Helminths

Kingdom Animalia Sub-kingdom Invertebrata I. Phylum Platyhelminthes - flatworms II. Phylum Nematoda - roundworms III. Phylum Annelida - segmented worms IV. Phylum Arthropoda

Phylum Platyhelminthes flatworms A. Class Cestoda -tapeworms  1. Taenia ­pisiformis. - head (scolex) and segments (proglottids) may be on; separate slides. Label: scolex, suckers, hooks if present, proglottid, testes, ovaries B. Class Trematoda - Flukes 2. Clonorchis sinensis - liver fluke; Label: oral sucker, pharynx, intestines (cecum), uterus, testes 3. Fasciolopsis buski - giant intestinal fluke Label: mouth, ventral sucker, intestines (cecum), testes 4. Schistosoma mansoni female blood fluke; ventral sucker, ovary, mouth C. Class Turbellaria - free-living flatworms, ie. not parasitic 5. Planaria spp. Label: pharynx, eyespots, gastrovascular cavity

. Phylum Nematoda roundworms 6. Enterobius vermicularis female – pinworm; Label: mouth, pharynx 7. Ascaris lumbricoides - intestinal round worm- plastimount; Label: male, female Necator americanus- American hookworm; Label: teeth, muscular pharynx, posterior bursa and rays (male) 9. Trichinella spiralis- threadworm encysted in muscle; Label: cyst, muscle, larva

Phylum Annelida segmented worms Class Hirudinea 10. Leech; Label: anterior sucker, mouth, intestine, posterior sucker

Phylum Arthropoda Class Arachnia Class Insecta

Class Arachnia 11. Dermacentor spp.- tick; Label: head, thorax, abdomen, legs Sarcoptes scabiei - itch mite; Label: mouth, legs, bristles on rear legs, bristles on abdomen Dermatophagoides spp.- dust mite; Label: thorax, legs, abdomen

Class Insecta 14. Flea; Label: head, thorax, abdomen, legs Pediculus humanis corporus - human body louse; Label: abdomen, thorax, head, antennae, eyes, plates, legs Pthirus pubis- crab louse; Label: thorax, abdominal segments, eyes, legs, antennae

Taxonomy Phylum: Platyhelminthes (Flatworms) Class: Cestodes (tapeworms) Pork tapeworm (Taenia solium) Beef tapeworm (Taenia saginata) Fish tapeworm (Diphyllobothrium latum)

Characteristics of Tapeworms Monoecious Missing an entire system Scolex: suckers, hooks, or grooves Segmented proglottids Gravid proglottids Strobilia Uterine branches

Beef Tapeworm Scolex

Pork Tapeworm Scolex

Pork Tapeworm Scolex

Pork Tapeworm Scolex

Pork Tapeworm Uterine branches in proglottid

Beef Tapeworm Uterine branches in proglottid

Pork and Beef Tapeworm Diseases 1. TAENIASIS (Pork and Beef) 2. CYSTICERCOSIS (Pork only)

Life Cycle:                                                                                    Taenia

Tapeworms inside intestines

Taenia Egg

Taenia Egg

CYSTICERCOSIS

Broadfish Tapeworm Operculated eggs contain ciliated coracidium. Copepods eat the coracidium. They become procerocoid larvae Minnows eat the copepod. Predator fish eat the minnows. Humans eat the predator fish. The infective stage is in the fish.

Broadfish Tapeworm The larvae are released from the cysts. They invade the intestines and mature. They attach by bilateral grooves called brothria. The proglottids are passed in the feces, and return to the water. They become embryonated and become operculated eggs.

Fish Tapeworm Bilateral grooves

Fish Tapeworm Proglottids

Operculated Broadfish Tapeworm (Diphyllobothrium) egg. Operculum Has a ciliated coracidium inside Knob

Diphyllobothrium Egg Operculum Knob

Diphyllobothrium Egg Operculum Knob

Diphyllobothrium Egg

Copepod

Walleye Pike

Taxonomy Phylum: Platyhelminthes (Flatworms) Class: Trematodes (flukes) Schistosomes S. japonicum S. mansoni S. haematobium

Schistosoma spp. Schistosomiasis

Schistosoma spp. Eggs are eliminated with feces or urine. The eggs hatch and release miracidia, which swim and penetrate specific snail intermediate hosts.  The stages in the snail include 2 generations of sporocysts and the production of cercariae (which have a forked tail). Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host, and shed their forked tail, becoming schistosomulae. 

