| Aleutian mink disease (AMD), which was caused by Aleutian mink disease parvovirus (AMDV), can trigger a chronic disorder of the immune system with the characteristics of plasmacytosis and persistent infection. It is notably common in mink breeding countries and causes reduced litter sizes, abortions, stillbirths, fur damage, glomerulonephritis, arterial inflammation and hepatitis. Besides, it can also give rise to immune system disorders in adult minks, and a serious pneumonia in newborn minks. Renal enlargement profile, congestion, variable beige or brown and some surface punctate hemorrhage and gray necrosis can be detected using pathology analysis. AMD with a high morbidity and mortality, always causes low fur quality and huge economic losses in mink farming industry.In recent years, strongly international demands of fur market in China contributed to the expansion of the mink farming industry. However, AMDV infection rates remain a high level mainly because of the poor management. In order to accurately evaluate the recent popularity of AMD in China, thousands of kidney samples of minks were collected from9mink farms across Hei longjiang, Ji lin, Liao ning, Shan dong provinces during2009-2010.18654serum samples of minks were collected from three independent mink farms during2009-2010. The AMDV infections in these minks were investigated by detecting these samples with the methods of PCR and CIEP separately. Results showed that the positive rates were94.59%and68.67%, suggesting that AMDV infections in our country were still keep a high level.In order to provide more conveniences for the future researches of AMDV antigen in China, and studied the genetic evolution type of Aleutian mink disease parvovirus. The samples collected from minks which were suspected of being infected with the AMDV were amplified using PCR method for a primary diagnosis, and were extracted and serially passaged in Crandel Feline Kidney cells (CRFK). If a PCR amplification indicates a positive result, the VP2gene sequences before and after separation will be sequenced. The results were compared with others AMDV VP2gene sequences available in the GenBank and proved that we got a stain of AMDV which could stable growth in CRFK cells (named AMDV-ZYL1). Amino acid sequence analysis found the VP2protein sequence of the AMDV-ZYL1strain have a highest homology96.1%with USA highly pathogenic AMDV-Utah-1strain while only have a homology of92.7%when compared with ADV-Far East,what confirms the VP2protein of ADV-ZYL1with a high mutation rate.For research China’s AMDV VP2sequence of molecular epidemiology,we selection nine representative samples from four districts and get sequences of AMDV strains VP2were compared with10international popular AMDV strains download from GenBank for research.105amino acid mutations were found among the647amino acid residues of the VP2protein from the19strains,27a.a were only found in Chinese.These mutation sites were not only found in the hypervariable region,but also happened in the immunoreactive region (VP2:429-524). These mutations also contain the sites decided to AMDV host range, immune pathogenesis and the infection stability function sites. In addition, we found that two Chinese strains ADV-SD1and ADV-DL1, lacked an amino acid residue at position235of the hypervariable region, which resulted from the deletion of three nucleotides in the VP2gene. The impact of this amino acid deletion should be thoroughly elucidated.The phylogenetic analysis was performed using the MEGA4.0software. The results indicating that several genotypes of the virus may circulate on a farm simultaneously and no correlation between the period and area of isolation.The results of the phylogenetic analysis clearly demonstrate that there are five subtypes that form independent clades. based on the phylogenetic analysis, we found that nearly50%of Chinese AMDV isolates were classified into Groups C and D, and these two groups had no relationship with AMDV strains from other counties.The remaining Chinese isolates were genetically similar to various AMDV strains from other countries. These results show that in addition to the AMDV strains imported from other countries, certain local AMDV strains are also prevalent in China. These strains could have evolved from an endemic virus species that had circulated among Chinese farmed minks for a long time or from AMDV strains imported from other countries in the past through the international mink trade. On one hand at present AMDV in our country were popular trend of complex, China and abroad stains exists at the same time, which caused inconvenience to AMDV purification in minks breeding industry. On the other hand, nucleotide or amino acid mutation rate of AMDV were very high,the use of import antigen detection AMD could affect the detection sensitivity and specificity, weaken the AMD purification effect,and the phylogenetic show that most of domestic AMDV strain fall in the same or similar evolutionary tree, has the certain evolution regularity and common the evolutionary tendency, and provides theory basis for make the standard CIEP diagnosis antigen apply to our country... |
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