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Microbiology > Unit 4 - The Order Rickettsiales > Flashcards

Unit 4 - The Order Rickettsiales Flashcards

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1
Q

What is the morphology of organisms in the order Rickettsiales?

A

rod shaped, coccoid, and often pleomorphic

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2
Q

Are organisms in the order Rickettsiales gram negative or positive?

A

gram negative - but stain poorly

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3
Q

What stains help visualize organisms in the order Rickettsiales?

A

Giemsa, Macchiavello, and Gimenez stains

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4
Q

What type of organisms are Rickettsiales?

A

obligate intracellular parasites

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5
Q

How do Rickettsiae enter the host cell?

A

by parasite-induced phagocytosis

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6
Q

How do Rickettsiae escape digestion?

A

in the phagolysosome by either escaping into the cytoplasm or remaining in the phagocytic vacuole and resisting digestion

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7
Q

How do rickettsiae multiply?

A

by binary fission

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8
Q

How are rickettsiae released?

A

by cell lysis or exocytosis

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9
Q

What organisms in the family Rickettsiaceae associated with?

A

nucleated host cells

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10
Q

What genera are included in the tribe Rickettsieae?

A

those that are pathogenic primarily for humans

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11
Q

When released from cells, what can the bacteria in the tribe Rickettsieae do?

A

infect vertebrate hosts when the vectors obtain a blood meal

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12
Q

What are the three distinct biotypes of the genus Rickettsia?

A

Typhus group (A), Scrub Typhus group (B), and Spotted fever group ©

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13
Q

What are two species belong in the typhus group?

A

Rickettsia prowazekii and Rickettsia typhi

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14
Q

What does Rickettsia prowazekii the cause of?

A

epidemic typhus - a louse-borne disease seen in conditions of war, poverty, and famine

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15
Q

How does clinical disease from Rickettsia prowazekii progress?

A

headache, fever, skin rash, and if untreated death

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16
Q

Is there an animal intermediate host for Rickettsia prowazekii?

A

no

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17
Q

What does Rickettsia typhi cause?

A

mouse typhus

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18
Q

How do humans get mouse typhus?

A

by accidental exposure to the rat flea or louse

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19
Q

What species belongs in the scrub typhus group?

A

Rickettsia tsutsugamushi

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20
Q

What does Rickettsia tsutsugamushi cause?

A

srub typhus or chigger-borne typhus

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21
Q

What are the vectors for Rickettsia tsutsugamushi?

A

mite larvae or chiggers

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22
Q

What species belings in the spotted fever group?

A

Rickettsia rickettsii

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23
Q

What does Rickettsia rickettsii cause?

A

Rocky-Mountain spotted fever

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24
Q

What transmits Rickettsia rickettsii?

A

ticks

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25
Q

What ticks are important vectors for Rickettsia rickettsii?

A

The Rocky mountain wood tick and the american dog tick

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26
Q

What serves as carriers of infected ticks for dogs and humans?

A

dogs

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27
Q

What is happens after Rickettsia rickettsii invades the body?

A

After gaining access to the body through a tick bite, the rickettsiae invade vascular endothelium causing widespread endothelial damage

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28
Q

What results from the endothelial damage that Rickettsia rickettsii does?

A

occlusion of small vessels, microthrombi, microhemorrhages, vasculitis, and in severe cases necrosis, shock, and death

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29
Q

When do clinical signs from a Rickettsia rickettsii infection typically appear?

A

2-3 days after a tick bite

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30
Q

What clinical signs are associated with Rickettsia rickettsii infections?

A

anorexia, fever, vomiting, diarrhea, depression, and petechial hemorrhages on the skin, mucous membranes, and retina

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31
Q

What are the most consistant causes of death associated with Rickettsia rickettsii infection?

A

cardiovascular, neurologic, and renal complications

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32
Q

What is the most common way to diagnose a Rickettsia rickettsii infection?

A

indirect FA

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33
Q

What other ways can you test for Rickettsia rickettsii infection?

A

PCR and immunohistochemical staining (post-mortem)

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34
Q

What treatment can be used for a Rickettsia rickettsii infection?

A

early treatment with tetracycline

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35
Q

When is transmission from dogs to humans of Rickettsia rickettsii assumed to occur?

