Trichinosis

Introduction

-Trichinosis is a parasitic disease caused by Trichinella spiralis and related species 

-it is the most common parasite of skeletal muscle

-it is spread by ingestion of undercooked meat, most commonly pork 

-Life cycle: Humans ingest undercooked meat containing encysted larvae, which mature into adults in the intestine. Female worms release larvae which enter blood and migrate to skeletal muscle or other organs, where they encyst

Symptoms & Signs 

-Most infections are asymptomatic

-Infection can be divided into two phases: 

Intestinal phase: fever, headache, chills, abdominal pain, nausea, vomiting, and diarrhea 

Muscular phase: Fever, facial edema, eyelid or periorbital edema, myalgia, weakness, maculopapular exanthem, subungual bleeding, conjunctivitis and subconjunctival hemorrhages, retinal hemorrhages, dry cough, dyspnea, dysphagia, painful movement of the eye muscles, involuntary movements, myocarditis, thromboembolic disease, and encephalitis

Diagnosis 

Labs: Eosinophilic leukocytosis, elevated serum muscle enzymes (creatine kinase, lactate dehydrogenase, aspartate aminotransferase), normal ESR 

-ELISA, serologic tests, muscle biopsy showing encysted larvae 

Treatment 

Albendazole is the drug of choice for trichinosis; Mebendazole 


Dracunculiasis

Introduction

-Dracunculiasis is caused by the nematode roundworm called Dracunculus medinensis, or Guinea worm.

-The Guinea worm is the largest tissue parasite of humans

-the disease is on the verge of being eradicated

-Humans are infected when they ingest water containing infective larvae from crustaceans like Cyclops 

Symptoms & Signs 

-Fever, periorbital edema, wheezing, urticaria, nausea, vomiting, diarrhea, dyspnea, blister formation, rupture of the blister with the worm emerging as a whitish filament in the center of a painful ulcer 

-Immersion in water relieves the pain

Diagnosis 

-identification of a typical skin ulcer with a protruding worm

Treatment 

-No drug is effective in treating dracunculiasis 

-Wet compresses, occlusive dressings

-Definitive treatment: Gradual extraction of the worm by sequentially rolling it over a small stick


Enterobiasis

Introduction

Enterobiasis is caused by a small intestinal parasite called Enterobius vermicularis 

-it is the most common intestinal nematode in the United States with highest prevalence in school-aged children 

-Transmission is by the fecal-oral route 

-Gravid female worms migrate nocturnally from the cecum to the perianal region to deposit large numbers of eggs 

Symptoms & Signs 

-Most individuals with pinworm infection are asymptomatic

-The most common symptom is perianal pruritis, which is most severe at night 

-Enuresis, restlessness, insomnia, perianal scratching, cellulitis, impetigo 

Diagnosis 

-Diagnosis can be made by “Scotch Tape” technique: Apply adhesive cellulose tape to the anal region and examine under thee microscope for ova 

-Eggs are football shaped with a thin outer shell

Treatment 

-The treatment of choice is albendazole

-Other effective agents: Mebendazole, Pyrantel pamoate 

-All family members may need treatment


Strongyloidiasis

Introduction

Strongyloidiasis is caused by S. stercoralis, a Nematode parasite

-Humans are the only hosts: It’s life cycle differs from that of most other helminths in that its entire life cycle may be completed within the human host 

-it is acquired by direct contact of skin with larvae or by ingestion of food contaminated with larvae 

-Life cycle: Filariform larvae (infectious) penetrate the skin, enter the blood, migrate to the lungs, move into alveoli, ascend up the trachea, swallowed, enter the colon, produce eggs which form rhabditiform larvae(non-infectious), which are passed in the feces

Autoinfection: Rhabditiform larvae can transform into filariform larvae in human host resulting in seeding of the perianal area with parasites; immunosuppression enhances risk of autoinfection  

-Of the common helminths, only  strongyloides may persist in the human host indefinitely

Symptoms & Signs 

Skin: A serpiginous urticarial rash in response to the migrating larvae; Generalized petechiae and reticular purpura of thee arms, legs, and abdomen with a characteristic thumbprint periumbilical distribution

