Leptospirosis is a bacterial infection that can hit a herd in two ways: a sudden crash in milk, or a slow drain of lost pregnancies that is easy to miss. On many farms the first thing anyone notices is an abortion, not a sick cow.1The Bovine Proceedings. Bovine Leptospirosis and Infertility The same bacteria live on in the kidneys of cattle that look perfectly healthy and pass out in their urine, which is why the disease spreads and why farm workers can catch it too. It is very controllable, though, with a yearly vaccine and a single antibiotic treatment that clears carriers.
What Leptospirosis Looks Like in a Herd
In a cow meeting the infection for the first time, milk yield drops suddenly, two to seven days after infection.2NADIS. Leptospirosis The udder goes soft in all four quarters, with thick, colostrum-like secretions or blood-tinged milk.3NADIS. Leptospirosis Some cows also become dull and stiff, run a temperature and go off their feed.4NADIS. Leptospirosis In many cows, though, the signs are mild and pass unnoticed.5NADIS. Leptospirosis
Ordinary mastitis usually affects one quarter, which feels hard, hot and swollen, while the lepto milk drop (often called flabby bag) hits all four quarters and the udder feels soft. Several cows often drop milk around the same time, which points to a herd infection rather than a single bad quarter. If standard mastitis treatment doesn’t explain a group problem, ask your vet to consider lepto.
A herd can be infected without any obvious illness. Cattle that have met the infection before, or that carry the cattle-adapted strain, often show little. A mild fever or a day off feed is easily missed in a busy herd, so a lack of sick cows doesn’t rule lepto out if fertility is poor.
Calves show a different, more dramatic illness. They tend to get fever, depression and sudden anaemia.6The Cattle Site. Leptospirosis in dairy cattle They may have small blood spots on the gums and pass red urine, known as redwater.7The Cattle Site. Leptospirosis in dairy cattle
Red urine isn’t proof of lepto, because redwater also occurs with tick-borne disease and plant poisoning. A calf with red urine and pale gums needs a vet promptly, since anaemia can kill quickly.
Abortions, Stillbirths and Poor Fertility
Long-running infection is linked mainly to abortion, stillbirth and infertility, especially with the strain called Hardjo.8Merck Veterinary Manual. Abortion in Cattle – Reproductive System It also causes early pregnancy loss and weak calves.9The Bovine Proceedings. Bovine Leptospirosis and Infertility These losses are actually less common than silent infection, even though abortion is the most visible sign.10PubMed Central. Bovine Genital Leptospirosis: An Update of This Important Reproductive Disease
Abortions are often said to happen in the last third of pregnancy, but calves can be lost at any stage.11PubMed Central. Bovine Genital Leptospirosis: An Update of This Important Reproductive Disease Losses can follow infection by anywhere from 10 days to 6 weeks.12The Bovine Proceedings. Bovine Leptospirosis and Infertility So by the time a cow aborts, the infection that caused it may have passed weeks ago. A burst of abortions tends to suggest a strain picked up from other animals, while a steady trickle tends to suggest the cattle-adapted strain, though only testing can say which.13PubMed Central. Bovine Genital Leptospirosis: An Update of This Important Reproductive Disease
Early losses are the ones you never see. Cows that were confirmed in calf and later scan empty may have lost an early pregnancy. Repeat returns to service and stretched calving intervals can be the only clue, so keep scanning and service records and let your vet look for a pattern.
On the day a cow aborts, isolate her from the rest of the herd. Wear gloves and keep bare hands off the fetus and afterbirth. Keep both cool, call your vet so they can be tested, and make sure dogs and other stock can’t reach the material.
Even a single abortion deserves a question. Other infections also cause abortion, and the cause is rarely obvious from the cow alone, so ask your vet to test.
