Pathogens: Healthy Populations Block 5 Exam

Virus characteristics

very small (0.25-0.35 um), round shape, protein capsule, enveloped or non-enveloped, needs host to replicate, infects every type of organism on Earth, few antiviral treatments

Canine Parvovirus type 2 (canine)

• small, non-enveloped virus

• highly contagious

• spread by direct contact or contaminated feces and environments (environmentally stable for year in soil)

• causes loss of appetite, vomiting, diarrhea, and dehydration

• not zoonotic

Bovine Papillomavirus (bovine)

• non-enveloped, circular double-stranded DNA virus in family Papillomaviridae

• survive in environment for weeks or months if protected by tissue

• growths resemble cauliflower

• found on head, neck, and shoulders

• can be zoonotic

Feline Leukemia Virus (feline)

• oncogenic, enveloped, immunosuppressive lentivirus

• most common infectious disease in cats (2-3% of cats in US)

• virus shed in saliva, nasal secretions, urine, feces, and milk

• transfer can occur from bite wound mostly and sometimes through shared litter and bowls

• vertical transmission occurs

• can’t survive long outside cat’s body

• outcomes after exposure are immunity, transient viremia with latency and clearance, persistent viremia

Bovine Viral Diarrheal Virus (bovine)

• single-stranded RNA enveloped virus

• genome = single, linear, positive-sense, single-stranded RNA molecule 12.3kb

  • catalyzed by BVDV RNA-dependent RNA polymerase

• most costly viral disease in US cattle (2 billion/year)

• found everywhere in US (5% of herds)

• immunosuppressive virus

• syndromes = respiratory, digestive, reproductive

Bacteria Characteristics

• single-cell organisms

• 10-100 times larger than viruses

• sphere or rod shaped

• reproduce in environment or in host

• use flagella or glide to move

• can double in number every 15 minutes or take weeks or months

• gram + or gram -

Gram Positive Bacteria

• thick peptidoglycan layer and no outer membrane

• peptidoglycan in cell wall stain purple-blue with crystal violet dye

• 90% of gram + treated with penicillin, cloxacillin, and erythromycin

Streprococcus equi subspecies equi (equine)

• gram positive, beta-hemolytic coccobacillus

• highly contagious upper respiratory infection

• bacterial shedding intermittently

• subclinical carrier sheds bacteria for months to years

• survive in environment for 4-6 weeks

• rarely zoonotic

• clinical signs = fever, lethargy/lack of interest, thick white to yellow nasal discharge, swelling under jaw, white to yellow drainage under jaw

Caseous Lymphadenitis (small ruminants)

• cornebacterium pseudotuberculosis

• gram-positive, facultative, intracellular coccobacillus

• abscess formation near major peripheral lymph nodes (external form) or within internal organs and lymph nodes (internal form)

• incubation period = 1-3 months

• survive on fomites for 2 months or soil for 8 months

• zoonotic

Erysipelothrix rhusiopathiae (swine)

• Erysipelas

• nonsporulating, gram-positive, rod-shaped bacterium

• clinical signs = fever, anorexia, red diamond shaped patches, lameness

• rout of transmission = direct contact (cuts in skin)

• susceptible to penicillin, cephalosporins, erythromycin, and clindamycin

  • resistant to vancomycin

• zoonotic

Gram Negative Bacteria

• thin peptidoglycan layer and outer lipid membrane

• stain red-pink

• more resistant than gram positive

• cause significant morbidity and mortality

• Susceptible to fourth-gen cephalosporins (cefepime), extended-spectrum ß-lactamase inhibitor penicillin (piperacillin/tazobactam, ticarcillin/clavulanate), and most carbapenems (imipenem/cilastatin, meropenem, ertapenem)

Klebsiella mastitis (bovine)

• K. oxytoca and K. pneumoniae responsible for causing clinical mastitis

• gram-negative bacteria shed in manure

• mild = abnormal milk, moderate = abnormal milk and swollen udders, and severe = systemic signs (fever, off feed, decreased production, shock, and recumbency)

• chronic infections

• no intramammary antimicrobials are labeled for treatment in US

• zoonotic

Parasite Characteristics

• eukaryote (have nucleus)

