) tests to identify the organisms involved.
Treatment decisions are based on the severity of the illness and the dog’s environment. Mild cases of kennel cough often resolve on their own, so dogs with mild disease might need only supportive care (good nutrition, limited activity, and a warm place to rest indoors). Some dogs benefit from treatment with an antibiotic active against Bordetella. Most dogs with kennel cough should not receive cough suppressants. Dogs with more severe disease need more intensive treatment. The treatment for dogs in an environment with a high risk of disease spread (like a shelter) may be different from the treatment chosen for a pet living at home.
Vaccines help control canine infectious respiratory disease. No single vaccine can entirely prevent kennel cough, but vaccinations protect dogs against some of the organisms and reduce the severity and spread of disease.
A combination vaccine including canine distemper virus, canine adenovirus type 2, and sometimes canine parainfluenza virus is recommended for all dogs. Puppies receive this vaccine as part of the puppy vaccine series. Adult dogs should have booster vaccinations (or antibody titer tests).
A vaccine against Bordetella bronchiseptica, sometimes also including canine parainfluenza virus, is recommended for dogs whose lifestyle puts them at risk for infection. The Bordetella vaccine is given in the nose, in the mouth, or by injection, depending on the formulation. Vaccines against canine influenza virus are also available. The decision to give a dog Bordetella and flu vaccines depends on the dog’s lifestyle and possibly on geographic area. Talk to your veterinarian about these vaccines if your dog goes to boarding kennels, doggie daycare, dog parks, dog shows, groomers, shelters, or other areas where dogs gather.
Because infectious respiratory disease is so contagious, dogs with symptoms should be kept away from other dogs as much as possible. Washing hands, bowls, dog toys, and clothing can reduce the risk of spreading the infection to other dogs.
1. Schulz BS, Kurz S, Weber K, Balzer HJ, Hartmann K. Detection of respiratory viruses and Bordetella bronchiseptica in dogs with acute respiratory tract infections. Vet J. 2014;201(3):365-369.
2. Hurley K, Aziz C. Canine infectious respiratory disease complex (CIRDC) - diagnosis and treatment; prevention and management. Pacific Veterinary Conference 2015. Veterinary Information Network website. https://www.vin.com/doc/?id=6789809. Accessed December 6, 2019.
3. Canine infectious respiratory disease complex (CIRDC, a.k.a. “kennel cough”). University of Wisconsin-Madison Shelter Medicine website. https://www.uwsheltermedicine.com/library/resources/canine-infectious-respiratory-disease-complex-a-k-a-kennel-cough. Published July 2015. Accessed December 6, 2019.
4. Kuehn NF. Tracheobronchitis in small animals. Merck Veterinary Manual website. https://www.merckvetmanual.com/respiratory-system/respiratory-diseases-of-small-animals/tracheobronchitis-in-small-animals. Accessed December 6, 2019.
5. 2017 AAHA canine vaccination guidelines. American Animal Hospital Association website. https://www.aaha.org/aaha-guidelines/vaccination-canine-configuration/vaccination-canine/. Published September 7, 2017. Updated February 3, 2018. Accessed December 6, 2019.
Photo by Hannah Lim
Laurie Anne Walden, DVM
Leptospirosis is a disease caused by infection with Leptospira bacteria. The disease is zoonotic, meaning that it can pass from animals to humans. The bacteria are spread through the urine of infected animals and can remain in water or soil for months.
Who’s at Risk
Many different animals can carry Leptospira. Rodents are the most common sources of infection in people. Farm animals, wild animals, and dogs can also be carriers. (Cats are very rarely infected.)
Leptospirosis is a public health hazard for people around the world. People are most often infected through contact with contaminated water, including recreational contact like swimming. Heavy rainfall and flooding increase the risk. Other routes of infection are direct contact with animal urine and contact with contaminated soil or food.[1,2]
Dogs are infected the same way as people: through contact with urine, contaminated soil, or contaminated objects. Dogs can also be infected by eating infected animals. Pregnant dogs can pass the infection to puppies through the placenta.