A

when removing ticks from the dog

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36
Q

What genera are of importance in the family Anaplasmataceae?

A

Ehrlichia, Neorickettsia, and Anaplasma

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37
Q

What do organisms in the genus Ehrlichia infect?

A

circulating leukocytes but some can infect vascular endothelial cells

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38
Q

What are the vectors for Ehrlichia?

A

ticks

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39
Q

What does Ehrlichia ruminantium cause?

A

heartwater disease in ruminants

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40
Q

Where is heartwater disease an economically important disease?

A

in Africa and the Caribbean

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41
Q

What type of cells does Ehrlichia ruminantium prefer to infect?

A

vascular endothelial cells

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42
Q

What clinical signs are associated with an Ehrlichia ruminantium infection?

A

high fever, depression, anorexia, and neurologic signs

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43
Q

What is a common lesion associated with an Ehrlichia ruminantium infection?

A

hydropericardium

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44
Q

What do Ehrlichia bovis and Ehrlichia ovina cause?

A

a tick-borne disease that causes a fever of several weeks duration in bovine and ovine in Africa

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45
Q

What does Ehrlichia canis cause?

A

canine ehrlichiosis

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46
Q

Where is Ehrlichia canis prevalent?

A

in tropical and subtropical areas

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47
Q

What cells does Ehrlichia canis infect?

A

only circulating leukocytes

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48
Q

What is the life cycle of Ehrlichia canis?

A

It enters the leukocyte cytoplasm where it divides inside a membrane-bound vesicle to form a morula. Organisms leave the cell when the cell ruptures or by exocytosis

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49
Q

What is the primary reservoir for Ehrlichia canis?

A

the brown dog tick

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50
Q

What are the three stages of Ehrlichia canis infection?

A

acute, subclinical, and chronic

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51
Q

How long does the acute phase of Ehrlichia canis last?

A

2-4 weeks

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52
Q

What occurs during the acute phase of an Ehrlichia canis infection?

A

The organism multiplies in mononuclear cells which spread to tissues throughout the body. In these tissues, the mononuclear cells attach to the endothelium and produce a vasculitis or cause an inflammatory response as they migrate into the subendothelial tissue

53
Q

What is a common finding with the acute phase of Ehrlichia canis infection?

A

thrombocytopenia and severe vasculitis which may result in disseminated intravascular coagulation and death

54
Q

How long does the subclinical phase of an Ehrlichia canis infection last?

A

40-120 days after acute infection

55
Q

What happens during the subclinical phase of an Ehrlichia canis infection and what does it cause?

A

Organisms persist and dogs can have thrombocytopenia, leukopenia, and anemia

56
Q

If the infected dog is immunocompetent, what occurs after the subclinical phase of an Ehrlichia canis infection?

A

they can eliminate it - it is the last stage

57
Q

What does the severity of the chronic phase of Ehrlichia canis depend on?

A

the strain variation, concurrent disease, and age

58
Q

What breed is especially susceptible to the chronic phase of Ehrlichia canis infection and what do they get?

A

german shepards - terminal pancytopenia

59
Q

True or False: Once an animal is infected with Ehrlichia they are immune to it.

A

False - Only if the animal still harbors the organism it is immune to reinfection, but if the organism is cleared then reinfection can occur

60
Q

How is Ehrlichia canis infection diagnosed?

A

indirect fluorescent antibody test

61
Q

How is Ehrlichia canis infection treated?

A

with tetracyclines

62
Q

What does Neorickettsia risticii cause?

A

Potomac horse fever or equine monocytic ehrlichiosis

63
Q

What time of year does Potomac horse fever typically present?

A

in the summer months

64
Q

What cells does Neorickettsia risticii infect?

A

macrophages, mast cells, and epithelial cells of the intestinal tract as well as circulating monocytes

65
Q

True or False: Neorickettsia risticii is the only rickettsial organism that grows in the intestinal epithelium of mammals.

A

TRUE

66
Q

What carries Neorickettsia risticii?

A

a trematode that parasitizes snails, aquatic flies, and bat intestines

67
Q

How do horses become infected with Neorickettsia risticii?

A

they eat or drink the fluke itself or the equatic insects, they ingest feces from bats or barn swallows that ate the organism, eat feces from infected horses, or direct transfer of blood

68
Q

What is the major manifestation of Neorickettsia risticii?

