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Created page with '{{unfinished}} ===Overview=== *Cause systemic diseases in animals *Usually use arthropod vectors *Host and cell type specificity *Q fever and Rocky Mountain spotted fever are z…'
{{unfinished}}
===Overview===
*Cause systemic diseases in animals
*Usually use arthropod vectors
*Host and cell type specificity
*Q fever and Rocky Mountain spotted fever are zoonoses
===Characteristics===
*Non-motile, pleomorphic Gram-negative organisms
*Obligate intracellular pathogens
*Require live cells for culture such as tissue culture cells or embryonated eggs
*Require Romanowsky stains
*Include two families, ''Rickettsiaceae'' and ''Anaplasmataceae''
*''Rickettsiaceae'' have cell walls that contain peptidoglycan; they target endothelial cells and leukocytes
*''Anaplasmataceae'' lack cell walls; they target erythrocytes
===Epidemiology===
*Rickettsiae replicate in gut epithelial cells of arthropod vectors and spread to other organs such as salivary glands and ovaries
*Transmission occurs during feeding on the animal host
*Transovarial or trans-stadial transmission occurs in the arthropod vectors
*Most ricketsiae have limited survival in the environment, apart from ''Coxiella burnetii'', which undergoes aerosol transmission
===Pathogenesis and pathogenicity===
*Many rickettsiae target endothelial cells of small blood vessels; they produce phospholipase which damages phagosome membranes, escaping into the cytoplasm
*''Ehrlichia'' target leukocytes or platelets, and inhibit phagosome/lysosome fusion
*''Anaplasmataceae'' localise within vacuoles or on the surface of red blood cells; they may alter red cell antigens causing immune-mediated damage. Anaemia may result from haemolysis or removal of red blood cells
===Identification===
*Giemsa-stained blood or tissue smears identify blue/purple organisms
*Fluorescent antibody technique for specific identification
*Isolation in embryonated eggs or tissue culture lines
*Nucleic acid probes and PCR
*Inoculation of susceptible animals
===Rocky Mountain spotted fever===
*Caused by ''Rickettsia rickettsii''
*Affects humans and dogs
*Various tick vectors, which acquire the organism from small mammals
*Transovarial and trans-stadial transmission within the tick population
*Organisms replicate in endothelial cells of infected dogs, cause vasculitis, increased vascular permeability and haemorrhage
*Clinical signs
**Incubation period 2-10 days; course less than 2 weeks
*Fever, depression, conjunctivitis, retinal haemorrhage, muscle and joint pain, coughing, dyspnoea, oedema of extremities
*Neurological signs in dogs include stupor, ataxia, neck rigidity, seizures and coma
*Death from cardiovascular, neurological or renal damage in severely-affected animals
*Gross pathology includes haemorrhage, splenomegaly and lymphadenopathy
*Diagnosis
**Rising antibody titre during an indirect fluorescent antibody test or ELISA
**Thrombocytopenia and leukopenia during early phase
*Treatment and control
**Tetracycline therapy for two weeks
**Tick removal from dogs
===Canine monocytic ehrlichiosis===
*Generalised disease of dogs in tropical and subtropical regions
*Caused by ''Ehrlichia canis''
*The brown tick, ''Rhipicephalus sanguineus'', is the main vector
*Dogs may carry the organism for 2 years after resolution of clinical signs
*Clinical signs
**Incubation period of 3 weeks
**Acute, subclinical or chronic phases
**Acute phase: fever, thrombocytopenia, leukopenia and anaemia
**Subclinical phase: low blood cell numbers but minimal clinical signs; can progress to a severe disease, tropical canine pancytopenia
**Chronic phase: bone marrow depression, haemorrhages, neurological disease, peripheral oedema, emaciation and hypotensive shock
*Diagnosis
**''E. canis'' morulae present in mononuclear cells in Giemsa-stained blood smears
**Rising antibody titre detected by indirect immunofluorescence
**Culture in canine macrophages
*Treatment and control
