Med Vet Entomology Midterm

Entomology

the study of insect→ segmented animals (insects, anthropoids)

from the greek “entomb” meaning “cut up or divided into segments”

Idiosoma (ticks)

internally segmented - fused together

Basic Characteristics of Anthropoids

anthropods: animals that have articulated legs

external skeleton: provides support + protection for the animals 

what are the types of problems caused by anthropods

• annoyance/nuisance

• toxins and venoms

• disease: destruction of host tissues (ie screwworms)

  • myiasis→done by fly larvae

• vector-borne diseases

• food contamination (disease)

• allgeric reactions

• physiological stress

  • fear 

  • delusional disorders (morgellons disease)

morgellons disease

belief that the skin is infected by bugs (skin lesions)

myisasis

parasitic infestation of the body of a live animal by fly larvae that grow inside the host while feeding on it tissue

toxins

chemicals that interfere with normal physiological structures

venoms

poisons injected by specialized morphological structures

what is the most important order

diperta

what is special about the Chiggers/Trombidiformes in Class Arachinida?

only parasitic through their larvae stage

Class arachnida

not all arachnids are parasitic through their entire life

the most dangerous animal

mosquitoes 

• 725,00 people a year

• malaria alone accounts for 600,000

What did Robert Koch do?

• Koch’s postulates (1884)

• germ theory od disease versus Miasma theory

what did Patrick Manson do?

• founder of the tropical medicine field

• role of mosquitoes in human elephantiasis (1877)

  • cased by a nematode (filiara) vector-mosquito

what did theobald smile do?

• discover the causative agent of Texas cattle fever was vectored by the cattle tick (1883)

  • caused by a unicellular parasitic babesia

what did Ronald ross do?

• described the life cycle of the parasites of malaria (1897)

what did Walter Redd do?

• demonstrated the role of Aedes mosquitoes in the transmission of yellow fever (1900)

what did William Burgdorfer, Alan Barbour, and Jorge L. Benach do?

• discovery of the agent of Lyme disease (1982)

Koch’s Postulates

way of proving that the pathogen is responsible for causing that disease in an animal

Major Human Vector Borne Disease

what is a vector-borne disease?

a disease transmitted by a vector

what is a vector?

an organism, typically a blood feeding arthropod, that transmits a pathogen from an infected host to a naive host

Mechanical vector transmission

picks up an infectious agent on the outside of its body and transmits it in a passive manner

biological vector transmission

transmission with a. vector carries pathogen to a host

• propagative transmission (plague)

• cyclodevelmental transmission (lymphatic filariasis)

• cyclpropagative transmission (malaria)

propagative transmission (plague)

occurs when the organism ingested with the blood meal undergoes simple multiplication in the vector

cyclodevelopmental transmission (lymphatic filariasis)

the cause organism undergoes developmental changes from one stage to another but does not multiply in the vector 

cyclopropagative transmission (malaria) 

the agent reproduces and undergoes cyclical changes in the vector 

Putative vector must

1. associate and feed on the reservoir/s and its seasonality should coincide with the incidence of vertebrate infection

2. be commonly found infected with the disease agent in question (in “field collections)

3. be shown to become infected experimentally 

4. be shown to be capable of transmitted the disease to an uninfected host (under controlled conditions)

vector competence

• refers to the ability of the arthropods to acquire, maintain and transmit a pathogen 

  • needs to survive in the vector species

  • vector needs to be able of maintaining the pathogen for biological transmission to happen

Vectorial capacity

is an equation that accounts for the major factors of pathogen transmission by mosquitoes and is defined as the average number of new vertebrate infections per day resulting from an initial index case

• the ratio of mosquitos to human (m)

• human biting rate (a)

• mosquitoes survival through one day (p)

  • the time that pathogen require to go from the mid gut to the salivary glands

• pathogen latent period (n)

1. number of mosquitoes

2. survivorship

3. feeding frequency and type

   1. only female require a blood means →needs energy to produce eggs

   2. males do not bite

bridge vector

organism typically a biting anthropod, that transmits a pathogen from one animal host to another human

enzootic vector

organism typically a biting arthropod that transmits a pathogen from one animal host to another animals

Risk Probability of human infection

Risk = A x Fm X P x Cv

• A = vector abundance

• Fm = fraction of human blood meals

• P = infection prevalence in the vector

• Cv = fraction of infected mosquitoes that will transmit the disease by a subsequent bite = vector competence

endemic 

refers to a disease regularly occurring in people within an area or community

• transmission is stable → does not change over time 

epidemic

is the rapid spread of disease to a large number of patients among a given population within an area in a short time

