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86 Cards in this Set

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These roundworms release live larvae ("viviparous") instead of laying eggs
Trichinella, Dracunculus (guinea worm), Filarial infections (elephantiasis, river blindness, eye worm)
Transmission of this worm is from carnivore (or ominovore) to carnivore by eating skeletal muscle from the previous host
This infection features encysted larval progency in skeletal muscle
This worm is acquired by eating undercooked pork (or any other carnivore)
Route of invastion of Trichinella
Meat (animal muscle) with encysted larva is eaten, larva are released in small intestine, where they invade the mucosa and mature
Infective stage of Trichinella
Larva within meat
How long after infection by Trichinella does fertilization take place?
2 days
How long after infection by Trichinella are live larvae released?
5 days
How long does the Trichinella worm continue to release larvae?
1 month
How long do Trichinella larvae take to reach maximal size in the muscle?
3 weeks
Survival time of Trichinella larvae in smooth muscle
2 years (after which time they die and are calcified)
Diagnostic stage of Trichinella
Encysted larva in striated muscle
The diagnostic and infective stages of this worm are the same
Trichinella (encysted larva in striated muscle)
What happens to the Trichinella cyst over time?
It becomes calcified
Clinical signs and symptoms of Trichinella early on in heavy infection
Diarrhea, gastroenteritis
Cause of death in Trichinella
Migration of larvae to heart and brain
Clinical signs and symptoms of Trichinella later on in heavy infection
Eosinophilia, periorbital edema, diplopia, muscle pain, headache, fever, others (a wide array is possible)
Various serological tests support diagnosis of infection by this roundworm
Treatment of Trichinella
Steroids may be useful; bendazole is recommended but is not proven effective
Prevention of Trichinella
Cook meat, freeze meat (several days); at the population level, stop feeding uncooked pork scraps (via garbage) to pigs
T/F: In the US, it is illegal to throw out raw pork
True. Risk of worm transmission (eg, trichinella)
Geographic distribution of Trichinella
Worldwide, except Australia and some Pacific Islands
Genus of roundworm that causes Guinea Worm
Dracunulus (Guinea worm)
Transmission of Guinea worm
Copepods in drinking water containing infectious larvae
Intermediate host of Dracunulus (Guinea worm)
Copepod (tiny crustacean)
The female of this worm type grows to 1 m long
Dracunulus (Guinea worm)
Diagnostic stage of Dracunulus
Larva or adulte female escaping from skin in response to submersion of ulcer in cold fresh water
Infective stage of Dracunulus
Larva (third stage larva)
Dracunulus (guinea worm) prefers to migrate in subcutaneous tissue, especially in this part of the body
Life cycle of guinea worm (Dracunulus)
Infectious larvae are ingested then penetrate the intestinal wall and enter connective tissue or body cavities where the male and female mate. The female then migrates to superficial cutaneous tissue where she gives birth to live larvae which then escape through the skin
This worm gives birth by prolapse of the uterus in response to submersion in fresh water
Dracunulus (Guinea worm)
Definitive host of guinea worm (Dracunulus)
If this worm is broken during treatment, larvae are released systemically and severe inflammation can result (hypersensitivity reaction)
Dracunulus (Guinea worm)
Treatment of guinea worm (Dracunulus)
Slow extraction of worm over several weeks; surgery; bendazole
This disease remains a major problem in Sudan
Guinea worm (Dracunulus)
Clinical signs and symptoms of guinea worm (Dracunulus)
Painful lesion, frequently with secondary bacterial infection
Complications of guinea worm
Hypersensitivity reaction in response to systemic release of larvae when worm is broken
Prevention of guinea worm
Separate drinking water from bathing/washing/wading water supplies. Filter drinking water. Larvicide treatment of water.
WHO hopes to eradicate this disease in the near future
Guinea worm (Dracunulus)
Definitive host of filariases
Humans harbor both the adult worms and their newborn larvae of this class of roundworm
Life cycle of filarial roundworms
Insect bite -> injection of mature larvae -> maturation and mating of adult worms -> female releases live first-stage larvae (MICROFILARIAE) -> mirofiliariae circulate in blood or migrate to tissue
Intermediate host of filarial roundworms
Blood-sucking insects
Diagnostic stage of filarial roundworms
Microfiliariae in blood or tissue
Where do filarial roundworms mature?