**Doxycycline for 10 days
**Fluid therapy or blood transfusion
**Prophylactic tetracyclines
===Canine cyclic thrombocytopenia===
*Caused by ''Ehrlichia platys''
*Affects platelets
*Recurrent thrombocytopenia, but dogs usually asymptomatic
*Seroconversion detected by indirect immunofluorescence
===Potomac horse fever===
*Caused by ''Ehrlichia risticii''
*Occurs during the summer
*Fluke vector
*Infects epithelial cells of colon and [[Monocytes - WikiBlood]], macrophages and mast cells
*Clinical signs
**Fever, anorexia, depression, diarrhoea, colic, leukopenia, laminitis
*30% mortality
*Can cause abortion
*Hyperaemia of large intestine at post mortem
*Diagnosis
**Seroconversion detected by indirect immunofluorescence or ELISA
*Treatment and control
**Oxytetracycline for 1 week
**Inactivated vaccines
===Equine granulocytic ehrlichiosis===
*Caused by ''E. equi''
*Clinical signs: fever, depression, ataxia, limb oedema, icterus and petechial haemorrhages
*Low mortality
*Diagnosis: presence of morulae in [[Neutrophils - WikiBlood|neutrophils]] during early disease; seroconversion; leukopenia
*Treatment: tetracyclines
===Bovine petechial fever===
*Caused by ''E. ondiri''
*Disease of cattle in Kenya and other countries of East Africa
*Tick vector
*Clinical signs: intermittent fever, depressed milk yield, petechiation of mucous membranes and conjunctiva
*Death from pulmonary oedema
*Diagnosis: presence of organisms in Giemsa-stained blood smears
*Treatment: tetracyclines
===Tick-borne fever===
*Caused by ''E. phagocytophila''
*Affects ruminants in Europe
*The tick ''Ixodes ricinis'' is the main vector
*Animals remain carriers for up to 2 years, but are immune to reinfection
*Clinical signs
**Incubation period of 2 weeks; recovery in 2 weeks
**Fever, anorexia, reduced growth rates in young animals
**Reduced milk production, abortion, still birth
**Leukopenia and thrombocytopenia
**Causes immunosuppression in young lambs causing susceptibility to tick pyaemia and louping ill
*Diagnosis
**Intracytoplasmic morulae in [[Neutrophils - WikiBlood|neutrophils]] of Giemsa-stained blood smears during acute phase
**Seroconversion detected by immunofluorescence
*Treatment and control
**Oxtetracycline
**Tick control
**Prophylactic tetracyclines for lambs during first few weeks of life
===Heartwater===
*Severe disease of ruminants in sub-Saharan Africa caused by ''Cowdria ruminantium''
*Vectors include ''Amblyomma'' ticks
*Carrier status can occur for up to 8 months in adult cattle and wildebeest
*Clinical disease in calves and lambs
*Clinical signs
**Incubation period 4 weeks
**Acute fever
**Neurological signs including chewing, twitching of eyelids, circling, high-stepping gait, convulsions and recumbency; can be fatal
**Subacute cases suffer from hydropericardium, hydrothorax and pulmonary oedema and congestion; splenomegaly and haemorrhages may occur
*Diagnosis
**Clinical and post mortem findings in endemic areas suggestive
**Orgnisms present in nuclei of endothelial cells in Giemsa-stained brain tissue
**PCR, indirect immunofluorescence, ELISA and western blot
*Treatment and control
**Tetracyclines during early disease
**Immunisation using infected blood
===Bovine anaplasmosis===
*Disease of cattle in tropical and sub-tropical regions caused by ''Anaplasma marginale''
*Carrier status in endemic regions with clinical disease occuring in times of stress
*High mortality rate in naive adult cattle
*Morulae localise inside red blood cells close to the cell membrane
*Transmitted via the ''Boophilus'' tick as well as flies and contaminated instruments
*Clinical signs
**Inculbation period 2-12 weeks
**Anorexia, fever, depression, reduced milk yield, weight loss
**Anaemia and icterus
**Sudden death from hypoxia can occur
*Diagnosis
**Clinical signs and haematology suggestive
**Organisms present in erythrocytes of Giemsa-stained blood smears
**Immunofluorescence of blood smears, PCR, serology
*Treatment and control
