Week 7

• Neorickettsia spp.


  • Trematodes as vectors
  • Snails as reservoirs
• Potomac horse fever (Neorickettsia risticii)


  • Seasonal
  • June to october
  • Transmission: Fresh water snails and trematodes, Aquatic insects, Associated with pastures bordering rivers
  • Horses acquire infection by ingesting water containing insects infected with metacercaria
  • Infects enterocytes and monocytes
• Potomac horse feverpathology

  • Hemorrhagic enterocolitis
• Clinical signs of Potomac horse fever

  • Colic
  • Fever
  • Severe diarrhea
  • Anorexia
  • Profound leukopenia
  • Laminitis
  • Abortion
• Diagnosis of Potomac horse fever

  PCR on blood or feces
• Treatment of Potomac horse fever

  Early diagnosis, Oxytetracycline
• Prevention of Potomac horse fever

  Vaccination, Minimizing insect ingestion in stabled horses, Turn off barn lights at night
• Salmon poisoning disease (Neorickettsia helminthoeca)


  • Hosts: Dogs, Polar bears, Raccoons, Coyotes
  • Reservoirs: Snail
  • Vectors: Trematodes
  • Transmission: Ingestion of raw salmon infected with trematodes
  • Infects monocytes
• Clinical signs of salmon poisoning disease

  • Fever, Depression, Anorexia, Vomiting, Dehydration, Hemorrhagic diarrhea, Lymphadenopathy
  • 90% death of untreated dogs
• Diagnosis of salmon poisoning disease

  Detection of fluke eggs, PCR for bacteria in feces, History and symptoms, Geographic location

  differential diagnosis - canine parvovirus infection
• Treatment of salmon poisoning disease

  Tetracycline, Praziquantel
• Prevention of salmon poisoning disease

  Prevention of feeding infected fish, Snail elimination
• Bartonella spp.

  Small, curved bacilli or cocobacilli, Pleomorphic, Gram-negative, Alpha 2 proteobacteria class, Aerobic, Fastidious to grow on culture, Enriched media BAPGM, Chocolate or blood agar, 5% CO2, Vector transmitted, Hemotropic, nonhemolytic, Long lasting intraerythrocytic bacteremia, Infects macrophages, Endothelial niche, Some related to vascular proliferation
• Prevalence of Bartonella

  Greater in warm and humid climates, Highly adapted to reservoir hosts
• Bartonella bacilliformis

  Etiologic agent of Carrion's disease, Transmitted by sand flies, Oroya fever (acute disease with fever, hemolytic anemia, 44-88% mortality if untreated), Verruga Peruana (chronic disease with skin eruptions and body warts), Proved by Daniel Carrion that Oroya fever and Verruga Peruana are caused by same agent and two different phases of same disease
• Bartonella quintana

  Etiologic agent of trench fever, 5-day relapsing fever, Transmitted by body lice, Lymphadenopathy, Endocarditis, Bacillary angiomatosis in immunocompromised, Sporadic description in cats and dogs
• Bartonella henselae

  Most prevalent, Cat is primary reservoir, Bacteremia in healthy cats, Chronic and recurrent, May persist for months and years, Relapses every several months, Primary zoonotic bacteria associated with cat scratch disease, Detected in humans, wild felids, mongooses, dogs, horses, rodents, seals, whales, Vector: Ctenocephalides felis, Intradermal inoculation of infected feces
• Bartonella clarridgeiae

  Cat is reservoir, Vector: Ctenocephalides felis, Bacteremia in healthy cats, Associated with cat scratch disease-like in humans
• Bartonella hoehlerae

  Cat is reservoir, No clinical disease in experimentally infected cats, Associated with human and canine endocarditis
• Epidemiology of Bartonella in cats

  Most commonly reported in cats and wild felids worldwide, Prevalence in cats: 5-40% serology, 15-55% bacteremia by PCR, May reach 80-90% depending on geographic and climate conditions
• Clinical signs of Bartonella henselae in cats

  • Infected experimentally: Most cats exhibit no clinical signs, Mild induration or abscesses at inoculation site, Lymphadenopathy, 2-4 day fever, Lethargy, Anorexia, Muscle pain, Mild neurologic signs
  • Natural infections: Endocarditis, Myocarditis, Uveitis, Fever, FeLV worsens the course of the disease
• Human diseases caused by Bartonella henselae


  Cat scratch disease, Bacillary angiomatosis, Vasculoproliferative lymphatic tumors, Vasculitis, Peliosis hepatis, Meningitis, encephalitis, neuroretinitis, Endocarditis, Psychiatric symptoms
• Canine bartonelosis

  Canids primary reservoir, Long lasting bacteremia in healthy dogs, Vectors: Bartonella vinsonii subsp. Berkhoffi & Bartonella rochalimae (Ticks: Rhipecephalus sanguines, Ixodes spp.), B. henselae (Ctenocephalides felis, Probably scratches from cats), Infection: Various tissue inflammation, Endocarditis, Vasculitis, Vascular proliferation
• Human diseases caused by Bartonella vinsonii subsp. Berkhoffi & Bartonella rochalimae

  Vasculitis, Endocarditis, Myocarditis
• Bartonella vinsonii subsp. Berkhoffi & Bartonella rochalimae in dogs and humans

  Can cause chronic immunosuppression in dogs, Vasculitis, Endocarditis and Myocarditis in dogs and humans
• Bartonella henselae associated illnesses in dogs

