Leptospirosis in dairy cattle

By Lex Turner and Jill Stephens, Department of Primary Industries and Fisheries, Queensland Government.

12 January 2006

7 minute read

Introduction

Leptospirosis is serious infectious disease of dairy cattle. It is important not only because of its detrimental effects on the health and production of the herd, but also because it is transmissible to humans from cattle.

In humans it can cause serious, long-term illness.

A vaccination program can provide long-term immunity in cattle against leptospirosis, thus protecting the herd and humans from the disease.

Dairy cattle differ from other types of livestock production systems in having management factors that increase the risk of exposure infectious disease.

For leptospirosis these factors include:

close contact — with dairy workers and within the herd

confinement during milking, yarding etc and

moist conditions.

Therefore, disease prevention becomes a higher priority under these conditions in order to avoid high rates of disease in the herd.

Causes and symptoms of leptospirosis

(i)Leptospira interrogans serovar pomona

Symptoms: usually affects calves causing fever, depression, acute anaemia, small blood spots on gums, and redwater; in older cows it can cause abortion, and mastitis with reduction in milk yield and milk discolouration.

(ii) Leptospira interrogans serovar hardjo

Symptoms: usually affects pregnant or lactating cows causing fever, a flabby mastitis with severe drop in milk production, milk discolouration and abortion.

Animal welfare and effects on production

- Animal welfare is a major concern and more recently, the consumers’ demand.
- One of the main measures of welfare is freedom from disease.
- A vaccination program can significantly reduce the incidence of disease.

L. pomona infection:

can affect most of the calves in a herd, with a death rate of up to 100 per cent;

in calves is now a less common disease, due to temporary immunity gained from drinking colostrum from vaccinated cows;

in older cattle can cause sudden and severe reduction in milk yields; and

sometimes causes abortion.

L. hardjo infection:

affects many cows in a herd;

results in a sharp drop in milk yields for up to 14 days;

results in an increased milk leucocyte count; and

may cause abortion in 5–10 per cent of affected cows, 6–12 weeks after infection.

Human health

Leptospirosis in humans causes:

- severe influenza-like illness usually lasting about one week;
- in some cases, a chronic recurring disease; and
- occasionally severe nervous symptoms.

There is no leptospirosis vaccine for humans.
The best way to prevent leptospirosis in dairy workers is by vaccinating the herd to eradicate the disease from the cattle.

Preventing leptospirosis in humans is important in order to avoid:

the debilitating illness itself;

the costs associated with employees being unable to work; and

potential liability if precautions are not taken to vaccinate against preventable diseases.

Farmers must take responsibility to prevent infection risks to their workers, family, visitors and themselves.

Transmission

The spread of leptospirosis bacteria involves the following factors:

- infected animals can shed the bacteria in their urine for many months or even years, causing new infections in any susceptible animals;
- humans and cattle can become infected by inhaling fine droplets of urine splashing from infected cows during milking;
- the bacteria can penetrate the mouth, nose, eyes or damaged skin;
- most mammals including man, cattle, pigs, sheep and rodents can be infected;
- the bacteria can survive for weeks in water, mud and damp soil eg. around dairies.

Potential risks

The leptospirosis bacteria:

can cause serious disease in dairy workers and dairying families;

are common organisms which are readily spread in the environment by any infected mammals eg. pigs and rodents;

can cause severe outbreaks in a herd, especially after rain; and

infection can persist indefinitely in unvaccinated herds.

Incidence

ARI reported infections in 23 dairy herds in Queensland from 1996 to 2001, 39 per cent infection rate was found in a survey of 2 800 beef cattle in central Queensland.

Potential economic losses

Potential losses due to leptospirosis infection in a herd include:

calf deaths

abortion

reduced milk production

treatment costs

employment costs for relief staff when workers become infected

workers compensation costs and

legal liability for preventable disease contracted by staff at work.

Prevention and control

A vaccination program can provide long-term immunity in cattle against leptospirosis.

