Worms Flashcards
What are three types of worms
- Nematodes (roundworms)
- Trematodes (flatworms)
- Cestodes (tapeworms)
Where are nematodes found
- Intestines
2. Tissues
Where are trematodes found
- Blood
- Liver
- Lung
- Intestinal
Where are cestodes found
- Non invasive
2. Invasive
Can adults worms reproduce outside the body
No, they require specific environmental conditions of the host
What is the pre-patent period
Interval between infection and appearance of eggs in the stool
Where are intestinal nematodes transmitted
From human to human via eggs or larvae
Faecal-oral spread
Why is the egg or larva no infectious when first passed
Because it needs to undergo a period of development in the soil
What is ascariasis
Infection of the intestines with nematodes
How long is the ascaris lumbricoid
15-30 cm long
How long does the ascaris lumbricoid live for
A year or more
Pre-patent period of ascaris lumbricoid
60-75 days
Sundrome is associated with larval migration through the lung
Loeffler’s syndrom e
How long does it take for Loeffler’s syndrome to occur
10-14 days after infection commenced
What is the effect of adult worm migration through the body
Asymptomatic
Leads to malnutrition
How do diagnose for, infection
Stool microscopy for eggs
How is worm infection treated
Piperazine, pyrantel
Levasimole
Mebendazole
What does Hookworm cause
Ancyclostoma Duodenal
Nectar Americanus
How does Hookworm enter the body
Through the soil if you’re barefooted
Life-expectancy of hookworm
1-5 years
Pre-patent period of the hookworm
40-100 days
What is the most common reason for iron deficiency
Infection by hookworm
Life cycle of the hookworm
- Filiform larvae penetrate exposed skin and migrate to the lungs
- Break out into alveoli are swallowed and develop into adults at the small intestines
- Adults attach to mucosa of duodenum and jejunum
- Females produce eggs that are passed into the soil with faeces and hatch within 24 hours
- Infectious filariform larvae develop after 5-10 days in moist soils
Clinical features of hookworm
- Ground itch (At site of entry of larvae)
- Mild pulmonary symptoms due to migration
- Iron-deficiency
How is Hookworm treated
Iron supplements (Pyrantel, mebendazole)
PPP of Enterobius Vermicularis
40 days
Lifespan of Enterbius
56 days
Lifecycle of Enterobius
- Females emerge from anus at night
- Lays eggs around the anus and dies
- Eggs embryonate within 4-6 hours causing scratching and eggs under fingernails
- Formites contaminated with infective eggs
- Ingested eggs move to duodenum where they hatch
- Mature adults migrate to caecum
Four clinical features of Enterobius
- Prunitis ani
- Appendicitis
- Vaginal penetration
- Paranasal sinuses
Diagnosis of enterobius
Microscopy sellotape strip from perineal region
Treatment of enterobius
Iron supplements
PPP of whipworms
70-90 days
How long are whipworms
2-5 cm long
Life cycle of whipworms (Trichuris Trichuria)
- Eggs are ingested by a suitable host
- Immature larvae hatch from eggs when they arrive at small intestine
- Larvae pass into large intestines
- Larvae embedded in the mucosa via thin anterior ends, reach sexual maturity and mate
- Trichuris app are found in the caecum, ascending colon and throughout the colon
- Eggs passed into environment in host faeces
- Embryonation in moist soil takes 21 days
Where is whipworm found
Large bowel
`Clinical features of whipworms
Asymptomatic Co-ecists with ascaris lumbricoides Trichuriasis Bloody diarrhoea Reactal prolapse Anaemia
What does Stronglyloides stercoarlis cause
Strongyloidiasis
Length of Strongyloid
2mm
PPP of strongyloid
17-28 days
Life cycle of strongyloides stercoarlis
- Filariform larvae penetrate the host’s skin and migrate to lungs via blood
- Larvae break out into alveoli, crawl over glottis and swallowed
- Development in Jejunum
- Eggs laid after ingestion
- Small no. eggs laid be females whose head is burrowed in sub-mucosa of small intestines
- Eggs hatch immediately in intestines and rhabditiform larvae passed into faces
- Infectious filariform larvae develop in the intestines and penetrate tract or perianal skin.
