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51 Cards in this Set
- Front
- Back
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What was Rocky Mountain Spotted Fever called when it was first discovered?
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Black measles
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What is Rickettsia?
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It is a huge group of bacteria that are all geographically organized and spread by ticks, fleas, lice, and chiggers.
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What is Ehrlichia and Anaplasma?
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These are similar bacteria that cause a disease involving human monocytes and a disease involving human granulocytes. This organism is spread by ticks.
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What is Coxiella?
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This bacteria causes Q fever which can result in a variety of symptoms depending on how the bacteria was required. It is spread by ticks and aerosol ingestion.
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What do Rickettsia, Ehrlichia, Anaplasma, and Coxiella all have in common?
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They are all tiny, obligate intracellular bacteria that MUST live inside cells. They are also ALL geographically organized. The diseases caused by all of these organisms are treated empirically because of how hard lab diagnosis is (the lab diagnosis comes later)
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What are some characteristics of Rickettsiae?
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Rickettsiae are small bacteria that cannot be seen with a microscope. They are transmitted by blood-sucking insects. They can import host cell ATP and proteins or generate their own ATP and proteins. They are obligate intracellular parasites that can ONLY be grown in animals, cell culture or eggs.
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Where do Rickettsia rickettsii bacteria replicate in the host cell?
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Nucleus- only the spotted fever group of Rickettsiae replicate here
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What is the intracellular mechanism used by Ricketsia?
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They move via polymerization of an actin tail (same as listeria and shigella). They use this tail to propel into adjacent cells and to propel out of the cell and utilize the host actin to generate it. The one species that only produces a small tail or no tail at all is Rickettsia typhi.
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What is the pathogenicity of Rickettsiae?
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It infects endothelial cells and the amount of damage depends on the number of intracellular bacteria. Once inside the endothelial cells the bacteria produce free radicals that can damage the endothelial membrane. It causes the vascular vessels to leak which activates a coagulation cascade. This results in the occlusion of the vascular vessels and hemorrhage which appears clinically as petechiae (red spots). Inside the endothelial the bacteria can move from cell to cell within the cells (it never has to exit the cell but can burst through 1 cell's membrane to get into another cell). This intracellular spreading is critical in the organisms ability to infect a large part of small vascular vessels.
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What are some of the symptoms of Rocky Mountain Spotted Fever?
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You start with a fever and then a rash that involves the palms and soles (same as syphilis). The fever is ALWAYS present at high levels. A headache occurs in most cases along with the rash. There is usually a history of a tick bite (these ticks are adults ticks and thus much larger so you feel when they bite you).
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What are some of the outcomes of Rocky Mountain Spotted Fever?
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It may cause encephalitis with a CNS endothelial infection and CSF pleocytosis (rise in the WBC count). It can also cause mortality in both untreated and treated situations.
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What is the triad of symptoms that tells you that you are dealing with Rocky Mountain Spotted Fever?
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Fever
Rash Tick bite However this triad only occurs in 1/3 of people that are suffering from Rocky Mountain Spotted Fever |
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What is the reservoir and vector for Rocky Mountain Spotted Fever?
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The reservoir is small mammals such as rodents and ticks. The vector is ticks. This disease is found ALL over the Eastern half of the US.
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How is R. rickettsiae maintained in ticks?
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Ticks are both reservoirs and vectors of this bacteria because they can transmit it to their progeny via their eggs (transovarial transmission).
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In what part of the US is Rocky Mountain Spotted Fever most common?
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It is the most common in the Eastern part of the US; esp. the central Eastern part of the US.
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What are the trends seen in terms of prevalence and death rate associated with Rocky Mountain Spotted Fever?
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There are mini epidemics of Rocky Mountain Spotted Fever that occur every 10-20 years. The death rate has decreased since the 1950s when physicians discovered the disease and began to treat it empirically.
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How do you diagnose Rocky Mountain Spotted Fever?
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Clinically!!- you look for the triad
Serology is NOT timely or helpful- it is only positive after 7-10 days of the infection and the patient could be dead at this point Immunohistopathology can be used with this rash and it is a VERY specific and sensitive test. PCR (not super common though) and Culture |
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How do you treat Rocky Mountain Spotted Fever?
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Empirically!
Antibiotic therapy is used with doxycycline being the drug of choice (or other tetracyclines). Beta-lactams and aminoglycosides CANNOT get into the bacteria so they will fail Sulfonamides can make Rickettsial infection WORSE |
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How long does it take to progress from the fever to the rash with Rocky Mountain Spotted Fever?
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About 3 days
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What 3 bacteria are a part of the Spotted Fever Group of Rickettsiae?
