General Vector Biology Flashcards
- What are the possible medical problems caused by arthropods?
o Annoyance (they bite, are abundant, and small)
o Allergic reactions (stings and bites can cause allergic reactions, or contact allergies, or even respiratory allergies from debris)
o Toxins and venom (bites and stings)
o Invasion of host tissue
o Disease transmission
- What is an example of a medical problem caused by arthropods where the host tissue is invaded?
o One such case is myiasis where the host tissue (stomach, throat, nose, eye) is invaded by fly larvae
- What is the leading cause of morbidity and mortality in the developing world?
o Malaria. The major demographic affected by malaria are women and children.
o 2.2 billion individuals are at risk for malaria.
- The Zika virus was first isolated in 1947, but it wasn’t until 2016 when an outbreak occurred, why?
o Over the course of evolution, genetic changes resulted in a variation that had increased transmissibility
o In the past, it is hypothesized that zika did appear, but only in small areas and it might have been misclassified
- What is the “perfect storm”?
o As with many viruses, an outbreak is facilitated by global demographic, social and technological changes, urbanization, globalization, and a lack of proper mosquito control in urban areas resulting in an increase in the transmission and spread of viruses through mosquitos as all of the categories align
- Why is Sir Patrick Manson denoted as the “Father of Tropical Medicine”?
o Patrick Manson was the first to demonstrate pathogen transmission by a blood-feeding arthropod. In 1877, he demonstrated that mosquitos can be a vector of filarial worm. Then in 1894, Sir Manson announced the mosquito-malaria hypothesis. This discovery sparked the modern period of medical entomology.
o Patrick Manson is one of the most significant figures in parasitic diseases
- T/F. Patick Manson discovered that malaria is a parasite that is transmitted from arthropod to human.
o False, Patrick Manson just discovered that mosquitos could transmit malaria, but is was Dr. Alphonse Laveran in 1880 who discovered that malaria was caused by a protozoan parasite
- What was the significance of Major Walter Reed’s discovery of the transmission of yellow fever through Ae. Aegypti mosquitos?
o This discovery showed that yellow fever was not transmitted through direct contact and that ae. aegypti is required as a vector for yellow fever
- What is the goal of classification of organisms?
o To arrange living organisms into groups based on their similarities and differences. Classification is based on 8 levels of organization
o Living organisms are placed into specialized groups based on their similarities in structure, origin, molecular composition, etc.
- What differentiates one organisms from another when scientist discuss living organisms?
o Binomial nomenclature, by naming an organism based on its genus and species name using two terms to give a unique name
- What is the key difference between classification and binomial nomenclature?
o Although both help differentiate species, classification is the organization of living organisms based on their similarities and differences, while binomial nomenclature is just the unique naming of the organism.
- What is the hierarchy of biological classification?
o Kingdom
o Phylum
o Class
o Order
o Family
o Genus
o Species
- What does it mean when an organism is classified under the phylum “Arthropoda”?
o Joint foot
- What are the general features of arthropods?
o Exoskeleton
o Jointed appendages (think of this as their elbows)
o Segmented body
o Ventral nerve cord
o Dorsal vessel
o Bilaterally symmetrical (meaning the left half is symmetrical to the right)
- How is the dorsal vessel similar or different from the heart?
o The dorsal vessel is like a blood vessel that is the heart of an insect. This vessel runs dorsally, meaning along the back of the insect. Instead of blood, the insect has hemolymph that circulates through the dorsal vessel, but instead of the primary purpose to carry blood, the hemolymph carries nutrients across the body of the insect.
o The dorsal vessel is the heart equivalent of insects
- What kind of eye do most arthropods have?
o Compound eyes and one to several simple eyes or ocelli
- What is the biological advantage of having compound eyes vs. simple eyes?
o Compound eyes are like many lens that creates a mosaic for the arthropod. This enables arthropods to quickly detect movement.
o Simple eyes are like humans where the eye is just a single lens. Simple eyes focus more on light intensity changes rather than movement
o Structure determines function
- What is the body cavity of most arthropods?
o Hemocoel, meaning an open cavity or a loosely filled space with tissue, sinuses, and blood
o The hemocoel has flowing hemolymph, the circulatory fluid
o The hemocoel functions as a circulatory system
- What is the arthropod equivalent of a spinal cord?
o The ventral nerve cord that takes signals from the brain and transmits it to the rest of the body
- What is the significance of having an open circulatory system that distinguishes the role of the spinal cord from the ventral nerve cord?
o The open circulatory system allows for nutrients to freely pass through the arthropod, allowing the insect to function even when decapitated. Brain input is not required.
