ENT104 - Medical Entomology (L25)

Certain insects are _____ of major and minor diseases

Vectors

What is medical entomology?

The study of the impact of insects (and other arthropods) on human physical and mental health

What is the primary motivation behind medical entomology?

Disease

The study of ________ is always critical to medical entomology

Behavior

What aspects of insect behavior are important in medical entomology?

What attracts the insect to the host (humans)?

What other hosts are there in nature?

What does the vector need from nature?

What is the basic lifestyle of the vector?

What is the classification of infectious diseases based on?

Reproductive rate of infection (RRI)

What is RRI?

Reproductive rate of infection

Numerical value

RRI > 1 = population growth of infection

RRI < 1 = population decline of infection

__________ have RRI > 1 in humans, < 1 in animals (meaning they are primarily human diseases)

Anthroponoses

__________ have RRI > 1 in animals, < 1 in humans (meaning they are primarily animal diseases)

Zoonoses

What is the disadvantage of classifying infectious diseases by RRI of pathogens?

RRI is not informative for the prevalence or severity of diseases

Why do researchers use RRI to classify infectious diseases?

RRI is the biological way of classifying pathogens based on lifecycle, which medical entomologists use to understand and manipulate vectors

RRI = emphasis on basic biology of vectors

What are anthroponoses?

Human diseases that grow and thrive with humans as the major host

What are some examples of anthroponoses?

Malaria, Dengue, Elephantiasis

(True/False)

Anthroponoses can be spread to other animals

True

What are zoonoses?

Primarily animal diseases that spill over into human populations

Pathogens cannot thrive with humans as major hosts (humans are not good hosts for zoonoses)

What are some examples of zoonoses?

Lyme disease, West Nile virus

What is biological transmission in insect vectors?

When the pathogen insects and grows inside both the insect (vector) and the host

What are the two ways that insects act as vectors?

Mechanical transmission

Biological transmission

What is mechanical transmission in insect vectors?

When the insect (vector) moves the pathogen onto its body and transports it to a host

How do houseflies mechanically transmit pathogens?

House flies walk over and feed on sewage, then walk on human food and regurgitate

How do insects biologically transmit pathogens?

Insect feeds on host and ingests pathogen

Pathogen multiplies inside insect (vector)

Pathogen moves into part of vector's body where it can most easily be transmitted to the next host (salivary glands, end of digestive tract)

Pathogen changes vector behavior to make it hungrier, and thus more likely to find a new host

Pathogen infects new host when the vector feeds

What are some major mosquito diseases?

Malaria

Dengue

Yellow fever

West Nile

Zika

Chikungunya

Dengue, Yellow fever, West Nile, Zika, and Chikungunya are all examples of ______

Viruses

Mosquito Diseases

(True/False)

Malaria is caused by a virus

False

Malaria is caused by a protist

What are the major symptoms of malaria?

Cyclical fever with intense chills and sweating

Pooling/clotting of blood in organs (including brain)

How is malaria controlled?

Vector control through pesticides, biocontrol, and prevention of breeding habitats (water)

Interference with mosquito biology (releasing GM mosquitoes)

What are GM mosquitoes?

Genetically Modified mosquitoes that are sterile and diseased to control wild mosquito populations

How did bednets cause mosquitoes to undergo behavioral evolution?

Bednets prevent mosquitoes from feeding at night

Bednets thus cause intense natural selection in favor of mosquitoes that feed during the day

Mosquito behavior evolves from night-feeding to day-feeding

How do mosquitoes undermine efforts at malaria control?

By undergoing rapid behavioral evolution

Altering their behavior (feeding times) to avoid preventive measures (bednets)

What is the insect vector of Leishmaniasis?

Sandflies (Psychodids)

Leishmaniasis is a (Zoonosis/Anthroponosis)

Zoonosis

What are the 3 main forms of leishmaniasis?

Cutaneous (skin)

Mucocutaneous (mouth/nose)

Visceral (internal organs)

What is the most common form of leishmaniasis?

Cutaneous

What is the most severe form of leishmaniasis?

Visceral

What is leishmaniasis most associated with?

Compromised immune systems due to poverty or HIV

What animals act as leishmaniasis reservoirs?

Rodents

e.g. gerbils, ground squirrels, hyraxes, opossums, sloths, marmosets, ocelots

What pathogen causes leishmaniasis?

Leishmania (protist)

What is the insect vector of sleeping sickness?

Tsetse fly

What pathogen causes sleeping sickness?

Trypanosoma brucei (Trypanosome, protist)

What are the symptoms of sleeping sickness?

Fever and flu-like symptoms

When is sleeping sickness most easily treated?

Early on

Treatment in second phase of sleeping sickness is more dangerous and less effective

(True/False)

Sleeping sickness is often a fatal disease

True

What is the insect vector of Chagas disease?

Kissing bug (Triatoma bug)

What is the main initial symptom of Chagas disease?

Swelling around one eye

How does Chagas disease cause death?

The pathogen inhabits the heart and digestive muscles, causing sudden death due to heart failure

How is the pathogen of Chagas disease transmitted from insect to human?

Kissing bug sucks blood and defecates on skin (excrement contains the pathogen)

Scratching the bite causes the skin to break and allows the pathogen to get inside

How did Triatoma bugs become primary vectors of Chagas disease?

Triatoma bugs adapted to living in human shelters in high numbers (easier access to blood)