Filariasis Flashcards
life cycle of dracunculus medinensis
- human drinks unfiltered water containing copepods with L3 larvae
- larvae are released the copepods die. Larvae penetrate the host’s stomach and intestinal wall. They mature and reproduce
- fertilised female worm migrates to surface of skin, causes a blister and discharges larvae
- L1 larvae released into water from the emerging female worm
- L1 larvae consumed by a copepod
- larvae undergoes two bolts in the copepod and becomes a L3 larvae
WHO target on guinea worm
eradication campaign has been a big success thanks to distribution of pipe to block ingestions of worms in drinking water
WHO target on lymphatic filariasis
one billion at risk, mostly in tropical regions, and 40 million severely incapacitated or disfigured. two separate drugs to prevent transmission
WHO target on river blindness
caused by infection by the nematode worm. about 500,000 people thought to be blinded, mostly in sub-Saharan Africa
WHO target on schistosomiasis
life-threatening urinary or liver damage or cancers. 76 million children need single dose treatment
what type of cell is Filariasis?
phylum nematoda
belongs to superfamily filaroidea
what is ovoviviparous?
producing eggs that are hatched within the body, so that the young are born alive but without placental attachment
which are the developmental stages of filariasis?
egg –> L1 –> L2 –> L3 –> L4 –> adult
when does the development arrests?
at L1 and L3
how many species of filarial nematodes use humans as the definitive host?
9
what is a definitive host?
the one in which the sexually reproducing adults develop
how are filarial nematodes transmitted?
by blood-feeding insects
what are vectors?
intermediate hosts
groups of filarial nematodes according to the niche they occupy
- lymphatic filariasis
- subcutaneous filariasis
- serous cavity filariasis
what does lymphatic filariasis involve?
lymphatic system, including the lymph nodes - can cause elephantitis
examples of species that cause lymphatic filariasis
Wucheria bancrofti, Brugia malayi, Brugia timori
what does subcutaneous filariasis involve?
subcutaneous layer of the skin, fat layer
examples of species that cause subcutaneous filariasis
Loa loa (African eye worm), Onchocerca volvulus (riverblindness), Dracunculus medinensis (Guinea worm), Mansonella streptocerca
what does serous filariasis involve?
serous cavity if the abdomen
examples of species that cause serous cavity filariasis
Mansonella perstans ad Mansonella ozzardi
what is lymphatic filariasis’s vector?
culex mosquitos
lymphatic filariasis infection cycle
- mosquito takes a blood meal (L3 larvae enters skin)
- adults in lymphatics
- adults produce sheathed microfilariae that reach the blood stream
- mosquito takes blood meal (ingests microfilariae)
- microfilariae shed sheaths, penetrate mosquito’s midgut, and migrate to thoracic muscles
- L1 larvae
- L3 larvae
- Migrate to head and mosquito’s proboscis
which microfilaria are sheathed?
Wuchereria bancrofti, Brugia malayi and Brugia timori
what is the sheath?
the eggshell
what time of the day is there the maximum presence if microfilariae in the blood?
at night
how is Wucheria and Brugia microfilariae cycles?
periodic
what type of disease is filariasis?
a spectral disease
what types of people ate there in endemic areas?
3 classes:
- microfilaria positive
- chronic pathology
- endemic normal
characteristics of a microfilaria positive person
usually asymptomatic, but the infection is active
–> due to defective T cell proliferative responses
characteristics of a chronic pathology person
cleared infection - normal proliferative response - immunopathology
characteristics of an endemic normal person
no or very low level infection - normal immune response
what type of effects does filariasis cause?
trans-generational effects
where are the endosymbiotic bacterium?
in insect-transmitted filarial worms
how are most species of filarial worms?
harbour bacterial and endosymbionts
what family do endosymbiotic bacterium belong to?
members of the Wolbachia family, related to rickettsia
how can Wolbachia DNA be detected?
by chemotherapy
what is Wolbachia appears to be essential for?
for worm fertility/viability/survival
what happens to the worm if you kill the Wolbachia?
it sterilises the worm
what is wolbachia involved in in riverblindness?
appears to have a role in pathogenesis particularly after death of microfilariae
drugs for killing adult filarial worms?
- Albendazole (anthelmintic) combined with ivermectin
- a combination of diethylcarbamazine (DEC) and albendazole is also effective
- tertacyclines against endosymbiotic bacterium - Wolbachia –> azithromycin for treatment of lymphatic filariasis
what is the vector for river blindness (onchocerciasis)?
stimulium damnosum or Dipteran fly (insect vector)
what does the stimulium damnosum requires for its larvae?
oxygenated water
do mosquitos need oxgenate water for its larvae?
no
the onchocerca vulvus (causative agent for river blindness) life cycle
- blackfly takes blood meal (L3 lavae enter the wound)
- subcutanenous tissues
- adults in subcutaneous nodule
- adults produce unsheathed microfilariae that typically ate found in skin ad in lymphatics of connective tissues, but also occasionally in peripheral blood, urine and sputum
- blackfly takes a blood meal (ingests microfilariae)
- microfilariae penetrate blackfly’s midgut and migrate to thoracic muscles
- L1 larvae
- L3 larvae
- migrate to head and blackfly’s probscis
what does river blindness cause in the head of infected people?
protuberances
what are other skin manifestations of onchocerciasis?
- sowda
- leopard skin
- elephant skin
what is sowda?
a cutaneous condition, a localised type of onchocerciasis
what is leopard skin?
a term referring to the spotted depigmentation of the skin that may occur with onchocerciasis
what is elephant skin?
when the skin eventually loses elasticity in onchocerciasis
what are the main objectives in the OCP (Onchocerciasis control programm(, now the APOC (African programme onchocerciasis control)?
- vector control
- screening and drugs:
- diethylcarbamazine (DEC) and the Mazzotti reaction
- ivermectin: diminish Mazzotti reaction
- tetracyline: sterilises adult females
what is the Mazzotti reaction?
Mazzotti reactions can be life-threatening, and are characterized by fever, urticaria, swollen and tender lymph nodes, tachycardia, hypotension, arthralgias, oedema, and abdominal pain that occur within seven days of treatment of microfilariasis.
loa loa infection cycle
- fly takes blood meal (L3 larvae enter the wound)
- adult in subcutaneous tissue
- adults produce sheathed microfilariae that are found in the spinal fluid, urine, sputum, peripheral blood and in the lungs
- fly takes a blood meal (ingests microfilariae)
- microfilarae shed sheaths, penetrate fly’s midgut, and migrate to thoracic muscles
- L1 larvae
- L3 larvae
- migrate to head and fly’s sproboscis
