LEPTOSPIROSIS IN CATTLE (REDWATER OF CALVES)

LEPTOSPIROSIS IN CATTLE (REDWATER OF CALVES)

DR. UDAY KUMAR, HAZIPUR

Leptospirosis, commonly referred to as “Lepto“, is caused by the spiral-shaped bacteria. Leptospirosis is an economically important zoonotic bacterial infection of livestock that causes abortions, stillbirths, and loss of milk production. Many aspects of leptospirosis in farm animals are poorly understood, in part because of difficulty in diagnosis, complexity of the host-leptospire relationship, and changing patterns of infection. Leptospirosis occurs worldwide and is caused by infection with the spirochete Leptospira. The pathogenic leptospires were formerly classified as members of the species Leptospira interrogans; the genus has recently been reorganized and pathogenic leptospires are now identified in 7 species of Leptospira. Leptospiral serovars are recognized and approximately 200 different serovars of pathogenic Leptospira have been identified throughout the world. Serovars are identified based on antigens on the surface of the organisms. In particular regions, different leptospiral serovars are prevalent and are associated with one or more maintenance host(s), which serve as reservoirs of infection. Maintenance hosts are often wildlife species and, sometimes, domestic animals and livestock. Transmission of the infection among maintenance hosts is efficient and the incidence of infection is relatively high. Incidental hosts are not important reservoirs of infection and the incidence of transmission is low. Transmission of the infection from one incidental host to another is relatively uncommon. Transmission among maintenance hosts is often direct and involves contact with infected urine, placental fluids, or milk. In addition, the infection can be transmitted venereally or transplacentally. Infection of incidental hosts is more commonly indirect, by contact with areas contaminated with urine of maintenance hosts. Environmental conditions are critical in determining the frequency of indirect transmission. Survival of leptospires is favored by moisture, moderately warm temperatures (optimal around 28°C), and neutral or mildly stagnant water; survival is brief in dry soil or at temperatures less than 10°C or more than 34°C. Therefore, leptospirosis occurs most commonly in the spring, autumn, and early winter in temperate climates and during the rainy season in the tropics. Leptospires invade the body after being deposited on mucous membranes or damaged skin. After a variable incubation period (3 to 20 days), leptospires circulate in the blood. During this period, leptospires enter and replicate in many tissues, including the liver, spleen, kidneys, reproductive tract, eyes, and central nervous system. Agglutinating antibodies can be detected in serum soon after the leptospires are in the bloodstream. Appearance of circulating antibodies coincides with the clearance of leptospires from blood and most organs. Leptospires can remain in the kidney and urinary shedding may occur for weeks to many months after infection. In maintenance hosts, leptospires also may persist in the genital tract and, less commonly, in the cerebrospinal fluid and vitreous humor of the eye.

Leptospira. It is one of the commonest causes of reduced fertilty and pregnancy loss in cattle. It also causes milk drop and increased cell counts. Wildlife such as rats can carry the disease and spread infection. Humans can also be infected by the bacteria causing a range of ‘flu’ like symptoms.

Lepto is excreted in urine and milk. Contaminated urine droplets (on the ground or in the air) can enter the cow’s body via the eyes, mouth, nose or broken skin. The bacteria then enter the
blood stream and head for their target organs – ovaries (infertility), uterus (abortion/infertility), udder (milk drop/cell count) and kidneys where the animal ‘carries’ the disease and can then reinfect other cows by shedding the disease in its urine. Leptospira organisms can survive in the environment for weeks to months depending on environmental conditions, and some organisms have been shown to survive in stagnant, standing water or in wet soil for longer than six months if the temperature is favourable.

