Intestinal Nematodes Flashcards
Characteristics of intestinal nematodes
- They are round
- unsegmented helminths
- bilateral symmetry
- fully functional digestive tract
- usually long and cylindrical
- vary from a few millimeters to over a meter long
- Tapered at both ends
- Those in humans have separate sexes
- Males usually smaller than females
What is Direct infection?
This means that once the egg is ingested and the internal larva has emerged, it develops within the intestinal tract into the adult form
Discuss indirect infection
Indirect- there is extensive migration throughout the body prior to adult worm maturation and egg production
Most prevalent nematodes in Nigeria
Ascaris lumbricoides 54%
Trichuris trichuria 43.7%
Necator Americanus 42.7%
Strongyloides Stercoralis 33%
How many people are estimated to carry nematode infections and what are the risks and morbidities?
World Health Organization (WHO) estimates suggest that over 3.5 billion people carry nematode infections
Risks:
HIV or other immunosuppressive ailments
Poverty!!
Poor sanitation
Climatic
Morbidity: blood loss, malnutrition, and intestinal blockage
What are some Parasitic factors for clinical effect?
- strain of parasite and adaptation to a human host.
- number of parasites (parasite load).
- site(s) occupied in the body
GI Nematodes of clinical importance
• Enterobius vermicularis (pinworm)
• Trichuris trichiura (whipworm)
• Ascaris lumbricoides (human roundworm)
• Ancylostoma duodenale and Necator americanus (human hookworms)
• Strongyloides stercoralis (human threadworm)
• Trichinella spiralis
What is the name of the new world hookworm?
Necator americanus
Length of ascaris lumbricoides
females measure 20 to 35 cm long, and males are 15 to 31 cm long
Describe the life cycle of ascaris lumbricoides
- Humans, ingest egg in food contaminated with human feces
- Eggs move to the duodenum and stomach, then they hatch and release, larvae
- Larvae migrates through the intestinal wall and undergo molting. It is carried to the right heart, into the pulmonary circulation (in 10 days)
- Larvae breaks into the alveoli land migrate into the bronchi into the trachea to the pharynx, and then swallow then re-entered the intestine, larvae mature and mate in small intestine in adults and many eggs are produced by the female 60 million in her lifespan
- eggs are released into stool
- become embryonated in warm moist soil. Ingestion of eggs complete lifecycle
Incubation period of ascaris lumbricoides
When do fertilized eggs become infective?
The entire developmental process from egg ingestion to egg passage from the adult female takes from 8 to 12 weeks.
Often only female worms are recovered from the intestine.
Fertilized eggs become infective within 2 weeks if they are in moist, warm soil, where they may remain viable for months or even years
Describe the fertilized and unfertilized ascaris egg
The fertilized egg is broadly oval, more rounded, with a thick, mammillated coat, usuallybile-stained a golden brown.
These eggs measure up to 75μm long and 50 μm wide.
Unfertilized eggs are usually more oval, measure up to 90 μm long, and may have apronounced mammillated coat or an extremely minimal mammillated layer.
Decorticate
What is the Pathology of ascaris?
Pathology-Ascariasis
the host immune response- (asymptomatism), effects of larval migration, mechanical effects of the adult worms, and nutritional deficiencies due to the presence of the adult worms
Ascaris Pnemonitis
transient pulmonary infiltrates associated with peripheral eosinophilia -Loeffler’s syndrome
Asthma and urticaria may continue during the intestinal phase of ascariasis
Rarely hepatic ascariasis
Worm migration may occur as a result of stimuli such as fever (usually over 38.9°C), the use of general anesthesia,or steroids.
This migration may result in intestinal blockage
bowel perforation and peritonitis, anal passage of worms, vomiting, and abdominal pain.
