Filarial Nematodes

Filarial Nematodes - Chapter 29

3 differences from other groups of nematodes:

1. Tissue-dwelling nematodes (not in digestive tract)

2. Possess a unique life cycle stage – the _____________________________- between the egg and L1

• Egg ____________ L1 L2 L3 L4 Adult

• these are present in the bloodstream or skin of the definitive host.

3. Filarial worms utilize ________________________________

__________________________________________

Wuchereria bancrofti

Causative agent of Bancroftian filariasis or ____________________________________

Disease has described by ancient Greek and Roman writers who likened the skin of infected persons to that of an elephant.

Microfilariae and adults were described in 1870's.

____________________________________ discovered that mosquitoes were vectors of this disease in 1878.

Distribution of Wuchereria bancrofti

Parasite is widespread throughout ______________________________

Was present in __________________________________ - last infections were recorded in South Carolina in 1920's - brought to U.S. with slave trade

High prevalence in ______________________________- concern to American GIs in WWII - used in Japanese propaganda. Over 10,000 infections were reported in servicemen but none developed the classical symptoms of elephantiasis

Life Cycle of Wuchereria bancrofti

1. Adults live in a coiled mass in _________________________ ___________________________of humans - generally in the lower parts of the body.

- male worms are 1½ inches long

- females are 2-4 inches long


2. Females produce thousands of ___________________________that are released into the lymph and move into peripheral blood __________________________

Why?

http://www.answers.com/main/Record2?a=NR&url=http%3A%2F%2Fcommons.wikimedia.org%2Fwiki%2FImage%3AWuchereria%2520bancrofti%25201%2520DPDX.JPG


3. Microfilariae are ingested when night-biting ___________________________takes blood meal.

4. Microfilariae migrate to the mosquito muscles and molt to___________________


5. L3 migrate to the mouth parts of the mosquito and enter human skin when the mosquito bites.

L3 is infective stage to human.

6. L3 enter small lymphatic vessels and move to the large lymphatic vessels

- molt 2x to become adults

- adults take up to a year to mature and produce microfilariae

Adults of Wuchereria bancrofti

Adults occur in the lymphatic vessels

Microfilariae of Wuchereria bancrofti

Microfilariae are seen in blood smears and are DIAGNOSTIC

• worms are 230-320 µm long

• contain a __________________________ that can be seen at one end – diagnostic character

Microfilariae of Wuchereria bancrofti

Nocturnal periodicity of microfilariae

Pathology of Wuchereria bancrofti

Pathology caused by _________________________________

__________________________________________________

3 clinical phases

1. __________________________________ - time between infection with L3 after a mosquito bite and maturation of adults (usually a year) - no symptoms


2. __________________________ - females release microfilariae

- infiltration of white blood cells

- intense inflammation of lymphatic vessels and lymph nodes shown by _________________________


3. _______________________________

- occurs in persons repeatedly infected with the worms - generally older persons living for years in endemic areas

- large numbers of adults block lymphatic vessels

- lymph is lost in the urine

- lymph accumulates in the scrotum called ______________________________


Nice family picture of hydrocele of the scrotum


Inflammation in right leg; obstruction in left leg

3. Obstructive phase cont: -

- progressive infiltration of obstructed area with _____________________________ leads to enlargement of legs, scrotum, &/or arms (elephantiasis)


Obstructive phase photos

Treatment of Wuchereria bancroftiDrugs _________________________________________________________ are somewhat effective

• kill microfilariae and adults with careful administration Pressure bandages on enlarged limbs forces lymph out.

Surgery can be used to remove elephantoid tissue if muscle involvement is minimal.

Prevention of Wuchereria bancrofti1. ___________________________________________________ 2. Protection from _________________________________________________________________________________________ 3. ______________________________of infected persons to eliminate

____________________________ so they are not available to biting mosquitoes

http://www.cartercenter.org/news/multimedia/HealthPrograms/AlleviatingSufferingEndingShame.html

Dirofilaria immitis

Causative agent of___________________________________________

DISTRIBUTION - Cosmopolitan distribution; found throughout much of the U.S.

- in the Midwest (Wisconsin, Minnesota, Iowa) 1 to 2% prevalence

- 1.6 % in Eau Claire - see study by Wittrock and Palmer

- high prevalence in southern U.S. - 10 to 70% prevalence

Life Cycle of Dirofilaria immitis

1. Adults live in the ______________________________________________

2. Females release _______________________ into the bloodstream

3. Microfilariae are ingested when ____________________ bites an infected dog.

Aedes mosquitoes are commonly called _______________________ and are associated with woody habitats.

And where do most dog owners build their kennels?

Life Cycle of Dirofilaria immitis

4. Larvae develop to the ________stage in the mosquito and migrate to mouthparts.

L3 is infective stage and is

inoculated into dog skin with mosquito bite.