 

Pathogenesis

Etiology

• Caused by bacteria from the genus Leptospira:

• • There are multiple serovars of leptospirosis, with the ones affecting cattle being:

• • • L. borgpetersenii serovar Hardjo.
    • L. interrogans serovar Hardjo.
    • L. Pomona.
  • Leptospira borgpetersenii serovar Hardjo is the most common serovar of leptospirosis affecting cattle worldwide:

• • • Cattle are the maintenance host for Hardjo.
    • It is endemic in many cattle populations with resultant low to moderate levels of disease.
  • Leptospira interrogans serovar Hardjo is less common than borgpetersenii and is associated with more severe outbreaks of disease:

• • • Serological methods cannot distinguish between both strains of Hardjo.
  • Leptospira Pomona is not as prevalent worldwide and is not as adapted to cattle as Hardjo, resulting in more severe forms of disease.
  • With less commonly implicated serovars, all of which are non host-adapted, disease is more severe:

• • • These serovars include:

• • • • Icterohaemorrhagiae.
      • Grippotyphosa.
      • Bratislava.
      • Canicola.
• After infection with Hardjo, cattle harbor the bacteria in their kidneys for months to years, excreting many leptospires in their urine so acting as a reservoir of infection for other cattle
• Both dairy and suckler cattle can be affected.
• The main source of infection is the carrier animal; water/feed that has been contaminated with infected urine can also be important.
• The organisms gain entry to the body though the membranes of the eyes, nose, mouth, and even the skin, especially if it is injured.
• Infected animals also commonly shed Hardjo in placental fluids and milk.
• In addition, some Leptospira serovars, such as Hardjo, can be transmitted venereally.

Predisposing factors

General

• Risk factors for Hardjo infection in cattle have been reported to include large herds, open herds, contract rearing or rearing of dairy heifers away from the main herd, access to contaminated water sources, co-grazing with sheep (potential maintenance host), and use of natural breeding.

Pathophysiology

• Dissemination of leptospires is probably a result of motility of the organism.
• Virulence factors have not been well described; however, it has been postulated that pathogenic leptospires release haemolysins, sphingomyelinases, and phospholipases.

Timecourse

• The incubation period is generally 7 to 14 days but ranges between 2 and 30 days.
• Hardjo abortion can occur anytime from 3 weeks to 3 months post-infection.

Epidemiology

• Some animals excrete Leptospira continually for a short time and then stop, others shed intermittently for life.
• Transmission is greatest in grazing cattle.
• Carriers can stop or reduce shedding when fed a concentrate diet or a diet that results in an acidic urine.
• The organism can persist in the environment for up to 4 months given sufficient moisture.
• Leptospira do not tolerate drying, exposure to sunlight or extremes in pH or temperature well.
• Spread occurs most rapidly in wet seasons on low lying areas.

 

Occurrence and prevalence of infection —

Most leptospiral infections are subclinical. Leptospira interrogans serovar pomona (L.pomona) is the commonest infection in all farm animals. Cattle are the only reservoir for L.hardjo and is an important cause of abortion. It is also the commonest leptospiral infection in man. In cattle the morbidity rate for the clinical disease may vary from 10-30% and fatality is relatively low at about 5%. Cattle is also maintenance host to L.hardjo-bovis which has low pathogenicity but could cause epidemics of agalactia, milk drop syndrome and a major cause of infertility. On the other hand, cattle are incidental hosts to L.pomona which causes abortion and fatal haemolytic disease in calves.

Leptospirosis in animals

The signs seen in animals will depend on whether the animals are primary or secondary hosts and sometimes they can be asymptomatic.

Primary hosts shed infectious bacteria via their urine into the environment, and generally show only minor clinical signs. In these hosts the Leptospira bacteria remain in the kidneys for long periods of time – at least 18 months and perhaps for years.

Infection in secondary hosts will cause more severe clinical signs:

Cows

• Mastitis
• A drop in milk production

Calves

• Depression
• High fever
• Jaundice (yellow mucous membranes)
• Red water (blood in the urine), with deaths commonly occurring.

How leptospirosis is spread in livestock

Livestock become infected by contact with water or grazing pasture contaminated by urine from infected animals or through mating. Leptospira can survive for extended periods of time in damp soil and stagnant water and can spread rapidly after heavy rain or flooding.

