Helminths and Nematoda

Helminths

• Are multicellular organisms with internal organ systems.
• Nematodes are the first group of helminths discussed
• They are commonly known as intestinal roundworms.

Nematoda Morphology and Life Cycle

• Nematoda are multicellular parasites that appear round in cross-section.
• They may assume three basic morphologic forms: eggs, juvenile worms known as larvae, and adult worms
• Eggs vary in size and shape
• Developing larvae are located inside fertilized eggs.
• They emerge and continue to mature in the appropriate environment.
• Larvae are typically long and slender
• Growing larvae complete the maturation process, resulting in the emergence of adult worms
• Sexes are separate
• Adult female worms are usually larger than the adult males
• Adults are equipped with complete digestive and reproductive systems
• Specific features vary with the individual species
• Life cycles are similar but organism-specific
• An intestinal nematode infection may be initiated in several ways
• Pinworms, for example, are transmitted via ingestion of the infected eggs.
• Hookworm larvae burrow through the skin of the foot and make way into the intestinal tract.
• The means whereby organisms enter the host and migrate into the intestinal tract varies by species
• Eggs or larvae continue to develop into adulthood, depending on the species
• Adult worms reside in the intestine, obtaining nutrition and reproducing
• Fertilized adult female nematodes lay their eggs in the intestine
• Eggs may be passed into the stool
• Once outside the body, the larvae located inside the eggs require warm moist soil and 2 to 4 weeks for continued development
• The developed egg will then be ready for infection into a new host and the cycle is repeated
• In two of the nematode life cycles, Trichinella and Dracunculus, tissue becomes involved, serving as the primary residence of the organisms
• Most nematodes can exist independent of a host.
• Each nematode organism's life cycle is addressed on an individual basis

Laboratory Diagnosis

• May be accomplished by the recovery of eggs, larvae, and occasional adult worms
• Specimens of choice vary by species
• Specimens include cellophane tape preparations taken around the anal opening, stool samples, tissue biopsies, and infected skin ulcers
• Serologic test methods are available for the diagnosis of select nematode organisms

Pathogenesis and Clinical Symptoms

• Three factors contribute to the severity of a nematode infection: the number of worms present, the length of time the infection persists, and the overall health of the host
• Infections last up to 12 months or longer, or 10 to 15 years or more, depending on the species
• Reinfections or autoinfections may increase the infection time up to several years and beyond
• Some infections persist indefinitely
• An infection of a small number of worms in a healthy individual may remain asymptomatic or cause minimal discomfort
• Patients with a heavy worm burden who have other health problems are more likely to experience severe symptoms and/or complications
• The life cycle involves the intestinal tract
• All nematodes, with one exception, may cause intestinal infection
• Symptoms include abdominal pain, diarrhea, nausea, vomiting, fever, and eosinophilia.
• Skin irritation, skin blisters, and muscle involvement may be present.

Nematode Classification

• Nematodes belong to the phylum Nemathelminthes
• The placement of Nematoda varies by source, listing it as a phylum, order or class
• Nematoda is considered as a class just like all of the helminth groups covered in this text
• Nematode species divided into intestinal species, and those that migrate into the tissues, termed intestine tissue species

Enterobius vermicularis (Pinworm)

• Common names: Pinworm, seatworm
• Associated disease and condition names: Enterobiasis, pinworm infection

Morphology

• Eggs measure 48 to 60 um in length by 20 to 35 µm in width
• The oval egg is characteristically flattened on one side
• Consists of a developing larva surrounded by a conspicuous double-layered, thick-walled colorless shell.
• Can be seen at various stages of development: unfertilized egg, fertilized egg, and mature egg
• The adult female E. vermicularis worm measures 7 to 14mm in length by up to 0.5 mm wide
• Yellowish-white females are equipped with primitive organ systems, including digestive tract, intestinal tract, and reproductive structures
• Adult female possesses a clear, pointed tail

Life Cycle Notes

• Humans are the only known host of E. vermicularis.
• Infection, initiated following the ingestion of the infective eggs, is usually self-limiting
• Eggs migrate through the digestive tract into the small intestine, where they hatch and release young larvae
• Larvae grow and mature, transforming into adult worms
• Worms reside in the colon
• Following mating of select worms (copulation), the gravid female worm migrates outside the body to the perianal region, depositing up to 15,000 eggs
• Following 4 to 6 hours incubation, the developing eggs achieve infective status.
• Eggs dislodge from the body, caused at least in part by intense scratching of the anal area by the infected person
• Eggs may take up residence in a number of locations, including dust, sandboxes, linens, and clothing
• Eggs may become airborne
• Infective eggs under suitable environmental conditions can survive for a few days up to several weeks
• New cycle can be initiated by ingestion of these infective eggs
• A retroinfection is infective pinworm eggs that migrate back into the host body, develop and reproduce rather than becoming dislodged
• Infected individuals may reinfect themselves if infective pinworm eggs are ingested via hand-to-mouth contamination

