Download Parasitic Diseases

Parasitic Diseases
Parasitic Diseases
 PROTOZOAL DISEASES
 HELMINTHIASE
Malaria
 Malaria is caused by obligate intracellular protozoa
of the genus Plasmodium
 Plasmodium including P. falciparum, P. malariae, P.
ovale, and P. vivax
 Plasmodium has a complex life cycle
 Asexual phase (schizogony) in humans
 sexual phase (sporogony) in mosquitoes
 Erythrocytic phase of Plasmodium:
 Merozoites released from schizonts in the liver
penetrate erythrocytes
 When inside the erythrocyte, the parasite transforms
into the ring form
 Ring form which enlarges to become a trophozoite
 Ring form and trophozoite can be identified with
Giemsa stain on blood smear
 Transmission:
 Anopheles mosquitoes female
 Blood transfusion
 Contaminated needle
 transplacentally to a fetus
Epidemiology
 Malaria is an important cause of fever and morbidity
in the tropical world
 Infected foreign civilians from endemic areas who
travel
 Citizens who travel to endemic areas without
appropriate chemoprophylaxis
Clinical Manifestations
 The incubation period ranges from 6 to 30 days
depending on the Plasmodium species
 The most characteristic clinical feature of malaria is
febrile paroxysms
 The classic symptoms of the febrile paroxysms of malaria
include high fever, rigors, sweats) and headache
 Paroxysms coincide with the rupture of schizonts that
occur:
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Every 48 hours with P. vivax and P ovale (tertian periodicity)
Every 72 hours with P. malariae (quartan periodicity)
 Short-term relapse→recurrence of symptoms after a
primary attack due to the survival of erythrocyte
forms in the bloodstream
 Long-term relapse→renewal of symptoms long after
the primary attack due to release of merozoites from
an exoerythrocytic
 Long-term relapse occurs with:

P vivax and P. ovale because of persistence in the liver

P malariae because of persistence in the erythrocyte
 Distinctive physical signs may include:
 splenomegaly (common)
 Hepatomegaly
 pallor due to anemia
Laborarcry and Imaging Studies
 The diagnosis of malaria→stained smears of
peripheral blood
 In nonimmune persons, symptoms typically occur 1
to 2 days before parasites are detectable on blood
smear
 Obtaining smears several times each day over 3
successive days
 Both thick and thin blood smears should be
examined
multiply infected erythrocyte containing
signet-ring P. falciparum trophozoites
,
Treatment
 Oral chloroquine is the recommended treatment
except for chloroquine-resisranr P. falciparum
 Quinine sulfate plus tetracycline, quinine plus
pyrimethamine-sulfadoxine, or mefloquine are used
for chloroquine-resistant malaria
 Quinidine gluconate is used for parenteral treatment
Complications and Prognosis
 Cerebral malaria is a complication of P. falciparum
infection:
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Coma
Repeated seizures
Hypoglicemia
 Other complications:
 splenic ruprure, renal failure
 severe hemolysis (blackwater fever)
 pulmonary edema, hypoglycemia, thrombocytopenia
 algid malaria (sepsis syndrome with vascular collapse
 Death most frequent with complicated P. falciparum
malaria
 Death is increased in children with measles
intestinal parasites, schistosomiasis, anemia, and
malnutrition
Prevention
 There are two components of malaria prevention:
Reduction of exposure to infected mosquitoes
 Chemoprophylaxis

 Chemoprophylaxis:
All visitors to and residents of the tropics
 Children of nonimmune women
 started 1 to 2 weeks before a person enters the endemic area
except for doxycycline which can be started 1 to 2 days before

 continue
for at least 4 weeks after the person leaves
 Areas of the world that are free of chloroquine-
resistant malaria strains, chloroquine is given once
per week
 In areas where chloroquine-resistant P. falciparum
exists, atovaquone-proguanil, mefloquine, or
doxycycline may be given as chemoprophylaxis
 Atovaquone-proguanil is generally recommended for
shorter trips (up to 2 wk), since it must be taken
daily
 Atovaqoune-proguanil is started 1-2 days before
travel, and mefloquine is started 2 wk before travel
Toxoplasmosis
 Infection is acquired by:
 infectious oocysts, such as those excreted by newly infected
cats
 from ingesting cysts in contaminated, undercooked meat
 Less commonly, transmission occurs transplacentally
during acute infection of pregnant women
 Acquired toxoplasmosis:
 usually asymptomatic


