Week 3 Role of mosquito II Dengue Disease transmission / Effect of temperature Flashcards
Define:
a) Mechanical Transmission b) Biological Transmission
a) Physical transfer of a pathogen to a host
b) Replication and/or development must occur in the vector prior to transmission
Explain Cyclodevelopmental transmission
Agent must undergo developmental changes in vector prior to transmission
Agent does NOT replicate
Example: filarial parasites develop within the mosquito
Explain Propagative transmission
Agent must replicate in the vector prior to transmission
Additional development does not occu
Example: Yersinia pestis replicates but does not undergo development in fleas
Explain Cyclopropagative transmssion
Agent undergoes both replication and development in the vector prior to transmission
Example: Plasmodium species replicate and undergo several stages of development in the mosquito
Define : Vector competence
Ability of a given vector to acquire, maintain, and transmit infectious agents
Many arthropod-borne diseases are highly species specific
Important mosquito borne diseases
Malaria
Dengue
Japaneese encephalitis
West Nile encephalitis
a) Where are common places Dengue occurs?
b) Who are the primary hosts?
a) Occurs in Tropical and sub-tropical regions
~2.5 billion at risk for infection
50-100 million infections/year
Endemic in >100 countries
b) Humans are the primary host
Mosquitos that transmits Dengue and facts about them
1- Ades aegypti mosquito Adapted to urban communities Prefers to feed on humans Prefers to feed indoors Often feeds on multiple sources Feeds during the day 2 hours after dawn and before sunset Breeds in containers Sufficient viremia in humans to infect mosquito
2- Ades alpopictus Asian tiger mosquito Less adapted to urban environment Borders vegetative areas Can survive colder climate Very aggressive, daytime feeder Will feed on humans and other mammals
What cell types get infected by Dengue?
Dendritic cells Monocytes/macrophages B-cells Endothelial cells Hepatocytes
What are the 3 variations of Dengue?
Dengue Fever
Dengue Hemorrhagic Fever (DHF)
Dengue Shock Syndrome (DSS)
What are some of the symptoms of Dengue fever?
Why is it known as “ break bone fever” ?
High Fever Leukopenia Thrombocytopenia Arthralgia Myalgia Petechial rash
The person infected by Dengue experiences severe pain all over the body, often described as, as bad as pain generated from a bone fracture, but all over the body accompanied by very painful headaches.
What are the symptoms of Dengue Hemorrhagic Fever ?
Abdominal pain Cyanosis Bleeding gums Increased vascular permeability Vascular leakage Hemorrhaging in GI tract
What are the symptoms of Dengue Shock Syndrome ?
Decreased blood pressure
Narrow pulse pressure
Rapid pulse
What are the 4 Dengue serotypes?
DEN-1
DEN-2
DEN-3
DEN-4
History of Dengue
First reports around 1770 in Asia, Africa, and North America
Periodic epidemics re-occurred every 10-40 years
Current pandemic began in SE Asia during WWII and was connected with movement of military equipment and water storage facilities
Epidemics increased in SE Asia since WWII where
multiple serotypes were present
DEN3 was most common, there were 900,000 cases of DHF and DSS in Taiwan from 1958-90
Since 1980 epidemics in East Africa have increased
All four serotypes were detected but little severe disease emerged.
In West Africa there were cycles of Dengue in monkeys.
Later on the disease spread to spread to Pacific Islands