Thumbprint sign: A unique pattern of periumbilical purpura resembling multiple thumbprints 

Larval currens: External autoinfection producing raised, red, serpiginous lesions over the buttocks, abdomen and back 

Pulmonary and intestinal manifestations can be like hookworm and Ascaris infections

Lungs: Cough, fever, eosinophilia

GI: Peptic-ulcer like pain, nausea, vomiting, diarrhea, constipation, malabsorption, weight loss

Hyperinfection: The most severe complication of Strongyloidiasis is hyperinfection

Immunodeficiency due to HIV,  human T-lymphotropic virus-1 (HTLV-1), has a stronger association with Strongyloides hyperinfection

Lung:  the most common extraintestinal manifestation of hyperinfection syndrome is pulmonary disease; Cough, wheezing, dyspnea, hemoptysis 

GI: Abdominal pain, diarrhea, ileus 

Other organs: liver, urinary tract, brain 

Diagnosis 

Larvae: Diagnosis depends on finding larvae, rather than eggs, in the stool

Serology: Serology via ELISA 

Labs: Eosinophilia 

Treatment 

Effective agents: Ivermectin (Drug of choice), Albendazole 


Hookworm disease

Introduction 

-Hookworm disease is caused by the Infection with the hookworms Ancylostoma duodenale and Necator americanus

-Adult hookworm possess two pairs of teeth in the buccal capsule 

-Male hookworm has a characteristic copulatory bursa 

-Infectious larvae present in soil penetrate the skin, enter bloodstream, reach the lungs, invade the alveoli, ascend the airways, are swallowed, reach the intestines, mature into adult worms, attach to the mucosa, and suck blood

Symptoms & Signs 

Most infected persons are asymptomatic

Skin: Initial skin infection by the larval penetration may cause a pruritic maculopapular rash (ground itch) and serpiginous tracks of subcutaneous migration (cutaneous larva migrans) 

Lungs: Pulmonary symptoms during larval migration through the lungs include fever, cough and wheezing 

Gastrointestinal: Abdominal pain, anorexia, nausea, vomiting, diarrhea, ascites 

Hematological: Hypochromic microcytic anemia, eosinophilia, hypoalbuminemia

Diagnosis 

Diagnosis is based on the identification of characteristic eggs in feces

Adult worms: Ancylostoma duodenale possesses four sharp tooth-like structures, whereas N americanus has dorsal and ventral cutting plates;  the males have a unique fan-shaped copulatory bursa

Labs: Microcytic anemia, occult blood in the stool, hypoalbuminemia, eosinophilia 

Treatment 

Effective agents: Albendazole, Mebendazole, Pyrantel pamoate 


Trichuriasis

Introduction

Trichuriasis is caused by whipworm Trichuris trichiura, a nematode parasite of the large intestine 

-Humans acquire the infection by eating foods contaminated with eggs. In the small intestine, the larvae hatch, mature and migrate to the colon 

– Unlike Ascaris, Trichuris does not have a migratory lung phase

-The adult worm has a ‘buggy whip’ appearance, hence the name whipworm 

Symptoms & Signs 

-Most infected persons are asymptomatic

-Abdominal pain, distention, cramps, nausea, vomiting, diarrhea, rectal prolapse, iron-deficiency anemia

Diagnosis 

-Diagnosis is based on finding the barrel-shaped or lemon-shaped eggs with a plug at each end 

-Adult worms may be seen in the prolapsed rectum

Treatment 

Effective agents: Albendazole, mebendazole, ivermectin, and oxantel pamoate


AscariASIS

Introduction 

Ascariasis is caused by Ascaris lumbricoides, the most common intestinal helminth and the largest intestinal nematode 

-it can reach up to 40 cm in length 

-it is particularly common in the Far East, India, and South Africa

-it is seen following ingestion of foods or vegetables fertilized by ‘night soil’ (human feces) or playing in the infected soil 

Life cycle: Humans ingest eggs, which form larvae in the gut, where after hatching, they migrate through the blood to the lungs, where they enter the alveoli,ascend the bronchial tree, and are swallowed. In the gut, they become adults and lay eggs that are passed in the feces. Adult worms can migrate to the appendix, bile duct or pancreatic duct, causing obstruction and inflammation 

