Infectious Diseases - Dogs Part 2 Flashcards
Clostrididum botulinum
gram positive, straight to slightly curved, motile, anaerobic rods
grows best in anaerobic conditions with warmth
disease caused by ingestion of toxin
found in wounds, food, fly maggots
Botulinal toxins
LMN disease/paralysis - prevent presynaptic release of Ach at neuromuscular junction
Diagnosis of clostridium botulinum
Clinical signs, EMG, find toxin in serum, feces, vomitus or stomach content
mouse inoculation test
Treatment of clostridium botulinum
supportive care, anti toxin not useful because doesn’t contain specific type C antitoxin
antibacterial - metronidazole or penicillins
Prevention of clostridium botulinum
heat food
vaccination against toxins type A, B, C, D, E
dogs and cats quite resistant but can still become infected
Clostridium tetani
gram positive, motile, anaerobic, spore-producing bacterium
tetanus caused by neurotoxin found in C. tetani
Two neurotoxins found in C. Tetani?
tetanleptin - causes hemolysis of erythrocytes (not as important)
tetanospasmin - causes neurological dysfunction by inhibiting motor neurons
toxin migrates up the motor nerves and can enter spinal cord, and ascends into brain. also affects cranial nerve
toxin inhibits release of glycine and y-aminobutyric acid (inhibitory neurotransmitters)
Clinical Signs of C. tetani infection
ear drawn back sardonic grin trismus salivation dysphagia gait - ambulatory but rigid progress to opisthotonus, convulsions and respiratory compromise --> death
Diagnosis of C. tetaniinfection
CS, leukocytosis, neutrophilia, tachyarrhythmia or bradyarrythmia, megaesophagus on rads, isolation of bacteria from wound (difficult)
Which of the following is FALSE regarding treatment of C. tetani?
A) toxin wears off over 3-4w during which time supportive care is needed
B) there is no antitoxin
C) antibiotics such as metronidazole or penicillin G to treat and reduce toxin formation
D) sedatives to control seizures and convulsiosn
B - there is an antitoxin - best to give IM
Clostridium difficile
can potentially produce diarrhea
not all species are toxin producing strains
CS: acute hemorrhagic diarrhea - small and large bowel signs
Diagnosis: detection of fecal toxin, cell culture and cytotoxicity assay is gold standard. can also do serology but not as good. Detection of organism with PCR or ELISA
Treatment: metronidazole
Mycoplasma haemocanis
transmitted through brown tick, rhipicephalus sanguine
splenectomy required before CS develop (though uncommon in dog)
Dx: PCR or organism on blood smear
Treatment - doxycycline
Canine Bartonellosis
epidemiology poorly understood, likely get it from dog bites, fleas, and cat scratches
Dx- serology (but 50% sensitive because cross reactions with rickettsial app), bacterial isolation (PCR)
Tx: no evidence based medicine, we use doxy and enrofloxacin/rifampin for dogs and doxy and pradofloxacin in cats
Rocky Mountain spotted fever caused by:
rickettsia rickettsia
Monocytotrophic ehrlichiosis caused by
Ehrliche canis, E. chaffeensis
Granulocytotrophic ehrlichiosis caused by
E. ewingii
Granulocytotrophic anaplasmosis caused by
anaplasma phagocytophilum
thrombocytotropic anaplasmosis caused by
A. platys
Salmon poisoining
neorickettsia helminthoeca
Pathophysiology for most rickettsial diseases
rickettsiae enter blood, replicate in the endothelial cells –> vascular damage and increased vascular permeability and leakage of fluid/erythrocytes into extravascular space
vasculitis leads to thrombocytopenia and decreased albumin (peripheral edema)
petechiation, bleeding, lameness
Ehrlichial organisms (E. Canis, E. chaffeensis)
vectors: rhipicephalus spp, amblyomma americanum
infects mononuclear cells - often get lymphadenopathy
infected cells stick to vascular endothelium = vasculitis = clinical signs
Anaplasma organisms
A. equi or A. ewingii - infects neutrophils, lameness, fever, joint swelling and pain
A. phagocytophilum - infects neutrophils, vector = ixodes, anemia and leukopenia
A. platys - cyclic thrombocytopenia, found in platelets, vector = rhipicephalus and dermacentor spp
Rocky Mountain Spotted Fever
vector - dermacentor variables, cannot diagnose on blood smear
blood tests for PCR, antibody count
skin biopsies - multifocal areas of crusting on the skin, can be erosive
rickettsia rickettsia
Diagnosing rickettsial disease
blood smear/cytology - lucky to find the organism
serology - look for antibodies against organism (IgM or IgG if long term infection)
PCR
Minimum data base expected with rickettsial disease
hematology - thrombocytopenia, neutropenia, lymphocytosis, anemia (regen if due to blood loss or destruction, non region if organism in bone marrow causing pancytopenia)
chemistry - hypoalbuminemia, hyperglobulinemia
urine - proteinuria
T/F: lab changes for rickettsial diseases are the same as those for borreliosis
true
Other signs associated with rickettsial diseases
cardiac - AV blocks tachycardia, arrhythmias
CNS - vestibular and cerebellar signs, coma, paralysis
ocular - hemorrhage (retinal)
renal - azotemia (glomerulonephritis)
pulmonary - edema
GI - vomiting, diarrhea, melena
integument - petechial bleeds, epistaxis
Chronic rickettsial diseases mainly due to
E. canis
treatment of rickettsial diseases
doxycycline
Prevention of rickettsial diseases
tick control, ensure blood donors are sero-negative
Which of the following is NOT zoonotic? A) E. chaffeensis B) E. ewingii C) A. equi D) A. phagocytophilum
C - A. equi
Salmon poisoining
Neorickettsia helminthoeca
fever, serum to purulent ocular discharge, periorbital edema, vomiting and diarrhea, weight loss, lymphadenopathy, splenomegaly
Dx - fluke eggs, rickettsial inclusions in lymph nodes
Tx - supportive care and tetracycline/doxycycline
