Zoonosis

Definition: diseases which are transmitted from vertebrate animals to man

Classification: by nature of the pathogen, mode of transmission, geographic range of host, which animal host is infected, or by clinical syndrome

Animal bites

Infectious organisms: from hosts own skin flora or animal’s oral flora: pasteurella moultocida, group A strep, Streptobacillus moniliformis, spirillum minor, agents of rat bite fever, Tularemia

Dog bites: Capnocytophagia canimorsus

Cats: pasturella multocida, Q fever

Birds: psittacosis

Other agents: rocky mountain spotted fever, tularemia, plague, brucelosis, leptospoirosis, anthrax

Symptoms associated with Disease

Neurologic: encephalitis, meningitis, cranial nerve neuropathies, myelopathy, peripheral neuropathy

Zoonotic respiratory infections: can mimic atypical pneumoniae

Lyme disease: Bell’s palsy and peripheral neuropathy

Encephalitis: toxoplasmosis, brucellosis, cat-scratch disease, literiosis, leptospirosis, lyme disease, relapsing fever, murine typhus, Q fever, rabies, rocky mountain spotted fever, psittacosis

Meningitis: brucelosis, C. canimorsus, listeriosis, plague, salmonellosis, leptospirosis, tularemia, lyme disease, relapsing fever, ehrlichiosis, Q fever, Rocky Mountain Spotted fever, psittacosis, arbofiral disease

Rash: maculopapular, crepitant, gangrenous, petechial, purpuric

Erytehma chronica migrans (erythematous, annular plaque with central clearing occurring 2-20 days after a tick bite) Þ Lyme disease

Rocky mountain Spotted Fever: maculopapular rash begins on extremities (wristis, ankles) spreads centripetally Þ petechiae Þ skin necrosis or gangrene

Skin lesion	Bug
Maculopapular	Cat scratch fever, colorado tick fever, leptospirosis, lymphocytic choriomeningitis, psittacosis, rocky mountain spotted fever, reckettsial infections, rat bite fever, relapsing fever, salmonellosis
Crepitant or gangrenous lesions	Aeromonas, capnocytophagia canimorsus, vibrio vulnificus
Petechial and purpuric lesions	Viral hemorrhagic fevers (dengue, yellow, ebola, lassa), rocky mountain spotted fever, rickettsia prowazekii, rat bite fever (Streptobbacillus moniliformis), relapsing fever, capnocytophagia canimorsus
Local eschar	Rickettsial infections
Local skin lesion with lymphadenitis	Cat scratch fever, rat bite fever, tularemia

Ehrlichia Chaggeensis – Ehrlichiosis ("spotless Rocky Mountian Spotted Fever")

Agent: rickettsiaceae: small, nonmotile, pleomorphic gram negative obligate intracellular parasites

Ehrlichia found within cytoplasmic vacuoles (not cytoplasm) organisms remain sequestered in phagosomes of leukocytes

Morulae: leukocytic inclusions

Pathogenesis: infects circulating leukocytes,

Transmission: arthropod vectors amblyomma americanum, lons star tick

Manifestations: nonspecific, self-limited febrile illness

Symptoms: rigors, malaise, fatigue, nausea, vomitting, diarrhea, abdominal pain, petechial rash

Lab: leukopenia, absolute lymphopenia, thrombocytopenia, anemia, hepatic aminotransferasis Ý ,

Differential: RMSF, tularemia, lyme disease, babesosis, Colorado tick fever, meningococcemia, viral hepatitis, enteroviral, influenza, Q fever, collagen vascular disease, leukemia

Diagnosis: clinically, anti-ehrlichial IgG antibodies (within first 3 weeks of illness)

Mulberry-like intraleukocytic inclusions: peripheral blood, bone marrow, CSF

Treatment: tetracycline

Francisella tularensis (Tularemia) – Pasteurella tularensis: small, gram negative non-motile coccobacillus