Symptoms & Signs 

Most persons with Ascaris infection are asymptomatic

Lungs: migrating worms can cause fever, cough, chest pain, dyspnea, eosinophilia, or  “Löffler syndrome”

Gastrointestinal: Abdominal pain, obstruction, volvulus, perforation, appendicitis 

Biliary: Cholangitis, cholecystitis, obstructive jaundice, pancreatitis 

Diagnosis 

Adult worms: can be seen emerging from the mouth, nose, or anus or in stools 

Chest X ray: migratory pulmonary infiltrates 

ERCP: linear filling defects within the bile ducts 

Eggs in stool: egg is oval with an irregular surface with a typical “scalloped” edge 

Treatment 

Effective agents: Albendazole, mebendazole, ivermectin, or pyrantel pamoate 


Taenia solium infection

Introduction

Pork taeniasis is a disease caused by the tapeworm Taenia solium 

– it is particularly common in South and Southeast Asia, Africa, Latin America, and Eastern Europe

T solium inhabits the human jejunum 

-it possesses a rostellum armed with sucking disks and two rows of hooklets

-It can cause two distinct forms of infection in humans: adult tapeworms in the intestine (Taeniasis) or larval forms in the tissues (cysticercosis). 

-Taeniasis is acquired by eating raw or undercooked pork. Cysticercosis is acquired only by ingesting eggs in fecally contaminated food or water.

-Significant difference from beef tapeworm: Tissue cysticerci develop in swine and humans

Symptoms & Signs 

Taeniasis: Tapeworm in gut causes little damage. 

Cysticercosis: Cysticerci encyst in various human tissues, including skin, liver, muscle, heart, kidney,eye and brain 

Neurocysticercosis: fever, nausea, vomiting,headache, mental disturbances,  focal neurologic abnormalities, personality changes, visual disturbances, seizures, increased intracranial pressure, and hydrocephalus  

Diagnosis 

Adult worm is diagnosed from proglottids or eggs in stool 

Cysticercosis is diagnosed by imaging, biopsy, or serology 

Neuroimaging: Mass lesions; a scolex within a cystic lesion 

Treatment 

Intestinal worms: Praziquantel 

Cerebral cysticercosis: Praziquantel, albendazole,antiseizure medications 

Obstructive hydrocephalus: removal of the cysticercus via endoscopic surgery 


Taenia saginata

Introduction 

Beef Taeniasis is a parasitic infection by beef tapeworm called Taenia Saginata 

-it is prevalent in Latin America, Eastern Europe, Africa and Russia 

-Humans become infected when they eat raw or undercooked beef (“measly beef”) 

-Taenia saginata inhabits the human jejunum, grow to a maximum length of 10 m

-After ingestion, larvae attach to the gut wall and become adult worms with gravid proglottids. 

-Terminal proglottids pass in the feces and are eaten by cattle

Symptoms & Signs 

-Most persons infected with beef tapeworm are asymptomatic 

-Nausea, vomiting, headache, pruritus, abdominal pain, diarrhea, constipation and intestinal obstruction 

– In contrast to Taenia solium, cysticercosis does not occur

Diagnosis 

-Adhesive cellophane tape technique can detect eggs

-Gravid proglottids visible in stool or appear in the underclothing or bedsheets of infected patients

-Adult worm examination: Scolex has four suckers but no hooks

Treatment 

The drug of choice is praziquantel


Paragonimiasis

Introduction

Paragonimiasis is primarily a lung disease caused by the fluke paragonimus 

-it is prevalent in Southeast Asia, Africa, and South and Central America. 