Thoracic muscles of infected insect
This worm causes elaphantiasis
Wuchereria bancrofti
This disease is caused by adult worms in the lymphatics
Elephantiasis (caused by Wuchereria)
Intermediate host of Wuchereria
T/F: Wuchereria microfiliariae are pathogenic
False. The adult worm, not the microfiliariae cause disease
Microfiliariae are hard to detect in chronic forms of this disease because there are not many of them
Elephantiasis (caused by Wuchereria)
Treatment of elephantiasis
This disease could possibly be eradicated over the course of 5 years with universal chemotherapy
Elephantiasis (caused by Wuchereria)
Tropical pulmonary eosinophilia is a complication of infection by this worm
Wuchereria bancrofti (cause of elephantiasis)
T/F: Tropical pulmonary eosinophilia is a common, fatal complication of Wuchereria infection
False. It is a rare (0.5%) but fatal complication
This worm can cause pulmonary infiltrates
Wuchereria bancrofti (cause of elephantiasis)
T/F: Tropical pulmonary eosinophilia is solely caused by Wuchereria bancrofti.
False. Many types of worms can cause it, but Wuchereria is a common cause of this rare syndrome
Diagnostic stage of Wuchereria
Microfiliariae in blood
Diagnostic stage of Onchocerca (River Blindness)
Microfiliariae in tissue (skin)
Geographic distribution of Wuchereria
All tropical regions
Microfilariae of this worm are harmless, but microfilariae of this worm cause disease
Wuchereria microfiliariae are harmless (the adult form causes disease when it enters the lymphatics), but Onchocerca microfiliariae cause blindness
Intermediate host of Onchocerca (River Blindness)
Black fly (genus Simulium)
This is where to find adult Onchocerca in infected humans
Subcutaneous nodule at the site of the infecting black fly bite
Clinical signs and symptoms of Onchocerca
Dermatitis with severe itching, eye lesions, eosinophilia, subcutaneous nodules
Microfilariae of this worm cause dermatitis with severe itching
Onchocerca (River Blindness)
Pathogenesis of blindness caused by Onchocerca (River blindness)
Cornea: chronic keratitis and fibrosis
Iris: atrophy
Retina: chorioretinitis
T/F: There is an autoimmune mechanism involved in River Blindness
Geographic distribution of Onchocerca
Focal areas of tropical Africa, Central and South America
Diagnosis of this disease requires microfiliariae on a skin snip or adult worms in biopsy of nodule
Onchocerca (River Blindness)
Treatment of River Blindness (Onchocerca)
Ivermectin (once a year; it kills microfiliariae before they can do harm)
T/F: Ivermectin kills the adult and microfiliariael forms of Onchocerca
False. It is only effective against the microfiliariae.
This is the least serious of filiarial infections
Loa Loa
This worm causes symptoms due to migration of the adult worm through subcutaneous tissue
Loa Loa (Eye Worm)
T/F: Conjunctival migration is a common finding in Loa Loa (Eye worm)
False. Only 15% of travelers with Loa Loa present with conjunctival migration; most present with Calabar swellings
Chrysops is the intermediate host of this worm
Loa Loa (Eye Worm)
Intermediate host of Loa Loa
Chrysops fly
How long does it take for microfiliariae of Loa loa to mature in its host?
2 weeks
Diagnostic stage of Loa loa
Microfiliariae in blood
Infective stage of filariasis
Infective larvae transmitted from the blood-sucking fly to the human
How long does it take for Loa loa to mature once it has entered its human host
1 year
Survival time of Loa loa
Several years (10-20)
Calabar Swellings
Itchy, chicken egg-sized edematous lesion seen in Loa loa infections. A hypersensitivity mechanism caused by migration of adults (5 cm)
Geographic distribution of Loa loa
Tropical Africa only
Treatment of Loa loa
Surgical removal, chemotherapy (DO NOT USE IVERMECTIN)
Prevention of filiarial diseases
Avoidance of fly bites
What are the species, diseases they cause, their vectors, and the cause of pathology in the three filarial infections?
Wuchereria - Elephan - Mosquito - Adults in lymphatics
Ochocerca - River Blind - Simulium (black fly) - Microfiliariae in tissues
Loa loa - Chrysops fly - Adults in tissues
Clinical signs and symptoms of Loa loa
Calabar swelling, adult migrating in conjunctiva