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Biological transmission occurs when the pathogen reproduces within a biological vector that transmits the pathogen from one host to another ( [link] ). Arthropods are the main vectors responsible for biological transmission ( [link] ). Most arthropod vectors transmit the pathogen by biting the host, creating a wound that serves as a portal of entry. The pathogen may go through part of its reproductive cycle in the gut or salivary glands of the arthropod to facilitate its transmission through the bite. For example, hemipterans (called “kissing bugs” or “assassin bugs”) transmit Chagas disease to humans by defecating when they bite, after which the human scratches or rubs the infected feces into a mucous membrane or break in the skin.

Biological insect vectors include mosquitoes , which transmit malaria and other diseases, and lice , which transmit typhus . Other arthropod vectors can include arachnids, primarily ticks , which transmit Lyme disease and other diseases, and mites , which transmit scrub typhus and rickettsial pox . Biological transmission, because it involves survival and reproduction within a parasitized vector, complicates the biology of the pathogen and its transmission. There are also important non-arthropod vectors of disease, including mammals and birds. Various species of mammals can transmit rabies to humans, usually by means of a bite that transmits the rabies virus. Chickens and other domestic poultry can transmit avian influenza to humans through direct or indirect contact with avian influenza virus A shed in the birds’ saliva, mucous, and feces.

a) Step 1: fly picks up pathogen from fecal matter and carries it on its body. 2: Fly transfers pathogen to food. 3: Person eats contaminated food and gets sick. B) Step 1: Infected mosquito bites uninfected person. 2: Infections spreads through body and into red blood cells. 3: Second mosquito bites infected person. Mosquito may now transmit infection to another person.
(a) A mechanical vector carries a pathogen on its body from one host to another, not as an infection. (b) A biological vector carries a pathogen from one host to another after becoming infected itself.
Table titled common arthropod vectors and selected pathogens. Columns: Vector; species, pathogen; disease. Black fly; Simulium spp.; Onchocerca volvulus; Onchocerciasis (river blindness). Flea (has 2). Ctenocephalides felis; Bartonella henselae; cat scratch disease. Xenopsylla cheopis (has 2). Rickettsia typhi; murine typhus. Yersinia pestis; plague. Kissing bug, Triatoma spp.; Trypanosoma cruzi; Chagas disease. Louse; Pediculus humanus humanus (has 3) Bartonella quintana; trench fever. Borrelia recurrentis; relapsing fever. Rickettsia prowazekii; typhus. Mite/chigger (has 2).  Leptotrombidium spp.; Orientia tsutsugamushi; scrub typhus. Rickettsia akari; rickettsialpox. Moquito (has 3). Aedes spp and Haemogogus spp.; yellow fever virus; yellow fever. Anopheles spp.; Plasmodium falciparum; malaria. Cutex pipiens; west nile virus, west nile disease. Sand fly; Phlebotomus spp.; Leishmania spp.; Leishmaniasis. Tick (has 2): Ixodes spp; Borrelia spp.; Lyme disease. Dermacentor spp. And others; Rickettsi rickettsia; rocky mountain spotted fever. Tsetse fly; Glossina spp. Trypanosoma brucei Trypanosomiasis (sleepting sickness).
(credit “Black fly”, “Tick”, “Tsetse fly”: modification of work by USDA; credit: “Flea”: modification of work by Centers for Disease Control and Prevention; credit: “Louse”, “Mosquito”, “Sand fly”: modification of work by James Gathany, Centers for Disease Control and Prevention; credit “Kissing bug”: modification of work by Glenn Seplak; credit “Mite”: modification of work by Michael Wunderli)
  • Describe how diseases can be transmitted through the air.
  • Explain the difference between a mechanical vector and a biological vector.

Using gmos to stop the spread of zika

In 2016, an epidemic of the Zika virus was linked to a high incidence of birth defects in South America and Central America. As winter turned to spring in the northern hemisphere, health officials correctly predicted the virus would spread to North America, coinciding with the breeding season of its major vector, the Aedes aegypti mosquito.

