Disease Causative Agents

Particles containing organisms which can remain in air for long time Solution:- Dust particles containing microorganisms which can remain in air for longer duration of time results in airborne transmission. They must be resistant to drying and can survive for long outside the body. Therefore, (b) is the correct answer.

Contamination of drinking water sources by sewage can occur from raw sewage overflow, septic tanks, leaking sewer lines, land application of sludge and partially treated waste water. Sewage is a complex mixture and can contain many types of contaminants. The greatest threats posed to water resources arise from contamination by bacteria, nitrates, metals, trace quantities of toxic materials, and salts. Seepage overflow into drinking water sources can cause disease from the ingestion of microorganisms such as E coli, Giardia, Cryptosporidium, Hepatitis A, and helminths. Septic tanks are enclosures that store and process wastes by bacterial decomposition. Badly constructed percolation systems may allow water to escape without proper treatment.This water may seep to the land surface, runoff into surface water or flow directly into the water table causing waterborne diseases like cholera, typhoid, diarrhoea etc.

Airborne diseases are caused by pathogenic microbes small enough to be discharged from an infected person via coughing, sneezing, laughing and close personal contact or aerosolization of the microbe. The discharged microbes remain suspended in the air on dust particles, respiratory and water droplets. Illness is caused when the microbe is inhaled or contacts mucus membranes or when secretions remaining on a surface are touched. Many common infections can spread by airborne transmission at least in some cases, including: anthrax (inhalational), chicken pox, influenza, measles, smallpox, and tuberculosis.

An airborne disease is any disease that is caused by pathogens and transmitted through the air. Potato virus is transmitted by aphids by sticking to aphid mouth parts (stylet). The virus can be acquired from the infected plant within seconds, and transmitted to a healthy plant very fast. It can also be transmitted mechanically by machinery, tools, and damaging plants while walking through the field. Aphids are by far the most efficient means of transmission.

Salmonella bacteria can be found in food products such as raw poultry, eggs, and beef, and sometimes on unwashed fruit. Food prepared on surfaces that previously were in contact with raw meat or meat products can, in turn, become contaminated with the bacteria. This is called cross-contamination.

Mycoplasma mycoides is the causative agent of Contagious Bovine Pleuropneumonia (CBPP), a serious respiratory disease in cattle.

Creutzfeldt-Jakob disease (CJD) is caused by infectious protein particle called prions.

Cholera is caused by vibriocholerae bacteria and typhoid is caused by salmonella typhi bacteria.

Dysentery can be caused by bacteria, virus, or other parasites which cause inflammation of intestines accompanied by bloody diarrhoea.

Pathogens are the type of organisms which cause diseases, by attacking on the defense mechanism of body.

1. Diarrhea is the condition of having at least three loose or liquid bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss.
2.  Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behavior. This can progress to decreased urination, loss of skin color, a fast heart rate and a decrease in responsiveness as it becomes more severe. 
3. These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected. Hence, the mode of infection of diarrhea is food.
   

The first human death from the H5N1 avian influenza virus was recorded in Hong Kong in 1997.

Koch's postulate designed the causative relationship between a microbe and a disease.  Viruses are obligate intracellular parasites so they cannot be grown on artificial media.