Chapter 17: Infectious Diseases 225
Shigellosis
General
Shigellosis refers to a group of bacteria called Shigella,
whichisknowntocausedysentery.Dysenteryisaclinical
syndrome that consists of fever, abdominal cramps, and
diarrheamixedwithbloodandmucus.Dysenterycanbe
causednotonlybytheenteroinvasivebacteriumShigella,
butalsootherenteroinvasivebacteria(Salmonella enteriti-
dis, Campylobacter jejuni, Clostridium difficile, Yersinia
enterocolitica)orparasitessuchasEntamoeba histolytica.
16
There are many different groups of Shigella bacteria
thatcausediarrheainhumans.Theserogroupsconsistof
A,B,C,andD.WhileShigella sonnei(serogroupD)isthe
causeofmorethantwo-thirdsofmildercasesintheUnited
States,itisthemoreaggressiveShigella dysenteriaetype1
(serogroup A) that has been responsible for deadly epi-
demicsinmanydevelopingcountries.
16,18
Childrenappeartobeatgreatrisknotonlyforinfection
but also from complications including death. Data sup-
portedbytheWorldHealthOrganizationputthenumber
ofannualcasesbetween1966and1997at165million,of
which69percentofcaseswereinchildrenyoungerthan
5yearsofage.Theprominentoccurrenceinchildrencan
alsobeseenintheUnitedStates,wheremostoftheesti-
mated 14,000 annual cases occur in children aged 2–4
years.Thegreaterincidenceinchildrenislikelyareec-
tionofthefecal–oralrouteoftransmissioninhumans.
16,18
Patients with the milder infection are likely to recover
withoutantibiotictherapy.Inpatientswhodorequireanti-
biotictherapy,considerationshouldbegiventoincreasing
the incidence of antibiotic resistance.
Signs, Symptoms, and Diagnosis
ThehumandigestivetractisthemainreservoirofShigella.
Therefore,apatientmaybeasymptomaticbutabletotrans-
mittheinfectiontoothers.Theperson-to-persontransmis-
sionismosteffectiveviathefecal–oralroute,butinfection
can also occur through drinking contaminated water or
consumingcontaminatedfood.Fliescanalsotransmitthe
infectionbybreedingincontaminatedfecesandthenland-
ingonfoodpreparationsurfacesoronfooddirectly.
The typical incubation period is 1–4 days. Symptoms
typicallybeginabruptlywithnausea,vomiting,bloodydiar-
rheamixedwithmucus,highfever,abdominalcramps,and
headache.Intheabsenceofcomplicationsandpreexisting
health conditions and in milder cases caused by Shigella
sonnei(serogroupD),diarrheatypicallyresolvesafter5–7
days.
16,18
A diagnosis of shigella is sometimes based on
presentingsignsandsymptomsorwhenknowncasesclus-
tertogetherinlocationssuchasadaycarecenterorcruise
ship.Diagnosisconrmationmaybewarranted,suchasin
initial or isolated cases and in persistent or unresponsive
diarrhea.Inthesesituationsidenticationoftheorganism
in the stoolcan aidin thediagnosis. Stoolcollection can
alsoaidinsuspectedantibiotic-resistantcases.
Management
Mildcasestendtoresolvewithsupportivemeasures,such
as oral uids and rest. In cases where more aggressive
management is warranted, antibiotics are the mainstay
(ciprooxacin,trimethoprim–sulfamethoxazoleorceftriax-
one).
16,18
Insuspectedcasesofantibioticresistance,nd-
ingsfromthetestingofstoolculturesshouldbeusedto
determinethemosteffectiveantibiotictherapy.
Antidiarrhealagentssuchasloperamide(Imodium)or
diphenoxylatewithatropine(Lomotil)aretobeavoided
because they may prolong the duration of symptoms or
increase the likelihood of complications. Complications
arenotonlymorelikelytodevelopincasescausedbythe
moreaggressiveShigella dysenteriaetype1(serogroupA),
but also in patients with preexisting health conditions,
suchaschronicrenalfailureorimmunosuppression.Com-
plications include metabolic disorders (hypoglycemia,
hyponatremia), intestinal perforation, bacteremia, hemo-
lytic uremic syndrome, and toxic megacolon.
16
Reactive
arthritis that lasts from months to years has been docu-
mentedin2to3percentofthoseinfected.Thedevelop-
mentofreactivearthritistendstooccurinthosewiththe
HLA-B27antigenandresultsinarthritisinjoints,ocular
irritation,andurethritissymptoms(Reitersyndrome).
16,18
Lifestyle Changes: Practical Tips for Your
Patients
Patients should be encouraged to practice regular
hand washing with soap, especially in facilities where
alargenumberofpeoplecongregate(daycarecenters,
cruise ships, institutions, etc.). Patients should be
encouraged to follow local authority recommenda-
tionsregardingswimminginarealakes,rivers,orsea-
side communities that are exposed to raw sewage.
Regardlessofrecommendations,swallowingwaterin
suchsettingsshouldbeavoided.
Lyme Disease
General Characteristics
Lyme disease, as it later became known, was rst recog-
nized in 1976 when a cluster of children in Lyme, Con-
necticut, presented with arthritic-like symptoms initially
thoughttobe juvenilearthritis.It wasn’tuntil1982that
thespirochete-likebacteriumBorrelia burgdorferi was iso-
latedasthecauseofthismultisystemillnessthatcommonly
affectstheskin,nervousandcardiovascularsystems,and
joints.
Cases in the United States tend to occur more com-
monlyinthenortheastandnorthcentralareaswherethe
black-leggedtick(ordeertick)ismorecommon.Ticksof
the Ixodes ricinuscomplex,suchastheblack-leggedtick,
arethevectorforLymedisease.Otherticks,suchasthe
lonestartick(Ambylomma americanum)andAmericandog
tick (Dermacentor variabilis), are not known to transmit
Lymedisease.
19
Theblack-leggedtickhasthreelifestages:larvae,nymph,
andadult.Itisduringthenymphstagethatthetickismost
likelytotransmitdiseasetohumans.
20
Althoughsymptoms
ofLymediseasecanpresentacutely,noteveryonewhois

Get Patient Education: A Practical Approach, 2nd Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.