Clinical features of Strongyloides
- Pruritis at larval entry
- Larval migration into lungs
- Malabsorption with eosinophilia
- Skin rashes due to auto-infection
- Hyperinfection syndrome
What type of worm is larva migrans caused by
Toxocara canis and T cati
Life cycle of larva migrant
Eggs ingested and develop into larva
Clinical features of larva migrant
- Children effected
2. Pyrexia, eosinophilia and hepatomegaly
How do we diagnose larva mirgans
Serology
How is larva migrant treated
Mebendazole
Albendazole
What is Ocular Toxocariasis
- Larvae trapped in retina
- Granulomatous reaction takes place
- Causes blindness and increased retinal mass
What condition can we accidentally diagnose a patient with ocular toxocariasis with
Retinoblastoma
Diagnosis of ocular toxocariasis
Serology and antigen detection in aqueous humour
What causes cutaneous larva migrant
- Dog hookworms and ancyclostoma canine
Clinical feature so cutaneous larva migrant
Lesions at sites where larvae penetrate
How is cutaneous larva migrant spread
Contact with dog faeces
How is cutaneous larva migrant treated
Topical.systemic thiabendazole and topical cryotherapy
Life cycle of anisakiasis
- Definitive host is infected when eating food
- Adult ascarides found in stomach
- Passed through host faeces
- Eaten by marine animals
- Migrates into tissues of fish, squid
PPP of Dracunculus medinesnsis
1 year
Length of Dracunculus
100 cm
Life cycle of Dracunculus medinesnsis
Man swallows cyclops sp in contaminated water
- Infected larvae liberated digestive juices and penetrate the gut wall
- Larvae develop and occupy subcutaneous tissues
- After one year, female’s head approach skin where a blister forms
- Blister bursts and larvae leaves through discharge
Clinical feature of Dracunculus
- Localised pain and urticaria at site where worm protrudes
- Tetanus
- Blisters
Diagnosis of dracunculus
Drop of water on ulcer promotes egg release
Treatment of Dracunculus
- Wind out worm
2. Mebendazole
Why do we use mebendazole
Eases extraction
How do we prevent further infection by dracunculus
Sieve of water
What worm causes elephantiasis
Wuchereria Bancroftii
How is Wuchereria Bancroftii diagnosed
Demonstration of microfilaria in blood taken between 11 and 1 am
Serology
How is Wuchereria Bancroftii treated
DEC and Ivermectin
What is Onchocerciasis
Hanging groin, river blindness
Where are worms found in Loa Loa
Retina
Life cycle of Trichina Spirals
- Larvae digested from muscle enter epithelial lining and becomes sexually mature
- Male and female worms in intestinal wall mate and produce larvae
- Newborn larvae pass through lymphatic system into the blood
- Larvae encyst ini striated muscle
- Infected meat is ingested by humans and carnivorous or omnivorous animals
What causes Trichinosis
Trichiniella Spiralis
Clinical features of Trichinella in muscles
- Asymptomatic
- GI disturbance as worms develop
- Fever, headache, cough at 8 weeks
- Periorbital oedema, haemorrhage
- Splinter haemorrhage
- Neurological signs (deafness)
- Myocarditis
- Pneumonitis
What meat is Tania Saginatum found
Beef
Length of Tania Saginatum
5-10 metres
Lifespan of tania saginatum
30 years
PPP of tania saginatum
12 weeks
Life cycle of Tania Saginatum
Caught by eating undercooked beef containing cysts
Clinical features of tania saginatum
Asymptomatic
Proglottids may emerge from human anus
Diagnosis of tania saginatum
Stools of eggs and proglottids
Treatment of taenia saginatum
Niclosamide
Praziquantel
Life cycle of Taenia Solium
- Solex attaches to intetsine
- Adult tapeworm
- Gravid proglottid in faeces or environment
- Onchosphere hatches and penetrates intestine wall
- Cystercus in lungs, brain, eye or connective tissue
What worm causes neurocysticercosis
Pork tapeworm
What tapeworm causes HYDATID DISEASE
Echinococcua Granulosus - DOG
What is caused by Echinococcus Multilocularis
Alveococcosis
How can we get Diphyllobothrium latum
Fish
What is sparganosis
An infection caused by Diphyllobothrium Latum
What is the intermediate host used by flukes to spread
Snail
Where are flukes found
Blood
Liver
Lung
Bowel
Name an adult fluke
Schistosoma
Normal life span of a fluke
3-5 years
How long is an adult fluke
12 cm
What does Schistosoma infection cause
Katayama fever
What is Katayama fever
An initial immune-complex mediated illness 2-4 weeks after exposure
What proportion of patients infected with Schistosomia have Katayama fever
50%
Why is Katayama physiologically caused
T-cell mediated immune response to egg surfaces leads to cytokine release
IL-12 can suppress egg-induce pathology (mediated by INF-gamma)
Granuloma development
Fibrosis if egg laying continues
Where do adult S haematobium reside
Liver
Where do S haematobium egg migrate to
Bladder
What damage can S haematobium do in the bladder
- Pseudopapillomata (granulomatous lesions)
- Obstructive uropathy (reversible if short duration and treated)
- Calcified bladder
- Squamous cell bladder cancer
- Kidney stones
Clinical features of S mansoni
- Asymptomatic
- Iron deficiency
- Hepatosplenomegaly
- Pseudopolyposis
- Fibrosis of liver
- Portal vein hypertension
How is Schistosomia caused
- Serology
- Urine (time-consuming)
- Stool (67% positive)
- Rectal Biopsy
- Ultrasound
How is Schistosomia-caused infection treated
- Praziquantel
- Isoquinoline
- Metriphonate
- Oxamniquine
