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Leptospirosis - Coggle Diagram
Leptospirosis
clinical presentation
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abortion may occur 3-12 weeks following infection with most abortions during the last 3 months of pregnancy
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Leptospira Hardjo may also cause embryonic death. Venereal transmission is possible but may not adversely affect the pregnancy rate because Leptospira Hardjo is killed by uterine defences during oestrus. Split-herd vaccination trials have shown improved fertility parameters in vaccinated cows in herds with endemic Leptospira Hardjo infection.
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aeitology
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leptospires are susceptible to drying, exposure to sunlight, pH under 5.8 or extremes of temperature
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diagnosis
milk drop diagnosis
In acute infection paired serum samples taken three to four weeks apart will normally demonstrate increased MAT or ELISA concentrations. Leptospires can be demonstrated in urine samples using dark-field microscopy.
abortion diagnosis
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Dam serology is of limited use because the MAT titre may fall rapidly after acute infection and be negative at the time of abortion; a positive result may only reflect previous exposure. During an abortion outbreak MAT titres >1/400 in some aborted cows are likely to be meaningful. ELISA titres are reported to remain positive for much longer following infection so may simply indicate previous exposure.
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Antibodies in foetal fluids may indicate exposure to Leptospira Hardjo in utero after four months' gestation however the foetus may die before mounting an immune response.
Fluorescent antibody test (FAT) to detect Leptospira Hardjo antigen in foetal tissues, e.g. kidney and lung is the best available test to confirm a diagnosis of abortion but delays in sample submission lead to rapid sample autolysis adversely affecting the test.
herd screening test
A bulk milk ELISA test is available and can be monitored regularly as part of surveillance programme in a naïve herd. Pooling milk samples from first lactation heifers is a useful way of monitoring the infection status in a herd.
treatment
antibiotic treatment of milk drop cases recommended to reduce excretion of leptospires and zoonotic risk
A single intramuscular injection of streptomycin/ dihydrostrepomycin at 25mg/kg will eliminate infection from most cattle. However, vaccination is the better approach avoiding unnecessary use of antibiotics.
control
As a precautionary measure streptomycin is added to semen from bulls held at artificial insemination centres.
Vaccination should prevent urine shedding following exposure and will protect against milk drop and abortion.