- What is the common name for the chilopoda class?
o Centipedes, the name comes from the Greek kheilos lip + pous foot, meaning that the first pair of feet is modified to look like jaws
- What are the common characteristics of the chilopoda class?
o Dorso-ventrally flattened
o Single pair of antennas
o One pair of legs per segment
o Two pairs of maxillae (jaws) on the foot used to hold food for chewing
o Carnivores
o The first segment of the body has a pair of poison claws called maxillipeds
o Females lay eggs in carefully guarded nests
- Chilopoda have a pair of maxillae on the head to hold food and a pair of poison claws (maxilliped). From that information, what can you deduce that chilopoda eat?
o Centipedes are most likely carnivores that will hold food and munch on it. The jaw-like claws provide a clue that some kind of chewing is going on.
- What are Diplopoda class?
o Millipedes. Diploos means double and pous pod- meas foot. Millipedes now have two pairs of legs per body segment.
- What are the characteristics of the Diplopoda class?
o Round body
o Two pairs of legs per segment
o Scavengers or herbivores
o Lack poisonous fangs
o Do not bite
o Discourage predators by rolling into a defensive ball and emit poisonous or foul-smelling substances
o Females lay eggs in carefully guarded nests
- Diplopoda do not have poisonous fangs like the centipedes and they do not bite. From these characteristics, what can you deduce about the diet of Diplopoda?
o Herbivores, no need for chewing and munching on flesh
- What are some key differences between the class Chilopoda and Diplopoda?
o Just like the name entails, millipedes have two pairs of legs per body segment while centipedes only have one
o Centipedes are carnivores that need organs that can chew on other organisms, as well as poison, while millipedes do not have biting fangs and are herbivores.
- What is found in the Arachnida class?
o Ticks, mites, scorpions, spiders
- What are the common characteristics of the Arachnida class?
o Two body regions, a cephalothorax and an abdomen
o No antenna
o Has 4 pairs of walking legs
o A single pair of claws or fangs known as chelicera that often contain venom
o A single pair of pedipalps (small antenna like structures (think fangs on a spider)) used for feeding, sensing, and transferring sperm
o The appendages on the abdomen are either missing or modified
- What is a cephalothorax?
o Fused head and thorax
- What is an example of an appendage on an Arachnida that is modified?
o Spiders have spinnerets instead that spin webs
- Will you find wings on Arachnida?
no
- What will be found in the Insecta class?
o Insects
- What are the common characteristics of the Insecta class?
o The body has three distinct regions, a head, thorax, and abdomen
o A single pair of antennas on the head
o The mouthparts are adapted for different types of feeding
o 0 to 2 pairs of wings
o Thorax has three pairs of legs, and you will not find an appendage for locomotion on the abdomen (butt)
- What is the purpose of the head?
o The head takes in sensory information through organs such as the compound eyes, mouthparts, and the antenna
- What is the purpose of the thorax?
o Movement, through the wings and/or legs
- What is the purpose of the abdomen?
- What is the purpose of the gnathosoma?
o This is the mouth and feeding parts found on mites and ticks
o Therefore, one can deduce that the purpose of the gnathosoma is for feeding and attachment
- What is the purpose of the idosoma?
o This is the area of the mite that contains legs, and what is needed for digestion and reproduction
- What is the general purpose of legs?
o Movement and host location/identification
- How can legs play a role in host identification?
o Some archaea cannot attach to certain hosts because of the way their legs are designed. Think attaching to the feather of birds or the leg hairs of a human
- Why is body shape important in ectoparasites?
o Ectoparasites are parasites that live outside of a host, like a flea. Because the parasite is exposed to so much external environment, shape becomes very important
- What is the purpose of body shape in ectoparasites?
o To facilitate in movement onto the host or to hide in tight spaces
- What are the two types of body shapes on ectoparasites?
o Dorsal-ventrally flattened like bed bugs and ticks
o Laterally flattened like fleas
o Shapes such as these are important in how the parasite interacts with the host
- What is the purpose of wings?
o Wings enable insects to reach a host
- What are the different types of adaptions of mouthparts?
o Mouthparts can be adapted to feeding on fluids such as blood and secretions, or for feeding externally on the skin
o The arthropod mouthparts have different functions depending on the arthropod. Such functions include biting/chewing, siphoning, piercing/sucking, chewing/lapping, and sponging
- What are the morphological adaptions of legs?
o Ectoparasites have specialized legs that will facilitate the attachment to a host and movement on the host or habitat
- What are some examples of morphological adaptions of legs?
o Claws that grasp and cling to a host to prevent the arthropod from easy removal
o Forelegs with enlarged claws that will grasp onto a host as one walks by
o Large hind legs that permit an arthropod to jump long distances between hosts
- What is the purpose of sensory structures on parasitic arthropods?
o For host location and recognition
- Why would different arthropods have different sensory structures? Why not have an arthropod capable of detecting everything?
o Sensory structures are determined by the arthropod and can detect various signals such as motion, vibration, temperature, moisture, CO2, chemical substances, or visual cues
o If an arthropod survives by only detecting one thing, why waste the energy to build everything else?
