Arthropods and Disease Review 2

Blattaria

Cockroach

Phthiraptera

Lice

Hemiptera

True Bugs

Coleoptera

Beetles

Siphonaptera

Fleas

Diptera

Flies and Mosquitoes

Lepidoptera

Moths and Butterflies

Hymenoptera

Ants, Bees, and Wasps

Scorpionida

Scorpions

Solpugida

Sun Spiders, Solpugids, and Camel Spiders

Acari

Mites and Ticks

Araneae

Spiders

Who demonstrated pathogen transmission by a blood-feeding arthropod and found that mosquitoes transmitted Bancroftian filiariasis?

Patrick Manson

Who implicated the cattle tick as the vector of Texas cattle fever and paved the way for the eradication of the tick and subsequently cattle fever?

Theobald Smith and F.L Kilbourne

Who demonstrated the link between mosquitoes and avian malarial parasites?

Ronald Ross

Who found the cyclical development of malarial parasites in anopheline mosquitoes in 1898?

Giovanni Grassi

Who found that fleas are the vector of the plague?

Paul Louis Simond

Who found evidence in 1948 that mosquitoes transmitted yellow fever?

Josiah Nott

Who found evidence that Aedes aegypti were the mosquitoes transmitting yellow fever?

Carlos Finlay

Who led the US Yellow Fever commission and showed that aedes aegypti were transmitting the virus in the 1900’s?

Walter Reed

Who showed that tsetse fly transmits African trypanosomiasis during blood feeding?

David Bruce

Who are in the Yellow Fever Trio

Josiah Nott, Carlos Finlay, and Walter Reed

Arthropod Characteristics

• Segmented bodies arranged into regions (tagmata)

• Have chitinous exoskeleton that must be shed

• Paired appendages are jointed

• Bilateral Segments

• Nervous system is dorsal

• Circulatory system is open and Ventral

Types of Mouthparts

1. Chewing

2. Piercing and Sucking

Blood Feeding Mouthparts:

Telemophages

Selenophages

Telemophages

Lacerate (saw) into host skin and feed on pools of blood at bite site.

Ex: Black flies, Horse flies, Deer Flies, and Biting Midges

Selenophages

Penetrate individual capillaries and feed directly on host blood

Ex: Mosquitoes, Bed bugs, Kissing bugs, Sucking lice

Sucking Lice

• Labrum highly modified to haustellum, which surrounds other mouthparts

• At the tip are teeth, which are used to anchor the mouthparts to the hosts

Flea Legs

• Hind legs modified for Jumping

• Enlarged, muscular femur

• Resilin

  • Stores energy and increases the efficiency of the hind legs

Lice Legs

• Cling tenaciously to hosts

• Modified tibia and and tarsus, tibiotarsal claw

Tick Legs

• Forelegs have enlarged claws

• Quickly grasp passing hosts and facilitate holding onto skin during feeding and mating

Rodent Mites Legs

Enlarged Legs for clasping the fur of rodent hosts

Scabies Mites

• All legs are reduced and have elongate apoteles with terminal suckers

• Move about quickly on the skin surface

Diptera Antenna

Have receptors that detect molecules emanating from the skin and in the exhaled breath of potential hosts

Diptera Antennas in Mosquitoes

• Johnston’s Organ: specialized for detecting airborne vibrations.

  • Can cue in on vibrations produced by host movements and vocalizations

Flea Antenna

• Short - flattened fits into a protective groove on the side of the head

  • Allows antenna to be retracted so its not damaged or impeding of movement.

• Compound Eye

Solenophages Antenna

• Receptors concentrated near the tip of the proboscis or rostrum

• Used to detect precise location of capillaries beneath the surface of the skin

Sensilium

• Dorsal portions of the terminal abdominal segments

• Specialized for detecting host associated cues such as vibrations and temperature gradients

Trichobothria

Common in mites and other arachnids for detecting airborne + substrate

Haller’s Organ

• Ticks

• Located on the dorsal aspect of the tarsus on first pair of legs

• Functions in detection of temperature, air movements, host odors, and other environmental cues

Epidemiology

The natural history and spread of diseases within human and animal populations

Vector-Borne Disease

Triad between arthropod vector, vertebrate host, and host + pathogen

Vector

• Arthropod responsible for parasite transmission

• They transmit the parasite, not disease

• The disease is the host’s response to the parasite

Parasite

• Any organism, including viruses, bacteria, protozoa, helminths, and arthropod that is dependent upon the host for survival.

• May or may not cause disease

When a parasite injures the host, it is called a ____ or a ______

Pathogen; disease agent

Facultative Parasite

Free-living and parasitic forms

Obligate Parasite

Totally dependent on host for survival

Ectoparasite

Live outside of the host

Endoparasite

Live inside of the host

A host carrying a/the parasite is ______

Infected

A host capable of transmitting the disease is ______

Infective

A host capable of parasitic maintenance without the clinical symptoms is a _______

Carrier

Components of Transmission Cycles

• A parasite that can multiply within both vertebrate and invertebrate host tissues

• A vertebrate host that develops a level of infection with the parasite that is infectious to a vector

• An arthropod-host or vector that acquire the parasite from the infected host and is capable of transmission

Vertebrate Host Requirements

• Accessibility

  • Must be abundant and fed upon frequently by vector

• Susceptibility

  • Must be susceptible to infection and permit development and reproduction of the parasite

• Transmissibility

  • Need suitable numbers of susceptible vectors available to become infected

Vector Requirements

• Host Selection

  • Must be abundant and feed frequently

• Infection

  • Susceptible to infection and live long enough for parasite to complete development or multiplication

• Transmission

  • Must exhibit a high probability of re-feeding on one or more susceptible hosts

Vector - Antropophagic:

likes to feed on humans

Vector - Endophilic:

Like to feed on the inside

Vector - Exophilic:

Like to feed on the outside

Vector - Zoophagic:

Likes to feed on animals (general)

Vector - Mammalophagic:

Likes to feed on mammals

Vector - Orinthophagic:

Like to feed on birds

Types of Vertical Transmission:

Transstadial, Transgenerational, and Venereal

Transstadial Transmission:

Vertical - Sequential passage of parasites acquired one life stage through the molt to the next stage

Transgenerational Transmission:

Vertical - Vertical passage of parasites by an infected parent to its offspring

Venereal Transmission:

Vertical - Passage of parasites between male and female vectors during mating.