Dogs are at increased risk for leptospirosis if they have access to any of the following:
Leptospirosis was once considered a disease mostly of working dogs and other outdoor dogs. But small-breed dogs that live in cities and have no access to outdoor water sources are also at risk because rodents carry the disease.
Leptospirosis causes a wide range of problems, including kidney failure, liver failure, lung disease, eye damage, blood clotting disorders, and death. Some dogs infected with Leptospira have mild disease or no symptoms at all. The severity of disease depends on the Leptospira strain and the dog’s immune system, among other factors.
Symptoms of leptospirosis in dogs vary but can include the following:
Leptospira infection can be diagnosed with blood tests. Dogs suspected of having leptospirosis generally also need other tests, such as urinalysis, x-ray examination, and ultrasound.
Dogs with leptospirosis are treated with antibiotics. Most require hospitalization for supportive care and intravenous fluid treatment. The prognosis is good for most dogs that are treated early in the course of disease. Dogs with kidney failure that is not aggressively treated and those with lung complications have a poorer chance of survival.
Dogs with leptospirosis can infect people and other dogs. People handling infected dogs should take precautions like wearing protective clothing and avoiding contact with the urine.
Leptospira vaccines are available for dogs. Talk to your veterinarian about your dog’s risk for leptospirosis. In some geographic areas, veterinarians recommend leptospirosis vaccination for all dogs, including those that live mostly indoors.
Other precautions to reduce the risk of infection are washing hands after handling dogs, wearing gloves when cleaning or collecting dog urine, and using antibacterial solutions to clean surfaces that might be contaminated with urine. The Centers for Disease Control and Prevention recommends avoiding contact with contaminated water (don’t wade barefoot in floodwater!) or wearing protective clothing around potentially contaminated water or soil.
1. Leptospirosis. Centers for Disease Control and Prevention website. https://www.cdc.gov/leptospirosis/index.html. Accessed July 9, 2019.
2. Leptospirosis. World Health Organization website. https://www.who.int/zoonoses/diseases/leptospirosis/en/. Accessed July 9, 2019.
3. Sykes JE, Hartmann K, Lunn KF, Moore GE, Stoddard RA, Goldstein RE. 2010 ACVIM small animal consensus statement on leptospirosis: diagnosis, epidemiology, treatment, and prevention. J Vet Intern Med. 2011;25(1):1-13.
Photo by Matt Jones on Unsplash
Laurie Anne Walden, DVM
Fleas don’t just cause itching. They also carry infectious diseases that can be contagious to people. Controlling fleas on your pets protects your whole family’s health.
Tapeworms are parasites that live in the intestines. They shed small body segments called proglottids that pass out of the host animal’s body in the feces. Tapeworm segments in the stool look like whitish rice grains.
Fleas transmit a type of tapeworm that commonly infects dogs and cats. Dogs and cats become infected by swallowing a flea. Tapeworms rarely cause significant disease in dogs and cats.
The dog and cat tapeworm that is carried by fleas, Dipylidium caninum, can also infect humans (usually children) who swallow a flea.
Bartonellosis (Cat Scratch Disease)
Bartonella species are bacteria that cause a variety of diseases in humans and other animals. Cat scratch disease and endocarditis (heart valve infection) are just 2 of the serious illnesses caused by Bartonella infection.
Fleas are the most common insect vector for Bartonella henselae, the species that causes cat scratch disease. Fleas can also carry other Bartonella species. Infected cats and dogs might or might not have any symptoms of infection.
Bartonellosis is a human health risk. Treating your cat with a cat-safe flea preventive reduces the risk of cat scratch disease for people in contact with your cat.
Rickettsiae are a group of bacteria responsible for diseases such as typhus and Rocky Mountain spotted fever. Rickettsiae are spread by arthropods, including fleas and ticks. The types of fleas that infest dogs and cats transmit Rickettsia typhi (which causes murine typhus) and Rickettsia felis. Both of these bacteria can also cause disease in people.[1,4]
Plague, including bubonic plague and the Black Death, is caused by infection with the bacterium Yersinia pestis. The Oriental rat flea (Xenopsylla cheopis) transmits the bacterium usually to rodents but sometimes to cats, dogs, other animals, and humans. Rat fleas in the western United States and other parts of the world still harbor Yersinia.
