Infectious diseases - transmission and prevention - class-VII

Among many epidemiologic triad or triangle, the traditional model for an infectious disease (The triad ) consists of an external agent, a susceptible host, and an environment. So, the correct option B ( Host, agent, and environment )

Neutrophils. The first immune cells that arrive at an injured site are mostly neutrophils, which are quick-response immune cells that recognize and destroy bacteria. 

Infectious diseases are those diseases which are caused by microorganisms like fungi, bacteria, virus, parasites. HIV (Human immunodeficiency virus) causes AIDS (Acquired immunodeficiency syndrome). It is a sexually transmitted disease. Diphtheria is caused by bacterium Corynebacterium diphtheria. It affects the mucous membrane of throat and upper respiratory tract. Coronary thrombosis is a disease that results due to accumulation of blood clot on the walls of arteries. Diabetes mellitus is a disease that results due to insufficient production of insulin in the body.

IgM is the largest antibody and the first to be synthesized by a fetus in response to an intrauterine infection. Because IgM is a pentamer, it cannot cross the placental barrier from the mother, meaning any IgM detected in a newborn's blood originates from the fetus itself due to an active infection.

Prions are proteinaceous infectious agents that cause spongiform encephalopathies, such as Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. Potato spindle tuber disease is caused by a viroid, which is a naked RNA molecule. Red rust of tea and white rust of crucifers are caused by algal and fungal pathogens, respectively.

The limitations that are confronted while treating an infectious disease are that the impaired body functions happened due to the infection cannot recover completely, the patient is asked to have complete bed rest and infectious disease can spread from one person to another as it a contentious disease.

Mosquito-borne diseases or mosquito-borne illness are disease caused by bacterial, viruses or parasites transmitted by mosquitoes. They can transmit disease without being affected themselves. Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases, and viruses such as dengue, encephalitis and yellow fever. 

• Measles, mumps, rubella, and varicella (commonly known as chickenpox), influenza are the chronic diseases of a virus. 
• These can be prevented from spreading by using vaccines. This vaccine works by prior exposure of a small dose of the virus or a protein from the virus, which activates the immune response.

Some infectious diseases can be passed from person to person. Some are transmitted by bites from insects or animals. And others are acquired by ingesting contaminated food or water or being exposed to organisms in the environment. Therefore, (d) is the correct answer.

Vector borne diseases are illnesses caused by an infectious microbe that is transmitted to vertebrates by another animal, usually an arthropod. This second animal is called a vector for the disease. There are a large number of viral, bacterial and parasitic diseases that can be transmitted by insect vectors. The most common vectors are blood sucking insects such as mosquitoes, fleas, lice, biting flies, bugs, lice, helminths and ticks. Most common vector borne diseases affecting people and their vectors are: malaria -anopheles mosquitoes, dengue and chikungunya - aedes mosquitoes, Leishmaniasis (kala azar) - sandflies, trypanosomiasis (gambia fever) - flies and bugs, filariasis - mosquitoes, encephalitis - mosquitoes and ticks, yellow fever - mosquito, plague - flies, lyme disease - ticks etc.

Pathogen is an infectious agent such as a virus, bacterium, prion, fungus, viriod or parasite that causes disease in its host. The host may be an animal, a plant, a fungus, or even another microorganism.

Food prepared in unhygienic conditions can lead to diseases. Use of contaminated water, dirty utensils, not washing raw materials before cooking, inappropriate cooking practices are all source of contamination and can result in infection. Therefore, (a) is the correct answer.

Pathogen is the term used to describe an infectious agent that causes disease in the host. Therefore, (a) is the correct answer.

Air, water and soil are carriers of infectious organisms. Soil can cause contamination of plants and infect them and hence, the human. Air is the most common carriers of pathogens around us. Therefore, (d) is the correct answer.

There are numerous ways through which infections can be transmitted. Coughing by the infected person can cause transfer as the organisms coming out are inhaled by the healthy person. No use of proper sanitization can also cause transmission of diseases. Therefore, (b) is the correct answer.

Latent infection is one which do not show any signs or symptoms at first but can naturally develop over time. Therefore, (a) is the correct answer.

Measles is caused by the type of paramyxovirus known as rubella virus.

