Leptospirosis is a zoonotic disease caused by Leptospira bacteria transmitted through contact with infected animal urine. It is endemic in tropical and subtropical regions including parts of India. The disease affects both animals and humans. In animals, it can cause reproductive issues like abortions. In humans, symptoms range from flu-like illness to severe symptoms involving multiple organ failure. Diagnosis involves microscopic examination of samples, culture, serological tests and PCR. Control relies on rodent control, sanitation measures, vaccination of animals, and personal protective measures for humans.

1. Leptospirosis: Its Epidemiology,
Diagnosis and Control with
particular reference to Assam

2. INTRODUCTION
Leptospirosis is a zoonosis caused by pathogenic spirochetes of the genus
Leptospira.
Disease was first described by Adolf Weil in 1886
In 1908, a Japanese research group led by Ryokichi Inada and Yutaka to first
identified the bacterium as the causative agent of leptospirosis and noted its
presence in rats in 1916
Generally it is transmitted by the infected urine of rodents.
Leptospirosis is in the group of 17 neglected tropical diseases, categorized by
WHO.
Leptospirosis is an underreported disease, and there are no reliable global
incidence figures (WHO, 2015)
Synonyms: Weil's Syndrome, Weil-Vasiliev disease, Swineherd's disease, Rice-
field fever, Waterborne fever, Nanukayami fever, Cane-cutter fever, Swamp fever,
Mud fever, Stuttgart disease, and Canicola fever.

3. Etiology
Aerobic, gram-negative, slow growing
Spirochetes that are fastidious
Characteristic corkscrew-like motility
Leptospira were divided into two groups;
The pathogenic Leptospira were all
classified as members of L. interrogans
The Saprophytic Leptospira were classified
as L biflexa
Long, Thin, Highly Coiled
Under Dark Field Microscopy
Source: Merck Veterinary Manual
Source: Wikipedia

4. Table: Various serovars and their respective carriers

5. CURRENT STATUS OF THE DISEASE
Worldwide major outbreaks were reported from the Latin America and the
Caribbean region (36%), followed by Southern Asia (13%), and North America
(11%) (Claudia et. al., 2020)
In India, the disease is prevalent in almost all the species of domestic animals and
in several rodent species It has been reported more frequently from southern states
although few reports are also available from western states (Gujarat and Rajasthan)
(WHO, 2015)
Human Leptospirosis is reported to be of endemic importance from many States of
India which includes Andaman and Nicobar Islands (since 1988), Gujarat (since
1994), Maharashtra ( since 1998), Kerala and Tamil nadu. (WHO, 2015)
Few reports from Assam. Kader et.al., 2018 carried out a study in cattle from few
districts of lower Brahmaputra valley, Assam and recorded a seropositivity of 11.58
%.

6. Three epidemiological patterns of leptospirosis were defined by
Faine (1994)
• The first occurs in temperate climates where few serovars are involved
and human infection almost invariably occurs by direct contact with
infected animals though farming of cattle and pigs
• The second occurs in tropical wet areas, within which there are many
more serovars infecting humans and animals and larger numbers of
reservoir species, including rodents, farm animals, and dogs
• The third pattern comprises rodent-borne infection in the urban
environment (slums)
EPIDEMIOLOGY

7. EPIDEMIOLOGY
 HOST RANGE
1.Reservoir host: wide range of natural rodent and non-
rodent reservoir hosts which include foxes, rabbits, rat,
mice, moles etc.
2.Carrier hosts: Domestic animals includes cattle,
sheep, goat, buffalo, horse and dogs.
3.Accidental/ Incidental host: Human act as accidental
host of disease.
MODE OF TRANSMISSION
1.Direct contact with an infected animal.
No human to human transmission is reported
2.Indirect contact via soil, water and food contaminated with urine from an infected animal
3.Transplacental transmission may occur if infection occurs during pregnancy
4.Droplet infection –breathing air polluted with droplets of urine, eg. During milking of
cattle and buffalo.

