Flashcards in Lecture 2 - Flea Borne Diseases Deck (88)
Fleas are wingless, bloodsucking insects
Have existed for at least 50 million years
Fleas have a wide range of hosts
More than 200 species of mammals
Fleas can cause dermatological problems and act as zoonotic vectors
Flea associated ID cases seem to be concentrated in coastal and more temperate zones that are ideal for rapid flea life cycles
Flea-associated ID cases seem to be concentrated in ___________ zones that are ideal for rapid flea life cycles
coastal and more temperate
Genus Yersinia consists of 3 main pathogenic species
Y. pestis (causes plague)
Y. enterocolitica (enteric, rarely in blood)
Y. pseudotuberculosis (enteric, rarely in blood)
Y. pestis can lead to (3 things)
Acute febrile lymphadenitis (bubonic plague)
Three Major Urban Pandemics
1. AD 541-700s Egypt and spread throughout the world
2. 1320s- 25 million Europeans died during this 5 year outbreak, roughly 30-40% of the population
3. 1860- started in China and spread throughout the world
Currently, about 10 cases per year reported in the US, concentrated in the Western States
Factors promoting spread of the plague "black death"
Y. pestis is endemic in rats
Some rats immune to disease, some are not
Describe the mechanism for Bubonic Plague Spread by the flea
1. Flea feeds on rats
2. Fleas feeding on infected host get midgut obstructions due to Y. pestis
3. These fleas begin to starve and become aggressive; attempt to feed on anything and regurgitate large quantities of bacteria into new host
4. When the rats not immune to the disease died, the fleas would sometimes feed on humans, creating accidental hosts and spreading plague
Gram ______ bipolar staining bacillus
Yersinia is anaerobic
What are the virulence factors of yersinia
1. Plasminogen activator- bacterial surface protein important for survival in fleas, responsible for the bolus of blood ( see later slide)
2. Pesticin-promotes iron uptake for Y pestis
3. Lipopolysaccaride Endotoxin-promotes cytokine cascade
Plasminogen activator in yersinia does what?
bacterial surface protein important for survival in fleas, responsible for the bolus of blood
Pesticin in yersinia does what?
Promotes iron uptake for Y pestis
Lipopolysaccaride Endotoxin in Yersinia does what?
Promotes cytokine cascade
Reservoirs for Yersinia
- Primarily rodents (urban and domestic rats)
- Also squirrels, mice, and prairie dogs
- Less common cats, dogs, rabbits
Transmission of Yersinia occurs via (2)
- Flea bites (more commonly)
- Inhalation of infected respiratory specimens of infected humans or cats
Blocked flea model of plague
1. Flea feeds on bacteremic host
2. Y. pestis colonizes flea midgut, replicates, and creates a blockage of the flea intestine as seen in previous image
3. Flea starves and becomes aggressive
4. As flea rapidly feeds, it regurgitates into the wounds and infects subsequent hosts
Y. pestis then travels up to the lymphatics then eventually into the blood stream
- Plague maintained at steady level in rodent populations
- Low death rates
- Squirrels, Chipmunks, Mice, Rabbits affected
- Large die-offs, fleas change hosts
- Amplifying hosts: prairie dogs, ground squirrels, rock squirrels, woodrats, chipmunks (vectors that reach blood levels of the organism high enough to infect other fleas)
- Expansion into human occupied areas
Amplifying hosts for sylvatic plague are
prairie dogs, ground squirrels, rock squirrels, woodrats, chipmunks
-Infected fleas or rodents move to urban area
-Increased number and areas of western U.S. cities: suburban-wilderness zone
- Commensal (domestic) rodents (Roof rat, Norway rat
....Rat fleas may feed on humans)
- Poverty, lack of sanitation, homelessness contribute
Three Types of Clinical Plague
Bubonic Plague Symptoms
- Incubation period of 1-7 days
- Sudden onset
(Fevers >38, malaise, myalgia, dizziness, painful lymphadenopathy near the site of the bite
Bubo = tender swollen lymph node with boggy consistency and hard core upon palpation
Exquisitely tender without fluctuance)
- If untreated, it can progress to septicemia
Primary Septicemic Plague clinical presentation
- Gram negative septicemia without plague symptoms/buboes
-Patients appear extraordinarily ill and febrile without localizing symptoms
- Calculated using SOFA (Sequential Organ Failure Assessment) score paired with unstable vital signs
Clinical syndrome of life threatening organ dysfunction due to dysregulated immune response to infection
Pneumonic Plague symptoms
1. Short incubation period after exposure, averaging a few hours to 3 days
2. Sudden onset of fever, and nonspecific signs such as headache, myalgia, and vomiting
3. Respiratory manifestations (Cough, chest pain, sputum production with hemoptysis)
4. Untreated has 100% mortality, treated has 50% mortality
5. Has been associated with sick domestic cats transmitting vial aerosol droplets to their owners
6. Only form of plague that can be transmitted from person to person
Which plague has 100% mortality if untreated
Which plague is assocaited with sick cats
Pneumonic Plague clinical manifestations
1. Secondary complications
2. Pneumonic Plague- Infection reaches the lungs by hematogenous spread of bacteria from the bubo, Highly contagious, patchy infiltrates on x-ray, Sputum can be purulent with high counts of bacilli
3. Meningitis-A rare complication
(Occur more than 1 week after partially treated bubonic plague. Assoc. with disease high involvement)
How many cases of plague in the uS do we get each year? Which type? Where? What time of year?
