Prevention and treatment of canine parvovirus disease

1 Introduction to the pathogen

The pathogen of canine parvovirus disease is canine parvovirus (CPV), which belongs to the Parvoviridae family and the Parvovirus genus. Under an electron microscope, CPV virus particles are round or hexagonal in appearance, without an envelope structure, and have a diameter of approximately 20 to 24 nm[1]. The viral genome is a single-stranded negative-strand DNA virus consisting of approximately 5,200 nucleotides[2].

CPV has a strong resistance to external physical and chemical stimulation. When stored at room temperature for 90 days, its infectivity only decreases slightly, and it can survive in feces for months to years. When stored at low temperatures, its infectivity does not change significantly. The virus is insensitive to common disinfectants such as ether, alcohol, and chloroform, but it has significant effects on ultraviolet rays, oxidants, and formalin. Therefore, dog owners need to choose the correct disinfection method to kill CPV to prevent the spread of CPV.

2 Epidemiology

Canine parvovirus was first isolated from the feces of sick dogs by Australian and Canadian scholars in 1978. Since then, the virus has quickly spread to dog-raising countries around the world. my country first reported and confirmed the existence of the disease in 1982 [3]. Since then, the disease has occurred and spread in purebred dogs and police dogs in Northeast my country, East China, and Southwest China. In general, canine parvovirus can infect in all seasons without obvious seasonality, but the incidence rate is higher in winter and spring. There is no significant difference in infection between different breeds of dogs. The incidence rate of purebred dogs is significantly higher than that of hybrid dogs, and the mortality rate is higher [4].

Sick dogs are the main source of infection for this disease. Their vomit and feces contain a large amount of viruses, and the viruses exist in the excrement for a long time, making it difficult to eliminate canine parvovirus in the external environment. After recovery, sick dogs will become hidden sources of infection, excreting toxins through feces for a long time, contaminating feed, drinking water, tableware, and the surrounding activity environment. Newborn puppies are generally rarely infected due to the presence of maternal antibodies, but they are susceptible after 2 months of age. When feeding and management conditions change, such as long-distance transportation, sudden temperature changes, sudden changes in diet and other stress factors can promote the occurrence of the disease. Poor hygiene conditions, improper care, and secondary infection will aggravate the condition.

3 Clinical symptoms

The incubation period of the disease is 7 to 14 days. Clinically, the disease is characterized by hemorrhagic enteritis and myocarditis as the main symptoms, so it is divided into enteritis type and myocarditis type. A few cases show a mixture of the two types. The main clinical manifestation of the current popular canine parvovirus infection is hemorrhagic enteritis [5]. In the early stage, enteritis-type dogs show depression, loss of appetite, occasional fever, vomiting, and yellow or grayish-yellow loose stools. Subsequently, vomiting develops more frequently, and soy sauce-like or tomato juice-like loose stools are discharged. The diarrhea is mixed with blood and accompanied by a special fishy odor. At this time, the sick dog quickly develops a series of dehydration symptoms such as sunken eye sockets, dry mucosa, and inelastic skin. Frequent vomiting and diarrhea lead to electrolyte disorders. In the late stage, the white blood cell count of the sick dog will decrease significantly, and the limbs will become cold, shock or even death will occur. Myocarditis is common in puppies under 8 weeks of age. There are usually no premonitory symptoms, or only mild diarrhea, followed by sudden groaning, weakness, dyspnea, cyanosis of the mucous membranes, and murmurs in the heart. It is usually too late to treat the dog and the dog dies within a few hours. Autopsy shows dilatation of the heart, degeneration and necrosis of myocardial fibers, which are signs of heart failure. A mixed type of the two will show typical symptoms of both enteritis and myocarditis. In most cases, enteritis symptoms appear first, followed by myocarditis symptoms, and the mortality rate is high [6].

4 Diagnosis basis

It is generally not difficult to make a preliminary diagnosis based on clinical symptoms, but laboratory diagnosis is still required for confirmation. In the past, hemagglutination and hemagglutination inhibition tests were often used to collect feces from sick dogs, and the supernatant was centrifuged and tested. Virological detection can generally be observed by electron microscopy after negative staining with phosphotungstic acid, and round or hexagonal virus particles with a diameter of 20 to 24 nm can be seen. Immuno-electron microscopy can also achieve good results for the virus. Animal hospitals often use rapid detection methods. After collecting feces from sick dogs, they use canine parvovirus rapid diagnosis kits for detection. If positive, the diagnosis can be confirmed. Another method is to use colloidal gold detection plates for detection. Take sick dog feces and dilute it in a diluent, mix it, let it stand, take the supernatant and drop it on the colloidal gold detection plate, and read the results after 5 minutes. If both the test line and the control line are red, it can be diagnosed as canine parvovirus disease. This method is fast, simple and easy to operate. There are many reports on the use of polymerase chain reaction (PCR technology) to detect the virus, but it is less commonly used in practice.

