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Leptospirosis
of Domestic Animals
G78-417-A
Leptospirosis of domestic animals is a very complex disease. This NebGuide
examines its diagnosis, treatment, and prevention.
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Donald B. Hudson, D.V.M., District Extension Specialist, Veterinary Science
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* Introduction
* Method of Spread
* Leptospirosis in Domestic Animals
* Signs in cattle
* Signs in swine
* Signs in horses
* Cause of abortion
* Leptospirosis in Other Animals
* Sheep and goats
* Dogs
* Rodents
* Diagnosis
* Control
* Treatment
Introduction
Leptospirosis is an infectious disease of animals and man caused by a spiral-shaped
organism (spirochete) of the genus Leptospira. The important serotypes recognized
in livestock in the United States include Leptospira pomona, L. canicola,
L. icterohaemorrhagiae, L. grippotyphosa and L. hardjo.
These organisms have a wide host range, including man. Among domestic animals,
swine, cattle, dogs, and horses are most frequently affected. Known wildlife
hosts include many of the small rodents, raccoons, foxes, opossums, skunks,
deer, and moose.
Because of the nature of the disease, it should not be considered a problem
of the individual animal but a problem of a population, either a herd or a species
within the area. The disease can be controlled by proper management and the
correct use of available vaccines.
Method of Spread
Leptospirosis is generally contracted by the direct splashing of urine from
infected or carrier animals into the eyes of susceptible animals. It can also
be spread through the skin and mucous membranes from contact with water contaminated
with leptospires. Transmission may also occur during breeding through residual
urine in the genital tract or through infectious semen.
The major sources of contamination are swine, cattle, dogs, and wildlife that
have recovered from the disease and have become carriers. Cattle and swine are
major sources because of the volume of urine and the extent and duration of
leptospires in the urine.
Leptospirosis is an important zoonotic disease (a disease acquired by man from
animals). A significant percentage of human cases are acquired through direct
contact with the urine of infected livestock or with contaminated soil or water.
Many epidemics of L. pomona have occurred among persons swimming in water
contaminated with the urine of infected livestock. The organism may survive
up to six months in alkaline water.
Leptospirosis in Domestic Animals
Signs in cattle. Leptospirosis in cattle may vary in severity from a
mild, inapparent infection to an acute infection that may cause death.
Acute clinical disease occurs more often in young calves, but all ages may be
affected. Cattle may develop a high fever of 104° to 107°F, depression,
loss of appetite, decreased milk production, and weakness. Hemoglobinuria (coffee-colored
urine), anemia, icterus (jaundice), and bloody milk are also seen. In lactating
cows, the udder becomes flaccid and milk flow nearly ceases. The milk is usually
abnormal and may contain thick yellow or reddish clots. Reddish milk may develop
with the onset of hemoglobinuria.
Abortion, frequently the only clinical sign reported, usually occurs two to
five weeks after initial infection. Although abortions may occur earlier, most
occur in the last three months of pregnancy.
The clinical disease may occur with mild signs, and inapparent infections can
occur. Many cattle in a herd may develop serologic titers without apparent clinical
signs.
Signs in swine. The disease in swine is largely subclinical (no apparent
signs of illness) except for abortions, which usually occur during the last
two to three weeks of pregnancy. The sow aborts pigs rapidly with no apparent
signs of illness. Some aborted fetuses may have been dead a short time. Piglets
may be born weak and die shortly after birth.
Signs in horses. The acute phase of the disease in horses following exposure
is frequently subclinical. The infected animal may have a slight temperature
rise and mild loss of appetite. Leptospirosis caused by L. pomona is
widespread among susceptible horse populations.
Within 12 to 14 months after the initial infection, the eyes of many horses
show evidence of uveitis (inflammation of the internal structures of the eye),
a disease commonly known as periodic ophthalmia or "moon blindness."
The amount of eye involvement is variable, and the disease may be arrested after
one or two acute attacks, or may proceed through several acute episodes to total
blindness.
Cause of abortion. Researchers believe that the fetus dies from actual
leptospiral infection and is expelled as a foreign body. During leptospiremia
(Leptospira in the blood) of the dam, some of the leptospires penetrate the
placental barrier and, having escaped antibody from the mother, continue to
multiply in the fetus. In cattle, abortion occurs two to five weeks after the
onset of the disease, and the fetus has usually been dead for several days before
it is expelled. Abortion is not delayed as long in swine; therefore, many infected
fetuses contain viable leptospires when aborted. Leptospirosis is not a common
cause of abortion in horses.
Leptospirosis in Other Animals
Sheep and goats. Leptospirosis occurs in sheep and goats with less frequency
than in cattle and swine. The signs reported are similar to those described
for cattle. A variety of serotypes have been identified, but only L. pomona
has been isolated in the United States.
Dogs. Canine leptospirosis is widespread in the United States. However,
the incidence varies with the environment and is less common in confined dogs.
Leptospira canicola is the most common serotype; L. icterohaemorrhagiae,
L. pomona, and L. grippotyphosa are also responsible for some
infections.
The acute disease in dogs is recognized as a bacterial disease causing elevated
body temperature, vomiting, muscular stiffness, weakness, and nephritis (inflammation
of the kidney). In severe cases, jaundice and death may occur. Central nervous
system signs may occur with or without other clinical signs, and organisms may
be present in the brain tissue for extended periods. Chronic leptospirosis is
primarily associated with chronic kidney degeneration. Shedding of leptospires
in the urine may continue for over a year.