Type A: nearctica, found in rodents and blood sucking arthropods

Type B: palaearctica: water and aquatic animals

Epidemiology and host factor: found throughout the northern hemisphere, Over 100 species are host (ticks and rabits)

Who: Hunters and their families, muskrat trappers, when: summer (ticks) and winter (rabbits)

Manifestations: EXTREMLY INFECTIVE (10-50 bacilli adequate to cause disease)

Portals of entry: skin or mucous membranes

Arthorpod vector: tick

Incubation: 1-14 days

Progression: tick biteÞ skin papule at site of entry Þ ulcer with systemic symptoms (fever, lymphadenopathy) Þ bacteremia

Symptoms: fever, chills, malaise, fatigue. Clinical syndromes:

Ulceroglandular (75-85%): ulcerated skin lesion dvelops at site of inoculation with painful regional lymphadenopathy
Oculoglandular: (2%) unilateral painful purulent conjunctivits with preauricular or cervical lymphadenopathy
Typoidal: (5-15%) fever weight loss, sever malaise without lymphadenopathy

Diagnosis: rarely seen on gram stain, cultures usually negative (labs don’t want to culture because so infective).

Serology: Ý in agglutination or microagglutination titers

Treatment: streptomycin, gentamicin

Babesia – Babebiosis: febrile illness assoc/ hemolysis and hemoglobinuria

Agent: malaria-like protozoa that infects erythrocytes

Growth and identification: over 70 species 3 cuase disease: B. divergens. B. bovis. B.microti. found in erythrocytes (may be mistaken for Plasmodium falciparum

Epidemiology and host factor: northeastern coastal US

Vector: Ixodes dammini (also responsible for lyme disease)

Clinical manifestations: majority of infections are subclinical

Symptoms: non-specific and gradual: malaise, fatigue, anorexia, rigors, fever, headache, myalgias, arthralgias, nausea, vomiting, abdominal pain, depression, emotional lability, dark urine, cough sore throat, conjunctivall injection, photophobia, rash similar to erythema chronica migrans (lyme disease), petechiae, splinter hemorrhage. NO lymphadenopathy

Labs: hemolytic anemia, ß serum haptoglobin Ý reticulocyte counts, positive direct coombs test, Ý BUN, creatinine, transaminases, bilirubin, alk phos

Host defenses: spleen crucial, also complement activation, mac produced mediators (IL1, TNF)

Diagnosis: microscopic exam (Giemsa or wright stain), indirect immunoflourescent antibody

Treatment: recover without specific therapy, for severe infection clindamycin, oral quinine

Leptospira (leptospirosis) – generalized vasculitic disease caused by spirochetes of Leptospira

Identification: finely coiled, motile spirochetes with hooked ends. > 170 serotypes

Epidemiology: worldwide (Hawaii)

Transmission: contact with infected animal via water or soil

High risk patients: agricultural laboreres, abattoir workers, poultry, fish processors, sewer workers, butchers, soldiers

Source of infection: rats

Manifestations: subclincical (90%) mild

Weil disease (10%) severe disease with jaundice: jaundice, renal insufficiency, oliguria, purpura, petechiae, hemorrhagic diathesis Þ hepatocellualr dysfunction without necrosis (liver recovers after infection)

Pathogenesis: penetrate mucous membrane Þ bloodstream Þ spinal fluid and eye a biphasic course

Symptoms: flu like with abrupt onset of fever, chills, headache, severe myalgias, malaise, prostration, abdominal pain, nausea, vomiting

Conjunctival suffusion (conjunctivitis with pus and exudate not present)

Labs: direct bilirubin < 20mg/ml, alk phos Ý , Ý serum creatinine phosphate

Poor prognostic factors: age, renal insufficiency jaundice

Diagnosis: isolation of organism: darkfield examination

Serology: PCR, ELISA

Treatment: IV penicillin, ampicillin, or oral doxycycline, ampicillin or amoxicillin