How Leptospirosis Spreads Between Animals
Some strains, chiefly Hardjo, are adapted to cattle and pass from cow to cow worldwide.14Merck Veterinary Manual. Leptospirosis in Ruminants – Infectious Diseases Other strains, such as Pomona and Grippotyphosa, are picked up from wildlife or other livestock, and their spread depends more on poor management and the environment.15Merck Veterinary Manual. Leptospirosis in Ruminants – Infectious Diseases In the United States, Hardjo causes most breeding losses, with Pomona next.16The AABP Proceedings. Leptospirosis in Cattle
The bacteria usually enter through broken skin or the moist linings of the eyes, mouth and nose.17Beef Cattle Handbook. Leptospirosis of Cattle They multiply in the liver and travel in the blood to the kidneys.18Beef Cattle Handbook. Leptospirosis of Cattle After the cow recovers, they settle in the kidneys and pass out in her urine, which makes her a carrier.19Beef Cattle Handbook. Leptospirosis of Cattle The kidney infection persists even though her immune system is fighting it.20PubMed. Host-pathogen interactions in the kidney during chronic leptospirosis
Carrier cows shed for a long time. Naturally infected cows can shed bacteria in urine for 28 to 40 weeks, longer than in experimental infection.21PubMed. Duration of urinary excretion of leptospires by cattle naturally or experimentally infected with Leptospira interrogans serovar hardjo Shedding is heaviest for the first few weeks, then gradually declines.22PubMed. Duration of urinary excretion of leptospires by cattle naturally or experimentally infected with Leptospira interrogans serovar hardjo In other herds, shedding came and went over periods of about 79 to 259 days.23PubMed Central. Urine shedding patterns of pathogenic Leptospira spp. in dairy cows So a cow that tests clear once may still shed later. Less often, bacteria also pass in semen, uterine discharges and milk, during breeding and from cow to unborn calf.24The Ohio State University. Leptospirosis in Cattle: Symptoms, Transmission, and Control
Rats carry the bacteria for long periods without getting sick and shed them in their urine.25PubMed Central. Leptospirosis in rats and livestock in Bantul and Gunungkidul district, Yogyakarta, Indonesia The bacteria can survive a long time in water, even water low in nutrients, and stay infectious.26PubMed Central. Leptospirosis and the Environment: A Review and Future Directions Flooding and heavy rain are linked to outbreaks around the world, and more frequent floods may bring more.27Transactions of the Royal Society of Tropical Medicine and Hygiene. Climate change, flooding, urbanisation and leptospirosis: fuelling the fire?
On a farm, infection is most likely to pass where urine collects. Muddy yards, wet bedding and shared troughs keep bacteria alive. Streams and ponds can carry them in from neighbouring farms or wildlife, and feed stores that attract rats bring rat urine close to cattle. Bought-in cattle and hired bulls can carry the infection into a clean herd. With months of shedding, one bought-in carrier cow can infect many others over a season, so control targets carriers, not just sick animals.
How Vets Confirm Leptospirosis
The most common blood test measures antibodies against several strains.28PubMed Central. Serological diagnosis of Leptospirosis in bovine serum samples using a microsphere immunoassay It depends on skilled reading, and low results can be false positives.29PubMed Central. Serological diagnosis of Leptospirosis in bovine serum samples using a microsphere immunoassay In one comparison, about 1 in 6 samples with low readings on this test came up negative on a newer, more sensitive method.30PubMed Central. Serological diagnosis of Leptospirosis in bovine serum samples using a microsphere immunoassay A single low result is therefore weak evidence, while a rising result or a pattern across the herd means more.
Other tests look for the bacteria directly. A DNA test on aborted calves found infection in about a third of fetuses, around three times as many as an older stain test.31PubMed. Improvement of Leptospira spp. diagnosis in aborted bovine fetuses by qPCR On urine from known infected cattle, the DNA test agreed well with growing the bacteria in culture but poorly with the stain test.32PubMed Central. Comparison of Real-Time PCR, Bacteriologic Culture and Fluorescent Antibody Test for the Detection of Leptospira borgpetersenii in Urine of Naturally Infected Cattle Even so, the DNA test missed about 4 in 10 known-positive urine samples.33PubMed Central. Comparison of Real-Time PCR, Bacteriologic Culture and Fluorescent Antibody Test for the Detection of Leptospira borgpetersenii in Urine of Naturally Infected Cattle Dairy herds can also be screened by testing antibodies in bulk tank milk, though this gives only a rough idea of how many cows are affected.34PubMed Central. Bayesian inference for within-herd prevalence of Leptospira interrogans serovar Hardjo using bulk milk antibody testing
Your vet may want blood from several cows, including those that aborted and their herd-mates, to build a herd picture. Urine samples help find carriers still shedding. Aborted fetuses and placentas should be fresh and chilled for DNA testing. A second blood sample a few weeks later can show a rising response that points to recent infection.
Vaccination complicates blood results. Vaccinated cattle make antibodies, so a positive blood test may simply reflect the vaccine. Tell your vet the herd’s vaccination history before testing. Tests that find the bacteria itself aren’t confused by vaccination.
Treating Infected Cattle
Antibiotic treatment reportedly prevents abortions and other breeding problems.35Merck Veterinary Manual. Leptospirosis in Ruminants – Infectious Diseases A single injection of streptomycin is the usual choice and generally clears the kidney infection.36Merck Veterinary Manual. Leptospirosis in Ruminants – Infectious Diseases A single injection of oxytetracycline or tilmicosin, or a short daily course of ceftiofur, also stopped urine shedding.37PubMed. Evaluation of antibiotics for treatment of cattle infected with Leptospira borgpetersenii serovar hardjo
Every antibiotic has a withdrawal period before milk or meat can be sold, and some of these drugs aren’t licensed for lactating cows in every country. Your vet will choose a drug and dose that fits your herd and local rules.
