Canine Herpesvirus: The Hidden Threat to Puppy Health

Canine herpesvirus (CHV) is a contagious virus that affects dogs, especially newborn puppies. This virus is part of the herpesvirus family and can cause serious illness in young pups, often leading to death within the first few weeks of life. In adult dogs, CHV usually shows no symptoms or only mild signs, but they can still spread the virus to others. Understanding CHV is important for dog breeders and pet owners alike, as early detection and prevention can help protect vulnerable puppies.

E­tiology/Pathophysiology

Etiology 

• Agent is a DNA virus from the Herpesviridae family.

• Infects dogs through:

  • In utero transmission (from infected dam to fetus),

  • During birth (through the birth canal),

  • Contact with oronasal secretions from infected dogs.

• Naïve pregnant females are at high risk of severe infection leading to reproductive failure.

• Spread can also occur through contact with other dogs shedding the virus, even without visible symptoms.

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Pathophysiology 

• Targets mucosal epithelial cells and lymphoid tissues for replication.

• Virus replicates best in cooler body temperatures (below 98.6°F), especially in areas like the nasal and genital mucosa.

• In neonatal puppies (<3 weeks):

  • Body temperature is not well-regulated, allowing rapid viral replication.

  • Results in systemic viremia, often leading to sudden death.

• In pregnant dogs:

  • Primary infection can cause viremia, leading to fetal death, abortion, or mummification.

• CHV enters a latent phase after initial infection:

  • Resides in nerve ganglia or lymphoid tissue.

  • Can reactivate during stress, leading to virus shedding and potential transmission.

• Previously exposed dams:

  • Typically asymptomatic.

  • Pass on temporary passive immunity to puppies through colostrum.

• Older puppies and adults:

  • Usually develop mild clinical signs, such as:

    • Respiratory issues,

    • Ocular infections,

    • Genital lesions.

Epidemiology

• Canine herpesvirus (CHV) is a widespread viral threat found in various canine species, including domestic dogs, coyotes, and wolves, across the globe.

• Surveys conducted across Europe reveal a high antibody presence, with 39% to 88% of dogs showing signs of past exposure.

• The virus spreads more easily in group settings, making kennels, shelters, and breeding facilities high-risk environments for transmission.

• Recent shelter-based studies suggest CHV may contribute to the canine infectious respiratory disease complex (CIRDC), pointing to its role as a possible underlying cause of respiratory illness in dogs.

Signalment

• Neonatal Risk (0–3 Weeks):
  Puppies under 3 weeks are highly vulnerable to severe illness and death due to immature immune systems and limited defenses.

• Older Dogs (3+ Weeks):
  Male and female dogs over 3 weeks typically develop only mild symptoms. Infections are often less severe but may recur periodically.

• Note
  Age is a key factor: puppies under 3 weeks face life-threatening risks, while older dogs generally experience milder, recurring infections.

Infection History and Clinical Signs in Dogs

Transmission and Exposure

• The virus spreads from infected dogs to healthy ones by direct contact.

• Common in places where many dogs are housed together, such as kennels, shelters, and breeding facilities.

• Stressful conditions can reactivate latent infections in dogs previously exposed.

Risk Factors

• Dogs with weakened immune systems are at higher risk of repeated infections.

• Conditions impairing immunity include diabetes, immune system disorders, and cancers like lymphoma.

• Young puppies (1 to 3 weeks old) are especially vulnerable to severe disease.

Clinical Signs in Neonatal Puppies (1–3 weeks old)

• General signs: lethargy and poor appetite.

• Respiratory distress: rapid or labored breathing.

• Gastrointestinal issues: diarrhea with soft, yellow, or greenish stools.

• Persistent, intense crying indicates pain or discomfort.

• Abdominal tenderness when touched.

• Small pinpoint hemorrhages (petechiae) on mucous membranes (e.g., gums, mouth).

• Occasional blister-like (vesicular) lesions on the genital area.

• Rapid disease progression, with death often within 1–2 days after signs appear.

• Survivors of the acute phase may develop neurological problems.

Clinical Signs in Older Puppies and Adult Dogs

• Signs of upper respiratory infection: sneezing, nasal discharge, mild cough.