Cats infected with certain types of Mycoplasma bacteria develop anemia (low red blood cell count). Fleas are thought to be a source of infection for cats.
Fleas cause skin disease in animals that scratch or chew themselves to relieve the itch. Just a few fleas can set off intense itching in an animal with a flea allergy.
Because fleas feed on blood, animals with lots of fleas can develop anemia from blood loss. This anemia can be life threatening.
1. Fleas. Companion Animal Parasite Council website. https://capcvet.org/guidelines/fleas/. Updated September 19, 2017. Accessed May 7, 2019.
2. Bartonella infection (cat scratch disease, trench fever, and Carrión’s disease). Centers for Disease Control and Prevention website. https://www.cdc.gov/bartonella/index.html. Updated December 14, 2015. Accessed May 7, 2019.
3. Shaw SE. Flea-transmitted infections of cats and dogs. World Small Animal Veterinary Association World Congress Proceedings, 2008. Veterinary Information Network website. https://www.vin.com/doc/?id=3866578. Accessed May 7, 2019.
4. Little SE. Feline fleas and flea-borne disease (proceedings). DVM360 website. http://veterinarycalendar.dvm360.com/feline-fleas-and-flea-borne-disease-proceedings. Published April 1, 2010. Accessed May 7, 2019.
5. Lappin MR. Update on flea and tick associated diseases of cats. Vet Parasitol. 2018;254:26-29.
Photo of Oriental rat flea (Xenopsylla cheopis) by James Gathany, CDC
Laurie Anne Walden, DVM
Adult heartworms grow up to a foot long, block blood flow around the heart, and cause inflammation within blood vessels. The damage continues as long as the heartworms remain in the body.
Heartworm treatment protocols for dogs are designed to remove the worms while reducing the risk of treatment complications. No safe heartworm treatment exists for cats and ferrets. Your veterinarian can recommend appropriate heartworm preventives for your dog, cat, or ferret.
Heartworm infection is diagnosed with a blood test. Your veterinarian might confirm the diagnosis with another test before proceeding with treatment.
Other tests, like x-ray imaging, echocardiography (heart ultrasound), and other blood tests, are used to assess the extent of damage. The results can affect the treatment plan, so your veterinarian might recommend these tests even if your dog isn’t showing any symptoms of infection. Dogs with blood clotting problems or signs of heart disease need a full diagnostic workup before treatment starts.
Any activity that increases the heart rate and blood pressure can worsen the problems caused by heartworms. Dogs with heartworms need to stay as quiet as possible to limit the damage. Once treatment begins, pieces of dead worms can break off and lodge in small blood vessels, potentially causing serious problems and even death. Strict exercise restriction is the best way to reduce the risk.
The American Heartworm Society (AHS) recommends restricting activity from the time heartworms are diagnosed until 6 to 8 weeks after the last dose of heartworm treatment. Dogs should ideally stay indoors in a small area where they can’t run or jump. Some dogs need to be confined to a crate. They should go outdoors on a leash only long enough to pee and poop. Ask your veterinarian about the level of confinement your dog needs.
Before Killing the Heartworms
Before dogs begin receiving adulticide (medication that kills adult heartworms), they may need treatment for heartworm-related problems. They should receive a certain type of heartworm preventive to remove larvae, or immature worms, from the bloodstream. They also benefit from a monthlong course of doxycycline, an antibiotic, to eliminate a bacterium that lives inside heartworm cells. This bacterium is partly responsible for the inflammation that occurs when heartworms die.
The AHS recommends that dogs start adulticide treatment 2 months after receiving a heartworm diagnosis (30 days after the last dose of doxycycline). Dogs should have limited activity during these 2 months.
The only adulticide currently approved for use in the United States is melarsomine. This drug is given by injection in a veterinary hospital. Your dog may need to stay in the hospital for observation after a melarsomine injection.
