nematodes pt.2 Flashcards
what are the 2 organism of Hookworm and its associated diseases
Necator americanus (New World Hookworm)
2. Ancylostoma duodenale (Old Worm Hookworm)
associated diseases:
○ Hookworm infection
○ Ancylostomiasis
○ Necatoriasis
briefly explain the different morphologic forms of hookworms
transes
eggs > rhabditiform larvae (L1 & L2) > filariform larvae L3 > adult worm
non infective stage in hookworm
Rhabditiform Larvae
- need nutrition in order to grow to infective stage
what do Rhabditiform Larvae feed on
organic matter
bacteria
soil
the outer covering or cuticle of the organism is shed in order to develop into the next stage, not yet mature
molting
What happens after L2 in hookworm spp.
undergoes another molting process to become an infective filariform larva (L3).
A long oral cavity present in rhabditiform larvae
buccal cavity
- present in hookworms
Precursor structure to a reproductive system consisting of a clump cells in an ovoid formation
Small genital primordium
infective and non feeding stage in hookworm
Filariform Larvae (L3)
- long and slender body
- hhave shetah that protect itself from the outside environment
- has distinct pointed tail
- actively seeks a host
true or false:
hookworms have a longer esophagus length than S. stercoralis
false - shorter
this stage is rarely seen in hookworms
adult
morphology of adult hookworm
Grayish-white to pink in color with somewhat thick cuticle
Anterior end: forms a conspicuous bend, referred as hook
- More pronounced in N. americanus than A. duodenale
this form is equipped with prominent, posterior, umbrella-like structure that aids in copulation
male hookworm
- that is known as copulatory bursa
primary laboratory diagnosis method for hookworms
recovery of hookworm eggs in stool
- larvae may mature and hatch from the eggs in stool that has been allowed to sit at room temp w/o fixative (hence need to be examined immediately)
Why is it important to differentiate hookworm larvae from Strongyloides stercoralis?
ensure proper diagnosis and treatment
What structure is examined to determine the specific hookworm species?
buccal capsule
- in Necator americanus: Cutting plates
- in Ancylostoma duodenale: Teeth-like structures
how to maintain the asymptomatic hookworm infection state
adequate rich in iron, protein and other vitamins
briefly explain the hookworm disease
Ancylostomiasis & Nectoriasis
- ground itch
symptoms associated with:
1. lung migration
soar throat
bloody sputum
wheezing
headache
mild pneumonia w cough
- intestinal infection
*depend on the no. of worms present
- chronic (light worm burden)
mild gastrointestinal symptoms
slight anemia
weight loss
weakness - acute (heavy worm burden)
diarrhea
anorexia
edema
pain
enteritis
epigastric discomfort
microcytic hypochromic iron deficiency
weakness
hypoprotenemia.
allergic itching at the site of hookworm penetration when a patient is repeatedly infected.
Ground itch
what is the egg count in
chronic (light) hookworm infection:
acute (heavy) hookworm infection:
<500 eggs/g of feces
>5,000 eggs/g of feces
life cycle of hookworms
- Humans contract hookworm when third-stage filariform larva (L3) penetrate through the skin.
○ Infective stage to humans: L3
○ Penetration of the skin: unprotected feet of the patient - Inside the body, L3 migrates to the lymphatics and blood system.
- Blood carries the larvae to the lungs, where they penetrate the capillaries and enter the alveoli.
- Migration of larvae continues into the bronchioles, where they are coughed up to the pharynx, subsequently swallowed, and deposited into the intestine.
- Larvae mature into adult hookworms in the intestine, where they also live and multiply.
- An adult female lays 10,000 to 20,000 eggs/day.
- Many of the eggs are passed into the outside environment via feces.
- Within 24-48 hours under appropriate conditions, first-stage rhabditiform larva (L1) emerge.
○ Appropriate condition: warm, moist soil - The larvae continue to develop by molting twice.