Diagnosis of ascariasis
Larval migration phase- sputum or gastric washings
Intestinal phase- eggs (iodine/Saline wet mount) or adult worms in stool
Radiology- trolley-car lines
bowel obstruction, biliary or pancreaticduct blockage, appendicitis, or peritonitis
Acute abdomen
Diagnosis of ascariasis
Larval migration phase- sputum or gastric washings
Intestinal phase- eggs (iodine/Saline wet mount) or adult worms in stool
Radiology- trolley-car lines
bowel obstruction, biliary or pancreaticduct blockage, appendicitis, or peritonitis
Acute abdomen
Treatment, prevention, complications, prognosis of ascariasis
Treatment- Adult worm killers
Albendazole or mebendazole -drug of choice
ivermectin and pyrantel pamoate (pregnancy)
Levimasole
Prevention
Sanitation
Faeces as fertilizers
Complications
Low weight
Anaemia
Prognosis
Good but reinfection
What is the nemaode with High prevalence in children
Enterobius vermicularis aka pin worm
pinworm morphology
Female pinworms (about 10 millimeters in length) have a slender, pointed PIN posterior end. Males are approximately 3 millimeters in length and have a curved posterior end
Mode of transmission of Enterobius vermicularis and how does it migrate?
After fertilization of the female worms, the males usually die and may be passed out in the stool
the female migrates down the colon and out of the anus, where they deposit eggs on the perianal and perineal skin
Vaginal migration sometimes
eggs are fully embryonated and infective within a few hours
transmission is often attributed to the ingestion of infective eggs by nail biting and inadequate hand washing
Life Cycle of enterobius vermicularis
Pathology of Enterobius vermicularis and clinical manifestation
Pathology: Enterobiasis
Asymptomatic
PRURITUS via migration of the female worms from the anus onto the perianal skin before egg deposition ……. Hypersensitivity reaction of the eggs
Women and children are more predisposed to symptomatism
+/- eosinophilia
nervousness, insomnia, nightmares, and convulsions
unexplained eosinophilic enterocolitis
Diagnosis of Enterobius vermicularis
Diagnosis
May be clinical; anal itching, irritability and insomnia
Confirmed laboratory by demonstrating the presence of eggs or adult worms
perianal and perineal skin with cellulose tape (Scotch tape) 4X overnight
The tape is transferred to a glass slide and examined under the microscope for the presence of eggs or adult worms
Stool sampling rarely
Treatment of enterobius vermicularis
Treatment
albendazole or mebendazole
ivermectin or pyrantel pamoate
Sanitation and good hygiene
Which nematode is usually seen with Ascaris spp.
Trichuris trichiura aka whip worm
Type of life cycle of whip worm
Direct life cycle
Morphology of Trichuris Trichuria
Adult female whipworms are approximately 30–50 millimeters in length; adult male worms are smaller
360° coil at the caudal extremity
Adult whipworms inhabit the colon, where male and female worms mate
Life Cycle of Trichuris Trichuria
Pathology of Trichuris trichuria
Pathology- Trichuriasis
Asymptomatic
The head portion of the worm is very thin and is embedded in the mucosa, while the posterior end is much thicker and lies free in the lumen of the large intestine
Punctate haemorrhages
Clinical manifestations of trichuriasis
What is the dreaded complication?
Intestinal manifestations-worm burden, the length of the infection, and the age and overall health status of the host
Lower abdominal pain, distention, and diarrhea
chronic dysentery-like syndrome if they have a massive infestation leading to anemia and growth retardation.
Severe infection may lead to profuse bloody diarrhea, cramps, tenesmus, urgency, and RECTAL PROPLAPSE (dreaded complication) the appendix, causing appendicitis
Hypochromic anaemia-blood loss
Dreaded complications of Trchuriasis
rectal prolapse
List examples of hookworms
Ancylostoma duodenale, Necator americanus, and Ancylostoma ceylanicum
Epidemology of hookworm
An estimated 700 million to 900 million people worldwide are infected with hookworm (mostly Ancylostoma duodenale), 0.2% of whom suffer fromsevere anemia
Morphology of hookworm
Adult fem
males measure 7 to 11 mm long
The adult Ancylostoma worm tends to be larger than the Necator worm
Life Cycle of hookworm
Special characteristics of hookworms
Proteolytic enzymes for penetration
Optimal pH
Life cycle similar to Ascaris when in the intestines
This worm attaches to the intestine and feeds on the blood from the capillary-rich lamina propria of the bowel
Pathology of Hookworm and clinical manifestation
Pathology—-Hookworm infection
Worm burden predicts events
Skin penetration
Ground itch—-may become infected (erythema and intense pruritus )
Pneumonitis
Intestinal phase
Necrosis of tissue and blood ingestion
Necator—0.03ml/day; Ancylostoma—0.15-0.2ml/day
Clinically manifested as
fatigue, nausea, vomiting, abdominal pain, diarrhea with black to red stools (depending on the level of blood loss), weakness, and pallor
In chronic infections- iron deficiency anemia (microcytic, hypochromic)
Loefflers Syndrome
Diagnosis of hookworms
Eggs in the stool—non-distinguishable amidst species
Treatment of hookworms
mebendazole, pyrantel pamoate, and albendazole
Iron replacement
Mangement of co-morbidities
Life cycle of Strongyloides stercoralis
Pathology of Strongyloides stercoralis
Pathology- Strongyloidiasis
Point of entry- skin irritation and pruritus in the form of low-grade chronic dermatitis ,
Larva currens
The intestinal manifestations vary from few to no symptoms in light infections to severe necrotizing bowel disease in heavy infections
DDx PUD, crohn’s (eosinophilic granulomatous enterocolitis)
(severe diarrhea, abdominal pain, gastrointestinal bleeding, nausea, vomiting) Loeffler’s pneumonia
How is strongyloidiasis disseminated?
