vector borne infections

Question 1

characteristics of vector borne diseases?

Answer 1

• transmission by live agents: usually arthropods/insects
• potential for rare transmission by other routes: blood transfusion, organ transplantation
• areas of endemicity restricted by the vector
• control of the vector may allow control of disease

Question 2

what does “areas of endemicity restricted by the vector” mean

Answer 2

sometimes, there is a major vector but also other vectors that do not act as efficiently in transmission, vectors may be potential if they exist but do not transmit the infection as the infecting agent is not present in the population

Question 3

transmission by live agents can happen two ways…

Answer 3

mechanical = passively carrying organisms ex. on feet
biological = organism lives within the vector

Question 4

what disease is popular in ns?

Answer 4

lyme disease, others that may exist but are not common are anaplasma and babesia
- there are vectors present here that could transmit infection but have NOT yet ex RMSF or WNV

Question 5

what is an example of a key vector?

Answer 5

ixodes scapularis = black legged tick (BLT)
- requires a blood meal at each stage of maturation for females
- found in multiple places in canada

Question 6

how did lyme disease begin?

Answer 6

first found in lyme, connecticut in 1975, now common in canada and us
- caused by borrelia burgdorferi, a gram negative spirochete
- transmitted by ixodes ticks

Question 7

how do ticks transmit lyme disease?

Answer 7

antigenic changes in the organism occur when the tick bites a host, 24-36 hours of attachment is needed for transmission
- nymphs and adults are the stages of tick involved in transmission

Question 8

what causes lyme disease?

Answer 8

borrelia burgdorferi, a gram negative spirochete

Question 9

clinical presentations of lyme disease?

Answer 9

• early localized disease (3-30 days after bite): 80% will develop a bulls eye rash “erythema migrans”, may be “flu like illness” but no resp or gi components
• early disseminated disease
  multiple em lesions, neurological or cardiac disease
• late disease
  arthritis esp of the knee, may be neurological symptoms

Question 10

bulls eye rash is called

Answer 10

erythema migrans

Question 11

diagnosis of lyme disease

Answer 11

• many do not remember tick bite
• ## early localized disease is diagnosed clinically, serology positive after several weeks

Question 12

serology for lyme disease looks at…

Answer 12

IgM/IgG levels
- enzyme immuno assay / western blot used or 2 sequential rapid tests

Question 13

serology for lyme disease is used only…

Answer 13

for early and late disseminated disease and it should not be used for asymptomatic people, people with non specific symptoms, or when only em is present bc it is insensitive

Question 14

treatment of early lyme disease…

Answer 14

• prophylaxis is used after tick bites in high prevalence areas (doxycycline)
  early disease: amoxicillin, doxycycline, cefuroxime, are all effective for up to 3 weeks

Question 15

treatment of late lyme disease or neurological disease

Answer 15

neurological disease: ceftriaxone, or penicillin or doxycycline for up to 28 days
- late lyme disease symptoms may persist after treatment: additional antimicrobials are not beneficial and long courses are not useful

Question 16

babesiosis is

Answer 16

an apicomplexa parasite related to malaria (plasmodium)
- transmitted by ticks (ixodes scapularis), no person-person spread
- takes 24-36 hours of attachment after transmission
- lives in red blood cells in humans and causes anemia, fever, hemolysis and more severe disease can occur if no spleen, old, very young, or immunosuppressed

Question 17

babesiosis transmission facts …

Answer 17

normally found in mice that then infect ticks
- takes about 24-36 hours of attachment for transmission
- common in new england, nj, and minnesota
- rarely transmitted in blood or transplanted organs

Question 18

how does babesiosis infect

Answer 18

• organism comes from tick and when the tick bits and transmits the organism, the organism lives in the red blood cells and causes damage (anemia), causing fever and the blood cells break open causing hemolysis

Question 19

clincial of babesia

Answer 19

infection can cause symptoms ranging from asymptomatic to severe (resp distress, disseminated intravascular coagulation)

Question 20

diagnosis of babesiosis

Answer 20

blood smear most common - resembles plasmodium falciparum (malaria) but smaller
- detection of parasite DNA by pcr: very sensitive
serology tends to be after acute phase of infection (can be used for screening blood donations)

Question 21

treatment for babesiosis

Answer 21

antimicrobials are effective

Question 22

anaplasma is

Answer 22

anaplasma phagocytophilum (common in phagocytes) transmitted by ixodes ticks
- gram negative obligate intracellular (has to be inside cells) bacteria, related to lack genes to make peptidoglycan (why it cant survive outside of cells)
- rarely transmitted by blood transfusion or organ transplant

