leptospirosis

Identity

Preferred Scientific Name

• leptospirosis

International Common Names

• English: leptospirosis in cattle; leptospirosis in sheep and goats; leptospirosis in swine; redwater of calves

Pathogen/s

Overview

Leptospires are motile bacteria with hook-shaped ends, and internal flagella. They can be found in aquatic environments and are sensitive to desiccation. They are Gram-negative, do not stain well, but can be visualized using dark-field microscopy. Leptospires in tissues can be detected by silver impregnation and immunological staining techniques. Leptospirosis can affect all domestic animals and humans, and can vary in severity from mild infections of the urinary or genital tract to serious systemic disease. They are usually excreted in urine. Leptospirosis is a serious zoonotic disease.

Leptospira has several pathogenic species, including Leptospira kirschneri, Leptospira interrogans, Leptospira noguchii, Leptospira borgpetersenii, Leptospira santarosai and Leptospira weilii. These species are divided into over 250 different serovars in 23 different serogroups. Serologically similar leptospires can belong to different species; for example, serovar hardjo belongs to two species interrogans and borgpetersenii, because common surface antigens are shared by the two species which are genetically separate.

Host Animals

Hosts/Species Affected

In maintenance hosts the disease is often mild or latent, and there is prolonged excretion of the leptospires in urine. Other species that become infected are termed incidental hosts. Incidental hosts are usually less susceptible to infection, develop more severe disease, and are less efficient transmitters of the leptospire to other hosts. The following table shows the maintenance and incidental hosts for serovars of Leptospira interrogans:

The main causes of leptospirosis in pigs and ruminants are the following serovars of L. interrogans:

* Serovar hardjo can be of Leptospira interrogans or Leptospira borgpetersenii. Some authors claim recently that Leptospira borgpetersenii serovar hardjo is the commonest cause of bovine leptospirosis, whereas earlier literature considers that Leptospira interrogans serovar hardjo is the commoner cause (Naiman et al., 2001).

Systems Affected

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

List of Symptoms/Signs

Disease Course

Disease in Cattle

Acute leptospirosis is seen mainly in calves. They show signs of fever, anorexia, pass red urine, are jaundiced and many die within 3 to 5 days. Survivors are usually unthrifty for the rest of their lives. Decreased reproductive performance can also indicate the presence of leptospirosis. Leptospirosis can cause stillbirths and abortions in late pregnancy. A cow may show no signs of illness before or after the abortion or stillbirth. Leptospirosis can decrease a calf drop by 40% or more during a bad epidemic. Mastitis may also be caused by leptospirosis. Cows show signs of fever and depression and go off their feed. The udder is flaccid in all four quarters and milk yield decreases. Milk is yellowish and may contain red flecks but usually returns to normal in 4 to 5 days, full production being restored after 2 to 3 weeks. Within a herd where there are cases of acute leptospiral mastitis, a large number of cows will show no signs of disease, but will have a fall in milk production. Several weeks later these cows may then abort.

Cattle that recover may become carriers and shed the organism in their urine. The organism can colonize the kidneys and cause nephritis and lead to excretion of the bacteria in urine (Yener and Keles, 2001; for further discussion, see Epidemiology section).

Leptospira pomona and L. hardjo can cause localized renal infections in young animals, leading to diarrhoea, anaemia, haemoglobinuria and abortion.The kidneys are swollen, with multi-focal petechial and ecchymotic haemorrhages that become pale with time. The liver may be swollen, with minute areas of focal necrosis. Petechial haemorrhages in other organs are seen in fulminating cases, however, in the more prevalent Leptospirahardjo infections, the lesions are primarily restricted to the kidneys.

Disease in Pigs

Leptospirosis in pigs causes reproductive losses in breeding herds throughout the world. Losses are due to abortion, stillbirths, weak piglets, and reduced fertility. Pigs are maintenance hosts for serovars of the pomona, australis and tarassovi serogroups, while strains of serogroups canicola, icterohaemorrhagiae, and grippotyphosa are often incidental infections. The most important serovar in pigs is pomona, which is found worldwide. Other serovars found in pigs are tarrassovi, bratislava, canicola, copenhageni, and icterohaemorrhagiae.

Epidemiology

Cattle that recover from leptospirosis may become carriers and shed the organism in their urine. The organism can colonize the kidneys and cause nephritis and lead to excretion of the bacteria in urine (Yener and Keles, 2001). Cattle can shed leptospirosis in the urine for over 12 months.

