Test 3- RIckettsiales Flashcards
Generals
Obligate intracellular Gram‐negative bacteria
Bacteria within arthropods
Family Anaplasmataceae
Genus Anaplasma
Survive in erythrocytes, phagocytes and platelets
Genus Ehrlichia
Survive in phagocytic cells
Genus Neorickettsia
Survive in macrophages and mononuclear cells
Family Rickettsiaceae
Rickettsiae (Survive in vascular epithelium)
Genera Rickettsia, Wolbachia, Orientia
Bacterial reclassification- Not super important
Reorganized by sequence comparison of 16S rRNA gene
α‐ Proteobacteria in the genera: Neorickettsia
Anaplasma
Ehrlichia
Genus Anaplasma
Gram negative small coccoid – ellipsoid bacteria
Live within cytoplasmic vacuoles of myeloid cells, neutrophils and erythrocytes- PROTECTS FROM IMMUNE SYSTEM
Peripheral blood or tissues of mononuclear phagocyte organs
May cause anemia, thrombocytopenia, leukopenia
Single or in morulae (bacterial packets)
Wright‐Giemsa (bluish purple)
Anaplasma marginale
Anaplasma centrale
Anaplasma ovis
Anaplasma bovis
Bovine anaplasmosis
Formerly Ehrlichia bovis Anaplasma platys
Formerly Ehrlichia platys
Anaplasma phagocytophilum
Formerly Ehrlichia phagocytophilum, E. equi and E. phagocytophila
Anaplasma marginale
Reservoir and transmission
Infected ruminants
Wild (deer) and domestic species
REPORTABLE DISEASES
All continents
Biologic transmission with hard ticks
Boophilus microplus
Boophilus, Dermacentor, Ixodes and Rhipicephalus
Mechanical transmission (less significant)
Biting flies, contaminated fomites
Contaminated instruments
Pathogenesis of Bovine Anaplasmosis
Clinical signs and pathological changes
Subclinical to peracutely fatal presentations
Mortalities of ~50% in cattle >3 years of age
Persistent infection, undulating febrile disease
Depression, anorexia, fever, anemia and icterus
Long term carriage occur
ERTHOCYTES-THUS ANEMIA
Bovine Anaplasmosis Immune Response
Immune response
Humoral and cell‐mediated response
Antigenic variation present
Msp2 gene
Related to chronicity
Antibody response is also directed to host antigens
DESTRUCTION OF ERYTHROCYTES
Immune response can be shared between other Anaplasma
Anaplasma centrale
Experimental vaccines are available but are not USDA approved
Diagnosis of Bovine Anaplasmosis
Diagnosis
Routine blood stains, acridine orange or IFA
Appear purple structures near periphery of erythrocytes in GIEMSA stains
Molecular diagnosis
Serological methods
Complement fixation, capillary agglutination, ELISA Useful in detecting subclinical cases
Treatment and control
Tetracyclines are pretty effective
Vaccination and VECTOR CONTROL
Anaplasma marginale in bovine erythocytes
Anaplasma phagocytophilum
generals
Human granulocytic anaplasmosis
Tick borne fever
Domesticated and wild ruminants
Equine granulocytic anaplasmosis
dogs and horses
Anaplasma phagocytophilium
reservior and transmission
Reservoir and transmission
Rodents and wildlife (deer)
In North America
East is mainly the white‐footed mouse and the deer tick (Ixodes
scapularis)
West is mainly the western black‐legged tick (Ixodes pacificus)
A. phagocytophilium causes, pathogenesis
Causes tick‐borne fever primarily in ruminants (EUROPE) and in horses, dogs and humans in North America
Pathogenesis associated with infection of neutrophils (primary) and eosinophils
Tick pyemia (Staphylococcus infection) is commonly linked to tick‐borne fever
Disease is mediated by the host immune response
Clinical and Pathological Findings for A. phagocytophilium
Clinically
Fever, depression, inappetance, anemia, edema, ataxia,
icterus, drop in milk yield, abortions, and leukopenia
Immunosuppressive effects
Pathological findings
Hepatitis, splenomegaly, arthritis, paracortical hyperplasia in lymph nodes
A. phagocytophilium Vaccine and immunoaspects
Immunological aspects
Antigenic variability
Major surface proteins (Msp2)
Serological cross‐reactivity
Ehrlichia spp, other Anaplasma spp
. No vaccines
Recovery with doxycycline therapy and adequate immune responses and tick control
A. phagocytophliium diagnosis
Laboratory diagnosis
In GIEMSA or Wright’s stained blood smears
Appear like membrane‐bound morulae (1‐10 bacteria) within neutrophils of ruminants, dogs, horses and humans
Has been propagated in tick and human leukemic cell cultures
Serological methods IFA, ELISA
Molecular methods PCR
A. platys
PLATLETS!
