Leptospirosis (Rat Scratch Yellow Fever)
Leptospirosis (Rat Scratch Yellow Fever) is also known as Weil’s disease, Canicola fever, Canfield fever, Seven day fever and Paddy field fever.
Leptospirosis (Rat Scratch Yellow Fever) is a potentially re-emerging, epidemic disease creates a public health problems.
Leptospirosis (Rat Scratch Yellow Fever) causes an acute, severe, septicemic infection leading to death following multi-organ failure.
Etiology
- Leptospira species is grouped into 23 serogroups with more than 260 serovars.
- Leptospira are spiral-shaped bacteria that are 6-20 μm long and 0.1 μm in diameter with a wavelength of about 0.5 μm. One or both ends of the spirochete are usually hooked.
- A dozen rodent species are known to act as reservoir for leptospira.
- Leptospires are broadly classified into pathogenic (L. interrrogans) and non pathogenic (L. biflexa).
Cattle
- L. hardjo
- L. pomona
- L. icterohaemorrhagiae
- L. canicola
- L. grippotyphosa
- L. bratislava, L. hardjoprajitna
- L. hardjobovis
- L. autumnalis.
Dogs
- L. icterohaemorrhagiae
- L. canicola
- L. pomona
- L. grippotyphosa
- L. bratislava
Sheep
- L. pomona
- L. grippotyphosa
- L. hardjo
- L. bratislava
Horses
- L. serovar L. pomona type kennewickii
- L. bratislava.
Pigs
- Serovar, L. bratislava is widely prevalent.
- L. pomona
- L. grippotyphosa
- L. canicola
- L. tarassovi.
Human
- L. hardjo
- L. pomona
Epidemiology
Prevalence of infection
- World wide in distribution.
- The disease is highly prevalent in India in animals and human beings.
Economic impact
- Sub-clinical infection- abortion storm, still births and birth of weak calves, infertility, increased culling rate, agalactia, milk drop syndrome (L.hardjo) and death rate in-cattle, sheep, horses and pigs causes heavy economic losses.
Predisposing factors
- Organism is susceptible to dryness & pH <6 or >8 inhibits the survival.
- Temperature <7-10 °C or >34-36 °C is sensitive to inactivate the organism.
- Moisture and dampness increase the incidence of leptsopirosis.
- In high rainfall area L. hardjo and in low rainfall areas L. pomona is prevalent.
- There is a direct correlation exists between incidence and rainfall Stagnant water preserves more organism than the flowing water.
Transmission
- Rat is a peri-domiciliary mammal excrete leptospires in urine.
- Fox is a sylvatic carrier.
- Human contact with contaminated soil and infected materials able to contract the infection.
- Through licking of urine, penetration via abraded/injured skin, mucous membrane and eyes infection mostly occurs in dogs.
- Natural and artificial insemination would spread the infection.
- Venereal transmission is possible.
Host affected
- All animals including human beings are susceptible.
Pathogenesis
- Upon entry through skin leptopsires soften skin, cross the mucosal surface and bind to the epithelial
- cells. And get attached with extracellualr matrix components by an active process initiated by expressed surface proteins.
- Pathogenic leptospira found extracellularly between cells of liver and kidney and release lymphokines, TNF-α from monocytes through the endotoxic activity.
- TNF-α damage the endothelial cells and produce hemorrhage in severe leptospirosis.
- Vascular lesion is aggrevated by lipopolysaccharide and endotoxin of leptopspires.
- Intravascular hemolysis and interstitial nephritis, septicemia, abortion and mastitis.
- In acute severe septicemic leptospirosis, endotoxaemia, haemorrhages, hepatitis, nephritis and meningitis.
- Subacute leptopsirosis is a moderately severe disease manifested by nephritis, hepatitis, agalactia and meningitis.
- Chronic leptospirosis is characterised by abortion, stillbirth and infertility.
- In occult form no clinical illness seen.
Clinical Signs
Per acute leptospirosis
- Young calves below one month age is characterised by high fever, rapid respiration, haemoglobinuria and death.
Acute Leptospirosis
- Sudden onset of agalactiae in adult dairy cattle and sheep, Icterus and haemoglobinuria in young animals, meningitis, acute renal failure and jaundice in dogs.
Chronic leptospirosis
- Abortion, still birth, retained placenta, weak offspring, infertility, chronic renal failure in cattle, jaundice in dogs and periodic ophthalmia and conjunctival suffusion in horses.
- In chronically infected animals the organism persists in the kideney and genital tract.
- Chronically infected animals carrying the infection for life and become reservoir.
Dogs
- Incubation period is 2-20 days.
- Decrease urine output, anuria proteinuria.
- Jaundiced sclera indicates hepatitis.
- Vomition, fever, dysuria and dark or brown urine.