- What are the primary sensory organs of insects?
o Antennae and eyes
- What happens if a mosquito lost the Johnston’s organ found on the base of the antenna?
o The insect will no longer be able to detect airborne motion as efficiently
- Why do some arthropods exhibit small or no eyes, like in the case of lice or fleas?
o The eyes are not necessary for finding a host. The lack of eyes or eyes that are reduced in size prevent damage to sensitive organs
- What drives external adaptions (wings and legs) such as wings?
o Internal morphology (the structures inside the insect) which allow for the interpretation of the environment
- How does gas exchange in the arthropod occur?
o Like mammals, arthropods need oxygen, but the gas exchange occurs through the trachea with tubes (spiracles) that branch out throughout the body, contacting every organ of the insect that requires oxygen
o Remember, this is an open system of air flowing in
- Why do you only find small insects, never human size ones?
o The tracheal system of the arthropods limits the maximum body to surface area ratio.
o The tracheal system must remain small to allow for gas exchange to occur throughout the body via spiracles
o The branches of the tracheal system must be short to allow for oxygen diffusion
- How does area enter an arthropod?
o Through the trachea via muscle-controlled spiracles located laterally on the body
- What is the circulatory system of insects like, and compare it to humans?
o The circulatory system of insects is an open system that uses what is called the dorsal vessel (similar to the heart) to pump haemolymph (similar to blood) throughout the body of the insect.
o The flow is regular around the body, and is assisted by muscle contractions and peristaltic contractions of the dorsal vessel
o The haemolymph is pumped from the posterior end, circulating freely around the internal organs
- Describe the nervous system of insects.
o The nervous system contains a variety of sensory mechanisms. It is decentralized. The nervous system is also efficient with the main function of collecting information, processing it internally, and responding appropriately
- Compare the neurotransmitters of insect to humans.
o Neurotransmitters such as acetylcholine and dopamine are also important in insect function. Think of this when it is used as a target in pesticides
- What are the characteristics of the reproductive morphology in insects?
o High reproductive potential often with short lifecycles
o Capability to store sperm from a single mating
o Parthenogenesis/asexual reproduction
- What is the main function of the female reproductive system?
o Egg production
o Storage of male spermatozoa until the eggs are ready to be fertilized
- What is the main function of the male reproductive system?
o Production and storage of spermatozoa
o Transport of viable spermatozoa to the reproductive tract of females
- T/F. All insects undergo metamorphosis.
o False, metamorphosis just means a change in form during development. If the body structure remains the same, it does not undergo metamorphosis
o Because of this difference, metamorphosis is a basis for classification
- Why do some arthropods undergo metamorphosis, while others don’t?
o Evolution. Metamorphosis allows for an increase in the diversity of food sources and an exploitation of environmental resources at different niches
o Overall, it promotes survival, dispersal, and reproduction.
- What is the opposite of metamorphosis?
o Ametabolous
o Ametabolous is when no metamorphosis occurs just a change in the size of the body
- What is the difference in resource exploitation between arthropods that undergo metamorphosis, and arthropods that undergo ametabolous?
o Arthropods that undergo metamorphosis have a completely different body structure permitting them to exploit different niches and habitats, as well as food sources. Conversely, arthropods that do not undergo metamorphosis (ametabolous) have habitats and food sources that remain relatively the same throughout the lifespan of the arthropod
- When can arthropods that undergo ametabolous reproduce?
o Only in the adult stage
- What are the two ways metamorphosis can occur and what is the difference?
o Hemimetabolous and holometabolous
o Hemimetabolous is a gradual, simple, incomplete metamorphosis. The egg will hatch into a nymph which is just a small version of the adult, and gradually molt into an adult. These stages share similar habitats and food sources. Only adults reproduce here even though the stages look the same.
o In holometabolous, there is a complete metamorphosis, with 4 morphologically distinct stages
- What are the three stages of hemimetabolous?
o Egg, nymph, adult
- What are the four stages of holometabolous?
