Parasitic Diseases Flashcards
Protozoan GI infestations
Entamoeba histolytica (amoeba) Giardia lamblia (flagellate) Cryptosporidiosis (sporozoan)
infectious form of Entamoeba histolytica
cysts which have cell wall to resist gastric acid
trophozoites are amebic form
What does Entamoeba histolytica do in the body?
lyse colonic epithelial cells
trophozoites invade crypts of the colonic glands; burrow through tunica propria; halted by muscularis mucosae
Entamoeba histolytica characteristially produce?
flask-shaped ulcers with narrow neck and broad base
What happens in 40% of Entamoeba histolytica cases?
parasites penetrate portal vessels, embolize to liver and form amebic abscesses; usually solitary; pain may be elicited on palpation of liver
Pathology of Entamoeba histolytica
involves cecum and ascending bowel; in severe cases, entire bowel may be involved
parasites resemble macrophages
What happens to the mucosal cells overlying Entamoeba histolytica organisms?
mucosal cells slough due to deprivation of blood supply; neutrophilic infiltrates result in liquefactive necrosis
Chronic damage with Entamoeba histolytica leads to
napkin-like constrictive lesions similar to colonic carcinoma due to extensive fibrosis
Obligate fermenters of glucose to ethanol
Amebae, giardia, trichomonads, and anaerobic bacteria
Metronidazole targets
ferredoxin-dependent pyruvate-oxidoreductase
Giardia lamblia associated with
IgA deficiency and immunosuppression (common intestinal parasite in AIDs patients)
Infectious form of giardia
dormant cyst
What does giardia cause
diarrhea, not dysentery
Where do giardia trophozoites multiply?
in small intestine (duodenum) via concave attachment disc
attach to mucosa but do not invade the intestinal wall
Characteristic morphology of giardia
two nuclei which resemble eyes, pear shape
really cute, looks like an old man
Abnormalities of the mucosa with a giardia infection
clubbing of villi with mixed inflammatory infiltrate of the lamina propria
follicular hypertrophy of mucosal lymphoid tissue in IgA deficient individuals
Cryptosporidium causes
transient, watery diarrhea in children
severe disease in immunosuppressed
far more severe disease in immunosuppressed individuals
Infectious oocytes not killed by
chlorine
What form of cryptosporidium is infectious
environmentally resistant oocytes
crypto is the only GI parasite with
sexual reproduction in host
What do Cryptosporidium do inside the body?
adhere to jejunum/ileum/colonic epithelium (apical brush border)
mixed inflammatory cell infiltrate in lamino propria
infect macrophages and underlyig Peyer’s patches
What occurs with Cryptosporidium disruption of the mucosa
malabsorption and secretory diarrhea
diarrhea and vomiting (3-14 days)
Diagnosis of Entamoeba histolytica
stool of aspirates (abscess)
Trophozoites or cysts
Diagnosis of Giardia lamblia
cysts of trophozoites in stool
Biopsy; “string test’
Diagnosis of Cryptosporidium
biopsy; fecal smears; “string test”
Treatment of Entamoeba histolytica
metranidazole, iodoquinal
Treatment of Giardia
metranidazole, furazolidone
Treatment of Cryptosporidium
rarely effective; spiramycin
Four types of malaria
P. falciparum
P. vivax
P. ovale
P. malariae
Describe pathogenesis of P. vivax and P. ovale
infect RBCs, leads to removal by spleen; mild anemia, rarely splenic rupture and nephrotic syndrome
What do P. falciparum sporozoites in the body?
invade liver cells
rapidly form thousands of merozoites
hepatocytes rupture, release merozoites
What do merozoites bind on RBCs
sialic residues
What do merozoites do within RBCs
mature into ringed trophozoite forms
Immature ring forms (RBCs/malaria) do what
get trapped in spleen because they’re flexible
P. falciparum results in
severe anemia, renal failure, pulmonary edema, cerebral symptoms and death
What causes 80% of deaths in children with P. falciparum?
cerebral involvement
What leads to black water fever (hemoglobinuria) and kidney damage with P. falciparum?
hemolysis of infected erythrocytes
pathology of p falciparum
large spleen, liver, and kidneys
pigmented liver and kidneys
CNS vessels plugged with parasitizied cells
focal hypoxic lesions in heart
What is Babesiosis
malaria-like protozoans transmitted by same deer ticks which carry Lyme disease
fever and hemolytic anemia
Trypanosomiasis causes
African sleeping sickness
intermittent fevers, lymphadenopathy, splenomegaly, progressive brain dysfunction, cachexia and death
Typanosomiasis transmistted by
tsetse fly
What stimulates typanosome parasite growth
interferon-gamma production by CD8 cells
What appears at the site of a tsetse fly bite that is transmitting typanosomiasis?
