Epidemiological Characteristics And Immunology Research Of New Type Piglet Diarrhea

As one of the most common diseases in swine industry, piglet diarrhea outbreak nationwidely in China since 2010 and it caused serious loss. Piglet diarrhea occurred in large-scale pig farms, samll-sacle farms and backyark ones. As it unlike traditional diarrhea, this piglet diarrhea was called new type piglet diarrhea. This paper explored its epidemiological characteristics and PEDV posite rate. And pathological changes of the diarrhea piglets’ heart, liver,kidneys, spleen and intestine were studied. To explore immunology features of new type piglet diarrhea, antibodies of classical swine fever(CSFV) and porcine circovirus-2(PCV-2), levels of cytokines IL-1, IL-2, IFN-γ and secretory Ig A(SIg A) were determined. Besides, treatment of new type piglet diarrhea with IFN-γ was explored in this paper:1. Epidemiological survey of new type piglet diarrheaThe main characteristics of new type piglet diarrhea were vomiting, diarrhea and dehydration. Pigs wihin 7 days were susceptible. Mortality rate reach up to 70%-100%. Large-scale and medium-scale farms have higher incidence. Its duration reach up to several months and popular time concentrated in December every year to next April. But during the remaining time it also occurred. Test results found that positive samples were 100 parts in 159 fecal samples of suspected diarrhea in pigles. So the positive rate was 62.5%. This indicated that PEDV was the main pathogens which lead to the occurrence of new type piglet diarrhea.2. Histopathological changes of new type piglet diarrheaThe heart, liver, kidneys, spleen, and intestine of new type piglet diarrhea were collected for preparation of paraffin sections. Results showed that intercellular space between cardiac myocytes were widen and myocardial fiber were broken; Congestion and local necrosis in the liver, lobular architecture was not obvious, cable structure disappeared, nuclei was concentrated and dissolved, broken nuclei showed blue-violet stained debris, congestion in liver tissue, centra vein dilation which is full of red blood cells, hepatic cord and veins full of red blood cells, hepatic cord with a small amount of hemosiderin deposition; tubular epithelial cell swelling, tubular structural damage, tubular lumen with serous and a small amount of cells, renal tubular endothelial cells were observed in the oil pipe, congestion in kidney tissue; splenic structure reduce and was not obvious, thinning of splenic artery peripheral lymphoid sheath, small intestine villus shedding. The results indicated the presence of various organs dysfunction, the body’s blood circulation disorders and immune suppression.3. Immunology research of new type piglet diarrheaCompared with healthy control piglets, CSFV antibody level was lower and differences between the two groups was significant(P<0.01). PCV-2 antibody level of diarrhea piglets was lower than heathy piglets and differences between the two groups was significant(P<0.01). IL-2 and IFN-γ levels of diarrhea piglets were lower than heathy piglets(P<0.05); IL-1 levels between two groups didn’t show significant difference(P﹥0.05). SIg A levels of new type diarrhea piglets feces was lower than heathy control piglets(P<0.01). The rusults showed that sick piglets body contain immune suppression. The function of diarrhea piglets’ humoral immunity, cellular immunity and intestinal mucosa immunity were decreased. And afer interferon theraty, piglets’ IL-2 and IFN-γ levels increased significantly as high as the heathy piglets. This indicated that interferon could regulate the body immune status and relieve the illness of new type piglet diarrhea effectively.