Urinary tract disease, weight loss and death possibly related to winter browsing of a shrubby plant (Cistus salviifolius) in three herds of Portuguese beef cattle

Four outbreaks of fatal urinary tract disease in beef cattle were studied on 3 farms in Southern Portugal between 1998 and 2000. The Portuguese Mertolenga breed appeared to be at increased risk. 93% of deaths occurred in animals aged 4 years or older. No cases were observed in animals less than one year of age. Outbreaks of disease, which developed from January through May, were associated with inadequate pasture growth during December through February, a result of either unseasonal cool, rainy and overcast, or dry winter weather. Circumstantial evidence suggested that the disease was related to browsing a bushy, non-deciduous, perennial range plant, Cistus salviifolius (sage leaf rock rose), during periods of nutritional deprivation. Dysuria was observed in nearly all affected animals. On rectal and necropsy examinations, the urinary bladder was greatly distended. The bladder wall was thickened and oedematous in 44% of cases necropsied. In the early stages of disease, a variable proportion of affected cattle showed signs of photophobia, and a few eventually became blind and had severe bilateral keratitis and complete corneal opacity. Chronic cases lost considerable weight. Survivors recovered slowly, taking 4 to 12 months or even longer. The course of fatal disease ranged from less than 2 weeks to more than 5 months. The combined mean morbidity, mortality, and case fatality rates for all outbreaks (in straightbred Mertolenga herds) were 26, 11, and 43%, respectively.