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3.  The Successful Management of Leptospirosa hardjo Infection in a Beef Herd in Northern Ontario 
The Canadian Veterinary Journal  1986;27(11):435-439.
Abortion, premature calving, hemolytic anemia and fatal hematuria were associated with high levels (titer > 10−4) of antibody to Leptospira interrogans serovar hardjo and with isolation of hardjo in a herd of 265 beef cattle in the Great Clay Belt of northern Ontario. This herd was bred by artificial insemination, after heat detection by vasectomized bulls. The antibody prevalence rate in the herd was 54 to 60% over a five year period. The rate tended to reach 100% by age three years and to be below 5% in yearlings, which were raised in isolation from older cattle. Hardjo was isolated from the urine of a cow that aborted in the eighth month of pregnancy, and from kidneys of yearling steers which had been exposed to an older cow. Maternal antibody levels in calves paralleled those in their dams, protecting calves while they were being naturally exposed to infection, thus contributing to the achievement of balance between host and parasite. A controlled vaccination trial was conducted in 50 initially seronegative yearling steers and heifers. Serological response to vaccine was limited to a maximum agglutinin titer of 10−2 in 8% of vaccinated cattle. Vaccination reduced the infection rate from 86% in the controls to 46% in the treated group, indirectly reducing the number of calves for which colostral antibody against hardjo would be available. A vaccination program was not implemented in the herd. Hardjo infection appeared to die out over a period of six years following the initial five year study period, with antibody prevalence falling from 60% to 0.7% and reactors persisting only in two eight year old cows. Decline in infection was coincident with changes in management which protected heifers from exposure to infection until their third pregnancy, and which probably lowered the reservoir of infection by increased culling from older age classes.
PMCID: PMC1680323  PMID: 17422716
Hardjo; clay; maternal antibody; vaccination; bovine leptospirosis
4.  Leptospirosa pomona Abortion Storm in a Cattle Herd in Saskatchewan 
The Canadian Veterinary Journal  1986;27(11):440-442.
Abortions occurred in 18% of 131 beef cows and heifers during two months, on a farm in southern Saskatchewan. The losses began two weeks after acute febrile illness and agalactia in a dairy cow to which the beef herd had been exposed. A diagnosis of Leptospira interrogans serovar pomona infection was made on the basis of serology in cows and the finding of leptospires in fetal tissues by fluorescent antibody test. Tentative diagnosis of infectious bovine rhinotracheitis delayed treatment and prophylaxis until infection attained high intensity in the herd and severe losses to the farmer occurred. Abortions ceased after vaccination against pomona and oxytetracycline treatment of pregnant cows, although chronic debility followed the acute phase of the disease in some cows. Recrudescence of infection was suspected four months later, when acute agalactia occurred in one cow and debility in calves and cows was recurring. Pomona infection was not proven, but dihydrostreptomycin treatment and revaccination were applied to the whole herd. Seroconversion and IgM antibody continued to indicate a persistent source of infection and susceptibility in a minority of the population one year after onset. The source of the original infection is believed to have been a carrier beef cow, or a dairy cow which was leptospiruric at the time of contact with the beef herd. With the exception of one aborted calf, no evidence of pomona infection was found outside the farm, in cattle or wild mammals tested serologically within a radius of 30 km, during one year following the outbreak.
PMCID: PMC1680310  PMID: 17422717
Abortion; bovine; pomona; leptospirosis
5.  Leptospira interrogans serovar hardjo Infection in Cattle in the South Okanagan District of British Columbia 
The Canadian Veterinary Journal  1985;26(10):328-332.
An outbreak of leptospirosis due to Leptospira interrogans serovar hardjo in the South Okanagan District of British Columbia was investigated. The infection was associated primarily with bulls, but serovar hardjo was isolated from both bulls and cows at slaughter. Kidney and cerebrospinal fluid were found to contain leptospires, independently of the presence and level of serum agglutinins. Treatment of a bull twice in six months with dihydrostreptomycin failed to diminish an agglutinin titer (1/200) which persisted for two years without reexposure of the bull. A serological survey of cull cows sold through a central auction mart revealed the presence of hardjo agglutinins in 15.4% of 1300 sera representing 163 herds in 20 locations. Thirty percent of these herds contained reactor cattle. The number of premises from which reactor cattle came in a given locality varied from 4% to 67.7%. Measures to control leptospirosis in the study are suggested.
PMCID: PMC1680177  PMID: 17422584
Leptospirosis; infertility; hardjo; kidney; cerebrospinal fluid; Canada; British Columbia
6.  Correlation of Bedrock Type with the Geography of Leptospirosis 
Leptospirosis occurs enzootically over most of Southern Ontario. Leptospira pomona is the serotype most commonly found in outbreaks. Antibodies to L. pomona occur frequently in the sera of deer in wilderness areas. The geographic location of leptospirosis presents a pattern which closely parallels the distribution of Paleozoic bedrock. By contrast, L. pomona infection is absent from areas underlain by Precambrian bedrock. Comparisons of water chemistry, soil type, habitat, and host and pathogen availability in these two geologically distinct environments have not defined the mechanisms involved in the disease pattern. Leptospires resembling saphophytic strains occur widely, regardless of bedrock type. High titers to L. biflexa, a saprophytic serotype, were found frequently in deer sera from a Precambrian area which was surveyed intensively. Antibodies to L. hardjo and L. sejroe occur in many bovine sera from a predominantly Precambrian area where Paleozoic outliers are numerous. Colloidal clay is common to leptospiral habitats. A microenvironment structured by the surface activity of clay is likely to be a key ecological factor in the landscape epizootiology of leptospirosis. In Ontario, bedrock composed of limestone and dolomite formed in the Paleozoic era appears to be a reliable ecological marker for Leptospira pomona infection.
PMCID: PMC1319417  PMID: 4246001

Results 1-6 (6)