Diagnosis, Prevention and Treatment of Infectious Canine Hepatitis

Infectious canine hepatitis is an acute, highly contagious, septicemic infectious disease of dogs caused by canine adenovirus type I, characterized by circulatory disturbance, central necrosis of the hepatic lobules, and intranuclear inclusion bodies in the liver parenchyma and endothelial cells. Dogs and foxes are highly susceptible, and coyotes, raccoons and black bears are also susceptible. It can also infect humans, but does not cause clinical symptoms.

The pathogen, canine infectious hepatitis virus, belongs to the family Adenoviridae and the genus Mastadenovirus, and has only one antigenic type. The virus is quite resistant; it can survive on contaminated objects for 10 days to 14 days, can survive at room temperature for 10 weeks to 16 weeks, and remains infectious after 30 minutes at 56°C, and is only killed after 3 minutes to 5 minutes at 60°C. It is tolerant to lipid solvents such as ether and chloroform. Phenol, iodine tincture and caustic soda are commonly used effective disinfectants.

Epidemiology: This disease is widespread, and can occur in all four seasons, regardless of age or sex, but it occurs more frequently in young dogs under 1 year of age, and dogs aged 2 months to 3 months are the most susceptible. The disease has a high incidence, and the mortality rate ranges from 25% to 40%. Dogs that recover can acquire lifelong immunity, but they still carry the virus and can shed it in their urine for as long as 6 months to 9 months. Sick dogs and recovered dogs are the main sources of infection; the virus is shed from the body with the sick dog's vomit, saliva, feces, urine and other secretions and excretions, contaminating food, drinking water, utensils and the surrounding environment. Healthy dogs become infected through the digestive tract, and infection through the placenta also occurs.

Clinical symptoms: The incubation period is usually 3 days to 5 days, and the most acute cases often die within 12 hours to 24 hours after the onset of symptoms. Most cases have a course of 10 days to 15 days. In acute cases, the dog is initially afraid of cold and has poor spirit and appetite, then its body temperature rises to 40°C to 41°C, persists for 1 day to 2 days, then drops to normal, and rises again after 4 days to 5 days. At this point, the sick dog completely loses its appetite, is thirsty and drinks eagerly, and commonly shows vomiting, diarrhea, serous to mucoid discharge from the eyes and nose, abdominal pain and moaning. The oral mucosa is congested and bright red, the tonsils are inflamed, the submandibular lymph nodes are obviously swollen, and palpation of the liver area reveals pain and enlargement, with the sick dog moaning in pain. On palpation of the left anterior abdomen, the spleen is enlarged. Subacute cases have mild symptoms. The sick dog's body temperature rises slightly, a few have edema of the head, neck and lower abdomen, with increased heart rate and accelerated breathing. During the recovery period, about 15% to 20% of sick dogs develop temporary corneal opacity in one or both eyes (uveitis), commonly called hepatitis blue eye, which is mostly temporary, and in a few cases can cause permanent damage or even blindness. Most recover or die within 2 weeks. The mortality rate of puppies is about 20%. Most adult dogs are able to survive.

Pathological changes: The main lesions on necropsy are systemic septicemic changes, commonly subcutaneous edema, and hemorrhagic spots of varying sizes on parenchymal organs, serous membranes and mucous membranes. There is abdominal effusion, and the ascites is blood-tinged. The liver is enlarged in appearance with blunted edges. The gallbladder is enlarged and full of bile. The gallbladder wall is highly edematous, thickened and hemorrhagic, appearing dark red, which is a characteristic lesion. The kidneys are enlarged, and the mesenteric lymph nodes are hemorrhagic.

Diagnosis: A preliminary diagnosis can be made based on clinical symptoms, epidemiology and pathological changes. Because this disease often occurs as a concurrent infection with canine distemper, care must be taken in clinical examination. Confirmation requires virus isolation and serological diagnosis. Artificial infection causes disease in foxes and dogs, but cannot cause disease in ferrets.

Prevention and control measures: Vaccination: Regular vaccine immunization of dogs can effectively prevent the occurrence of this disease. Puppies receive their first immunization at 45 days of age, and are given booster immunizations at 60 days and 75 days of age. Starting from the second year, they are vaccinated once every six months, and each dog receives one vial of vaccine each time regardless of size. The domestic canine five-combined vaccine has good immune effects against canine parvovirus, rabies, infectious canine hepatitis and canine parainfluenza, and in particular its immune protection rate against infectious canine hepatitis and canine parvovirus is close to 100%. According to expert estimates, the vaccination rate for canine vaccines is less than 10%, mainly because people have a weak awareness of vaccinating dogs. Therefore, expanding the coverage of canine vaccination and increasing immunization density is the key to controlling this disease.

Treatment of sick dogs: The mortality rate of puppies with this disease is high, and there is currently no specific drug treatment, so comprehensive treatment is usually adopted. In the early stage of the disease, use hyperimmune serum or whole blood, serum or plasma from recovered dogs, or gamma globulin for treatment, injected subcutaneously, once every other day, for 2 to 3 consecutive times, which can inhibit virus replication and spread; use 150 ml of 5% glucose saline, add 250 mg of Vc, 150 mg to 200 mg of VB12, 1 ampoule of coenzyme A, 1 ampoule of ATP, and 1 ampoule of inosine, injected intravenously, once daily, to correct water and electrolyte disturbances; use 1 ml of 30% florfenicol and 2 ml of compound astragalus polysaccharide, injected intramuscularly, once daily, to control concurrent and secondary infections; take 2 to 3 tablets of glucurolactone orally, three times daily, to protect the liver and gallbladder.

Control measures: Once an outbreak occurs, isolation measures should be strictly implemented to avoid direct and indirect contact between sick dogs and healthy dogs, and dead dogs should be burned and buried deep. Dog kennels, grounds and feeding utensils should be disinfected with 3% sodium hydroxide solution, and newly introduced dogs should be isolated and observed for no less than 15 days. For healthy dogs, emergency immunization with the five-combined or six-combined vaccine should be carried out, or during an outbreak of this disease, puppies under 1 year of age should be injected subcutaneously with adult dog serum once a week, 3 ml to 5 ml each time, which can effectively control the outbreak.