Vector Borne Diseases

Front 1

Define a vector:

Back 1

invertebrate organism that transmits a microorganism from one vertebrate species (animal reservoir) to another (humans in clinical medicine)

Front 2

Differentiate passive versus active vectors:

Back 2

passive: simply carries microorganism from one species ot next (Aedes mosquitoes and eee) or active (vector plays role in replication, life cycle, and maintenance of microorganism in nature (anopholes mosquitoes and malaria)

Front 3

what afllictions do arthropod vectors transmit?

Back 3

-malaria (anopheles mosquitoes); leishmaniasis (sandflies); trypanosomiasis (glossina-tsetse flies); and chaga's disease (reduviid bugs-kissing beetles)
-vector-borne diseases such as plague, epidemic typhus, african sleeping sickness, and malaria = major impact on world history, human migration, and human genetics (malaria resistance and sickle cell disease)

Front 4

In the US, what are three important arthropod vectors?

Back 4

ticks, mosquitoes, fleas
-other arthropod vectors: deer flies (tularemia) mites; (rickettsialpox) and reduviid bug (Chaga's disease in Texas)

Front 5

Tick-borne diseases: Lyme disease: geographical distribution:

Back 5

-reported in 48 states but three demarcated regions:
1.) seabord areas mass to maryland
2.) upper midwest (Minnesota and wisconsin)
3.) west coast: Cali and oregon

Front 6

What is the vector host?

Back 6

ixodes tick: (tick borne borreliosis: common vector borne disease in the US; tick vector species infected with b. Burgdorferi) ; varies but all closely related:
Ixodes scapularis: Northeast/ upper midwest US
Ixodes pacificus: West Coast of US
Ixodes ricinus: Europe

Front 7

Describe the genus borrelia:

Back 7

-borrelia burdorferi sensu stricto; length = 20-30 um by .3 um wide (7-11 flagella)
-spirochete can be isolated from tissues and body fluids and is isolated from the Ixodes tick/ it can be also grown in tissue culture
B. burdorferi has been isolated from domesticated animals (dogs, cats, horses, cows) as well as in birds

Front 8

Describe the highlights in the Ixodes lifestyle:

Back 8

-tick feeds only once in each stage of life (total of 3 x)
-a larva must feed on effective reservoir host (one that is colonized with spirochetes) to become infectious to humans)
- most common reservoir host is the white footed mouse (Peromyscus leucopus)
-usually nymphal stage that transmits the infection to humans during months of June, July, and August.
-adult tick feeds once in the fall (preferably on deer)

Front 9

Overview of ixodes lifestyle once more:

Back 9

-2 year life cycle of B. burgdorferi in ixodes dammini ticks (depend on horizontal transmission between immature ticks and mice); larval tick is infected in summer when feeds on a mouse carrying the spirochete
-after dormant period, larva emerges as a nymph the next spring, when it again feeds on a mouse and infects it with the spirochete. it is the nymphal stage that usually transmits the infection to humans. nymphs become adults during the summer, feed once in the fall (preferably on deer) and then produce more larvae, which are spirochete free until spring, when cycle begins with larvae feeding on mice

Front 10

two principal determinnats in infection rates:

Back 10

1.) prevalence of ixodes in the area
2.) incidence of ticks infected with the spirochete

Front 11

statistics of lime disease:

Back 11

-lyme disease is the most common vector-borne disease in teh US, with 29,959 confirmed cases
per 100,000 in population, RI: 14.2; Delaware = highest rate: 111.2/ 100,000

Front 12

What is stage 1 of lime disease?

Back 12

-median duration of 4 weeks and includes definitive skin lesion of Lyme disease, Erythema migrans (as well as numerous other nonspecific manifestations)

Front 13

Erythema migrans: occurs in what time frame?

Back 13

-between 3 and 32 days after the tick bite (median 7 days)
-fewer than 50% of people recall tick or bite
-lesion may be anywhere (thigh, groin, axila most common)
-begins as a macule/papule then expands with red to bright red outer borders with partial central clearing; hot but painless
-median diameter = 15 cms (range of 3-68 cms)

Front 14

What are the cutaneous signs and symptoms of lyme disease?

