Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Infection control wikipedia , lookup
Neglected tropical diseases wikipedia , lookup
Schistosomiasis wikipedia , lookup
Schistosoma mansoni wikipedia , lookup
Sociality and disease transmission wikipedia , lookup
Eradication of infectious diseases wikipedia , lookup
Globalization and disease wikipedia , lookup
Welcome to Diseases and Parasites of Aquatic Organisms MARI-5315 Dr. Joe Fox January 20, 2004 Description of Syllabus Course Number and Title: MARI-5315, Diseases and Parasites of Aquatic Organisms Lecture Time/Location: Tuesdays, 4:307:00 in CS 103 Lab Time/Location: 7:00-9:00 CS 234 Instructor: Dr. Joe Fox, CS 251, TW10-12 Description of Syllabus Exposure to fundamental and current disease/health issues pertaining to the production of aquaculture crops Prevention of diseases via practical diagnosis and real-world decision making Covers: anatomy and physiology, immunology, virology, bacterial diseases, nutritional diseases, parasitology, mycoses, larval diseases and general health management Syllabus No textbook applicable (course too broad) All other readings will be on reserve or in my office course will consist of a weekly two-hour lecture followed by a two-hour practical lab lectures are on the mariculture home page (www.sci.tamucc.edu/pals/maric/Index/WEBPAGE/mari1.htm) you will need a lab coat (we’ll give you one) no open-toed shoes in lab labs will often require observation and checking on samples outside class period Syllabus: lecture outline Lecture 1 2 3 4 5 Date 1/20 1/27 2/3 2/10 2/17 2/24 3/2 3/9 3/16 3/23 6 7 8 9 10 3/30 4/6 4/13 4/20 4/27 5/4 Topic Introduction to Disease, Part 1 Introduction to Disease, Part 2 Immune Response in Aquaculture Animals Diseases of a Non-infectious Nature Exam 1 Common Viral Pathogens of Aquaculture Organisms, Part 1 Common Viral Pathogens of Aquaculture Organisms, Part 2 Common Bacterial Pathogens of Aquaculture Orgnaisms, Part 1 Spring Break – No classes. Common Bacterial Pathogens of Aquaculture Organisms, Part 2 Probiotic Bacteria Exam 2 Molds and Fungi Protozoans and Parasites Aquaculture Health Programs Design of High Health Facilities Syllabus: lab outline Lab 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Date 1/20 1/27 2/3 2/10 2/17 2/24 3/2 3/9 3/16 3/23 3/30 4/6 4/13 4/20 4/27 5/4 Activity Lab safety; Fish internal/external anatomy Shrimp internal/external anatomy Clinical work-up Post mortem techniques ELISA PCR, Part 1 PCR, Part 2 Basic microbiological techniques Spring Break – No lab Vibrio sp. enumeration Bacterial pathogen identification, classical Bacterial pathogen identification, rapid methods Aquaculture parasites, microscopic review Aquaculture parasites, necropsy Review for lab final practical exam Lab Final Practical Exam Syllabus: grading criteria Evaluation Date % of total grade Exam 1 2/17/04 16.67 Exam 2 4/6/04 16.67 Exam 3 5/7/04 16.67 Lab final exam 5/4/04 17.50 Lab reports Due at start of following lab period 32.50 Note: all assignments are due on time, unless w/prior consent of instructor; Lecture 1: Introduction to Disease What is disease? Types of diseases Dynamics of infectious disease Epizootiology of infectious diseases What you have to do to be a disease agent Disease reservoirs Transmission The host Stages in an epizootic What is Disease? Definition: any alteration of the body or one of its organs so as to disturb normal physiological function opposite of health = unhealthy or dysfunctional Why are diseases important to aquaculture? 1990: WSSV, a virus, devastates shrimp culture in China, $600 million lost 1971: Flexibacter columnaris, a bacterium, kills 14 million wild fish in Klamath Lake the Idaho trout industry loses 10 cents on every dollar made to disease (death, weight loss) future of finfish and shrimp culture may hinge on our ability to control vibriosis Types of Diseases 1) infectious: diseases due to the action of microorganisms (animal or plant): viruses: CCV, WSSV, TSV, YHV bacteria: Vibrio sp. protozoans metazoans fungi: Saprolegnia sp. crustaceans: O. Isopoda Types of Diseases 2) non-infectious: diseases due to non-living causes (environmental, other) even a moderately adverse environment can lead to stress, stress leads to epizootics a very adverse environment can cause disease and mortalities directly (e.g., nitrogen gas bubble disease, brown blood disease) the “other” category refers to nutritional, genetic and developmental diseases Types of Diseases 3) treatable vs. non-treatable non-treatable diseases are some of the worst include pathogens such as viruses, drug-resistant bacteria, myxozoans white spot syndrome virus (shrimp) has no known treatment Vibrio sp.: because of rampant over-use of antibiotics in Central America, South America, new, more virulent strains are developing Dynamics of Infectious Diseases First mode of infection demonstrated by Robert Koch (1876) and his work with Bacillus anthracis (anthrax) reached epidemic proportions in cattle, sheep and other domesticated animals also