Rodents. Wild rat (Rattus norvegicus) populations in urban and
rural areas are frequently infected with L. icterohaemorrhagiae. Leptospira
ballum is found primarily in wild mice (Mus musculus), but is also
present in some rat populations and has been present in commercially raised
laboratory mice. Other serotypes occur with less frequency in rodent populations.
Diagnosis
Leptospirosis diagnosis in all animals, including livestock, companion, and
wild animals, must be confirmed by laboratory tests. There are no clinical signs
distinctive to this disease but certain signs are suggestive. When L. pomona
is introduced into dairy cattle, the first signs are a sudden drop in milk production,
thickened and blood-tinged milk, anemia, and hemoglobinuria. Affected cows usually
have a fever at this stage. Many cows infected during the last three months
of pregnancy will abort two to five weeks after infection. Abortions and particularly
low conception rates are frequently seen in herds of beef and dairy cattle infected
with L. hardjo.
The most practical means of confirming a diagnosis of leptospirosis is the demonstration
of significant levels of antibodies to leptospires in the serums of recovered
animals. Currently, most veterinary diagnostic laboratories use either the plate
agglutination test with killed antigens or the microscopic agglutination (MA)
test, in which living organisms are used as antigens. Titers greater than 1:100
by MA test or 1:40 or greater by plate test against one or more serotypes are
generally considered significant.
Antibodies can be detected seven to ten days after the onset of the acute phase;
they reach peak levels 30 to 60 days later. In most cases, aborting cattle and
swine have reached peak antibody titers at the time of abortion. The most significant
serologic evidence is a four-fold change in titer between two or more sequential
serum samples taken from individual animals over 10 to 14 days.
Serums taken from cattle during the acute febrile phase should be negative;
those taken from animals that aborted or had been sick at least two weeks previously
should be positive. Because leptospirosis is a herd problem, serum samples must
be obtained from at least 10 animals or 10 percent of the herd, whichever is
greater.
Diagnosis of a leptospirosis outbreak is justified when most of the sero-positive
animals have MA titers of 1:1000 or greater, or plate test titers of 1:160 or
greater (Stoenner antigen), or when paired samples show a four-fold change in
titer. If the infecting serotype is L. hardjo, lower titers are expected.
Leptospirosis in animals may also be diagnosed by demonstrating the organism
microscopically in tissues by fluorescent antibody (FA) techniques and by isolating
leptospires in a culture or in laboratory animals following the injection of
infected material.
Leptospires are most readily isolated from blood or milk taken from animals
during the acute phase, or from the urine, kidneys, spinal fluid, and brains
of recovered animals.
Proper management of infected herds is important. When leptospirosis is diagnosed
in swine or cattle during the early phase, further abortion losses may be reduced
or prevented by promptly vaccinating the entire herd.
Breeding swine and cattle should be vaccinated against serotypes prevalent in
the area. Swine should be vaccinated at 6-month intervals and cattle annually.
Additions to the herd should originate from herds that are free of leptospirosis
and antibodies on the basis of a complete herd test.
Control
Livestock herds can be protected against leptospirosis by a combination of proper
management and vaccination procedures. Because of the widespread distribution
of L. pomona in the United States, all cattle used for breeding purposes
should be vaccinated during early pregnancy to provide the greatest degree of
protection during the last two-thirds of gestation. In western states, vaccination
is often done in the fall when cows are examined for pregnancy. In areas where
L. hardjo or L. grippotyphosa are also prevalent, a trivalent
vaccine is recommended for annual vaccination. Vaccination with L. hardjo
should be done before breeding due to the infertility caused by this serotype.
Yearling calves destined for feedlots should be vaccinated with L. pomona
vaccine.
The vaccine used in infected herds should be identical with the serotype causing
the diseases, as there is little or no cross-protection between vaccine serotypes.
The vaccine should be given to all susceptible livestock on the premises where
infection has been identified.
The future breeding efficiency of herds that have experienced leptospirosis
is usually unaltered. Animals should not be culled because they have had the
disease. In fact, their value may be enhanced because they are solidly immune
against re-infection with the same serotype.
Annual vaccination is recommended for dogs with a booster given if an outbreak
occurs in the area.
Treatment
Antibiotic therapy--Streptomycin, chlortetracycline, or oxytetracycline--is
often successful if it can be given early. Dihydrostreptomycin, 10 mg per pound
or 10 g per 1,000 pound cow, has been reported to be effective for termination
of the carrier or shedder state.
In the face of an acute outbreak of leptospirosis in swine, it is recommended
that chlortetracycline or oxytetracycline be added to complete rations for two
to three weeks at the highest levels for which it is cleared. Vaccination of
the entire herd can be accomplished at the same time. By following this procedure,
immunity can be established in the herd before the antibiotic is removed.
Dihydrostreptomycin can also be given to new additions, such as boars, to clear
them of the Leptospira carrier state. Use a single injection of 10 mg per pound.
Leptospirosis of domestic animals is a very complex disease. Therefore, it is
important to work with your local veterinarian in its diagnosis, treatment,
and prevention.
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File G417 under: ANIMAL DISEASES
F-2, General Livestock
Issued September 1978; 15,000 printed.
Electronic version issued October 1996
pubs@unl.edu
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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June
30, 1914, in cooperation with the U.S. Department of Agriculture. Kenneth R.
Bolen, Director of Cooperative Extension, University of Nebraska, Institute
of Agriculture and Natural Resources.
University of Nebraska Cooperative Extension educational programs abide with
the non-discrimination policies of the University of Nebraska-Lincoln and the
United States Department of Agriculture.
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