Leptospirosis

Leptospirosis is a contagious disease that infects both animals and humans and is caused by bacteria called Leptospira. There are over 200 different strains of Leptospira found worldwide, with infections being most prominent in areas that have hot and humid climates.

Leptospirosis is considered an occupational hazard for people who work with cattle as well.

Etiology

There are two strains of Leptospira that are frequently identified in dairy and beef cattle.

  • Leptospira hardjobovis
  • Leptospira pomona

Both of the strains may also cause severe illness in humans.

The pathogenic leptospires were formerly classified as serovars of Leptospira interrogans, but they have been reclassified into seven distinct species with more than 200 recognized serovars. Leptospira serovars Grippotyphosa, Pomona, Canicola, and Icterohaemorrhagiae usually cause abortions in cattle during the last trimester. Serovar Hardjo is host-adapted to cattle and can establish lifelong infections in the kidneys and reproductive tracts. The Leptospira located in the kidneys are voided in the urine and serve as sources of infection to other animals1.

Impact on Reproduction

Leptospirosis is one of the major causes of reproductive failure in cattle. Some of the problems that leptospirosis can cause for reproduction in cattle include:

  • Abortions: usually 6-12 weeks after the initial infection2
  • Stillbirth
  • Weak newborns
  • Infertility: low pregnancy rates and increased culling due to low fertility

Clinical Signs

Acute disease occurs in young stock which can show:

  • High fever
  • Hemolytic anemia
  • Hemoglobinuria
  • Jaundice
  • Pulmonary congestion
  • Meningitis

In lactating cows, leptospirosis can cause agalactia with small quantities of blood-tinged milk. A less severe form of this “milk drop syndrome” may occur in hardjo-infected lactating cows in the absence of other clinical evidence of infection. In lactating cows, incidental infections have been reported to cause blood-tinged milk.

The chronic phase of disease is associated with fetal infection in pregnant cows presenting as abortion, stillbirth, or birth of premature and weak infected calves.

Leptospira interrogans serovar hardjo. Courtesy of Dr. J. Glenn Songer

Leptospira interrogans serovar Hardjo. Courtesy of Dr. J. Glenn Songer

Diagnosis

History and clinical signs may indicate leptospirosis in cattle, but diagnosis needs to be confirmed by laboratory tests. Common laboratory tests for leptospirosis include:

Serology - Useful for screening herds with a history of abortions or reproductive problems.

Bacterial isolation - From blood, cerebrospinal fluid, and milk in acute cases. In clinically infected or suspected carrier animals, bacterial isolation can be taken from urine samples. Cows infected with serovar Hardjo can shed the organism in urine throughout life. For other serovars, the dam’s urine can be cultured or examined for leptospires within two weeks of abortion.

The placenta and fetus should be submitted to the laboratory for fluorescent antibody staining or PCR testing for Leptospira.

Necropsy - From organs of animals that died during the acute phase of disease.

Treatment and Prevention

To eliminate the renal carrier state3:

  • A single injection of oxytetracycline (20 mg/kg, IM)
  • A single injection of tilmicosin (10 mg/kg, SC)
  • Ceftiofur (5 mg/kg/day, IM, for 5 days or 20 mg/kg/day, IM, for 3 days)
  • Amoxicillin (15 mg/kg, IM, two injections 48 hours apart)

For control, sources of infection (such as feed or water contaminated by dogs, rats or wildlife) should be identified and eliminated.

Vaccination with a five-way bacterin every six months provies good protection against Leptospira canicola, L. grippotyphosa, L. Hardjo, including the L. borgepetersenii serovar Harjo bovis, L. icterohaemorrheagiae and L. pomona and it is an aid in prevention of urniary shedding of L. Hardjo organisms.

Leptospirosis is a zoonotic disease, and urine and milk of dams may be infective for up to three months, except for serovar Hardjo, in which case cows can be infective for life if not treated.

References

  1. Lillenbaum W, Martins G. 2014. Leptospirosis in Cattle: A Challenging Scenario for the Understanding of the Epidemiology. Transboundary and Emerging Diseases 61 Suppl 1(s1):63-8.
  2. Zelski R. 2007. Leptospirosis in cattle herds. Primefact 445. New South Wales Department of Primary Industries.
  3. Alt DP, Zuerner R, Bolin C. (2001). Evaluation of antibiotics for treatment of cattle infected with Leptospira borgpetersenii serovar Hardjo. Journal of the American Veterinary Medical Association. 219. 636-9. 10.2460/javma.2001.219.636.