Symptomatic infection is typically a heterophile-negarive
mononucleosis syndrome
Disseminated infection is more common in
immunocompromised person
Congenital Toxoplasmosis
 The later in pregnancy that infection occur but the
less severe the illness
 Serologic diagnosis:

fourfold increase in antibody tirer or seroconversion
positive IgM antibody titer

positive polymerase chain reaction (PCR) for T. gondii

 Treatment:
 pyrimethamine and sulfadiazine
 folinic acid
 Spiramycin is used in therapy of pregnant women with
toxoplasmosis

Corticosteroids are reserved for patients with acute CNS or ocular
 Ingesting only well-cooked meat
 avoiding cats or soil in areas where cats defecate are
prudent measures for pregnant or
immunocompromised persons
 Administration of spiramycin to infected pregnant
women→congenital infection↓
Amebiasis
 E. histolytica
 The 2 most common forms of disease:


amebic colitis
amebic liver abscess
 Infection is acquired through the ingestion of parasite
 Cysts can be killed by heating to 55°C
 Food or drink contaminated with Entamoeba cysts and
direct fecal-oralcontact are the most common means of
infection.
 Amebic Colitis:
 occur within 2 wk of infection
 Diarrhea is frequently associated with tenesmus
 most patients do not present with grossly bloody
stools
 fever documented in only one third of patients
 High in children 1-5 yr of age
 Amebic Liver Abscess:
 Serious manifestation of disseminated infection, is
uncommon in children
 Enlargement and tenderness of the liver
 Changes at the base of the right lung, such as
elevation of the diaphragm and atelectasis or
effusion
 examining 3 stools →Sensitivity can be increased to
85-95%
 phagocytosed erythrocytes (specific for E.
histolytica)
 The most sensitive serologic test, indirect
hemagglutination
 Rapid antigen and antibody tests for bedside
diagnosis
 Chronic amebiasis should be excluded before
initiating corticosteroid treatment for IBD
Giardiasis
 The life cycle of Giardia is composed of 2 stages:
trophozoites and cysts
 Giardia trophozoites contain 2 oval nuclei anteriorly
and 4 pairs of flagella
 Outbreaks associated with drinking water
 Asymptomatic carriage may persist for several
months
 Transmission of Giardia is common in child-care
centers, consumers of contaminated water, travelers
to certain areas
 Transmission of Giardia:


water contaminated with Giardia cysts
food-borne
 The incubation period of Giardia infection usually is
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1-2 wk but may be longer
Acute infectious diarrhea, or chronic diarrhea
Failure to thrive and abdominal pain or cramping
Most infections in both children and adults are
asymptomatic
Stools initially may be profuse and watery and later
become greasy
Giardia has been associated with iron deficiency
 Stool enzyme immunoassay (EIA) or direct
fluorescent antibody tests for Giardia antigens
 3 stool specimens
 Aspiration or biopsy of the duodenum
HELMINTHIASE
 Helminths are divided into three groups:
 roundworms, or nematode
 two groups of flatworms, the trematodes (flukes) and the
cestodes (tapeworms)
Hook Worms
 Ankylostoma duodenale ,Necator americanus
 The larvae are found in warm, damp soil and infect