If the urine is passed into an environment favourable to the bacteria, for example into moist, shaded areas with moderate temperatures, the bacteria can survive for a number of weeks. Survival in the environment can also be extended if the bacterium is picked up by carrier animals (rats, wild pigs, bandicoots, etc.) which can then re-infect the herd with their urine. Leptospires are able to penetrate the membranes of the mouth, nose, eyes and broken skin. Muddy areas around water troughs, water holes and dams are sites of infection. Pigs can act as long-term carriers of serovars pomona and tarassovi. Therefore leptospirosis is more likely on mixed dairy-pig properties or when feral pigs are present. As well as transmission via urine, sexual transmission is an important source of infection (Heinemann et al., 2000).

Zoonoses and Food Safety

Leptospirosis presents an important zoonotic risk to people working closely with pigs.

Disease Treatment

Treatment includes antibiotic therapy. Administration of streptomycin, chlortetracycline or oxytetracycline in the early stages of infection reduces the number of leptospires in the tissues and the amount of excreted organisms.

Prevention and Control

It is possible to eradicate leptospirosis from infected farms by a combination of vaccination, diagnostic tests, drugs and improved hygiene and biosecurity. The greatest threat to eradication schemes is the introduction of infected animals and contact with infected rodents or wild animals (including contact with feral pigs). Vaccination against leptospirosis is common in pigs and cattle. Most vaccines are formalin inactivated, and contain one or more serovars, with aluminium hydroxide adjuvant. Pregnant cows should be vaccinated promptly with killed vaccine. All cattle aged more than 6 months should be vaccinated, with a booster, after 4 weeks. Cows should have an annual booster at mid-pregnancy or at drying off. A monovalent vaccine against Leptospira borgpetersenii serovar hardjo can prevent it colonising the kidneys and greatly reduce excretion of the bacteria (Bolin and Alt, 2001).

For pig farms, control depends on combined use of antibiotic therapy, vaccination, and husbandry (including strict biosecurity with rodent control). Outbreaks should be controlled with streptomycin at 25 mg/kg, and vaccination of at-risk stock, followed by a vaccination programme. If vaccination is not possible, a programme of medicated feed (chlortetracycline or oxytetracycline 600-800g/ton of feed) fed continuously or 'one month on one month off', can be used (Ellis, 1999)

References

African Union-Interafrican Bureau for Animal Resources, 2011. Panafrican Animal Health Yearbook 2011. Pan African Animal Health Yearbook, 2011:xiii + 90 pp. http://www.au-ibar.org/index.php?option=com_flexicontent&view=items&cid=71&id=109&Itemid=56&lang=en

Bolin CA, Alt DP, 2001. Use of a monovalent leptospiral vaccine to prevent renal colonization and urinary shedding in cattle exposed to Leptospira borgpetersenii serovar hardjo. American Journal of Veterinary Research, 62(7):995-1000; 38 ref.

Ellis WA, 1999. Leptospirosis. In: Diseases of swine, 8th edition. Oxford, UK: Blackwell Science, 483-354.

Heinemann MB, Garcia JF, Nunes CM, Gregori F, Higa ZMM, Vasconcellos SA, Richtzenhain LJ, 2000. Detection and differentiation of Leptospira spp. serovars in bovine semen by polymerase chain reaction and restriction fragment length polymorphism. Veterinary Microbiology, 73(4):261-267; 15 ref.

Naiman BM, Alt D, Bolin CA, Zuerner R, Baldwin CL, 2001. Protective killed Leptospira borgpetersenii vaccine induces potent Th1 immunity comprising responses by CD4 and gammadelta T lymphocytes. Infection and Immunity, 69(12):7550-7558.

OIE Handistatus, 2002. World Animal Health Publication and Handistatus II (dataset for 2001). Paris, France: Office International des Epizooties.

OIE Handistatus, 2003. World Animal Health Publication and Handistatus II (dataset for 2002). Paris, France: Office International des Epizooties.

OIE Handistatus, 2004. World Animal Health Publication and Handistatus II (data set for 2003). Paris, France: Office International des Epizooties.

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (data set for 2004). Paris, France: Office International des Epizooties.

OIE, 2009. World Animal Health Information Database - Version: 1.4. World Animal Health Information Database. Paris, France: World Organisation for Animal Health. http://www.oie.int

OIE, 2012. World Animal Health Information Database. Version 2. World Animal Health Information Database. Paris, France: World Organisation for Animal Health. http://www.oie.int/wahis_2/public/wahid.php/Wahidhome/Home

Radostits OM, Blood DC, Gay CC, 1994. Diseases caused by Leptospira. In: Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses. London, UK: Bailliere Tindall, 884-898.

Yener Z, Keles H, 2001. Immunoperoxidase and histopathological examinations of leptospiral nephritis in cattle. Journal of Veterinary Medicine A, Physiology Pathology Clinical Medicine, 48(7):441-447.

Zaki SR, Shieh WJ, 1996. .

Links to Websites

Distribution Maps