Back 14

-flu-like syndrome with malaise, chills, fatigue, low grade fever
-neurologic symptoms: headache, photophobia, stiff neck
-migratory arthralgias, myalgias

Front 15

Describe the pathogenesis of stage I:

Back 15

-as the ixodes tick bites, the spirochetes move from midgut to salivary glands, and the tick regurgitates or salivates spirochetes into the wound. The tick needs to be attached for at least 24 hours; in order to transfer enough spirochetes to cause disease; once spirochete enters skin, it moves centrifugally away from bite wound (rash enlarges centrifugally)
-as spirochete enters bloodstream it can seek new skin sites (secondary lesions) and can be detected in CSF in early stage

Front 16

Describe Stage II lyme disease:

Back 16

-occurs weeks to months after initial tick bite; it includes nervous system, cardiac, musculoskeletal, and opthalmologic involvement

Front 17

Describe nervous system involvement in stage II lyme disease: (there are two components)

Back 17

1.) aseptic meningitis : headache, nausea, neck stiffness; CSF shows lymphocytic pleocytosis
2.) neuritis: bell's palsy (7th nerve) is the most common clinical sign of neurologic lyme disease and develops in up to 50% of patients with frank meningitis
-peripheral neuropathies and plexopathies can also occur, as well as radiculopathies and other cranial nerve involvement (3,4,5)

Front 18

Describe cardiac involvement in stage II lyme disease:

Back 18

-can cause myopericarditis, varying degrees of atrioventricular block from first degree to complete heart block

Front 19

Describe eye involvement in stage II lyme disease: (there are two components)

Back 19

conjunctivitis, iritis, and optic neuropathy are uncommon

Front 20

Describe stage III of lyme disease:

Back 20

-consists of frank arthritis and late neurologic complications

Front 21

What are the arthritic features of stage III lyme disease?

Back 21

1.) arthritis
a.) musculoskeletal pain:
may involve tendons, bone or muscles. They can be migratory and relapse intermittently for years.
b.) frank arthritis: occurs in 60% of untreated stage I patients. consists of recurrent monoarticular or asymmetric pauciarticular arthritis primarily of the large joints (rarely symmetrical joint involvement)
-knee is most frequently involved with heat and swelling but little pain
-JOINT FLUID: WBC ranges from 500-100,000/mm with PMN predominance

Front 22

describe the neurologic involvement in stage III lyme disease: (3 aspects)

Back 22

1.) neuropsychiatric symptoms
2.) focal CNS lesions (looks like MS or transeverse myelitis)
3.) incapacitating fatigue

Front 23

Diagnosis of lyme disease: 2 steps: (what is problem with the first test?) ; what is a third separate test?

Back 23

1.) ELISA (problem is that stage I serologic tests will be negative in up to 65% of patients; IgM response may not peak for up to 3-6 weeks; IgG may take months to peak)
2.) western blot for verification diagnose false positives or equivocal results ;;;

*THIRD TESTS: PCR (for synovial fluid/ and urinary antigen test but not accurate for diagnosis alone)

Front 24

Treatment of Lyme disease:

Back 24

1.) stages I and II: oral doxycycline 100 mg poq 12 hrs for 2-3 weeks or amoxicillin 500 mg q 8 hrs for 2-3 weeks
other alternative: cefuroxime axetil (no use doxycycline under 8 years of age)

-meningitis: IV pencicillin G: 20 million units in four doses daily for 2-3 weeks or IV ceftriaxone: 2 grams q 24 hr for 2-3 weeks;

Front 25

What is lyme disease prophylaxis?

Back 25

-a singel dose of 200 mg of oral doxycycline ;

Front 26

Name two lyme disease insecticides:

Back 26

-1.) DEET: concentration of 30% 1 to several hours
2.) permethrin: 1% : use only on clothes; hours and days:

Front 27

name the two genera and three clinical syndromes of ehrlichiosis:

Back 27

two genera: ehrlichia and anaplasma
three clinical syndromes:
1.) HME (from ehrlichia chaffeeensis);
2.) human anaplasmosis (human granulocytic ehrlichiosis) from anaplasma phagocytophilum
3.) ehrlichiosis ewingii from ehrlichia ewingii

Front 28

What are vectors for the three syndromes of ehrlichiosis:

Back 28

1.) lone star tick amblyomma americanum for both HME and ewingii
2.) deer tick/black leged tick ixodes scapularis and wetern black legged tick ixodes pacificus for HGE

Front 29

What are the animal hosts for three syndromes of ehrlichiosis?