Cows can also pick up the infection directly from each other when they are close together and urinating on each other, like in the milking shed.The bacteria are extremely infectious and can penetrate intact mucous membranes, and skin that has been softened by exposure to water. Cuts and abrasions make it easier for the bacteria to enter the body.The bacteria do not survive well out of water so there is little infection risk from dry surfaces.

Leptospirosis in people

Humans usually become infected via direct or indirect contact with urine from infected animals. This can include contact with urine contaminated water e.g. puddles. The bacteria invade either through the body’s mucous membranes (eyes, nose and mouth) or through cuts and abrasions.

Aborted material or assisting a cow with calving can also cause infection as well as contact with urine or kidneys from home-kill or when hunting (pigs and deer) or when dealing with rodents/possums.

Symptoms

In people it can cause a minor flu-like sickness, but may also make some people seriously ill, needing intensive care at hospital. They may be off work for several months, have lasting kidney or liver damage, and may suffer long term fatigue and depression.

Traditionally the disease has mostly been occupationally-acquired with strong links to the meat processing, farming and forestry industries. Overseas, leptospirosis has also been linked with outdoor recreational pursuits and flooding events.

Risk factors for contracting Leptospirosis:

• Open herd
• Using bulls rather than AI, especially if shared
• Co-grazing sheep with cattle
• Having water courses used by a mixture of animals

 

Differential diagnosis:

Acute leptospirosis must be differentiated from diseases causing haemolytic anaemia with or without haemoglobinuria. They include: Babesiosis, Anaplasmosis, Post parturient haemoglobinuria & Bacillary haemoglobinuria. Chronic leptospirosis causing abortion must be differentiated from all other causes of abortion such as: Brucellosis, Trichomoniasis, Protozoal abortion, Campylobacteriosis, IBR, Mycotic abortion & BVD. In case of chronic leptospirosis with milk drop syndrome it must be differentiated from milk drop due to change of feed or management or epidemic infection such as Bovine Respiratory Disease.

Diagnosis:

A bulk milk sample is a good place to start to give some indication of the level of infection on the farm. On  dairy farms blood samples can be taken which will tell us if they infection is circulating and to find out whether the animal has been previously exposed. Abortion enquiries can sometimes give false negatives due to the interval between infection and abortion.

Treatment:

Animals with acute leptospirosis can be treated with streptomycin (12.5 mg/kg twice daily for three days) or tetracycline ( 10 to 15 mg/kg twice daily for three to five days). Streptomycin treatment can be combined with ampicillin or large doses of penicillin G. Leptospires also are highly susceptible to erythromycin, tiamulin, and tylosin, although these antibiotics cannot be relied on to remove the renal carrier state. A single dose of streptomycin (25 mg/kg) will usually remove the chronic renal carrier state caused by pomona or other serovars; chronic hardjo type hardjoprajitno infections may resist this treatment regimen . Streptomycin is no longer available for use in the United States. Injectable, long-acting oxytetracycline at a dose of 20 mg/kg or amoxycillin  with two injections ( 48 h apart) at a dose of 15 mg/kg may be substituted for streptomycin to treat chronic infections

Good management is vital in the control of leptospirosis and includes:

1. Eliminating access of cattle to surface water or streams used by other livestock.
2. Removing rubbish that harbours wildlife and rats.
3. Limiting access of rodents and wildlife to livestock feed.
4. Eliminating urine drainage into water sources.
5. Reducing contacts between cattle, other livestock, rodents, and wildlife as much as possible.
6. Cleaning, disinfecting, and drying barns, pens, and other confinement areas after use by infected cattle.
7. Draining or fencing swampy areas likely to harbor the leptospires.
8. Vaccinating susceptible animals for relevant serotypes.
9. Keep your herd closed if possible.
10. Use AI rather than a bull.