**Long-acting oxytetracycline or imidocarb early in the disease
**Supportive therapy
**Vaccination of animals being introduced into an endemic region
===Feline infectious anaemia===
*Caused by ''Mycoplasma haemofelis ( ''until recently, known as'' Haemobartonella felis)
*Organism found on surface of erythrocytes
*Common in roaming tom-cats of 1-3 years old
*Possibly transmitted via bite wounds or arthropods
*Recoverd cats become carriers
*Clinical signs
**Peracute disease is associated with severe anaemia and immunosuppression, and can be rapidly fatal
**Fever, anaemia, depression, weakness and jaundice occur in the acute form
**Anaemia, lethargy and weight loss occur in the chronic form
**Recovery can occur with a regenerative bone marrow response
**Severe feline infectious anaemia may occur in the presence of feline leukaemia virus
*Diagnosis
**Organism intermittently seen on the surface of red blood cells in Giemsa-stained blood smears
**Immunofluorescence of blood smears
**Reduced packed cell volume; regenerative anaemia
*Treatment
**Doxycycline for 3 weeks early in the course of the disease
**Blood transfusion
**Flea control
===Canine haemobartonellosis===
*Dogs infected with ''Haemobartonella canis'' usually asymptomatic
*Acute haemolytic anaemia may occur in dogs after splenectomy, immunosuppressive drug therapy or immunosuppressive infections
===Q fever===
*Caused by ''Coxiella burnetti''
*Influenza-like disease of humans in contact with farm animals
*Transmitted to humans by inhalation from parturient sheep, goats and cattle
*Organisms replicate in female genital tract and mammary glands of ruminants
*Shedding occurs in uterine discharges, foetal fluid and milk
*Infections in animals usually subclinical
*Sporadic abortions occur in sheep, goats, cattle, cats
*Infertility may result in ruminants, as well as placentitis or endometritis
*Hepatitis, myocarditis and interstitial pneumonia may occur in affected foetuses
*Diagnosis: MZN-stained smears of placental tissue and uterine discharges; immunofluorescence; PCR; culture; serology
*Control: disposal of infected placenta and separation of pregnant ruminants; inactivated vaccines
[[Category:Infectious_Agents]]
===Overview===
*Cause systemic diseases in animals
*Usually use arthropod vectors
*Host and cell type specificity
*Q fever and Rocky Mountain spotted fever are zoonoses
===Characteristics===
*Non-motile, pleomorphic Gram-negative organisms
*Obligate intracellular pathogens
*Require live cells for culture such as tissue culture cells or embryonated eggs
*Require Romanowsky stains
*Include two families, ''Rickettsiaceae'' and ''Anaplasmataceae''
*''Rickettsiaceae'' have cell walls that contain peptidoglycan; they target endothelial cells and leukocytes
*''Anaplasmataceae'' lack cell walls; they target erythrocytes
===Epidemiology===
*Rickettsiae replicate in gut epithelial cells of arthropod vectors and spread to other organs such as salivary glands and ovaries
*Transmission occurs during feeding on the animal host
*Transovarial or trans-stadial transmission occurs in the arthropod vectors
*Most ricketsiae have limited survival in the environment, apart from ''Coxiella burnetii'', which undergoes aerosol transmission
===Pathogenesis and pathogenicity===
*Many rickettsiae target endothelial cells of small blood vessels; they produce phospholipase which damages phagosome membranes, escaping into the cytoplasm
*''Ehrlichia'' target leukocytes or platelets, and inhibit phagosome/lysosome fusion
*''Anaplasmataceae'' localise within vacuoles or on the surface of red blood cells; they may alter red cell antigens causing immune-mediated damage. Anaemia may result from haemolysis or removal of red blood cells
===Identification===
*Giemsa-stained blood or tissue smears identify blue/purple organisms
*Fluorescent antibody technique for specific identification
*Isolation in embryonated eggs or tissue culture lines
*Nucleic acid probes and PCR
*Inoculation of susceptible animals
===Rocky Mountain spotted fever===
*Caused by ''Rickettsia rickettsii''
