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MMI 426 > Filariasis > Flashcards

Filariasis Flashcards

1
Q

Filariasis - lymphatic

A

Wuchereria bancrofti
Brugia malayi
Brugia timori

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2
Q

eye/skin - filariasis

A

Loa loa
Onchocerca volvulus
Mansonella streptocerca
Mansonella ozzardi
Mansonella perstans

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3
Q

W. bancrofti

A

nematode = round

adults reside in lymph vessels and nodes

long, slender, creamy white, thread-life worms with tapered ends

adult F = 80-100 nm x 0.2-0.2 mm = longer than M (40 mm x 0.1mm)

females are viviparous -> sheathed microfilaria

males have corkscrew tail, two spicules at posterior end

M & F live coiled together in the lymphatics

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4
Q

lifecycle of W. bancrofti

A
  • humans are only definitive host (reservoir for infection)
  • intermediate = Sculex mosquitos but also anopheles in rural Africa and Adian mosquito in Pacific islands

3rd stage larvae (infective) injected into person during mosquito blood feed -> lymphatic vessels -> node = mature to adults in few months

male and female worms mate and produce first stage larvae; male stage die after mating and F live up to 5-10 yrs

-> lymphatic vessels -> bloodstream (taken up by mosquitoes)

mosquito gut = microfilaria shed sheath 1-2 hrs of ingestion -> through stomach wall -> thoracic muscle (develop filariae form with 3rd stage larvae) -> infective forms go to mouth pods of mosquito (10-14 days development in mosquito)

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5
Q

female W. bancrofti microfilaria

A

50 000 microfilaria/year

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6
Q

pre-patent period of E. bancrofti

A

time of inoculation of 3rd stage larvae to detection of microfilaria in blood = 80 to 100 days

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7
Q

W. bancrofti microfilaria

A
  • diagnostic form (first stage microfilaria)
  • sheathed (no stain)
  • gently curved body
  • tail tapered to a point
  • nuclear column loosely packed
  • no nuclei in tail
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8
Q

T or F. 90% of skin/eye filariasis is W. bancrofti

A

F! lymphatic filariasis

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9
Q

vectors of W. bancrofti

A
  • mosquitoes (inefficient transmitters); need to stay in endemic areas for a while to be infected
  • microfilaria display no nocturnal periodi ity
    > in bloodstream from 10 pm to 2 am
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10
Q

hosts of W. bancrofti

A

only definitive is human
mosquitoes are intermediate host and vector

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11
Q

pathogeneis of W. bancrofti

A
  • adult worms do not cause inflammation but obstruction of lymph flow
  • symbiotic bacteria seen in the worms = cause some inflammation of lymphatic filariasis
  • Wolbachia required for homeostasis of adult filaria
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12
Q

clinical presentation of W. bancrofti

A

in endemic areas, can be asymptomatic or subclinical = abnormalities seen in tests (blood and proteins in urine)

  • increased eos, IgE, microscopic blood and protein in urine

early infections can result in pain, redness, and swelling of involved lymph vessels, and fever

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13
Q

chronic infection of W. bancrofti

A

lymphoedema
> genitals (M)
> breasts (F)
> limbs
- recurrent bacterial infections
- elephantiasis

not seen in travellers; years of exposure and repeated infections are required to see chronic changes
chronic = high depression rate and lose ~29 days of work

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14
Q

diagnosis of W. bancrofti

A

blood collection between 10 pm to 2 am = Giemsa or wright stain; microfliaria seen; gold std

filarial Ag test
> blood can be collected at any time
> more sensitive than blood smears

antifilarial Ab tests
> only useful in travellers from non-endemic areas; can distinguish between current or past infections and some cross-reactivity

molecular tests
> research only

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15
Q

T or F. Treatment for W. bancrofti exists but does not reverse elephantiasis

A

T

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16
Q

10% of lymphatic filiarisis

A

Brugya
- roundworm
- adults reside in lymph vessels and nodes

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17
Q

species of Brugya

A

B. malayi
B. timori

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18
Q

transmission of Brugya

A

host = humans, domestic and wild animals (ZOONOSIS)

vector = anopheles, Aedes, and Mansonia mosquitoes

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19
Q

Where is B. timori found?

A

sequestered to Timor islands of Indonesia

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20
Q

Lifecycle of Brugya

A

same as W. bancrofti except human stages also occur in animals

most Brugyan filaria also exhbit nocturnal periodicity = highes # microfiliaria in bloodstream between 10 PM to 2 AM

subperiodic variants = microfliaria variants in blood during daytime as well

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21
Q

clinical presentation of Brugya

A

same as W. bancrofti (acute, asymptomatic, chronic)
*chronic usually occurs below elbows and knees *

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22
Q

diagnosis for Brugya

A

blood collection between 10PM to 2 AM; no available antigen test

antibody tests and only useful for travellers from non-endemic areas

molecular tests for research only

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23
Q

identification of B. malayi

A

175-230mm

Sheathed (stains pink in Giemsa)

Tail tapered to a point

Nuclear column more tightly packed

Terminal and subterminal nuclei in the tail

24
Q

identification of B. timori

A

larger; ave 310 mm

sheathed but does not stain

longer cephalic space

more nuclei in tail and tail tapered

nuclear column more tightly packed

25
Q

Treatment and prevention of Brugya

A

same as W. bancrofti

but cannot be eliminated from endemic areas due to animal reservoirs

if to decrease disease burdens = prevention of mosquito bites = bed nets and screens

26
Q

African eye worm

A

Loa loa

27
Q

T or F. Loa loa probability of infection increases with age

A

T

28
Q

T or F. Travellers can be infected with Loa loa

A

T, but requires months to years of exposure

29
Q

Hosts of Loa loa

A

only humans

30
Q

Where is Loa loa found?