A

gastrointestinal disease

69
Q

How does acute onset of Neorickettsia risticii present?

A

as a sudden onset of depression, anorexia, colitis, laminitis, and fever with diarrhea starting 1-3 days after onset of clinical signs

70
Q

How does subacute disease of Neorickettsia risticii present?

A

depression, anorexia, and fever but no diarrhea

71
Q

How is the mild or inapparent form of Neorickettsia risticii diagnosed?

A

by seroligic studies

72
Q

In general how is a Neorickettsia risticii diagnosed?

A

PCR on feces

73
Q

How is a Neorickettsia risticii treated?

A

intravenous fluids and oxytetracycline - but it needs to be diagnosed as soon as possible

74
Q

Is there an immunization for Neorickettsia risticii?

A

yes - there is a killed bacterin but due to different serologic variants it does not always confir protection

75
Q

What does Neorickettsia helminthoeca cause?

A

salmon poisoning disease

76
Q

Where is salmon poisoning disease prevalent?

A

from northwestern California to southwestern Washington

77
Q

What cells does Neorickettsia helminthoeca typically infect?

A

cells of the mononuclear phagocytic system

78
Q

What is the vector of Neorickettsia helminthoeca?

A

the trematode Nanophyetus salmincola

79
Q

What hosts are required for complesion of the life-cycle of Nanophyetus salmincola?

A

snails, fish, and mammals or birds

80
Q

What is the pathogenesis of Neorickettsia helminthoeca infection?

A
  1. Dogs ingest raw fish containing metacercariae 2. The fluke matures and attaches to the intestinal mucosa and somehow injects the rickettsiae 3. The rickettsiae enter the blood and spread throughout the body
81
Q

What pathological findings are associated with Neorickettsia helminthoeca infection?

A

changes in the lymphoid tissue with edema, hemorrhage, and necrosis - there may be a meningitis or meningoencephalitis

82
Q

What clinical signs are associated with Neorickettsia helminthoeca infections?

A

first sign is sudden fever then anorexia, vomiting, diarrhea, and enlarged lymph nodes

83
Q

How is Neorickettsia helminthoeca infection diagnosed?

A

trematode eggs in the feces with fluid aspirated from enlarged lymph nodes to observe intracytoplasmic organism

84
Q

How is Neorickettsia helminthoeca infection treated?

A

sulfonamides, penicillin, tetracycline, and chloramphenicol - fluid therapy to control vomitting and diarrhea

85
Q

What does Neorickettsia elokominica known as?

A

the Elokomin fluke fever agent

86
Q

What does Neorickettsia elokominica cause?

A

a disease similar to salmon poisoning disease but not as severe

87
Q

Where are organisms in the genus anaplasma found?

A

within or on erythrocytes or free in the plasma of ruminants

88
Q

How are organisms in the genus Anaplasma transmitted?

A

by any route whereby blood is transmitted including by arthropods, needles, surgical instruments etc.

89
Q

What is the most priminent clinical sign associated with the genus Anaplasma?

A

anemia

90
Q

What is the pathogenesis of organisms in the genus Anaplasma forming an inclusion?

A

the organisms or initial bodies enter erythrocytes by invagination of the cytoplasmic membrane and formation of a vacuole. They multiply by binarry fission and form an inclusion

91
Q

What is the most pathogenic Anaplasma species to cattle?

A

Anaplasma marginale

92
Q

What age of cattle are typically affected by Anaplasma marginale?

A

young adult and older cattle (mortality increases with age)- cattle less than 6 months of age are relatively resistant

93
Q

Where is Anaplasma marginale enzootic?

A

in southern states, lower plain states, and western states

94
Q

Where are Anaplasma marginale organisms located?

A

in spherical inclusions near the periphery or margin of the erythrocytes - each inclusion contains one to eight initial bodies

95
Q

What are the biological vectors of Anaplasma marginale?

A

with the pacific coast tick and the Rocky Mountain wood tick

96
Q

How is Anaplasma marginale mechanically transmitted?

A

by other ticks, horseflies, mosquitos, other biting flies, and contaminated surgical instruments and needles

97
Q

How does Anaplasma marginale cause regenerative anemia?

A

infected erythrocytes are removed by the mononuclear-phagocytic system resulting in regenerative anemia

98
Q

What general clincical signs are associated with Anaplasma marginale?

