INTRODUCTION TO MEDICAL ENTOMOLOGY

Overview of Medical Entomology

Explain how arthropods can become ectoparasites. Give examples of these arthropods and the visible effects of ectoparasitoses.

Arthropods can directly cause disease by bloodfeeding, burrowing, crawling, and scraping.

Examples:

• Ticks - bloodsucking

• fleas -bloodsucking

• lice -bloodsucking

• Mites (Scabies mites) - burrowing

Manifestations of ectoparasitoses include reactions such as dermatoses, allergic reactions, and loss of efficiency and productivity. They can also cause weight loss and lowered milk production for cattles.

Explain how arthropods can become endoparasites. Give examples of these arthropods and the visible effects of endoparasitoses.

Arthropods can directly cause disease by invading tissues or body cavities of vertebrate hosts.

Examples

• “Chigoe” or “Chigger” flea - swelling of host tissues surrounding the feeding site

• Fly maggots - myiasis

Give examples of arthropods involved in envenomation.

Wasps, bees, and spiders

Venom are a type of _____________, which are often ________ that cause poisonous reactions in other animals.

toxin; proteins

What is delusory parasitosis?

a psychopathic condition that is manifested by a strong sense of being infested by arthropods

What is a vector?

any agent by which a pathogen is transmitted from one host to another.

The long evolutionary history of insects stretches back at least into the ____________ period

Devonian (450 mya)

Dipterans are believed to have first appeared no later than the _________ period, about 200 mya

triassic

The mosquito fossils of the Eocene epoch of the Quaternary Period (40-60 mya) is remarkably similar to the present-day ____________ species

Culex

Most entomologists believe that the __________ habit in mosquitoes had already developed by the time birds and mammals arose late in the __________Era (70-230 million years ago)

bloodsucking; Mesozoic

Before, infectious diseases are generally believed to have been caused by __________, and not microorganisms.

helminths

generally regarded to have begun the modern period of medical entomology

Patrick Manson

What is the important findings of Patrick Manson\s research?

• mosquitoes became infected with immature stages of filarial worms (microfilariae) in the process of taking a bloodmeal

• association between insects and parasites

What are the findings of Theobald Smith and F.L. Kilbourne in their research?

demonstrated the transmission of Texas cattle fever (piroplasmosis) by the cattle tick, Boophilus annulatus.

• Revealed that pathogenic microorganisms can be transferred from arthropods to vertebrate animals

• Pathogenic microorganisms can be transferred from adult female arthropod to its progeny through transovarial transmission, wherein eggs are infected

Who hypothesized that the yellow fever mosquito, now known as Aedes aegypti, was the vector of the disease?

Carlos Finlay

Who proved Finlay’s hypothesis?

Major Walter Reed, leader of the Yellow Fever Commission

Scientists of the Yellow Fever Commission that participated in a series of experiments that demonstrated conclusively that Ae. aegypti mosquitoes could transmit the virus from infected patients in hospitals to uninfected volunteers, and that the disease could not be transmitted through direct contact with contaminated food or bedding, nor with infected patients.

James Carroll, A. Agramonte, and Jesse Lazear

lost his life by permitting infected mosquitoes to feed upon him

Jesse Lazear

discovered that trypanosome parasites (later named Trypanosoma brucei in his honor) present in the blood of cattle caused. nagana, a fatal disease of cattle and horses

David Bruce

demonstrated that the parasites were transmitted by flies in the genus Glossina (tsetse)

David Bruce

reported that tsetse transmitted the related parasite T. gambiense to humans, resulting in African sleeping sickness.

David Bruce and David Nabarro

became the first to observe malarial parasites in the blood of infected patients

Charles Laveran in 1894

observed the developing malarial parasites in mosquitoes that he characterized as "dapple-winged."

Ronald Ross in 1897

discovered that Culex mosquitoes transmitted parasites causing bird malaria

Ronald Ross in 1898

demonstrated the complete developmental cycle of malarial parasites in Anopheles mosquitoes

Battista Grassi in 1898

confirmed that only anopheline mosquitoes transmitted human malarial parasites

Malcom Watson in Malaya and by Sir Rickard Christophers in India

their discoveries laid the basis for the concept of vector competence

Malcom Watson in Malaya and by Sir Rickard Christophers in India

__________made the significant discovery in Beruit in 1902 that mosquitoes were the vectors of the then unknown organism causing dengue

H. Graham

Investigated that fleas were vectors of plague

W.B. Liston and D.B.Verjbitski

A Brazilian parasitologist that discovered a disease prevalent in South America was caused by a trypanosome parasite he named Trypanosoma cruzi.

Carlos Chagas

In 1908, ___________reported that the triatomid bug Panstrongylus megistus transmitted these trypanosome parasites, causing the disease now called ____________ disease

Carlos Chagas; Chagas

In 1926, ____________discovered that black flies (Simuliidae) vectored the parasite causing onchocerciasis, or river blindness

D.B. Blacklock

____________ and ______________conducted their pioneering research in the Yakima Valley of Washington that led to the understanding of the basic ecology of western equine encephalomyelitis and St. Louis encephalitis

William McD. Hammon and William C. Reeves

• demonstrated that the mosquito Culex tarsalis, which feeds mainly on birds, was the primary vector of the viruses causing both diseases

The decade of the __________ saw the isolation and identification of the causal agents of Lyme borreliosis and ehrlichiosis

1980s

What is the main problem of solving diseases in medical entomology nowadays?

solutions to problems in medical entomology often have been sought in a relatively vertical, single-objective framework

Different stages of larvae are referred to as the ______________

instars

___________ is defined as the long term host of the pathogen

reservoir

What is the generalized life cycle of a holometabolous insect?

egg, larvae, pupae, adult

What is the generalized life cycle of a hemimetabolous insect?

egg, nymph, adult or imago

______________ depends on the pathogenic microorganism’s ability to replicate and invade the insect’s hemolymph, which can then be transferred to its salivary glands.

vector competence

Evolutionarily speaking, being a vector may be considered as a ____________ trait

homoplastic

Why insects have no capability of spreading other diseases like COVID?

vector competence

Can bed bugs be considered as vectors?

No, because of low vector competence despite being morphologically and functionally similar to usual vectors

The three types of transmission are:

vertical, horizontal, transstadial

What does transstadial transmission means?

e.g. nymph to nymph, larvae to larvae transmissions

Differentiate extrinsic and intrinsic incubation periods