Leptospirosis, Plague, Scrub typhus

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Leptospirosis
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 hardjoor 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, ofwhich 2 belong to saprophytic leptospires.
Each serogroup consists ofseveral 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 bodythrough 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 for7 days. Theleptospires replicate

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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 commonin 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).
 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

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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 contactwith 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 occupationaland/orrecreational 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

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 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.
Zoonosis
Leptospirosis is a human pathogen. Thebacteria can get into your bodythrough cuts
and scratches, the lining of your mouth, throat and eyes after contact with infected
urine, blood orcontaminated water. Care should betaken 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

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2) lethargy, aching joints, headaches
3) long period of sickness with the potential for renal failure.
Plague is a bacterial infection, which Yersinia pestis is the etiological agent of this
disease, and mostly affects (lungs and lymph nodes and blood vessels ). Plague is a
fatal disease , which approximately more than 200 million people have been dead
by this disease.
The word of plague is believed to come from the Latin word plāga ("blow, wound")
Bubonic Plague
Bubo is a Greek word which is termed for swollen lymph glandes. It is the acute
inflammation and painful swellings of the lymph nodes , it also is the most common
type of Plague.
It will occur when an infected rodent or flea bites you.
The Bacteria will spread through the lymphatic vessels of the infected human until
it reaches a lymph node, where it stimulates the inflammation that causes the lymph
nodes to expand. The expansion of lymph nodes is the cause of the characteristic
lymphadenopathy "bubo".
• Symptoms : sudden high fever , headache , body pain , chills etc.
Pneumonic plague
Is the another type of plague , which arises from infection of the lungs. It causes
coughing and sneezing.

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Pneumonic plague is the only form of plague that can be transmitted from person to
person.
The course of the disease is rapid, unless diagnosed and treated soon enough,
typically within a few hours . Death may follow in one to six days.
• Symptoms : sudden pneumonia , respiratory failure , watery mucus etc.
Septicemic plague
When the bacteria enter the bloodstream directly and multiply there, it’s known as
septicemic plague. When they’re left untreated, bothbubonic and pneumonic plague
can lead to septicemic plague.
Septicemic plague is the least common of there form with a mortality rate close to
one hundred percent.
Yersinia Pestis is a gram negative and noncapsulated, facultative anaerobic
microorganism (family enterobacteriaceae)
It can infect humans and animals via the oriental rat flea which called (Xenopsylla
Cheopis).
It can reproduceinside cells, so even if phagocytosed they can still survive, because
it produces an anti-phagocytic slime layer.
Yersinia pestis was discovered in 1894 by Alexandre yersin .
• Symptoms : fever , chills , body pain , severe abdominal pain etc.

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Transmissions:
 Air droplet : coughing or sneezing on another person
 Direct physical contact : touching an infected person, including sexual
contact.
 Indirect contact : usually by touching contaminated soil or a contaminated
surface
 Fecal-oral transmission : usually from contaminated food or water sources
 Vector borne transmission : carried by insects or other animals.
When a flea bites a human and contaminates the wound with regurgitated blood,
the plague carrying bacteria are passed into the tissue. Once in the body, the
bacteria can enter the lymphatic system.
Diagnostic Technique
1. A blood test can reveal if you have septicemic plague.
2.To check for bubonic plague, use a needle to take a sample of the fluid in
swollen lymph nodes.
3.To check for pneumonic plague, fluid will be extracted from your airways by
a tube that is inserted down your nose or mouth and down your throat. This is
called an endoscopy.
4. By using X-ray .
Treatment
If diagnosed in time ,the various forms of plague are usually highly responsive to
antibiotic therapy. The antibiotics often used are Streptomycin, Chloramphenicol

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and Tetracycline. the newer generation of antibiotics are Gentamicin and
Doxycycline have proven to use against this bacteria.
Prevention and Control
• Isolate infected animals
− Limit number of people in contact
− Personal protection
Surgical mask, gloves, eye protection
• Flea control
− Most effective method to break the chain of transmission (Rodent-flea-man)
− Use of insecticidal spraying (DDT and BHC), use malathion in case of
resistance.
− Indoor spraying, Rat burrows should be insufflated with insecticidal dusts.
• Prevent roaming or hunting of pets
• Rodent control
− Eliminate rodent habitat around home
Brush, food sources, firewood, junk
− Undertaken only after insecticide use
• Insect repellents for skin & clothes
• Insecticide use in epizootic areas.

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Scrub typhus, also known as bush typhus, is a disease caused by a bacteria,
called Orientia tsutsugamushi. Scrub typhus spreads to people through bites of
infected chiggers (larval mites).
 Among Rickettsioses, scrub is the commonest
 Mite borne infectious disease
 Orientia tsutsugamushi
 Transmitted through Larval mites or “chiggers”
 Belonging to family Trombiculidae
 Only larval stages take blood meal
Scrub typhus is transmitted by the mite Leptotrombidium deliense. The vector
mites inhabit sharply demarcated areas in the soil where the microecosystem is
favourable (mite islands). Human beings are infected when they trespass into
these mite islands and are bitten by the mite larvae (chiggers). The mite feeds on
the serum of warm blooded animals only once during its cycle of development,
and adult mites do not feed on man. The microbes are transmitted transovarially
in mites. Scrub typhus normally occurs in a range of mammals, particularly field
mice and rodents.