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R. rickettsii
R. conorii R. africae |
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What disease does R. rickettsii cause and what is the reservoir, transmission and geographic distribution?
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R. rickettsii causes Rocky Mountain Spotted Fever. It's reservoir is ticks and it is transmitted through a tick bite. It is found in North and South America.
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What disease does R. conorii cause and what is the reservoir, transmission and geographic distribution?
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R. conorii causes Boutonneuse fever. It's reservoir is ticks and it is transmitted through a tick bite. It is found in Southern Europe and Northern Africa.
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What disease does R. africae cause and what is the reservoir, transmission and geographic distribution?
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R. africae causes African tick bite fever (a much milder disease). It's reservoir are domestic and wild mammals and it is transmitted by a tick bite. It is found in Southern Africa.
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What are the 3 types of typhus that can be caused by Rickettsiae bacteria?
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Epidemic Typhus
Endemic Typhus Scrub Typhus |
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What bacteria causes Epidemic Typhus, what transmits it, what is its reservoir, what situations is it associated with and what symptoms does it cause?
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Epidemic Typhus is caused by R. prowazekii. It occurs in situations of war, famine, refugee situations etc... and thus can be found worldwide. It is transmitted by human lice feces and thus is only transmitted in destitute situations. Its reservoirs are humans and flying squirrels in the US. Humans can be asymptomatic and thus propagate the infection between outbreaks. It causes petechial rash and fever (similar to Rocky Mountain Spotted Fever). It can also cause Brill-Zinsser Disease (latent typhus that can result in periodic symptoms and last for decades).
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What bacteria causes Endemic Typhus, what transmits it, what is its reservoir, what situations is it associated with and what symptoms does it cause?
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Endemic Typhus is caused by R. typhi. It is a milder and self-limited disease compared to Rocky Mountain Spotted Fever or epidemic typhus. It's reservoir is rodents (and fleas) and it is transmitted through flea feces. It causes a nondescript fever and RASH. It is hard to diagnose and is usually not fatal. It occurs in places where they are lots of rats and mice and thus can be found world-wide, esp. in the tropics and subtropics.
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What bacteria causes Scrub Typhus, what transmits it, what is its reservoir, what situations is it associated with and what symptoms does it cause?
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Scrub typhus is a COMMON disease that is caused by Orientia tsutsugamushi. It causes undifferentiated fever in SE Asia. It is also common in military campaigns. It DOES NOT usually cause a rash. It's vector is a chigger (blood-sucking insect) and it's vector is the chigger as well (it is transmitted transovarianly to progeny). It is VERY hard to diagnose.
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What are some KEY clinical aspects of Ehrlichia chaffeensis infection?
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It causes a LOW WBC count (ex=800), the individual will recall multiple tick bites, it DOES NOT cause a rash and it causes platelets to be decreased (ex= 67,000).
A patient presenting with these symptoms would be treated with broad spectrum antibiotics (such as IV piperacillin and gentamicin) until the knowledge of the multiple tick bites which would lead to the addition of doxycycline (the other 2 drugs are stopped as well). Cultures, chest xrays, and abdominal xrays would show up negative. |
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What happens to WBC count when you treat an Ehrlichia chaffeensis infection with doxycycline?
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The WBC count increases.
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What is Ehrlichia chaffeensis, what is its vector, where is it distributed in the US and what is the treatment for it?
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This is the bacteria that causes Human Monocytic Ehrlichiosis. It is a common bacteria that infects monocytes. You cannot visualize the bacteria in teh cells but they grow within the vacuoles/granules of the cell and you can sometimes see inclusions of them. They can also be seen on EM.
Its vector is the Lone Star Tick. It is found in Mississippi valley and the Southern part of the US. It is treated with doxycycline. |
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What is Anaplasma phagocytophilum, what is its vector, where is it distributed in the US and what is the treatment for it?
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Anaplasma phagocytophilum is the bacteria that causes Human Granulocytic Ehrlichiosis. It infects granulocytes. It's vector is the Ixodes tick. It is found in the Northeast and North Central US (it has the same distribution as Lyme disease). It is treated with doxycycline.
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What is the relationship between the density of cases of disease and the presence of ticks?
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These two factors are DIRECTLY related. The highest density of cases are found where the ticks reside.
Monocytic Ehrlichiosis incidence is found in the US in the same area as Rocky Mountain Spotted Fever since both diseases are transmitted by the same tick. They are found in the mid-southern part of the US. Granulocytic ehrlichiosis incidence is greatest in the areas where you find lyme disease. The distribution of the tick determines the distribution of the disease. Geography of where the patient has been can change your differential diagnosis. |
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What is another name for Granulocytic ehrlichiosis?