- L3 results and are ready to begin a new cycle.
epidemiology of hookworms
estimated that 25% of the world’s
population is infected w hookworm
frequency of infections in highwarm areas whr thr r poor sanitation practices
unholy three
hookworm
Trichuris
Ascaris
- mixed infection w any combination of these
who are the person at risk of getting hookworm infection
who walk barefoot in feces-contaminated soil
treatment in hookworms
drug of choice:
Mebendazole
Pyrantel pamoate
asymptomatic hookworm infection:
Iron replacement
Dietary therapy
prevention and control for hookworms
Similar to those for A. lumbricoides.
Proper sanitation practices
- fecal disposal
Prompt and thorough treatment of infected
Personal protection of person entering endemic areas
- covering bare feet
what are the other species of hookworms known to infect humans accidentalu
Ancylostoma braziliense
– parasite of dogs and cats
Ancylostoma caninum
– parasite of dogs only
*when they infect humans, these organisms are unable to complete their life cycle, infecting the subcutaneous or skeletal tissue
infection caused by theAncylostoma braziliense and Ancylostoma caninum
Cutaneous Larva Migrains
- skin lesions and intense itching = sec bacterial infections
- lesions resemble creeping worms through skin
*treatment of choice: Thiabendazole
Strongyloides stercoralis
Common name: Threadworm
Common associated disease:
○ Strongyloidiasis
○ Threadworm infection
true or false:
eggs in S. stercoralis is indistinguishable from those of hookworms and bigger
false - slightly smaller
morphology of S. stercoralis eggs
48 µm long, 35 µm wide
Contain well-developed larvae
Show embryonic cleavage (two-, four-, or eight-cell stage)
Thin hyaline shell
key features of rhabditiform larvae (L1-L2)?
short buccal cavity and prominent genital primordium
- opposite with hookworms
*active feeding stage
How do S. stercoralis rhabditiform larvae differ from hookworms?
S. stercoralis has a short buccal cavity and a prominent genital primordium
Hookworms have a long buccal cavity and small genital primordium
Refers to the ability of female worms to reproduce without the need for fertilization by a male
Parthogenic
- seen in adult female worm in S. stercoralis
which form of S. stercoralis can it penetrate the skin
Filariform Larvae (L3)
the morphology of adult female worm of S. stercoralis
- short buccal cavity with long and slender esophagus
- colorless body that appears almost
transparent - parthogenic
laboratory diagnosis, S. stercoralis: how to successfully recover the
- Eggs
- Rhabditiform Larvae
★ Eggs
○ May be present in stool with patients that have severe diarrhea.
○ Can be successfully recovered using the method stool concentration with zinc sulfate
★ Rhabditiform Larvae
○ May be recovered in
- fresh stool samples
- duodenal aspirates
what are the other laboratory diagnosis for S. stercoralis
★ Enterotest
successful in obtaining the desired larvae and hookworm-like eggs.
★ Serologic Tests
such as ELISA have been developed for detection of the parasite
(Enzyme-Linked Immunosorbent Assay)
*Sputum - can also yield S. stercoralis larvae
What sample, besides stool, can contain S. stercoralis larvae?
sputum
In what type of specimen are threadworm larvae more frequently recovered?
Concentrated specimens, rather than those processed with the flotation technique.
briefly explain the clinical symptoms in S. stercoralis
asymptomatic
- patient suffering from light infection
Strongyloidiasis: Threadworm
Infection
- most common symptoms:
diarrhea
abdominal pain
- urticaria (hives) with eosinophilia
- gastrointestinal symptoms may occur in strongyloidiasis:
Vomiting
Constipation
Weight loss
Variable anemia
Malabsorption (in heavy infections)
What happens at the site of larval penetration in in S. stercoralis?
bcm itchy and red
What happens when S. stercoralis larvae migrate to the lungs?
experience pulmonary symptoms.
