What are the characteristics of Actinomyces?
- Gram stain: G+ anaerobic bacteria, filamentous, branching
- Transmission: not transmitted between animals, normal oropharyngeal and GI inhabitant
- Who gets it: young large breed dogs (immune competent, introduced by a foxtail or bite wound)
- CS: chronic pyogranulomatous pleural space disease with sulfur granules and hilar lymphadenopathy
- Skin lesions of fluctuant SC swellings, sometimes with draining sinus tracts
- Organomegaly, retroperitoneal space, CNS
- Dx: acid fast stain (not!), culture (slow growing anaerobe), histopath
- Txt: drain abscess/pyothorax first, then high dose penicillins or doxy for cutaneous (1-3 months), pulmonary (6 months), systemic (12 months)
- Px: 90% recovery
What are the characteristics of Nocardia?
- Gram stain: G+ aerobic bacteria, filamentous, branching
- Transmission: not transmitted between animals, much less common than actinomyces, ubiquitous soil saprophyte (found in house dust, beach sand, garden soil, swimming pools)
- Who gets it: cats or young adult, male dogs (1/4 to 1/3 are immunosuppressed)
- CS: cause chronic pyogranulomatous pulmonary infx
- Dx: culture, histopath, acid fast stain (variable)
- Txt: susceptibility testing is difficult, then high dose TMS for cutaneous (1-3 months), pulmonary (6 months), systemic (12 months)
- Px: not as good as Actinomyces
What are the characteristics of mycobacteria?
- Stain: G+ aerobic, nonmotile bacteria. Cell wall rich in mycolic acid so is acid-fast, resistant to phagocytosis
- Transmission: resistant in the environment, killed by direct sunlight and dilute household bleach
- Caused by: tuberculous mycobacteria (M. tuberculosis and M. bovis), opportunistic mycobacteria (slow-growing M. avium complex and rapidly-growing other), lepromatous mycobacteria (M. lepraemurium, canine leproid granuloma)
- Pathogenesis: defective CMI
- CS of M. TB and MAC: respiratory (coughing, dysphagia, retching, tonsillitis), GI (weight loss, anorexia, V, D, anemia, enlarged MLN, abdominal effusion), disseminated (lymphadenopathy, organomegaly, neurologic signs, ocular disease, osteomyelitis, nonhealing skin lesions)
- CS of RGM: Cutaneous and SC granulomas, in inguinal area, most cats feel fine, systemic signs are rare
- CS of lepro: CA, Australia, short-coated breeds on head or pinnae; never cultured
- Dx: acid fast stain, see elongated beaded orgs (esp MAC and lepro, hard to find with M. TB), histopath (pyogranulomatous inflammation), isolation (multiple biopsies), PCR
- Txt for M. TB: combo of streptomycin, isoniazid, rifampin for > 6 months, should probably euthanize
- Txt for RGM: skin lesions need high doses of FQ or doxycycline, then surgical excision, with intraoperative IV gentamicin, then continue with 3-6 months of doxycycline or a FQ
- Txt of lepro: self limiting, can sx excise
What are the characteristics of M. tuberculosis?
- Highly pathogenic
- Dogs are susceptible, humans are reservoir
- Pulmonary predilection (likes high O2)
- Especially Atlantic coast, SE US, CA
What are the characteristics of M. bovis?
- Cattle main reservoir hosts
- Ingestion of unpasteurized milk or uncooked meat or offal
- GI tract in cats, respiratory tract in dogs
- Dogs and cats rarely spread disease to people
- Cats most commonly infected
What are the characteristics of opportunistic mycobacteria?
- Saprophytic, survive >2years in the environment
- M. avium complex: produce tuberculous lesions, disseminate, prefer acid soils, cats and dogs are quite resistant to infection
- Rapidly-growing: include M. thermoresistible, M. fortuitum, M. smegmatis; inoculated into skin via trauma, enhanced pathogenicity in adipose tissue, most affected animals immune competent, cats most susceptible
What are the characteristics of lepromatous mycobacteria?
- Produce localized cutaneous nodules which may ulcerate
- Difficult or impossible to culture
- Western USA, UK, NZ, Australia, Netherlands
What are the characteristics of E. coli D?