Aim: to vaccinate all susceptible cattle before infection occurs, so that chronic urinary shedding is prevented. When leptospirosis is already present in the herd the following points are important:

Vaccination will immunise young uninfected cattle against the organism.

The older chronic carriers will be gradually culled, leaving only immune cattle.

Vaccination does not prevent urinary shedding of the organism in previously infected cattle.

Veterinary treatment is required to cure the disease.

When the disease is not already present:

a vaccination program will prevent infection;

consequently urinary shedding of bacteria will not occur; and

the herd will remain free of leptospirosis with an effective vaccination program.

Vaccination program

- Vaccinate all cattle with a combined hardjo and pomona (‘2in1’) vaccine.
- The first dose is given at three–six months of age.
- A second dose should be given four–six weeks later.
- Calves vaccinated before six months of age (to protect against pomona redwater) require revaccinating at six months, and again four–six weeks later, as maternal antibodies may interfere with acquiring long-term immunity before six months of age.
- Cattle should be given a booster vaccination every 6–12 months as required.
- Boosters are best given two–four weeks before calving or before the wet season.
- Six-monthly vaccination may be warranted, if a farm has a history of leptospiral problems.
- Vaccinate all livestock on the property as all stock, including bulls and steers, can be infected and become chronic urinary shedders.
- All new animals brought onto a property should be fully vaccinated before being introduced into the herd.
- It is important to follow the advice given for the specific vaccine being used as recommendations vary for different manufacturers.

NB Using a combined leptospirosis-clostridial ('7in1') vaccine will improve the efficiency and economy of the vaccination program.

Vaccination costs

The cost to vaccinate a herd can vary significantly, the price per head can be affected by:

the total number of cattle to be vaccinated — larger herds generally cost less per head;

the regional prices;

the price from the particular supplier of the vaccine; and

acquiring vaccines when on special can significantly reduce the overall cost.

It is important to compare the different brands and various retailers to ensure implementing the most economic vaccination program.

Vaccine costs for leptospirosis

Vaccine costs in this article indicate the cost of the doses only (2003 costs) and do not include labour, materials or facility costs.

$0.70 per dose (2003 price) of a leptospirosis ‘2in1’ vaccine for a 100-cow herd;

if herd includes 100 cows, 3 bulls, 25 heifers, plus 40 heifer calves (calves require two doses) g 208 doses/yr @ $0.70/dose = $145.60/year.

Therefore the program would break even, if the equivalent of one animal (valued at $1 000) was saved every seven years by vaccination against leptospirosis.

Combined leptospirosis and clostridial vaccines
Using a ‘7in1’ vaccine (combined leptospirosis and clostridial vaccine) saves time and labour costs, because it requires only one injection instead of two, to protect the herd against the five clostridial diseases and the two types of leptospirosis .

Vaccine costs

$1.00 per dose (for 100-cow herd) g 208 doses/year = $208/year.

Therefore the program would break even, if the equivalent of one animal (valued at $1 000) was saved (from the effects of any of the clostridial diseases or leptospirosis) every five years by a ‘7in1’ vaccination.

Important considerations when vaccinating cattle

- The manufacturer’s instructions should be followed closely.
- Store and handle vaccines correctly to ensure their effectiveness is not reduced.
- Safety precautions for workers handling vaccines and associated equipment should be adhered to carefully.
- Ensure safe disposal of used equipment, avoiding environmental contamination.
- Animals should be in good health to optimise the immunity gained.
- Vaccination does not provide instant protection — generally full protection doesn’t occur until up to four weeks after the initial doses.

Summary

A vaccination program can be a very cost-effective management tool in avoiding the potentially high production losses,animal suffering and the risk of human infection due to leptospirosis in a dairy herd.

Significant legal penalties could be awarded against a dairy farmer in the case of an employee becoming infected with leptospirosis.

It is the farmer’s responsibility to provide a safe working environment.

January 2006