Investigation Of HyPerthemia Causes Of Canine Parvovirus Disease

Objective: Canine parvovirus infection is a highly contagious disease in canine,clinical treatment can reduce its mortality. But mortality was extremely high in which the tempreture is more than 41 ℃, even it was up to 100%. The aim of this study was performed to explore possible pathogenesis in canine hyperpyrexia models, hoping to provide experimental data for the clinical treatment of hyperpyrexia cases.Methods: Canine feces were collected from the canine which were infected with parvovirus of hyperpyrexia canine, and feces were diluted by PBS fluid to scale(1:5),then centrifuged and stored at 4℃. 10 healthy crossbreed canines(weight: 2-3kg, age:40~60 days),which were not immuned, kept in the same management and feeding conditions. One week later, each canine was given oral CPV challenge(2 ml/kg per day) for 3 days. Observed clinical symptoms of canine every day, detected temperature of all canines 2 times a day. When canine developed typical symptoms,we collected feces to test by the CPV test paper and detected parameters of blood 1week after infection, respectively. What’s more, content of endotoxin and Interferon-α(IFN-α) in serum was measured by ELISA method before diagnosis and after diagnosis. Furthermore, we Collected heart, liver, spleen, lung, and kidney of the dying or dead animal for bacterial culture to determine the strains of infected bacteria through isolation and purification of bacteria, oxidase test and biochemical test.Meanwhile, we used neutral formalin solution to stabilize the above organs and make pathological section by using HE method,finally, Observed the pathological change of organs.Results: The experimental results are as follow:1. Clinical manifestation of animals experiment :After 3 days of oral CPV challenge, the experiment canines started to appear obvious and typical clinical symptoms such as depression, vomiting, diarrhea, loss of appetite, mild or moderate dehydration, bloody stool, pale conjunctiva and so on.CPV test paper indicated Strong positive results, which confirmed the replication of the canine parvovirus case is completed.2. Changes of body temperature:After oral CPV challenge, there were 3 canines of hyperpyrexia(41℃ above), 5canines’ temperature were between 39 and 41℃. Incidence rate of hyperpyrexia was up to 30%. Following CPV challenge 2 and 3 days later, the temperature appeared significant increase(P<0.05), compared with ardent fever canine before diagnosis;on the 4 to 7 days, it showed remarkably significant increase(P < 0.01); the temperature of canines, which had a fever but not reached 41 ℃, also showed remarkably significant increase(P < 0.01) compared with that of 4 to 7 days;comparing the two group, on the second and the third day, it showed significant increase(P < 0.05), and on the sixth and the seventh day, it showed remarkably significant increase(P<0.01).3. Changes of blood-routine:Here, we compared the changes of blood-routine of canines of 39 ~41℃ and canines of above 41℃ with before diagnosis, respectively. the content of white blood cell and lymphocyte all first significantly increased and then significantly decreased during 3 to 7 days(P < 0.05 or P < 0.01); The number of red blood cell showed remarkably significant decrease(P<0.01), whereas the ratio of lymphocyte showed significant or remarkably significant increase(P<0.05 or P<0.01). The difference of all indicator of the two group was not significant.4. The content of endotoxin:The content of endotoxin of canines of 39~41℃ was 0.17±0.02(Eu/L) and the endotoxin from same canines after CPV challenge was 0.29±0.02(Eu/L), which was significantly higher than before diagnosis(P < 0.05). The endotoxin of canines of above 41℃was 0.16±0.06(Eu/L) after CPV challenge was 39±0.07(Eu/L), which showed remarkably significant increase than before diagnosis(P<0.01). Compared with canines of 39~41℃, the endotoxin of canines of above 41℃ showed significant increase(P<0.05).5. The content of of Interferon-ɑ:The contents of the Interferon-ɑ of ardent fever canines between 39~41℃ and above 41℃was 99.38 ± 6.26(ng/ml)) and 117.01 ± 51.77(ng/ml), respectively;compared with control group, the content of the Interferon-ɑ of canines between 39 and 41℃was 325.78 ± 118.05(ng/ml), which had significant increase(P < 0.01);compared with the canines before they were diagnosed, the content of the Interferon-ɑof the above 41℃ was 358.75±101.82(ng/ml), which showed remarkably significant increases(P < 0.01); Compared with canines of 39 ~ 41℃, the content of the Interferon-ɑ of the above 41℃ showed no significant change.6. Bacterial culture and identification results:Samples from livers of ardent fever canine appeared bacterial colony in the culture vessel. This kind of bacterial colony was pink in the Mac Conkey Agar Medium.Oxidase test indicated that this bacteria was gram-negative bacteria and identified as Escherichia coli by biochemical tests.7. Pathological observation of organs:The pathological section indicated that the livers of ardent fever canines had a large area of vacuolar fatty degeneration. other organs didn’t appear obvious pathological changes.Conclusion: When canine infected with canine parvovirus, they might develop secondary Escherichia coli infection, which could lead to endotoxemia and ardent fever. The content of endotoxin in the body was positively correlated with the change of body temperature. Whereas ardent fever was not correlated with the content of the interferon-α.