The range of the A. aegypti mosquito extends well into the southern United States ( [link] ). Because these same mosquitoes serve as vectors for other problematic diseases ( dengue fever , yellow fever , and others), various methods of mosquito control have been proposed as solutions. Chemical pesticides have been used effectively in the past, and are likely to be used again; but because chemical pesticides can have negative impacts on the environment, some scientists have proposed an alternative that involves genetically engineering A. aegypti so that it cannot reproduce. This method, however, has been the subject of some controversy.

One method that has worked in the past to control pests, with little apparent downside, has been sterile male introductions. This method controlled the screw-worm fly pest in the southwest United States and fruit fly pests of fruit crops. In this method, males of the target species are reared in the lab, sterilized with radiation, and released into the environment where they mate with wild females, who subsequently bear no live offspring. Repeated releases shrink the pest population.

A similar method, taking advantage of recombinant DNA technology, Blandine Massonnet-Bruneel, Nicole Corre-Catelin, Renaud Lacroix, Rosemary S. Lees, Kim Phuc Hoang, Derric Nimmo, Luke Alphey, and Paul Reiter. “Fitness of Transgenic Mosquito Aedes aegypti Males Carrying a Dominant Lethal Genetic System.” PLOS ONE 8, no. 5 (2013): e62711. introduces a dominant lethal allele into male mosquitoes that is suppressed in the presence of tetracycline (an antibiotic) during laboratory rearing. The males are released into the environment and mate with female mosquitoes. Unlike the sterile male method, these matings produce offspring, but they die as larvae from the lethal gene in the absence of tetracycline in the environment. As of 2016, this method has yet to be implemented in the United States, but a UK company tested the method in Piracicaba, Brazil, and found an 82% reduction in wild A. aegypti larvae and a 91% reduction in dengue cases in the treated area. Richard Levine. “Cases of Dengue Drop 91 Percent Due to Genetically Modified Mosquitoes.” Entomology Today. https://entomologytoday.org/2016/07/14/cases-of-dengue-drop-91-due-to-genetically-modified-mosquitoes. In August 2016, amid news of Zika infections in several Florida communities, the FDA gave the UK company permission to test this same mosquito control method in Key West, Florida, pending compliance with local and state regulations and a referendum in the affected communities.

The use of genetically modified organisms (GMOs) to control a disease vector has its advocates as well as its opponents. In theory, the system could be used to drive the A. aegypti mosquito extinct—a noble goal according to some, given the damage they do to human populations. Olivia Judson. “A Bug’s Death.” The New York Times , September 25, 2003. http://www.nytimes.com/2003/09/25/opinion/a-bug-s-death.html. But opponents of the idea are concerned that the gene could escape the species boundary of A. aegypti and cause problems in other species, leading to unforeseen ecological consequences. Opponents are also wary of the program because it is being administered by a for-profit corporation, creating the potential for conflicts of interest that would have to be tightly regulated; and it is not clear how any unintended consequences of the program could be reversed.

There are other epidemiological considerations as well. Aedes aegypti is apparently not the only vector for the Zika virus. Aedes albopictus , the Asian tiger mosquito, is also a vector for the Zika virus. Gilda Grard, Mélanie Caron, Illich Manfred Mombo, Dieudonné Nkoghe, Statiana Mboui Ondo, Davy Jiolle, Didier Fontenille, Christophe Paupy, and Eric Maurice Leroy. “Zika Virus in Gabon (Central Africa)–2007: A New Threat from Aedes albopictus ?” PLOS Neglected Tropical Diseases 8, no. 2 (2014): e2681. A. albopictus is now widespread around the planet including much of the United States ( [link] ). Many other mosquitoes have been found to harbor Zika virus, though their capacity to act as vectors is unknown. Constância F.J. Ayres. “Identification of Zika Virus Vectors and Implications for Control.” The Lancet Infectious Diseases 16, no. 3 (2016): 278–279. Genetically modified strains of A. aegypti will not control the other species of vectors. Finally, the Zika virus can apparently be transmitted sexually between human hosts, from mother to child, and possibly through blood transfusion. All of these factors must be considered in any approach to controlling the spread of the virus.