can occur in man (as we are well aware!) Koch showed that a bacterium caused the disease by using the following method: Koch’s Method (Postulates) 1) find the organism common to all infected animals, demonstrate its absence in healthy ones 2) isolate the organism in pure culture 3) reproduce the disease in suitable experimental animals 4) reisolate the same organism from experimentally infected animals Dynamics of Disease: Germ Theory Koch’s work lead to what is known as the germ theory: germs cause disease if you have germs you are diseased Renes Dubos (1955) refined the concept in the following statement: “There are many situations in which the microbe is a constant and ubiquitous component of the environment but causes disease only when some weakening of the patient by another factor allows infection to proceed unrestrained, at least for a while. Theories of disease must account for the surprising fact that, in any community, a large percentage of healthy and normal individuals continually harbor potentially pathogenic microbes without suffering any symptoms or lesions.” Dynamics of Disease: stress Definition: any stimulus (physical, chemical or environmental) which tends to disrupt homeostasis in an animal. The animal must then expend more energy to maintain homeostasis: less energy to combat disease Aquatic organisms are fundamentally different from terrestrials: they are immersed in their environment, can’t go somewhere else some disease agents are almost always present in the water (ubiquitous) examples: Aeromonas sp., Pseudomonas sp., Vibrio sp. Dynamics of Infectious Disease: how it occurs Three-set model: 1. 2. 3. susceptible host pathogenic agent environment unfavorable to host/favorable to agent exceptions??: extremely large numbers of bacteria, extremely virulent agent stress throws a wrench into it all Dynamics of Infectious Diseases infection parasitism disease (infection can result from parasitism, but neither necessarily results in disease symbiosis: any association between 2 species involving an exchange of matter and energy commensalism: symbiosis in which one partner benefits, the other is neutral parasitism: symbiosis in which the parasite (usually smaller) is metabolically dependent on the host (larger); some harm intuitive, but not necessary Epizootiology of Infectious Diseases: terminology epidemiology: branch of medicine describing occurrence, distribution and types of diseases in populations of animals at distinct periods of time and at particular places (usually refers to humans) epizootiology: same as above (non-human) epidemiology is the study of the who, what, when, where, how and why of disease outbreaks Epizootiology of Disease: outbreak terminology enzootic vs. epizootic (endemic vs. epidemic) incidence: frequency of disease in a population over time in relation to the population in which it occurs (cases/yr) rate: number of new cases per number of population (per thousand) prevalence: the expression of the frequency of a disease at a particular point in time in relation to the population in which it occurs (%) proportion: number affected/population mortality: the percentage expression of the frequency of deaths over a period of time in the total population (not a rate, a proportion) How to Become a Disease Agent: 6 Commandments of Parasitism 1. 2. 3. 4. 5. 6. 7. Find a proper host Somehow get in or access inside Find a home Be fruitful and multiply Get out once done or developed Be transmitted to a new host all this obviously involves specificity in the host:parasite relationship Host:Parasite Specificity Specificity is required for steps 1 and 3, above (find a proper host, find a home inside) host specificity example: Shasta rainbow trout are highly susceptible to Ceratomyxa shasta while Crystal Lake individuals are completely resistant reason: physiological specificity (the host must meet all of the metabolic requirements of the agent without destroying it immunologically) Host:Parasite Specificity Another example: Why are centrarchids infected with black spot metacercariae while walleyes aren’t? Answer: ecological specificity -- the host and agent must overlap in time and space Another type of specificity: tissue specificity For Next Time…. Will continue with introduction to disease Check books on reserve in the library…. Lab tonight: fish interna/exeternal anatomy, we provide dissection kits, etc. Today in MARI-5315 (Jan 20, 2004) Texts on reserve in library (3 hr max check-out; don’t fail to turn them in on time; $3.00/hr overdue fine) Lab tonight: we provide dissection kits Lecture: more on basics of disease Potential for Disease via Infection: contributors 1. 2. 3. 4. 5. 