Leptospirosis in Cattle (Redwater of calves)
Description Leptospirosis is recognized worldwide as a cause of abortion, systemic illness, and mastitis. Signs can be mild or severe. Several serovars of LEPTOSPIRA INTERROGANS can be involved. Dx by isolation or serology. Abortions occur while titers are decreasing and are usually in the last trimester. In rare cases there is peracute hemolysis with seizures and sudden death. Transmissible to man. Antibiotics and vaccination are used in treatment and prevention. Has been associated with the birth of weak calves.
Acute leptospirosis can be severe in calves. Serovar pomona results in the most severe disease, however other serovars can cause similar disease. Calves may have fever, anorexia, dyspnea from pulmonary congestion, icterus, hemoglobinuria, and hemolytic anemia. Body temperature may rise suddenly to 105-106°F (40.5-41°C). Hemoglobinuria rarely lasts longer than 48-72 hr. The anemia begins to improve by 4-5 days and returns to normal 7-10 days later. Serovar hardjo being a host-adapted strain, does not typically result in the acute syndrome. Morbidity and mortality are higher in calves than in adult cattle.
In older cattle, signs vary greatly and diagnosis is more difficult. Enzootic infections of naive cattle with serovar hardjo , which usually result in abnormal milk, are more obvious in dairy than in beef cattle. Signs usually are restricted to a sudden drop in milk production; a hemolytic crisis does not occur. The milk is thick, yellow, and blood-tinged, with thick clots and a high somatic cell count; milk production can drop 10-75%, depending on the infecting strain. The udder is typically soft and flabby, which is unique for leptospirosis. Milk production can return to normal in 10-14 days even in the absence of treatment; however, cows with a severe drop in production may not recover to full production during that lactation cycle.
The chronic forms of leptospirosis manifest as abortion and stillbirths, and occur with infections of serovars pomona and hardjo . Abortion generally occurs 6-12 wk after initial infection and is more common during the third trimester. Stillbirths and birth of premature or weak infected calves also occur. An abortion storm in a breeding herd is often the first indication of leptospirosis infection, because the mild initial signs often pass unnoticed. In endemically infected herds, abortions occur mostly in younger animals and are sporadic. Calves reared by previously infected cows are protected by colostral antibodies for up to 6 mo. The calves generally have an antibody titer similar to that of their dams. Infertility may also be a problem in endemically infected herds, possibly as a consequence of localization of infection in the uterus and oviducts.