o Egg, larvae, pupa, adult
- What is the difference in habitats/niches between holometabolous and hemimetabolous?
o Holometabolous has 4 distinct stages of life, permitting it to exploit many different niches/habitats
o Hemimetabolous stages of life primarily remain in the same habitat/niche
- Why is it advantageous to have the development stages exploit different habitats/niches?
o Exploitation of different niches prevent competition for food between the stages
- During holometabolous, why are there different stages? Or what is the difference between the stages?
o The immature stage is for feeding and growth. For example, in the pupal stage massive reorganization and growth occurs. Yet the pupal stage is nonfeeding, just growth.
o Conversely, in the adult stage, the primary goal is for dispersal and reproduction
- Besides food, why is there a difference in habitat between the intermediate and the adult stage during metamorphosis?
o In the intermediate stage, the goal of the arthropod is to find a habitat where it can eat as much as possible, while in the adult stage, the goal is to find a habitat that is best suited for reproduction.
- If you wanted to disrupt the formation of wings in a holometabolous arthropod, which stage would you want to disrupt?
o The pupal stage because that is where the major organ development occurs, the transformation.
- T/F. All interactions with the host and the vector are negative.
o False, interactions can be both negative and positive
- What is the relationship between the habitat, vector, and the vector-borne pathogen?
o The habitat must match the mode and route of transmission. For example, if the vector can only feed off a host that cannot sustain the growth of the vector born pathogen, then the pathogen will die.
o The habitat is important for not only the vector, but the vector-borne pathogen
- What is the difference between a vector-borne disease and a disease without a vector?
o A vector-borne disease requires another organisms (a vector (typically an arthropod)) to transmit the disease agent from one individual to another. The vector is required.
o If the disease does not require a vector, based on how it is transmitted, can typically be transmitted directly from one individual to another
- What is the difference between zoonosis and anthroponosis?
o Zoonosis is the infectious disease of non-human vertebrates. The disease is strictly maintained in the animal host. Secondary transmission can occur to humans.
o Anthroponosis is the opposite of zoonosis, it is an infectious disease that occurs only in humans
- T/F. Malaria is a zoonotic disease.
o False, malaria is an infectious disease that only occurs in humans; therefore it is anthroponotic
- What is the difference between endemic and epidemic?
o An endemic disease is a local and stabilized disease in that region. The disease is permanently established in that area and does not cause severe mortality.
o Epidemic is when an unusually high number of cases occur, typically when over 10% of the population has the disease
o Endemic remains below 10%
- The type of endemic is dependent on what?
o The number of cases
o Hyper- means a greater number of cases
- What is the animal version of endemic?
o Enzootic
- What is the difference between hypoendemic, mesoendemic, and hyperendemic disease? Use malaria as an example.
o In all of these cases, the disease is endemic, so it remains stabilized disease in the region, but the key difference is the number of cases.
o Hypoendemic is when the disease is constantly present but has very low incidence, affecting only a small portion of the population
o Mesoendemic is one step up from hypoendemic. Here there is a moderate rate of infection. An area is mesoendemic when 10 to 50% of the children in the area show prior infection with malaria.
o Hyperendemic is the when there is a consistent high incidence rate in the population and all age groups are affected equally.
- What is an antigen?
o External material that has been improperly injected into the body.
- What is the term used for an organisms that can transmit a pathogen from an infected to a non-infected individual?
o A vector, and this is typically an arthropod
- T/F. A pathogen is an organisms that maintains its infection cycle in the host, the human.
o False, a pathogen is an organisms that maintains an infectious cycle in a suitable host, independent from human who become the accidental host.
- Does hematophagy require that a pathogen be present in the vector?
o No, hematophagy is the term used to denote blood-feeding arthropods, not necessarily if they are disease vectors or not
- What are the two types of hematophagous arthropods?
o Obligatory: Require the blood meal
o Facultative: Does not necessarily require the blood meal
- Why can’t all arthropods feed on blood?
o Structure determines function. If the male mosquito has not evolved to feed on blood, can’t find it, or uptake it, it will not feed on blood.
- What is the difference between a host and a vector?
o A host is an arthropod or vertebrate where the pathogen can go through its developmental changes.
o The pathogen needs a host to function and finish developing. A vector will carry the pathogen but does not necessarily have to be the host.