• larger than bacteria

• majority replicate in host

• one cell or many cells

Ascaris Suum

• large roundworm of pigs

• survive in soil for 10 years

• infected pigs may show no symptoms

• heavily infected pigs show symptoms

  • difficulty breathing, thumps

  • weight loss

  • unthrifty

  • slow weight gain

  • whole worms in manure

• zoonotic

Giardia

• single celled parasite of dog intestine

• results in diarrhea

• extended giardiasis causes weight loss, poor condition, and death

• many infected dogs don’t show disease

• dogs infected with giardia cyst are swallowed from water

• highly contagious

  • feces

  • contact

  • contaminated surfaces

• survive several months in cold water or soil

• zoonosis not likely

  • more likely from chinchillas, beavers, birds, opossums, and monkeys

Fungi Characteristics

• eukaryotes (nuclei and vacuoles)

• largest pathogen

• many shapes

• most common = environmentally resistant spores and molds

• found in rotting vegetation or animal feces

• cause skin infections and pneumonia

Dermatophytosis (canine, feline, and livestock)

• trichophyton or mycosporum genera fungi

• hair and wool loss occur at affected area

  • multiple areas affected

  • circular in outline and slightly raised

  • size is variably but extensive

• clinical signs begin four to fourteen days after exposure

• zoonotic

Aspergillus (canine and feline)

• nasal aspergillus most common

  • most cases are invasive

• deadliest form is systemic infection (from lungs to other organs)

• chronic nasal discharge with strong odor lasts for weeks to months and does not respond to antibiotics

• typically involves only one nostril

• require extended treatment with toxic side effects

• not zoonotic

Prion Characteristics

• misfolded protein that triggers normal proteins in brain to fold abnormally

  • creates chain reaction resulting in large aggregates of abnormal proteins

• lack genetic material

Chronic Wasting Disease (deer and cervids)

• weight loss, stumbling, listlessness, lack of coordination, drooling, and excessive thirst

• spread among cervids through environmental contamination

• no vaccine or treatment available

• found in 35 US states

• CWD prions in raw, cooked, and cured meat

  • cooking temperatures are well known to be ineffective disabling CWD prions

• zoonotic

Bovine spongiform encephalopathy BSE (bovine)

• first case in mid 1980s

• major outbreak in United Kingdom 1990s

• by 2005 24 countries reported BSE in native cattle

• caused from feeding cattle meat and bone meal with prions from infected cow or sheep

• cause changes in temperament, abnormal posture, incoordination, decreased production, and loss of condition

• 2-8 yr incubation period

• no vaccine or treatment

Creutzfeldt-Jakob Disease (humans)

• classic or variant CJD

• classic

  • older people

  • appear sporadically

  • brain breaks down or stops working normally

  • progresses quickly and is fatal within year

• variant

  • tied to eating beef from cow with BSE

  • younger people

  • mental symptoms and behaviors and pain when touching things

Colibacillosis

• caused by bacterial strains of Escherichia coli

• gram negative

• flagellated bacilli

• rod shaped

• virulence factors

  • encapsulated

  • fimbriae

  • easily adheres to mucosal enterocyte receptors within small intestines

  • rapid colonization

  • certain strains produce enterotoxins

  • local or systemic effects

  • fecal oral route

  • adheres and colonizes onto intestinal wall

• resistant to widespread disinfectants and antibiotics

• lack of effective vaccines due to constant mutation

• occurs in all age groups of chickens but most common in adult layer hens

• high mortality in neonatal piglets with severe watery diarrhea

• shed by healthy pigs

• swine clinical signs

  • anorexia, weight loss, asthenia, cyanosis, diarrhea, edema, fever, hemorrhage, paralysis, sudden death

• poultry clinical signs

  • respiratory distress, anorexia, diarrhea, weight loss, sudden death

• zoonotic - foodborne transmission

Cryptococcus neoformans

• most common systemic fungal disease in cats

• airborne pathogen caused by inhalation of fungi in environment

• found in soil, decaying wood, and bird poop

• clinical signs

  • cutaneous lesions of nose, mucous nasal discharge, weight loss, lethargy, joint inflammation, and neurologic symptoms

• not zoonotic

Porcine Epidemic Diarrhea virus

• enveloped virus

• 95-190 nm single stranded positive sense RNA genome

• spread via

  • fecal oral route

  • fecal nasal route

  • fomites

  • vertical transmission

  • sexual intercourse

• high mortality in neonatal pig, low mortality in post weaned

• only in swine and not zoonotic

Tritrichomonas foetus

• parasite

• causes venereal disease in cattle

• transmission increased by

  • not testing before breeding

  • breeding naturally

  • not treating infected cattle

  • lack of biosecurity

  • commingling breeding groups

• most common sign in cow is reproductive failure due to early embryonic death

• vaccination!

• not zoonotic

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