WELCOME TO ARISE INFECTIOUS DISEASE PROJECT
VOCABULARY
Pathogen: A bacterium, virus, or other microorganism that can cause disease.
Susceptible: Likely or liable to be influenced or harmed.
A Host: A place where a pathogen lives.
Disease: A disorder of structure or function in a human, animal, or plant, especially one that produces specific signs or symptoms.
Reservoir: A place to live.
Portal of exit: The site from where micro-organisms leave the host to enter another host and cause disease/infection.
Mode of transmission: The passing of a pathogen from a reservoir to a susceptible host.
Portal of entry: the site through which microorganisms enter the susceptible host and cause disease/infection.
Bacteria: A microscopic living organism, usually one-celled, that can be found everywhere.
Virus: A small infectious agent that replicates only inside the living cells of other organisms.
Fungi: Parasites on living organisms
Protozoans: It’s an informal term for single-celled eukaryotes, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris.
Prions: an infectious protein particle similar to a virus but lacking nucleic acid; thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system.
BACTERIA AND VIRUSES
Difference between a bacteria and a virus?
A virus is 10 to 100 times smaller than a bacteria. Viruses are also frequently believed to be organic structures that interact with living organisms to reproduce and remain alive. Meanwhile, bacteria are living organisms that duplicate through a form of asexual reproduction called binary fission. Overall, the main difference is that a bacterial illness can be cured with an antibiotic and a viral disease can only be treated and not cured.
FOUR DIFFERENT TYPES OF INFECTIONS
Endogenous
Exogenous
Noscomia
Opportunistic
THE CHAIN OF INFECTION
A chain of infection starts with a pathogen discovering a reservoir. The pathogen needs a mode of transmission from human to human contact or through surfaces that have been contaminated. Another thing the pathogen needs is a portal of entry and that could be a human’s respiratory, circulatory, or digestive system. Once the pathogen is inside, it proceeds to attack cells while the human body tries to restore homeostasis. Then, the pathogen is able to spread through the portal of exit: saliva, feces, urine, etc.
TYPHUS
Typhus is a disease that is caused by the pathogen, Rickettsia. Normally, the mode of transmission is through the bite of arthropods; fleas, lice, ticks, or mites. When arthropods are infected by rickettsia and they bite someone, the bacteria that causes typhus is transmitted to the person. Scratching the bite leads the bacteria to spread and have more access to the bloodstream where it is able to grow and reproduce. Typhus is worldwide, but usually only occurs in third world countries where there is poverty, bad sanitation, and close human contact.
THE BACTERIA CELL OF RICKETTSIA
THREE DIFFERENT FORMS OF TYPHUS
There are three different types of typhus that can be transmitted to humans: epidemic (louse-borne) typhus, endemic (murine) typhus, and scrub typhus. The type of typhus that someone is infected by depends on the arthropod that bit them. Arthropods tend to be carriers of a typhus strain that is specific to their species. Each form of typhus has similar and different forms of symptoms.
EPIDEMIC (LOUSE-BORNE) TYPHUS
This form of typhus is caused by the bacteria, Rickettsia prowazekii. This bacteria is carried by the body’s louse; insects that exist in the human body due to poor hygiene.
Symptoms:
Severe headache
Severe muscle pain
Low blood pressure
Confusion
Rash that spreads
Insensibility
High fever
Light sensitivity
ENDEMIC TYPHUS
This kind of typhus is also known as murine typhus. It’s caused by the bacteria, Rickettsia typhi which is found in the rat flea or the cat flea. People with this type of typhus tend to have close contact with rats.
Symptoms:
Dry cough
Diarrhea
Nausea and vomiting
SCRUB TYPHUS
This type of typhus is caused by Orientia tsutsugamushi which is just a fancy word for a bacteria that is part of the Rickettsia family. It’s carried by mites, fleas, louse, or ticks. People can get infected by the bite of arthropods, through their feces, and sleeping on a bed filled with lice.
Symptoms:
Rash
A cough
Swollen lymph nodes
A sore located at the spot where the bite occurred
Tiredness
COMMON SYMPTOMS SEEN IN ALL 3 FORMS OF TYPHUS:
Headache
Fever
Rash
Chills
The period of incubation for typhus is five to fourteen days, meaning that symptoms won’t be noticeable for up to five to fourteen days after you are bitten. The duration of the disease is different for everybody because it depends on what type of typhus you have and how developed/severe it is. However, there is a vaccine that cures typhus but if left untreated it will result in death.
HOW DOES THE IMMUNE SYSTEM RESPOND?
The immune system is made up of cells, protein, tissues, and organs. Its main job is to defend the body against infectious organisms and invaders. The immune system responds by using white blood cells to find and destroy disease-causing organisms/substances. This system also uses B cells to produce antibodies: specialized proteins that lock onto specific antigens. Once the antibodies have been made, they stay in a person’s body so that if their immune system encounters that same antigen it is able to easily destroy it. However, even though the antibodies are able to find and lock into an antigen they could not destroy it without the help of T cells. Many T cells are called “killer cells” because they kill antigens that have been identified by antibodies.
However, the immune system fails in fighting back typhus. It is widely unknown why the immune system fails but research is still being done to better understand how the rickettsia bacteria attacks the immune system.
DEFENSES AVAILABLE
Rudolf Weigl was a biologist that successfully developed a typhus vaccine in 1933. However, the number of typhus cases has decreased by a lot so the manufacturing of the vaccine has ended. Worry not, there are still three treatments that can cure typhus: Doxycycline, Chloramphenicol, and Ciprofloxacin. Doxycycline is the preferred treatment but Chloramphenicol is the treatment used for pregnant women. Finally, Ciprofloxacin is the treatment designed for people that are unable to take Doxycycline.
PREVENTING TYPHUS:
Having good personal hygiene (no lice.. etc)
Buy tick, mite, and insect repellent
Avoid traveling to countries that have had a typhus outbreak
Monitor the rodent population in your environment
SOURCES
1. "Typhus." Healthline. 12/18/18. https://www.healthline.com/health/typhus
2. "Typhus Fever." World Health Organization. 12/18/18. https://www.who.int/ith/diseases/typhusfever/en/
3. "Bacteria and Viruses." 12/18/18. Bradley University. https://onlinedegrees.bradley.edu/nursing/bacteria-and-viruses-how-are-they-different/
4. "Immune System." 12/18/18. Kids Health. https://kidshealth.org/en/parents/immune.html
5. "Rickettsia." Alamy. 12/18/18. https://www.alamy.com/stock-photo/rickettsia.html
6. "Stop Typhus." 123RF. 12/18/18. https://www.123rf.com/photo_59788597_stop-typhus-syringe-is-filled-with-injection-syringe-and-vaccine.html
7. "Bacteria Rickettsia." BigStock. 12/18/18. https://www.bigstockphoto.com/image-156705293/stock-photo-bacteria-rickettsia-inside-human-cell%2C-3d-illustration-gram-negative-bacteria-which-cause-epidemic-typhus%2C-murine-typhus-other-rickettsioses-and-are-transmitted-by-arthropods
8. "How Bacteria Differs from Viruses." WebMd.com. 12/18/18. https://www.google.com/search?q=infections&rlz=1C1GGRV_enUS751US751&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiH0PKS3KrfAhWtFzQIHdRIDZAQ_AUIDigB&biw=1280&bih=913#imgrc=Wi1DHbCJ9C5clM:
9. "Infection and Immunity." PMC. 12/18/18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC261167/
10. "Scrub Typhus." Medical Entomology. 12/18/18. http://www.faculty.ucr.edu/~legneref/medical/scrubtyphus.htm