-Human infection follows consumption of undercooked or raw crustaceans such as shellfish, crayfish and crabs 

-After consumption, larvae enter the gut and later burrow through diaphragm into lung parenchyma 

Symptoms & Signs 

Lung disease: Fever, cough, chest pain, hemoptysis with rusty, blood-tinged sputum containing Charcot-Leyden crystals, dyspnea, bronchitis, bronchiectasis, lung abscess,  urticaria, and eosinophilia

-Individuals may be mistaken for having tuberculosis 

Extrapulmonary involvement: Blindness, epididymitis, testicular inflammation, and seizures 

Diagnosis 

Diagnosis is made by finding the characteristic eggs in sputum, urine, or stool, or by identifying worms in biopsied tissues 

-Serologic tests help in making diagnosis and monitoring treatment response

Chest X-ray: small segmental infiltrates, round nodules, cystic rings with a crescent corona, fibrosis, abscesses and calcifications

Skull imaging in CNS disease: clusters of calcified cysts, ring-enhancing lesions

Treatment

The treatment of choice is praziquantel or triclabendazole.


clonorchiasis

Introduction

Clonorchiasis, due to Clonorchis sinensis and opisthorchiasis, due to Opisthorchis, occur in Southeast Asia and Eastern Europe

-Clonorchiasis and opisthorchiasis are clinically indistinguishable. 

-Humans are infected by eating raw, pickled, frozen, dried, salted, and smoked fish containing the encysted larvae (metacercariae)

-After excystation in the duodenum, immature flukes invade the biliary ducts and differentiate into adults 

Symptoms & Signs 

Most infections are asymptomatic

Fever, chills, abdominal pain, urticaria, eosinophilia, hepatomegaly, cholecystitis, cholangitis, pancreatitis, liver abscess, jaundice 

-Chronic infection is associated with increased risk of cholangiocarcinoma 

Diagnosis 

Definitive diagnosis is made by finding the typical brownish, small, operculated eggs in the stool 

-The eggs of Opisthorchis are indistinguishable from those of Clonorchis

– Imaging studies: Biliary tract dilatations with filling defects due to flukes 

Treatment 

The drug of choice is praziquantel

Other effective agent: Albendazole 


Fascioliasis

Fascioliasis is an infectious disease caused by Fasciola hepatica, the sheep liver fluke

-it is prevalent in sheep-raising areas 

-it results from ingestion of encysted metacercariae on aquatic vegetables or water plants such as watercress 

Symptoms & Signs 

Fever, malaise, abdominal pain, weight loss, urticaria, marked eosinophilia, leukocytosis, tender hepatomegaly, cholangitis 

CT and other imaging studies show hypodense migratory lesions of the liver. 

Diagnosis 

Definitive diagnosis: Identification of characteristic eggs in stool, duodenal or biliary aspirates 

CT/imaging studies: hypodense nodules in the liver; tracts or tunnels (representing the migration of larvae)  

Treatment 

The treatment of choice is triclabendazole

Other effective agents: Bithionol, emetine, dehydroemetine, nitazoxanide 

-it does not respond well to praziquantel


schistosomiasis

Introduction

Schistosomiasis is a disease caused by five species of the parasitic genus Schistosoma

Humans are infected with schistosomes after contact with freshwater containing cercariae released by infected snails

Symptoms & Signs 

Schistosomiasis has three stages of clinical symptomatology corresponding to the life cycle of the parasite in the human host 

Stage 1: Cercarial Dermatitis (“Swimmer’s Itch”)

The first stage is characterized by a very itchy maculopapular rash which occurs at the time of penetration 

Stage 2: Acute schistosomiasis (Katayama syndrome)

The second stage is characterized by a serum sickness like syndrome with elevated levels of immunoglobulin E and eosinophilia. 

-Fever,chills, myalgias, headache, cough, sweating, lymphadenopathy, hepatosplenomegaly, diarrhea, abdominal pain, and pulmonary infiltrates 

Stage 3: Chronic schistosomiasis

The third, chronic stage is characterized by granulomatous reactions to egg deposition in the intestine, liver, bladder, lung and CNS 

-Chronic diarrhea, abdominal pain, blood loss, portal hypertension, splenomegaly, bleeding esophageal varices, pulmonary hypertension, right-sided congestive heart failure, transverse myelitis, hematuria, bladder obstruction, hydroureter, and hydronephrosis

Diagnosis 

Diagnostic methods: Detection of schistosome eggs in stool or urine, ELISA, biopsy of the rectum, colon, liver or bladder 