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Anaplasmosis
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What are some features of Monocytic ehrlichiosis and Anaplasmosis (Granulocytic ehrlichiosis)?
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They occur from April to September with peaks in June and July. A tick bite history is common (they are both transmitted by adult ticks so you feel the tick bite). Males are at a higher risk of the disease than females. The Type IV secretion system of the bacteria mediates the interruption of the phagolysosome fusion which allows the bacteria to survive within cells. 2/3 of patients require hospitalization. The Monocytic ehrlichiosis is more serve than Anaplasmosis.
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What is key if you are bitten by a tick?
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GET IT OFF FAST so that you reduce the risk of disease transmission.
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What are some similarities between Ehrlichiosis and Rocky Mountain Spotted Fever?
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They both include a history of a tick bite, the diseases are geographically based on the tick distribution, they have similar symptoms (such as fever), they elevate liver enzymes, they cause thrombocytopenia and they both can be treated with tetracyclines.
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What are 2 key differences between Ehrlichiosis and Rocky Mountain Spotted Fever?
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There is a petechial rash in Rocky Mountain Spotted Fever and rickettsiae spotted fevers. There is Leukopenia and NO rash in ehrlichiosis.
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What is the host cell of Rickettsia and where within the cell does it replicate?
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Rickettsia infects endothelial cells and replicates in the nucleus. Rickettsiae ricketsii (which causes Rocky Mountain Spotted Fever) replicates in the nucleus.
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What is the host cell of Coxiella and where within the cell does it replicate?
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Coxiella (which causes Q fever) infects macrophages and replicates in the phagolysosomes.
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What is the host cell of Ehrlichia and where within the cell does it replicate?
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Ehrlichia infects monocytes and PMNs and replicate within intracytoplasmic vacuoles.
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What are some KEY components of a case of Monocytic Ehrlichiosis?
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The patient has been on a camping trip to the Smoky Mountains recently and the patient presented with fever, headache, malaise, and NO rash. The patient had a decreased WBC and platelets and increased hepatic enzymes. Finally, the patient was bitten by a tick.
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What are some KEY components of a case of African Rickettsia spotted fever?
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The patient presented with a fever and flu symptoms after returning from South Africa. He was working near a dam. He had crusty spots on his body that were not painful or tender. Someone else on the trip was experiencing a fever. He had a fever. Doxycycline cleared up the disease.
This illness was acquired through tick bites which are the scabs/ crusty spots on the patient. |
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What are eschars?
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They are usually cause by ticks attaching and biting you.
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What are some main differences between the symptoms seen with Rocky Mountain Spotted Fever and African Spotted Fever?
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African Spotted fever does not always include a fever and is MUCH less likely to include a rash. If the patient does present with a rash it is vesicular-looking (similar to chickenpox). There is less history of a tick bite and the symptoms triad is rare. Mortality is also rare with untreated African Spotted Fever (there is a high rate of mortality if Rocky Mountain Spotted Fever goes untreated). Eschars are common in African Spotted fever whereas they are VERY RARE with Rocky Mountain Spotted Fever.
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What are some of the characteristics of Coxiella burnetii?
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Coxiella burnetii is a small, pleomorphic coccobacillus. It can form a spore-like structure that is able to withstand harsh environmental conditions. It causes Q fever which is NOT very common.
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What type of bacteria is Coxiella burnetii and how is it transmitted to humans?
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Coxiella burnetii is an obligate intracellular bacteria that is taken up passively into cells and survives in the phagolysosomes of the cells. It is transmitted via the air (it is inhaled). Only 1 organism is needed to cause disease (IT IS VERY CONTAGIOUS). It can enter the lung and the proliferate in the lung, liver, spleen, lymph nodes, etc... It is a reticuloendothelial disease.
It can be transmitted via aerosolization, tick bite or through ingestion. |
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What are the animal sources of Coxiella and what are its vectors?
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Its reservoirs are cattle, sheep, goats, etc... as well as house cats. It can be transmitted among animals through ticks and from animals to humans via ticks. The infected animals appear healthy. This bacteria is often aerosolized when the infected animal gives birth (Coxiella lives in the placenta of the animals). It has also been found in raw milk.
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What can Coxiella infection cause?
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It can cause Q fever which presents as a self-limited flu like illness. It can results in atypical pneumonia. It can also result in endocarditis (but you cannot culture the organism) and hepatitis.
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Can you culture Coxiella?
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NO, you will never be able to grow this organism on a blood culture plate.
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How do you treat Q fever?
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Doxycycline
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How do you diagnose Q fever?
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Serology
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