Current Vet

In this episode of Current Vet, Dr. Lottie talks about canine infectious hepatitis, why its presentation can be so confusing, what the approach to treatment is and how we can prevent it

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Timeline:
00:00 Intro
02:23 Case
04:00 Aetiology & Pathogenesis
07:48 Clinical Signs
09:42 Diagnosis
13:35 Treatment
15:22 Prevention
16:40 Key Points
18:04 Outro

References

Current Vet is an educational podcast intended for veterinary students, veterinary professionals, and individuals with an interest in veterinary medicine.

All content provided in this podcast and its associated materials is for educational and informational purposes only. It is not intended as, and must not be considered a substitute for, professional veterinary advice, diagnosis, or treatment.

Any clinical cases discussed in this podcast are fictional, and are designed to reflect typical or likely clinical scenarios for educational purposes. They do not represent specific real-life cases, clients, or animals.

While every effort is made to ensure accuracy and alignment with current evidence at the time of publication, veterinary medicine is a rapidly evolving field, and recommendations may change over time.

Creators and Guests

Host
Dr. Lottie Wilkinson
Creator and host of the Current Vet podcast

What is Current Vet?

The podcast that makes veterinary medicine simple.

In each episode, Dr. Lottie breaks down clinical conditions, cases, and concepts across species, focusing on pathophysiology, decision-making, diagnostics, and what actually matters in practice. It’s the kind of context that makes your knowledge finally click.

Every month, we’ll also have honest conversations with guests about the incredible variety of veterinary medicine, what you can do with a vet degree and how to think bigger about your career.

Whether you’re cramming for exams or looking for a soundtrack for your dog walk, Current Vet will make veterinary medicine simple

Intro

Hello, hello, and welcome back to Current Vet. This is the podcast that makes veterinary medicine simple. I'm your host, Dr. Lottie, And this month, we are going to be focusing on our canine topics. Kinda similar to how we did the cat focus month back in March.

And to kick this month off, we are talking about canine infectious hepatitis, that is CAV-1. This was an episode that was requested by a listener, so thank you so, so much to her for requesting this topic, and also next week's topic on canine distemper as well.

If anyone else has any topics that they do wanna hear, obviously please let us know,

And we're very happy to cover them on the podcast. Before we get into this week's episode, I do actually wanna talk about something that is really exciting. Um, we have a new launch coming at the end of this summer. We'll be releasing more information on this soon, but we've been working on this project for the last almost two years now. And the whole reason behind it is I felt like I was missing so many aspects of learning and so many aspects of support while I was go- through vet school. So I've tried to create exactly what I felt was missing whilst I was in vet school.

So it's something that I've created for vets, more specifically students and new grads, with the sole focus of making vet med simpler. It's gonna be a full 360 approach to vet med. It's not just about the theory. It's not just about clinical cases. We're gonna have a couple of non-clinical aspects. We're gonna focus on different methods of learning, audio learning like with this podcast, active recall, theoretical learning, all those different avenues.

So keep your eyes peeled on our social media for further updates. And if you're interested, there is a waitlist you can join to find out further information. I will link it in the show notes. But otherwise, just get excited, I'm really excited to share it with you. So yeah, keep tuning in, and hopefully we'll have more information on this really, really soon

Okay, let's jump into our case.

Case

You're on consults, and a client rushes in with Rex, who is a seven-month-old entire male Labrador who is acutely unwell. The owner says that he was completely fine yesterday, but this morning he has become lethargic. He didn't eat his breakfast, and then he started vomiting.

Over the last few hours, he's worsened really quickly and now seems weak and doesn't want to move at all. On exam, Rex is depressed, pyrexic, so he's got a temperature of forty point two centigrade or a hundred and four point four Fahrenheit. He is tachycardic, has pale mucus membranes, and slightly prolonged capillary refill time.

As you're examining him, you notice mild petechiae on the gums, and he seems painful when you palpate the cranial abdomen. So in a bit of a nutshell, we have a young, unvaccinated dog who is acutely deteriorating. There are some GI signs, some vomiting, fever, abdominal pain, and now we have evidence of some bleeding.

So our differentials are going to include parvovirus. Of course, we always have to consider that with a young, unvaccinated dog, especially with GI signs. Leptospirosis, possible toxin exposure. We could have sepsis, and of course, we are going to consider infectious canine hepatitis.

So with these differentials, we want to make sure that he's going straight into an isolation kennel, and then let's talk about what is actually going on.

Aetiology & Pathogenesis

So Canine Adenovirus type one is the cause of canine infectious hepatitis, and it's a DNA virus with a tropism for endothelial cells and hepatocytes.

Dogs are infected via the oro-nasal route from contaminated urine or feces, saliva, and the virus typically replicates in tonsils and local lymph nodes. It then can spread via the bloodstream, and once the virus is present in the blood, this is known as a viremia, and that literally means virus in the blood.