Clearly there are risks and unknowns involved in conducting an open-environment experiment of an as-yet poorly understood technology. But allowing the Zika virus to spread unchecked is also risky. Does the threat of a Zika epidemic justify the ecological risk of genetically engineering mosquitos? Are current methods of mosquito control sufficiently ineffective or harmful that we need to try untested alternatives? These are the questions being put to public health officials now.

Micrograph of brown dots of about 50 nm inside cells; dots re labeled Zika virus. Photo of mosquito labeled Aedes aegypti. Map of where mosquitoes are found in the US. Aedes aegypti and Aedes albopictus are both found in the lower half of the US, reaching up to Connecticut, Missouri, and California. Aedes albopictus reaches further north in the eastern part o the country; through Minnosota. Aedes aegypti reaches a bit further into Utah and is in Puerto Rico.
The Zika virus is an enveloped virus transmitted by mosquitoes, especially Aedes aegypti. The range of this mosquito includes much of the United States, from the Southwest and Southeast to as far north as the Mid-Atlantic. The range of A. albopictus , another vector, extends even farther north to New England and parts of the Midwest. (credit micrograph: modification of work by Cynthia Goldsmith, Centers for Disease Control and Prevention; credit photo: modification of work by James Gathany, Centers for Disease Control and Prevention; credit map: modification of work by Centers for Disease Control and Prevention)