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SIGNS AND SYMPTOMPS
Symptoms of scrub typhus usually begin within 10 days of being bitten. Signs
and symptoms may include
• Fever and chills
• Headache
• Body aches and muscle pain
• A dark, scab-like region at the site of the chigger bite (also known as eschar)
• Mental changes, ranging from confusion to coma

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• Enlarged lymph nodes
• Rash
• People with severe illness may develop organ failure and bleeding, which can
be fatal if left untreated.
• Five to eight days after the onset of fever, a macular or maculopapular rash
may appear on the trunk and later extend to the arms and the legs in a small
proportion of patients Complications of scrub typhus infection include
pneumonia, acute respiratory distress syndrome (ARDS) like picture,
myocarditis, encephalitis, hepatitis, DIC, acute kidney injury, acute pancreatitis,
transient adrenal insufficiency etc.
TREATMENT
Scrub typhus should be treated with the antibiotic doxycycline. Doxycycline can
be used in persons of any age
PREVENTION
• No vaccine is available to prevent scrub typhus.
• Reduce your risk of getting scrub typhus by avoiding contact with infected
chiggers.
• When traveling to areas where scrub typhus is common, avoid areas with lots
of vegetation and brush where chiggers may be found. Continued,
• If you will be spending time outdoors:• Use Environmental Protection Agency
(EPA)-registered insect repellentsexternal icon containing DEET or other active
ingredients registered for use against chiggers, on exposed skin and clothing.

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• If you have a baby or child:
– Dress your child in clothing that covers arms and legs, or cover crib, stroller,
and baby carrier with mosquito netting.
– Do not apply insect repellent onto a child’s hands, eyes, or mouth or on cuts
or irritated skin.
– Adults: Spray insect repellent onto your hands and then apply to child’s face.
– Treat clothing and gear with permethrin or purchase permethrin-treated items.
Murine typhus, also known as endemic typhus, Mexican typhus, shop typhus,
rat typhus, urban typhus, and flea borne typhus, is caused by the rickettsial
organism Rickettsia typhi (formerly Rickettsia mooseri). Although this zoonosis
is typically maintained in peridomestic rats by flea transmission, humans canalso
be infected. Murine typhus is one of the most prevalent rickettsial diseases of
humans, but it is underdiagnosed and its importance is generally unappreciated.
Murine typhus (Endemic typhus) is a zoonotic disease transmitted by arthropod
vectors that prevails in urban and suburban areas. The etiological agent that
causes disease are Rickettsia typhi and Rickettsia felis. The transmission of R.
typhi and R. felis are associated with Ctenocephalides felis, the cat flea, and
Xenopsylla cheopis, the rat flea. The reservoirs of Murine typhus are domestic
cats, rats, and peridomestic opossums.
The pathogens R. typhi and R. felis are introduced by an arthropod ingesting a
blood meal infected with the disease. The pathogen Rickettsia is an obligate
intracellular coccobacillus alphaproteobacterium. As the pathogen circulates in

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the flea’s body, the pathogens that replicate in the midgut epithelial cells are shed
and excreted in the feces.
Urban Cycle: The rat is the host for the flea X. cheopis. The pathogen is
introduced into the circulatory system of the rat and the Rickettsia is transmitted
back to the flea on subsequent blood meals. The rat flea prefers to feed on rats;
however, it will search for other hosts if rats are not available. The urban cycle is
a route of infection common in overcrowded cities with unsanitary conditions.

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suburban cycle
 In the suburban cycle, the reservoirs are feral and domestic cats and
peridomestic opossums.
 Risk of domestic cats acquiring the infected fleas.
 Feral cats & opossums interact in suburban neighborhoods, entering
backyards if food, water and nesting sites are available.

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Infection: The incubation time of 7 to 14 days passes before onset of the illness.
The onset begins with a fever that lasts 3 to 7 days and will cause a severe headache,
myalgia, nausea, and vomiting. After one week, a maculopapular rash appears on
the trunk and axilla parts of the body that lasts 1 to 4 days.
Diagnosis:Misdiagnosis is commonsince the illness is similar to other dieases. Flea
bites found on the body during a medical examination is indicator for doctors to
considertesting for Rickettsia as a possible pathogen. The differentiation of R. typhi
& R. felis are confirmed through PCR testing and sequencing of the genes.
Treatment:
Murine Typhus is a treatable illness with antibiotic therapy. The mortality rate with
antibiotic use is 1% and 4% without antibiotic use The antibiotic, doxycycline has
proven effective in killing both R. typhi and R. felis pathogens and so far, no
resistance to the antibiotic treatment has occurred.
Prevention & Control: Close and or cover any open cracks, crevices or openings
that rodents, cats, or opossums can enter to hide or nest.
Remove any overgrown foliage and clutter in the yard, which are ideal harborage
sites. Remove all ripe fruit from trees and pick up fallen fruit.
Remove all possible food and water sources such as bringing in pet food/water
bowls at night. Cover all refuse containers tightly.
Outdoorpets onthe property, ensure proper flea controlis in use. Flea drops, collars,
powders containing larvicides and adulticides, such as fenoxycarb, and permethrin.
Mechanical methods such as washing bedding and vacuuming are an excellent way
to prevent pesticide resistance.

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Vacuuming will remove up to 95% of emerging fleas, 90% of eggs, and 50% of
larvae .
If a flea infestation is out of control contact a local pest control specialist