- Caused by: G- facultative aerobe
- Normal intestinal inhabitant that survives in feces, dust, and water for months
- CS: acute or chronic D
- EPEC: Attaching and effacing, causing loss of microvilli and watery D
- ETEC: Adheres to cells and produces LT and ST, inhibits Na and Cl absorption, watery D
- EHEC: is EPEC that produces SLT, causing hemorrhagic diarrhea and vascular endothelial damage, causes HUS in humans
- EIEC: invades colonic epithelial cells then adjacent cells and lymphatics, causing endotoxemia and sepsis especially in neonates or puppies with parvovirus infection, also causes granulomatous colitis in Boxer dogs
- Dx: Difficult! Isolation, toxin assays, PCR can all be found in normal dogs. Biopsy for PAS+ macrophages for Boxer colitis. Blood culture for bacteremia
- Txt: Uncomplicated cases get fluid therapy; Enrofloxacin when melena or Boxer colitis; Sepsis
- requires aggressive treatment with parenteral antimicrobials and fluids
- Prevent: good hygiene
What are the characteristics of Salmonella D?
- Stain: G- rod, S. typhimurium is most commonly isolated
- Transmission: prolonged environmental survival, uncooked or unprocessed pet foods
- Who gets it: Young animals with poor nutrition, stress or immunosuppression
- Pathogenesis: ileal M cells, intense inflammatory response causes chronic shedding or sepsis and DIC
- CS: pyrexia, lethargy and anorexia 3-5 days after infection, thrombosis/ hemorrhage, icterus, abortion, stillbirth, death, rarely chronic diarrhea (up to 8 weeks)
- Dx: CBC (anemia, lymphopenia, thrombocytopenia, neutropenia), chem (hypoproteinemia, hypoglycemia, elevated liver enzymes, azotemia, electrolyte abnormalities), fecal cytology, necropsy (hemorrhagic colitis), isolation (special media)
- Txt: Aggressive IVF colloid therapy, parenteral FQ for sepsis (abx increase shedding)
- Prevent: good hygiene, heat food, isolate infected
What are the characteristics of Campylobacter?
- Stain: G- microaerophilic, curved rod, C. jejuni or C. upsalensis
- Who gets it: dogs and cats < 6 months of age more likely to show signs
- CS: large bowel diarrhea, mucosy, watery, bile-streaked
- Dx: fecal smears (gram stain), isolation (special media), histopathology (silver staining)
- Tx: FQs for 1-3wks; resistant to most other abx. llin, ampicillin and TMS are usually ineffective
What are the characteristics of C. perfringens and C. difficile?
- Stain: G+ anaerobic rods, normal inhabitant
- Transmission: spores resistant in the environment so fomites; some strains produce enterotoxin (CPE) on sporulation
- Pathogenesis of C. perf: sporulation triggered by abx and alkaline intestine, viral infection, obstruction/strangulation, diet changes, immunosuppression
- Pathogenesis of C. diff: toxin A and toxin B triggered by abx maybe
- CS: watery to mucohemorrhagic diarrhea that is acute, chronic, or intermittent
- Dx: Difficult! Fecal toxin detection using ELISA (CPE, toxins A & B)
- Txt: not subclinical shedders; IVF, high fiber diet, ampicillin, clavamox, tylosin, or clindamycin for 5-7 days
- Prevent: Isolate affected animals, good hygiene, hypochlorite disinfectants
What are the characteristics of deep mycoses in general?
- Who gets it: Young adult, male, large breed hunting dogs & cats
- Pathogenesis: Inhalation of spores from the environment, which incubates >couple of weeks. Host immune competence very important
- CS: pulmonary infection may resolve before lesions appear elsewhere (as with other fungal infections)
- Dx: CBC (NR anemia, leukocytosis, lymphopenia), chemistry (hyperglobulinemia, hypoalbuminemia, cytology and histopathology (know structures!), serologic tests (know Ab vs Ag tests)
- Txt: itraconazole ($$$, doesn't penetrate to eye), fluconazole (penetrates to eye and urine) or Amphotericin B to inhibit fungal sterol synthesis
What are the most common fungal diseases of dogs and cats? What is their geographic distribution?
Will be a test question
What are the SE of azoles and amphotericin B?
- Azoles: Ulcerative dermatitis (itraconazole), reversible
- Hepatopathy (anorexia) so monitor liver enzymes monthly and reduce dose if ALT > 400, stop if anorexic/vomiting
- Amphotericin B: nephrotoxicity (lipid forms have less)
What are the characteristics of coccidioidomycosis?