Bubonic plague = 85% of the cases
Most prevalent in “Four Corner” States
Typically in summer
The fleas live on prairie dogs, which live in the area and are social animals
Which plague is thought to have arisen from infective flea bites?
Bubonic (primary lymphadenitis)
Which plague is associated with happening often after handling infected animal tissues
Primary septicemic plague
Which plage is associated with exposure to sick cats?
Primary pneumonic plague
Plague in California occurs where?
- Occurs in foothills, plateaus, mountains, and coasts
- Absent from southeastern desert and Central Valley
What happened with the Yosemite camp outbreak?
1. 2015, 2 cases of plague
2. Last had been seen in 1959
3. Dead squirrels found
4. Dusted rat burrows with flea medications
Diagnosing Plague (4 things to look for)
1. The symptoms are very non specific so it requires high clinical suspicion for modern diagnosis
2. The presence of fever in a person with either known contact with dead rodents or residence or travel to a plague-endemic region.
3. The presence of fever, hypotension, and unexplained regional lymphadenitis.
4. The presence of clinical findings of pneumonia in association with hemoptysis and sputum containing gram-negative rods on Gram stain.
Diagnosis of plague
1. Smear and culture of buboes aspirate or blood smears
- Look for the coccobacilli (1-2um in length)
- Wayson’s stain-appears as light blue bacilli with dark blue polar bodies
- Classic “safety pin” appearance
- Culture on blood or MacConkey media
2. Specific tests have been developed for the F1 antigen with 100% specificity and sensitivity
The coccobacilli are _____um in length.
Color of stain?
1-2um in length
Light blue with dark dlue polar body
Classic "Safety pin"
What antigen are they looking for when testing for plague?
The F1 antigen with 100% specificity and sensitivity
Untreated plague has a mortality rate of > ________
Untreated Pneumonic plague = _________-
Bubonic plague has a mortality rate of ______ percent if untreated ___________ if treated.
50 to 90% untreated
10 to 20% if treated
Treatment of choice for plague
(Tetracycline or doxycycline are oral options)
Oral options for treating plague
Tetracycline or doxycycline are oral options
Plague in Madagascar
- The most severely affected country in the world
- In 2015, there were 275 cases with 63 fatalities
- One significant outbreak started in 2014
- Currently undergoing an outbreak
The most severely affected country in the world for plague is
What is the flea species affecting Madagascar
What is the rat species affecting Madagascar
_______ infesting black rats is the most common reservoir in Madagascar
Number of reasons for spread of plague in Madagascar
1. Political instability (Coup in 2009 resulted in declining foreign aid and inability of local and national governments to work together)
2. Flooding (Flushed rats out into the open)
3, Infrastructure (Numerous slums in the capital city with no services, overcrowded prisons filled with rats)
4. Villagers tend to keep animals inside with them to prevent theft (Exposes to fleas)
5. Traditions (Bodies infected with plague should be buried immediately and sealed... Famadihana “the turning of the bones”)
Famidihana in Madagascar
Called “the turning of the bones”
1. Wisdom of ancestors is revered in Madagascar culture
2. Refers to a ritual where bodies are unearthed every 5-7 years to be rewrapped in silk
3. Given these factors, the bodies of plague victims are often unearthed by the family and snuck back to villages, exposing many to plague
4. Concrete graves have been made to discourage this
Onsets of plague cases during these ceremonies (famidihana) have been observed, suggesting that handling of potentially plague-infected corpses may reactivate the disease.
Onsets of plague cases during these ceremonies have been observed, suggesting that handling of potentially plague-infected corpses may reactivate the disease.
The Ministry of Health therefore recommended respecting a seven-year period between death and exhumation of a plague victim, and before any transfer of a corpse from one village to another.
Studies have been performed to determine the survival time of Y. pestis in corpses.
No studies done
Plague is endemic on the Plateau of Madagascar, including Ankazobe District, where the current outbreak originated
- A seasonal upsurge, predominantly of the bubonic form, usually occurs yearly between September and April.
Which countries are at risk for plague?
- South Africa
There is a vaccine to prevent plague
But travelers can take steps to prevent plague, and plague can be prevented with antibiotics
What are some CDC recommendations ofr people traveling to Madagascar?