Infectious canine cyclic thrombocytopenia
Cycles of 1‐2 weeks interval
Fever, lethargy, pale mucous membranes, petechial hemorrhages, epistaxis, and lymphadenopathy
Co‐infections with Ehrlichia canis common
Reservoir and transmission
Rhipicephalus and Dermacentor ticks
Laboratory diagnosis
In GIEMSA stained blood smears
A. platys in surface of canine platelets
IFA, PCR
Rickettsiae
Small bacteria (0.5‐1 μm)
Gram‐negative bacteria
Better to stain with Gimenez (red), Macchiavello (red) or Giemsa (purple) stains
Non‐motile bacteria
Actin hijack inside cells
Pathogenesis includes
Enter endothelial cells by endocytosis
Escape from phagosome and multiply in cytoplasm and nucleus Associated with invertebrate vectors
In veterinary medicine
Rickettsia rickettsii
Rickettsia felis
Coxiella burnetii
Rocky mountain spotted fever Typhus group
Q fever
Reserviors and Transmission for Rickettsia rickettsii
Causative agent of Rocky Mountain Spotted Fever
Reservoir and transmission
Dogs and people in endemic areas
Small mammals are though to be the major reservoir
Carried naturally by ~20 species of ixodid ticks
Dermacentor andersoni (Wood tick)
Wood tick
D. variabilis (American dog tick)
Transovarial and transtadial transmission- CAN GO FROM MOTHER TO EGGS
in ticks exist
American dog tick
Mainly in Eastern North America Seasonal incidence
Pathogensis of Rickettsia rickettsii
Tick
Replicates in epithelium
Transferred to salivary glands and ovarian tissues
Vertebrate
Ticks bites injects bacteria and targets vascular endothelium
Endocytosed, escape phagosome and multiply in cell cytoplasm and nucleus
Damage of endothelial cell membranes
Rickettsial phospholipases and proteases
Necrosis, vasculitis, hemorrhages, edema, thrombosis and dyspnea
Rarely fatal but does occur
Nervous system disturbances (~80% cases in dog)
Heart and kidney involvement
Clinical Signs of Rickettsia rickettssii
Clinical signs
High fever, anorexia, vomiting, diarrhea, petechiae or ecchymotic
mucous membranes, edema
Tenderness over lymph nodes, joints and muscle
Severe necrosis in extremities in dogs occur (severe fatal disease)
Marked thrombocytopenia and leukopenia may be present during acute phase
Immunological Aspects for Rickettsia rickettssii
Immunologic aspects
Auto immune reactions are related to pathogenesis in
late RMSF vascular manifestations
Humoral and cell‐mediated response occurs
CMI most important for removal of the pathogen
No vaccines available for RMSF
Lab Diagnosis of Rickettsia rickettiiss
Culture
Can be propagated in
Yolk sacs of chick embryos
Cell culture (VERO cells, endothelial cell lines)
33‐35°C with a generation time of ~9h
Need to have glutamate as nutrient
Serological methods
Immunofluorescence and ELISA commonly used
Mainly detect circulating IgG
Negative or low titers can be present early in the diseases
Laboratory diagnosis
Molecular diagnosis- Have to bx hemorrage sites because you can’t just pull blood
PCR is now widely used and accepted Very sensitive and specific
Limitations of PCR
Treatment and Control of Ricketsia Rickettsii
Treatment and Control
Susceptible to chloramphenicol, fluoroquinolones and
tetracyclines
Dogs need aggressive supportive therapy and possibly steroids
NEED TICK CONTROL
Coxiella burnetii
Reservoir
Worldwide
Survives in environment
Different from other related rickettsiae
Have a endospore‐like growth phase
Can be disseminated by airborne route - DOES NOT NEED A VECTOR
Natural hosts and vectors include
~125 mammalian species
Arthropods
Ticks, mites, fleas, lice and flies
Environmental persistence
Transmission of Coxiella burnetti
Transmission
Human cases of Q‐fever can be traced to
Sheep, cattle and goats
Direct or via unpasteurized milk products, feces, sperm and
reproductive discharges
Wind can carry “spore like stages”
BIO‐WEAPON, REPORTABLE
In humans
Subclinical influenza like occupational diseases
Farmers, abattoir workers, veterinarians
Endocarditis in chronic presentations
Pathogenesis of C. burnetti