  Endocarditis, Myocarditis, Panniculitis/steatitis, Nodular skin lesions, Pyogranulomatous lymphadenitis, Granulomatous rhinitis, Polyarthritis, Pulmonary nodules
• Diagnosis of Bartonella

  History of flea/tick exposure and clinical signs, Survey healthy animals if owner is immunocompromised, Cytology (not effective with conventional staining), Serology (IFA, ELISA - measures exposure, 50% detection, Cross-reactive with Rickettsia), PCR (confirms infection, Blood, spleen, liver, heart, lymph nodes, Real time PCR increases sensitivity, Limitations for humans and dogs due to very low bacterial loads), Culture (Blood, spleen, liver, heart, lymph node, or other tissue aspiration samples, Pre-enriched BAPGM liquid, BAPGM in chocolate or blood agar & 5% CO2 for 8 weeks, Limitations: Fastidious, Long time to grow, Less sensitive than PCR)
• Treatment of Bartonella in cats

  None proven effective in cats, Side effects common, Recommended for cats showing clinical signs or with immunocompromised owners, Options: Doxycycline (most recommended, partially effective), Enrofloxacin (clears B. henselae or B. clarridgeiae)
• Treatment of Bartonella in dogs

  Derived from experiences in human medicine, Options: Doxycycline, Enrofloxacin, Azithromycin
• Prevention of Bartonella

  Flea/tick control, Routine testing of blood donors, No vaccine available
• Mycoplasma spp.

  Smallest free living bacteria, Don't have rigid cell walls, Triple layered outer membranes, Spherical or filamentous, Small genome, Dependent on host for essential nutrients, Fastidious, Difficult to isolate in the lab, Pleomorphic, Susceptible to drying, Not susceptible to penicillin, Inhabit mucous membranes of respiratory and reproductive tracts, Affinity for ciliated epithelium, Most host specific, Disease in immunocompromized or stressed animals and humans
• Hemotropic mycoplasmas

  Affinity to erythrocyte membranes
• Differentiation of mycoplasmas

  Colonial morphology, Size (0.1-0.6mm), Requirement for cholesterol, Biochemical reactivity, Digitonin inhibits growth
• Pathogenesis of mycoplasmas

  Adhesion to host surface, Produce H2O2 (toxic damage), Evasion through variation of surface proteins, Similarity of mycoplasma antigen and host antigen (interfere with host recognition), Modulation of immune system, Pathogenic pulmonary mycoplasmas mitogenic for B and T lymphocytes (induce inflammation)
• Diagnostic procedures for mycoplasmas

  • Specimens: Refrigerated and evaluated until 48 hours, Mucosal scrapings, tracheal exudate, aspirates, pneumonic tissue, mastitic milk and fluids, Swabs from lesion
  • Transport media
  • Direct diagnostic tests: PCR, Culture and isolation
  • Serological tests: Complement fixations or ELISA
  • Ruminants (international trade): Rapid plate agglutination and hemagglutination inhibition tests
• Contagious bovine pleuropneumonia (mycoplasma mycoides subsp. mycoides)


  • Severe contagious disease of cattle, Reportable, Transmission by aerosols, Severity depends on strain virulence and immune status, Endemic in Africa and Asia, Sporadic outbreaks
  • Acute presentation: High fever, Depression, Drop in milk yield, Accelerated respiration, Coughing, Death in 1-3 weeks, Pneumonic lungs have marbled appearance
  • Chronic presentation: Fibrous encapsulation of necrotic tissue
  • Diagnosis: Clinical signs, Post mortem lesions, Antibody in pleural fluid, Culture, PCR, Serological tests
• Mycoplasma bovis

  Worldwide distribution, Associated with chronic respiratory disease, Caseonecrotic bronchopneumonia and scattered rice abscesses in lungs, Associated with mastitis and polyarthritis

  Treatment and control: Management practices, Antimicrobial therapy, Mastitis with systemic involvement may occur, Highly infectious in large herds, Gland fibrosis, Purulent plugs, Purulent mastitic exudate, High leukocyte count, Dramatic loss of milk production
• Enzootic pneumonia of pigs (mycoplasma hyopneumoniae)


  • Worldwide in intensively reared pigs, Transmission by aerosols, Risk factors: Poor ventilation, Overcrowding, Temperature fluctuations, Clinical signs: Coughing, Poor growth rates, Respiratory distress, Post mortem: Pulmonary consolidation in cranial and middle lobes
  • Diagnosis: Isolation is confirmatory but difficult, PCR, ELISA
  • Treatment: Antimicrobial drugs in feed (some resistance)
  • Control/prevention: Development of SPF herds, Monitoring at slaughter, Serological surveillance, Vaccines to reduce clinical disease and production loss
• Mycoplasma gallisepticum

  Reportable, chronic respiratory disease in chickens, Infectious sinusitis in turkeys, Transmission: Infection of embryo in egg or aerosols, Clinical signs: Coughing, Nasal discharges, Sinusitis with exudate production, Reduced egg production
• Mycoplasma synoviae

  • Reportable, Infectious synovitis in chickens and turkeys, Transmitted by aerosols, Clinical signs: Synovitis, Arthritis, Respiratory signs
  • Diagnosis: Culture and isolation, Agglutination tests, PCR
  • Control: SPF flocks, Eggs for hatching, Tylosine solution, Vaccines available