Treating the whole herd at once matters. In one dairy herd, cows treated once with dihydrostreptomycin stopped shedding within a week.38American Journal of Veterinary Research. Effective treatment with dihydrostreptomycin of naturally infected cows shedding Leptospira interrogans serovar hardjo subtype hbardjobovis But more shedding cows turned up six weeks later when only positive cows were treated.39American Journal of Veterinary Research. Effective treatment with dihydrostreptomycin of naturally infected cows shedding Leptospira interrogans serovar hardjo subtype hbardjobovis After the whole herd was treated at the same time, no new infections appeared.40American Journal of Veterinary Research. Effective treatment with dihydrostreptomycin of naturally infected cows shedding Leptospira interrogans serovar hardjo subtype hbardjobovis
Treatment alone doesn’t end the problem, because treated cattle can be reinfected from rats, water or untreated carriers. Pairing it with vaccination stops new infections taking hold.
Vaccination and Biosecurity
Hardjo vaccines prevent about 9 in 10 vaccinated cattle from shedding the bacteria after exposure.41PubMed. Meta-analysis of the efficacy of Leptospira serovar Hardjo vaccines to prevent urinary shedding in cattle In testing, no vaccinated animal had the bacteria in urine or kidneys.42PubMed Central. Bovine Immune Response to Vaccination and Infection with Leptospira borgpetersenii Serovar Hardjo Protection lasts about 12 months, and makers recommend yearly boosters.43PubMed Central. Bovine Immune Response to Vaccination and Infection with Leptospira borgpetersenii Serovar Hardjo
A basic schedule looks like this:
- Give two doses three to four weeks apart before first breeding.44NADIS. NADIS – Biosecurity
- Give a booster every 12 months.45NADIS. NADIS – Biosecurity
- Vaccinate all bought-in cattle on arrival and keep them apart for four weeks.46NADIS. NADIS – Biosecurity
Most cattle vaccines target Hardjo and may not cover strains caught from wildlife. Ask your vet which strains are common in your area and whether your vaccine covers them. Herds with pigs, dogs or heavy wildlife contact may need broader cover.
Biosecurity keeps infection out. Keep a closed herd where possible to avoid bringing in carriers.47NADIS. NADIS – Biosecurity Fence off ponds, streams and rivers and use mains water where you can.48NADIS. NADIS – Biosecurity Isolate cows that abort, and bury, burn or have collected all aborted material.49NADIS. NADIS – Biosecurity
Rodent and water control come down to daily habits. Store feed in rat-proof bins and clear spilled feed. Set bait stations around sheds and check them regularly. Clean and raise troughs so urine and mud don’t collect around them, and drain or fence wet patches where cattle stand.
Protecting Yourself and Your Workers
People can catch leptospirosis from cattle. In one survey of dairy workers, about 1 in 10 showed signs of past infection, and some had a recent infection.50International Journal of Veterinary Sciences and Animal Husbandry. Seroprevalence of leptospirosis in dairy cattle and occupational risk assessment among dairy farm workers Touching cattle urine, milking without gloves, having cuts on the hands and working on a farm for years all raised the risk.51International Journal of Veterinary Sciences and Animal Husbandry. Seroprevalence of leptospirosis in dairy cattle and occupational risk assessment among dairy farm workers Among slaughterhouse workers, those skinning carcasses and handling more carcasses each day were far more likely to have been infected.52PubMed Central. Leptospira seroprevalence and associated risk factors among slaughterhouse workers in Western Bahr El Ghazal State, South Sudan Vaccinating cattle cuts shedding enough to lower the risk to people working with them.53PubMed. Meta-analysis of the efficacy of Leptospira serovar Hardjo vaccines to prevent urinary shedding in cattle
A few habits help. Wear gloves for milking, calving and handling aborted material. Cover cuts and scratches with waterproof dressings. Wear face protection, or keep your face away from urine splash in the parlour. Wash your hands before eating, drinking or smoking.
In people, leptospirosis often starts like flu, with fever, headache and muscle aches. Severe cases can affect the liver and kidneys. Tell your doctor you work with cattle, since that changes what they test for.
What Leptospirosis Costs a Farm
On one dairy farm, profit per liter of milk fell to zero during an outbreak, then recovered step by step as the disease was brought under control.54PubMed. Estimation of economic losses due to leptospirosis in dairy cattle Overall, the outbreak cost up to 84% of the farm’s milk profit.55PubMed. Estimation of economic losses due to leptospirosis in dairy cattle The money goes in several places: lost milk from flabby bag cows, lost calves and longer gaps between calvings, and extra services, vet bills and replacement heifers.