Epidemiology, pathogenesis, and diagnosis of Aleutian disease caused by Aleutian mink disease virus: A literature review with a perspective of genomic breeding for disease control in American mink (Neogale vison)

A virulent escherichia coli O121-B2-ST131 strain causes hemorrhagic pneumonia in mink: evidence from pathogenicity and animal challenge experiments

In recent years, rapid fatal hemorrhagic pneumonia (HP) has been increasingly reported in mink. In several studies, the virulence factors of strains isolated from diseased tissues have been identified as extraintestinal pathogenic Escherichia coli (ExPEC). The molecular characteristics of the strains were also analyzed, but whether ExPEC is the etiological agent of HP has not been confirmed in an animal challenge model. In this study, we characterized the antibiotic resistance, virulence characteristics, and pathogenicity of a bacterial strain isolated from a typical case of mink HP, and designated it L1. Our study revealed that isolate L1 has high levels of antibiotic resistance, to multiple antibiotics, including ampicillin, tylosin, kanamycin, and so on. Numerous virulence genes were detected in isolate L1, including those encoding adhesins (focG, afa/draB, mat, crl), invasins (ibeA, einv), and toxin (cnf1). ExPEC isolate L1 belongs to the O121 serogroup and was classified in the B2 phylogroup and sequence type 131 (ST131). Animal experiments showed that L1 is highly pathogenic to mice, and induced fatal HP in mink. A mouse model of isolate L1 infection showed lethargy, depression, and then death. The sick minks showed similar clinical signs and died soon after nasal bleeding and hematemesis, with a large amount of congestion and consolidation in the lungs. Using animal challenge experiments based on Koch's postulates, we demonstrate for the first time that ExPEC is a causative agent of rapid fatal HP in minks. Our research provides important insights into the identification and control of rapid fatal HP in minks and effective antibiotic treatments for infected animals.

Multiplex one-step RT‒qPCR assays for simultaneous detection of AMDV, MEV and CDV

BACKGROUND

Aleutian mink disease, mink viral enteritis and canine distemper are known as the three most serious diseases that cause great economic loss in the mink industry. In clinical practice, aleutian mink disease virus (AMDV), mink enteritis virus (MEV) and canine distemper virus (CDV) are common mixed infections, and they have similar clinical clinical signs, such as diarrhoea. Therefore, a rapid and accurate differential diagnosis method for use on mink ranches is essential for the control of these three pathogens. Here, we developed multiplex one-step real-time quantitative PCR (RT‒qPCR) assays for the simultaneous detection and quantification of AMDV, MEV and CDV by using three primers and probes based on the conserved NS1, VP2 and N genes, respectively.

RESULTS

The results showed that the established method can not cross-react with other mink pathogens, with a detection sensitivity of 25 copies/µL and a coefficient of variation less than 3.51%. Moreover, the interference experiment showed that the presence of AMDV, MEV and CDV templates at different concentrations would not interfere with the detection results. Furthermore, two hundred clinical samples of mink with diarrhoea were simultaneously analysed using multiplex RT‒qPCR and single RT‒qPCR, the Kappa values were all greater than 0.921, indicating that there was a high degree of coincidence between the two detection methods.

CONCLUSIONS

In conclusion, multiplex RT‒qPCR exhibited high specificity, sensitivity, and reproducibility, indicating that this method can be used as a reliable and specific tool for the differential detection and quantification of AMDV, MEV and CDV.

A developed TaqMan probe-based qPCR was used to quantify the distribution of AMDV in various tissues of infected mink and its prevalence in northern China

Aleutian mink disease (mink plasmacytosis) is a severe immune complex-mediated condition caused by the Aleutian Mink Disease Virus (AMDV), the most significant pathogen affecting mink health in the industry. Several studies have shown that AMDV epidemics can result in millions to tens of millions of dollars in economic losses worldwide each year. In this study, we developed a TaqMan probe-based real-time PCR technology (TaqMan-qPCR) for the specific, sensitive, and reproducible detection and quantification of AMDV in mink tissues by the VP2 gene, achieving detection limits as low as 1.69 × 101 copies/uL of plasmid DNA and 8.50 × 10-3 ng/uL of viral DNA, and the established TaqMan-qPCR assay is 100 times more sensitive than PCR. Clinical samples of mink from different provinces showed a high prevalence of AMDV infection, 89.55% in Heilongjiang, 90.74% in Shandong, 80.23% in Hebei, 83.70% in Jilin, and 82.35% in Liaoning Province. Tissue distribution analysis showed that viral loads were generally high in all organs, especially in the mesenteric lymph nodes and spleen, and the virus was also detected in non-lymphoid tissues such as the brain, confirming the widespread distribution of AMDV throughout the body of mink. The established TaqMan-qPCR assay will become an important diagnostic tool for the prevention and control of AMDV, which is essential for disease management in mink populations.

Aleutian disease: Risk factors and ImmunAD strategy for genetic improvement of tolerance in American mink (Neogale vison)

Aleutian disease (AD) is a devastating infectious disease in American mink (Neogale vison) industry caused by Aleutian mink disease virus (AMDV). Two crucial steps toward controlling infectious diseases in farm animals are: (i) assessment of the infection risk factors to minimize the likelihood of infection and (ii) selection of animals with superior immune responses against pathogens to build tolerant farms. This study aimed to investigate AD risk factors and evaluate a novel "ImmunAD" approach for genetic improvement of AD tolerance. Phenotypic records and pedigree information of 1,366 and 24,633 animals were included in this study. The risk of animal's age, sex, color type, and year of sampling on AMDV infection was assessed using a logistic regression model and counter immune-electrophoresis (CIEP) test results. ImmunAD phenotype was calculated based on AMDVG enzyme-linked immunosorbent assay (ELISA) and CIEP test results, and breeding values for ImmunAD were estimated using an animal model. Animals were classified into high-coordinated (HCIR), average-coordinated (ACIR), and low-coordinated immune responders (LCIR) using ImmunAD's breeding values, and the impact of selection of HCIR on live grade of pelt quality (PQ), harvest weight (HW), and harvest length (HL) breeding values were evaluated. Age of > 1 year, male sex, and year of sampling were identified as significant risk factors of AD (p < 0.05). A moderate-to-high heritability (0.55±0.07) was estimated for ImmunAD, while a higher heritability was observed among the CIEP-positive animals (0.76±0.06). Significantly higher breeding values were observed for PQ and HL among HCIR than those for LCIR and ACIR (p < 0.05). Our findings indicate the critical role of male breeders in AD distribution within mink farms. Regular screening of AD in male breeders before pairing them with females during breeding seasons can help disease control. ImmunAD strategy can be applied to genetic improvement of AD tolerance, with favorable impacts on some growth and production traits. Higher genetic gains can be achieved in populations with higher AD seroprevalences.