- What relationship can the host have with the pathogen?
o The host can be resistant, susceptible, or silent
- What are the types of host?
o Dead-end host
o Amplifying host
o reservoir
o Definitive host
o Intermediate host
- What kind of relationship can the host have with the pathogen?
o Pathogen resistant
o Susceptible
o Silent
- What is an amplifying host?
o A host where the pathogen can increase in numbers. A feeding vector may become infectious from an amplifying host
o Amplifying hosts are great targets for reinfection
- What is a definitive host?
o An animal where the parasite can undergo development and become sexually mature in the host
- What is an intermediate host?
o An animal in which a multi-host parasite undergoes development but does not sexually mature in the host
- Can a vector be a host?
o Yes
- What is a dead-end host and in what cases may a dead-end host occur?
o A dead-end host is also known as pathogen resistant, meaning that the host may harbor the pathogen, but the vector will not become infective.
o This may be because the level of pathogen in the host remains low in the blood or tissue, so that when the vector feed, there is not enough pathogen to make the vector infected
o Or in the case of EEE, horses can become infected, but because of the structure of the horse, the pathogen cannot develop, or it cannot be taken up and transmitted to humans. Therefore, the horse is a dead-end host
- How is amplifying host different from dead-end host?
o They are opposites of each other. In a dead-end host, there is not enough pathogen produced for the vector to become infected. In an amplifying host, the level of pathogen is sufficient enough that a feeding vector will likely become infected.
o The amplifying host is used to amplify in numbers
- What are the similarities and differences between a definitive host and an intermediate host?
o In both hosts, intermediate and definitive, the parasite will undergo development, but in a definitive host, the parasite will become sexually mature in the host, while in the intermediate host, the parasite does not become sexually mature
- Plasmodium will develop and undergo sexual maturity in the host, the female mosquito. What kind of host is the mosquito?
o Definitive host
- Plasmodium will develop but not become sexually mature in the human. What kind of host is the human?
o Intermediate
- What is the gonotrophic cycle?
o A complete cycle that starts with the host-seeking, blood feeding, digestion, ovulation, and oviposition (laying eggs)
- Why is the gonotrophic cycle important?
o Entomologist are concerned with how long it takes the arthropod to develop and if there is a good match between the pathogen and the vector. If the vector develops so fast that the pathogen does not have enough time to mature, then the pathogen will never be viable for transmission.
o Cycle matching is important.
- What happens during diuresis and why is it important when controlling for vectors?
o Diuresis is when the vector, such as the mosquito must expel the excess water after a blood meal otherwise it would be very heavy.
o If a mosquito does not eliminate excess water, it will be too heavy to fly making it susceptible to predators.
o After feeding, this is why mosquitos remain low to the ground which means control measures can take advantage of this by placing low traps, up to the height of the individual.
- What is the opposite of zoophilic?
o Anthropophilic, meaning prefers humans
o Zoophilic means the vector prefers non-humans
o There is also ornithophilic which means the vector prefers birds
- What is the opposite of exophily?
o Endophily, meaning the arthropod prefers to live indoors
o Exophily means the arthropod prefers to live outdoors
- What is the opposite of exophagy?
o Entophagy, meaning the arthropod prefers to feed (think phagocytosis) indoors
o Exophagy means the arthropod prefers to feed outdoors
- What is the difference between “domestic” and “wild”?
o Domestic is an arthropod that is endophilic and rests there afterwards
o Wild is exophilic and never goes indoors
- If an arthropod prefers to feed on human, lives outdoors, but prefers to feed indoors, what words would use to characterize the arthropod?
o Anthropophilic
o Entophagy
o Exophily
- What will you typically find the central dogma of vector-borne disease applies to?
o In tropical areas where vectors are endemic
- What is the central dogma of vector-borne diseases?
o To know the cycle, it is important to know the landscape, the climate, and the socio-economy that drive the pathogen to the host
o The right conditions will allow vector-borne disease to thrive
- If the climate is perfect for a vector, the socio-economy is poor allowing the vector to thrive, but the landscape is 14,000 feet up a mountain, will the vector-borne disease thrive?
o No, the landscape is not beneficial for the vector to thrive
- T/F. Transmission mode and route mean the same thing in vector-borne diseases and can be used interchangeably.
o False, the mode is the epidemiological characteristic of the pathogen and the disease. The transmission
o The route is the method, and is dependent on the environment, reservoir/host, and the pathogen
- What is the mode of transmission?
o How the pathogen moves between hosts.
o For example, from small organism, to the vector, then to the host.
o Mode equals method of movement from hosts
o Essentially, what does the pathogen do inside the vector.
- What is route of transmission?
o This is how the vector will transmit the pathogen. Will it be through the blood feeding process? Through feces? Or maybe physical contact?
o The route is the exact method (the how) for the pathogen transmission.