*Affects humans and dogs
*Various tick vectors, which acquire the organism from small mammals
*Transovarial and trans-stadial transmission within the tick population
*Organisms replicate in endothelial cells of infected dogs, cause vasculitis, increased vascular permeability and haemorrhage
*Clinical signs
**Incubation period 2-10 days; course less than 2 weeks
*Fever, depression, conjunctivitis, retinal haemorrhage, muscle and joint pain, coughing, dyspnoea, oedema of extremities
*Neurological signs in dogs include stupor, ataxia, neck rigidity, seizures and coma
*Death from cardiovascular, neurological or renal damage in severely-affected animals
*Gross pathology includes haemorrhage, splenomegaly and lymphadenopathy
*Diagnosis
**Rising antibody titre during an indirect fluorescent antibody test or ELISA
**Thrombocytopenia and leukopenia during early phase
*Treatment and control
**Tetracycline therapy for two weeks
**Tick removal from dogs
===Canine monocytic ehrlichiosis===
*Generalised disease of dogs in tropical and subtropical regions
*Caused by ''Ehrlichia canis''
*The brown tick, ''Rhipicephalus sanguineus'', is the main vector
*Dogs may carry the organism for 2 years after resolution of clinical signs
*Clinical signs
**Incubation period of 3 weeks
**Acute, subclinical or chronic phases
**Acute phase: fever, thrombocytopenia, leukopenia and anaemia
**Subclinical phase: low blood cell numbers but minimal clinical signs; can progress to a severe disease, tropical canine pancytopenia
**Chronic phase: bone marrow depression, haemorrhages, neurological disease, peripheral oedema, emaciation and hypotensive shock
*Diagnosis
**''E. canis'' morulae present in mononuclear cells in Giemsa-stained blood smears
**Rising antibody titre detected by indirect immunofluorescence
**Culture in canine macrophages
*Treatment and control
**Doxycycline for 10 days
**Fluid therapy or blood transfusion
**Prophylactic tetracyclines
===Canine cyclic thrombocytopenia===
*Caused by ''Ehrlichia platys''
*Affects platelets
*Recurrent thrombocytopenia, but dogs usually asymptomatic
*Seroconversion detected by indirect immunofluorescence
===Potomac horse fever===
*Caused by ''Ehrlichia risticii''
*Occurs during the summer
*Fluke vector
*Infects epithelial cells of colon and [[Monocytes - WikiBlood]], macrophages and mast cells
*Clinical signs
**Fever, anorexia, depression, diarrhoea, colic, leukopenia, laminitis
*30% mortality
*Can cause abortion
*Hyperaemia of large intestine at post mortem
*Diagnosis
**Seroconversion detected by indirect immunofluorescence or ELISA
*Treatment and control
**Oxytetracycline for 1 week
**Inactivated vaccines
===Equine granulocytic ehrlichiosis===
*Caused by ''E. equi''
*Clinical signs: fever, depression, ataxia, limb oedema, icterus and petechial haemorrhages
*Low mortality
*Diagnosis: presence of morulae in [[Neutrophils - WikiBlood|neutrophils]] during early disease; seroconversion; leukopenia
*Treatment: tetracyclines
===Bovine petechial fever===
*Caused by ''E. ondiri''
*Disease of cattle in Kenya and other countries of East Africa
*Tick vector
*Clinical signs: intermittent fever, depressed milk yield, petechiation of mucous membranes and conjunctiva
*Death from pulmonary oedema
*Diagnosis: presence of organisms in Giemsa-stained blood smears
*Treatment: tetracyclines
===Tick-borne fever===
*Caused by ''E. phagocytophila''
*Affects ruminants in Europe
*The tick ''Ixodes ricinis'' is the main vector
*Animals remain carriers for up to 2 years, but are immune to reinfection
*Clinical signs
**Incubation period of 2 weeks; recovery in 2 weeks
**Fever, anorexia, reduced growth rates in young animals
**Reduced milk production, abortion, still birth
**Leukopenia and thrombocytopenia
**Causes immunosuppression in young lambs causing susceptibility to tick pyaemia and louping ill
*Diagnosis
**Intracytoplasmic morulae in [[Neutrophils - WikiBlood|neutrophils]] of Giemsa-stained blood smears during acute phase
**Seroconversion detected by immunofluorescence
*Treatment and control