Types of Horizontal Transmission:

Anterior and Posterior station, Mechanical, Nonviremic, Multiplicative, Developmental, and Cyclodevelopmental

Anterior Station Transmission:

Horizontal - Parasites are liberated from the mouth parts or salivary glands during blood feeding

Posterior Station Transmission:

Horizontal - Parasites remain within the gut and are transmitted via contaminated feces

Mechanical Transmission:

Horizontal - Parasite is transmitted among vertebrate without amplification or development within the vector.

Nonviremic Transmission:

Horizontal - Infectious vectors are able to transmit viruses through the host directly to concurrently feeding uninfected vectors

Multiplicative Transmission:

Horizontal - Parasite multiplies asexually within the vector and is transmitted after an incubation period

Developmental Transmission:

Horizontal - Parasite develops and metamorphoses but does not multiply within the vector

Cyclodevelopmental Transmission:

Horizontal - Parasite metamorphoses and reproduces asexually within the arthropod vector

Extrinsic Incubation Periods:

The time interval between vector infection and parasite transmission (time from infected to infective)

Intrinsic Incubation Periods:

Time from infection to the onset of symptoms or infectiousness in the vertebrate host

Anthroponosis Transmission Cycle:

Infects only humans (malaria)

Zoonosis Transmission Cycle:

Disease of animals that occasionally infects humans

Ornithonoses Transmission Cycle:

Disease of wild birds that occasionally infect humans (west nile)

Endemic Transmission Cycle:

When human cases appear consistently in time and space (geographically)

Epidemic Transmission Cycle:

An increase in the number of diagnosed human cases during a specific time period

Infection Rates

• Infection Prevalence

  • Numbers of vectors/number examined x100

• Entomological Inoculation

  • Number of potentially infective bites per unit of time

Vector Competence

Defined as the susceptibility of an arthropod species to infection with a parasite and its ability to transmit this acquired infection

Morbidity

Illness or impact on livelihood

Mortality

Death

Emerging Vector Borne Diseases

Emerging disease has a significant increase in incidence, severity or distribution in recent history.

• Demography

• Globalization of Commerce

• Anthropogenic changes

• Surveillance

• Pathogen Evolution

Taxonomy

• ~ 4,000 Species worldwide

• 70 species in the US, 24 have been introduced

Cockroach Morphology

• Cerci with 8 or more segments

• Biting-Chewing Mouthparts

• Head concealed by large pronotum

• Hind femora not enlarged

• Dorsoventrally flattened

Life History of Cockroaches

• Multiple eggs in each egg case, called ootheca

• Many eggs mean many nymphs

• Nymphs look like small versions of the adults

German Cockroach #1

• Most important domestic pest throughout the developed world

• Adults about 16mm, bronze, w/ two dark stripes on the pronotum

• Found everywhere, but likely warmth, moisture, and darkness

• Found in kitchens, pantries, bathrooms, and is nocturnal

German Cockroach #2

• Does not move between buildings readily

• Produce an ootheca with 30-50 embryos 4-8 times

• Mother carries eggs to term even if she is dead

• Eats almost anything

Brown-banded Cockroach

• Small: 13-14.5 mm w/ side to side stripes

• Found in warm and dry spots, often high up

• Confided to indoor environments of heated structures

• Development from egg to adult in about 6 months

• Females affix their ootheca to furniture

American Cockroach #1

• Large: 34 to 53cm and reddish-brown color

• Undergoes 10-13 molts over 1.5 to 2 years

• Female produces 9-10 egg cases w/ 12-16 embryos

• Lives in buildings, sewer system, tree holes, ships, and mines

American Cockroach #2

• Can move through crawl spaces of hospitals via pipe chases into other areas

• Most cosmopolitan species

• Likes it hot

Oriental Cockroach

• 25-33cm, black in color

• Development about one year

• Lives in sewers, basements, and mulch, sump pumps, and floor drains

• Likes it cool and wet

• Mobility fairly restricted, rarely seen during the daytime

Signs of Cockroaches

• Live Cockroaches

• Dead Cockroaches and their parts

• Frass (insect fecal matter)

• Egg cases

Where cockroaches live

• Anywhere in a building

• Prefer spots near water but also need food and warmth

• In cracks + Crevices where their bodies touch surfaces above and below

What cockroaches eat:

• Crumbs

• Grease

• Trash

• Cardboard glue

• Just about anything

Where Cockroaches Drink:

• Sinks

• Counters

• Pet bowls

• Sweaty pipes

• Shower Stalls

• Refrigerator drip pans and gaskets

• AC units

Public Health Importance

• Pathogen Agents

• Intermediate Hosts

Cockroach Allergies:

• One of the more significant indoor allergens of modernized societies

• Among asthmatics, about half are allergic to cockroaches

• Sneezing, runny nose, skin reaction, and eye irritation

• Severe cases include difficulty breathing or even anaphylactic shock