- What is host-seeking behavior?
o Exactly as it sounds; to get a meal, the arthropod has to show some kind of behavior that it is looking for a host
- What are some characteristics that can be classified in host-seeking behavior?
o The time of feeding
o The space the vector prefers to feed
o The cues the arthropod uses to seek the host
- When looking at host-seeking behavior, why is the time the vector seeks the host important?
o The time is important because arthropods are particular if they feed diurnal (daytime), nocturnal (night), or crepuscular (twilight).
o This gives you a clue of when the arthropod may be active and seeking a host
- Why is it important to know the space in which the mosquito seeks the host?
o If the vector is exophagic, then it will seek food outside (it does not make sense to put controls inside). If the vector is endophagic, then it is important to know that the host will go inside to eat, therefore you do not need to concentrate on the outside.
- T/F. Arthropods typically use a single type of cue to find their host to conserve on energy. Why evolve a trait that is not necessary.
o False, for example hematophagous arthropods will have different long distance and short distance cues.
- What are some examples of long distance cues?
o CO2
o Lactic acid
o Octanol
o Estrogen (some hematophagous vectors will bite females more because of the higher estrogen)
- What are some examples of short-distance cues?
o Body heat
o Vision
- There has been an uptick in the mosquitos on base and you have been tasked with spraying pesticides, what questions might you ask to figure out where to spray?
o Are the bites occurring indoors or outdoors?
o Are the bites occurring during the day or night?
- A combo of ___ and ___ are used in the process of host-seeking.
o Host-chemo and arthropod-mechanoreceptors
o The chemicals the host excretes and the mechanical receptors of the arthropod (like vibrations)
- If you wanted to avoid mosquitos, would you want to wear more clothing or less?
o Less, the chemicals are contained and paint a picture for the mosquitos the more clothing you wear. For example, mosquitos will bite less if you do not wear large socks because they will have a difficult time finding where exactly the lactic acid is coming from.
- What affects the host-finding ability for the proper transmission of the pathogen to the host?
o The pathogen-infected vector. What capabilities does the vector have in the kind of hosts that it can find? If the perfect host is humans and the vector does not have the capability to find humans, the pathogen will have a very difficult time getting to the host.
- What are some examples of chemo- and mechanoreceptors used during feeding?
o Chemoreceptors can initially be used to locate the host. Chemicals such as CO2 can attract the mosquito to the host. Think of chemoreceptors as chemical cues
o Mechanoreceptors are just how they sense, these are receptors that detect mechanical change like vibrations.
o A combination of chemo and mechanoreceptors are used when a mosquito lands on a host and begins to probe to locate capillaries for feeding
- Why is possible for a mosquito to uptake the blood of the host?
o The saliva of the arthropod has evolved to essentially force the blood to pump into the mosquito through a series of platelet inhibitors, vasodilators, and anticoagulants.
o The outer tube will inject the saliva and work as a vasodilator while creating pressure around the wound that forces the blood up
o These methods have evolved to counteract the homeostasis of the host that prevent the blood from being drawn.
- What is the role of saliva when a female mosquito is feeding on the host?
o Saliva acts as a mechanical pump by increasing pressure on the wound, and as a vasodilator
- T/F. Bites are unique to the arthropod, for example the sting of a bee is different from the bite of a bed bug.
o True, arthropods all evolved differently and have different mechanisms
- Why does a sting look the way that it does, a red dot in the missile with a light-colored puffy area surrounding the sting?
o Something, a toxin, was injected, while severe inflammation forms around the sting
- Why is the bite of a flee much smaller than that of a mosquito?
o The key is the saliva. On a flea bite, the saliva is not as intense in the flee to induce inflammation that results in the pressure build up. Less saliva results in no swelling.
- What evolutionary advantage has allowed the mite to stick to its host?
o Inverted teeth so that when a mite bites, it hooks into the host like an anchor making it very difficult to remove without damaging the insect
- Why is it important to analyze arthropod bites?
o If an individual comes to you complaining about a bug bite, the location gives an idea of where to look. On the ground where the legs gets bitten or higher up with a lot of arm bites.
o Looking at what the bite looks like will also give you an indication of what the arthropod is
o How the arthropod feeds may give you an indication of how the arthropod transmits any potential pathogens.
o Looking at the bite can provide a plethora of clues.
- What are the two modes of pathogen transmission in the vector-host relationship, and provide an example for each?
o Mode of pathogen transmission shows where the pathogen goes. Does it develop in the arthropod? Moves to another arthropod? Gets infected into a host? Sit and replicate in the vector? Essentially, where does the pathogen move.
o Vertical transmission is when the pathogen is transmitted across the same arthropod. For example, the pathogen develops with the vector across the stages in the life cycle. This is known as transstadial transmission, the pathogen stays with the vector
o Conversely, horizontal transmission is when the pathogen can be transmitted across the same species or an amplifying host or a dead-end host. Essentially, the pathogen goes to a new organism.
