Infectious Canine Hepatitis | Hepatitis in Dogs

Cause of Infectious Canine Hepatitis

Infectious canine hepatitis is caused by canine adenovirus 1 (CAV-1). This virus is antigenically related to canine adenovirus 2 (CAV-2), the causative agent of kennel cough in dogs. CAV belongs to the family Adenoviridae, genus Mastadenovirus.

Some Characteristics of Canine Adenoviruses

A non-enveloped double-stranded DNA virus
Antigenically related to CAV-2
CAV-1 is icosahedral
Resistant to chloroform, ether, bile salt, and fluorocarbon but disrupted by acetone
The thermal inactivation point is 56 C
Stable at -20C and pH of 5-6

Carter, G.R.; Wise, D.J. (2006)

Host Susceptibility

Canine adenovirus 1 causes the infection in dogs, wolves, foxes, coyotes, skunks, and bears. Ferrets are not susceptible.

Note: Young dogs, in the first 2 years of life, are more likely to die of the infection than older dogs

Transmission & Pathogenesis of Infectious Canine Hepatitis

A healthy dog can contract CAV-1 by direct contact with an infected dog or through indirect contact with contaminated objects like hands, utensils, and clothing. CAV-1 is shed in the saliva, feces, and urine of infected dogs. Fleas and ticks can also spread the virus from infected animals to healthy one. In such transmission, fleas, and ticks act as mechanical vectors. Transmission through airborne routes is yet not been reported. Recovered dogs shed virus in their urine for ≥ 6 months.

The virus first replicates in the tonsils and local lymph nodes after entering the body. Afterward, the virus enters the bloodstream. Hepatocytes and endothelial cells in a number of tissues, including the lungs, liver, kidneys, spleen, and eye, become infected as a result, leading to hemorrhage, necrosis, and inflammation.

The virus starts infecting the Kupffer’s cells in the liver before moving on to infect hepatocytes.

Note: The virus replicates in the nucleus of host cells and causes severe condensation and margination of nuclear chromatin, surrounded by a clear zone that separates them from the marginated chromatin. (Important Clinicopathological finding).

Clinical Findings of Infectious Canine Hepatitis

The incubation period of infectious canine hepatitis is 4 to 9 days. The first symptom is typically a fever that is >40°C (104°F), lasting 1-6 days, and typically biphasic in nature. If the fever is transient, leukopenia may be the only additional symptom. The clinical findings of infectious hepatitis in dogs are

Tonsillitis, conjunctivitis
Inappetence, lethargy, weakness
Polydipsia
Vomiting
Hematemesis
Diarrhea sometimes with frank blood
Cough
Tachypnea
Icterus
Serous oculonasal discharge, or corneal clouding (blue eye) due to replication of the virus within corneal endothelial cells

Note: Neurologic signs such as seizures, ataxia, circling, apparent blindness, head pressing, and nystagmus have been reported in association with CAV-1 but such cases are rare (Caudell et al., 2016).

dog with corneal clouding due to infectious canine hepatitis — **Corneal clouding**

conjuctivitis in dogs due to hepatitis — **Conjunctivitis in dog**

dog is coughing because of infectious canine hepatitis — **Cough in dog**

Postmortem findings of infectious canine hepatitis in dogs

Hemoabdomen (blood-tinged ascites)
Enlarged, congested liver
Splenomegaly
Enlarged, congested, and edematous lymph nodes
Fibrin deposition on the surface of abdominal viscera

Diagnosis of Infectious Canine Hepatitis in Dogs

Diagnosis of hepatitis in dogs is done on the basis of

History
Clinical signs and Clinicopathological findings
Laboratory confirmatory tests

Note: Any dog younger than a year old with a doubtful vaccination history, symptoms of fever, respiratory, gastrointestinal, or hepatic disease, and most definitely any young dog who develops ocular edema, should be tested for infectious canine hepatitis.

Clinicopathological findings of canine hepatitis

The clinicopathological findings of infectious canine hepatitis in dogs are

Abnormalities in CBC Report

Leukopenia
Anemia
Increased nucleated red blood cells
Moderate to severe thrombocytopenia.

Note: It’s possible for leukocytosis and lymphocytosis to happen during the healing process.

Abnormalities in Serum Biochemical Test Report

Increased activity of serum ALT and ALP
Hyperbilirubinemia
Hypoglycemia, and hypoalbuminemia

Note: Liver enzymes increase due to liver damage.

Urinalysis

Dogs with ICH may have proteinuria, hyaline and granular cylindruria, hematuria, and bilirubinuria on urine results.

Coagulation Profile

Due to thrombocytopenia (decrease in platelets), prolonged prothrombin time decreased factor VIII activity, increased fibrinogen degradation products, and reduced platelet adhesion.