What is the risk of autoinfection in immunocompromised patients? (S. stercoralis)
Spread of larvae throughout the body
Increased secondary bacterial infections
Possible death
life cycle of S. stercoralis
★ Direct
1. Rhabditiform larvae passed in the feces.
2. These rhabditiform larvae develop into third-stage infective filariform larvae in warm, moist soil.
3. Remaining phases of the life cycle
basically mimic those of hookworm.
★ Indirect
1. Threadworm rhabditiform larvae passed into the outside environment and mature into free-living adults that are nonparasitic.
2. These adult females produce eggs that develop into rhabditiform larvae.
3. These larvae mature and transform into filariform stages.
- initiate a new indirect cycle
- become the infective stage for a human host and begin a direct cycle.
★ Autoinfection
1. Rhabditiform larvae develop into the filariform stage inside the intestine of the human host.
- direct cycle first
2. Resulting infective larvae may then enter the lymphatic system or bloodstream.
3. Then initiate a new cycle of infection.
epidemiology of S. stercoralis
tropical and subtropical regions of the worlds
area of poor sanitation, in which feces are disposed in the warm moist soil
persons living institutions w in poor sanitation practices
★ At risk are those who come into skin contact with contaminated soil.
treatment for S. stercoralis
Ivermectin
Albendazole – alternative drug
prevention and control for S. stercoralis
Similar to those for hookworm
Proper handling and disposal of fecal material
Adequate protection of the skin from contaminated soil
Prompt and thorough treatment of infected persons
Trichinella spiralis
★ Common name:
★ Common associated disease
★ Common name: Trichina Worm
★ Common associated disease:
○ Trichinosis
○ Trichinellosis
where does the encysted larvae of Trichinella spiralis settle
by coiling up in muscle fiber and becoming encysted.
Striated muscle cell that surrounds the coiled larva
nurse cell
What does a biopsy of infected muscle tissue reveal in Trichinella spiralis
Inflammatory infiltrate caused by the immune system’s response to the larvae.
The immune system attacks the encysted larvae, leading to a buildup of white blood cells (inflammatory infiltrate).
what plays a vital role in diagnosing T. spiralis infection
clinical symptoms
patient history
what is the method of choice for the recovery of encysted larvae of T. spiralis
Examination of the Affected Skeletal Muscle
What laboratory findings can indicate a Trichinella spiralis infection?
Eosinophilia (elevated eosinophil count)
Leukocytosis (elevated white blood cell count)
What serum muscle enzyme levels may be elevated in a Trichinella spiralis infection?
Lactate dehydrogenase (LDH)
Aldolase
Creatine phosphokinase (CPK)
Why can some tests give false-negative results in early Trichinella spiralis infections?
The timing of sample collection may affect the detection of larvae and other indicators.
this spp is known as the great imitator
T. spiralis
- patients experience a variety of symptoms that often mimic other diseases or conditions = symptomatic
in Trichinella spiralis, what symptoms are associated with
- light infections
- intestinal phase of heavy infection
- larvae migrate through the body
- larvae settle in striated muscle
- light infections
Diarrhea
Slight fever (suggestive of flu) - intestinal phase of heavy infection
Vomiting
Nausea
Abdominal pain
Diarrhea
Headache
Fever - larvae migrate through the body
Eosinophilia (elevated eosinophils)
Pain in the pleural area
Fever
Blurred vision
Edema
Cough
Death (in severe cases) - larvae settle in striated muscle
Muscular discomfort
Edema (swelling)
Local inflammation
Fatigue
Weakness
Affects the face, limbs, and other parts of the body.
life cycle of Trichinella spiralis
- Infection initiated after consuming undercooked contaminated meat, primarily striated muscle.
- Human digestion of the meat releases T. spiralis larvae into the intestine.
- Larvae mature into adult worms rapidly.
- Mating occurs and the gravid adult female migrates to the intestinal submucosa to lay her live larvae.
- Infant larvae enter the bloodstream and travel to striated muscle, where they traveling encyst nurture cells.
- Granuloma forms over time which becomes calcified around these cells.
