Development of new tools for veterinary practice in relation to cystitis and urolithiasis in mink - optimization of prevention and treatment

PhD Student: Karin Mundbjerg
Thesis defended: 9 July 2021


Mink urinary tract disease (MUTD) is a disease complex characterized by stones in the urinary tract and infection in of the urinary bladder and kidneys. The disease often leads to fatal urethral obstruction, especially in males and is a common cause of mortality in growing mink kits. Urinary tract stones in mink are reported to be composed of the mineral struvite which forms in alkaline urine. The bacteria Staphylococcus delphini group A has been found in mink with urinary bladder lesions. The causal relationship between struvite formation and urinary bladder infection in mink is unknown. In dogs and humans urinary tract infection cause struvite stone formation, while in cats and ferrets the struvite stones develop in sterile urine. Identifying disease mechanisms and important disease risk factors can be used to prevent disease occurrence. Dietary factors as feed composition, feeding frequently and feed intake has been related to urine pH and struvite formation in other animals. Also gender and specific age groups has been found associated with occurrence of struvite stones, urinary tract infection, and urethral obstruction. Other diseases in mink are found related to specific fur coat color types and familial risk of urinary tract disease is known from humans.

In production animals management factors can affect disease occurrence. The effect of the current preventive and therapeutic treatments of MUTD in mink kits has not been investigated. Improved understanding of MUTD can improve prevention and treatment of the disease in mink kits.

Purpose of the project

The purpose of this PhD project was to generate tools for veterinarians in mink practice by elucidating questions concerning MUTD in order to improve disease prevention and treatment.

Results so far

Mink urinary tract disease (MUTD) in mink kits was found to be associated with the bacteria S. delphini group A and struvite was the main urinary stone mineral. MUTD caused one third of all mortalities in mink kits during July and throughout the growth season. Male kits and mink of the color type black was found to be in higher risk of fatal disease. MUTD was related to higher body weight and BMI compared to other causes of mortality. High mink kit body weight at the age of 28 days and low kit weight gain were associated with MUTD.

The investigation provided evidence of familial aggregation of MUTD within some families of mink. Mink kits of parents having siblings with MUTD were in higher risk of dying from MUTD than mink kits which parents did not have siblings diagnosed with MUTD.

Feed supplement with 3 ‰ ammonium chloride lowered urine pH of mink kits after feeding. A daily five-hour break between feedings did not affect urine pH after feeding or fasting compared to ad libitum feeding. Neither ammonium chloride additive nor the daily break between feedings lowered mortality caused by MUTD compared to controls. Antimicrobial flock treatment with amoxicillin (7.5 mg/kg and 14 mg/kg) or sulphadiazine/trimethoprim (30 mg/kg) did not lower mortality caused by MUTD in mink kits compared to controls.

Potential farm management risk factors of MUTD were high daily feed intake in late gestation, low daily feed intake in late lactation, low number of daily feedings in June, use of short kit nets, and cleaning manure from the cage.

Future perspectives

Further investigation of preventive and therapeutic treatment of mink urinary tract disease must be conducted. Protocols for dissolution and prevention of struvite stones and disease risk factors should be investigated. With implementation of individual animal registrations as cause of mortality, feed and water intake, body weight, color type and treatments combined with registration of management procedures (weaning, frequency of feeding and cleaning procedures) more refined analysis of animal and management risk factors could be performed.

The study designs used in this project may be applied in future investigations of other diseases leading to mortality in mink. Registering disease on animal level would also enable the investigation of diseases not leading to mortality. Best management practice and treatment guidelines could be established by identifying possible risk factors and testing preventive and therapeutic treatments using similar protocols.

The COVID-19 pandemic which forced Danish mink breeding to pause production and consequently the biggest contributor to Danish mink research, Kopenhagen Fur, is planned to close in 2023. This development raise great concern for the future of research in mink disease and welfare.