Herpesvirus Infection in Important Pets: Why Testing is Essential By Assoc. Prof. Dr. Sompote Weerakul, DVM (Ajarn Kaew) and Dr. Paweena Kongsanan, MT.

Herpesvirus Infection in Important Pets: Why Testing is Essential
By Assoc. Prof. Dr. Sompote Weerakul, DVM (Ajarn Kaew) and Dr. Paweena Kongsanan, MT.

Herpesviruses cause a wide variety of diseases; in humans, they are well-known for causing cold sores. They are classified as DNA viruses. This virus family is divided into three subfamilies: Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae. Combined, these subfamilies contain over 100 species that infect both humans and animals.

However, the Alphaherpesvirus group is the most significant when it comes to causing disease. In humans, this includes herpes simplex (HSV-1 and HSV-2) and chickenpox (Varicella-zoster virus, VZV). These viruses are also widespread in animals. Pet owners should be aware of them and regularly test for the disease, particularly when introducing new animals (for quarantine purposes) or when clinical signs appear to confirm a diagnosis.

Dogs and Cats
Alphaherpesvirus infections are found in both dogs and cats:

Cats (Feline herpesvirus, FHV-1): The virus primarily affects the respiratory system, particularly the upper respiratory tract. It is highly common and is associated with nearly 50% of sick cats presenting with respiratory signs.
Dogs (Canine herpesvirus, CaHV-1): While respiratory and gastrointestinal signs can occur, the primary issues are often linked to the reproductive system. The infection is particularly severe in young puppies from birth up to 3 weeks of age. Symptoms include coughing, abdominal distension, diarrhea, and petechial hemorrhages due to low platelets, which can be fatal. As dogs age, the severity of symptoms decreases; most older dogs remain asymptomatic but act as carriers.
Livestock
Livestock experience a variety of herpesvirus infections, including Bovine herpesvirus in cattle, Equine herpesvirus in horses, and similar infections in goats and sheep:

General Signs: These viruses typically cause rhinitis, conjunctivitis, and bronchitis (such as Infectious Bovine Rhinotracheitis), leading to nasal and ocular discharge. Secondary bacterial infections can lead to pneumonia. Purulent reproductive tract diseases are also observed.
Horses: The virus can cause neurological diseases and encephalitis.
Note: Generally, symptoms in livestock are relatively mild with low mortality rates.
Exotic Pets (Birds)
In exotic pets, herpesvirus infections are highly prevalent and diverse depending on the species:

Pacheco’s disease (PsHV-1): Frequently mentioned in parrots, though diagnostic capabilities for this are often limited in Thailand. It is a severe disease causing sudden death, with non-specific "sick bird" signs such as diarrhea, lethargy, and anorexia. It is most commonly found in Eclectus parrots, followed by African Greys, Macaws, Cockatoos, and Conures. Birds that survive the infection often develop gastrointestinal papillomas and exhibit stunted growth.
Poultry/Other Birds: Another significant herpesvirus disease is Infectious laryngotracheitis.
Reptiles
Because the virus affects multiple organs, multi-systemic symptoms are common. Reptiles are usually brought to veterinarians presenting with anorexia and lethargy:

Turtles & Tortoises: Infections have been reported in both freshwater and sea turtles. The virus frequently causes stomatitis (mouth rot), dermatitis, hepatitis, and hepatomegaly (enlarged liver). In tortoises, symptoms include vomiting/regurgitation, stomatitis, and nasal/ocular discharge from both the upper and lower respiratory tracts.
Snakes & Lizards: Stomatitis and regurgitation are common. In some cases, the virus is implicated in neurological signs in snakes, particularly pythons and boas. Infections have also been reported in iguanas and crocodilians.
Primates
Primates share a close biological relationship with humans, but different species have varying susceptibilities to herpesviruses:

New World Monkeys (e.g., Marmosets): Herpes simplex virus (HSV-1 and HSV-2) from humans can be fatal to them. Sometimes referred to as the "kissing death," this transmission occurs through contact with human carriers, resulting in high morbidity and mortality. Additionally, Saimiriine herpesvirus-1 (SaHV-1) causes outbreaks in squirrel monkeys and marmosets with a 76–100% mortality rate.
Old World Monkeys (e.g., Macaques): These monkeys can carry Cercopithecine herpesvirus-1 (B virus). While it causes only mild symptoms in the monkeys, transmission to humans leads to severe illness with a mortality rate that can exceed 70%.
Conclusion
The diseases detailed above are all caused by viruses in the Alphaherpesvirinae subfamily. While many other diseases are caused by different types of herpesviruses, the most significant and frequent ones belong to the alpha group. Their danger level correlates directly with the specific animal's susceptibility. Therefore, testing for alphaherpesviruses is crucial and necessary when there is a risk of an outbreak, when introducing new primates or animals to a group, and whenever clinical signs of illness appear.