8.  FACTORS FAVOURS EMERGENCE OF LEPTOSPIROSIS
Reservoir and carrier host
Soil salinization -The salinity of the soil provides favourable environment for survival of
leptospires for months together
Climate change - These factors include rainfall, humidity, ambient temperature, water
retaining capacity of the soil, pH and salinity of the soil and surface waters and forest cover
Seasonal variation - It is usually a seasonal disease that starts at the onset of the rainy
season and declines as the rains recede. Sporadic cases may occur throughout the year
Rodent density
Population size of the farm and other domestic animals
Sanitation of animal habitats
Availability of veterinary/ medical services for prompt detection and treatment of animal
leptospirosis and control programs
Personal hygiene

9.  HIGH RISK GROUPS
●Occupational exposure – Farmers, ranchers,
abattoir workers, trappers, veterinarians,
loggers, sewer workers, rice farmers, pet
traders, military personnel, laboratory workers
●Recreational activities – Freshwater
swimming, canoeing, kayaking, trail biking
●Household exposure – Pet dogs,
domesticated livestock, rainwater catchment
systems, infestation by infected rodents
●Other – Walking barefoot through surface
water, skin lesions, contact with wild rodents,
accidental laboratory exposure

10. Occupational vulnerability: about 75% of
leptospirosis cases are farmers
Recreational vulnerability affecting a
wider range of rural populations
Leptospira interrogans,
transported by water in
the environment
Vectors of leptospirosis:
Rice field rodents
(Bandicota sp. And Rattus
sp.)
Leptospirosis: a Zoonoses amplified by seasonal flooding

11. TRANSMISSION CYCLE AND PATHOGENESIS OF LEPTOSPIROSIS
Faisal et. al., 2012
Leptospires invade the body
Via penetrating exposed mucous
membranes or damaged skin
After a variable incubation period
(4–20 days)
leptospires circulate in the blood
replicate in many tissues
including the liver, kidneys,
lungs, genital tract, and CNS
leading to various manifestation

12. DISEASES IN ANIMALS
In Cattle: Incubation period (I.P) : 2–12 weeks
(A)Acute form: Sudden onset of elevated temperature (40-41.1°C), anorexia,
anaemia/jaundice, hemoglobinuria, abortion and depression may be seen
(B) Subacute form: Onset is slow, 'milk drop syndrome' due to mastitis resulting
in reduced yield, thick flaking like of colostrum) and yellow to blood coloration
of milk is common. The symptoms lasts for about weeks. Jaundice may be seen
in some cases
(C)Chronic form: Abortions, still births, foetal deaths, weak calves and retained
placenta cases are common in herds.

13. DISEASES IN ANIMALS
Dogs: I.P: 5–15 days
Elevated body temperature, depression, deep
sunken eyes, anorexia, muscle tenderness,
vomiting, intussuseption, foul breath, ulcerated
gums are usually associated with anaemia and
extensive jaundice that may lead to death.
The acute form of disease, known as “Stuttgart
disease” characterized by vomiting, rapid
dehydration, collapse, necrosis and sloughing of
buccal mucosa and tongue
Image depicting ulcerated gums and sunken eyes
Image depicting vomition

14. DISEASES IN ANIMALS
Swine: Usually infection is mild or inapparent. Occasionally may show pyrexia.
 Only or few affected pigs show acute signs of anorexia, pyrexia and/ or diarrhoea for
1-3 days.
 Chronic cases usually abort in late pregnancy or give birth to weak piglets . and
 Recover become renal shedders for at least 6 months.
Horses: Disease manifestations, though rare and usually mild, include pyrexia, icterus,
periodic ophthalmic and abortion.
Sheep: The common signs include abortion, fever, agalactia, dysponea, jaundice,
hematuria and sudden death.
Goats: May remain symptomless but shed leptospires in the urine for short periods or
may develop jaundice, haemaglobinurea and abortions.
Cats: Although susceptible to experimental infection, seldom suffer from clinical
leptospirosis.