Schistosomal miracidum

Schistosoma cercariae

Schistosoma spp. The schistosomulae migrate to the veins: S. japonicum and S. mansoni inhabit the mesenteric veins draining the intestines. S. haematobium inhabit the urinary bladder venous plexus. The females are smaller and live inside the male. They deposit eggs in the small venules. The eggs are moved progressively toward the lumen of the intestine and are eliminated with feces or urine.

Schistosoma

Schistosoma Male Female

Schistosoma spp. Human contact with water is thus necessary for infection by schistosomes.  Skin penetration is required. Various animals, such as dogs, cats, rodents, pigs, horse and goats, serve as reservoirs, but skin penetration is still required. Geographic Distribution: Schistosoma mansoni is found in parts of South America and the Caribbean, Africa, and the Middle East; S. haematobium in Africa and the Middle East; and S. japonicum in the Far East.  Schistosoma mekongi and S. intercalatum are found focally in Southeast Asia and central West Africa, respectively.

Schistosoma spp. Symptoms include: Katayama fever, granulomas (occasionally in brain or spinal cord).  S. haematobium schistosomiasis also includes: hematuria, and bladder cancer.

Life Cycle:                                                                               

Types of Schistosoma eggs S. mansoni S. haematobium S. japonicum

Schistosoma haematobium egg

Schistosoma haematobium egg

Schistosoma mansoni egg

Schistosomiais

Swimmer’s Itch

Schistosomiais: Swimmer’s Itch

Taxonomy Phylum: Nematodes (roundworms) Pinworm Whipworm Hookworm Intestinal Roundworm Pork Roundworm

Pinworm Enterobius vermicularis

Life Cycle:                                                                  

Pinworm Eggs are deposited on perianal folds.  Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area.  Person-to-person transmission can also occur through handling of contaminated clothes or bed linens or contact with contaminated curtains, carpeting, etc. Some small number of eggs may become airborne and inhaled.  These would be swallowed and follow the same development as ingested eggs.  Following ingestion of infective eggs, the larvae hatch in the small intestine and the adults establish themselves in the colon.  Gravid females migrate nocturnally outside the anus and deposit their eggs while crawling on the skin of the perianal area. 

Pinworm Geographic Distribution: Worldwide, with infections more frequent in school- or preschool- children and in crowded conditions.  Enterobiasis appears to be more common in temperate than tropical countries.  The most common helminthic infection in the United States (an estimated 40 million persons infected).

Pinworm Female

Enterobius vermicularis egg

Pinworm

Pinworm Esophageal bulb Esophagus Alae

Pinworm adult Alae Esophagus Esophageal bulb Eggs

Pinworm

Whipworm Trichuris trichiura

Life Cycle:                                                                  

Trichuris trichiura The unembryonated eggs are passed with the stool.  In the soil, the eggs become infective.   After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae that mature and establish themselves as adults in the colon.   Female worms in the cecum shed up to 20,000 eggs per day.  The life span of the adults is about 1 year. Geographic Distribution: The third most common round worm of humans worldwide, with infections more frequent in tropical areas and poor sanitation practices, and among children.  It is estimated that 800 million people are infected worldwide.  Trichuriasis occurs in the southern United States.

Whipworm

Prolapsed Rectum from whipworm

Prolapsed Rectum from whipworm

Whipworm egg

Whipworm egg

Whipworm, female and male

Hookworm Ancyclostoma duodenale Necator americanus

Life Cycle:                                                                                       

Hookworm Eggs are passed in the stool. The released rhabditiform larvae grow in the feces and/or the soil, and after 5 to 10 days they become filariform larvae that are infective. These infective larvae contact the human host, penetrate the skin and are carried through the veins to the heart and then to the lungs.  They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine, where they reside and mature into adults.  Adult worms attach to the intestinal wall with resultant blood loss by the host. 

Hookworm Geographic Distribution: The second most common human helminthic infection (after ascariasis).  Worldwide distribution, mostly in areas with moist, warm climate.  Both N. americanus and A. duodenale are found in Africa, Asia and the Americas.  Necator americanus predominates in the Americas and Australia, while only A. duodenale is found in the Middle East, North Africa and southern Europe.

Male hookworm

Copulatory Bursa of Male Hookworm

Copulatory Bursa of Male Hookworm

Hookworm cutting plates Necator americanus

Hookworm teeth Ancyclostoma duodenale

Hookworm teeth Ancyclostoma duodenale

Hookworm egg

Hookworm egg

Hookworm: creeping eruption

Ascariasis Ascaris lumbricoides

Life Cycle:                                                                  

Ascariasis Adult worms live in the lumen of the small intestine.  A female may produce approximately 200,000 eggs per day, which are passed with the feces After infective eggs are swallowed, the larvae hatch, invade the intestinal mucosa, and are carried to the lungs.  The larvae penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed.   Upon reaching the small intestine, they develop into adult worms.  