Explanation: It is an actual infectious disease of cattle, buffalo, sheep and goat. It distances transportation. In India, the disease is enzootic in nature. Etiology environmental conditions, malnutrition and long distance transportation. In India, the disease is enzootic in nature.

Encephalitis is the disorder in which there is inflammation of the meninges of the brain. This disease may be caused due to bacterial or viral infection and is transmitted by the vector which is the Culex mosquito. Malaria is a disorder which is caused by the protozoan Plasmodium vivax. The disease is transmitted by the Anopheles mosquito. 

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• A disease vector is an agent who carries and transmits an infectious pathogen into another living organism.
• Female Anopheles mosquito serves as vector for malaria.
• Musa(house fly)serves as a vector for at least 65 diseases to humans, including typhoid fever, dysentery, cholera, poliomyelitis, yaws, anthrax, tularemia, leprosy, and tuberculosis.
• Culex mosquito serves as a vector for arbovirus infections such as West Nile virus, Japanese encephalitis, or St. Louis encephalitis, but also filariasis.
• Hence Vectors are Anopheles, Musca, and Culex.
• So, the correct answer is 'Anopheles, Musca, and Culex'.

Droplet infection is an infection transmitted from one individual to another by droplets of moisture expelled from the upper respiratory tract through sneezing or coughing. Direct transmission occurs when there is physical contact between an infected person and a susceptible person. Droplet infection is a mode of direct transmission in which the infection is transmitted by coughing, sneezing.

• Diseases transmitted by mosquitoes include: malaria, dengue,Yellow fever,Elephantiasis West Nile virus, chikungunya, filariasis, tularemia, dirofilariasis, Japanese encephalitis, Saint Louis encephalitis, Western equine encephalitis, Eastern equine encephalitis, Venezuelan equine encephalitis, Ross River fever, Barmah Forest fever, La Crosse encephalitis, and Zika fever,as well as newly detected Keystone virus and Rift Valley fever.
• Out of pneumonia, gangrene, yellow fever, dengue fever, malaria and elephantiasis, mosquitoes transmit 4 diseases they are Yellow fever, dengue, malaria, and elephantiasis.
  
• So, the correct answer is '4'.

• A disease vector is an agent who carries and transmits an infectious pathogen into another living organism.
• Vector-borne diseases are human illnesses caused by parasites, viruses, and bacteria that are spread by insects like mosquitoes, sandflies, triatomine bugs, black flies, ticks, tsetse flies, mites, snails and lice. For example, Female Anopheles mosquito is a vector for malaria.
• Hence Vector insects are which spread disease.
  
• So, the correct answer is 'Spread disease'.

• African trypanosomiasis, also known as sleeping sickness, is an insect-borne parasitic disease of humans and other animals. It is caused by protozoa of the species Trypanosoma brucei. It is transmitted by the bite of an infected tsetse fly which acts as a vector.
  
• Malaria is a mosquito-borne infectious disease affecting humans and other animals caused by Plasmodium species. The disease is most commonly transmitted by an infected female Anopheles mosquito which acts as a vector.
  
• Kala-azar is a disease caused by protozoan parasites belonging to genus Leishmania. The disease is transmitted by insects which act as vectors such as sand fly.

Biological agents which cause disease are known as pathogens that are the micro-organisms which when successfully infect the human body, multiply and produce toxins in incubation period which interfere with the normal functioning of the body and cause disease. A virus is a small, infectious, biological agent that replicates only inside the living cells of other organisms.

• Malaria is caused by a one-celled parasite called a Plasmodium. Female Anopheles mosquitoes pick up the parasite from infected people when they bite to obtain blood needed to nurture their eggs. Inside the mosquito, the parasites reproduce and develop.
• In Filariasis, mosquitoes can transmit the parasite, depending on the geographic area. In Africa, the most common vector is Anopheles. During a meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the wound. 
• Hence, Plasmodium ovale and Wuchereria bancrofti human parasites require mosquito to complete their life cycle.
• So, the correct answer is 'Plasmodium ovale and Wuchereria bancrofti'

A fomite is any nonliving object or substance capable of carrying infectious organisms, such as viruses or bacteria, and hence transferring them from one individual to another. Fomites are associated particularly with hospital-acquired infections, as they are possible routes to pass pathogens between patients. Researchers have discovered that smooth (non-porous) surfaces like doorknobs transmit bacteria and viruses better than porous materials like paper money.

Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Symptoms include some combination of a productive or a dry cough, chest pain, fever, and trouble breathing. Pneumonia may spread via airborne droplets from a cough or sneeze. Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases.

• Measles is a highly contagious infectious disease caused by the measles virus. Symptoms include fever, often greater than 40 °C, cough, runny nose, and inflamed eyes. Measles is an airborne disease which spreads easily through the coughs and sneezes of infected people.
  
• Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Symptoms include a sore throat and fever. In severe cases, a grey or white patch develops in the throat. Diphtheria is usually spread between people by direct contact or through the air (droplet).
  
• Pertussis, commonly known as a Whooping cough is a highly contagious bacterial disease. Symptoms include a runny nose, fever, and cough. Pertussis is caused by the bacterium Bordetella pertussis. It is an airborne disease which spreads easily through the coughs and sneezes of an infected person.
• Gonorrhoea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. Symptoms include burning with urination, discharge from the penis, or testicular pain. Women may have burning with urination, vaginal discharge, vaginal bleeding between periods, or pelvic pain. Hence, it is not transmitted by droplets.

The assertion is true because Taenia (tapeworm) infection is transmitted through undercooked pork containing larvae. The reason is false because the larval stage found in pork is the cysticercus (bladder worm), not the hexacanth (oncosphere), which is the stage found in the egg.

• Droplet infection is an infection transmitted from one individual to another by droplets of moisture expelled from the upper respiratory tract through sneezing or coughing.
• Pneumonia is an inflammation of the parenchyma of the lungs. It is caused by the bacterium Streptococcus pneumoniae.
• Symptoms include a cough with phlegm or pus, fever, chills and difficulty breathing.
• The bacteria that are commonly found in the nose or throat, can infect the lungs if they are inhaled. They may also spread via airborne droplets from a cough or sneeze.
• So, the correct answer is '.Pneumonia ,Streptococcus pnemoniae,Droplet infection'.

Vectors are the organisms, which carries the infectious agents from sick person to another healthy person. For example, mosquito carries malarial parasite from infected person to healthy person. Therefore, option A is correct.

Wuchereria bancrofti is a human parasitic roundworm that is the major cause of lymphatic filariasis. W. bancrofti carries out its lifecycle in two hosts. Humans serve as the definitive host and mosquitos as the intermediate host or vector. The microfilariae are transferred into a vector i.e., female Culex mosquito. Hence, female Culex act as a vector of Wuchereria bancrofti.

• Meningitis is the Inflammation of the brain and spinal cord membranes, typically caused by an infection.
• If the meningitis is caused by bacterium Neisseria meningitidis, it is called as Meningococcal meningitis.
• Symptoms include pain in sudden high fever, severe persistent headache, neck stiffness, nausea or vomiting, joint pains, drowsiness, confusion, etc.
• People spread meningococcal bacteria to other people by sharing respiratory and throat secretions (saliva or spit) when they cough or sneezes.
  
• Hence Meningococcal meningitis infection is transmitted chiefly from person to person.
• So, the correct answer is 'Meningococcal meningitis.

When children play barefoot in pools of dirty water and flood water, they may suffer from Leptospirosis and bilharzia. 

Disease causing microbes can spread through the air. This occurs through the little droplets thrown out by an infected person who sheezes or coughs. Another person standing close by can breathe in these droplets and the microbes infect him also. Diseases which spread like this are common cold, pneumonia and tuberculosis.

So, the correct answer is 'Option 'First line defence - Fever' and 'Third line defence - AMI'.'

There are several ways disease-causing agents get from one person to another:

• Airborne or droplet infection (e.g. colds, flu).
• Animal borne or insect borne infection (e.g. rabies, malaria, Lyme Disease).
• Blood borne infection (e.g. HIV, hepatitis).
• Food borne or water borne infection (e.g. salmonella, giardia).
• Sexually transmitted (e.g. chlamydia, gonorrhea, syphilis).
• Other direct contact (e.g. some kinds of warts, scabies).
• Indirect contact (e.g. colds and flu carried from person to person on dirty tissues, money, door knobs, phones, computer keyboards).

RMP stands for Registered Medical Practitioner, a term used for individuals qualified and registered to practice medicine.