Lecture 7: Ectoparasites: Exploiting the behavior of wild malaria vectors Flashcards
What are the two classes the arthropods can be divided into? Insecta and arachnida
Insecta and arachnida
What roles can arthropods play in human health?
Ectoparasitosis (e.g. scabies mite), endoparasitosis (e.g. fly larvae that cause myasis: invade tissues), poisoning (wasp and bee stings, spider bites), allergic reactions (e.g. house dust mite), nuisance (e.g. midges and black flies in summer), delusory parasitosis (condition where you think there are arthropods in your environment or your body, when they are not there) and as vectors of disease agents like viruses bacteria and parasites (e.g. malaria mosquitoes, black flies, ticks, tsetse flies, blood-sucking bugs, fleas, sand flies, body lice)
What are ectoparasites?
Organisms living at the expense of other species of organisms (hosts), particularly on the external body surfaces. Damage occurs as a result of bloodfeeding, burrowing, crawling or scraping the skin surface
What are the different blood-sucking lice that live on humans?
Blood-sucking louse (Pediculus humanus) lives on the head, the blood-sucking crab louse (Phtirus pubis) live in pubic hair and are transmitted sexually, the body louse lives on the body or on clothing. The different types of lice are adapted to their environment and don’t switch places. You won’t find a crab louse on your head!
Which bed bugs are associated with shabby conditions?
The blood-feeding bed bugs! They can however also be found in more luxury hotels. They can hide in small nooks and crannies and come out at night to hunt. Getting rid of these bed bugs is very difficult and thus expensive. They are resistant to insecticides, so heat treatment is needed to get rid of an infestation. You need to close off a room and bring a heater and heat the room up to 60 degrees Celsius. This can cost up to 1000-2000 euros PER ROOM and in addition the furniture in the room can be affected.
Which ectoparasite is associated with damp grass?
The harvest mite/velvet mite! They live in damp grass areas. When you walk through this area barefoot, they jump on your leg and start feeding on your tissue. They excrete a factor that liquifies tissue, enabling them to feed.
Which ectoparasite has infested ~80% of Dutch farms?
The poultry red mite (Dermanyssus gallinae). They have enormous population sizes (up to 50.000 per chicken) and cause reduced egg laying, stress and death in chickens. For the farmers they are a nuisance, as they cause itching.
What is myiasis and what is an example of a parasite that causes it?
Myiasis is the invasion of living (animal) tissues by arthropods, e.g. by Dermatobia hominis.
What is the lifecycle of Dermatobia hominis?
This fly lays its eggs on another insect, e.g. a mosquito. When this mosquito bites another animal, e.g. a cow (but can also be a human), the eggs stick to the cow. They hatch and the larvae eat their way through the cow. It emerges as a grown larva, drops to the ground. Here it incubates in the soil until it becomes an adult and the cycle starts anew.
What is phoresis?
When the eggs of an insect, e.g. Dermatobia hominis “hitchhike” on the back of another insect to spread
Are mosquitos just flying syringes, spreading vector-borne diseases?
No. They have quite an intricate system for feeding. There is not just one channel, but two (one for feeding and one for excreting saliva). Mosquito saliva contains ~20 polypeptides (Ae. aegypti), a.o. anti-coagulants and vasodilators, this makes it easier for the mosquitos to take up the blood.
What is the soluble immune response to mosquito saliva?
IgG and IgE antimosquito antibodies next to histamine, serotonine and bradykinine ( which causes the pain/itch associated with a mosquito bite)
What is an underestimated part of emerging diseases?
Spillover from wild animals to domestic animals before it reaches the humans. In addition, vectors can also be a factor in this spillover.
What containment strategy can benefit people looking at spillover?
Early detection and forecasting readiness in diseases in animals to predict which disease can be the next zoonosis. In this manner, very early intervention can be done.
What is are the parameters involved in the basic reproductive number for a vector-borne disease?
R0= (mbca^2p^n)/(r(-lnp)). m = vector density relative to host b = transmission coefficient from vertebrate to vector c = transmission coefficient from vector to vertebrate a = biting habit (feeding frequency * human blood index) p = daily vector survival rate n = extrinsic incubation period r = host recovery rate