Mildly affected animals can have latent infection
Persist particularly in lactating mammary gland and pregnant uterus
Shedding of bacteria occurs during pregnancy
Activated during parturition
Sporadic aborts occur
Pathological changes
Severe vasculitis, placentitis, splenomegaly, mild hepatitis, fever
ENDOTHELIUM and RESPIRATORY
Immunologic Aspects of C. burnetti
Vaccine is available in some countries for at risk people
Uses the avirulent phase II
Has altered LPS and are killed by macrophages
Whole cell killed vaccine to researchers
Coxevac (France) vaccine for small ruminants
Phase I vaccine containing inactivated C. burnetii strain Nine Mile
Two antigenic phases, Phase 1 and Phase 2
Phase 2 antibodies are indicative of acute infection Antibodies to Phase 1 indicative of chronic infection
Lab Diagnosis of C. burnetti
Tissue stains
Gimenez, Giemsa, modified Ziehl Neelsen
Doesn’t differentiate between Coxiella and Chlamydophila psittaci
Isolation in cell culture or embryonated eggs Serological methods
IFA, ELISA and others
Molecular diagnosis PCR
Treatment and Control of C. burnetti
Treatment and Control
Major challenge
Antimicrobials are not effective in the acidic phagosome where C. burnetii resides
Need to add alkalinizing agents
Chloroquine + Tetracycline
Chloramphenicol, clarithromycin, enrofloxacin and trimethoprim‐sulfa
Ehrlichiae
White blood cell obligate intracellular bacteria
Multiply within membrane‐lined intracytoplasmic vesicles
Ehrlichiae canis
Reservoir and transmission
Agent of CANINE MONOCYTIC EHRLICHIOSIS
Only few cases of human monocytic ehrlichiosis due to E. canis Brown dog tick (Rhipicephalus sanguineus)
Obtain the bacteria from infected dogs only during acute diseases (~2 weeks)
Dog can remain infected for years, despite therapy
Puppies and particular breeds are more susceptible
All continents (except Australia, low to no cases)
Tropical and subtropical latitudes
Ehrlichiae canis Pathogenesis
monocytes live longer, so it can be CHRONIC
subclinical infections usually
Acute and Chronic Diseases of E. canis
Acute diseases
Fever, malaise, depression, inappetance, weight loss, pale
mucous membranes, lymphadenopathy, epistaxis
Thrombocytopenia, leukopenia and anemia (pancytopenia)
Chronic diseases
Dyspnea, enlargement of spleen, lymph nodes and liver
Polyarthritis, CNS disturbances and pulmonary infiltration
Secondary infections
E. canis Immunological aspects
Immunological aspects
Progression to the latent and chronic occurs mainly in dogs with genetic predisposition and possibly impaired cell‐ mediated immunity
Latent infections may reside in spleen, liver, bone marrow Not known at this time
Cellular and humoral immune‐mediated response to infected mononuclear cells and platelets contribute to:
Blood cell destruction
Bone marrow depression Polyarthritis
Uveitis
Immune complex deposition possible
Lab Diagnosis of E. canis
Laboratory diagnosis
Giemsa‐stained smears of buffy coat
Colonies (morulae) less than 4 μm in diameter are demonstrable
Scarce and found mainly during acute stage
Canine cell lines can be used for culture and isolation
Serology
IFA
Molecular PCR
E. chaffeenis
E. chaffeensis
Human monocytic ehrlichiosis
Closely related to E. canis
Its vector is Dermacentor variabilis (American dog tick) Mammalian reservoir is the deer
E. ewingii
E. ewingii
Agent of canine granulocytic ehrlichiosis
Amblyoma americanum (Lone star tick)
Mainly in central North America
Similar disease to A. phagocytophilum infection
Treatment and Control of E. canis, ewingii and chaffeenis
Treatment and Control
Tetracyclines and imidocarb dipropionate
Mainly in acute cases
Less so in advanced cases
Doxycycline and steroids
Late‐stage monocytic ehrlichiosis
POOR PROGNOSIS
PREVENTION Tick control
African heartwater
Ehrlichia ruminantium causative agent
REPORTABLE DISEASE
Mainly in ruminants in Africa and parts of the Caribbean
Passed only by parenteral introduction to the blood
Tick vector is Amblyomma spp.