5. Larvae wander in _________________________of dog for about 2 months before entering circulation.

Reach heart and molt 2x to adult stage.

Stages of Dirofilaria immitis

Unsheathed microfilaria in dog blood - DIAGNOSTIC

Adult male: 6-12 inches long

Adult female: 12-16 inches long

Adults coiled in right side of dog heart

Pathology of Dirofilaria immitis

PATHOLOGY caused by __________________________

1. First signs of infection involve __________________________

• due to inadequate blood supply to lungs

• infected dogs cough, have shortness of breath, and tire rapidly.

2. Eventually the dog suffers __________________________- usually after a period of exercise.

Dirofilaria immitis

PREVENTION - chemoprophylaxis

2 drugs are used: ivermectin (in Heartgard) and milbemycin oxime (in Sentinel and Interceptor)

- How taken? ___________________________________________

- How does it work? _____________________________________

- How long to treat? _____________________________________

Human Cases of Dirofilaria immitis

HUMAN INFECTIONS of Dirofilaria immitis are rare (~100 cases).

Most cases are ___________________________________

Cases involve ______________________________________

• Larvae are killed by the host reaction and scar tissue nodules form in lungs around worms

• Symptoms are coughing and chest pain.

Onchocerca volvulus

Causative agent of onchocerciasis or _____________________________________

DISTRIBUTION - _________________________________

________________________________________________

Life Cycle of Onchocerca volvulus

1. Adults live in coiled masses in _______________________________________________________________


- Nodules are most common in the _____________________ region in Africa

- Nodules are on the ____________________in Central & South America.


2. Females produce __________________________________________

- Microfilariae of Onchocerca NEVER invade the bloodstream.


3. Microfilariae in the skin are ingested by the _____________________ - Simulium damnosum - when a blood meal is taken.


4. Parasites develop to ____________ in the musculature of the blackfly and migrate to the mouthparts.

5. ___________________ are inoculated into the skin when blackfly bites.

Adults mature in a year within subcutaneous nodules.

Adults of Onchocerca volvulus

Skin nodule cut open to reveal adults coiled together

Microscopic section showing adults and scar tissue reaction around them forming the nodule

Microfilariae of Onchocerca volvulus

Unsheathed microfilariae occur in the skin, never the bloodsteam

Pathology of Onchocerca volvulus

ADULTS cause ___________________________________________________________________

Nodules are about ½ -1 inch in diameter.

Nodules are relatively benign and cause only some disfigurement.


MICROFILARIAE cause 3 severe problems. This is the only filarial worm in which microfilariae are pathogenic!

1. Microfilariae in the skin cause severe ______________________

- skin becomes ________________________________________ -___________________________ occurs leading to secondary bacterial infections - itching is so severe some people

have committed suicide


1. Microfilariae in skin cont:

- in parts of Africa, the skin of the scrotum and inguinal area loses its elasticity causing ______________________________________


2. Microfilariae invade the eye - ________________________________________________________ occur as microfilariae die in the eye - fibrosis causes clouding of cornea and aqueous and vitreous humors resulting in blindness - fibrosis of the eye is a slow development and most affected persons are _____________________________


2. Microfilariae invade the eye cont:

In many parts of Africa, the sighted young are responsible for leading the older blind adults.


3. Microfilariae invading the ___________________________________cause deficiency of growth hormone resulting in ____________________________________

- seen in parts of Africa

So it’s a terrible parasite – it doesn’t kill you but:

_________________________________________

_________________________________________

_________________________________________

Diagnosis of Onchocerca volvulus

(1) ________________________________________________

___________________________________________________

- snip must be bloodless so as to not to confuse with microfilariae that may be circulating in the bloodstream.

(2) ________________________________ in excised skin nodule

Onchocerca volvulus

TREATMENT

1. Surgical remove of nodules (denodulization)

2. Drug treatment with Suramin (kills adults) and Ivermectin (Mectizan®) (kills _______________________)

Mectizan® is free from Merck and only needs to be taken once per year

3. Recent finding of tetracycline – antibiotic kills the bacteria living in adult worms and adults died

http://www.cartercenter.org/news/multimedia/HealthPrograms/PreservingVisionforFutureGenerations.html

http://www.cartercenter.org/news/multimedia/HealthPrograms/MectizanBringsHopetoMillions.html



Onchocerca volvulus

PREVENTION –

1.

- Larval blackflies live in fast moving rivers

- After development in water, adults emerge and are bloodfeeders

2.

Brugia malayi

Causes _____________________________________ Distribution - Orient, South Pacific, and Southern Asia to India – overlaps with Wuchereria bancrofti - but does not occur in Africa or South America

Brugia malayi

Morphology and life cycle is similar to that of Wuchereria bancrofti

Brugia malayi

Pathology - Adults live in lymphatic vessels of the arms and legs and cause elephantiasis in these regions Difference from Wuchereria?