1. Use EPA-registered insect repellent that lists protection against fleas on the label and contains at least 25% DEET.
2. Avoid close contact with sick or dead animals.
3. Avoid close contact with seriously ill people, especially people who are coughing up blood.
R. typhi occurs everywhere but what continent?
R. typhi is linked to ______ and _____
rats and rat flea (Xenopsylla cheopis)
R. typhi recently been linked to ______in southern California and new vector cat flea
R. typhi is caused by ________
Caused by Rickettsia typhi
Referred as “endemic typhus” or “flea borne typhus”
Rickettsia typhi is a ________ gram _________________
Small gram negative obligate intracellular bacterium
Typhus is transmitted person to person
Rickettsiales order divided into 3 families
Rickettsia genus has 24 recognized species
How is typhus transmitted? And when do we see most cases?
- Disease is transmitted after the inoculation of infected flea feces into a pruritic flea bite wound
- Can also infect the reproductive organs of fleas, allowing for transmission of the bacterium to future flea population transovarially
- Cases occur year around with a peak during summer and early Fall
Rat flea does not routinely bite humans but will do so in the absence of their normal hosts
The typical cycle of R. typhi involves the_____ and _____rats and the rat flea (Xenopsylla cheopis).
roof and Norway rats
Presence of R. typhi shorten life span of the flea
Presence of R. typhi does not shorten life span of the flea
This rat-flea-rat cycle remains the major route of infection throughout the world
Describe the number of cases for typhus 1913-1940, 1945, now?
- 1913 to 1940 more than 5000 cases a year
- 1945 campagin to control rats and fleas drop it to 100 a year
- Currently most in Texas and SoCal less than 100 a year
LA county accounts for 42-90% of cases of typhus in the state
Clinical manifestation of typhus
- Can mimic long list of infectious etiologies (Many clinicians do not suspect this disease)
- Bacteria infect endothelial cells lining vessel walls
(Causing vascular inflammation. Fatal cases are attributed to end organ failure due to vasculitis)
-. Clinical manifestations range from mild to fatal
Mild symptoms are non-specific, constitutional
Case fatality rate is 1% (with abx)-4% (w/o abx)
- Incubation period is 1-2 weeks before onset of illness
- Initial presentation is nonspecific
- Rash (macular, petechiae, usually on ches)
- Neurological (confusion, seizure, stupor, ataxia)
Diagnosis of typhus
- Difficult to diagnose given similarities to other clinical syndromes
- No reliable lab tests for early acute phase of disease
- Rickettsial cultures of blood, skin biopsy with direct fluorescent antibody staining, and polymerase chain reaction have been used to diagnose murine typhus
- The mainstay of diagnosis is the indirect fluorescent antibody test (Positive when the antibody titer rise between acute and convalescent serum samples )
- Usually diagnosed after the empiric treatment has been started
Treatment of typhus
- Doxycycline is usually first line, empiric treatment (There is a usually a rapid clinical response)
- Quinolones are moderately active as are tetracyclines
- Many patients recover without treatment, over a 15 day period
- Preferred treatment is doxycycline for 7-15 days
Prevention of typhus
- Cornerstone of prevention is control of flea and mammalian reservoirs
- Foliage in the yard trimmed to reduce harboring rodents, opossums etc..
- Food sources should be contained to avoid attracting animals to residence
Epidemic Typhus is caused by? Transmitted by?
Caused by R. prowazekii
Transmitted by lice
Epidemic Typhus is caused by rickettsia typhi
Caused by R. prowazekii
Epidemiology of Epidemic Typhus
- Transmitted by human head and human body louse
- Humans thought to be the primary vector but recent studies have shown that R. prowazekii also lives in squirrels
- Disease is worldwide
- Lice die within 2 weeks of infection preventing transovarian infection
Tunga penetrans is distributed in __________ regions of the world
tropical and subtropical
including Mexico to South America (endemic), the West Indies and Africa (introduced)
Tungiasis fleas usually are where? Associated with what animals?
The fleas normally occur in sandy climates, including beaches, stables and farms
Associated strongly with stray dogs > cats
- Foot pain
- Difficulty walking
- Toenail loss
- Foot abscesses
- Deformed toes
(1) insecticide treatment of flea-infested domestic and stray animals and pets with 10% pyrethrin or pyrethroid sprays or 1% to 4% malathion powder
(2) bathing the feet of domestic and stray dogs and pigs with insecticide solutions, such as 2% trichlorfon
(3) spraying or dusting households, especially those with dirt floors, with 1% to 4% malathion
Extracting all embedded fleas immediately with sterile needles or curets
- Treat secondary bacterial infections
- Administer tetanus prophylaxis (Tungiasis has been associated with lethal tetanus in nonvaccinated individuals and was identified as the place of entry for 10% of tetanus cases in São Paulo in a 1991 study)