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
Life Cycle of Wuchereria bancrofti 2. Females produce thousands of ___________________________that are released into the lymph and move into peripheral blood __________________________ Why?
Life Cycle of Wuchereria bancrofti 3. Microfilariae are ingested when night-biting ___________________________takes blood meal. 4. Microfilariae migrate to the mosquito muscles and molt to___________________
Life Cycle of Wuchereria bancrofti 5. L 3 migrate to the mouth parts of the mosquito and enter human skin when the mosquito bites. L 3 is infective stage to human. 6. L 3 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 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 L 3 after a mosquito bite and maturation of adults (usually a year) - no symptoms
Pathology of Wuchereria bancrofti 2. __________________________ - females release microfilariae - infiltration of white blood cells - intense inflammation of lymphatic vessels and lymph nodes shown by _________________________
Pathology of Wuchereria bancrofti 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 ______________________________
Pathology of Wuchereria bancrofti Nice family picture of hydrocele of the scrotum
Pathology of Wuchereria bancrofti 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)
Pathology of Wuchereria bancrofti Obstructive phase photos
Pathology of Wuchereria bancrofti Obstructive phase photos
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. L 3 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
Nodules are most common in the _____________________ region in Africa
Nodules are on the ____________________in Central & South America.
Life Cycle of Onchocerca volvulus 2. Females produce __________________________________________ - Microfilariae of Onchocerca NEVER invade the bloodstream.
Life Cycle of Onchocerca volvulus 3. Microfilariae in the skin are ingested by the _____________________ - Simulium damnosum - when a blood meal is taken.
Life Cycle of Onchocerca volvulus 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
Pathology of Onchocerca volvulus 1. Microfilariae in skin cont: - in parts of Africa, the skin of the scrotum and inguinal area loses its elasticity causing ______________________________________
Pathology of Onchocerca volvulus 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 _____________________________
Pathology of Onchocerca volvulus 2. Microfilariae invade the eye cont: In many parts of Africa, the sighted young are responsible for leading the older blind adults.
Pathology of Onchocerca volvulus 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: _________________________________________ _________________________________________ _________________________________________
After development in water, adults emerge and are bloodfeeders
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. L 3 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 – 9,570 2008 – 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.
Life Cycle of Dracunculus medinensis 3. Uterus of female worm ruptures when worm in immersed in water. Thousands of ____________ ________________________(eggs hatch inside female).
Life Cycle of Dracunculus medinensis 4. L 1 must be ingested by _______________________ intermediate host . Larvae molt to infective L 3 stage within copepod.
5. Humans (and other mammals) become infected by__________________________________________________
6. L 3 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 ________________________
_____________________ 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
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
Medicine’s logo mark is based on Asclepius, a god of medicine, and snake around the stick Dracunculiasis 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