helminth part ii dr samuel aguazim. cestode tape worm taenia saginata intermediate host: cattle...

HELMINTH PART II

DR SAMUEL AGUAZIM

CESTODE• TAPE WORM• TAENIA SAGINATA• INTERMEDIATE HOST: CATTLE• DEFINITIVE HOST: HUMANS• FORMS/TRANSMISSION• - Rare beef containing cysticerci is ingested• Interstinal tapeworm( affects small intestine)• Asymptomatic to vague abdominal pain• Chronic indigestion• Diagnosis: eggs or proglottids in feces• Treatment: praziquantel

TAENIA SOLIUM

• INTERMEDIATE HOST: SWINE• DEFINITIVE HOST: HUMANS• Humans can be both intermediate and

definitive host.• Forms/transmission• Intestinal tape worm• Raw pork containing the cysticerci ingested by

humans

• CYSTICERCOSIS(INTERMEDIATE HOST): Humans ingest eggs directly.

• Water and food contaminated with eggs auto inoculation.

• disease/organ involvement/symptoms• -intestinal tapeworm( same as taenia saginata)• Larvae penetrate intestinal wall and migrate via the

blood to brain, heart, lungs and eye• Diagnosis: eggs or proglottids in feces• Treatment: praziquantel…

T. SOLIUM T. SAGINATA

MOT: INGESTION OF CYSTICERCUS (larval worm) IN PORK/BEEF PRODUCTS

CT Scan of Cysticercosis

DIPHYLLBOTHRIUM LATUM

• INTERMEDIATE HOST: CRUSTACEANS• DEFINITIVE HOST: HUMANS, MAMMALS• HUMANS can be both IH & DH • Forms/transmission• SPARGANUM• Drinking pond water with copepods crustaceans

carrying the larval forms• Intestinal tape worm• Rare, eating raw prickled fish containing sparganum

FISH TAPEWORMDiphyllobothrium latum

longest tapeworm found in man3-10 meters with more than 3000 proglottids.

Fish tapeworm:

Scolex has two elongated sucking grooves; no circular suckers or hooks

Fish tapeworm:

Oval eggs have an operculum (lidlike opening) at one end

MOT: INGESTION OF PLEROCERCOID LARVAE/SPARGANUM IN INFECTED FISH

Copepod

• Disease/organ involvement/symptoms• Sparganosis: larvae penetrate intestinal wall and

encyst• Interstinal tape worm in the small intestine that

absorb vitamin B12 leading to PERNICIOUS ANEMIA

• DIAGNOSIS: Eggs or proglottids in feces• Biopsy for sparganosis• Treatment: praziquantel

Echinococcus granulosus( dog tape worm)

• INTERMEDIATE HOST: HERBIVORES• DEFINITIVE HOST: Carnivores in sheep- raising

area• Humans are intermediate hosts• Forms/ transmission• Ingestion of eggs• Larvae can migrate to anywhere( liver is the

most common place)

Dog tapeworm. Scolex has four suckers and a double circle of hooks.

• Disease: HYDATID CYST DISEASE• Liver and lungs where cyst containing brood capsules develop• Eggs are ingested by sheep (and humans) and hatch larvae

in the gut that migrate in the blood to various organs, especially the liver and brain.

• Larvae form one large, unilocular hydatid cyst containing many minor pathogen and daughter cysts.

• Diagnosis- imaging and serology• Treatment: surgery and albendazole

Echinococcus multilocularis

• IH: RODENTS• DH: CANINES & CATS• HUMANS are intermediate hosts• Forms/transmission• Ingestion of eggs• Larvae can migrate to anywhere( liver is the

most common place)

• Disease: ALVEOLAR HYDATID CYST DISEASE• Much more serious than echinococcus

granulosus : cyst metastasis: exogenous budding cyst

• Diagnosis: difficult: MRI OR CT• TREATMENT: SURGICAL RESECTION

E. Multilocularis multilocular, liver

Hymenolepis nana (dwarf tapeworm)

most frequently diagnosed cestode infection in theUS

small tapeworm infects children Reservoirs: Rodents vague abdominal pain

enteritis Diagnosis :eggs DOC: Nicolsamide

MOT: INGESTION OF EGGS/ CYSTICERCOID IN INSECTS

Spirometra sparganosis MOT: ingest polluted water

raw or inadequately cooked flesh of snakes or frogs

southeastern region of the United States

east Asia (China, Japan, and Korea)

southeast Asia (Malaysia, India, and the Philippines)

Sparganosis

• subcutaneous edema • Muscles• Eyes• urogenital system• abdominal viscera• central nervous system

Sparganosis

• TreatmentSurgical removal of sparganum larvaePraziquantel no available treatment for proliferative sparganosis

Trichuris trichiura 

Disease: Whipworm infection

Characteristics: Intestinal nematode. The characteristic of “whiplike” apperance of the adult worm.