The number and timing of injections may vary depending on the situation. The current AHS recommendation is to give a series of 3 injections: 1 injection followed by a 30-day wait, then 2 injections given 24 hours apart. Your veterinarian will suggest a protocol that’s appropriate for your own dog.
Complete exercise restriction is crucial during adulticide treatment and for several weeks after the last dose. Your veterinarian may also prescribe medications to reduce adverse effects of treatment.
Your dog can be retested for heartworms several months after the last melarsomine injection. The goal of treatment is to remove all stages of heartworms.
Protocols to manage heartworm infection without using melarsomine are sometimes called “slow-kill” treatments. These protocols consist of giving doxycycline for a month and beginning a specific type of heartworm preventive to remove larvae. Heartworms take from several months to a year or more to die with these protocols.
The disadvantage of slow-kill treatment is that it allows adult heartworms to remain in the body for much longer than with adulticide treatment. The worms continue to damage the heart and blood vessels during this time. For this reason, the AHS does not recommend this method as standard treatment. Dogs receiving slow-kill treatment should also have exercise restriction for as long as adult heartworms remain in the body.
The advantage of slow-kill treatment is that it costs much less than melarsomine. Slow-kill methods have been proposed for dogs that would otherwise go untreated or be euthanized, like those in shelters or in areas where melarsomine is not available. Slow-kill treatment also offers an option for dogs at high risk of complications from adulticide treatment.
For More Information
See these resources from the American Heartworm Society:
Battling Boredom: Tips for Surviving Cage Rest (PDF)
Heartworm Positive Dogs: What Happens if My Dog Tests Positive for Heartworms?
Heartworm Treatment Guidelines for the Pet Owner (PDF)
Photo by Ryan McGuire
Laurie Anne Walden, DVM
Roundworms are some of the most common internal parasites in dogs and cats. They can also infect humans. According to the Centers for Disease Control and Prevention (CDC), 13.9% of people in the United States have antibodies to roundworms, meaning they have been exposed to the parasite at some point in their lives.
How dogs and cats are infected
Almost all puppies are born with roundworms. The type of roundworm that most often infects dogs, Toxocara canis, transfers from a mother dog to unborn pups through the placenta. T canis can also pass to puppies through the mother’s milk. Infected animals excrete roundworm eggs in their stool, so dogs can be infected by eating feces or swallowing roundworm eggs in the environment. Dogs can also become infected by eating a small animal (like a rodent) that is carrying roundworms.
The most common roundworm in cats is Toxocara cati. Cats and kittens are usually infected by swallowing roundworm eggs in the environment or by eating an infected animal. T cati does not pass to unborn kittens through the mother’s placenta.
Ingested T canis and T cati eggs hatch into larvae in the intestines. The larvae migrate through body tissues to the lungs, are coughed up and swallowed, grow into adult worms in the intestines, and begin producing eggs that pass into the environment through the feces.
Roundworm larvae can remain dormant in body tissues of adult animals instead of maturing in the intestines. These arrested-development larvae can’t be detected by fecal tests for worm eggs because they don’t produce eggs. Dormant larvae in a pregnant dog can become active and move through the placenta to the pups. In other words, a female dog with a negative test for roundworms can pass roundworms to her puppies anyway.
Signs of infection
Infected animals often have no symptoms at all. Dogs and cats (especially puppies and kittens) with lots of roundworms may develop a potbelly, vomiting, diarrhea, weight loss, or dull coat. Heavily infected animals sometimes vomit worms, which look a bit like spaghetti noodles, or pass worms in the stool.
Treatment and prevention in pets
Young puppies and kittens should receive multiple doses of deworming medication. The Companion Animal Parasite Council recommends deworming puppies and kittens every 2 weeks starting at age 2 weeks for pups and 3 weeks for kittens, continuing until they are about 2 months old, and then beginning monthly parasite preventives. Many heartworm preventives also prevent roundworm infection.
To reduce the chance your pets will be infected, remove feces from the environment and try to keep them from eating rodents or other wild animals. Have your veterinarian regularly test your pets for parasites, and give them parasite preventives all year round.
