NEMATODE INFECTIONS

giant round worm

Ascaris lumbricoides other term

tropics

Ascaris lumbricoides occur most frequently in the ?

soil-transmitted helminth (STH)

Ascaris is a ___________ , along with Trichuris trichiura and hookworms, which means that the soil plays a major role in the development and transmission of the parasite

* tissue reaction to the invading larvae,
* intestinal irritation to the adult,
* other complications due to heavy infection and extraintestinal migration

STH causes varying degrees of pathology

Soil transmitted helminth infections

These diseases are diseases of poverty, and contribute to malnutrition and impairment of cognitive performances

Polymyarian type

type of somatic muscle arrangement of Ascaris lumbricoides

whitish or pinkish

ascaris worm color

True

T/F: female AL worms are much larger than male AL worms

terminal; three; sensory papillae

AL worms have a _____ __mouth with__ ___ __lips and__ _____ ______

curved; two

Males have a ventrally _____ __posterior end with _____ spicules

paired

Female AL have ______ reproductive organs in the posterior two-thirds

small intestines

The AL adults reside in but do not attach to the mucosa of the ____ ________

pepsin inhibitor 3 (PI-3)

Ascaris has been shown to produce ____ ______ that protects worms from digestion and phosphorylcholine that suppresses lymphocyte proliferation.

Infertile eggs of Ascaris lumbricoides

longer and narrower than fertile eggs, with a thin shell and irregular mammilated coating filled with refractile granules

Fertile eggs of Ascaris lumbricoides

outer, coarsely mammilated albuminous covering which may be absent or lost in “decorticated” eggs. The egg has a thick, transparent, hyaline shell with a thick outer layer as a supporting structure and a delicate vitelline, lipoidal, inner membrane, which is highly impermeable.

embryonated egg

infective stage of AL

14

hepato-tracheal migration phase takes about __ days

9 to 11

the development of egg-laying adult worms takes about *_ to* __ weeks after egg ingestion.

1 year

The life span of an adult worm is about

200,000

A female Ascaris produces about ______ eggs per day

2 to 3

In the soil, it takes about *_ to* _weeks for eggs to develop into the infective stage (embryonation) under favorable conditions with suitable temperature, moisture, and humidity

two

The larvae undergo ___ molts to reach their 3rd stage within the egg and become embryonated

True

T/F: A majority of Ascaris infections are asymptomatic

False

T/F: A majority of Ascaris infections are symptomatic

1\.85 million

Ascariasis was estimated to have contributed to a total of ___ million disability-adjusted life years (DALYs) in 2004.

* The varied pathology of ascariasis includes
* irritation of the intestine by the mechanical and toxic action
* parasite’s extraintestinal migration

The varied pathology of ascariasis includes

* lung infiltration
* asthmatic attacks
* edema of the lips

During lung migration, the larvae may cause host sensitization resulting in allergic manifestations such as

Eosinophilia

This is present during larval migration

biliary ascariasis

Patients with ____ ______experience severe colicky abdominal pain, which is brought about by the movement of the worms inside the biliary tract.

lactose intolerance

moderate infection in preschool children may cause

Bowel obstruction

Heavy infections of ascariasis may cause

acute appendicitis

worms lodge in the appendix may cause

pancreatitis

worms occlude pancreatic ducts may cause

caused by intestinal bacteria carried to migration sites

Abscesses

Peritonitis

penetration of worm into the peritoneal cavity

* direct fecal smear (DFS)
* Kato thick Smear
* Kato-Katz techniques
* concentration techniques (formalin-ether/ethyl acetate concentration technique (FECT)

stool examination techniques used to diagnose ascariasis by confirming the presence of eggs in the feces

Direct Fecal Smear

* less sensitive compared to the Kato thick Smear and Kato-Katz techniques.
* Used for detection of parasitic motility

Kato technique or Cellophane thick smear method

* Fecal sample used is 20 to 60 mg
* Purely qualitative method and recommended for mass examination of feces for diagnosis of Ascaris lumbricoides

Kato-Katz technique

provides quantitative diagnosis in terms of the intensity of helminth infection in eggs per gram (epg) of stool that is useful in monitoring the efficacy of treatment in clinical trials, as well as public health programs

Albendazole

Drug of choice for Ascaris

* given at 400 mg single dose (200 mg for children 12-23 months)

albendazole, mebendazole, and pyrantel pamoate

Antihelmenthic drugs

Mebendazole

given at 500 mg single dose

pyrantel pamoate

given at 10 mg/kg (max. 1 g) also as a single oral dose

Ivermectin

shown to be as effective as albendazole if given at a dose of 200 μg/kg single dose

Benzimidazoles

these drugs, such as albendazole and mebendazole, bind to the parasites’ b-tubulin resulting in the disruption of parasite microtubule polymerization thus killing the parasite

four months post-treatment

When does reinfection usually occur?

six or seven months post treatment

WHen does full reinfection occurs?

