Canine Herpesvirus Infection: Treatable and Controllabl

Characteristics of Canine Herpesvirus

The canine herpesvirus (CHV) is a highly contagious pathogen that exclusively affects dogs. It is notorious for causing acute, potentially fatal respiratory diseases in puppies under two weeks of age, with a mortality rate that can reach up to 80%. Older puppies may exhibit mild or nonsymptomatic illness, while adult dogs typically show no signs or only mild symptoms such as rhinitis, tracheitis, or vaginitis. Infected and recovered dogs are the primary sources of transmission, as the virus is shed in saliva, nasal secretions, and urine. Puppies are primarily infected during the birthing process by contact with the infected female dog's vagina or by inhaling contaminated droplets. Transmission can also occur among puppies through oral and pharyngeal contact.

Clinical Symptoms

Newborn puppies younger than 21 days can suffer from a deadly infectious disease. Initially, affected dogs may display signs of confusion, depression, loss of appetite, weakness, difficulty breathing, and pain upon abdominal pressure. Some may exhibit rhinitis symptoms, with serous nasal discharge and widespread pinpoint hemorrhages on the nasal mucosa. Skin lesions, characterized by red papules, are common in the inguinal area, the vulva and vagina of female dogs, and the prepuce and oral cavity of male dogs. Affected dogs may eventually lose consciousness, exhibit arching of the back, and have seizures. Most dogs succumb to the disease within 2448 hours after the onset of clinical symptoms. Some recovered dogs may develop permanent arching of the back and seizures.

Dogs older than 21 to 35 days primarily exhibit upper respiratory symptoms such as sneezing, coughing, and dry hacking, which typically last for about 14 days before subsiding. Mixed infections can lead to fatal pneumonia. In female dogs, reproductive tract infections are characterized by diffuse vesicular lesions on the vaginal mucosa. Pregnant females may suffer from abortion and stillbirth. Male dogs may show lesions on the penis and prepuce, along with increased secretions.

Pathological Changes

Fatal infections in newborn puppies are characterized by diffuse hemorrhage and necrosis in the visceral organs, particularly the liver, kidneys, and lungs. The thoracic and abdominal cavities may show serous or mucoid exudates. The lungs are congested and edematous with enlarged hilar lymph nodes. The spleen is congested and enlarged. The intestinal mucosa may exhibit pinpoint hemorrhages, and jaundice and nonsuppurative encephalitis may occasionally be observed.

Differential Diagnosis

1. Canine Herpesvirus Infection vs. Toxoplasmosis: Both conditions present with symptoms like nasal discharge, coughing, sneezing, vomiting, ataxia, and abortion in female dogs. Differentiation includes fever and changes in red and white blood cell counts in toxoplasmosis cases, as well as the presence of tachyzoites in tissue smears after Giemsa or Wright staining.

2. Canine Herpesvirus Infection vs. Canine Distemper: Both conditions have symptoms like anorexia, depression, sneezing, nasal discharge, dry cough, vomiting, and conjunctivitis. Differentiation includes the absence of fever in herpesvirus cases, biphasic fever in distemper, conjunctivitis and keratitis, purulent discharge, marked neurological symptoms, decreased white blood cell count, and detection of canine distemper virus using immunofluorescence tests.

3. Canine Herpesvirus Infection vs. Canine Tuberculosis: Both conditions present with symptoms like dry cough, mucopurulent or purulent nasal discharge, and upper respiratory symptoms. Differentiation includes progressive weight loss, fever, chronic course, and nodules on the reproductive organs and skin in tuberculosis cases.

4. Canine Herpesvirus Infection vs. Canine Colds, Laryngitis, Bronchitis, Pneumonia: These conditions present with symptoms like coughing, nasal discharge, depression, and anorexia, but are not contagious.

5. Canine Herpesvirus Infection vs. Canine Cryptococcosis: When cryptococcosis affects the lungs, it presents with symptoms like coughing, sneezing, increased ocular discharge, or skin infection, and respiratory distress. Neurological symptoms like ataxia and motor dysfunction may occur after neurological infection. Differentiation includes the presence of thickwalled yeast cells in the respiratory and neurological symptoms, along with edema of the skin, and the observation of these cells under a microscope after staining with methylene blue.

6. Canine Herpesvirus Infection vs. Canine Aspergillosis: When aspergillosis affects the nasal cavity and sinuses, dogs may sneeze and have serous or mucoid nasal discharge. Differentiation includes respiratory and neurological symptoms in herpesvirus cases, along with respiratory distress, vomiting, and diarrhea. Additionally, the presence of branching hyphae with septa and连锁状 sporangia at the ends of the hyphae can be observed under a microscope after adding 1 drop of 20% potassium hydroxide to nasal secretions or pus and covering with a coverslip.

Reminders

Based on the acute onset and high mortality in newborn and young puppies, and the diffuse hemorrhage and necrosis in the liver, kidneys, and lungs, a preliminary diagnosis can be made. Confirmation requires pathogen testing.

Preventive Measures

1. Prevention:

① Vaccination: Naturally recovered dogs and dogs vaccinated with attenuated vaccines can produce lowlevel serum neutralizing antibodies, which provide protection against infection. Inoculating newborn puppies with serum from recovered female dogs can prevent infection and death. Since dogs infected with canine herpesvirus can develop immunity, after an outbreak in a litter, subsequent puppies are generally not affected. An inactivated vaccine with adjuvants has been developed to induce a certain level of antibodies in female dogs.

② Pay attention to disinfection of kennel areas, strengthen breeding management, and isolate and treat sick dogs promptly.

2. Treatment:

The treatment principle is to enhance the body's resistance, increase environmental temperature, and prevent secondary infections.

① During outbreaks, intraperitoneal injection of 12 milliliters of high immune serum into puppies can reduce mortality.

② Broadspectrum antibiotics can be used to prevent secondary infections in dogs with respiratory symptoms.

③ Interferon, at 1020 thousand units per dose, can be administered subcutaneously or intramuscularly every other day.

④ Increasing the environmental temperature is beneficial for the recovery of affected dogs. Place the dogs in an incubator or use heaters to maintain a temperature of 3538°C and a humidity of 50%. This can help the dogs recover sooner.