Pandemic

is an epidemic of an infectious disease that has spread across a large region of instance, multiple continents or worldwide, affecting a substantial number of individuals 

enzootic

refers to a disease involving non-human animals in a specific geographical area where the disease is constantly present at a low incidence

Epizootic

is the rapid spread of disease to a large number of patients among a given population within an area in a short time

culex

gnat

mosquito

little fly

Morphological differences between anopheline and culicinae 

Anopheles Gambian complex (anthrophophilic)

• malaria

• human filariasis

-endophilic

-endophagic

Anopheles arabiensis

drier climates

culex pipiens

close group of domestic and peridomestic species

• west Nile

• St. Louis encephalitis

• bird malaria

temperate climates: Cx. pipiens form molestus (underground, autogenous) tropical and subtropical Cx quinquefasciatus

Aedes spp. 

• denge

• chikungunya

• zika

• yellow fever

Aedes aegypti

• yellow fever mosquito

• feral form (formosus) aegypti Vs domestic aegypti

Aedes albopictus (asian tiger mosquito)

• cold hardy egg-diapausing strain is invasive

anthropophilic

• referring or seeking a human host over another animal.

• supplement

• used to describe parasites that prefer or seek human as host rather than other animals

endophilic

• is a mosquito that tends to inhabit/rest indoors

endophagic

is a mosquito that feeds indoors

Mosquito Eggs

Anaopheles: lateral floats → eggs laid individually on water

Aedes: No floats → eggs laid individually beside water

Culex: No Floates → eggs laid in rafts on water 

Mosquito Larvae

Anapheles: No siphon → rest parallel to water surface

Aedes: siphon → rest at angle to water surface

Culex: siphon → rest at angle to water surface

autogenous

a blood feeding species that can lay eggs before feeding

Morphology Pupa

• breathing trumpets

• not possible to determine genus at this stage 

Area for Aedes species

Aedes aegypti: tropical

• has permanent temperate populations

Aedes albopictus: tropical and temperate

• some can undergo photoperiodic-induced diapause to survive cold winters

Aedes j. japonicus: temperate

indroduced mosquitoes. to Hawaii

bird malaria was introduced in Hawaii, it harmed the native species because their immune system does not have a history of fighting of the pathogen 

What group is no longer alive?

trilobites is not longer present→ extinct.

-they are the one group

Phylum Arthropoda

is the largest in the animal kingdom

• Characteristics:

  • exoskeleton (hardened plates with flexible joints)

  • articulated appendages

  • segmentation

  • open circulatory system

    • hemolymph

    • specialized excretory structures, Malpighian tubules →collect the product of metabolic  waste

What is the exoskeleton made of?

predominantly of chitin (a nitrogenous polysaccharide = polymer of n-acetyl-glucosamine)

Exoskeleton

is an external skeletons that supports and protects an animals body

1. protection against predator

2. support: it provides an attachment framework for muscles

3. protects against desiccation

• all the muscles are anchored to the exoskeleton 

Limitations of Exoskeleton

• Ecdysis

• the cuticle

• empty exoskeleton

• after molting, the cuticle is soft and it hardens and darkens

• cuticle grows via fluid or air

• repairs damaged tissue 

  • can regenerate a missing appendage or tissue

Ecdysis

is the molting of the cuticle in many invertebrates 

the cuticle

is an inelastic ( can’t extend) exoskeleton

exuvia/exuviae

empty exoskeleton

tanning process

the period it takes for the cuticle to harden and darken

• during the process they are executable to predation

pore canals

ecytoplas’s extension of the epidermal cells that retract after molting, forming the canals

trichogen cell

produces cells to make hair

gland cell

expands themselves to produce the cells to produce cuticule

epicuticle

thin and made of 4 layers:

• cuticulin layer 

• polyphenol layer (involving in tanning)

• wax layer

  • importantly prevents the lost of water

• cement layer

procuticle

mix of protein and chitin (nitrogenous poly saccharide = polymer of n-acetyl-glucosamine)

what happens after molting?

the procutcle differentiates into the endocuticle (soft and flexible) and exocuticle (hardness and rigidity/sclerotin)

Diatomaceous earth

is a fossilized remains of diatoms, a type of hard shelled microalgae

• removes the wax layer →result lost pf water and they will die rapidly

hemolymph

has the same functions of he vertebrate blood and lymph combined (except that oxygen reaches cells through the tracheal system - CO2 dissolves and is excreted by the Malpighian tubes)

