The Epidemiology of Summer Mastitis in the Netherlands

Abstract

Summer mastitis is an acute mastitis which is only seen in the summer months in pastured, non-lactating cattle, i.e., dry cows, heifers and calves. The clinical signs and isolated bacteria are typical and must be seperated from other mastitis cases in dry cattle in summer or winter time. The disease is enzootic in certain areas in the Netherlands but only sporadic in others. Soil and vegetation (trees and bushes) are important but summer mastitis is also seen in quite open areas without trees and bushes. The role of H. irritans in the etiology seems to be important. The incidence of summer mastitis varies between years and has, for the last 3 years, been as low as 0.2%. This is probably the reason that over 50% of the acute mastitis cases in dry cattle could not be confirmed bacteriologically as summer mastitis in 1984 and 1985. In 1980 the incidence on the same farms was as high as 10%. Calves contract less summer mastitis than heifers. The highest incidence rate is seen in dry cows which also have the most serious clinical symptoms. Pregnancy seems to have no influence. Cows still with a high milk yield at drying off are more susceptible to summer mastitis. If there is a calf, heifer or cow which sucks other cattle the incidence of summer mastitis rises dramatically in a herd. There is no difference in susceptibility between the various breeds in the Netherlands but the Jersey which is said to be rather insusceptible is hardly seen in Holland. There are, however, heritable differences. Daughters of bulls with a high peak milk flow are more susceptible, as are daughters of easy milking cows. This is probably the reason why heifers from certain farms contract more summer mastitis than heifers from other farms at the same time in the same pasture. Front quarters are twice as much affected as hind quarters with summer mastitis. Front and hind quarters are equally affected in acute mastitis in dry cattle during the summer which is caused by other bacteria than those typical for summer mastitis. Front and hind quarters are equally affected in acute mastitis in dry cattle during the summer which is caused by the other bacteria than those typical for summer mastitis.