Back 29

1.) white-tailed deer, dogs, foxes, wolves, coyotes for HME and Ewingii
2.) white footed mouse and other mammals for HGE

Front 30

What cells are infected for the three ehrlichiosis syndromes:

Back 30

HME: monocytes
HGE: neutrophiles
ewingii: neutrophils

Front 31

What is the location and reported cases for the three syndromes of ehrlichiosis? What season are the ticks most active?

Back 31

HME (>1500) and ewingii (8): southeastern, southcentral, mid-atlantic
HGE (1700): west and Europe

Front 32

Describe lab diagnosis for the three syndromes of ehrlichiosis:

Back 32

HME and HGE: PCR and serology
Ewingii = only PCR

Front 33

describe organisms of ehrlichiosis:

Back 33

-small, obligate intracellular bacteria of 0.5-1.5 micrometers in length shape from cocci to coccobacilli

Front 34

Describe the clinical findings for ehrlichiosis: and lab abnormalities

Back 34

-fever, headache, myalgias, rash in only a MINORITY
-lab abnormalities: leukopenia with left shift, thrombocytopenia, anemia, and mild to moderate elevations of SGOT, SGPT, LDH, and ALK phos.

Front 35

What is median duration of disease and when is hospitalization required for ehrlichiosis? What organs are primarily affected

Back 35

-date of onset until recovery is three weeks;
-only in complications including DIC, renal failures, seizures
-organs: liver, spleen, bone marrow, lymph nodes

Front 36

Diagnosis of ehrlichiosis: What do you see in a peripheral blood smear?

Back 36

morulae in circulating peripheral blood cells;

Front 37

Diagnosis of ehrlichiosis: What is IFA used for?

Back 37

indirect fluorescent antibody is used to detect Ehrichiosis chaffeensis antigen: positive if four fold increase in antibody titer/ (1:64); four fold increase in a. phagocytophilum: (1;80) minimum

Front 38

Therapy for ehrlichiosis: drugs;

Back 38

drug of choice: doxycycine: 100 mg po BID for 10 days; doxycycline also used in children with moderate to severe disease; otherwise rifampin 300 mg BID can be used

Front 39

What is babesiosis?

Back 39

infection caused by protozoan parasite babesia; (babesia microti): (intra-erythrocytic phase)

Front 40

How is babesia microti disseminated? where?

Back 40

-via bite of ixodes scapularis ; in summer; / coast new england; called Nantucket fever; /

Front 41

What is the reservoir for parasite babesia microti?

Back 41

white footed mouse!

Front 42

What is the clinical presentation of babesiosis?

Back 42

-most cases = asymptomatic:
-severe and life-threatening infections occur
MILD CASES = myalgia, malaise, low grade fever and chills, fatigue, nausea, headache
-SEVERE: jaunice, DIC, ARF, RF

Front 43

Diagnosis of babesiosis:

Back 43

--> MICROSCOPIC IDENTIFICATION ON THIN GIEMSA STAINS: harder to appreciate thick smear / difficult to distinguish from plasmodium falciparum

Front 44

treatment of babesiosis:

Back 44

most recover w/o treatment. those with moderate-severe illnesses clindamycin IV or PO and oral quinine for 7-10 days

alternate: atovoquone + azithromycin (fewer side effects)

Front 45

What are other names of tularemia and what bacteria is it caused by?

Back 45

-rabbit fever or deerfly fever; caused by gram negative bacillus Francisella tularenis

Front 46

How is francilsella tularenis transmitted?

Back 46

-handling or ingestion of infected rabbits or rodents;
-infectious aerosols from animals
-animal bites
-transmission by arthropod vectors (Dermacentor variablis (dog tick) and deerflys:

Front 47

Where is francisella tularnis (tularemia) endemic?

Back 47

central and western parts of the US: higher in the summer;

Front 48

Why is tularemia now considered a bioterrorism agent?

Back 48

-b/c high mortality rate of 15% : from pulmonary and typhoid form

Front 49

What are four clinical syndromes of tularemia and incidence of each?