- Look like: dimorphic fungi, thick-walled, barrel-shaped, multinucleate arthroconidia
- Transmission: soil arthrospores dispersed by wind and inhaled, rainfall in late summer and early fall
- Who gets it: young adult, large breed dogs; feline disease very rare
- Location: SW US (AZ, TX, CA, San Joaquin Valley), Mexico, Central and South America
- Incubation period 1 to 3 weeks
- Pathogenesis: arthrospores form a spherule -> endospores, which attracts macrophages and neutrophils and form new spherules to infect bronchioles, alveoli, peribronchiolar the subpleural tissue, then to hilar LNs over 3-4 months with immunosuppression (especially bones, eyes, heart and pericardium, testicles, brain, spinal cord, spleen, liver and kidney)
- CS: Coughing (hilar lymphadenopathy or pulmonary involvement), systemic signs (lameness, lymphadenopathy, skin lesions, R-CHF, CNS signs)
- Dx: chest rads (miliary to nodular interstitial patterns, hilar lymphadenopathy, pericardial and pleural effusion); cytology and histopath (spherules but low sensitivity), serology (Ab detection, titers correlate with disease severity, CF titers of 1:4 or less occur in healthy dogs in endemic areas)
- Txt: >1yr antifungal treatment, esp itraconazole, AMB for disseminated disease. Monitor titers every 1-2 months during treatment
What are the characteristics of blastomycosis?
- Caused by: Blastomyces dermatitidis, dimorphic fungus; thick, refractile, double-contoured cell wall and broad-based budding
- Who gets it: dogs and people, rarely cats. Dogs are 10x more susceptible than humans
- Transmission: likes water sources and acid, sandy soils, expect recent soil disturbance. Spores inhaled -> yeast form in the lungs, disseminates via blood and lymph to skin and SC tissues, bone, eyes, LNs, testes, brain
- Location: upper Midwest and 95% of dogs are < 400 m from water; mainly North America (Mississippi, Missouri and Ohio River valleys, Mid-Atlantic States).
- CS: lethargy, fever, nodular draining skin lesions, lymphadenopathy, lung involvement (>80%), ocular involvement (40%), lameness (bone or joint involvement)
- Dx: chest rads (diffuse, nodular interstitial disease, hilar lymphadenopathy), skeletal rads (osteolysis with periosteal proliferation), cytology (pyogranulomatous inflammation), Ag testing (sensitive! run on urine)
- Txt: initial worsening then a response 3-5 d later. Support with fluids, NE tube feeding, oxygen, humidification, coupage, aspirin. Enucleation usually required for endophthalmitis and glaucoma
- Px: 60% survival with treatment, relapse rate 20% in first 6 months. Poor prognosis with brain involvement, severe pulmonary involvement
- Prevent: restrict dogs from endemic areas and construction sites.
What are the characteristics of Histoplasmosis?
- Caused by: Histoplasma capsulatum, soil borne dimorphic fungus found in bird and bat feces
- Location: most US casesin the southern half of OH, MI and MO river valleys
- Who gets it: cats more susceptible than dogs, most <4yrs old
- Pathogenesis: mycelia produce macroconidia and microconidia, which are inhaled, microconidia → yeasts which bud intra- and extracellularly -> dissemination via blood and lymph. GI disease follows respiratory infection
- CS in cats: most have disseminated disease, nonspecific signs common. Dyspnea, organomegaly, retinal detachment, optic neuritis, bone involvement
- CS in dogs: inappetence, fever, dyspnea, C, organomegaly (icterus, ascites), most have GI involvement (colitis, watery D and PLE), bone marrow involvement (no optic lesions)
- Notice: Histo doesn't have skin lesions (blasto and coccidio do)
- Dx: chest rads (miliary or nodular patterns), pulm mineralization, hilar lymphadenopathy), abd rads (organomegaly), cytology (in macrophages on rectal scrapings or endoscopic biopsies, BAL or TTW fluid, FNA of affected organs. Histo much smaller than blasto!), Ag test (sensitive and specific in cats, possible cross-reactions with other fungi)
- Txt: ITZ +/- AMB for 4-6 months
- Px: fair to excellent