- What are the two types of horizontal transmission?
o Biological transmission and venereal transmission
- What is the difference between biological transmission and venereal transmission?
o Biological transmission is the interaction between vector and host while venereal is between the same vectors. In both cases, this is the transmission of the pathogen, either to a host or the same vector.
- What are the three types of biological transmission?
o Propagative
o Developmental
o Cyclopropagative
- What is the difference between propagative biological transmission and developmental biological transmission?
o In propagative, the pathogen just multiplied in the arthropod without changing its form
o In developmental, the pathogen will just change form (it will develop) WITHOUT multiplication
- What form of biological transmission is it when a pathogen both multiplies in the arthropod and changes (develops)?
o Cyclopropagative
- What is an example of how venereal transmission can occur?
o Infected males will mate with uninfected females resulting in infected eggs.
o Remember, the vector remains the same
- What is a “route” of pathogen transmission?
o The pathway for transmission, so how is the pathogen being transmitted, the in-between. For example the pathogen travels from the saliva
- What are the different routes of pathogen transmission?
o Salivarian
o Sterocorarian
o Regurgitation
o Active escape/active transfer
o Ingestion
o Co-feeding
- What is the salivarian route of pathogen transmission?
o When pathogen transmission requires salivary gland invasion
- What pathogens require the salivarian route of transmission?
o Plasmodium spp. and anopheles mosquitoes
o Arboviruses and mosquitos/ticks
o Trypanosoma spp. And tsetse flies
- What is the stercorarian route of pathogen transmission?
o When the pathogen is transmitted through arthropod excretions such as through the rectum, urine, and feces
o Sterco comes from the word for the sternum where the excretion of material comes from. The skeleton at the sternum is semipermeable allowing the contents to be excreted
- What pathogens require the stercorarian route of pathogen transmission?
o Trypanosoma cruzi and kissing (triatomine) bugs
o Rickettsia prowazekii and human body louse
- What is the regurgitation route of pathogen transmission?
o The regurgitation of pathogens while the arthropod is feeding on the host
- What are some pathogens that require regurgitation as a route of transmission?
o Yersinia pestis and fleas
o Leishmania and sand fleas
- Why does regurgitation occur?
o To get rid of a previous blood meal so that the arthropod can take up a new blood meal
- What is an example of the active escape/active transfer route of pathogen transmission?
o When a filarial L3 larvae migrates to the mosquito mouthpart and actively escapes the tip
o Another example could be larvae that tear apart openings
o A nematode drops out of the arthropod and into the wound
o Filariasis and mosquitos
o Think of this as when the pathogen drops out of the vector
- How common is active escape/active transfer route of pathogen transmission?
o Well think about it, not only does the pathogen have to crawl out or fall out at the right time, but it also must make it to the right host. This is a very difficult mode of transmission. You would need thousands of mosquito bites for an infection with a nematode from a mosquito.
- Which is a more efficient mode of transmission, active escape of nematode from a mosquito, or salivary transfer of malaria from a mosquito?
o Salivary method, active transfer is a very difficult method of pathogen transmission
- What is the ingestion route of pathogen transmission?
o When a contaminated vector transmits the pathogen to something that is consumed
- What is an example of the ingestion route of pathogen transmission?
o Fecal bacteria and filth flies
o Dog tapeworm and dogs/cats
- What is the co-feeding route of pathogen transmission?
o Co-feeding is when two or more vectors feed next to or in proximity on a host and the salivary secretions of one infected vector will pass the infection to the non-infected one during feeding
o For example, the hemocylc is an open system that allows everything to be transported everywhere, even the salivary gland
- What is also known as “vector-to-vector” feeding?
o Co-feeding
- What are some examples of co-feeding?
o Borrelia burgdorferi and lxodes ticks
- What are the drivers to the ecology of vector and vector-borne diseases?
o International travel
o Antimicrobial drug use
o Global human populations
o Climate change
o Globalization
o Urbanization
o Agricultural and developmental projects
o All the above increase the complexity of vector-borne disease transmission because they can drive the disease one way or another
- What are the different roles vectors can have in ecology?
o Primary/major vector
o Secondary vector
o Non-vector
o Bridge-vector
- Why are the primary/major vectors the vector of interest in research?
