Parasitology - Lecture 3 - 1/11 - Ectoparasites

explain where the ectoparasites come from

arthropoda

• insecta

• arachnida

Role of arthropods in human health

• ectoparasitosis

  • scabies

  • mite

• endoparsitosis

  • larvae that cause myasis; larvae enter body

• poisoning

  • bee stings

  • wasp

• allergic reaction

  • house dust mite

• nuisance

  • midges and black flies in summer

• delusory parasitosis; condition where you think you have an infestation of parasites, not really there

• arthropods can be vectors of disease agents, such as viruses, bacteria and parasites

  • malaria mosquitos

  • black flies

  • tsetse flies

  • blood sucking bugs

  • fleas

  • sand flies

  • body lice

    • fleas and lice can carry disease but can also cause an infestation themselves

Definition ectoparasites

Organisms living at the expense of other species of organisms (hosts), particularly on the external body surfaces. Damage as a result of blood feeding, burrowing, crawling, or scraping the skin surface.

role of ectoparasites in causing nuisance

• blood sucking louse. obligate human ectoparasite

  • eggs are laid and hatch to the skin.

  • body louse (different species from head louse). can be a vector of louse borne typhus

  • blood sucking crab louse (schaamluis); sexually transmitted

• blood feeding bed bugs

  • resistent to chemicals

  • aggregation due to secretion of pheromones (call mates)

• Harvest mites; allergies caused by arthropods

  • saliva causes allergic reaction, excrete enzyme that dissolves tissue, eats this.

  • live in moist grassy areas

  • larvae stages cause harm (only 6 legs instead of 8)

• nuisance biting in poultry; poultry red mite

  • 50000 mites per chicken, chicken can die from anemia

  • reduced egg laying

  • nuisance for poultry farmers (itch)

  • 80% of dutch farms infested

Role of endoparasite

phoresis (one organism uses the other for transportation) resulting in myiasis (fly lays eggs on host, larvae burrow into tissue until they are fully grown and fall on soil).

Role of ectoparasites in transmission

• transmission of yellow fever by mosquitos was proved;

  • two groups of people, mosquito hut Very hygienic) and formite hut (very dirty hut)

  • only group with mosquitos got ill, thus it was not transmitted through bodily fluids

• Mosquito bite; saliva contains 20 polypeptides with anti coagulants and vasodilators. IgG and IgE anti-mosquito antibodies are produced next to histamine in response to the saliva, which causes itching.

Explain spill over

• often diseases spill over from livestock to human population through direct contact.

  • vectors play a role here

• livestock gets infection from wildlife, bats, rodents etc.

Basic reproductive number for vectors

• definition; Definition: The number of new infections resulting from the introduction of an infection into an immunologically naive (= susceptible) population.

  • 0 > 1 a disease will spread.

  • 0 < 1 a disease will decline and eventually die out.

• m = vector density relative to host (number of mosquitos).

  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 (the time it takes before a mosquito becomes infectious).

  r = host recovery rate.

• physical barriers; peritrophic membrane, midgut, hemolymph, salivary gland

• vector response; micro-encapsulation, melanization, antibacterial peptides, RNAi, innate immunity (Toll, Jak-STAT, IMD)

• all this together means that not every mosquito turns into vector)

Malaria, explain how it is an ancient, rampant and emerging problem

• ancient in the Netherlands

  • vector was common in the Netherlands (coastel areas)

  • mass drug administration with quinine helped eliminate plasmodium vivax

  • improvement of living conditions

  • 1970 - malaria free

  • role of ecology; the question remains if malaria can come back due to the increasing abundance of anopheles plumbeus

• rampant in Kenya

  • plasmodium falciparum

  • 75% of people at risk

  • indoor vector control (bed nets and spraying)

  • role of ecology; question remains if using bed nets can lead to behavior change of mosquitos. They can start biting earlier during the night when people are not sleeping yet.

• emerging problem in Malaysia

  • plasmodium knowlesi, 68% of hospitalized cases

  • macaques are reservoirs

  • no human to human transmission

  • role of ecology; what are the effects of timber and palm oil production. animal and humans live closer together.

anopheles mosquito species are primary vectors of plasmodium species.

Control strategies of malaria

• environment management;

  • napier grass

• biological control

  • entomopathogenic fungi; fungi indoors that kill insects

• behavioral manipulation

  • solar powered and odor baited mosquito traps; Based on olfactory sensilla on the antennae of mosquitos, that are involved in smelling odors that attract the mosquitos.

    • By implementing these odors into a trap outsides homes, mosquitos can be lured and trapped. By doing so, the mosquitos can be removed from the general population.

  • 5 compound blend is created that consists of odors of humans, optimal for anopheles mosquito species

  • trap is solar powered to be able to use fan that can spread the odor around in the trap

  • social science and community involvement were important

  • parasite prevalence reduced by 30%, malaria mosquito reduced by 70%

  • future; applying traps in other settings, making traps for zika / dengue, improving numbers of captures around hanging or standing traps

  • the flight dynamics are assessed around the traps. a lot mosquitos attracted to the trap bur only small proportion will be captured.