Case Study of Infectious Canine Hepatitis in Clinically ill Dog

Microbiological Tests for Infectious Canine Hepatitis

Traditional PCR methods have been published for the identification of CAV-1 in clinical materials such as blood, nasal, rectal, and ocular swabs, as well as tissue acquired during necropsy. PCR test or restriction fragment length polymorphism is required to conclusively separate CAV-1 from CAV-2.

Differential Diagnosis

Infectious canine hepatitis in dogs must be differentiated from other similar diseases like canine distemper, Kennel cough, and canine parvovirus infection.

Note: In canine distemper, GIT, respiratory, and neurological signs are evident, whereas in parvo-enteritis, respiratory signs, and neurological signs are absent. Conjunctivitis and corneal clouding are important clinical signs of infectious canine hepatitis.

Treatment of Infectious Canine Hepatitis in Dogs

Treatment for canine hepatitis is largely supportive and symptomatic. The principal components of treatment include

1- Fluid therapy

2- Anticoagulant therapy

3- Nutritional support

4- Antibiotic & Antemetic therapy

Fluid therapy

For the correction of acid-base and electrolyte disturbances, fluid therapy must be done. Typically, a balanced isotonic crystalloid solution (such as Lactated Ringers) is the preferred fluid for early rehydration and restoration of intravascular volume.

Ringer Lactate 15ml/kg IV

Anticoagulant therapy

For treating coagulopathy, give a blood transfusion to severely affected dogs.

Nutritional therapy

Improved mucosal integrity, quicker healing, and a consequent decrease in the likelihood of bacterial translocation are all linked to enteral feeding.

Antibiotic & Antemetic therapy

When a dog has hemorrhagic gastroenteritis and there is a chance that there will be bacterial translocation that leads to bacteremia, parenteral broad-spectrum antimicrobial medications should be taken into consideration. Use any broad-spectrum antibiotic. Ampicillin @ 20–40 mg/kg/8 hours IV.

Various antemetic drugs are available like chlorpromazine, Acepromazine, Prochlorperazine, Aminopentamide, Dimenhydrinate, Diphenhydramine, and Maropitant, etc.

Acepromazine (0.025–0.2 mg/kg, IV, IM, SC, maximum 3 mg; 1–3 mg/kg, PO)
Chlorpromazine (0.5 mg/kg, IV, IM, SC, tid-qid)
Aminopentamide (0.022 mg/kg, PO, SC, or IM, bid-tid)
Dimenhydrinate (4–8 mg/kg, PO, tid)
Diphenhydramine (2–4 mg/kg, PO, tid)
Maropitant (2 mg/kg, PO or 1 mg/kg/day, SC, for up to 5 days)

Prevention of Infectious Canine Hepatitis in Dogs

Infectious canine hepatitis can be prevented by effective immunization of dogs. Vaccination is recommended at the time of canine distemper vaccination. Vaccines should be administered every 3 to 4 weeks from 6 weeks of age, with the last vaccine given no earlier than 16 weeks of age.

After receiving attenuated live vaccinations, the duration of immunity is at least three years and most likely longer.

Maternal antibody persists until puppies are 12 weeks of age and interferes with immunization when virus neutralization titers exceed 1:100.

Live, attenuated CAV-1 vaccines have temporarily opaque one or both corneas, and the virus can be excreted in the urine. For these reasons, live, attenuated CAV-2 strains are given preference since they have a very low tendency to cause corneal opacities or uveitis and the virus is not shed in urine. These strains also provide cross-protection against CAV-1.

Additional preventative measures, include adequate disinfection, isolation, avoid overcrowding and interaction with wild animals.

Conclusion

Infectious canine hepatitis is a viral disease that affects young dogs and can be accompanied by a wide variety of clinical signs, ranging from fever and lethargy to hepatic failure, severe coagulopathy, and death.
PCR assay, serologic analysis, or ELISA can all be used to make a diagnosis.
Treatment consists only of supportive care, with the goal of preserving proper nutrition and hydration balance.References

References

Caudell, D., Confer, A. W., Fulton, R. W., Berry, A., Saliki, J. T., Fent, G. M., & Ritchey, J. W. (2005). Diagnosis of infectious canine hepatitis virus (CAV-1) infection in puppies with encephalopathy. Journal of veterinary diagnostic investigation, 17(1), 58-61. Available at https://journals.sagepub.com/doi/abs/10.1177/104063870501700111

Infectious canine hepatitis. (2022, October 19). In Wikipedia. https://en.wikipedia.org/wiki/Infectious_canine_hepatitis

Merck Veterinary Manual. Overview of Infectious Canine Hepatitis, Available at here

ScienceDirect. Infectious Canine Hepatitis. Available at https://www.sciencedirect.com/topics/medicine-and-dentistry/infectious-canine-hepatitis