Ascariasis Geographic Distribution: The most common human helminthic infection.  Worldwide distribution.  Highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation.  Occurs in rural areas of the southeastern United States.

Ascariasis

Ascariasis

Ascaris Adult

Ascaris egg

Ascaris egg

Trichinellosis Trichinella spiralis

Life Cycle:                                                                  

Trichinellosis Trichinellosis is acquired by ingesting meat containing cysts (encysted larvae) of Trichinella.  After exposure to gastric acid, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms. The females release larvae that migrate to the striated muscles where they encyst.  Ingestion of the encysted larvae perpetuates the cycle.  Rats and rodents are primarily responsible for maintaining the endemicity of this infection.  Pigs or bears feed on infected rodents.  Humans are accidentally infected when eating improperly processed meat of these carnivorous animals (or eating food contaminated with such meat). Geographic Distribution: Worldwide.  Most common in parts of Europe; in the United States, it is most common in Alaska from eating infected bear meat.

Trichinellosis Eosinophilia develops in response to the presence of the worm. Patients who develop neurologic and cardiac dysfunctions have marked hypereosinophilia associated with arteriolar microthrombi leading to areas of cerebral and myocardial infarction. Immunologic reactions also are deemed responsible for one of the hallmark clinical findings—palpebral edema. The direct trauma of the larva encysting in muscle cells, coupled with the immunologic response, is responsible for other clinical features (eg, fever, myalgias). Ultimately, the intramuscular cysts typically calcify.

Trichinella cyst

Trichinella cysts

Filariasis Caused by nematodes that produce a thread-like larvae called microfilariae. They inhabit the lymphatic system of humans. They require the bite of a mosquito.

Elephantitis Wuchereria bancrofti Mosquito: anopheles or Culex (Asia) Blocks lymph drainage

Life Cycle of Wuchereria bancrofti:                                                                             

Elephantitis During a blood meal, an infected mosquito introduces filarial larvae onto the skin of the human host, where they penetrate into the bite wound.  They develop in adults that commonly reside in the lymphatics.  The microfilariae migrate into lymph and blood channels moving actively through lymph and blood.  Another mosquito ingests the microfilariae during a blood meal and work their way to the mosquito's midgut and develop into infective larvae.  The infective larvae migrate through to the mosquito's prosbocis and can infect another human when the mosquito takes a blood meal.

Elephantiasis

River Blindness Onchocerca volvulus Requires bite of Black Fly (Simulium) Itchy nodules under skin and head Treatment is Ivermectin

Life Cycle of Onchocerca volvulus:                                                                               

River Blindness During a blood meal, an infected blackfly (genus Simulium) introduces filarial larvae onto the skin of the human host, where they penetrate into the bite wound.   In subcutaneous tissues the larvae develop into adult filariae, which commonly reside in nodules in subcutaneous connective tissues.  Adults can live in the nodules for approximately 15 years.  Some nodules may contain numerous male and female worms.  Some of them get into the bloodsteam. Another blackfly ingests the microfilariae during a blood meal and migrate to the thoracic muscles.  There they develop into infective larvae and migrate to the blackfly's proboscis and can infect another human when the fly takes a blood meal.

River Blindness

River Blindness

River Blindness

Guinea Worm Dracunculus medinensis Geographic Distribution: Restricted to rural, isolated areas in a narrow belt of African countries.

Life Cycle:                                                                                         

Guinea Worm Humans become infected by drinking unfiltered water containing copepods (small crustaceans) which are infected with larvae of D. medinensis. Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space.  After maturation into adults and copulation, the male worms die and the females migrate in the subcutaneous tissues.  Approximately one year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures.  When this lesion comes into contact with water, the female worm emerges and releases larvae.  The larvae are ingested by a copepod and develop into infective larvae. 

Guinea Worm

Loa loa The “eye worm”

Life Cycle of Loa loa:                                                                        

Loa loa The vector for Loa loa filariasis are flies from two species of the genus Chrysops, C. silacea and C. dimidiata.  During a blood meal, an infected fly (genus Chrysops, day-biting flies) introduces filarial larvae onto the skin of the human host, where they penetrate into the bite wound.  The larvae develop into adults that commonly reside in subcutaneous tissue but can migrate into spinal fluids, urine, and sputum. During the day they are found in peripheral blood, but during the noncirculation phase, they are found in the lungs.  The fly ingests microfilariae during a blood meal, which migrate to the thoracic muscles and develop into infective larvae.  They migrate to the fly's proboscis and can infect another human when the fly takes a blood meal.

Loa loa

Loa loa

Loa loa

“My worm collection”