• In some cases, the disease may progress to pneumonia (lower respiratory tract).

• Genital infections show as vesicles or small blisters on the genital mucosa.

Ocular Signs

• Conjunctivitis: redness and irritation of the eye’s conjunctivae.

• Corneal involvement: ulcers or keratitis (corneal inflammation).

• Blepharospasm: involuntary tight eyelid closure due to pain.

• Photophobia (light sensitivity) and eye discharge are common.

D­iagnosis

• Gathering a detailed medical background, observing clinical symptoms, conducting a physical assessment, and identifying any signs of stress or immune system compromise are essential steps to raise suspicion of an infectious process.

• In neonatal patients, bacterial bloodstream infection (sepsis) remains the leading condition to differentiate from other causes.

• Canine herpesvirus (CHV) can be isolated by culturing samples from multiple internal organs such as the liver, spleen, kidneys, and lymph nodes, especially in puppies that have died due to widespread infection.

• Older dogs showing symptoms related to reproductive health, respiratory distress, or eye inflammation typically release the virus via the mucous membranes of the mouth or genital tract, making these locations ideal for collecting diagnostic specimens.

• When the virus is present in the bloodstream (viremia), whole blood preserved with an anticoagulant like EDTA can be utilized for successful viral isolation.

• Various diagnostic techniques are available for detecting CHV, including polymerase chain reaction (PCR) to identify viral DNA, immunofluorescence assays to visualize viral antigens, and electron microscopy for direct observation of viral particles.

• Blood tests measuring antibodies to CHV confirm that the animal has been exposed to the virus at some point, but positive serology does not necessarily indicate an active infection at the time of testing.

Differential diagnosis by :

• Canine Parvovirus Infection

• Canine Distemper

• Bacterial Septicemia

• Neonatal Septicemia

• Canine Adenovirus Infection

• Canine Coronavirus

• Fading Puppy Syndrome

• Toxoplasmosis

• Neosporosis

• Hypoglycemia in Puppies

• Congenital Defects

• Other Viral Neonatal Infections

Treatment 

• There are very few treatment options for puppies with CHV right now.

• Supportive care is the most important thing.
  This means keeping the puppy warm, fed, and comfortable.

• Some vets suggest giving 1–2 mL of special blood serum from mother dogs that had CHV puppies before.
  This may help protect sick or exposed puppies.

• Keeping puppies warm may slow down the virus and help prevent illness in puppies who aren’t showing signs yet.
  But this doesn’t work once the puppy is already sick.

• There are no approved medicines for CHV in dogs right now.

• Some antiviral drugs like acyclovir or vidarabine have been tried, but they can be dangerous, and we don’t know yet if they work well for puppies.

• There is no CHV vaccine in the U.S., but a vaccine is available in Europe for breeding dogs.

• More research is needed to find safe and effective treatments.

Prognosis:

This disease tends to be highly fatal in neonates, largely due to their immature immune systems and underdeveloped thermoregulatory mechanisms. In contrast, older animals with a robust immune response and effective thermoregulation typically experience mild or even subclinical manifestations. Notably, immunosuppressed individuals are at risk for reactivation of latent infections, which may lead to renewed clinical signs.

Public Health concern:

Canine herpesvirus (CHV), consistent with other herpesviruses, exhibits strict host specificity and poses no zoonotic risk. To date, there is no evidence of CHV infection in humans, making it a concern solely within canine populations.

What is Canine Herpesvirus (CHV)?
CHV is a species-specific herpesvirus that primarily affects dogs, especially newborn puppies.

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FAQ’S

2. How is CHV transmitted?
It spreads through direct contact with infected secretions or from mother to pup during birth.

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3. Who is most at risk?
Newborn puppies are at the highest risk, while adult dogs may carry the virus without symptoms.

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4. Can CHV be controlled or prevented?
Yes. Isolation of infected animals, stress reduction, and vaccination (where available) can help prevent outbreaks.

Conclusion

Canine Herpesvirus lurks as a hidden threat, especially to vulnerable newborns. Understanding its subtle spread and serious impact helps pet owners, breeders, and veterinarians take timely action. With vigilant care, proper hygiene, and informed prevention, CHV doesn’t have to be a silent killer—it can be a manageable risk in a well-protected canine community.