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Leptospirosis

Introduction

Leptospirosis is a bacterial disease that affects farm animals, wildlife and humans.

There are many different strains or serovars, carried by rodents and many other wild animals including rabbits, skunks and birds. Cattle, pigs and dogs are the main domestic animal carriers of leptospirosis.

Leptospirosis in cattle is generally caused by one of two strains: Leptospira hardjo or Leptospira Pomona. These two bacteria infect the kidney and genital tract of cattle.

Causative Agent

Leptospirosis is primarily a disease of animals, occasionally infect humans. It is caused by pathogenic spirochete of the genus leptospira that traditionally consist of two species, Leptospira interrogans and Leptospira biflexa. The former includes all pathogenic serovars and the later includes the saprophytic strains. Leptospira strains have been divided into 26 serogroups, of which 2 belong to saprophytic leptospires.

Each serogroup consists of several strains designated as seorovars. Nearly 300 host adopted leptospiral serovars are naturally carried by more than a dozen species of rodents, wild and domestic animals. The moderate to highly conducive abundantly available variety of hosts, results in successful perpetuation of this organism. The leptospira serovars predominantly present in India are L.andamana, L.pomona, L.grippotyphosa, L.hebdomadis, L.semoranga, L.javanica, L.autumnalis, L.canicola.

Pathogenesis

Leptospira enter the body through exposed mucous membranes in the mouth, eyes, skin abrasions or gastrointestinal tract. The incubation period for leptospirosis is 4 to 20 days. The leptospires circulate in the blood for 7 days. The leptospires replicate in the liver, kidneys, lungs, genital tract and central nervous system. The bacteria remain in the kidneys and may be shed in the urine for a few weeks to many months after infection.

Clinical signs

Leptospirosis is less common in cattle under 15 months of age than in older animals. The clinical signs of infected calves include;

High fever Hemolytic anemia (breakdown of red blood cells) Hemoglobinuria (blood/hemoglobin in urine)

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Jaundice (yellowing of tissues) Meningitis and death. Myalgia Headache Conjuctival suffusion Oliguria/Anuria and/or proteinuria Nausea vomiting Abdominal pain

Diagnosis

Serological evaluation of a herd or pen can infer antibody production against leptospira. Urine can be tested using dark-field microscopy and/or immunofluorescence. However, these tests are expensive and the dark-field microscopy isn’t very sensitive. The gold standard is bacterial culture. Leptospira can be isolated from blood, urine, kidney, liver or any other tissue infected by the bacteria.

Transmission

Transmission of leptospira often involves direct contact with infected urine, placenta or milk. It can be transmitted venereally or transplacentally. The most common transmission is through direct or indirect contact with infected urine. Dairies commonly have leptospira contaminations in their environment. Dairy feeder calves are probably the largest carriers of leptospira in commercial feedyards. Dairy calves commonly suckle the sheaths and scrotums of other calves in the pen. This would be a direct contamination of infected urine from carriers by this suckling habit.

Leptospira can also survive in the environment. Leptospira favors moist environments and moderately warm temperatures. Leptospira can survive for extended periods in stagnant water (i.e. waterholes in pens). Survival of leptospiral is brief in dry soil, cold temperatures or very hot temperatures. Therefore leptospira outbreaks are most common in dairy calves in the fall and spring.

Factors Responsible For The Emergence Of Leptospirosis

The conditions that are favourable for maintenance and transmission of Leptospirosis are:

a) Reservoir and carrier hosts

Leptospirosis has a very wide range of natural rodent, and non-rodent reservoir hosts especially rats, cattle, dogs, foxes, rabbits, etc. The animals act as carriers of the leptospires and excrete large number of leptospires in their urine, thus responsible for the contamination of large and small water bodies as well as soil.

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b) Flooding, drainage congestion

Flooding and drainage congestion may be risk factors for contamination of water bodies with infected animal urine. Water logged areas may force rodent population to abandon their burrows and contaminate the stagnant water by their urine.

c) Animal-Human Interface

The potential for infection increases through exposure from occupational or recreational activities without proper protection. Poor cleanliness/sanitation in recreational areas may attract animal host such as rodent thus increases the risk of contamination. These may be due to poor maintenance of facilities, improper disposal of waste and public attitude/ apathy.

d) Human host risk factors

Several sections of the population are more susceptible to infection such as those not previously exposed to the bacteria in their environment (naïve immunities), and those with chronic disease and open skin wounds.

HIGH RISK GROUPS

Exposure depends on chance contacts between human and infected animals or a

contaminated environment through occupational and/or recreational activities. Some

groups are at higher risk to contract the disease such as:

Workers in the agricultural sectors Sewerage workers Livestock handlers Pet shops workers Military personnel Search and rescue workers in high risk environment Disaster relief workers (e.g. during floods) People involved with outdoor/recreational activities such as water recreational activities,

jungle trekking, etc. Travelers who are not previously exposed to the bacteria in their environment especially

those travelers and/or participants in jungle adventure trips or outdoor sport activities People with chronic disease and open skin wounds.

Treatment

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Leptospira is a bacterium that is susceptible to dihydrostreptomycin or long-acting oxytetracycline. We are currently recommending a mass-treatment of the pen with Tetradure 300 at 5 cc/cwt subcutaneously. This new oxytetracycline has blood levels above MIC (minimum inhibitory concentration) for eight days. Cattle should also be vaccinated with an IBR/Lepto vaccine at the time of mass-treatment.

Prevention

There are two avenues of prevention for leptospirosis: 1) vaccination and 2) environmental sanitation. Since dairy cattle are the highest risk for leptospirosis, we are recommending that all dairy calves receive a leptospirosis vaccination upon arrival.

There are many different brands available and none seem to be better nor worse than the others. Vaccination will not stop an infected animal from shedding the bacteria however it will help reduce the infection of naïve calves. Environmentally, we need to be sure that we remove areas of stagnant water in the feeding and hospital pens. Especially, if there are dairy calves in the pen.

For people who work with animals:

Cover cuts and abrasions with a waterproof dressing; Wear protective clothing (for example, gloves, eye shields or goggles, aprons and boots)

when working with animals that could be infected, especially if there is a chance of contact with urine;

Wear gloves when handling cattle placentas or stillborn or aborted calves or carcasses; Shower after work and wash and dry hands after handling potentially infected material;

Do not eat or smoke while handling animals that may be infected. Wash and dry hands before smoking or eating;

Vaccinate livestock as recommended by your vet.

For other people:

Avoid swimming in water where there is a possibility of contamination with animal urine.

Cover cuts and abrasions with waterproof dressings, especially before coming into contact with soil, mud or water that may be contaminated with animal urine.

Wear footwear outdoors, especially when walking in mud or moist soil. Wear gloves when gardening. Control rodents by cleaning up rubbish and removing food sources that are close to

housing. Do not feed raw offal to dogs.

Zoonosis

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Leptospirosis is a human pathogen. The bacteria can get into your body through cuts and scratches, the lining of your mouth, throat and eyes after contact with infected urine, blood or contaminated water. Care should be taken when necropsying animals suspected of being infected with leptospira.

How can we prevent exposure?

1) Cover all cuts and broken skin before and during work

2) Wear protective clothing and eyewear when necropsying

3) Wash you hands after handling any animal before eating, drinking, smoking, dipping, or chewing tobacco.

Human clinical signs of leptospirosis:

1) fever and flu like symptoms

2) lethargy, aching joints, headaches

3) long period of sickness with the potential for renal failure

Prepared By Amjad Khan Afridi

Submitted To Sir Ghadir Ali