Epidemiology

• Found worldwide, particularly in temperate areas
• Is considered by many to be the most common helminth known to cause infection in the United States
• White children appear to be at the greatest risk
• Transmission occurs primarily by hand-to-mouth contamination
• E. vermicularis may be responsible for the transmission of Dientamoeba fragilis

Clinical Symptoms

• Many cases are asymptomatic
• Enterobiasis: Pinworm Infection
• Symptoms include intense itching and inflammation of the anal and/or vaginal areas
• Symptoms accompanied by intestinal irritation, mild nausea or vomiting, irritability, and difficulty sleeping
• Minute ulcers as well as mild intestinal inflammation and abdominal pain may occur

Prevention and Control

• Practice proper personal hygiene, particularly hand washing
• Apply ointment or salve to infected perianal area to help prevent egg dispersal into the environment
• Avoid scratching the infected area
• Thoroughly clean potentially infected environmental surfaces, including linens
• Provide treatment to all household members
• Eradication is unlikely in the near future

Treatments

• Albendazole, mebendazole, or pyrantel pamoate are the treatment of choice
• Treatment is suggested for household members

Trichuris trichiura (Whipworm)

• Common names: Whipworm.
• Common associated disease and condition names: Trichuriasis, whipworm infection.

Morphology

• Egg measures 50 to 55 µm by 25 μm
• An egg is barrel-shaped (football-shaped)
• Undeveloped unicellular embryo is surrounded by a smooth shell
• A smooth shell retain a yellow-brown color when in contact with host bile
• A prominent hyaline polar plug is visible at each end
• The adult whipworm measures 2.5 to 5 cm in length
• Anterior end of the adult appears colorless and contains a slender esophagus
• Posterior end assumes a pinkish-gray color, consisting of the intestine and reproductive systems
• Male is usually smaller than the adult female
• The male posseses an easily recognizable curled tail.

Morphology

• Possesses a digestive system, intestinal tract, and reproductive organs
• The large posterior end resembles that of a whip handle.
• The anterior end looks like the whip itself.

Laboratory Diagnosis

• Recover T. trichiura eggs from stool
• Eggs are readily apparent in infected samples processed using the zinc sulfate flotation method (described in Chapter 2).
• Adult worms may be visible on macroscopic examination of the intestinal mucosa
• Adults may also be seen in the intestinal tract down to the rectum in heavy infections
• Samples examined from patients treated may reveal distorted worm eggs

Life Cycle Notes

• Infection initiates in humans that consume the larvae containing eggs
• Larvae emerge from the eggs in the small intestine
• Development occurs as they migrate within the intestinal villi
• Larvae go to the cecum where they complete their maturation
• Adults embed in the mucosa and take residency in the colon
• In untreated infections, the lifespan can be up to 8 years
• After copulation, the female lays undeveloped eggs. It is this stage of the egg that is passed in the feces
• The eggs become infective and embryonate after a month in the soil outside of the human body and is ready to start the cycle all over again

Epidemiology

• Is the third most common helminth
• Can primarily be found in warm climates where open defecation is practiced and human feces is used as fertilizer
• People at risk for contracting the infection are children or those that reside in psychiatric facilities

Clinical Symptoms

• Patients suffering from a slight T. trichiura infection will often remain asymptomatic
• Heavy infections of 500 to 5000 worms produces a variety of symptoms that differ with age
• Ulcerative colitis can occur with those infected along with chronic dysentery, anemia and growth retardation
• Treated children return to normal growth rates
• Adults experience inflammatory bowel disease
• Common symptoms: abdominal tenderness and pain, weight loss, weakness, and mucoid or bloody diarrhea.

Treatment

• The treatments of choice are Mebendazole or albendazole.

Prevention and Control

• Prevent the spread by exercising proper sanitation practices by 1) avoid putting feces in the soil directly and 2) the use of proper personal sanitation practices

Ascaris lumbricoides

• Roundworm (Name)
• Large intestinal roundworm, roundworm of man (Common names)
• Ascariasis, roundworm infection (Associated disease and condition names)

Morphology

• Infertilized eggs- typically measures 85 to 95 µm by 38 to 45 µm
• Inner mass and sheds
• Cortication (possesses outer mammillated coating)
• Fertilized egg- measures 40 to 75 µm by 30 to 50 μm
• Transformation of protplasm.
• Chitin (coating)
• Decorticated (lacking outer mammillated)
• Adults assume creamy white color with pink tint
• Largest nematode
• Male (30cm in legnth vs 22-35 in the female)

Laboratory Diagnosis

• Stool sample for eggs recovery in order to begin diagnosis
• The intestinal,gallbladder,liver, and appendix can also give A. Lumbricoides
• Stool sample or removed from external nares
• ELISA can be used