Replicates in reticuloendothelial cells
Macrophages, endothelial cells, and neutrophils
Pathogenesis of African heartwater
CS; edema, and likes to go to pericardium can see NS signs
Acute, Subclinical, and Percute CS of African Heartwater
Peracute form
Fever of several hours
Collapse and death under convulsion
Acute form- Very common
Fever followed by neurological signs
Hyperexitability, muscle tremors, ataxia, deficit in conscious proprioception, head pressing, coma and seizures
Death within 2‐10 days
Mortality 6‐80%
Subclinical form is also described
Hydropericardium, hydrothorax, congestion
Splenomegaly and extensive hemorrhages
Pathological Findings of African heartwater
Widespread vasculitis with effusion
Epithelial and endothelial hemorrhages
Pericardial effusion and encephalitis can occur
Enlarged spleen, liver and lymph nodes
Bone marrow depression
What is one of the findings on necropsy from african heartwater?
hemorraghic lesions in muliple organs
Immunological and Lab diagnosis of E. ruminantium
Immunologic aspects
Some cattle breeds and newborns appear to be resistant
In surviving cattle, cell‐mediated immunity persists for up to 5 years (unless a different isolate)
Laboratory diagnosis
Demonstration of agent in Giemsa‐stained smears
Molecular and serological diagnosis
Treatment and Prevention of E. ruminantium
Treatment
Tetracycline
Effective if early during diseases presentations
Prevention
Tick control and vaccination are important
Young calves and lambs are vaccinated with virulent bacteria
Older cattle infected & immediately treated
Generals for Neorickettsia
Small, non‐motile, coccoid, intracytoplasmic
Found within vacuoles of monocytes, macrophages and
enterocytes
Gram‐negative bacteria
Stain readily with Macchiavello and Giemsa stain
Cannot be cultivated in cell‐free media or chicken embryos
Fluke serve as vectors
All stages within the life cycle of fluke are infectious
Salmon posioning disease
Caused by Neorickettsia helminthoeca in Pacific Northwest coast
Range of the snail intermediate
Elokomin fluke fever is a mild form of salmon poisoning disease
Infects lymphoreticular tissues of canids (LN, Peyers patches)
Target cell are the canine mononuclear cells
Multiplies in cytoplasm, frequently forming multiple morulae and
filling the entire cell
Infects dogs after ingestion of fluke (Nanophyetus salmincola)
Neorickettsia helminthoeca is maintained by transovarial passage in the helminth
Found throughout the life cycle of the fluke INCLUDING FREE‐SWIMMING CERCARIA
encysted in salmonid fish
Host of salmon posioning and pathogenesis
Generally only members of family Canidae Reported in captive polar bears and raccoons
Acute diseases - salmon poisioning
Acute diseases
Fever, depression, dehydration, anorexia, vomiting, weight loss, hemorrhagic diarrhea, and lymphadenopathy
From proliferation of reticuloendothelial components
Case fatality high in untreated dogs
Recovered animals are immune to re‐infection
Diagnosis and Prevention of Salmon Poisioning
Diagnosis
Detection of fluke eggs in feces, history, clinical signs,
LOCATION
Organism in lymph node aspirates
Has been propagated in cell culture media
Serology/molecular
IFA, can be unreliable, PCR best
Differential Diagnosis
Canine Parvovirus 2 and canine distemper
Prevention
Not allow dogs to eat raw fish
Sick animals
Supportive care
Control vomiting and diarrhea Maintain acid‐base balance
Tetracycline, penicillin G, chloramphenicol and sulfonamides No vaccine
Potomac Horse Fever
Also known as:
Equine monocytic ehrlichiosis
Equine scours
Acute diarrheic illness of equids
Caused by Neorickettsia (Ehrlichia) risticii
Affinity for blood monocytes, tissue macrophages, and intestinal epithelial cells
Epidemelogy of Potomac Horse Fever
Very little is known
US, Canada, South America
Serological Europe, Asia and Australia
Proximity to bodies of water
Seasonal pattern Mainly summer
Very little is known
US, Canada, South America
Serological Europe, Asia and Australia
Proximity to bodies of water
Seasonal pattern Mainly summer
Infectious life cycle involves an intermediate snail reservoir and trematode cercaria
Aquatic insects also suspected, mayflies
Potomac Horse Fever Clinical Signs
Primary clinical sign is acute, watery diarrhea
Fever, anorexia, mild colic, depression, dehydration,
laminitis and leukopenia
Case fatality is 5‐30%
Enterocyte infection with loss of microvilli and malabsorption of sodium and chloride ions and lack of water resorption
DIARRHEA
Dx and Tx of Potomac Horse Fever
Diagnosis History
Wright‐stained blood smears Not reliable
Serology ‐ unreliable IFA, ELISA
Molecular detection PCR
Treatment
Available vaccine is questionable Heterogeneity among isolates
Deficiency in antibody response
IV administration of tetracycline or oxytetracycline early in the course of diseases
Aeyptianosis
Diseases caused by Aegyptianella pullorum
Affects poultry and wild birds
Vector are tick of genus Argus
Present with ruffled feathers, anorexia, diarrhea, anemia and hyperthermia
Lesions include hepatosplenomegaly and punctiform hemorrhages of serosal surfaces
Treatment with tetracyclines
Control of ticks is important
Salmoning poisiong and potmac horse fever cause….
GI SIGNS
