Gastrointestinal and Ecto parasite life cycles (4.8.1) THREADWORM CARD 4 ONWARDS Flashcards
What are the type of worms, fleas, ticks, and scabies
Describe the properties of roundworms
- Invertebrates with long round bodies
- size from microscopic to 30cm
- More common in warm climates than in cooler temperate climates
- Most have cycle where eggs are found in soil –> either picking up in hands to mouth, enter via skin
- Infect plants, insects, vertebrates very succesfully, ascaris lumbricoides (human)
- >1 billion infected
- Infection through eating eggs off uncooked vegetables
- very large roundworms. Up to 30 cm, pencil thickness
- affects lungs (See attached image)
Describe the properties of hookworms
- Two most important are; Ancylostoma duodenale1 and Necator americanus2 (Australia: more common)
- Egg output 10-25,000 per day
- Eggs hatch < 24h, life cycle involves 2 moults to the strongyliform stage then waits for host to pass. Normally burrow into skin (No 1 is also infective through oral ingestion)
- transported in blood to lung; move up trachea
- enter oesophagus and attach to duodenum/jejunum 4th larval stage matures here, moulting its buccal capsule
symptoms:
- If low number-no visible signs
- In chronic infections, serious anaemia (blood loss)
- Additionally; In Australia
> A. canium almost develops in S.I., but produces severe inflammatory reaction of bowel: pain; diarrhoea
> peripheral blood eosinophilia.
Describe the properties of threadworms? Include symptoms, diagnosis, treatment and lifecycle
- Small threadlike
- Males 5mm Females 10mm
- Most common in temperate climates
- 25% of Humans
- Female dies after laying egg
Symptoms:
- Itching around anus can become intense-but that is about it
Diagnosis: egg detection: Scotch tape early morning detection of child perianal skin with torch also works-Worms glow in the light
Treatment: mebendazole or pyrantel pamoate (Povan) –> whole family MUST be treated if one member is found to harbour the parasite.
What are some other roundworms
See attached image
What are the different types of tapeworms? What are the lifecycles?
- Beef Tapeworm
- Pork Tapeworm
- Fish Tapeworm
- Diphyllobothrium
- Dog Tapeworm
- Echinococcus & Taenia spp.
What are examples of ectoparasites
- Scabies-Acarus scabiei
- Head Louse-Pediculus capitis
- Fleas-Ctenocephalides felis or canis
- Ticks - Soft (Argasidae) & Hard (Ixodidae)
Describe properties of fleas
- Ctenocephalides felis or canis (Pulex irritans (Human?))
- Mostly irritation
- Main problem is with carried organisms
> plague (Yersinia pestis)
> salmonella
> tularemia (Francisella tularensis)
> cystercoid stages of some tapeworms
Describe properties of lice (pediculosis)
- 3-4 species infect humans;
- Pediculus capitis (Head louse)-school kids
- Pediculus corporis (Body louse) –> no particular age (only uncleanliness)
- Pthirus pubis (Crab louse) –> Sexually active people term-pthiriasis
- Evolved to grasp human hair
- During feeding, release anticoagulants.
- Ill humans or animals can become large in No and can cause sig blood loss
- As with fleas, major problem is associated carried diseases generally specifically a body louse problem
- 1-1.5 month life span
Lice detection
- Presence of the parasites themselves
- heavy infection-can cause intense itching (pruritus)
- Very heavy infection- scarred hardened pigmented skin (vagabonds disease)
- Fecal pellets of head louse on shoulders.
- New nits -yellow/opaque, hatched eggs still present though for long time (pale /papery)
- > 150-300 per life span (8/day)
Associated disease
- Epidemic typhus (ricketssia prowazekki –> human infected by rubbing infected lice faeces into wound)
- Trench fever (Rochalimaea quintana –> mostly during WW1, rare now)
- Louse-borne relapsing fever (borrelia recurrentis –> humans infected by killing ‘popping’ lice and the fluid entering wound
Describe properties of bedbugs
- Cimex lectularis
- 5-8 mm long (adult)
- Life cycle – egg –> nymph (1-3 weeks) –> adult (1-2 months) lays eggs….
- Inflammatory response to bite variable
- Feed weekly but can go 1 year without meal
- blood meal at night from people in vicinity
- NOT carriers of other diseases
Describe the properties of ticks
Disease carriers
>ricketssia infections
>lyme disease –> eastern states (mainly USA)
>some viral
>Haemoorhagic fever
Tick paralysis
> Neurotoxins - saliva –> not ifnection
Ticks (soft)
- No distinct head (mouthparts not visible from above)
- Quick feeders – 30 min
- Live in nests close to host
- Can use different hosts (bats, dogs, reptiles)
- can survive off of hosts for years
- Larva - 6 legs, nymph to adult = 8 legs
- Multiple nymph stages (2-8)
Ticks (hard)
- Tough, leather-like integument
- 1,2 or 3 host life cycles
- Australian paralysis tick (ixodes holocylys)
- Attached image for life cycle
1 Host ticks (hard)
- Larva to Nymph to Adult all on one animal
- Eggs still laid on ground though
- Larva hatch and await new host to start cycle again
2 Host ticks (hard)
- Usually larva and nymph on one host
- Nymph moves back into environment to mature
- Adult on the 2nd host
3 Host
- All stages on different hosts – much maturation in environment (can take 2-3 years between complete cycles)
When does tick paralysis occur? What are some of the symptoms?
Starts several days after tick attachment (when the Ixodidae tick reaches rapid feeling phase –> it salivates rapidly injecting much toxin)
Symptoms:
- unsteady gait
- weakness of limbs & lethargy
- paralysis progresses over couple of hours.
- Severe cases = ventilatory failure (usually children).
- treat in intensive care (possible antitoxin needed – although some people allergic
Describe the properties of scabies
Arachnid mite: sarcoptes scabiei
- Simple life cycle-single host (10-17 d)
- 0.4mm long
- 2-3 eggs day laid during burrowing
- 48 hours later hatched
- Rash common -> creased skin (except on head)
- Person-person contact or sheets (2d)
- In animals (mange) –> different species
