EpiLEC Session 5 Describing Disease PDF

Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: _____...

Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Lesson title: Describing Disease in Populations Materials: - Paper and Pen Lesson Objectives: - Desktop Computer or Smart Phone with At the end of this period, the students are expected to: internet access 1. describe occurrence disease with reference to their - pdf file copy of temporal and spatial patterns. reference book 2. differentiate epidemic, endemic, sporadic and pandemic. Reference: Thrusfield, Michael (1995). Veterinary Epidemiology. 1. Third edition. Oxford: Blackwell Science Ltd. Productivity Tip: Speak to your teacher right away when you struggle to understand new concepts A. LESSON PREVIEW/REVIEW 1) Introduction (2 mins) At this point, it has already been established that cause precedes effect thereby disease does not occur in random fashion. Further, a disease can be due to a complex interaction between host, agent and environmental factors. In this session, we will learn to describe a disease in populations into four classifications (sporadic, endemic, epidemic, pandemic) with respect to three essential descriptive variables (factors): a) structure of both the diseased and healthy population (Which animals are affected?); b) time of occurrence and duration of the disease under investigation (when did the animals become infected?); and c) geographical distribution of the disease and population (Where are the affected animals located?). We also aim to relate the current Covid-19 pandemic to our understanding of epidemiologic concepts. FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ 2) Activity 1: What I Know Chart, part 1 (3 mins) Consider the following questions on the table below. On the first column briefly write in bullet points what you know about the question. Meanwhile, leave the third column blank until you have completed going through the whole lesson. What I Know Questions: What I Learned (Activity 4) 1. What do “clustering” of cases of a disease in time and space mean? 2. What is your understanding on the terms “outbreak” and “epidemic”? 3. When will a disease become endemic in a population? B.MAIN LESSON 1) Activity 2: Content Notes (20 mins) Read the contents in pages 46-49 of Veterinary Epidemiology Third Edition by Thrusfield, Michael (1995). Describing Disease Occurrence in the Population The level of disease in a population depends often on an interplay of three factors: Individual factors: what types of individuals tend to develop disease and who tends to be spared? Temporal factors: how does disease frequency change over time, and what other factors are associated with those changes? Spatial factors: where is the disease especially common or rare, and what is different about those places? Individual Individuals can be grouped or distinguished on several characteristics: age, sex, breed, coat color and so on. An important component of epidemiological research is aimed at determining the influence of individual characteristics on the risk of disease. FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ What is an epidemiological unit? Determining the epidemiological unit is essential in disease outbreak investigation. The epidemiological unit refers to a group of animals with a defined epidemiological relationship that share approximately the same likelihood of exposure to a pathogen. This may be because they share a common environment (e.g. animals in a pen), or because of common management practices. Usually, this is a herd or a flock. However, an epidemiological unit may also refer to groups such as animals belonging to residents of a village, or animals sharing a communal animal handling facility. The epidemiological relationship may differ from disease to disease, or even strain to strain of the pathogen. Timing of Disease Events The basic premise of epidemiology is that disease does not occur randomly over time or in space in a population. The timing of onset of cases rather follow one of three patterns: ▪ Cases may occur sporadically, i.e. they do not seem to be associated with any other identifiable factor, nor with other; ▪ Cases may occur regularly. The disease is often referred to as being endemic. It virtually always occurs, often at low levels; ▪ Cases may occur in clusters, a pattern typical of outbreaks or epidemics. Place The spatial pattern of disease is typically a consequence of environmental factors. Environmental factors include aspects of climate (temperature, humidity, rainfall) as well as aspects of animal management (management of animals in a certain area of a country may result in high rates of disease that may not be seen in other areas). Endemic o Used to describe: a. the usual frequency of occurrence of a disease in a population; b. the constant presence of a disease in a population. o levels of disease do not exhibit wide fluctuations over time o implies a stable state; if a disease is well understood the endemic level is often predictable o clustered in space but not in time FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ o a disease may be endemic in a population at any frequency level, provided that it occurs with predictable regularity o Endemic diseases described according to their frequency of occurrence: Hyperendemic = affects a high proportion of the population-at-risk Mesoendemic = affects a moderate proportion of the population-at-risk Hypoendemic = affects a small proportion of the population-at-risk Epidemic o Originally used to describe a sudden, usually unpredictable increase in the number of cases of an infectious disease in a population. o In modern epidemiology: it describes an occurrence of an infectious or non- infectious disease to a level in excess of the expected level. o clustered in time and space o occurs when there is a rapid increase in the level of disease in a population. o usually heralded by an exponential rise in the number of cases in time and a subsequent decline as susceptible animals are exhausted. o Epidemics may arise from the introduction of a novel pathogen (or strain) to a previously unexposed (naive) population or as a result of the re-growth of susceptible numbers sometime after a previous epidemic due to the same infectious agent. o When epidemics occur, the population must have been subjected to one or more factors that were not present previously o Note that a disease may be epidemic even at a low frequency of occurrence, provided that it occurs in excess of its expected frequency. Why do epidemics occur? Some reasons of epidemics due to infectious disease agents are: o Recent introduction of the agent into a susceptible population o Recent introduction of a susceptible group of animals into an infected area o Recent increase in virulence or amount of agent o Change in the mode of transmission of the agent o Change in host susceptibility or response to the agent o Factors causing increased host exposure or involving new portal of entry. Pandemic o Refers to a widespread epidemic that usually affects a large proportion of the population. o Many countries may be affected o Examples of Human Pandemic: serious human pandemic of plague (the Black Death) in the Middle Ages, Cholera in the 19th Century, influenza soon after the First World War, Corona Virus (Covid-19) FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ o Examples of Animal Pandemic: African Swine Fever (ASF), Avian Influenza (Bird Flu) Sporadic Occurrence o Occurs irregularly and haphazardly o Implies that appropriate circumstances have occurred locally, producing small, localized outbreaks. o Sporadic disease is normally absent from a population but which can occur in that population, although rarely and without predictable regularity. o Sporadic can indicate either a single case or a cluster of cases of a disease (without obvious disease) that is not normally present in an area. Notifiable diseases Source: OIE (2011). Terrestrial Animal Health Code. Download in: www.oie.int. World Organisation for Animal Health (OIE), Glossary, Chapter 1.1 and Chapter 1.2. As defined by the OIE, notifiable disease means a disease listed by the Veterinary Authority, and that, as soon as detected or suspected, should be brought to the attention of this Authority, in accordance with national regulations. Veterinary Authority is the Governmental Authority of an OIE Member, comprising veterinarians, other professionals and para-professionals, having the responsibility and competence for ensuring or supervising the implementation of animal health and welfare measures, international veterinary certification and other standards and recommendations in the Terrestrial Code in the whole territory. Notification means the procedure by which: a) the Veterinary Authority informs the Headquarters, b) the Headquarters inform the Veterinary Authority, of the occurrence of an outbreak of disease or infection, according to the provisions of the Terrestrial Code. World Organisation for Animal health (OIE) publishes a list of diseases, infections and infestations. The list is reviewed on a regular basis and modifications on the list are adopted by the OIE World Assembly of Delegates during General Session. List comes into force every January 1 World Animal Health Information WAHIS) Database. The criteria for the inclusion of a disease in the OIE List are: International spread, Zoonotic Potential, Significant Spread within Naïve Populations, and Emerging Diseases. Basic criteria Parameters (at least one 'yes' answer means that the criterion has been met) International Spread Has international spread been proven on three or more occasions? OR Are more than three countries with populations of susceptible FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ animals free of the disease or facing impending freedom (based on the relevant provisions of the Terrestrial Code particularly those contained in Chapter 1.4.)? OR Do OIE annual reports indicate that a significant number of countries with susceptible populations have reported absence of the disease for several consecutive years? Zoonotic Potential Has transmission to humans been proven? (with the exception of artificial circumstances) AND Is human infection associated with severe consequences? (death or prolonged illness) Significant Spread Does the disease exhibit significant mortality at the level of a within Naïve country or a zone? OR Populations Does the disease exhibit significant morbidity at the level of a country or a zone? Emerging Diseases Are there apparent zoonotic properties or is there a rapid spread? The OIE list of notifiable diseases are categorized into multiple species diseases and diseases in specific species (cattle; sheep and goat; equine; swine; avian; lagomorph; bee; and