These species specific microscopic mites cause unbearable itchiness for the animal and can result in thinning and/or patchy loss of hair and scurfing of the skin (may resemble dandruff). Severe infestations can be life threatening. The most serious infestations occur in the young and ill older animals subject to stress and poor environmental conditions. The response in healthy animals, perhaps due to grooming or suppressed immune response is less severe. "Maximal parasite load is reached approximately 1 month after infection (Rothwell et al., 1991) then slowly regresses if left untreated. Mortality is common in some reports." (Harkness and Wagner)