A

west and central frics

31
Q

transmission of Loa loa

A

bite of deer or horse fly
(Chrysops/ tabanid fly)

32
Q

Loa loa life cycle

A

infective third stage of larvae inoculated into skinof host during blood meal of tabanid fly

flies attracted to movmeent; bite in day time
]
filarial larvae penertrate through subcutaneous stissue and mature in to adult worms ; 3 month process

adult worms can migrate to any areas of body including conjutival tissue if eye

6-12 months post infection, female produces microfilaria into bloodstream -> taken up by tabanid fly

mature into infective third stage larvae in 10-12 days

adult worms can live for up; to 20 years but cant multiply in humans so adult worm burden increases w new infections each time new larvae are infected during blood meal of tabanid fly

33
Q

clinical presentation of Loa loa

A

Most asymptomatic

Transient localised swellings (Calabar swellings)
> most likely allergic rxns

Migration across subconjuntiva; usually resolve after worms leave eye ; trip across eye = 10-20 mins

Symptoms recur as adults worms live up to 20 years

Complications
- Heart
- Kidneys
- Brain

34
Q

diagnosis f Loa loa

A

when adult worm seen travelling in eye or microfilaria visualization in blood smear; Females larger

travel at rate 1cm/min
increased eos, IgE, blood, protein in urine

diurnal periodicity; microfilariae at highest conctn in blood during 10Am to 2PM

serology = antibodies to Loa loa but most useful for diagnosis of diseases in travellers

antigen test being developed
molecular assays available

35
Q

Identification of Loa loa

A

250 - 300 um

sheathed
tapered tail
nuclei extend to end of tail

similar endemicity to W. bancrofti and Mansenella

36
Q

treatment of Loa loa

A

used for symptomatic pts only

rule out onchocerciasis first; no Wolbachia (endosymbiont bacteria)

37
Q

2nd leading infectious cause of blindness

A

Onchocera volvulus

38
Q

river bliondness

A

O. volvulus

39
Q

hosts of O. volvulus

A

only humans
transmission viablack fly (Simulium spp)

40
Q

where does O. volvulus breed?

A

near fast flowing streams and rivers = river blindness

41
Q

Four countries have been successful in eliminating the river blindness

A

Columbia, Mexico, Ecuador and Guatamala

42
Q

O. volvulus life cycle

A

humans become infected 3rd stage fly larvae -> skin and mature there (12-18 months)

female adult worms live in nodules while males live close by and travel between nodules to fertilize females

adults live 10-15 yrs in humans and microfilaria have lifespan of 12-15 months if not ingested by black fly

when black fly takes blood meal from infected ppl, they go to flight muscles of fly; in one week = 3rd stage larvae and go to bite parts of fly

female black flies eat a blood meal to ovulate; diseases only transmitted by female

black flies bite during the day

43
Q

T or F. Endosymbiont Wolbachia is present in O. volvulus

A

T!

44
Q

clinical presentation of O. volvuvus

A

Asymptomatic in some

Most have
itchy skin
rashes,
nodules under the skin
vision changes (rxns to dead or dying filaria)
-progress to blindness

inflammation in skin can resullt in long-term damage = leopardskin appearance and thinning (cigarette paper appearance)

45
Q

hanging groin

A

O. volvulus

46
Q

The inflammation caused by O. volvulus larvae that die in the eye results initially in __________ lesions on the cornea that without treatment progress to permanent clouding of the cornea, resulting in _________

A

reverisble; blindness

47
Q

diagnosis of O. volvulus

A

gold std = detection of microfilaria in skin snips; prepatent period = 12-18 months from initial infection to presence of microfilariae in skin

adult worms in skin nodules are seen when surgically removed

serology not useful

48
Q

O. volvulus filaria description

A

unsheathed
tail tapers to a point and often sharply bent
no nuclei in tail

49
Q

Mansonella species

A

M. perstans = solely human parasite

M. ozzardi = primarily human but monkeys can be infected too

M. streptocerca = primarily humans but wild chimps have been infected

50
Q

Mansonella epidemiology

A

M. perstans
West, East and Central Africa, Central and South America
Transmitted by biting midges

M. ozzardi
Central and South America, Caribbean islands
Transmitted by mainly by biting midges; black flies in some areas of S. America & Haiti

M. streptocera
Tropical rain forests of western and central Africa
Transmitted by biting midges

51
Q

M. perstans clinical presentation

A

transient subcutaneous swellings
inflammation of the membranes covering the heart or lungs
impaired vision if the microfilaria enter the eye
fever, tiredness, ab pain, joint pains

52
Q

Mansonella sp. lcinical presentation

A

largely symptomatic/mild

if symptoms do occur, hard to know if due to Mansonella or bc of co-infection w other parasites

53
Q

identification of M. perstans

A

adult worms in tissue or microfilaria in blood

unsheathed
round, blunted tail with nuclei extending to the end

round terminal nucleus

54
Q

M. streptocerca clinical presentations

A

itchy skin
thickening of skin
enlarged lymph nodes in axilla and inguinal areas

55
Q

identification of M. streptocerca

A

sharply curved tail at posterior end
need skin snips for ID

56
Q

how to treat Mansonella spp.

A

treated with same drugs used for lymphatic filiarisis
infection in travellers uncommon

57
Q
A

MMI 426 (20 decks)

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