other diseases) Meanwhile, the Philippines Bureau of Animal Industry (BAI) also prepares a list of reportable diseases. Further, livestock diseases are group into four categories by national control priorities. Class I diseases, being in the priority list have government budgetary allocation for control and prevention. A disease is not fixed into a particular class. It can be re- classified based on the criteria. Priority Disease Characteristics Class I Dramatic, economically disruptive, and frequently epidemic infections producing high mortality or especially serious morbidity (plus zoonotic infections of major public health importance) that are currently present in a country. II Above groups of infections currently absent from a country but which pose serious economic or health threats as potential invaders. III Other well-defined but usually less dramatic, endemic, or sporadically epidemic infectious or non-infectious diseases of demonstrated or assumed economic and / or public health consequences. IV More poorly-defined and locally variable disease complexes, often clearly multicausal, and responsible for substantial but sometimes insidious performance and reproduction inefficiencies FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ 2) Activity 3: Skill-building Activities A. Temporal and Spatial Distribution of Disease Complete the table. Under the corresponding column, put a (+) sign if the disease description on the first column is limited in time (Temporal) or space (Spatial). Use a (-) sign if not limited. The term “limited” also means the disease is “clustered,” occurring only on a specific time and particular place. Description Temporal Spatial EPIDEMIC ENDEMIC SPORADIC PANDEMIC B. List two animal diseases currently classified under priority Class I in the Philippines. 3) Activity 4: What I Know Chart, part 2 (2 mins) You are about to complete the lesson at this point. To refresh what you have learned, review back the questions in the What I Know Chart from Activity 1 and write your answers to the questions based on what you now know in the third column of the chart. 4) Activity 5: Check for Understanding (5 mins) Take Quiz Uploaded in Google Classroom C. LESSON WRAP-UP 1) Activity 6: Thinking about Learning (5 mins) You are done with this session! Let’s track your progress. Shade the session numbers you have completed. P1 P2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ ☐ FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ 2) My learning targets: Complete the table below. Record your scores, learning experience for the session and deliberately plan for the next session. Date Learning Target/Topic Scores Action Plan What session# did you do? What were the What were What contributed to the quality of your performance What’s the date learning targets? What activities did you your scores in today? What will you do next session to maintain today? do? the activities? your performance or improve it? FAQ What’s the difference between a pandemic, an epidemic, endemic, and an outbreak? Epidemic vs. Pandemic A simple way to know the difference between an epidemic and a pandemic is to remember the “P” in pandemic, which means a pandemic has a passport. A pandemic is an epidemic that travels. For example, when COVID-19 was limited to Wuhan, China, it was an epidemic. The geographical spread turned it into a pandemic. Epidemic vs. Endemic An epidemic is actively spreading; new cases of the disease substantially exceed what is expected. More broadly, it’s used to describe any problem that’s out of control, An epidemic is often localized to a region, but the number of those infected in that region is significantly higher than normal. Endemics, on the other hand, are a constant presence in a specific location. FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH  Course Code: PHLT 2 Veterinary Epidemiology Student’s Activity sheet for Session #5 Name: _____________________________________________________________ Class number: _______ Section: ____________ Schedule: ________________________________________ Date: ________________ Endemic vs. Outbreak Outbreak means the occurrence of one or more cases in an epidemiological unit. An outbreak is a greater-than-anticipated increase in the number of endemic cases. It can also be a single case in a new area. If it’s not quickly controlled, an outbreak can become an epidemic. An endemic can lead to an outbreak, and an outbreak can happen anywhere. Key to Correction to Activity 3 A. Temporal and Spatial Distribution of Disease Description Temporal Spatial EPIDEMIC ENDEMIC SPORADIC PANDEMIC B. Priority class of current diseases Priority Current Examples Class I Rabies, African Swine Fever, Avian influenza, Classical Swine Fever, Newcastle disease, II Swine Flu, African Horse Sickness, Nipah virus encephalitis, Foot and Mouth Disease, Rinderpest, Leishmaniosis III Anthrax, Schistosomiasis, Brucello is, Japanese Encephalitis, Surra, Hemorrhagic Septicemia, Caprine arthritis / encephalitis, Cysticercosis (Taeniasis), Equine Infectious Anemia, IV Porcine Respiratory Reproductive Syndrome (PRRS), Porcine Epidemic Disease (PED), Transmissible gastroenteritis, Notes: a) Rabies is the only disease of pet animals (dogs / cats) listed in priority class 1. b) Philippines is now free of Rinderpest and Foot and Mouth Disease FLM 1.0 Prepared by Daniel C. Ventura, Jr., DVM, PhD., DipVPH