large, red rubbery chancre (ulcer plus large mononuclear inflammatory infiltrate)
Most frequent cause of heart failure in Brazil and neighboring Latin American countries
Chaga’s disease (Trypanosma cruzi)
How is Chaga’s transmitted
person to person via “kissing bugs” which feed on sleeping inhabitants and pass infection via feces
chagoma
erythematous nodule at site of trypanosoma cruzi entry
Acute Chaga’s disease involves
cardiac damage resulting from direct invasion of cardic cells;
may present with fever, cardiac dilation and failure and generalized lymphadenopathy or splenomegaly
Pathology of chronic myocarditis
dilated heart with mural thrombi; interstitial and perivascular infiltrates are composed of lymphocytes, plasma cells and monocytes; cardiac cell necrosis and interstitial fibrosis
Describe the toxoplasma gondii organism
obligate intracellular protozoan
Toxo causes
subclinical infections but severe opportunistic disease in AIDS patients
Toxo oocytes are shed in?
cat feces; however, the oocytes are not infectious for 24-48 hours
undercooked lamb or pork contains intracystic organisms
toxo enters through
gut
many toxo infections in AIDS patients appear to be
reactivation of dormant organisms from cysts
toxo is particularly damaging to fetuses when?
during the first trimester of pregnancy
disseminated and often fatal parasitemias occur in 25%
neonatal toxoplasmosis
destructive lesions in CNS are composed of microglial nodules
extensive CNS necrosis, vascular thrombosis, and intense inflammation
Leishmaniasis vector
sandfly
Visceral forms of leishmaniasis
spread thru RES system result sin severe systemic disease
hepatosplenomegaly, lymphadenopathy, pancytopenia, fever weight loss
fibrotic liver, late lesions
black fever
hyperpigmentation of skin with leishmaniasis
Cutaneous forms of leishmaniasis
relatively mild with localized disease consisting of sing ulcer with surrounding granulomatous inflammation
mucocutaneous forms of leishmaniasis
moist, ulcerating or nonulcerating lesions which may be disfiguring
Naegleria
parasitic meningitis
infection from water source through cribiform plate in nose; mimics meningococcal meningitis
Acanthamoeba
parasitic meningitis in immunosuppressed individuals
entry through nasal mucosa, lung or skin with hematogenous dissemination
AIDS associated, but not disseminated parasitic infections
Amebae, giardia
Disseminated disease in immunosuppressed individuals
cryptosporidiosis, toxo
Schistosomiasis causes death usually from
hepatic granulomas and fibrosis
How does schistosomiasis infect hu8mans
sporocysts in fresh water snails give rise to cercaria which infect humans by penetrating through the skin
IL-3, IL-4, IL-5 results in induction of
IgE synthesis, mastocytosis and eosinophilia
what forms around schistosome egg?
calcified, pinhead granulomas
granulomas include macrophages, lymphocytes, neutrophils and eosinophils
Describe liver flukes (clonorchiasis)
adult flukes live in biliary ducts
humans become infected by eating improperly cooked
usually asymptomatic
Taenia saginata
beef tapeworm; ingestion of undercooked beef
no cysticercosus
Taenia solium
pork tapeworm
ingestion of undercooked pork with encysted cysticerci
attach to intestinal wall with scolices
proglottids with eggs shed in feces
Cysticercosus
T. solium eggs ar eingested, larbae hatch and penetrate gut wall
hematogenous dissemination results in cysts in CNS
Echinococcus
canine tapeworm
hydatid cysts form in liver and lungs
usually asymptomatic and chronic unless cysts rupture
Pinworms (Enterobius vermicularis)
small worms of intestine
anal pruritis
human is the only reservoir, pinworms cannot be gotten from anmals
Whipworms (Trichuris trichiura)
tropics
local hyperemia and lesions of colonic mucosa
not invasive
Hookworms (Necator americanus/Ancylostoma duodenale)
hookworms attach to upper levels of small intestine
larvae penetrate between toes
Hookworm symptomology
small itchy papule where they penetrate skin
mild pneumonitis from traveling thru lungs
blood loss and anemia
Strongyloides (Strongyloides stercoralis)
fatal disseminated disease in immunocompromsied host
severe pneumonitis and duodenitis
manifestations usually mild otherwise
Ascaris lumbricoides
extremely large worms that live unattached in lumen of small intestine
Symptoms and signs of ascaris
eosinophilic pneumonitis of the lung including dyspnea, dry cough, fever and eosinophilia
epigastric pain, malnutrition
eggs in feces
Small intestine parasites
hookworms, ascaris, strongyloides, giardia
Trinchinosis (Trichinella spiralis)
improperly cooked pork
larvae penetrate tissues, disseminate hematogenously, and encyst in muscle cells
signs of trinchinosis
marked eosinophilia, fever, myalgias, periorbital edema
patchy interstitial myocarditis with eosinophilia and giant cells resulting in scarring
Trapped trinchinella larvae in the lungs cause
allergic eosinophilic infiltrate
filariasis (Wuchereria bancrofti)
transmitted by mosquito
elephantiasis
onchocercias
filarial nematode transmitted by blackflies
major cuase of blindnes in equatorial africa