Life Cycle

• Complex cycle -The ingested eggs turn into larva in the small intestine where they emerge
• Liver- lung migration by entering the blood by going through the intestine wall
• Lungs help the burrough the capillaries into the alveoli and in the bronchioles which lead to a cough to transition into the pharynx where saliva is ingested
• Results in adult worms that reside in the small intestine
• Eggs that are unveloped can be produced by adults (250k day)
• The environment helps the eggs to embryonate
• eggs or any of the fecal matter water is easily destroyed by chemicals

Epidemiology

• Most common intestine infection known, affecting 1 billion people
• US ranks 2nd in frequency
• A.Lumbricoides harbors similar
• Most susceptible are those from The Appalachian The population children who put thier hands in their mouths

Clinical Symptoms

• Often asymptomatic
• Roundworm infection
• Tissue deconstruction
• Symptoms by the infection Vague abdominal pain vomiting fever distention

Treatments

• Medication consist of medicine meant for killing parasitic worms and parasites.
• Albendazole, mebendazole

Prevention and Control

• Avoidance of human feces as fertilizer or personal hygiene is critical in the breaking of the cycle

Hookworms

• Necator americanus (ne-kay'tur/ah'merr"i-kay'nus): New world hookworm - Ancylostoma duodenale (an"si'ios'tuh'muh/dew"o-de-nay'lee): Old World hookworm
• Common associated disease and condition names: Hookworm infection, ancylostomiasis, necatoriasis Morphology
• Eggs are recovered and considered indistinguishable
• Adult worms each have minor morphologic differences for eggs and larva stages

Morphology

• Necator 60 to 75Um whereas the tipical egg measure 55 to 60Um
• Smooth egg with cleavage that provides protection
• At a minimum double the length , morphologic form is characterized by having oral cavity that is know as buccal capsule

Hook- Worm Laboratory Diagnosis

Filariform

• Slim short esophagus
• Adults grayish -white is the bending area (hook area)
• N.americnus- contains plates
• a. duodenale contins teeth
• Recovery in stool samples is very popular

Life Cycle

• Migrate into the lymphatic and food system
• Bronchioles where they enter into the alveoli
• Intestine is where the larva results
• Females lay 10k-20k day
• Two - 3rd stage is required for the condition to persist
• the larvae need to molt up to 2 times in the feces
• Third infection larvae results need to begin the cycle- The penetration of the skin need to occur at an alarmingly quick pace

Epidemiology

• 25% is affected by hookworm due to proper sanitation practices
• N,Americanus -south and north America Africa and china
• A. Duodenale. - China African and south america

Clinical symptom

• Light hookworm doesn't exhibit
• A.duodenale has adapted Ground itch migration into lungs- soar throat,blood sputum a cough and soar throat blood sputum

Treament

• Anemia
• protein vitamins
• Mebendazole is used as well as - pyrantel pamoate

Prevention and control

• Protection-feet covers , appropriate feeding location

Strongyloidiasis stercoralis

• (threadworm)

Morphology

• Eggs are identical
• Larve are contained
• Rhabditiform measure 22o -small

Lab

• E.Test
• Spotum also has a similar egg to the hookworm (can also be transferred through the the the the the THE ENTEROTEST)
• Recovery can be helped by the by using flotation

Life cycle Notes

• There are three cycles- direct- hookworm is identical
• in which a rhabdiitiform is a hookworm
• indirect- the egg is a parasite, and is excreted to the fecal matter
• in short similar to

Trichinella spiralis

• (Trichina worm) Common associated disease and condition names: Trichinosis, trichinellosis.

Morphology

• Average Size- juvenile and measure 7
• 125um - (small)

Muscle Biop

• The larvae create infultrates and settl to cause infultrates to spread across the muscle
• Small Has no mouth
• Male features :has curves and 2 appendages- in which possess two ovaries and Vulva
• There are a few enzyme tests but nothing known

The cycle

• Animals primarily from striated muscle
• This occur as a number of zoonasies
• Digestion happens
• Mating cycle occurs very quick

Clinical symptom

• Trichinosis affects the body causes a variety of conditions (symptoms ) such as flus small fever Muscular discomfort Overall weakness Inflammation in striated muscle and face limb

Treatments

• The person can take pain relievers
• Or in some other circumstances steroids can be used

Prevention and control

• Thorough cooking,storage, and avoiding the contamination cycle

D.medinensias

• The test in the form of first is the diagnostic form the 1.5 the first size
• Tail will then 1/3

Diagnosis of Worms

• This step is to check the emergence and ruption of infection from
• Water intake can lead to human infection with fresh water which contains infection. THey then create larva in the intestine Subcutaneous tissues worms can then migrate due to larva site
• Humans create an infected ulcer which causes copepods to live in the area causing them to drink more larvae from other regions which continues to cause cycle

Treatmets

• take the effective area put in a bister in col water
• Step 2 is the the worm out daily
• Step 3-is to continue until all of the worms are out
• Antiomicrobals