Nematoda 3 II

Is hookworm prevalence and intensity higher among adult females or males? Why?

In adult males because hookworm infection tends to be occupational

Do the skin-invasive larvae of N.americanes and A. duodenale all immediately pass through the lungs and into the gut?

No as they are spread around the body via the circulation to become dormant inside muscle fibres

What happens in terms of N.americanes and A. duodenale in a pregnant women after childbirth?

Some or all of the larvae are stimulated to reenter the circulation because of sudden hormonal changes. Then they are passed into the mammary glands so that the newborn baby can receive a large dose of infective larvae through its mothers milk

Can there be heavy and fatal hookworm infections in children a month or so of age? If yes, where?

Yes there can be in China, India, and Northern Australia 

Are male or female hookworms smaller?

Male hookworms

Describe what the anterior end of N. americanes has

It is armed with a pair of curved cutting plates where A. duodenale is equipped with one or more pairs of teeth

What is the life cycle of hookworms identical to? What is a difference between them?

Identical to that of threadworms. But hookworms are unable to carry out a free living or auto-infectious cycle. In addition, A. duodenale can infect by the oral route

What do symptoms of hookworm infection depend on? Does light infection of hookworms often go unnoticed?

The site at which the worm is present and the burden of worms. Yes 

How do you diagnose hookworms? Can species of hookworms be distinguished by egg morphology?

Through identification of eggs in fresh or preserved feces. No

How do we treat hookworms?

Through mebendazole (200mg) for adults and (100mg) for children for 3 days

How do we control disease caused by hookworms?

Sanitary disposal of fecal material and avoidance of contact with infected fecal material

What is the common name for Dracunculus medinensis? Is male or female smaller?

Guinea worm or fiery serpent of the Israelites. Male is half the size of the female 

Describe the life cycle of Dracunculus medinensis

1. Human drinks unfiltered water containing copepods with L3 larvae

2. Larvae are released when copepods die. Larvae penetrate the hosts stomach and intestinal wall. They mature in 10-12 weeks and reproduce here

3. Fertilized female worm migrates to surface of skin, causes a blister, and discharges larvae 

4. L1 larvae released into water from the emerging female worm (emerges one year after infection) (D)

5. L1 larvae consumed by a copepod 

6. Larvae undergoes two molts in the copepod and becomes a L3 larvae in 2-3 weeks (I)

What happens if the Dracunculus medinensis does not reach the skin? What does D. medinensis do in superficial tissue?

It will die and cause little reaction. It liberates a toxic substance that produces a local inflammatory reaction in the form of a sterile blister with serous exudation 

What does D. medinensis lie in?

The worm lies in a subcutaneous tunnel with its posterior end beneath the blister which contains a clear yellow fluid

What is the course of this tunnel marked with? What does contamination of the blister produce?

Marked with induration and edema. Produces abscesses, cellulitis, extensive ulceration and necrosis

How do we diagnose D. medinensis?

Made from the local blister, worm, or larvae. The outline of the worm under the skin can be revealed by reflected light

How do we treat D. medinensis?

Have to extract the adult worm by rolling it a few cm per day or preferably by multiple surgical incisions. Metronidazole is also effective in killing the worm 

What are preventative measures against D. medinensis?

Protection of drinking water from being contaminated with Cyclops and larvae

Why is the best treatment to pull the worm out? Where is D. medinensis mainly found in the body? Why?

This is because if you damage the worm through surgical incisions then it can cause more blisters. In the legs and feet because they have contact with water

What are the major blood and tissue parasites of humans? What does this include?

Microfilaria which include:

1. Wuchereria bancrofti

2. W. (Brugia) malayi

3. Onchocerca volvulus

4. Loa loa (eye worm)

What is elephantiasis caused by? What is the vector?

Wuchereria bancrofti and W. (Brugia) malayi. Mosquitos are the vectors for both parasites

Is W. bancrofti strictly a human pathogen? Where is it distributed?

Yes it is and distributed in tropical areas worldwide

What does B. malayi infect? Where is it distributed?

It infects a number of wild and domestic animals and is restricted to South-east Asia

Are B.malayi and W. bancrofti similar in morphology and diseases they cause? Where is the adult female for W. bancrofti found? 

Yes they are and it is found in lymph nodes and lymphatic channels 

What are microfilaria and where are they found?

They are juveniles and are found in blood

What is the size difference between B. malayi and W. bancrofti?

Adult B. malayi are half the size of W. bancrofti but their microfilaria are only slightly smaller than W. bancrofti

What is the typical vector for B. malayi filariasis?

Mosquito species from the genera Mansonia and Aedes

What does the microfilaria of W. bancrofti do?

It will penetrate the midgut of the vector and migrate to the musculature where they develop to infectious L3 (filariform larva). L3 larvae will migrate to the flys mouthparts and infect a new host when the vector takes a blood meal

Describe the life cycle for lymphatic filariasis

1. Mosquito will take a blood meal and L3 larvae enter the skin and migrate to various tissues (I)

2. They will mature for a year to become adults

3. Adults will produce sheathed microfilaria that migrate to lymphatics and at night enter the blood circulation (D)

4. Mosquito will take a blood meal and ingest microfilaria 

5. Microfilaria shed sheaths and penetrate mosquitos midgut and migrate to thoracic muscles 

6. L1 larvae 

7. L3 larvae 

8. Migrate to head and mosquitos proboscis 

What are the symptoms of lymphatic filariasis?

Lymphadenitis (infection of your lymph node) and recurrent fever every 8-10 weeks that lasts 3-7 days. Lymphedema (tissue swelling), elephantiasis, eosinophilia (too many eosinophils) and some splenomegaly.

What is progressive lymphadenitis due to?

An inflammatory response to the parasite lodged in the lymphatic channels and tissues

What is lymphedema and elephantiasis caused by?

As the worm dies, the reaction continues and produces a fibre-proliferative granuloma which obstructs lymph channels

What is stretched skin susceptible to? What causes eosinophilia and some splenomegaly? 

Susceptible to traumatic injury and infections. Microfilaria 

Do all infections lead to elephantiasis? In the absence of elephantiasis, is the prognosis good?

No they do not and yes.

What is diagnosis based on for lymphatic filariasis?

1. History of mosquito bites in endemic areas

2. Clinical findings

3. Presence of microfilaria in blood samples collected at night (have to take it from capillaries not veins)

What are two types of treatment for lymphatic filariasis?

Diethylcarbamazine quickly kills the adult worms or sterilizes the females. It is given orally for 14 days. Steroids also will help alleviate inflammatory symptoms

What can reduce inflammatory reaction of lymphatic filariasis?

Cooler climate

Why are appendages getting swollen? Is the skin getting hard?

This is because blood vessels and lymphatic nodes are being blocked. Yes