- Humans are not the traditional hosts, completion of T. spiralis life cycle does not occur and the cycle ceases with the encystation of the larvae.
What type of infection does Trichinella spiralis cause in humans?
Zoonotic infection
- parasite whose normal host is an animal, causing accidental infection in humans.
epidemiology of Trichinella spiralis
worldwide but rarely in tropical areas
in developed areas, feeding of contaminated pork scraps to hogs accounts for major mode of transmission
in what diff type of animals can Trichinella spiralis be found
pig
deer
bear
walrus
rat
- this suggest that it is resistant to colder regions
treatment of Trichinella spiralis
- no medication as it is non-life threatening strain of disease
- pletny rest
- adequate fluid intake
- fever reducers
- pain relievers
★ Prednisone for severe infection
Dracunculus medinensis
★ Common name:
★ Common associated disease:
★ Common name: Guinea Worm
★ Common associated disease:
○ Dracunculosis
○ Dracunculiasis
○ Guinea worm infection
where does the third-stage larvae of Dracunculus medinensis reside
in the intermediate host
this is one of the largest adult nematodes
Dracunculus medinensis (adult worm)
laboratory diagnosis of Dracunculus medinensis
★ Recovered by observing infected ulcers for the emergence of the worms.
★ Induced rupture of the infected ulcers by immersing in cool water reveals the first-stage larvae
clinical symptoms of Dracunculus medinensis
- allergic reactions related to the migration of the organism
- secondary bacterial infections = disability or death
- ulcer at the site
- allergic reactions and nodule formation
What happens at the site where the gravid female Guinea worm settles?
ulcer forms as the gravid female settles into the subcutaneous tissues and lays her larvae.
What happens when an adult Guinea worm dies?
Allergic reactions
Nodule formation
Calcification of the dead worm
life cycle of Dracunculus medinensis
- Infection is initiated upon ingestion of drinking water contaminated with infected copepods (freshwater fleas).
- Copepods containing infective D. medinensis third-stage larvae will emerge into the intestine.
- Larvae mature into adult worms which will penetrate the intestinal wall, and proceed to connective tissues or body cavities.
- Following mating, gravid female adult worms migrate into the subcutaneous tissues, especially in the skin of extremities, where they lay live first-stage larvae.
- On release of the larvae, the adult females may escape from the body at the larvae deposit site or migrate back into deeper tissues.
- Infected ulcer results at the site of larvae deposit.
- Ulcer ruptures and releases the larvae into the water.
- Copepods living in the water consume the first-stage larvae, serving as its intermediate host.
- Maturation into their third-stage infective form occurs.
- Ingestion of the infected copepod begins the cycle again
epidemiology of Dracunculus medinensis
parts of
- Africa
- India
- Asia
- Pakistan
- the Middle East
reside in freshwater, particularly in areas called step walls
- ppl obtain drinking water and bathe
ponds, human-made water holes, and standing water may also serve as sources of infection.
reservoir hosts include dogs which can be infected via contaminated drinking water
where do the Dracunculus medinensis reside
reside in freshwater, particularly in areas called step walls
- ppl obtain drinking water and bathe
prevention and control of Dracunculus medinensis
★ Use of properly treated water for consumption
★ Boiling water for suspected contamination.
★ Prohibiting practice of drinking and bathing in the same water.
★ Ceasing the practice of allowing standing water to be ingested.
★ Copepods may be removed from suspected water by using a finely meshed filter.
treatment of Dracunculus medinensis
- Placing the aected body part, in the form of a blister, in cool water.
- contact with water creates an environment of interest to the underlying adult worm. - The adult worm breaks through the blister and is eager to explore the outside world.
- It is important at this juncture to clean the resulting wound thoroughly.
- Manual extraction of the entire worm by winding it around a stick or a similar item that creates tension.
- Once the worm is removed, apply topical antibiotics to the wound site as a protective measure against the emergence of secondary bacterial infections.