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humans by penetrating the skin
The worms mature and attach to the intestinal wall,
where they suck blood and shed eggs
Albendazole or mebendazole or pyrantel pamoate
Intense pruritus (ground itch)
Examination of fresh stool for hookworm eggs is
diagnostic
Cutaneous Larva Migrans
 Cutaneous larva migrans (creeping eruption) is
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caused by the larvae of several nematodes, primarily
hookworms
A. braziliense is the most common cause
After penetrating the skin, larvae localize at the
epidermal-dermal junction and migrate in this plane,
moving at a rate of 1-2 cm /day
erythematous, serpiginous tracks, which occasionally
form bullae
Intense localized pruritus, without any systemic
symptoms, may be associated with the lesions
 If left untreated, the larvae die, and the syndrome
resolves within a few weeks to several months
 Treatment with ivermectin
Ascariasis
 After humans ingest the eggs, Iarvae are released
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and penetrate the intestine migrate to the lungs,
ascend the trachea, and are swallowed
Manifestations may be the result of migration of the
larvae
Pulmonary ascariasis
Intestinal ascariasis
Examination of fresh stool for characteristic eggs is
diagnostic
 The fertile ova are oval in shape with a thick
mammillated covering measuring
 albendazole (400 mg PO once, for all ages
 mebendazole (1 00 mg bid PO for 3 days or 500 mg
PO once forall ages)
 pyrantel pamoate (11 mg/kg PO once, maximum
1g)
 Piperazine citrate (75 mg/kg/day for 2 days
maximum 3.5 g/day)


neuromuscular paralysis of the parasite and rapid expulsion
of the worms
treatment of choice for intestinal or biliary obstruction
Visceral Larva Migrans
 Toxocara canis, or, Iess commonly, the cat
tapeworm, Toxocara cati
 These organisms also cause ocular larva migrans
 Visceral larva migrans is most common in young
children with pica who have dogs or cars as pets
 Ingesred eggs hatch into larvae that penetrate the
gastrointestinal tract and migrate to the liver,…
 Symptoms of visceral larva migrans:
 result of the number of migrating worms
 Associated immune response
 Eye examination may reveal granulomatous lesions
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near the macula or disc
Eosinophilia and hypergammaglobulinemia
ELISA
This is usually a self limited illness
In severe disease, albendazole or mebendazole is
used
Entrobiasis
 Humans ingest the eggs carried on hands, present in
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house dust or on bedclothes
At night, the females migrate to the perianal area to
lay their eggs
The most common symptoms are nocturnal anal
pruritus (pruritus ani)
Vaginitis and salpingitis may develop secondary to
aberrant worm migration
The eggs are detected by microscopically examining
adhesive cellophane tape pressed against the anus
 Treatment:
 albendazole(400 mg), mebendazole (100 mg),
 pyrantel pamoate(11 mg/kg, maximum 1g) each given as a
single oral dose
 and repeated in 2 weeks
Echinococcosis
 Hydatid or unilocular cyst disease caused by
Echinococcus granulosus
 Alveolar cyst disease caused by Echinococcus m
ultilocularis
 Humans acquire echinococcosis by ingesting eggs
and become an intermediate host
 The eggs hatch in the intestinal tract, and the larva
(oncospheres) penetrare the mucosa and enter the
circulation to pass to the liver
 Pulmonary cysts may cause hemoptysis, cough,
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dyspnea, and respiratory distress
Brain cysts appear as tumors
liver cysts cause problems as they compress and
obstruct blood flow
Ultrasonography identifies cystic lesions, and the
diagnosis is confirmed by serologic testing
Treatment:Surgical resection plus albendazole
Neurocysticercosis
 Taenia. solium, and is the most frequent helminthic infection
of the CNS
 Humans are infected after consuming cysticerci in raw or
undercooked larva-containing pork→adult pork tapeworm
 Infection with the invasive intermediate stage (cysticercus) is
called cysticercosis
 Ingestion of food or water contaminated with the eggs of T.
solium.
 Cysts typically enlarge slowly, causing no or minimal
symptoms
 The cyst then begins to swell, and leakage of antigen incites an
inflammatory response
 The CSF shows lymphocytic or eosinophilic pleocytosis
 The diagnosis is confirmed by serologic testing
 Neurocysticercosis is treated:
 Albendazole or praziquantel
 corticosteroids for concomitant cerebral inflammation from
cyst death
 Anticonvulsant drugs
Life cycle of Taenia saginata and Taenia
solium
Taenia solium - The Pork Tapeworm