5 Treatment

5.1 Symptomatic treatment

The key to treating this disease is symptomatic treatment. Symptomatic treatment is carried out according to the clinical symptoms of the sick dog. If vomiting occurs, appropriate antiemetic drugs such as metoclopramide and antacid can be given. Once the gastric mucosa is damaged, pet-specific sucralfate tablets can be taken orally to promote the healing of the ulcer surface. For bleeding symptoms, calcium and vitamin K supplementation can be paid attention to, which can effectively relieve the symptoms. If the bleeding is severe, phensulfonamide injection (hemostatic) can be given. Antiviral drugs for this disease generally use canine parvovirus monoclonal antibodies, high-immune serum, and broad-spectrum antiviral recombinant canine interferon [7]. The first dose is doubled. At the same time, attention should be paid to the prevention and treatment of diarrhea. To prevent secondary infection, broad-spectrum antibiotics such as ampicillin sodium can generally be used.

5.2 Replenishing body fluids and maintaining electrolyte balance

According to clinical examination, the dehydration of sick dogs can be roughly judged. Generally, the degree of dehydration can be judged according to the elasticity of the skin, capillary refill time, degree of mucosal dryness, degree of eye socket depression, and whether mental depression occurs, so as to perform fluid rehydration. Fluid rehydration requires accurate calculation of the amount of fluid rehydration and the infusion rate. If conditions permit, it is recommended to use a pet-specific infusion pump to monitor the infusion volume and infusion rate to avoid excessive fluid rehydration. Most pet hospitals now use blood gas analyzers to detect the lack of ions and the body's pH, which can quickly correct electrolyte imbalance problems. Appropriate supplementation of nutrient solution, glucose, coenzyme A, inosine, and vitamin C are given to maintain the basic physical fitness of dogs and enhance the body's resistance. In order to maintain the plasma colloidal osmotic pressure of sick dogs, appropriate amounts of special hydroxyethyl amylase, canine blood albumin, etc. can be given.

5.3 Nursing

The sick dog should pay attention to monitoring the body temperature and keep warm. An incubator can be used. If conditions do not allow, an electric blanket can also be used. After 3 to 4 days of the above comprehensive treatment, if the dog is not dead, it can generally recover. After that, the sick dog will not vomit frequently or have bloody stools. If the dog has a certain appetite, a small amount of easily digestible dog food can be given, and probiotics and other digestive additives can be added to help it recover as soon as possible.

6 Prevention and Control

The prevention method of canine parvovirus disease is timely vaccination, strengthening feeding management, thoroughly disinfecting the environment, and reducing the occurrence of stress. Vaccination is currently the most commonly used and most effective means of prevention. At present, the common vaccines for preventing canine parvovirus disease are homologous inactivated vaccines, homologous attenuated vaccines, heterologous inactivated vaccines, and heterologous attenuated vaccines. Vaccines commonly used in pet hospitals include domestic CPV inactivated vaccines, pentavalent attenuated vaccines, hexavalent attenuated vaccines, Pfizer Weijia 5 and Weijia 8 in the United States, and Intervet hexavalent vaccine in the Netherlands. In the prevention of canine parvovirus disease, immunization time and immunization procedures are equally important. Usually, the first immunization is carried out when the puppy is 10 to 12 weeks old. This period is the peak period of parvovirus disease. The first immunization can be carried out at 6 weeks of age, followed by a booster immunization after 21 days, and then another booster immunization after an interval of 21 days. Usually, it can produce a one-year immune protection effect. You can also go to the pet hospital to test the antibody level. After that, you can have a booster immunization once a year. Before completing the immunization procedure, try to avoid contact with other dogs and environments that may be infected.

7 Summary

Canine parvovirus is one of the highly contagious diseases of dogs. It is difficult to treat. However, with the development of science and technology and the continuous improvement of the medical level of pet doctors, the cure rate of the disease has been significantly improved. However, the disease mostly occurs in puppies. With the large-scale circulation of pet dogs, it will lead to changes in the environment and dog food. In addition, short-distance or long-distance transportation will cause stress, which can easily cause the disease. In the early stage of the disease, most breeders did not discover it in time and did not pay enough attention. They did not seek medical treatment until obvious clinical symptoms appeared, which undoubtedly made the treatment of the disease extremely difficult. Once the disease occurs, it is recommended that pet owners discover and treat it early to strive for the best treatment time and reduce the harm caused by parvovirus disease.