Is Sarcoptes scabiei infection in pigs a major welfare concern? A quantitative assessment of its effect in the host's nocturnal rubbing and lying behavior

The nocturnal rubbing and lying behaviorof commercialfattening pigs from moderately (M)and heavily (H) Sarcoptes scabieieinfected farms was investigated. The study included 4 cohorts (2 per farm) of 11-15 acaricide-treated (uninfected) and untreated (infected) 4- to 7-month-old pigs, and the time and number of behavioral bouts were monitored for 350 hours over 101 days. Auricular mites, dermatitis, and plasma histamine concentration were investigated postmortem at the age of 7 months, and histamine concentration was also analyzed at the age of 3 months in 3 cohorts. The percentage of pigs with mites was 27% and 79% in untreatedfarmMandHcohortsand0%intreatedpigs.Erythematoushypersensitivedermatitiswasobserved inbothtreated anduntreatedanimals;however,histamine levelsweremuchgreaterinuntreatedcompared with treated pigs and increased with time in the former group. Rubbing was significantly increased in untreated compared with treated pigs, but it was generally low and with small variations over time. The mean rubbingtimeper210minutes(1daysample)was0.00-0.79and0.00-0.65minutesinuntreatedpigsinfarms MandH,respectively,and0.00-0.15and0.00-0.03minutesintreatedpigsinfarmsMandH,respectively.The mean lying time and number of events of standing up were similar for treated and untreated pigs, and differencesbetweenfarmcohortswerenotassociatedtoS.scabieiinfection.Moreover,theaveragepig’slifelong weight gain also appeared to be independent of infection. The small effect of S. scabiei on pig behavior and growthcontrastswiththemuchgreatereffectthatthenonburrowingmitePsoroptesovishasbeenreportedto