Microbiology: Parasites

• Giardia lamblia
• Entamoeba histolytica
• Cryptosporidium

• Disease:
• Giardiasis: bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers and hikers)

Think fat rich Ghirardelli chocolates for fatty stools of Giardia

Transmission: Cysts in water

Dx: Trophozoits or cysts in stool

Tx: Metronidazole

Giardia lamblia

• A. Trophozoite
• B. Cyst

Disease: Amebiasis: bloody diarrhea (dyssentery), liver abscess (reddish brown), RUQ pain (histology shows flask-shaped ulcer if submucosal abscess of colon rputures

Transmission: Cysts in water

Dx: Serology and/or trophozoites with RBCs in the cytoplasm or cysts (with multiple nuclei) in the stool

Tx: Metronidazole and iodoquinol

Entamoeba histolica

• C. trophozoites (with RBCs in the cytoplasm)
• D. cyst (with multiple nuclei)

• Disease: Severe diarrhea in AIDS
• -Mild disease (watery diarrhea) in non-immunocompromised

Transmission: Cysts in water

Dx: Cysts on acid-fast stain

Tx: Prevention (by filtering city water supplies); no treatment

• Toxoplasma gondii
• Naegleria fowleri
• Trypanosoma brucei

• Disease: Brain abscess in HIV (seen as ring-enhancing brain lesions on CT/MRI)
• -congenital toxoplasmosis = "classic triad" of chorioretinitis, hydrocephalus, and intracranial calcifications

Transmission: cysts in meat or cat feces; crosses placenta (pregnant women should avoid cats)

Dx: serology, biopsy

Tx: Sulfadiazine + pyrimethamine

Disease: rapidly fatal meningoencephalitis

Transmission: Swimming in freshwater lakes (Think Nalgene bottle filled with freshwater containing Naelgeria); enter via cribiform plate

Dx: Amoebas in spinal fluid

Tx: Amphotericin has been effective for a few survivors

Naegleria amoeba

• T. gambiense
• T. rhodesiense

Disease: African sleeping sickness: enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma

Transmission: Tsetse fly, a painful bite

Dx: Blood smear

Tx: Suramin for blood-borne disease or melarsoprol for CNS penetration (it SURe is nice to go to sleep; MELAtonin helps with sleep)

Trypanosoma on blood smear

• Plasmodium
• -P. vivax/ovale
• -P. falciparum
• -P. malariae

Babesia

Disease: Malaria: fever, headache, anemia, splenomegaly

• -P. vivax/ovale
• Presentation: 48-hr cycle (tertian; includes fever on first day and third day);
•     - dominant form in liver

• -P. falciparum
• Presentation: severe; irregular fever patterns
•       - parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs

• -P. malariae
• Presentation: 72-hr cycle (quartan)

Transmission: Mosquito (Anopheles)

Dx: blood smear, trophozoite ring form, RBC shizont with merozoites

• Tx: Chloroquine (blocks plasmodium heme polymerase); if resistant, use mefloquine
• -vivax/ovale - add primaquine for dominant form in liver (hypnozoite)

Plasmodium (malaria)

• A. blood smear, trophozoite ring form
• B. RBC schizont with merozoites

Disease: fever and hemolytic anemia; predominantly in northeastern US; asplenia pts have increase risk for severe disease

Transmission: Ixodes tick (same as Borrelia burgdorferi of Lyme disease; may often co-infect humans)

Dx: Blood smear, ring form, "Maltese cross"

Tx: Quinine, clindamyacin

Babesia

• Blood smear
• 1. ring form
• 2. "Maltese cross"

• Trypanosoma cruzi
• Leishmania donovani

Disease: Chagas' disease (dilated cardiomyopathy, megacolon, megaesophagus); predominantly in South America

Transmission: Reduviid bug ("kissing bug"), a painless bite (much like a kiss)

• Dx: Blood smear
• 

Tx: Nifurtimox

Disease: Visceral leishmaniasis (kala-azar): spiking fevers, hepatosplenomegaly, pancytopenia

Transmission: Sandfly

Dx: Macrophages containing "amastigotes"

• 
• Tx: Sodium stibogluconate

Trichomonas vaginalis

Disease: Vaginitis: foul-smelling, greenish discharge; itching and burning; do not confuse with Gardnerella vaginalis, a gram-negative bacterium that causes bacterial vaginosis

Transmission: Sexual (cannot exist outside human - cannot form cysts)

Dx:  Trophozoites (motile) on wet mount

Tx: Metronidazole for pts and partner

• Intestinal
• Tissue

• Ingestion - Enterobius, Ascaris, Trichinella
• Cutaneus - Strongyloides, Ancylostoma, Necator

• You'll get sick if you EAT these!
• These get into your feet from the SANd.