15. DISEASES IN MAN
After an incubation period of 7-14 days the disease is manifested in 2 phases.
1. Early or leptospiraemic phase: The pathogen appears in blood and CSF.
In milder cases, the disease remains a subclinical infection
In others, it may present itself as a 'flu-like' syndrome which is characterized
by sudden high fever, chills, headache, muscle aches, vomiting and
conjunctivitis.
 Non availability of treatment could intensify the disease to second phase.

16. 2. Second or immune phase/Well's syndrome:
The symptoms may gradually worsen leading to
kidney and liver failure, of which the latter results in
jaundice
Widespread haemorrhages occur leading to anaemia,
coma and finally death.
Fig: Red eye caused by leptospirosis
Red eye (conjunctival suffusion due to immune reaction ) is a constant and
characteristic feature.
In rare cases, the most severe forms of the disease present as
atypical pneumonia, or
aseptic (leptospiral) meningitis or
myocarditis
All the severe forms have a mortality rate of 5-10%, which is quite significant

17. Diagnosis
The disease can be tentatively diagnosed on the basis of clinical symptoms
However, confirmatory diagnosis is made as follows:
 Direct examination of samples :
The clinical or morbid materials such as blood, urine, CSF, tissue
scrapings/emulsions should be properly treated with
(a) 10% acetic acid for 5-19 minutes (in case of impression smears), or
(b) 0.25% trypsin for 3-5 minutes (in case of tissues), or
(c) 40% formalin to decontaminate clinical materials, or in smears
by following microscopic techniques as
 Dark field microscopy at 400x magnification
 Silver impregnation staining
Silver impregnation staining
for Leptospira

18.  Isolation of leptospires: These methods include
(i) Culture, (ii) Animal inoculation, and (iii) Culture following animal inoculation
(ii) Animal inoculation: Carried out to enhance the concentration of Leptospira cells or
to remove the bacterial contaminants from the samples.
 In hamsters (3 weeks old): Fatal infection accompanied by jaundice evoked following
inoculation with 0.5-1 ml of sample through intra-peritoneal route
 Guinea pigs (1 week old) inoculated with 0.5-1 ml material, i/p seldom die of the
infection
(i) Culture: The isolation rate of leptospires from clinical specimens is very low.
Media for culturing leptospires are of 3 types,
 media containing serum (Korthof's medium, Fletcher's semi-solid medium etc.)
 media containing bovine albumin fraction V and tween 80 (EM medium, EMJH etc ), and
 synthetic media

19.  Other test being employed:
Immunofluorescence: Useful in examination of urine, other body fluids, and tissues
that have been frozen or are not amenable to silver staining.
Immunohistochemistry: Achieved by using enzymatic or metallic labels on the
secondary antibody. Phosphatase, peroxidase, or metallic gold- labelled antibody can be
used.
Nucleic Acid Probes and Hybridization: Leptospira specific sequences are isolated,
cleaved and labelled with a reporter molecule , then hybridized to ss DNA .
 If the nucleotide sequences in the nucleic acid probe are complementary to those in the
sample, hybridization occurs monitored by autoradiography or calorimetrically
Polymerase Chain Reaction : PCR can rapidly confirm the diagnosis in the early
phase of the disease, when bacteria may be present and before antibody titres are at
detectable levels.

20.  SEROGROUP/SEROVAR SPECIFIC TEST:
Microscopic Agglutination Test (MAT): MAT is the WHO standard
reference test for serological diagnosis of leptospirosis .
MAT determines agglutinating antibodies in the serum of a patient/ animal by
mixing it in various dilutions with live/killed leptospires.
Anti-leptospiral antibodies present in the serum cause
the leptospires to stick together to form clumps observed
using dark field microscopy (DFM).
Accepted endpoint: Final dilution of serum at which
50% or more of the leptospires are agglutinated.
Leptospires observed under DFM (20X)

21.  GENUS SPECIFIC TESTS: These tests are based upon the use of a single antigen
common for the genus Leptospira. The antigen for these tests is prepared from the
non-pathogenic L. biflexa Patoc –1 strain.
 Macroscopic Slide Agglutination Test: This test is carried out with a dense
suspension of leptospires, which agglutinate into clumps visible to the naked eye.
 Indirect Fluorescent Antibody Test: Specimens of blood, urine and
parenchymatous organs are stained with luminescent sera and examined under a
fluorescent microscope. The antigen antibody complex fluoresces brightly and is
visible under the microscope.
 Complement Fixation Test (CFT): CFT is performed using either whole leptospiral
cells or soluble extracts. The CFT is useful in detecting relatively recent infection. .