Water sanitation; hygiene; education ; Deworming

WASHED stands for

1. sanitary disposal of human feces
2. health education
3. mass chemotherapy/mass treatment

Prevention and control measures for ascaris involves

Necator americanus Ancylostoma duodenale

* these hookworms infect humans
* blood-sucking nematodes

Necator americanus

New world hookworm

Ancylostoma duodenale

Old World Worm

meromyarian

Type of somatic muscles that all hookworms have

N. americanus adults

small, cylindrical, fusiform, grayish-white nematodes

True

T/F: Female N. americanus are larger than males

False

T/F: Male N. americanus are larger than Female

caudal bursa

The posterior end of the male N. americanus has a broad, membranous ___ ____with rib-like rays, which are used for copulation

opposite

hookworms: The head is curved ________ to the curvature of the body, which is like a hook at the anterior end

A. duodenale; N. americanus

The adult ______ __is slightly larger than__ ______

same

the head of the A. duodenale adult continues in the _____ direction as the curvature of the body

single paired

how many reproductive organs does adult hookworms have

semilunar cutting plates

The buccal capsule of N. americanus has a ventral pair of ?

curved ventral teeth

The buccal capsule of Ancylostoma duodenale has two pairs of

True

T/F: Rhabditiform larvae of N. americanus and A. duodenale are indistinguishable

Strongyloides stercoralis

Rhabditiform larvae of N. americanus and A. duodenale resemble those of

larger, more attenuated posteriorly, and have a longer buccal cavity; smaller genital primordium than stercoralis

Difference of the rhabditiform larvae of N. americanus and A. duodenale to Strongyloides stercoralis

parallel

The buccal spears of the N. americanus filariform larva are conspicuous and ________ throughout their lengths

conspicuous

The transverse striations present on the sheath in the tail region of N. americanus are

inconspicuous

The transverse striations present on the sheath in the tail region of Ancylostoma duodenale are

bluntly rounded ends and a single thin transparent hyaline shell

eggs of hookworms

unsegmented

eggs of hookworms are ____________ at oviposition

Eggs in intestinal lumen→ human feces →soil → filariform larva in soil→ skin → venules → heart and lungs → alveoli → trachea → small intestine

hookworm life cycle

* the skin at the site of entry of the filariform larvae
* lung during larval migration
* small intestine, the habitat of the adult worms

The pathology of hookworm infection involves:

maculopapular lesions; erythema

Penetration of the filariform larvae through the skin produces ______ __and localized__ ______

ground itch; dew itch

Itching is often severe, and it is known as “?” or “?” as it is related to contact with soil, especially on a dewy morning

bronchitis and pneumonitis

If the larvae migrating through the lungs are abundant, ? may result

hemorrhages

In the course of migration, these larvae produce minute ? with eosinophilic and leukocytic infiltration

steatorrhea

abnormal amts of fats in feces

True

T/F: Hookworm infection is usually chronic, hence patients often show no acute symptoms.

Hypoalbuminemia

another manifestation of hookworm infection. There is low level of albumin due to combined loss of blood, lymph, and protein

humoral

Extensive _______ responses are produced against the larva and the adult hookworm, which share many antigens

eosinophils; mast cells; Th2 cells

Cellular immune response is primarily mediated by ? , ?, and ?

IgE

polyvalent ___ antibodies have been suggested to provide some protective roles

DFS; KATO THICK/KATO-KATZ METHOD; zinc sulfate centrifugal flotation/formalin-ether/ethyl acetate concentration; Harada Mori

Tests to diagnose hookworm

Direct fecal smear

Diagnostic tech: when the infection is quite heavy. It may not detect the parasite in light infections

Kato thick or Kato-Katz method

may increase detection rates since more stools are examined using these techniques.

Kato-Katz method

provide quantitative diagnosis by determining the intensity of infection in terms of number of helminth eggs per gram of fece

rapid clearance of eggs

disadvatage of Kato thick/Kato-katz

FLOTAC

centrifugal flotation method, has been shown to have a higher sensitivity for the diagnosis of soil-transmitted helminths compared with multiple examinations of KatoKatz smears

harada-Mori

Culture methods like the ? allow hatching of larvae from eggs on strips of filter paper with one end immersed in water

Culture method

method used for identification of helminth species

Albendazole

the drug of choice, is larvicidal and ovicidal against N. americanus and A. duodenale

Anemia and hypoproteinemia

What should also be addressed by giving iron supplementation and adequate diet.

Europe; Southwestern Asia

A. duodenale was prevalent in ? and ?

Africa ; Americas

N. americanus was prevalent in tropical ? and the ?

agricultural

The local distribution of human hookworm infection is greater in what areas

Farmers

They are prone to the infection because they work in rice fields and vegetable gardens

1. suitability of the environment for eggs and larvae
2. mode and extent of fecal pollution of the soil
3. mode and extent of contact between infected soil and skin or mouth

Factors that contribute to the distribution and transmission of hookworms are:

percutaneous

method of human infection in necatoriasis

percutaneous; oral route; transmammary transmission

method of human infection in ancylostomiasis