- Cough, haemoptysis, dyspnoea and increaed respiratory rate Meningitis, fatigue, hearing impairment, respiratory distress, azotemia, renal interstitial tubular necrosis, renal and liver failure in severe form of Weil’s disease.
Cattle
Acute cases
- Cattle is a reservoir for serovar L. hardjo and type L. hardjo bovis and it causes nephritis.
- Leptospirosis is septicaemic in calves and lambs. Dyspnoea, pulmonary congestion, icterus, haemoglobinaemia, haemoglobinuria last for 48 to 72 hours.
- Haemolytic anaemia leading to death and sometimes recovered animals become normal in 7-10 days.
- Enzootic infection in adult cattle.
- Abnormal haemorrhagic milk in dairy cattle.
- No haemolysis noticed.
- Mortality rate is 10-30% & CFR – 5%.
- Abortion 30% Flabby bag syndrome – (Sudden drop milk syndrome) – Somatic cell counts are 10-75%.
- Udder uniformly affected and resume milk production in 10-14 days.
- Leptospiruria is present in upto 30% of affected cows.
Chronic cases
- Abortion and still births is more common in 6-12 weeks of gestation.
- Abortion storm – In mid term to last term pregnancy.
Pigs
- Abortion occurs in 2-4 weeks of pregnancy.
Zoonosis
- Infection by water, food, soil contaminated with infected urine, skin contact.
- Spread of infection during convalescent period rare.
- Swimmers, slaughter house workers, veterinarians, butchers, sewage clearing persons, farm workers at risk.
Clinical signs
- Human Incubation period is 4-14days.
- Disease is biphasic in nature.
First phase
- Flu like fever, chills, myalgia, intense headache and become asymptomatic.
Second phase
- Flu like signs with muscle pain, abdominal pain, vomition, diarrhoea, rash, red eyes, renal failure, meningitis, liver damage, jaundice and highly lethal pulmonary haemorrahge.
- Hypotension, irregular pulse-ECG reveals the type of arrythymia.
- Bleeding of vascular tubules and decreased platelets.
- Increased neck rigidity and cells in cerebrospinal fluid.
Necropsy Findings
- Generalised pale and icteric carcass.
- Enlargement of liver.
- Hepatitis, nephritis, placentitis.
- Leathery placenta.
Diagnosis
- Based on clinical signs and necropsy findings. Isolation of organism by culture using Fletchers medium, Stuarts medium and EMJH medium.
- Identification of organism using dark field microscope (DFM).
- Detection of antibody titer by microscopic agglutination test (MAT).
- MAT titer is 1:100 is considered positive.
Kidney
- Increased serum creatinine and blood urea nitrogen.
Liver
- Serum bilirubin, with normal or mildly elevated SGPT, SGOT and CPK.
Lung
- Chest Xray shows lower and mid zone opacities.
- Molecular diagnosis by PCR.
- Samples Collection.
Acute phase
- Liver, lung, brain, kidney, body fluids, blood, milk, cerebrospinal fluid, thoracic and peritoneal fluids.
Chronic phase
- Urine, kidney, fetal fluid, uterine and other reproductive discharges.
Differential Diagnosis
- Dengue fever, Haemorrhagic fever and Hepatitis. Viral meningitis, Malaria, Typhoid fever, Influenza and Parvo.
- Brucellosis, SMEDI, (Still birth, mummification, early embryonic death, and inferitility, etc).
Treatment
- Doxycycline 100 mg/oral/every 12 hours period for one week. Penicillin 20,000 IU /kg body weight for every 4 hours for one week.
- Doxycycline 200-250mg once a week in adult as a prophylaxis per oral.
- Dogs-penicillin-leptospiraemic phase and doxycycline eliminate the carrier status.
- Detoxification, hydro-electrolyte balance with glucose and salt solutions.
- Dialysis in serious cases must be done. K and P may be increased due to renal failure.
- Corticosteroid (eg.prednisolone 30-60 mg for 7-10 days).
Prevention
Prevention by maintenance of appropriate hygiene, sanitation and management.
Vaccine: Trivalent Leptospira (inactivated vaccine for bovines )
- This vaccine contains three Leptospiral serovars resptectively., L.pomona, L.hardjo and L.grippotyphosa.
- It is a killed vaccine containing, thiomersal inactivated, aluminium hydroxide gel adsorbed vaccine which confers specific immunity against leptospirosis in cattle.
- Available as 30 ml (5 doses) and 6 ml in single doses.
- Canine leptopsira killed vaccine containing L.icterrohaemorrhagiae and L.canicola, L.pomona and L.grippotyphosa are available.
Control
- Pasteurization of milk.
- Rodents control measures.
- Filling of stagnant water place with sand or removal of water should be done.
- Garbages should be discarded / covered.
- Disinfection of infected premises.
- Isolation and identification of a renal carriers for controlling of infection.
