Leptospirosis

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  • Topic: Leptospirosis, Leptospira, Infection
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Leptospirosis

Also known as Weil’s Disease, Mud fever, Canicola fever, Flood fever, Swineherd’s Disease, Japanese Seven Days fever.

Definition and Background

* A bacterial zoonotic disease caused by spirochaetes of the genus Leptospira that affects humans and a wide range of animals, including mammals, birds, amphibians, and reptiles.

* First described by Adolf Weil in 1886 when he reported an “acute infectious disease with enlargement of spleen, jaundice and nephritis”

Causative Agent

Leptospira - genus bacteria was isolated in 1907 from post mortem renal tissue slice.

Commonly found: Leptospira pyrogenes, Leptospira manilae, & other species like L. leterohemorrhagiae, L. canicola, L. batavia, L. Pomona, L. javinica

Predisposing Factors

Direct exposre to the microorganism is the method in which the disease is contracted.

* Occupational exposure: farmers, abattoir workers, trappers, veterinarians, loggers, sewer workers, rice field workers, and military personnel.

* Recreational activities: fresh water swimming, canoeing, kayaking, and mountain biking in warm areas.

* Household exposure: pet dogs, domesticated live stock, rainwater catchment systems, and infestation by infected rodents.

Source of Infection

Infection comes from contaminated food and water, and infected wild life and domestic animals especially rodents.

1. Rats ( L. leterohemorrhagiae) are the source of Weil’s disease frequently observed among miners, sewer, and abattoir workers.

2. Dogs (L. canicola) can also be the source of infection among veterinarians, breeders, and owners of dogs.

3. Mice (L. grippotyphosa) may alos be a source of infection that attacks farmers and flax workers.

4. Rats (L. bataviae) are the source of infection that attacks rice field workers.

Modes of Transmission

* Wild mammals seem to serve as the primary reservoir of most leptospiral serovars. The organism has been found in more than 160 mammals, including rats, pigs, dogs, cats, raccoons, and cattle. Rats are considered the most important reservoir, as they are the most common source worldwide. Dogs are often carriers of leptospires, which can cause problems because of their close association with people.

* Transmission occurs by contamination of water, soil, or vegetation by urine excreted from infected animals. Humans can become infected upon contact of the contaminated material with abraded skin, mucous membranes, or when the contaminated material is ingested.

* Humans are considered incidental hosts to the disease because transmission of the disease between people is rare, at best. Humans are the end of the line of the disease, with very rare exceptions.

Modes of Transmission

1st
Gastrointestinal Tract
Ingestion of contaminated water/food with urine / carcasses of infected wild / domestic animals.

Blood

Contact through swimming in contaminated pools of water with urine/ carcasses of infected wild/ domestic animals. 2nd
Blood
Skin and mucous membranes

Entry via nose, eyes, mouth and broken skin

3rd
Contact with contaminated water and soil
Bites from infected animals (cattles, dogs, rodents, wild animals)

Incubation Period
* 6 – 15 days/ 2 – 8 weeks

Clinical Manifestations
* 1st stage:    Septicemic/ Leptospiremic Phase (4 – 7 days) -    onset of high remittent fever, chills, headache, anorexia, nausea & vomiting, abdominal pain, joint pains, muscle pains, myalgia, severe prostration, cough, respiratory distress, bloody sputum. * 2nd stage:    Immune/ Toxic Phase (4 – 30 days)

-    if severe, death may occur between the 9th & 16th day 2 types:
* Anicteric (without jaundice) – return of fever of a lower degree with rash, conjunctival injection, headache, meningeal manifestations like disorientation, convulsions & signs of meningeal irritations...
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