Question 23

where is anaplasma seen

Answer 23

in NS, distribution similar to lyme disease
- tends to occur in summer and early fall
- incidence of disease increases with age
- infects granulocytes (pus cells) and grows in their cytoplasm
- forms masses of organisms that are seen as inclusions
- as it infects wbc, may cause immunosuppression of the host

Question 24

clinical manifestations of anaplasma

Answer 24

symptoms of anaplasmosis are variable:
- fever, headache, muscle aches, malaise, cough, abdominal pain
severe: resp distress, bleeding, renal failure (seen most in immunocompromised)

Question 25

detection of anaplasma

Answer 25

early in illness NAAT testing or PCR is sensitive, but rarely presents early - inclusion in granulocytes may be seen in up to 60% in first week - serology is the mainstay of diagnosis

Question 26

treatment of anaplasma

Answer 26

doxycycline for all ages prevention: tick avoidance

Question 27

q fever is caused by

Answer 27

coxiella burnetti - small gram negative rods that are intracellular pathogens

Question 28

q fever transmission

Answer 28

- has a large actively growing form and a small dormant form pathogens of goats/sheep/cattle/cats/dogs - transmitted to humans by aerosols and rarely by ticks - large numbers of the organism are present in the placenta and associated with fluids released when the infected host (commonly animals giving birth) gives birth

Question 29

coxiella clinical disease:

Answer 29

flu like illness w fever - most common - pneumonia - hepatitis - chronic infection, esp endocarditis - comps in pregnancy

Question 30

diagnosis for q fever

Answer 30

serology

Question 31

treatment for q fever

Answer 31

doxycycline and trimethoprim sulfamethoxazole are used post q fever fatigue syndrome has been recognized

Question 32

rickesttsial disease found by

Answer 32

dr howard taylor ricketts, he described the agent for rocky mountain spotted fever

Question 33

rocky mountain spotted fever is

Answer 33

rickettsia rickettsii, tiny gram negative bacteria, intracellular and tick borne - spotted fever group grow intracellularly in vascular endothelium and smooth muscle - damage leads to rash, many species

Question 34

rickettsia transmitted by

Answer 34

between ticks by transovarially route (from birth) and sexually infection in ticks - reservoir and vector (dog tick - dermacentor variabilis)

Question 35

clinical features of RMSF

Answer 35

incubation period is 5-10 days - initial flu-like illness - subsequent development of abdominal pain and joint pain, diarrhea, cutaneous gangrene (tissue death) - rash 3-5 days after fever, initially macular but become raised and papular, soles/palms (15% have no rash) - may be rapidly fatal if G6PD deficiency (esp old men of african descent in US)

Question 36

epidemiology of RMSFl

Answer 36

distributed widely over US and southern canada - not in ns - found in latin america - seasonal distribution influenced by vector age range may reflect contact w vector - young predominant

Question 37

lab findings of RMSF

Answer 37

present w low platelets, low sodium, liver enzymes increased, wbc normal confirmatory diagnosis is slow so treatment will happen quick if RMSF is possible - IFA used for serological diagnosis - immunohistochemistry may be used on biopsies or special staining

Question 38

other rickettsia ...

Answer 38

can cause severe, potentially fatal disease - rare, not endemic to canada ex. louse borne typhus wiped out napoleon's grande armee which was a type of rickettsia - tends to occur in conc camp environs, war, natural disasters ex. murine typhus - occurs worldwide, reservoir in rats, less sever than other typhus

Question 39

tularemia is caused by

Answer 39

francisella tularensis small gram negative coccobacillus - occurs as infection of wild rabbits/rodents or transmitted by ticks (dog ticks) - can also be acquired by handling infected carcasses, eating and inhaling dust no person to person transmission - endemic to canada

Question 40

clinical tularemia

Answer 40

most common type: ulceroglandular - 2-5 days, papule at site of inoculation, forms a tender small ulcer and scab (can also have no ulcer "glandular" - painful lymphadenopathy, fever, headache, myalagia, malaise, cough - can last for several weeks - may progress to sepsis, pneumonia, meningitis, can be fatal

Question 41

diagnosis of tularemia

Answer 41

culture from blood or discharge - gram stain is very small and pale - easily missed - immunofluorescence, pcr, serology (after recovery)

Question 42

treatment of tularemia

Answer 42

streptomycin or doxycycline prevention: avoid ticks and gloves for trappers

Question 43

recommended method for tick removal from cdc

Answer 43

1. wear gloves or protect skin with tissue 2. grasp tick with fine forceps as close to the skin as possible 3. apply gentle pressure w out twisting or crushing 4. wash hands and the area w soap or water 5. keep the tick for id to determine the risks