-Eggs of Schistosoma haematobium possess a characteristic terminal spine

Treatment 

The drug of choice for treatment of schistosomiasis is praziquantel

Chemoprophylaxis with artemether has shown efficacy 


Trichomoniasis

Introduction 

Trichomoniasis is a disease caused by the flagellated protozoan parasite Trichomonas vaginalis which manifests as vaginitis in women and nongonococcal urethritis in men 

-It is the most prevalent nonviral sexually transmitted disease worldwide

-it is most often transmitted during sexual contact 

-risk factors include prostitution, multiple sexual partners 

-Females are more often affected and symptomatic than males

Symptoms & Signs 

Women: Vulvovaginal discomfort, pruritis, dysuria, dyspareunia, copious vaginal discharge, no foul smelling, frothy, yellow or green colored discharge pooled in the posterior vaginal fornix, punctuate hemorrhages over vaginal walls, A red, granular, friable endocervix (Strawberry cervix); symptoms worsen during menses and pregnancy; increased risk of preterm birth 

Men: Most infected men are asymptomatic; dysuria, dyspareunia, and scant urethral discharge 

Diagnosis 

T. vaginalis can be recovered from the urethra of both males and females 

-it is detectable in males after prostatic massage

-Diagnostic methods: Wet-mount microscopy, culture, molecular tests (Nucleic acid amplification tests) 

-Trichomonas vaginalsis has characteristic twitching movements, it contains 4 frontal and 1 larger back flagella, which is embedded into an undulating membrane

Treatment

All infected persons should be treated, even if asymptomatic to prevent reinfection and to limit the spread 

Effective agents: Metronidazole, tinidazole 


giardiasis

Introduction

Giardia lamblia is a flagellated protozoan parasite infecting the small intestine and biliary tree

-it is endemic around the world 

-risk factors: drinking contaminated water, hypochlorhydria, immunocompromise, unprotected sex, exposure to infected day care centers, camping sites, swimming areas

-After ingestion, cysts excyst in the small intestine and release flagellated trophozoites in the proximal small intestine. Both cysts and trophozoites are excreted in feces.  

-Chlorination does not destroy cysts; they can be eradicated from water by either boiling or filtration 

-In the United States and Europe, Giardiasis is the most common intestinal protozoan pathogen

Symptoms & Signs 

-the manifestations of infection range from asymptomatic carriage (most common) to chronic diarrhea and malabsorption 

Acute giardiasis: nausea, vomiting, abdominal pain, bloating, belching, flatus, diarrhea; The stool is greasy in appearance, foul-smelling, and floats. It is usually devoid of blood or mucus. 

Chronic giardiasis: can be episodic or continual; diarrhea, increased flatulence, sulfurous belching, weight loss, malabsorption,vitamin deficiencies,  growth retardation, dehydration; stools are foul smelling, greasy or frothy, without blood, pus or mucus. 

Diagnosis

-It can be diagnosed by detection of parasite antigens in the feces, by identification of cysts or trophozoites in the feces or by nucleic acid amplification tests 

-Cysts are oval and contain four nuclei; Trophozoites are pear-shaped and contain 

two nuclei and four pairs (8) of flagella; they have ventral sucking disks 

Treatment 

Effective agents: Metronidazole, tinidazole, quinacrine, furazolidone, nitazoxanide and paromomycin 

-Unlike metronidazole, tinidazole, furazolidone is safe in pregnancy 


Cyclosporiasis

Introduction

Cyclosporiasis is a disease caused by protozoan Cyclospora cayetanensis 

-Cyclospora can be transmitted through water or foods like raspberries, basil, and mesclun 

Symptoms & Signs 

-It can be self-limited or can persist for more than a month

-abdominal cramps, bloating,burping, flatulence, nausea, vomiting, watery, explosive diarrhea, fatigue, anorexia, and myalgia 

Diagnosis 

Diagnosis is made by detection of spherical oocysts in stool stained with acid-fast stains 

-The oocyst formula is  O.2.2 because one oocyst contains two sporocysts and each sporocyst contains two sporozoites 

Treatment 

Treatment is trimethoprim-sulfamethoxazole for 7 days


CRYPTOSPORIDIOSIS

Introduction 

Cryptosporidiosis is a disease caused by intracellular protozoan parasite Cryptosporidium 