A

fever, pallor, depression, anorexia, icterus, dehydration, and tachycardia

99
Q

What are the four stages of Anaplasma marginale infection?

A

incubation stage, developmental stage, convalescent stage, and carrier stage

100
Q

How long is the incubation stage of Anaplasma marginale?

A

3-8 weeks

101
Q

What occurs during the developmental stage of Anaplasma marginale?

A

anemia develeps - the first clinical signs are noticed halfway through this stage: mortality mostly occurs in animals over 2 years of age

102
Q

What occurs during the convalescent stage of Anaplasma marginale infection?

A

the reticulocytes return to normal - few weeks to few months

103
Q

What occurs during the carrier stage of Anaplasma marginale?

A

the clinically recovered animals remain carriers with nondetectable lowe level parasitemia for life and act as reservoirs

104
Q

What is conclusive to diagnose Anaplasma marginale?

A

demonstration of the marginal bodies in erythrocytes - which can only be found in the developmental and convalescent stages

105
Q

What can be used to diagnose Anaplasma marginale in developmental, convalescent, and carrier stages?

A

serologic tests - rapid-card agglutination, CF, ELISA, competitive ELISA, and PCR testing

106
Q

How is Anaplasma marginale treated?

A

with tetracycline

107
Q

Is there a vaccine for Anaplasma marginale?

A

yes there is a killed product but it is considered experimental

108
Q

What does Anaplasma centrale produce?

A

centrally-located inclusions in the erythrocyte

109
Q

Where is Anaplasma centrale found?

A

in Europe, Africa, and Australia

110
Q

What animals does Anaplasma ovis cause disease in?

A

sheep and goats

111
Q

What does Anaplasma phagocytophilum cause?

A

human granulocytic ehrlichiosis

112
Q

Where does disease from Anaplasma phagocytophilum occur?

A

upper Midwest, East, and Northeast US as well as the West Coast - disease also occurs in northern Europe and parts of Asia and South America

113
Q

What is Anaplasma phagocytophilum transmitted by?

A

ixodid ticks

114
Q

What species does Anaplasma phagocytopilum infect?

A

dogs, cats, human, horses, ruminants, and many wildlife species

115
Q

What are considered to be the reservoir hosts for Anaplasma phagocytophilum?

A

whitetailed deer and several species of rodents

116
Q

A high seroprevalence in endemeic areas indicates that disease caused by Anaplasma phagocytophilum is often _______ or at least not severe enough to warrant diagnosis.

A

subclinical

117
Q

What vague clinical signs are associated with an Anaplasma phagocytophilum infection?

A

vague signs such as fever, lethargy, anorexia, and general muscle pain

118
Q

What is clinical disease due to Anaplasma phagocytophilum most often associated with?

A

the acute, bacteremic phase of infection and can last from one to several days

119
Q

What is the most frequent clinical sign is observed in dogs infected with Anaplasma phagocytophilum?

A

acute joint pain and lameness due to polyarthritis

120
Q

At what age is clinical disease due to Anaplasma phagocytophilum most seen in dogs?

A

dogs 8 years or older

121
Q

How is Anaplasma phagocytophilum diagnosed?

A

demonstration of morulae in WBC, ELISA, IFA, and PCR

122
Q

How is Anaplasma phagocytophilum treated?

A

clinical infection can be treated with doxycycline - tick control to prevent infection is warranted

123
Q

Is Wolbachia gram negative or positive?

A

negative

124
Q

What percentage of insects are infected with Wolbachia pipientis?

A

twenty to seventy-five percent

125
Q

How is Wolbachia pipientis most commonly transmitted?

A

from the female through the egg but horizontal transmission and cross-species transmission are also recognized

126
Q

Wolbachia pipientis is required for fertility and _____ development in nematodes and is always present in _______ ______ in dogs and cats.

A

larval; Dirofilaria immitis

127
Q

What is used to kill Wolbachia pipientis in concurrent with heartworm treatment?

A

doxycycline

128
Q

What is reproductive infection of Wolbachia pipientis in arthropods characterized by?

A

the ability of the organism to override chromosomal sexxual determination, induce pathogenesis, selectively kill males, influence sperm competition, and generate cytoplasmic incombatibility

Microbiology (50 decks)

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