Life cycle: • Humans ingest eggs, which develop into adults

in gut. • Eggs are passed in feces into soil, where they

embryonate, ie, become infectious.

Trichuris trichiura

Transmission: • More than 500 million infected. • Transmitted by food or water contaminated with soil

containing eggs. • Humans are the only hosts. Occurs worldwide, especially

in the tropics.

Pathogenesis:• Worm in gut usually causes little damage.• The whipworm infects about 2 million children in the U.S. • Causes rectal pruritis and tenesmus, which often results

in rectal prolapse.

Infectious DiseasesWhipworm – Rectal Prolapse

Infectious DiseasesWhipworm – Rectal Prolapse

Laboratory Diagnosis: • Eggs visible in feces. • The egg is barrel-shape with a plug at each

end, in the stool.

Treatment: Mebendazole.

Prevention: Proper disposal of human waste

FOOTBALL SHAPE EGG

Trichuris trichiura eggs, a typical barrel shape two polar plugs, that are unstained

LOA LOA

Disease: Loiasis.

Characteristics: Tissue nematode.

Transmission: Transmitted by deer flies. Humans are the only definitive hosts. No animal reservoir. Endemic in central and west Africa.

Pathogenesis: Hypersensitivity to adult worms

causes “swelling” in skin. Adult worm seen crawling across conjunctivas

Laboratory Diagnosis: • Microfilariae visible on blood smear.

Treatment: Diethylcarbamazine.

Prevention: Deer fly control.

Onchocerca

Disease: Onchocerciasis (river blindness). Characteristics: Tissue nematodes.

Onchocerca

Transmission: Transmitted by female black flies. Humans are the only definitive hosts. No animal reservoir. Endemic along rivers of tropical Africa and Central America.

Pathogenesis: Microfilariae in eye ultimately can cause blindness.

Adults induce inflammatory nodules in skin.

Laboratory Diagnosis: Microfilariae visible in skin biopsy, not in blood.

Treatment: Ivermectin affects microfilariae, not adult worms. Suramin for adult worms.

Prevention: Black fly control and ivermectin

RIVER BLINDNESS/SOWDA

trapped microfilaria in the cornea, choroid, iris and anterior chambers, leading to photophobia, lacrimation and blindness

Toxocara canis

Disease: Visceral larva migrans. Characteristics: Nematode larvae causedisease.

Life cycle: • Toxocara eggs are passed in dog feces• Ingested by humans. • Hatch into larvae in small intestine• Larvae enter the blood and migrate to organs,

especially liver, brain, and eyes, where they are trapped and die.

Transmission: • ingestion of eggs in food or water contaminated with

dog feces. • Dogs are definitive hosts. Humans are dead end

hosts. Pathogenesis: Granulomas form around dead

larvae. Granulomas in the retina can cause blindness

Laboratory Diagnosis: Larvae visible in tissue. Serologic tests useful.

Treatment: Diethylcarbamazine

Prevention: Dogs should be dewormed

Tissue nematodeDracunculus

Disease: Dracunculiasis. Characteristics: Tissue nematode.

Dracunculiasis

Transmission:

• copepods in drinking water. • Humans are definitive hosts.• Many domestic animals are reservoir hosts. • Endemic in tropical Africa, Middle East, and India

Pathogenesis: • Adult worms in skin cause inflammation and ulceration.

Treatment:• Niridazole.• Extraction of worm from skin ulcer. Prevention: • Purification of drinking water

Dracula ate an infected crustacean and got an ulcer with protruding worm.

He removed the worm by winding it around a stick.

Strongyloides

Disease: StrongyloidiasisCharacteristics: Intestinal nematode.

• NOTE: the only helminth to secrete larvae (and not eggs) in feces

Transmission: Filariform larvae in soil penetrate skin. Endemic in the tropics.

Pathogenesis:• Little effect in immunocompetent persons. • In immunocompromised persons, massive superinfection can

occur accompanied by secondary bacterial infections.

Laboratory Diagnosis: Larvae visible in stool. Eosinophilia occurs.

Treatment: Thiabendazole. Prevention: Proper disposal of human waste. Use of footwear

Memory Tool

• The strongman (Strongyloides) is brought down by a larvae penetrating his skin causing pulmonary distress and superinfection. Poor strongman!

ANCYLOSTOMA BRAZILIENSEANCYLOSTOMA CANINUM

• DOG and CAT Hook worm• Forms/ Transmission.• Filariform larvae penetrate intact skin but cannot

mature in humans• Disease/organ most affected• Cutaneous larvae migrans: intense itching• Tunnels through tissue• Diagnosis: clinical signs• Treatment- ivermectin