So vire being the virus and emia referring to the blood.

So CAV-one infects vascular endothelial cells which line blood vessels. So this is gonna cause endothelial damage, increased vascular permeability, and vascular inflammation known as vasculitis And this results in edema as fluid leaks out of the blood through that leaky membrane into surrounding tissues.

We can also get hemorrhage, and that is why we're seeing those petechiae, and we may see ecchymosis as well.

As we said before, the virus also targets hepatocytes. So this is gonna cause hepatocellular damage, necrosis, inflammation, and the result is going to be decreased hepatic function. So if we think about the roles that the liver plays in the body, we're going to get decreased production of clotting factors, decreased production of proteins, possibly hypoglycemia, as the liver is involved in glucose metabolism ,
and we're gonna have impaired detoxification of the blood. So with that endothelial injury and the reduced clotting factor production because of liver damage, this is the perfect way to develop a coagulopathy and bleeding conditions. And in severe cases, you can also progress to disseminated intravascular coagulation,
there is a slightly odd feature that we can see with canine infectious hepatitis, known as blue eye. So around seven to ten days post-infection, some dogs can develop corneal edema, which is the cause of the, quote-unquote, blue eye. It is not caused by direct damage from the virus. It's due to immune complexes depositing into the cornea, which then causes uveitis, edema, and that weird blue color in the eye.
Immune complex deposition can also affect the kidneys, causing renal tubular damage and inflammation, so that's gonna be glomerular nephritis. And then the virus can actually persist in the kidneys for months afterwards and be shed in urine, so spreading that infection to other animals and contaminating the environment. I do quickly want to highlight a bit of a comparison between canine adenovirus 1 and canine adenovirus 2.

So CAV.1 and CAV.2 are very closely related, but CAV.2 causes laryngotracheitis and is part of the kennel cough complex. So it targets respiratory epithelium and causes mild upper respiratory disease. This is not the same as CAV.1, which is gonna be the cause of canine infectious hepatitis.

However, because they are so similar and so genetically related, the CAV.2 vaccines, so those kennel cough vaccines, actually also protect against CAV.1.

Clinical Signs

Okay, so let's come on to what clinical signs you might see in infected dogs. So if we have paracute or acute cases, we might see things like sudden lethargy, pyrexia, vomiting, diarrhea, abdominal pain, and that is gonna be from a tender liver area, and then petechiae, ecchymosis, and other evidence of bleeding tendencies.

So any evidence of spontaneous hemorrhage, and poor clotting capability. As things progress, the dog can develop hypovolemia, so we're gonna see, prolonged capillary refill time, possibly cold extremities. A couple of other signs we might see are lymphadenopathy, so that's gonna be inflammation and enlargement of the lymph nodes.

We might feel on abdominal palpation some hepatomegaly, and in later stages, we might also see icterus. Don't forget that blue eye appearance that is kind of classic. It is related to this infection, but it's not always seen, so don't rely on it being visible in infected patients.

This is actually, if you think about it, quite a varied presentation. We've got GI signs, so that vomiting, the diarrhea, the abdominal pain. We've got signs of bleeding tendencies

potential renal involvement.

And then in the later stages, when there is progressive hepatic dysfunction and damage, we may see icterus.

Remember that we may see also that blue eye or the corneal edema, but while it is associated with this infection, it is not always seen in every case. So don't rule out canine infectious hepatitis if you don't see this blue eye presentation.

Diagnosis

this disease can look a bit like some different GI diseases. It can look like a sepsis or toxin exposure or leptospirosis. So it can actually be misdiagnosed early on and can be quite tricky to diagnose. So what are we going to do in this case to make sure that we get the right diagnosis? So first up, we are going to run a hematology and biochemistry.

Things we might see are going to be a leukopenia in the early viral phase, followed by a leukocytosis if the condition has progressed. We can see thrombocytopenia, elevated liver enzymes, so that ALT, AST, hyperbilirubinemia, and prolonged clotting times. So these findings are going to suggest that liver involvement, we're seeing those elevated liver enzymes, hyperbilirubinemia, and then also the coagulopathy element, the prolonged clotting times and the thrombocytopenia.

We may also do a urinalysis, which is likely to show renal casts and proteinuria from the glomerular and tubular injuries, and then possibly bilirubinemia if there is severe icterus.

PCR tests can be used to detect viral DNA. We can do this on blood samples, on faeces, on ocular nasal swabs, and they are very useful, but they're not immediately available in GP, so they may not be possible off the bat. Serology is another test option. So this is going to require two consecutive tests to prove that there is an increase.

