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Synonyms
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Weil's disease (caused by Leptospira icterohaemorrhagiae, named after Adolf Weil), Haemorrhagic jaundice (Leptospira icterohaemorrhagiae), Canicola fever (L.canicola), Dairy worker fever (L.hardjo), Swine herd's disease, Rice-field fever, Sugarcane-cutter's fever, Swamp fever, Mud fever, Fort Bragg fever, Seven-day fever, ‘Elikaicchal’ (Tamil)
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In animals: Stuttgart disease
Type of zoonosis
Definition
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Leptospirosis occurs in all farm animal species and is an important zoonosis. It is an acute or chronic or clinical inapparent infection with multiorgan failure in humans, characterized by fever, icterus / conjunctivitis and myalgia. It causes septicemia, interstitial nephritis, haemolytic anemia and abortion in most species of animals, and mastitis in cattle.
Brief history
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In 1886, Adolf Weil in Heidelberg observed the disease.
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In 1907 , Stimson used silver impregnation staining to the pathogen causing Weil's disease.
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In 1915, Inada (Japan) demonstrated the etiology and isolated the Leptospires.
Etiology
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Pathogenic Leptospires belong to the species Leptospira interrogans, which is subdivided into more than 200 serovars in to 23 serogroups.
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Non-pathogenic or saprophytic Leptospires belong to the species Leptospira biflexa.
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Dogs: L.canicola
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Cattle: L.hardjo
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Swine: L.pomona
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Rats: L.icterohaemorrhagiae
Reservoir and incidence
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Humans are susceptible to all serovars, and they are mostly accidental or incidental hosts.
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Host susceptibility may vary with different serovars, and act as primary maintenance host. Example: pigs and cattle are principle hosts for L.pomona, cattle for L.hardjo and dogs for L.canicola.
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The rat, particularly, Rattus norvegicus, is the chief reservoir host.
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Mice, bandicoots, guinea pigs, gerbils, squirrels, rabbits, hamsters, reptiles, nonhuman primates, livestock and dogs are also reservoirs of Leptospires.
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Rats and mice are common animal hosts for L.ballum. Infection in mice is inapparent and can persist for the animal's lifetime.
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Rodents are the only major animal species that can shed Leptospires throughout their life-span without clinical manifestations.
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High prevalence of leptospirosis recorded in tropical countries with high rain fall and neutral or alkaline soils, and abundance of rats.
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Rodents and pigs are important reservoir hosts and potential spreaders, also agricultural animals and mongoose.
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Outbreaks of leptospirosis by exposure to water contaminated by urine of infected animals.
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Waling on bare foot on the contaminated water during rainy season reflects higher incidence of leptospirosis in humans.
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Survival of Leptospires depends on soil and water condition.
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It is the number one occupational disease in many parts of the country.
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Occupational hazards to
Source of infection
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Urine is the chief source of infection.
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Dogs and rodents are the common source of infection for man.
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Milk from acutely infected cows.
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Genital excretions from cattle and swine.
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Leptospiruria state varies from species to species
Transmission
Disease in man
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Incubation period ranges from 2 days to 10 days
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Two phases of infection have been recognized, viz. bacteremic phase (leptospiraemic phase) for 7 to 10 days and leptospiruric phase for a week to months.
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Two clinical forms are icteric form and anicteric form.
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(a). Icteric form or hepatonephritic form or Weil's disease:
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Sudden fever, headache, myalgia, conjunctivitis, nausea, vomiting and diarrhoea or constipation.
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Severe prostration.
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Petichae on the skin, haemorrhages in the GI tract and proteinuria.
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Hepatomegaly and jaundice.
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Renal insufficiency with oliguria or anuria, azotemia and electrolyte imbalance with the disappearance of leptospiremia and fever.
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Convalescence lasts one or two months, during which time general malaise and myalgia may reappear for few days.
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Uveitis (conjunctivitis).
Figure 1. Uveitis
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(b). Anicteric form: It is the mild form of leptospirosis
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Ranges from inapparent infection to severe infection and death. Biphasic Illness
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Weakness, headache, myalgia, malaise, chills and fever.
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Leukocytosis, painful orchitis (testes not usually enlarged), conjunctival effusion and rash.
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Icteric leptospirosis (Weil's syndrome-usually caused by L.icterohaemorrhagiae) is the most severe form of the disease, characterized by impaired renal and hepatic function, abnormal mental status, hypotension, and a 5-10% mortality rate. Signs and symptoms are continuous and not biphasic.
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Non- suppurative meningitis.
Figure 2. Icteric changes on foot
Figure 3. Icteric conjunctival mucus membrane
Disease in animals
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In cattle
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It may be acute or subacute or chronic infection.
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L.pomona and L.hardjo are the important pathogens in cattle, causing abortion.
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Clinically, fever and anorexia occur with rapid decline in milk yield and atypical mastitis / milk drop syndrome or haemorrhagic mastitis, haemoglobinuria. Also, mild jaundice and severe haemolytic anaemia occurs with enlarged liver and swollen kidneys will be observed.
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Pregnant cows abort (at third trimester of pregnancy) with retention of the placenta (Storms of abortion).
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In pigs
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In dogs and cats
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Gastroenteritis, jaundice and nephritis may occur.
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Acute haemorrhagic form, icteric form and uremic form (Stuttgart's disease) have been recognized.
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L.cnicola and L.icterohaemorrhagiae are the important pathogens of dogs.
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In horses
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In sheep and goats
Diagnosis
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History and clinical signs.
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Dark field microscopy examination of urine or serum (examined immediately after collection, sample should not be placed under ice cool condition, because, it affects the motility of the organism) at early stage of the disease.
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Microscopic agglutination test: It is a ‘gold standard test’ as per OIE. Positive titre is 1:100.
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Culture and identification in EMJH (Ellinghauson McCullough Johnson and Harris) medium. On semisolid or liquid medium the growth of Leptospires is described as Dinger's ring. Other media that can also be used are, Korthof's medium, Stuart's medium, Fletcher's medium and Vervoort's medium.
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Culture is difficult and requires several weeks.
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Molecular diagnosis by PCR.
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Antibody detection in serum and aqueous humor.
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A rapid diagnosis is made with the Dot-ELISA test.
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IgM antibody detection ELISA is most useful for early diagnosis of clinical leptospirosis.
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Silver immpregnation staining (Fondana's staining and Levaditi's staining) can be used to stain Leptospires in tissue section.
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Haematology
Treatment
Prevention and control
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Vaccination of animals, particularly cattle, dogs and swine.
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Chemoprophylaxis of animals with dihydrostreptomycin @ 25 mg/kg body weight.
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Avoid swimming in or drinking from potentially contaminated water.
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Avoid walking bare foot in contaminated or stagnant water.
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Protect workers by providing boots and gloves.
- Doxycycline chemoprophylaxis for persons at high exposure.
- Mass education to create awareness.
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Participants