22.  Enzyme Linked Immuno Sorbent Assay (ELISA): ELISA usually detects only the
antibodies reacting with a broadly reactive genus-specific antigen.
 Microcapsule Agglutination Test (MCAT): This test is based on the passive
agglutination of synthetic polymer carriers, sensitized with mixed antigens of sonicated
leptospires, by leptospiral antibody.
 Lepto Dipstick: This dipstick assay for the detection of
Leptospira-specific IgM antibodies in sera
 Latex Agglutination Test: This test depends on the
sensitisation of commercially available latex particles
with a leptospiral antigen.

23. CONTROL STRATEGIES
IN ANIMALS:
1.Rodent control: Areas which favour rodent survival, the rodent control should be
exercised by suitable means including
(i) poisoning with rodenticide (2% zinc phosphide) ,
(ii) use of predators (cat, cagle etc.),
(iii) trapping,
(iv) biological control either by manipulating or altering the habitat,
(v) mechanical proofing, (vi) rodent repellents,
(vii) electronic barriers (fencing), (viii) fumigation,
(ix) proper storage of foods, animal feeds and grains, and
(x) general cleanliness of surroundings

24. 2. Sanitation:
(i) proper draining of yards, pens, sheds and kennels and their
regular disinfection (with cresol , sodium hypochlorite etc.),
(ii) avoidance of stagnation of water, urine and faeces, and
(iii) burial or burning of infected carcasses, aborted foetus,
placentas and/or bedding
3. Proper Management: Should aim at
(i) breaking of the cycle of infection
(ii) allowing new addition to herd or flock only if such animals
have been found negative to MAT on their initial testing as well
on their retesting
(iii) sero-testing of herd by MAT
 strictly remove carrier animals serving as excreters and
 to isolate infected animals
(iv) prevention of reinfection

25. IN MAN:
The disease control measures include
1. Personal hygiene and protection emphasising in
(i) protection of food articles and utensils from
contamination with urine of rat
(ii) encouraging use of protective clothing (rubber
gloves, goggles, gum-boots particularly when working
in water logged areas or handling animals/animal
products during slaughtering and parturition etc.,
(iii) avoidance of swimming and wading in water of
lakes, ponds, swimming pods contaminated with urine
of rats and livestock, and
(iv) encourage mechanization of agricultural
operations.

26. 2. Sanitation: It includes
(i) disinfection of contaminated work areas such
as food stores, abattoirs, fish and meat processing
plants and animal sheds,
(ii) proper collection, transport, treatment and
secured disposal of garbage and animal excreta
(iii) proper disposal of dead and infected animals,
(iv) disinfection of swimming pool with chlorine,
(v) drainage of wet areas, and
(vi) rodent control in the areas of domestic and
farm environment.

27. 3. Animal related care: It calls for
(i) care in handling of laboratory and other animals
as they may be carriers,
(ii) improvement in occupational hygiene
standards in animal farms/ laboratories
4. Health education: General people and
particularly the high-risk group groups should be
educated about the disease, and the protective
measures to be followed including prohibition of
activities in contaminated waters.

28. CONCLUSION
Leptospirosis is a worldwide underreported neglected zoonosis
In many developing countries, including most of the leptospirosis endemic areas,
laboratory capabilities to detect pathogenic microorganisms are often inadequate
Reservoirs control measures, environmental control programs and animal
vaccination, in combination with a strong surveillance system may significantly
reduce the disease
Public education for people’s awareness of the disease reservoirs and its
transmission is essential
The extensive and good understanding of the eco-epidemiological and cultural
characteristics of a community that faces the problem of leptospirosis is an
essential prerequisite for evolving an effective and acceptable control measure.

29. THANK YOU !