• also acts as a physical force (hydraulic) to extend proboscis reproductive organs, molt

• small arthropods might not need extra parts to move around hemolymph 

venture diaphragm

helps mix the products of the hemolymph

heart portion of dorsal aorta & dorsal diaphragm Ostia

contract to help move the hemolymph in bigger arthropods

aorta

helps move around the waste to get out

hemocytes

cellular components (multifunctional cells)

• would repair

• detoxification

• immunity

mites muscle system

primitive

• they can’t extend their muscles they use their circulatory 

• use the hemolymph to shoot the part they want to extend

what part might microscopic insects lack from the respiratory system?

treacha system

• change of oxygen is done through infusion system

taenidia

makes the structure stable

tracheole

allows oxygen ti reach all of the cell in their body

ametabola

• most primitive wingless insects

  • all have driven from this one

• there is almost no change in form throughout growth to the adult 

Hemimetabolous

• incomplete metamorphosis

• distinct stages : the egg, nymph, and the adult or imago

  • no pupal stage

• the nymph has a thin exoskeleton and resembles he adult stage but lacks sings and functional reproductive organs 

Holometabolous

• complete metamorphosis

• prevents larvae from competing with a adults because they inhabit different ecological niches

• larval traits maximize feeding, growth, and development

• adult traits enable  dispersal, mating and egg-laying 

Morphological adaptation of parasitic arthropods: body, shape, wings

• modify body parts to facilitate movement on the host

• ectoparasites with a long term close association with host: dorsoventral (bedbug, ticks)

  • lateral flattening (fleas)

• wings (tabards, lice, louse flies) →not pessary to parasite insects

Morphological adaptations of parasitic arthropods: mouthparts

• adapted to feed on blood, hemolymph, skin secretions (moth part adapted for piercing) or skin, feathers, skin scales (chewing mouthparts)

• temophages (pool feeders) → horse flies

• solenphages (capillary feeders) → mosquitoes 

• mouthparts can change during the stages of growth

myiasis

is the parasitic infestation of the body of a live animal by fly larvae (maggots) that grow inside the host while feeding on its tissue

• animal has to be alive

what are the two main fly families that can cause myiasis

• Calliphoridae (blow flies)

  • have free metallic exoskeleton

• Muscidae (house flies, stable flies)

How do they cause myiasis?

• flies are most commonly attracted to open wounds and urine or feces soaked fur

• some species (botfly, blowfly, and screw fly) can create an infestation on unbroken skin

• vector mediated

  • trap a sucking vector and they eggs on it, the eggs attracted to the vector will lay on the host and it can get into the tissue during a vector blood meal

Psudomyiasis or accidental myiasis

caused by free-living flies that can become parasitic under rare conditions

• ex: ingestion of food contaminated with eggs or larvae

  • cannot develop in the host

facultative myiasis

involves larvae that can be either free-living, detritivores or parasites→opportunistic flies

• ex: maggots of blow flies which normally feed on carrion

primary myiasis

involve those species that can initiate myiasis

secondary myiasis

involve species that cannot imitate by continue myiasis

• may feed on carrion 

tertiary myiasis

species that join primary and secondary species at or right before host death

• free living species that feed on carrion 

obligatory myiasis

• maggots are always parasitic

• require a living host for their developent

• Ex: screwworms and bot flies

Temporary myiasis

• intermittent contact between a fly larva and its host 

  • nestling maggots and floor maggots

• maggots get on the host → feed on the host→ leave the host→ come back when hungry 

incidental myiasis

parasitism of an atypical host by obligate myiasis producing fly

What animals did Philornis drowns fly invade in the early 1960s?

finches in the Galapagos islands

What do fly larvae get out of myiasis?

• exploiting a rich protein source by larva for development

• for adults → reproduction

• accumulate resources early on

  • dietary proteins are required for growth, development and egg production

  • proteins can be obtained by larvae, adults or both 

Myiasis in Humans

• relatively uncommon

• occurs seasonally and sporadically in temperate regions and during the wet seasons in the tropics

  • In South America several hundred human cases by the New World screworms (cochliomyia hominivorax → perfers humans) have been reported

  • some Africans countries show a high prevalence of furuncular myiasis by cordylobia anthropophaga → eats humans

• most human cases of facultative or obligatory myiasis are only temporary or are aborted because humans are not suitable host

• maggots do not complete their development in people because they are interrupted by self-grooming or medical intervention