Questions & Answers

what is the reference between selective medium and differential medium?
Tony Reply
the micro flora of air is transient why
Princess
Hello.... Am new here
essien Reply
welcome essien
Muhammad
welcome essien
Beka
classification of gram positive
lissa Reply
classify gram positive
lissa
catalase test is done to differentiate between staph and strep. as staph is catalase positive while strep is catalase negative then staph is differentiate further on coagulase positive and coagulase negative. staph aureus is coagulase positive while staph epidermidis is coagulase negative.
Muhammad
gram positive staph is further differentiated on sensitivity test and manitol salt fermentation test while gram positive strep is differentiated on hemolysis pattern
Muhammad
more about gramm positive
lissa
please
lissa
ok
Blessing
am back any gist
Blessing
taxonomy
Rahul
can i use the graph of bacterial growth for my master's thesis?
Christoph Reply
facultative anaerobic bavteria gives uniform turdibity in nutrient broth why?
Princess Reply
oils and waxes are not sterilized in autoclave
Princess
what is the function of paraffin
Muhammad
@ MAHI because they can grow all over the media from surface to the bottom as they can utilize oxygen or conduct fermentation in its absence.
Online
2.@MAHI Autoclave uses steam under pressure. The steam cannot penetrate through oil and wax. Thus, dry heat sterilization is preferred than autoclave .
Online
thnku
Nadiya
how nutirent agar can converted into blood agar
Princess
thank you
Princess
take a nutrient agar ........and add 5ml blood and put in it ...........!
Nadiya
nutrient agar +blood 5ml+ distilled water =blood agar .
Nadiya
mixed wellllll
Nadiya
hi
Rahul
why agar is not a neutrient source?
Shimul
because it's a general purpose agar only use for growing bacteria
Richa
way is antigen
opaleye
what is antigen
opaleye
antigen is a foreign body that cause activation of antibody?
ASNAKE
Antigen is a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
Shimul
thanks for that
opaleye
what is pharmacology
Luyenu
a science that studies about the drug
ASNAKE
hello ever one
Sayid
y
Abdul
Work hard
Anigor
y
Abdul
thanks alot
Luyenu
What is the major different between gram positive and gram negative bacteria.
Asikur
bacteria kya hai
Mala
content of their cell wall
Doris
koi mujhse basic microbiology ki study k Lea book suggest kro .
Richa
Harley prescott
Vikas
what are the five predisposing factors of opportunistic infections
Asher Reply
1. long term exposure to diseases, that the body immunity weakens.
prosper
2. Nature Of some diseases to weaken body immunity such as, AIDS.
prosper
3. Use of immuno-suppresive drugs.
prosper
anyone... need a hand here 🙋😞
prosper
Low immune is the major cause eg for kaposis sarcoma
Davismith
suitable conditions e.g temp,
Muhammad
what os gnormal flora
kifayat Reply
morphological and genetic classification of bacteria
Potter Reply
what is the morphogical
Bupe
h
Sudhir
morphologycal is defined as relating to the branch of biology that deals with the form of living organisms,and with relationship between their structures.
Nadiya
relating to the form or structure of things .
Nadiya
what is the meaning of lessions
oluwa
i am frim Afghanistan.
wahidullah Reply
iam from iraq
Haidar
and i'm from pakistan
Muhammad
Nice
Amina
what's about the qualification
Muhammad
Hlo
Asiya
Hmm
Number
Almustafa Muhammad from Nigeria
Mujtafa
am ustaz Abdulsalam from Ghana
ustaz
am Bupe Chifita from Zambia
Bupe
what is microbiology
Bupe
is the study of invisible micro organism
Mujtafa
microbiology is the study of very too small organisms which we can't see with naked eyes ......in other words ....study of microorganism is called microbiology.
Nadiya
Hello! How Can Microorganisms Be Isolated From The Skin?.. 5 ways if possible. (briefly)
prosper
from skin swabbing is the prefer method worldwide
Muhammad
thanks Muhammad Nauman very much!
prosper
hi
Meek
hi Meek
prosper
are there any other ways pals?
prosper
hi prosper
Meek
hello Meek Mild.
prosper
Any question or ideas, Meek?😊
prosper
and if a patient have any blister or abscess on the skin then first cut the blister or abscess. inside material is taking by syringe.
Muhammad
in case of fingernail or toenails simply cut a small piece of nail and culture on the appropriate media at a required temperature and time
Muhammad
Again, thanks Mr. Muhammad! I appreciate the help.
prosper
you welcom prosper 😊
Muhammad
what are the media use for skin swab?
Sieh-Mlanwin
blood and macckonkey mostly usededia for skin bacteria
Muhammad
used media*
Muhammad
@ SIEH mostly fungal infection occurs in skin so SDA ( Sabouraud Dextrose Agar) or MEA ( Malt extract agar) are common.
Online
thanks
Sieh-Mlanwin
Microbiologicam source of vitamins
Bachi Reply
what do you mean?
Md
that's example?
Md
hi everyone
Muhammad
such as. c/s media
Md
hmm hlw
Md
just tell me about that ?
Md
where are u from
Muhammad
history of Bactolagy?
Piyush Reply
ask me any question you want on microbiology
Norbuqaari Reply
what is scale up fermenter ? and whict bectetia is benifited in industrial microbilogy ?
Nadiya
can u explain to me wts the meaning of autoclave,and how it doing and ,wt r the equipment to need to do it?
chandi
stem heat under pressure
Nadiya
thnks
chandi