At risk populations: day-care settings, travelers, backpackers, campers, swimmers

-After ingestion, oocysts excyst within the intestine and form trophozoites which cause diarrhea

-Trophozoites do not invade the intestine; the site most heavily infested is jejunum 

-Purification of water supply: Cysts are highly resistant to chlorination; they are killed by pasteurization; can be removed by filtration 

Symptoms & Signs 

Immunocompetent patients: self-limited watery diarrhea, dehydration, nausea, and vomiting 

Immunocompromised patients: Chronic watery, nonbloody diarrhea, fever, dehydration and weight loss 

Biliary tree involvement: cholangitis, hepatitis, and pancreatitis 

Diagnosis 

-At least 3 different stool samples should be inspected for oocysts 

-Acid-fast stains reveal red cysts on a blue background 

Treatment 

-Nitazoxanide: effective for immunocompetent patients but not for HIV-infected patients 

-Antiretroviral therapy can alleviate symptoms in the latter 


Amebiasis

Introduction

Amebiasis is an infection caused by Entamoeba histolytica, an intestinal protozoan

-Entamoeba histolytica  is acquired by ingestion of viable cysts from fecally contaminated water, food, or hands 

-E. histolytica is infectious in the cyst form

Symptoms & Signs

Intestinal amebiasis: 

-The most common type of amebic infection is asymptomatic cyst passage

-After ingestion by humans, cysts enter the small intestine and form trophozoites, which adhere and invade the intestinal epithelium and form “flask-shaped” ulcers with a pinhead-sized center and raised edges 

-Fever, vomiting, abdominal distention, abdominal pain, tenderness, hepatomegaly, hypotension, diarrhea,dysentery, weight loss, and heme-positive stools 

Amebic liver abscess:

-The most common extraintestinal manifestation is amebic liver abscess

– Fever, right-upper-quadrant pain, intercostal tenderness, right-sided pleural effusion 

Diagnosis 

Diagnosis is by stool examinations for Entamoeba or its antigen or by serologic tests 

Fecal findings: a positive test for heme, a paucity of neutrophils, amebic cysts or trophozoites 

Liver abscesses: 

Needle aspiration: reddish “anchovy paste” purulent material 

Imaging: Ultrasonography, CT or MRI 

Treatment 

Intestinal amebiasis: 

-Treatment of amebiasis involves the use of tissue amebicides and luminal amebicides 

Tissue amebicides: they act on organisms in the bowel wall and the liver 

Metronidazole, tinidazole, chloroquine, emetines 

Luminal amebicides: they act on organisms only in the lumen of the bowel

Diloxanide, iodoquinol, paromomycin 

Diloxanide is commonly used as the sole agent for the treatment of asymptomatic amebiasis 

Liver abscess: 

Metronidazole is the drug of choice for amebic liver abscess; aspiration, percutaneous drainage, and surgery 


Toxoplasmosis

Introduction

Toxoplasmosis is caused by the obligate, intracellular protozoan parasite Toxoplasma gondii

-the only Definitive hosts are cats 

-In the majority of infected persons, toxoplasmosis is chronic, asymptomatic, and self-limiting

-it is contracted through the consumption of poorly cooked meat or the ingestion of oocytes in food or water contaminated with cat feces; rarely via blood transfusion or organ transplantation 

-Toxoplasma form oocysts in cats. After ingestion, oocysts become tachyzoites in humans and form tissue cysts mostly in skeletal muscle, eye, brain, placenta,and myocardium 

Symptoms & Signs 

Most individuals are asymptomatic, but severe disease is often seen in the immunocompromised individuals 

-Toxoplasmosis occurs in four major clinical forms: 

Infection in Immunocompetent persons 

-infectious mononucleosis like clinical syndrome 

-self-limiting febrile lymphadenopathy which can be non-tender cervical lymphadenopathy or generalized lymphadenopathy; fever, headache, malaise, fatigue, sore throat and myalgias 

Infection in Immunocompromised persons 

-often secondary to reactivation of latent infection 

-fever, headaches, seizures, mental status changes, encephalopathy, meningoencephalitis, mass lesions, multiple necrotizing brain lesions

