L2 (gem): Intro to vectors

Physical attack by arthropods

Biting, stinging, and the release of products which sensitise the individual, resulting in inflammation

Tick bites

Painful bites that induce local inflammation and cause subcutaneous haemorrhage due to an anticoagulant in their saliva

Mosquito bites

Cause itchy lesions in sensitised persons which may progress to chronic ulcers, and attack repeatedly at rates of up to 280 per minute in extreme cases

Black flies

A seasonal menace occurring in enormous numbers whose bites around the eye may trigger allergic swelling of the eyelids

House dust mites

Ectoparasites that cause severe dermatitis and release allergenic products that trigger asthma in sensitised individuals

Scabies mites

Ectoparasites that burrow into the skin causing papules and a generalised rash, which are a significant problem in rural Indigenous communities

Vector

An organism housing infectious agents and transmitting them from one host to another, commonly acting as a host itself

Biological transmission

Transmission of infectious pathogenic organisms that replicate in the arthropod, requiring an extrinsic incubation period and necessary for pathogen survival

Mechanical transmission

Transmission where a vector picks up the infectious agent on its body parts without ingestion and physically transfers it, which is not necessary for pathogen survival

Horizontal transmission

Biological transmission of a pathogen by the bite of a competent vector

Vertical transmission

Transovarial transmission of a pathogen from a vector to its offspring

Host

An organism supporting an infectious agent in or on its own body, and often to its own detriment

Vertebrate reservoir

The natural host species, such as animals or birds, that acts as a reservoir of the infectious agent for the vector species

Incidental host

A host, such as humans in many vector-borne diseases, whose infection is not usually important in the maintenance of the infectious agent in nature

Zoonotic transmission

A transmission cycle of an infectious agent involving an arthropod vector, a vertebrate reservoir, and humans

Anthroponotic transmission

A transmission cycle of an infectious agent involving only an arthropod vector and humans

Insecta

A class of arthropod vectors that possess wings, antennae, a thorax with 3 pairs of legs, and a segmented abdomen, such as mosquitoes, flies, and fleas

Arachnida

A class of arthropod vectors lacking wings and antennae that undergo incomplete metamorphosis to develop 4 pairs of legs as adults, such as ticks and mites

Myxomatosis

A viral disease of rabbits that was mechanically transferred by mosquitoes and fleas from infectious surface lesions

Yersinia pestis

The plague bacterium that proliferates in and blocks the flea's pharynx, causing the bacteria to be regurgitated when the flea attempts to feed

Tissue-replicating biological transmission

Pathogens enter during a blood meal, replicate in tissues, and infective forms invade the vector's mouth parts, bursting through the cuticle during feeding

Leishmania transmission

The protozoan parasite undergoes its development cycle in the gut of a sand fly, blocks its mouth parts forcing more frequent bites, and is injected into new hosts

Salivary gland replication

The most efficient biological transmission mechanism where agents replicate in the vector's salivary glands for easy entry into the host's blood, such as in malaria and dengue

Female vector requirement

Only female mosquitoes, phlebotomine sandflies, and biting midges transmit pathogens because they require the protein from a blood meal to develop their eggs

Extrinsic incubation

The time it takes for a virus to infect a mosquito's midgut and eventually travel to the salivary glands, usually 8 to 10 days for dengue

Intrinsic incubation

The time it takes for a human to develop symptoms after being infected by a vector, usually 4 to 7 days for dengue

Justinian Plague

The first plague pandemic in 541 AD which caused over 100 million deaths and affected much of the Mediterranean basin

Black Death

The second plague pandemic starting in 1347 that killed an estimated 60 percent of the European population and sped up economic and technical modernizations

Plague impact on human genetics

The plague created a genetic bottleneck and altered human evolution by allowing only those with natural resistance to survive

Modern plague treatment

Antibiotics such as tetracycline, streptomycin, and chloramphenicol are very effective, although resistant strains are emerging

Malaria historical impact

It killed Alexander the Great, stopped the armies of Attila the Hun, caused one million cases in the US civil war, and was the strongest selective pressure on the human genome

Malaria genetic resistance

Resistance evolved in the human genome due to hemoglobin disorders such as thalassemias and sickle cell anemia

Zika virus

First identified in 1947 in Ugandan monkeys, it causes mild symptoms but was declared a public health emergency in 2016 due to an association with congenital microcephaly

Zika transmission routes

Primarily transmitted by Aedes mosquitoes, but also via mother-to-fetus transmission, sexual transmission, and blood transfusion

Climate change impact on vectors

Projected to increase mosquito habitats globally and expand the number of months per year when disease transmission is possible