o These vectors are the ones that primarily feed on one host, and the pathogen is transmitted to that one host
o The vector is the primary method of transmitting the pathogen to humans or other animals
- What role do secondary vectors play in vector ecology?
o These vectors essentially just maintain the numbers of the pathogen high
o These only supplement the role of transmission of the pathogen
o Secondary vectors feed on one host
o These vectors typically have little contact with humans but can maintain a small number of pathogens. Just another vector that can upkeep the numbers but is not necessarily important in pathogen transmission
- Which vectors are normally of local importance?
o Secondary vectors
- If all the primary vectors of a disease were gone, will the secondary vector be able to maintain the disease?
o In most cases, no
- What is a non-vector?
o These are vectors that cannot transmit a pathogen to man or other animals
- If a vector can hold the pathogen, why would it be a non-vector?
o Maybe the vector does not feed on blood which is required for transmission
o Maybe the route prevents the pathogen from circulating in the body
o Maybe there is something in the genetics of the vector
- What role does a bridge-vector play?
o A significant role in transmitting pathogens because they can transmit from vertebrate to human and vice versa
o Bridg-vectors have multiple host meaning that if a host were to disappear from the environment, the bridge-vector may take up a new host and pass the disease to the new host.
- What affects vector ecology?
o Role of the vector
o Feeding preference
- Why is it important to know the feeding preference of a vector?
o The feeding preference of a vector include the biting location, biting time, and host. All of these preferences will influence transmission of the pathogen
o The time of activity and the behavior can even give you an indication of what kind of species and parasite your are looking at
o It is important to know where, when, and what the vector is feeding on to successfully control the vector
- What are nocturnal vectors?
o Night biters such as the anopheles
o These vectors will have disease pathogens that circulate in the nighttime
- What are diurnal vectors?
o Day biters such as the aedes
- What are crepuscular vectors?
o Biters that will bite in the early morning and evening such as the culex
- What is vector competency?
o The intrinsic ability for a vector to biologically transmit the pathogen
o Essentially, how well can the vector successfully uptake the pathogen, circulate it, and transmit it
- What factors affect the vector competency for a pathogen?
o Susceptibility to infection
o Permissiveness for pathogen development
o Permissiveness for pathogen reproduction
o Duration of incubation period (EIP)
o Transmission efficiency
- Compare the competency of a primary vector to a secondary vector.
o A primary vector will be 100% competent, while a secondary vector will be less than 100% competent, but can still transmit the disease
- What is the significance of an open system inside the mosquito for pathogen ecology?
o The pathogen can go all around the vector of the mosquito
- What is the plasmodium-mosquito midgut interactions?
o Invertebrates are capable of both cellular and humoral responses to combat infections
o The specific factors that block any phase of ookinete development and cell penetration constitute a midgut infection barrier
- What is vector capacity?
o The overall ability of a vector species to transmit a pathogen at a given time and place
o The ecological attributes of the vector relative to pathogen transmission, feeding frequency, and host selection
o Essentially, in that moment in time, how good can the vector transmit the pathogen
- What factors contribute to vector capacity?
o Vector competence
o EIP (extrinsic incubation period)
How long the vector goes from infected to infectious
o Vector/host interactions
o Vector population size/abundance
o Vector longevity
o Vector feeding patterns
o EIR (Ento inoculation rate)
The average number of potentially infective bites that will be delivered by all vectors feeding upon a single host in one day (or other unit of time); related to vectorial capacity and epidemiology
How many people can you inoculate
o Vector resting behavior
o Vector activity profile (dispersal)
o Climate factors that influence EIP and EIR
- Overall, what is vectorial capacity a function of?
o Vector capacity, survivor rate, and density
- Why do we look at vectorial capacity from a function point of view (such as the equation above)?
o Having an equation shows that for an arthropod to approach a host, a number of factors have to work out. Just because there is a high density of hosts, does not mean that capacity is high. The survival of the vector may be so low that the host rarely gets attacked.
o You must look at the equation to determine the capacity for a vector to transmit a pathogen.
- T/F. Transmission rate is determined by vector competency. So, if the vector competency is low, then transmission will be low.
o False, a low vector competency can be offset by a high vector capacity and how the vector thrives in the peridomestic environment (human environment)
- What kind of conditions may cause a vector to have different transmission rate?
o Poor housing conditions
o Human behavior
o Entomological indices and malaria metrics ranged among localities
o Different prevalences of infections
o Different biting rates
o Different vectorial capacity
o Different vector competence
o Habitat and breeding sites
o Number of hosts
o Range expansion (humans increasing land use, irrigation, moving, wars, etc.)