**Oxtetracycline
**Tick control
**Prophylactic tetracyclines for lambs during first few weeks of life
===Heartwater===
*Severe disease of ruminants in sub-Saharan Africa caused by ''Cowdria ruminantium''
*Vectors include ''Amblyomma'' ticks
*Carrier status can occur for up to 8 months in adult cattle and wildebeest
*Clinical disease in calves and lambs
*Clinical signs
**Incubation period 4 weeks
**Acute fever
**Neurological signs including chewing, twitching of eyelids, circling, high-stepping gait, convulsions and recumbency; can be fatal
**Subacute cases suffer from hydropericardium, hydrothorax and pulmonary oedema and congestion; splenomegaly and haemorrhages may occur
*Diagnosis
**Clinical and post mortem findings in endemic areas suggestive
**Orgnisms present in nuclei of endothelial cells in Giemsa-stained brain tissue
**PCR, indirect immunofluorescence, ELISA and western blot
*Treatment and control
**Tetracyclines during early disease
**Immunisation using infected blood
===Bovine anaplasmosis===
*Disease of cattle in tropical and sub-tropical regions caused by ''Anaplasma marginale''
*Carrier status in endemic regions with clinical disease occuring in times of stress
*High mortality rate in naive adult cattle
*Morulae localise inside red blood cells close to the cell membrane
*Transmitted via the ''Boophilus'' tick as well as flies and contaminated instruments
*Clinical signs
**Inculbation period 2-12 weeks
**Anorexia, fever, depression, reduced milk yield, weight loss
**Anaemia and icterus
**Sudden death from hypoxia can occur
*Diagnosis
**Clinical signs and haematology suggestive
**Organisms present in erythrocytes of Giemsa-stained blood smears
**Immunofluorescence of blood smears, PCR, serology
*Treatment and control
**Long-acting oxytetracycline or imidocarb early in the disease
**Supportive therapy
**Vaccination of animals being introduced into an endemic region
===Feline infectious anaemia===
*Caused by ''Mycoplasma haemofelis ( ''until recently, known as'' Haemobartonella felis)
*Organism found on surface of erythrocytes
*Common in roaming tom-cats of 1-3 years old
*Possibly transmitted via bite wounds or arthropods
*Recoverd cats become carriers
*Clinical signs
**Peracute disease is associated with severe anaemia and immunosuppression, and can be rapidly fatal
**Fever, anaemia, depression, weakness and jaundice occur in the acute form
**Anaemia, lethargy and weight loss occur in the chronic form
**Recovery can occur with a regenerative bone marrow response
**Severe feline infectious anaemia may occur in the presence of feline leukaemia virus
*Diagnosis
**Organism intermittently seen on the surface of red blood cells in Giemsa-stained blood smears
**Immunofluorescence of blood smears
**Reduced packed cell volume; regenerative anaemia
*Treatment
**Doxycycline for 3 weeks early in the course of the disease
**Blood transfusion
**Flea control
===Canine haemobartonellosis===
*Dogs infected with ''Haemobartonella canis'' usually asymptomatic
*Acute haemolytic anaemia may occur in dogs after splenectomy, immunosuppressive drug therapy or immunosuppressive infections
===Q fever===
*Caused by ''Coxiella burnetti''
*Influenza-like disease of humans in contact with farm animals
*Transmitted to humans by inhalation from parturient sheep, goats and cattle
*Organisms replicate in female genital tract and mammary glands of ruminants
*Shedding occurs in uterine discharges, foetal fluid and milk
*Infections in animals usually subclinical
*Sporadic abortions occur in sheep, goats, cattle, cats
*Infertility may result in ruminants, as well as placentitis or endometritis
*Hepatitis, myocarditis and interstitial pneumonia may occur in affected foetuses
*Diagnosis: MZN-stained smears of placental tissue and uterine discharges; immunofluorescence; PCR; culture; serology
*Control: disposal of infected placenta and separation of pregnant ruminants; inactivated vaccines
[[Category:Infectious_Agents]]