-The most common clinical manifestation of toxoplasmosis acquired after birth is asymptomatic localized lymphadenopathy

Congenital infection

-Transplacental transmission highest in third trimester

-Newborns may show low birthweight, hepatosplenomegaly, jaundice, anemia, chorioretinitis, blindness, microcephaly, hydrocephalus, abortion, stillbirth,  tram-track intracerebral calcifications, deafness, mental retardation, blueberry muffin lesions (dermal erythropoiesis), purpura 

Ocular toxoplasmosis

Pain, photophobia, visual changes, uveitis, focal necrotizing retinochoroiditis, chorioretinal scar, glaucoma, blindness  

Diagnosis 

-The primary method of diagnosis is serology 

-Identification of tachyzoites in tissue or body fluids: With Wright or Giemsa stains, tachyzoites are crescent-shaped and have a prominent, centrally placed nucleus. 

-Pregnancy: PCR of amniotic fluid

-Newborns: IgM or IgA antibody tests 

-CT and MRI scans: show multiple ring-enhancing cerebral lesions

Treatment

Immunocompetent patients with only lymphadenopathy: do not require treatment 

Immunocompromised patients: Pyrimethamine plus sulfadiazine; given with leucovorin/folinic acid to limit bone marrow toxicity; Pyrimethamine is not used during the first trimester of pregnancy due to its teratogenicity; trimethoprim-sulfamethoxazole is an effective alternative; Clindamycin can be used in sulfonamide-allergic patients 

Congenital infection: Oral pyrimethamine, sulfadiazine, and folinic acid for 1 year; Spiramycin is used to prevent congenital infection  

Ocular toxoplasmosis: Pyrimethamine and either sulfadiazine or clindamycin for 1 month 

Q. What is the most common clinical manifestation of toxoplasmosis acquired after birth? Asymptomatic localized lymphadenopathy 

Q. What are the most frequently involved lymph nodes in toxoplasmosis? cervical nodes 

Q. What is the most common cause of intracerebral lesions in AIDS patients? Toxoplasmic encephalitis 

Q. What is the most common late presentation of congenital toxoplasmosis? Retinochoroiditis 



Babesiosis

Introduction

Babesiosis is a malaria-like disease caused by intraerythrocytic protozoa of the genus Babesia

-similar to malaria, the protozoans invade and lyse the red blood cells 

-it is transmitted by ticks, and occasionally through transfusion of blood products 

 -In the United States, infections occur most frequently in the Northeast and upper Midwest

-Babesia trophozoites appear round or ameboid

-The ring form is most common and lacks the central brownish deposit (hemozoin) typical of Plasmodium falciparum trophozoites

Symptoms & Signs 

Babesiosis can be asymptomatic 

-Symptomatic babesiosis may show fatigue, fever, headache, arthralgia, myalgia, nausea, vomiting, abdominal pain, anemia, thrombocytopenia, hepatomegaly, splenomegaly, splenic rupture, hemolysis, jaundice, dark urine 

Diagnosis 

Blood smear: identification of intraerythrocytic ring forms resembling malaria on a Giemsa- or Wright-stained peripheral blood smear; merozoites often in tetrads (“Maltese cross”) 

Other methods: PCR, indirect immunofluorescent antibody test

Treatment 

-Most patients have a mild illness and recover without therapy

-Similar to malaria, babesiosis requires the use of antiprotozoals

– Two combination therapies are recommended: atovaquone plus azithromycin or quinine plus clindamycin

-in severe disease: exchange transfusion 

Memory Aid: Babesiosis is a malaria like disease caused by a malaria-like organism and treated with malaria-like drugs 


Understanding Malaria

Introduction

Malaria is a disease caused by Plasmodium parasites 

-it is transmitted by the bite of infected female anopheline mosquitoes

-it is uncommon in temperate climates, but still common in tropical and subtropical countries 

-it is the most significant disease acquired through international travel to the tropics

–approximately half of the world’s population are at risk for malarial infection each year

-Five species of the genus Plasmodium infect humans: Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, Plasmodium falciparum, and Plasmodium knowlesi

-While Plasmodium falciparum is the most common cause of serious malaria, P vivax and P knowlesi can also cause severe and fatal infections

-Plasmodium falciparum is also responsible for cerebral malaria 

-Severe malaria is a medical emergency and requires hospitalization 

Pathophysiology 

Step 1: Infected female Anopheles mosquito bites, infects humans: Sporozoites are released from the mosquito into the human bloodstream 

Step 2: Liver stages: Sporozoites migrate to the liver and start multiplication through asexual reproduction within hepatocytes. The daughter cells are called merozoites. Hepatocytes rupture and release merozoites into the circulation.  