Control strategy for farms:

• Conduct MAT at periodic intervals as a herd test on 10% of the animals and cull or treat positive reactors.
• · If reactors are found, screen the entire herd by MAT or any other suitable test and cull or treat any other reactors.
• · Screen a cow which fails to carry a calf to term, produces a dead or weak calf, or exhibits any other signs of the disease by a suitable test and treat or cull if found positive.
• · Investigate signs of infection like mastitis and high numbers of abortion.
• · Paired sera samples taken 7- 10 day apart during acute and convalescent phases should be submitted from each suspected case.
• · Paired sera samples from a few apparently normal animals also need to be submitted along with the above.
• · Paired sera are of limited value in chronic infections.
• · Use veterinary gloves while assisting cows in calving.
• · Keep animals away from effluent ponds.
• · Do not spray pastures with effluent stored in ponds during the wet season.
• · Dry out pasture sprayed with effluent before allowing grazing.
• · Properly seal and drain effluent disposal tanks.
• · If pigs are kept on the farm, their effluent should be kept inaccessible to cattle.
• · Treat suspected bulls to reduce the level of urinary shedding.
• · Control of rodents in the farm is important.

Zoonotic implications

Clinical cases in humans by acquiring infection from animals are uncommon. However, farmers who milk cows are highly susceptible to L.hardjo and L.pomona. There is no vaccine available for humans. Infection in humans is most likely to occur by contact with contaminated urine or uterine contents. Leptospirosis is endemic in Tamil Nadu, Kerala and Andamans and is being increasingly reported from other parts of India. It usually affects people who work in agriculture and causes severe morbidity and mortality.(John) It may have a mortality as high as 40% in its icteric form (weil’s disease) (Dutta and Christopher). However the presentation of non-icteric forms of leptospirosis are often non-specific and may be missed unless there is a high index of suspision.(Rajajee, Shankar, and Dhattatri) The ICU mortality in patients suffering from leptospirosis has been recorded to be higher (52%) than compared to the total ICU mortality (31%).(Chawla, Trivedi, and Yeolekar.

It was not until the late 80s that the Andaman Haemorrhagic Fever (AHF) with majority cases showing pulmonary involvement was identified as leptospirosis and severe pulmonary haemorrhage was shown for the first time as a complication of leptospirosis from Andamans, India. This pulmonary form has a case fatality rate of 10-15%.(Vijayachari et al.) The Regional Medical Centre under the Indian Council of Medical Research (ICMR) in Port Blair, Andaman and Nicobar Islands, has now been re-designated as WHO Collaborating Centre for Diagnosis, Reference and Training in Leptospirosis. (WHOCCDRTL).

Vaccination:

Vaccination ususally consists of a primary course of two injections at least 4 wks apart. Ideally the course should be completed in the spring before the main transmission season at turnout. Re-vaccination with a single booster should be given annually to maintain protection and progressively reduce exposure in the herd. If the primary course is given later than spring it should be given in the following spring and annually thereafter.

You would need to vaccinate all breeding animals above 6 months of age. For this reason we advise vaccinating from 6 months to ensure the herd becomes free from disease over a period of a few years. To short cut this you can inject the herd with antibiotics first to clear out carriers. Don’t forget that bulls can carry and spread lepto so they need to be included in your control programme.

Additional herd management

Minimising hazards such as reducing stock access to stagnant water, controlling rodents and other wildlife, and general hygiene will help reduce the risk of transmission and infection.

Other species on farm such as deer, sheep, goats and pigs need to be vaccinated as they contribute to the cycling of disease. Keeping pigs on a dairy farm is a high risk for infection in both cattle and people. Pigs and their effluent should not come in contact with cattle and any pigs on the farm need to be included in the farm vaccination programme.

Preventative methods include vaccinations, with a stringent buying-in protocol highly advisable – such as buying stock from a leptospirosis-accredited herd.

Bacteria can also be shed from the male reproduction tract in the form of semen and be spread among the other cows, therefore the use of artificial insemination is safer than sharing a bull.

Remember, the bull needs regular monitoring to make sure they are BVD, IBR and leptospirosis free.

Other measures include fencing off cattle from potentially contaminated waters, and avoiding mixed grazing and water sharing with sheep.

https://www.pashudhanpraharee.com/major-diseases-of-cattle-and-its-management/

https://veepro.nl/animal-health/leptospirosis-in-cattle-redwater-of-calves/

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