Disseminated Strongyloides infection—organic
Autoinfection
Hyperinfection—-Immunity problem; steroids and human T-lymphotropic virus type 1 (HTLV-1) infection
Gram-negative sepsis
Diagnosis of strongyloidiasis
Rhabditiform larva in stool
Eggs could be seen in profuse diarrhoea
Peripheral Eosinophilia
EnteroTest capsule
Molecular
Serology
Clinical manifestation of chronic strongyloidiasis
chronic disease These symptoms include intermittent vomiting, diarrhea, constipation, and loud gurgling GI noises, Anal pruritus, urticaria and larva currens, rashes, recurrent asthma, and nephrotic syndrome have alsobeen associated with.
Primary and secondary treatment of Strongyloidiasis
Treatment
Ivermectin
Thiabendazole
Mebendazole
Albendazole
What is Trichinella spiralis?
Acquired by eating improperly cooked meat infected with the larval stage
Mating of adult worms occur in the intestine post-maturation
female worms release live larvae
larvae penetrate the intestine, circulate in the blood,and eventually encyst in muscle tissue
Intestinal symptoms: diarrhea, abdominal pain, and nausea
Muscular encystation is the hallmark of Trichinellosis/Trichinosis
Tissue nematode!!!!
What is Trichostrongylus spp.?
Trichostrongylus spp.
Rare in man
Similar to hookworm in structure (but nil jaws) and intestinal habitat (nil lung migration)
Live embedded in the mucosa of the small intestine
Infection in humans is acquired through ingestion of the infective larvae contaminating plant material
Clinical effect—-Worm burden and intestinal damage
Symptoms of Trichostrongylus spp?
Symptoms:
Epigastric pain, diarrhea, anorexia, nausea, dizziness, and generalized fatigue or malaise; eosinophilia is usually present
Cholecystitis
Dx-Egg In stool
Tx- pyrantel pamoate, mebendazole, and albendazole
Ascaris lumbricoides has a migratory phase through the lungs true or false?
True
Ascaris lumbricoides first phase is the lung phase true or false?
False
Intestinal
Ascaris lumbricoides moves from the lungs to the large intestine true or false?
False
It moves from the lungs to the trachea
Coughing, mental regression, and spiked eosinophilia are signs of what?
Loefflers Syndrome
Pneumonitis is secondary to what?
Loefflers Syndrome
In testing for eosinophilia what type of blood count would you request?
Five parts blood count not three part because three parts would not show eosinophils
Enterobius vermicularis has a direct life cycle true or false?
True
Before diagnosing enterobiasis where insomnia is seen in a child a good physician should first rule out what?
OSAS
Obstructive sleep apnea syndrome due to adenoids
What are the phases of pathology for ascaris lumbricoides ?
Lung and intestine
Stercoralis is sophisticated in pathogenesis True or false
True
Stercoralis is sophisticated in pathogenesis True or false
True
Stercoralis has in vivo instantaneous effect in immunocompetent, individuals true or false?
False
Immunosuppressed
Larva currens is a characteristic of what
Dermatitis in strongyloides
What is usually topical for lava currens?
Thiabendazole
