Reservoirs of Disease

1. Reservoirs of Disease By: Allison Smock

2. What exactly are reservoirs of disease? • Animate or inanimate sources which harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. • Reservoirs are distinguished from vectors and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks.

3. Categories of Disease Reservoirs • Reservoir- Refers to the place in nature where a disease normally lives or is always found in significant numbers • Zoonoses- Reservoir of diseases in animals (usually other than humans however, don't be too offended but epidemiologists consider humans just another animal), that can be transmitted to humans (e.g. Ebola, Lassa fever, Lyme disease and probably the original HIV; now the HIV reservoir is humans). These are the most common types of reservoirs since pathogens are pathogens because they metabolize other living organisms who fail to appreciate their activities. Rabies is a classical case of a nonhuman animal reservoir. • Inanimate- With few exception, inanimate reservoirs are secondary or accidental reservoirs. For example, you can catch a cold by handling a virus-laden Kleenex or a doorknob infected by someone's spit or snot with the flu virus, but the main reservoir of cold and flue are infected persons. The soil serves as a reservoir for pathogens like #Clostridium perfringens, Clostridium tetaniand Bacillusanthrax spores, but the ultimate reservoirs again are the hosts they reproduce in. #Clostridium botulinum, as well as some fungal diseases, have their reservoirs in the soil and mostly live in the soil, probably on dead matter; that is, living organisms are rare,ﾊaccidental hosts.

4. Terms associated with Disease Reservoirs • Disease vector: Invertebrates or non-human vertebrates, which transmit infective organisms from one host to another. • Fomites: Inanimate objects that carry pathogenic microorganisms and thus can serve as the source of infection. Microorganisms typically survive on fomites for minutes or hours. Common fomites include clothing, tissue paper, hairbrushes, and cooking and eating utensils.

5. Terms Continued • Carrier State: The condition of harboring an infective organism without manifesting symptoms of infection. The organism must be readily transmissible to another susceptible host • Transplantation disease transmission: transmission of infectious disease as a consequence of transplant procedures; this includes introduction of a new pathogen from a source animal into a human or other species or from a human introduced into another species; includes diseases transmitted through transplantation of cells, tissues, organs, or blood transfusion, etc.

6. Animals and Disease Reservoirs Animals can act as disease reservoirs. Deer carry the bacteria that causes lyme disease and can infect humans. Ticks feed off the blood of deer and mice and then transfer the disease to us when they latch onto us and bite us. HIV, Ebola, SARS - any of the world's most horrifying diseases are caused by animal viruses that made the jump to humans.

7. Humans and Disease Reservoirs • TYPHOID FEVER is caused by Salmonella enterica typhi and it typically has a human reservoir. It is usually transmitted by drinking (oral ingestion) or immersion in water that has been contaminated by fecal matter, especially in drinking water.

8. Transmission • Infectious agents may be transmitted through either direct or indirect contact. Direct contact occurs when an individual is infected by contact with the reservoir, for example, by touching an infected person, ingesting infected meat, or being bitten by an infected animal or insect. • Transmission by direct contact also includes inhaling the infectious agent in droplets emitted by sneezing or coughing and contracting the infectious agent through intimate sexual contact. • Some diseases that are transmitted primarily by direct contact with the reservoir include ringworm, AIDS, trichinosis, influenza, rabies, and malaria. • Indirect contact occurs when a pathogen can withstand the environment outside its host for a long period of time before infecting another individual. Inanimate objects that are contaminated by direct contact with the reservoir (for example, a tissue used to wipe the nose of an individual who has a cold or a toy that has been handled by a sick child) may be the indirect contact for a susceptible individual. Ingesting food and beverages contaminated by contact with a disease reservoir is another example of disease transmission by indirect contact.

10. Works Cited • www.biology-online.org/dictionary/Disease_reservoirs • http://www.use.hcn.com.au/subject.%60Disease%20Reservoirs%60/home.html • http://www.wrongdiagnosis.com/medical/disease_reservoir.htm • http://images.google.com/imgres?imgurl=http://graphics8.nytimes.com/images/2007/04/24/science/24bees.hat.xlarge1.jpg&imgrefurl=http://wdin.blogspot.com/2007_ • =2&tbnid=i2jVN4CoaAK39M:&tbnh=79&tbnw=135&prev=/images%3Fq%3D%2Bbee%2Bdisease%2Breservoirs.%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG • http://images.google.com/imgres?imgurl=http://www.smm.org/buzz/media/images/Kemperman.img_assist_custom.jpg&imgrefurl=http://www.smm.org/buzz/buzz_tags/ticks&h=185&w=200&sz=17&hl=en&start=25&tbnid=4KhcPIrZ6JXf2M:&tbnh=96&tbnw=104&prev=/images%3Fq%3D%2Bdisease%2Breservoirs.%26start%3D18%26gbv%3D2%26ndsp%3D18%26svnum%3D10%26hl%3Den%26sa%3DN • http://science.education.nih.gov/supplements/nih1/diseases/guide/understanding1.htm • http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/Chap14.html#Reservoir