Back 49

1.) ulceroglandular (75-85%)
2.) typhoidal (5-15%)
3.) oculoglandular (0-5%)
4.) pulmonary (7-10%)

Front 50

Describe ulceroglandular tularemia:

Back 50

-primary cutaneous lesion with regional lymphadenitis with fever, chills, and hepatosplenomegaly

Front 51

Describe typhoidal tuleramia:

Back 51

by ingestion; fever, chills, weight loss; hepatosplenomegaly and abdominal pain

Front 52

describe oculoglandular tularemia:

Back 52

aerosol inoculation to the eye

Front 53

describe pulmonary tularemia:

Back 53

-by inhalation; non-productive cough with bilateral patchy infiltrates

Front 54

How do you diagnose tularemia?

Back 54

--> based on clinical presentation b/c gram stain not seen and culturing is biohazard/ need special media and serologic assays

Front 55

Treatment of tularemia:

Back 55

--> aminoglycosides (streptomycin and gentamicin):
-tetracycline, chloramphenicol, and ciprofloxacin

Front 56

What is rocky mountain spotted fever caused by?

Back 56

-rickettsia rickettsii during summer months:

Front 57

-What is rickketssia rickettsii (describe features); how is it transmitted/

Back 57

-obligate intracellular pathogen: -transmitted by dermacentor variabilis tick dog tick; prolonged contact of several hours is needed;

Front 58

What are clinical findings of RMSF:

Back 58

-only 3% have classic triad of fever, rash, and tick bite history
-incubation period of 3-12 days (average of 7 days); abrupt onset of high fever, headaches, malaise, myalgias, and 1-2 days following with a rash (erythematous and macular involving ankles and wrists and spreading to palms, soles, trunk, and face:

Front 59

What percent of lesions of RMSF become petechial?

Back 59

50%

Front 60

describe the pathogenesis of RMSF with the rickketssia?

Back 60

-rickettsia invade endothelial cells causing necrotizing small vessel vascultiis. this produces characteristic skin rash.

Front 61

Describe the diagnosis of RMSF:

Back 61

specific PCR of blood or skin available as is an IFA serology;
-many patietns present with hyponatremia and thrombocytopenia;
-30% of patients present with lymphohistiocitic meningitis. LFT's may be elevated

Front 62

Treatment of RMSF:

Back 62

-doxycycline for 7-10 days ; chloramphenicol if patient is ill.

Front 63

What are other tick borne diseases in the US: (5)

Back 63

1.) tick paralysis (neurotoxin released in saliva of dermacenter andersoni wood tick)
2.) powassan viral encephalitis
3.) colorado tic fever (dermacentor andersoni);
4.) tick borne relapsing fever (borrelia recurrentis spirochete)
5.) Q fever: transmitted by aerosol ;

Front 64

What are the 5 tick borne diseases discussed?

Back 64

1.) lyme disease
2.) ehrlicchiosis
3.) babesiosis
4.) tularemia
5.) RMSF

Front 65

What are mosquito borne viral diseases?

Back 65

see arthropod borne lecture!

Front 66

What are two fleaborne zoonoses?

Back 66

1.) plague
2.) endemic typhi

Front 67

How is plague tarnsmitted?

Back 67

-gram negative coccobacillus Yersinia pestis as a result of rat flea xenopsylla cheopis /

Front 68

Describe the pneumonic plague:

Back 68

potentially lethal disease transmitted from person to person, leading to epidemics and making it useful for bioterrorism
a.) highly infectious by aerosol
b.) highly lethal
c.) person-person spread
d.) difficult to treat once symptoms manifest themselves
e.) no effective vaccine in use

Front 69

When was the last epidemic of the pneumonic plague:

Back 69

Surat, India in 1994

Front 70

When do patients evelop febril acute ulcerglandular syndrome after flea bite:

Back 70

2-8 days after

Front 71

What are teh suppurative lymph nodes of plague called?

Back 71

-bubos/

Front 72

What is septicimic plageu?

Back 72

-untreated bacteria seeping into bloodstreaming, resulting in pneumonia; sputum is bloody and chest XRAY does no thelp distinguish this from other types of pneumonias:

Front 73

How do you diagnose plague?

Back 73

-gram stain of lymph node aspirate, sputum or bood; cultured from blood or lymph nodes;

Front 74

Treatment for plageu:

Back 74

-aminoglycosies such as strep or gentamicin;
-alternatives: doxycycline and ciprofloxacin or chloramphenicol;
-

Front 75

What is endemic typhus:

Back 75

-murine typhus; caused by rickettsial species R. typhi; spread by bite of rat fleas and cat fleas; endemic to texas and southern california