Infection in humans
People can be infected by T canis or T cati if they ingest contaminated dirt or feces. Toxocara eggs can survive in the soil for years. Children and people who own dogs or cats have an increased risk of infection, says the CDC.
Many people with Toxocara infection don’t develop serious disease and have no symptoms. But T canis and T cati larvae can migrate through the bodies of humans, as they do in dogs and cats. Larvae that migrate to internal organs (such as the liver) damage these tissues, a disease process called visceral larval migrans or visceral toxocariasis. Symptoms depend on the organs affected. Sometimes larvae migrate to the eye, causing a disease known as ocular larval migrans or ocular toxocariasis. People with this condition may develop retinal inflammation and vision loss.
Prevention in humans
The CDC recommends these steps to prevent toxocariasis:
For more information
Ascarid (Companion Animal Parasite Council)
Cat Owners: Roundworms and Dog Owners: Roundworms (Pets and Parasites)
Toxocariasis FAQs (CDC)
Photo by Berkay Gumustekin
Laurie Anne Walden, DVM
Are you tempted to skip your pets' heartworm and flea medicines during the winter? Dogs and cats actually need parasite prevention all year round. Year-round parasite control for pets helps keep the whole family safe from parasite-transmitted disease.
Warm spells during the winter are common in North Carolina, so we can’t count on cold temperatures to suppress insects that carry disease. Mosquitoes, fleas, and ticks can also live through the winter in areas that are protected from the cold.
Heartworms are transmitted by mosquitoes. Mosquitoes become active when the temperature rises above about 50°F (which happens routinely in North Carolina during the winter). But occasional warm winter days aren’t the only reason pets need year-round heartworm prevention.
Heartworm preventives work by killing tiny heartworm larvae that are already in an animal’s bloodstream. These larvae came from mosquitoes that bit the animal in the past month or more. Skipping a month of heartworm prevention could mean that your dog isn’t protected from heartworm larvae that he was exposed to when it was warmer. The American Heartworm Society recommends giving heartworm preventives all year round.
Intestinal parasites (worms)
Some heartworm preventives also control intestinal parasites like hookworms and roundworms. These parasites can infect humans too. Giving parasite prevention to your pets throughout the year is a sensible safety measure.
Fleas don’t just causing itching. They also transmit diseases like cat scratch disease, tapeworms, and plague.
Fleas lay eggs that drop off the infested animal into the environment. This means that flea eggs are present everywhere the animal has been, including inside a home. After the eggs hatch, the larvae and pupae (intermediate stages) can stay dormant for weeks to months before becoming adult fleas.
Because fleas can go through their life cycle indoors, they don’t need to wait for warm weather to develop into adult fleas. Flea infestations are easier to prevent than to treat, so the best chance of avoiding a flea problem is to give your pets year-round flea prevention.
Ticks carry many diseases that affect both pets and people. Some tick species, including the type that transmits Lyme disease, are active during the winter when the temperature is above freezing.
Ticks tend to live in leaf litter, crevices of buildings, and underbrush. When they’re ready to take a blood meal, they move to grassy areas or shrubbery near paths and latch onto a passing animal or person.
Ticks can be hard to see through fur, so you might not realize that your dog has picked up a tick. Because of the risk of serious disease, the safest approach is to limit tick exposure: control ticks around your home and give your pets tick preventives recommended by your veterinarian.
Photo by Justin Veenema
Laurie Anne Walden, DVM
Both indoor and outdoor cats need vaccines. Vaccination protects cats against infectious diseases that cause serious illness or death. This article describes the vaccines that veterinarians commonly recommend for cats.
One factor that affects vaccination protocols for cats—but not dogs—is the risk of injection-site sarcomas. Some cats develop these malignant tumors at the injection sites of vaccines or other substances. These cancers are uncommon (estimated to occur in 1 to 10 of every 10,000 cats vaccinated) but can be devastating. Although the vast majority of cats do not develop injection-site sarcomas, feline vaccination protocols are designed to balance the tumor risk with the need to keep cats protected from infectious disease. Recommendations include giving cats only the vaccines that are necessary, vaccinating cats no more often than necessary, and using vaccine formulations that are less likely to cause sarcomas.
