Establishment Of Experimental Infection Pet Cat Model By Feline Herpesvirus Type 1

Feline herpesvirus type 1?FHV-1?belongs to the herpesvirus family,a member of the alpha-herpesvirus subfamily.It is a typical linear double-stranded DNA virus with a capsule,which can cause infectious rhinotracheitis in cats and felid.At present,the disease is prevalent all over the world,but only feline animals are vulnerable for infection,among which young cats aged 2 to 6 months are most susceptible to infection,and the incidence rate is 100%,and the mortality rate can reach 20%-50%.After FHV-1 infection,the body temperature of the diseased cat increased to 39.5-42 degrees C,causing severe upper respiratory tract and eye symptoms,coughing.Because the symptoms of the disease are similar to those of the upper respiratory tract caused by calicivirus,chlamydia,mycoplasma and reovirus,it is difficult to differentiate the symptoms from clinical symptoms.Moreover,the disease is often co-infected with calicivirus and parvovirus,which makes the diagnosis of the disease difficult.Imported vaccines remain the main means of prevention.There is no self-developed vaccine with clinical approval in China.Therefore,the establishment of FHV-1 animal infection model can lay a foundation for the development of FHV-1 vaccine and therapeutic drugs.A strain of FHV-1 was isolated in the early stage in the laboratory and was named as FHV-1 CH-B.After expansion culture,the titer was 10^-7.38TCID₅₀/ml.In this study,animal infection test was first carried out using FHV-1 CH-B strain,and 6-10 weeks old healthy unimmunized Chinese garden cats were inoculated by intranasal inoculation at a dose of 0.5ml/nostril?10-7.38 TCID50/ml?with continuous observation for 11d.By observing clinical symptoms,the pathogenicity of the strain was determined by observing clinical symptoms,histopathological changes,temperature changes,detoxification and virus distribution in tissues.The results of the experiment showed that all cats were vaccinated after the vaccination,and the survival rate was 40%.Detoxification began on the 2nd day after vaccination,and there were symptoms such as elevated body temperature,increased secretion of eyes and nose,sneezing,respiratory vocalization,skin ulcer around the eyes and nose.FHV-1 was not detected in tissues such as liver,spleen,kidney,and heart.This indicates that the FHV-1 CH-B strain is highly pathogenic,and only causes upper respiratory tract infection after infection with cats,and does not cause systemic infection.Therefore,the FHV-1 CH-B strain can be used in subsequent experiments.The FHV-1 CH-B strain was inoculated with 6-10 weeks old healthy unimmunized Chinese garden cats by intranasal,oral or subcutaneous injection.The nasal inoculation dose was 0.5ml/nostril,and 1ml was injected orally and subcutaneously.The virus titer is 10^-7.38TCID₅₀/ml.After 15 days of continuous observation,the best way of inoculation was determined by observing clinical symptoms,histopathological changes,temperature changes and detoxification.The results showed that the body temperature of the cat after the inoculation increased at the 2nd day,and the body temperature reached 40?on the 4th day.Symptoms such as sneezing and serous secretions began to appear on the 3rd day after the inoculation.On the 4th day,the symptoms increased,and the eyes and nose pus appeared.Secretion,difficulty in breathing,depression and other symptoms;the initial temperature fluctuation of cats after oral inoculation was not obvious,the body temperature increased to39.1?on the 9th day,and sneezing,nasal and nasal serous secretions appeared on the 5th day after inoculation;on the 7th day,the symptoms like eye and nose purulent secretion and breathing difficulty were aggravated,.The cats with subcutaneous injection did not show any signs of temperature rise and obvious symptoms.This shows that both intranasal and oral inoculation methods can cause morbidity.The subcutaneous injection method can not cause the disease.The nasal inoculation method causes the fastest onset,the most obvious symptoms and all deaths.Therefore,it is determined that nasal drip inoculation is the best way to inoculate.Secondly,four different infection doses were selected to inoculate groups A,B,C and D by intranasal inoculation for animal infection test.The inoculation titers were:10^-7.38TCID₅₀/mL,10^-6.38TCID₅₀/mL,10^-5.38TCID₅₀/mL,10^-4.38TCID₅₀/mL,and inoculation dose was 0.5ml/nostril.After 15 days of inoculation,the lowest infection dose was determined by observing clinical symptoms and histopathological changes,monitoring body temperature changes,and detecting detoxification.The results showed that the body temperature a group increased on the 6th day after inoculation with FHV-1,and all died on the 7th day,and the body temperature could not be observed.The body temperature increased on the 3rd day of the B group,and the body temperature reached 39.3?on the 5th day.After the second day,the body temperature increased,and the body temperature reached 39.2?on the 7th day;the body temperature of the D group fluctuated slightly.On the 2nd day after vaccination in group A,there were symptoms of sneezing serous secretions,sneezing and other symptoms.The symptoms were aggravated on the 3rd day.Three died on the 6th day and all died on the 7th day.The symptoms of eye-nose serous secretion,sneezing and snoring appeared on the 4th day after inoculation in group B,and the symptoms of eye-nose serous secretion turned to purulent secretion and dyspnea on the 6th day;the symptoms of eye-nose serous secretion and sneezing began to appear on the 5th day after inoculation in group C,aggravated on the 7th day,and the symptoms of eye-nose serous secretion turned to purulent secretion,dyspnea and other symptoms did not occur in group D.Symptoms of upper respiratory tract appeared.The experimental results indicated that only the dose of 10^-4.38TCID₅₀/mL could not cause the disease,and the other three doses could cause the death of the cat so the minimum dose was determined to be 10^-5.38TCID₅₀/mL.Finally,according to the optimal vaccination route and the lowest infectious dose determined in the previous experiment,the mice were inoculated by intranasal drip.The dose was 10^-5.38TCID₅₀/mL,and three repeated infection tests were performed and observed continuously for20 days.An animal infection model was established by observing clinical symptoms,histopathological changes,monitoring changes in body temperature,and detecting detoxification.The results showed that the body temperature began to rise on the 3rd day after inoculation and reached its peak on the 8th day,reaching 39.2?,and began to turn around on the 9th day.On the 4th day after inoculation,the symptoms of eye-nose serous secretion,sneezing and snoring appeared,and on the 8th day,the symptoms of eye-nose purulent secretion,conjunctivitis,dyspnea and skin ulcer around the eyes and nose increased significantly.On the 10th day,the two cats died.It was concluded that the inoculation dose of10^-5.38TCID₅₀/mL by nasal drip could cause morbidity and death in all cats.The FHV-1 pet cat infection model established in this experiment lays the foundation for the development of vaccine preparation and therapeutic drugs.