Abortion episodes in cattle were investigated on 54
dairy farms in Cumbria, North Lancashire, and North
Yorkshire from 1984 to 1986. From a breeding" population of
approximately 3600 dairy cows 149 abortions were
investigated, representing an annual abortion rate of 2%,
substantially higher than previously reported national
estimates.Visits were made by a Local Veterinary Inspector of the
Ministry of Agriculture, Fisheries, and Food to each farm
reporting an abortion, under the Brucellosis Order (England
and Wales) 1978. The required samples were submitted to a
Veterinary Investigation Centre (V.I.C), accompanied by form
BS7. In addition, further samples were taken from each case
where possible; placentome, fetal placenta, clotted blood
(followed by a convalescent sample 28 days later), and
fetus. All were examined in the practice laboratory.Routine bacteriology was carried out on fetal stomach
contents, lung, and placentome/placenta; cultured bacteria
were identified. Fetal thoracic fluid and paired serum
samples were sent to a V.I.C. for serological examination
against Bovine Viral Diarrhoea virus (B.V.D), Infectious
Bovine Rhino-tracheitis virus (I.B.R), and Leptospira hard.jo
infections.Pathological studies were made on all fetal and
placental material collected. Gross lesions were noted.
Eyelid, heart, lungs, liver, and placental tissues were
routinely fixed in 10% formalin, sectioned, stained with
Haematoxylin and Eosin, and examined.Autolysis was present in 81 of 118 fetuses examined.
Gross lesions were seen in 96 fetuses and 66 placental
tissues. Except for hepatomegaly (3 cases), they were not
considered to be diagnostically significance. Seven fetuses
were mummified.Immunoglobulins IgG and IgM were found in 35/129
fetuses, as well as titres to B.V.D (13/35), and L. hard.jo
(5/35). Positive titres to B.V.D, I.B.R, and L. hard.jo were
present in paired serum from 62 cows.Histological lesions were demonstrated in tissue from
113 abortions; infection was associated with 57 episodes. In
9 cases which remained undiagnosed, consistent lesions of
conjunctival hyperplasia with a coexisting placentitis (6/9)
and amnionitis (2/9) were recorded, resembling experimental
fetal infection with Ureaplasma diversum.Myocarditis was associated with B.V.D (6 cases) and
I.B.R (5 cases), which often coexisted with interstitial
pneumonia (13 cases). Bronchial pneumonia occurred in 24
fetuses, associated with isolation of pure bacterial
cultures from the lung. Erythroblastosis featured in 8
abortuses where L.hardjo infection was present.Placentome was a diagnostically significant tissue;
18/40 presented a necrotic placentitis. Haemorrhagic lesions
were found in 20, frequently linked to L.hardjo infection,
but accompanied by hypoxic change
