Disease Reservoir and Transmission PDF

Disease reservoir and transmission Luis Pablo Hervé Claude Assistant Professor of Veterinary Public Health and Epidemiology Objectives Learn the terminology used to describe disease transmission Define and identify a reservoir of disease Understand the modes/routes of t...

Disease reservoir and transmission Luis Pablo Hervé Claude Assistant Professor of Veterinary Public Health and Epidemiology Objectives Learn the terminology used to describe disease transmission Define and identify a reservoir of disease Understand the modes/routes of transmission of disease Define determinants that increase the likelihood of disease transmission Chain of transmission Chain of infection https://www.ottawapublichealth.ca/en/professionals-and-partners/chain-of-infection.aspx  Exposure and Transmission Exposure: Introduction of a doesn'tmeantransmission new pathogen into a susceptible population. Reservoir Susceptible Disease population population Epidemic Transmission: Adoption, 8fading 19 in establishment, and dissemination the susceptible population. Requires a pathogen that can adapt to, and transmit between, these hosts. Chain of transmission  are What is a reservoir? are Habitat or populations in which an infectious agent normally lives, grows and multiplies Maintain pathogens over time Different strategies to survive in the reservoir  Born Key Points about animal reservoirs Reservoir does not mean not ill. If asymptomatic: then we consider it a carrier Not all sick animals are reservoirs An individual can be killed by the agent, but the population maintains the agent  J M S reservior What are the reservoirs? Felines Measles Feline Leukemia humans Virus soil chicken reptiles humans Legionella Salmonella Mumps spp. soil water rodents Coccidioides Leptospirosis wheerfallingabout Bovine buffalo µ Rabies Foot and Mouth Disease Chain of transmission Portal of exit The method the pathogen uses to leave the body of the host Saliva Blood Feces Vaginal secretion Urine Chain of transmission  Diagram of transmission Vertical Horizontal Transplacental, Transovarial Perinatal fecundation & eggs Direct Indirect Contact Droplet/ Airborne Vehicle Vector Common vehicle Fomite Biological Mechanical  Diagram of transmission Vertical Transplacental, Transovarial Perinatal fecundation & eggs  Vertical transmission: Infection at fecundation and transplacental Infection at fecundation: virus can attach to spermatozoa or oocyte Transplacental infection: in utero, through the placenta placental structuresare differentfordiff int hesediagrams https://www.researchgate.net/figure/Classification-of-placentas-based-on-histological-assessment-of-the-maternal- chorion_fig1_273780913 Vertical transmission: Transmission to eggs Transmission of the pathogen agent during the egg development Salmonella enterica Serovar Gallinarum Mycoplasma Avian leukosis viruses Avian encephalomyelitis  onlyinarthropods Vertical transmission: transovarial Passage of pathogen from the adult female to eggs through the ovaries of an arthropod Egg Larvae Nymph Life stages of ticks Vertical transmission: Perinatal 1) At parturition (Enzootic bovine leucosis, HIV) 2) Through the colostrum/milk Transmission diagram Horizontal Direct Indirect Horizontal transmission: direct vs. indirect Direct transmission Directly from the Limited space reservoir to a Without intermediary susceptible host Short time period Indirect transmission Via any sort of Distance intermediary either Intermediary animate or inanimate Longer time period  Transmission diagram Horizontal Direct Contact Droplet/ Airborne Skin Mucous membranes Brutal Direct by contact Skin contact Microsporum canis Francisella tularensis  Direct by contact Mucous membrane contact: Sexual transmission (Brucella, HIV), Saliva contact Brutal contact Direct by air/water Direct projection (droplet spread) Wet, large, and short-range aerosols, like sneezing, coughing or talking Airborne Considered to be a form of direct Droplet Airborne transmission because disease agents do SARS-CoV Influenza virus not generally survive for extended periods within aerosolized particles. Waterborne (for aquatic animals only): Through the gills  Transmission diagram Horizontal Indirect Vehicle Common vehicle Fomite  Indirect: Vehicle Vehicle: An inanimate object which serves to communicate disease Common Vehicle Fomites Water Objects that can be Food contaminated and transmit Soil disease on a limited scale … Transmission diagram Horizontal Indirect Vector Biological Mechanical Indirect: Vectors Vector: Arthropods who carry and transmit pathogens Mechanical vector: an animal that carries a pathogen from one host to another without being infected itself Biological vector: the pathogen undergoes changes or multiplies while in the vector  ex e coli fly feces carries onlegs infected fly isn't itself Mechanical Biological Chain of transmission Portal of entry The method the pathogen uses to enter the body of the susceptible person or animal Most of the pathogens cannot go through the intact skin Animals are well protected (See microanatomy) Chain of transmission Susceptible host Member of a population who is at risk of becoming infected by a disease (Epidemiological definition) What is important? Chain of infection Portal of entry and exit: how the pathogen can enter and exit and the most efficient portal of entry Recognize all the different ways of transmission Reservoir characteristics What is a susceptible host