Rabies vaccination is mandated by law for dogs and cats in the United States. In North Carolina, all cats, dogs, and ferrets aged 16 weeks and older must be vaccinated against rabies. Rabies vaccination laws are one reason this fatal disease is very rare in humans in the United States. Around the world, rabies kills tens of thousands of people every year.
Cats in North Carolina can and do get rabies. In 2017, cats were 1 of the 5 most common species to test positive for rabies in this state (after raccoons, skunks, foxes, and bats). The total number is low, but the risk is real.
Cats that live 100% indoors need rabies vaccines too. Cats sometimes escape outside. And sometimes the unexpected happens, like a bat getting into the house. The presence of a bat indoors is considered a rabies exposure unless the bat is caught and tests negative. A cat that is exposed to rabies but does not have a current rabies vaccination is subject to quarantine for up to 6 months. Also, a cat that bites a person must be quarantined for 10 days; cats without current rabies vaccinations typically spend this quarantine at a facility instead of at home. For more information, see the post about NC rabies laws.
In North Carolina, the first rabies vaccine a cat receives lasts for 1 year, and subsequent vaccines can legally be given every 3 years (as long as the vaccine is labeled for 3-year use). If your veterinarian recommends giving your cat a rabies vaccine every year instead of every 3 years, it’s probably because the clinic uses a feline rabies vaccine that is designed to reduce the sarcoma risk and is labeled for 1-year use. Most 3-year rabies vaccines on the market are killed-virus vaccines that contain adjuvants, substances that enhance the immune response. Killed, adjuvanted rabies vaccines have been associated with injection-site sarcomas in cats. A different type of rabies vaccine, a recombinant vaccine, does not contain adjuvants. The most common version of the recombinant rabies vaccine is a 1-year vaccine. Ask your veterinarian which type of rabies vaccine the clinic uses for cats.
Feline herpesvirus 1 (rhinotracheitis), calicivirus, and panleukopenia virus
Vaccines for feline herpesvirus 1, calicivirus, and panleukopenia virus are often included in a single combination vaccine. The American Association of Feline Practitioners (AAFP) recommends that all cats be vaccinated against these viruses as kittens (in a series of boosters), again 1 year later, and then every 3 years. In past decades, cats received these vaccines every year, but annual vaccination is no longer considered necessary.
Feline herpesvirus 1 and calicivirus are 2 of the main causes of feline respiratory disease complex. This illness spreads easily from cat to cat. People can also carry the infectious agents on their clothing, which is how indoor cats can be infected. Infection causes sneezing, discharge from the nose and eyes, conjunctivitis (pinkeye), fever, mouth ulcers, and eye ulcers. Some combination vaccines also cover Chlamydophila (Chlamydia) bacteria, which cause conjunctivitis in cats.
Feline panleukopenia virus is very contagious among cats, and infection can be fatal. The virus is similar to canine parvovirus. Like parvovirus, it destroys cells lining the intestine and impairs immune function. In kittens, it can also damage the part of the brain that regulates coordination and balance.
Feline leukemia virus
Feline leukemia virus is a retrovirus that suppresses immune function and causes cancer. Because the virus impairs immunity, infected cats develop a wide variety of medical problems. Most infected cats die within 3 years of diagnosis. There is currently no cure.
Vaccines against feline leukemia virus have been associated with injection-site sarcomas. For this reason, the decision to vaccinate an adult cat usually depends on the cat’s lifestyle and risk factors. However, the AAFP recommends vaccinating all kittens against feline leukemia virus. A nonadjuvanted recombinant vaccine is available.
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Laurie Anne Walden, DVM
The contents of this blog are for information only and should not substitute for advice from a veterinarian who has examined the animal. All blog content is copyrighted by Mallard Creek Animal Hospital and may not be copied, reproduced, transmitted, or distributed without permission.