Step 3: Red blood cell stages: Merozoites enter the bloodstream and invade red blood cells. A merozoite enters an erythrocyte, multiples within and forms a schizont. 

Step 4: Invasion of the body: A schizont ruptures to release merozoites which releases pyrogens into the bloodstream causing malaria. Thus, symptomatic malaria is caused only by the erythrocytic stage of infection. 

Step 5: Infection of the mosquito: A portion of the merozoites develop into sexual forms (gametocytes). Feeding on its human host, Anopheles mosquito swallows male and female gametocytes, which undergo sexual reproduction in its gut. They produce sporozoites which travel to the salivary glands waiting to be injected into the next innocent human victim. 

Symptoms & Signs: Fever,chills, myalgia, malaise, headache, cough, chest pain, abdominal pain, nausea, vomiting, diarrhea, arthralgia, tachycardia, tachypnea, and splenomegaly

Fever may follow regular cycles 48-hour (P vivax and P ovale) or 72-hour (P malariae) cycles

Severe complications: Anemia, jaundice, renal failure, metabolic acidosis (pH <7.35), hypoglycemia, shock, disseminated intravascular coagulopathy, pulmonary edema, acute respiratory distress syndrome, impaired consciousness, seizures

Diagnosis 

Thick and thin blood films, Rapid diagnostic tests, PCR based tests 

Treatment 

-no antimalarial drug kills sporozoites, so it is not truly possible to prevent infection using drugs 

-Drugs can prevent symptomatic malaria by inhibiting asexual merozoite production in the hepatocytes 

Artemisinin and derivatives: Artemisinin-based combination therapies (ACTs) achieve the fastest clearance of parasites from the blood; According to the WHO, IV artesunate is the drug of choice for severe malaria, effective against  drug-resistant P falciparum;  Co-Artem (Artemether/ Lumefantrine) may cause hearing loss 

Atovaquone/proguanil: useful in malaria chemoprophylaxis, it acts at both the liver and the blood stage; can cause oral aphthous ulcers; can enhance warfarin anticoagulation; Contraindications: pregnancy, severe renal insufficiency  

Chloroquine: Chloroquine is the drug of choice for the treatment of sensitive non-falciparum and sensitive falciparum malaria; causes generalized pruritis in black people; Contraindications: Psoriasis, epilepsy 

Mefloquine: first-line drug (taken weekly) given for prophylaxis in all geographical areas with chloroquine resistance; most frequent side effects are vivid dreams, mood changes, insomnia; Contraindications: serious psychiatric disease, seizure disorder 

Primaquine: effective against the liver stages, blood stages and gametocytes; Contraindications: pregnancy, G6PD deficiency, all individuals should have G6PD screening prior to treatment

Quinine: Parenteral quinine is used for severe malaria when parenteral artesunate is not available; it is cardiotoxic; can cause Quinine-induced hyperinsulinemic hypoglycemia; blood glucose concentrations should be monitored; can also cause  hypotension, thrombocytopenia, erythematous rash, increased uterine contractions in pregnant women leading to miscarriage 

Quinidine: a diastereomer of quinine and is more toxic; can cause hypotension and QT prolongation; requires electrocardiographic monitoring 

Doxycycline: effective as chemoprophylaxis and treatment; should be taken daily; Side-effects include photosensitivity, gastrointestinal upset, esophageal ulceration. Contraindications: pregnancy, breast-feeding, and children less than 8 years of age

Clindamycin:  is less effective than doxycycline or atovaquone/proguanil; can be used when other drugs cannot be used (pregnant women, young children)

Pyrimethamine-sulfadoxine: it inhibits folate synthesis in the parasite; of little use due to drug resistance