autoclave is a steam heat under pressure .it is use to sterilize the equipment, agar ,petridish broth liquid and many more things....to kill the microbes.......free from microbes
Nadiya
nadiya Scale up studies refers to the act of using results obtained from laboratory studies for designing a prototype and a pilot plant process. do you agree or
Norbuqaari
bectetia is benifited in industrial microbilogy is lactobacilli
Norbuqaari
and
Nadiya
chandi. strong heated container used for chemical reactions and other processes using high pressures and temperatures, e.g. steam sterilization.
Norbuqaari
another
Norbuqaari
who is father of microbiology?
Norbuqaari
anton van leoven hook
chandi
antonie van leeuwenhoek
chandi
thanks
Norbuqaari
what is microbial taxonomy
Ini
what is normal flora
kifayat
normal flora contains the microorganisms which lives on and in our body but can not cause diseases easily....e.g staph. aureus lives on our body they dont cause disease in normal conditions whenever our skin is injured by any cut or wound then they enter into the body and cause diseases
Muhammad
two types of normal flora .... one is the resident normal flora and the other is transient normal flora.....resident normal flora is reside on our body in every condition but transient normal flora changes with the conditions
Muhammad
what is the method used for anaerobic bacteria to grow in the lab other then the candle jar method?
Muhammad
Why those beans water smell
Asiya
wow
Sebewu
hahahaha
Kwame
Asiya Ibrahim please beans water how? please come clear!
Kwame
what is the purpose of gam staining
Norbuqaari Reply
the purpose of gram staining is to differentiate and classified bacteria and other microbes !
Nadiya
the purpose of gram staining is to differentiate between gram negative bacteria and gram positive bacteria
Leah
thanks Nadiya... Thank you Leah Kalasya..Safari njema!
prosper
remember me in yr prayers norbuqaari ! 🙂
Nadiya
what is the virus?
Norbuqaari Reply
an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.
chandi
chandi sheeth thanks alot
Norbuqaari
😊😊😊
chandi
what is bacteria
Ibrahim Reply
a member of a large group of unicellular microorganisms which have cell walls but lack organelles and on organised nucleus and ,including some which can cause disease
Nadiya
what is a germ
Ibrahim
a microorganisms,speciallay one which causes disease .
Nadiya
bacteria are a type of biological cells. They are unicellular. Bacteria were among the first life forms appear on the earth. they have a number of shapes, typically a few micrometers in length. They are present in of its habitata on earth.
isha
What is Auto clave?
Lovely
Autoclave is a pressure chamber used to sterilize equipments
praveen
hi
Lovely
n
vijaya
hii
chandi
what is a Laminar air flow?
isha
Laminar airflow cabinet is a carefully enclosed bench designed to prevent contamination of semiconductor wafers, biological samples or any particle sensitive materials
praveen
Praveen Deepi.... thnq....
isha
what bacteria causes malaria
Silas
female anaphilis mosquitos!
Nadiya
malaria isn`t caused by a bacteria rather by a digenetic parasite named Plasmodium.
Online
plasmodium sp
SRUTHI
its caused by a plasmodium germ....
Cotilda
Malariya cycle
Mohit
malariya cycle is
xasan
what is sterilization.
Shujjat
process of removing of microorganisms
SRUTHI
May anyone cite some few examples of Gram negative bacteria.😕
prosper
tnx shrutti
Shujjat
 Escherichia coli, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Chlamydia trachomatis, and Yersinia pestis.
rohit
prokeryot and eukoryot ?
Shujjat
can anyone describe for me some roles played by lipids?
Cotilda
short description on C-reactive proteins plz
WINFRED
lipids regulate membrane permeability, lipids are storage compounds, triglycerides serve as reserve energy of the body, lipids are the important compounds of cell membrane structure in eucaryotic cell, lipids serve as source of fat soluble vitamins....
isha
what is dry heat
Shahid
C-reactiv proteins is a blood test marker inflammation in the body. It called CRP also. It's produced in the lever and it's level is measured by testing the blood. It is classified as an acute phase reachant, which mean that it's levels will rise in response to inflammation.
isha
what is stlization
Shahid
dry heat is used to kill the microorganisms.using of flame is an example for dry heat
SRUTHI
what is pasteurization
SRUTHI
what is mothed of dry heat
Shahid
the process of making something free from bacteria or other living microorganisms.
Nadiya
is called sterilization.
Nadiya
incineration
SRUTHI
buring
SRUTHI
incineration is a waste treatment process that involves the combustion of organic substance contain in waste material .this method also burns any organisms yo ash!
Nadiya
pasteurization is a process to kill or to finish the pathogenic microorganisms in milk or fruit juice (liquid food) by heat treatment... less than 100 degree Celsius....or 212 degree Fahrenheit temperature...
isha
pasteurization is a process of heating ,and then rapidly cooling ,liquid or food in order to kill microbes that may expedite their spoilage or cause disease .and .....French scientists who invented the process of pasteurization was Louis pasteur.
Nadiya
is the single celled organisms that can existance independent or dependent living
Norbuqaari
i think it dependent
chandi

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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