• Enterobius vermicularis (pinworm)
• Ascaris lumhricoides (giant roundworm)
• Trichinella spiralis
• Strongyloides stercoralis
• Ancylostoma duodenale, Necator americanus (hookworms)

Food contaminated with eggs; intestinal infection; causes anal pruritis (the Scotch tape test)

Tx: bendazoles or pyrantel pamoate (worms are BENDy; treat with meBENDazole)

Eggs are visible in feces; intestinal infection

Tx: bendazoles or pyrantel pamoate

Undercooked meat, usually pork; inflammation of muscle (larvae encyst in muscle); periorbital edema

Tx: bendazoles

Larvae in soil penetrate the skin; intestinal infection; causes vomiting, diarrhea, and anemia

Tx: bendazoles or ivermectin

Larvae penetrate skin of feet; intestinal infection causes anemia (sucks blood from intestinal walls)

Tx: bendazoles or pyrantel pamoate

• Dracunculus medinensis
• Onchocerca volvulus
• Loa loa
• Wuchereria hancrofti
• Toxocara canis

In drinking water; skin inflammation and ulceration

Tx: Niridazole, prolonged extraction

Transmitted by female blackflies; causes hyperpigmented skin and river blindness (remember black flies, black skin nodules, "black sight"). Can have allergic reaction to microfilaria

Tx: Ivermectin (IVERmectin for rIVER blindness)

Transmitted by deer fly, horse fly, and mango fly; causes swelling in skin (can see worm crawling in conjunctiva)

Tx: Diethylcarbamazine

Female mosquito; causes blockage of lymphatic vessels (elephantiasis). Takes 9 months - 1 year after bite to get elephantiasis sx.

Tx: Diethylcarbamazine

Food contamination with eggs; causes granulomas (if in retina --> blindness) and visceral larva migrans

Tx: Albendazole or mebendazole

• Taenia solium
• Diphyllobothrium latum
• Echinococcus granulosus

• Treat most with Praziquantel

• Ingestion of larvae encysted in undercooked pork leads to intestinal tapeworm.
• Ingestion of eggs causes cysticercosis and neurocysticercosis, mass lesions in brain ("swiss cheese"" appearance)

Tx: Praziquantel (use -bendazoles for neurocysticercosis)

Ingestion of larvae in raw freshwater fish. Causes vit B12 deficiency, results in anemia

Tx: Praziquantel

Eggs in dog feces when ingested can cause cysts in liver; causes anaphylaxis if echinococcal antigens are released from cyst (surgeons inject ethanol before removal to kill daughter cysts)

Tx: Bendazoles

• Schistosoma
• Clonorchis sinensis
• Paragonimus westermani

• Tx: Praziquantel

Snails are host; cercariae penetrate skin of humans

• Causes granulomas, fibrosis, and inflammation of the spleen and liver. 
• Chronic infection with S. haematobium can lead to squamous cell carcinoma of the bladder

Tx: Praziquantel

• Undercooked fish
• causes inflammation of the biliary tract --> pigmented gallstones
• Also associated with cholangiocarcinomas

Tx: Praziquantel

• Undercooked crab meat
• Causes inflammation and secondary bacterial infections of the lung, causing hemoptysis

Tx: Praziquantel

• Brain cysts, seizures - Taenia solium (cysticercosis)
• Liver cysts - Echinococcus granulosus
• B12 deficiency - Diphyllobothrium latum
• Biliary tract disease, cholangiocarcinoma - Clonorchis sinensis
• Hemoptysis - Paragonimus westermani
• Portal hypertension - Schistosoma mansoni
• Hematuria, bladder cancer - Schistosoma haematobium
• Microcytic anemia - Ancylostoma, Necator
• Perianal pruritis - Enterobius (pinworm)