And generally, we look for a four-fold increase in antibody titers, and that will suggest a positive result. So Essentially, as the infection progresses, as the body mounts an immune response, we're gonna see increases in antibody production and antibody levels, and that is gonna suggest infection. If we're not seeing an increase in antibody production, it doesn't indicate that the body is responding to an infection.
It's worth remembering, though, that recent vaccination can affect this test, so it might be tricky to interpret in vaccinated dogs. It's also not very useful in the acute setting because we are needing that fourfold increase in titers, so waiting for those test results can delay diagnosis and treatment if we're waiting for results to come back.

Histopathology of the liver is going to be a quote, unquote, "gold standard test." It's rarely done. You need a liver biopsy, which is going to either be percutaneous or surgical, um, and you're looking for hepatic necrosis and viral inclusion bodies within hepatocytes just to show that the virus is infecting the liver.
But it's not a test that we're gonna be reaching for, especially in acutely unwell patients. They're not prime candidates for a liver biopsy, so this isn't widely done for diagnosis. So in reality, in practice, diagnosis is often gonna be based on the signalment, so a typically young or potentially unvaccinated dog, the clinical signs, those changes on lab work. So looking for that liver involvement, looking for the coagulopathy signs and then further testing the PCR and the serology.

But because these cases are so emergent, we shouldn't be waiting for definitive confirmation before starting treatment if the results are gonna take a while. So once the condition is suspected, get started on your treatment plan.

Treatment

There is no specific antiviral treatment for CAV 1, so treatment focuses on aggressive supportive care.
So first of all, we're gonna consider fluid therapy, and this is used to correct the hypovolemia and to support tissue perfusion. And also consider whether the fluid needs to be supplemented with anything like dextrose or electrolytes if we have some deficiencies. To manage coagulopathies, we could use fresh frozen plasma to replace those clotting factors or whole blood if there is anemia.

We can use hepatoprotectants for liver support, so a couple of options includes silymarin, vitamin E, N-acetylcysteine, and SAMe. We also consider nutritional support or parenteral nutrition if the dog isn't eating or if they're vomiting enough that they can't eat.

Also consider placing a feeding tube if necessary if they're just not eating or actually they just can't get enough in.

For the vomiting and GI support, we can give maropitant or ondansetron to prevent vomiting and, nutritional support.

And consider some gastroprotectants like sucralfate or omeprazole if vomiting has been severe or chronic.
While we're treating these patients, we do need to be really careful with our monitoring, so watching those electrolytes, glucose levels, clotting times, PCV and total protein, and liver enzymes. We just wanna make sure that all these values are trending in the right direction, as this is gonna be a good indicator that the supportive care is working.

Prevention

Okay, let's talk a little bit about prevention.

First up is vaccination. As we said before, we have the core canine vaccine of CAV-two, which is that kennel cough virus, not the hepatitis virus, but it provides cross-protection against CAV-one, which is gonna be the cause of canine infectious hepatitis. The reason we don't vaccinate with CAV-one directly is because older vaccines cause that blue eye response with the immune complex deposition, and it can also cause kidney inflammation.

So we now use the CAV-two instead. Basically offers the same protection, but it has fewer side effects. The other aspects of prevention are, of course, going to be really good hygiene. CAV-one is actually non-enveloped and very stable in the environment, so it can survive for weeks and months. So good hygiene, isolation of infected dogs, disinfection with dilute bleach or steam cleaning are gonna be some of the only effective methods.

A lot of these standard disinfectants are actually ineffective, so we really need to focus on good biosecurity, good hygiene practices in order to prevent further spread.

Key Points

Okay, what are the key things that you need to know about canine infectious hepatitis before you go? So CAV-one is the cause of canine infectious hepatitis. The virus mainly targets endothelial cells and hepatocytes, which leads to vasculitis and hepatitis.

Clinical signs are often quite acute. We see lethargy, vomiting, abdominal pain, and petechiae. That blue eye Sign is due to immune complex deposition causing corneal edema. While it is associated with the infection, it is not a prerequisite for infection, so don't assume they aren't infected if you don't see blue Diagnosis is often based on clinical presentation and lab work with PCR used for confirmation. But remember that definitive diagnosis should not be prioritized over starting your supportive care treatments. And then your treatment is gonna be aggressive supportive care because there is no direct antiviral cure.
And then finally, for prevention, vaccination with CAV two provides effective protection and should be given as part of the core vaccine protocol as a puppy.

Outro

And that is canine infectious hepatitis. It is something that all vets should know about and be able to recognize. It's one of our core canine vaccines and definitely one to be able to explain to owners on the importance of these key vaccines. Thank you so much for listening to this episode. If you found it helpful, follow or subscribe wherever you get your podcasts, wherever you listen to this podcast, and share it with someone who needs a refresher on this condition as well. Thank you again to our lovely listener for requesting this episode.

If there's a topic you wanna hear us cover next, come and find us on Instagram or on TikTok, @veterinaryvista or let us know what you wanna hear in the comments below. We'll see you next time.