Loa loa

____________________________________ - name is actually incorrect as adults spend most of life under skin but occasionally migrate through the eye

Distributed in the ___________________________________

Life Cycle of Loa loa

1. Adults occur in the ________________________________________ - produce bumps called ____________________

Migrate extensively and occasionally wander into the conjunctiva and cornea of the eye.

Life Cycle of Loa loa

2. Females release ____________________which enter the bloodstream during the day (diurnal periodicity) and are available to the vector ____________________

3. L3 develop in the deerfly and are inoculated into skin when deerfly bites.

microfilariae

Pathology of Loa loa

Adults cause localized inflammatory reactions in the skin called Calabar swellings.

Eye swells when worms migrate through.

Loa loa is rather benign compared to other filarial worms.

Guinea Worms – Chapter 30

Dracunculus medinensis Human guinea worm - causative agent of dracunculiasis

DISTRIBUTION - now only in parts of Africa Number of cases has dropped drastically: 1986 – 3.5 million 2002 – 54,000

2007 – 9,5702008 – 4,219 thus far

Dracunculus medinensis

MORPHOLOGY- Adults occur ______________________________________________________________although all parts of the body are susceptible.

Adult females are largest nematodes of humans – reach length of up to 4 feet.

Male is smaller - 4 cm.

HOSTS - humans and many other mammals (dogs, cats, cattle, horses, monkeys)

- disease is a ____________________

Life Cycle of Dracunculus medinensis

1. Adults occur in the subcutaneous connective tissues.

2. Female migrates to surface of the skin and produces a _______________________ through which the anterior of worm protrudes.


3. Uterus of female worm ruptures when worm in immersed in water.

Thousands of ____________ ________________________(eggs hatch inside female).


4. L1 must be ingested by _______________________ intermediate host.

Larvae molt to infective L3

stage within copepod.


5. Humans (and other mammals) become infected by__________________________________________________

6. L3 penetrate small intestine and migrate to subcutaneous tissues

- they molt twice to become adults.

- female is mature in about a year.

Human Cases of Dracunculus medinensis

In endemic areas humans are constantly re-exposed and re-infected with this parasite

High prevalence in _______________________

- high concentration of persons around water

- warm, stagnant water is excellent habitat for ________________________

Human Cases of Dracunculus medinensis

_____________________ are common sites of infection.

- Infected water bearers enter water allowing female worms to release larvae

- They then fill water jars with drinking water containing infected copepods.

Pathology of Dracunculus medinensis

1. Symptoms of dracunculiasis occur as worms migrate under the skin

- female releases metabolic wastes that cause toxemia that causes a rash, nausea, diarrhea, and dizziness

Pathology of Dracunculus medinensis

2. Blister formation results in a large inflamed sore

- blister ruptures when ______________________________

- secondary bacterial infections can occur through ruptured blister

2. Blister formation results in a large inflamed sore

- blister ruptures when ______________________________

- secondary bacterial infections can occur through ruptured blister

3. Some worms may migrate into deeper tissues such as the joints where they calcify causing ________________________

Dracunculus medinensis

DIAGNOSIS - appearance of red blister followed by

emergence of the female worm

Treatment of Dracunculus medinensis

TREATMENT -

______________________________________ is best known treatment

• must be done slowly as to not break worm

• Why?

PREVENTION:

http://www.yamagiku.co.jp/pathology/photo/photo195-4.htm

Since 1986, when an estimated 3.5 million people were infected, a campaign run by the ______________________________ UNICEF, WHO and the CDC has largely eliminated the disease, but it still occurs in 5 countries, all in Africa.

But this may be second disease (after smallpox) to be totally eradicated from the world.

http://www.cartercenter.org/news/multimedia/HealthPrograms/TamingtheFierySerpent.html

Former president Jimmy Carter has been actively involved in the elimination of Guinea worm, lymphatic

filariasis, and river blindness

"Hopefully Guinea worm will be the first parasitic disease ever eradicated. If and when that happens, we will have done it without a drug and without a vaccine to treat or prevent the disease. If we can do that, it will be one of the greatest achievements in public health."

—Dr. Ernesto Ruiz-Tiben, director, Guinea Worm Eradication Program

What is this symbol?

What are these?

Medicine’s logo mark is based on Asclepius, a god of medicine, and snake around the stickDracunculiasis was endemic along the Red Sea in the era of the Old Testament. Guinea worm was called "fiery snake". Actually, the snake around the Asclepius' stick is the Guinea worm! It can be supposed that in the Greek era, Asclepius was especially good at removing the fiery snake by using a stick.

Dracunculus insignis

Dracunculus insignis occurs in the ___________________________________________of wild mammals (canids, mink, raccoons, badgers, etc.) in the U.S. including Wisconsin.

A few human cases of this species have been reported but the parasite is apparently nonpathogenic.

See specimen on demo in lab

Filarial Nematodes

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