6. number of organisms (overwhelming) infectivity (ability to get in) virulence (ability to produce disease) susceptibility of the host agent’s ability to overcome host’s defenses level of stress (REM!) probablility of disease (Theobald Smith Model) = (# agents x virulence of agents)÷(resistance of host) Possible Fates of an Agent within its Host 1. host dies: agent proliferates, overwhelms host, good parasites don’t do this, $$$$$ 2. host lives: largely dependent on stress host gets sick, but recovers (defense worked) host doesn’t get sick (agent not virulent, wrong host) survivors: agent either eliminated or carrier state established (host infected, but no obvious disease, big problem) latent (not easily observed) patent (ongoing/observable) Mortality Curves: bell shaped Infectious agent or toxic substance moves into the population and then, after time, no longer affects events in population. Transmission is horizontal with width of curve proportional to incubation time and period of communicability. 25 Mortality Rate (fish/wk) 20 15 10 5 0 1 2 3 4 5 6 7 8 9 Agent??: typically bacterial Week Mortality Curves: sigmoidal Slight deviation from bell-shaped curve due to lag period in course of disease (lag phase of growth) Also, periods in which the disease is not communicable. 25 Mortality Rate (fish/wk) 20 15 10 5 lag 0 1 2 3 4 5 6 7 8 9 Week Agent??: typically bacterial Mortality Curves: point source Population at risk was exposed to agent at a single point in time. All susceptible members affected. Highly virulent infectious type disease of toxic agent Exposure to toxin. 25 Mortality Rate (fish/wk) 20 15 10 5 0 1 2 3 4 5 6 7 8 9 Agent??: chemical, viral Week Indicates exposure over a long period of time slow incubation slow transmission Agent??: possibly nutritional Mortality Rate (fish/wk) Mortality Curves: plateaushaped 18 16 14 12 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 Week Mortality Curves: multiple spiked Due to frequent but intermittent exposure to disease agent Data usually or eventually indicate plateau effect Must take care re frequency of sample 14 Mortality Rate (fish/wk) 12 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 Week Agent??: physical parameter (e.g., low D.O.) Theoretical Cumulative Mortality Patterns Degree of Infection Acute: high degree of mortality in short period of time, external signs might be completely lacking (e.g., CCV, IHNV, TSV, WSSV) Chronic: gradual mortality, difficult to detect a peak (Aeromonas septicemia, furunculosis) Latent: disease agent present, but host shows no outward sign, little or no mortality, sometimes associated with secondary pathogen/infection (CCV and Edwardsiella ictaluri) The Reservoir Concept reservoir: the sum of all sources of the agent, the natural habitat of the agent, where the agent comes from The size of the reservoir is proportional to the chance of spread of a pathogen transient reservoir: situation in which the epizootic displays a seasonal pattern of either cases or carriers permanent reservoir: usually associated with disease in which chronic carriers are shown good example: water supply, itself Transmission Definition: mode of transfer of disease to a new host Method 1) direct transmission: from one host to another, either a) vertically or b) horizontally a) vertical transmission: from parent to offspring via male (Girodactylus, trematode in pipefish) via female (IHN) b) horizontal transmission: from one member of a population to another, one offspring to another contact: typically water borne (e.g., fish to fish) ingestion of agent or of infected aquatic Transmission Method 2) indirect transmission: infection via an inanimate vehicle, vector or intermediate host vehicle: an inanimate object such as handling equipment (nets, waders, etc.) or feed (e.g., aflatoxin) vector or intermediate host: animate object mechanical: vector is not essential to life cycle of agent biological: agent spends some part of life cycle in vector (e.g., water boatman and WSSV) Disease Transmission: getting in the door Portals of entry, not as easy as they sound: 1. 2. 3. 4. ingestion: e.g., Ceratomyxa shasta, BKD, Myxobolus cerebralis gill lamellae: e.g., Schizamoeba salmonis, Ichthyobodo necatur lesions: bacteria (Vibrio sp.), fungi (Saprolegnia sp.) active penetration: some metazoans, dinoflagellates The Host The ability of a host to acquire a disease agent and demonstrate disease symptoms can be expressed both qualitatively and quantitatively qualitatively: resistance (ability of a host to withstand the effects of an agent; e.g., Litopenaeus stylirostris to TSV) quantitatively: susceptibility (a measure of the host’s ability to tolerate an agent) Resistance: Primary Factors Physical barriers, inflammation, natural immunity, acquired immunity 1. physical barriers: refers to innate characteristic of animal body to penetration (e.g., mucous slime layer, intact skin, mucous membranes, exoskeleton) for fish, the mucous slime layer itself displays an immune response (phagocytic properties, antibodies) Resistance: Primary Factors 2. inflammation: basic response to any wound, designed to seal off the area and reduce further infection/damage manifestations (humans) include swelling, reddening, loss of function, heat, pain manifestations (fish) possibly include heat and pain histological changes: local edema (swelling); infiltration of neutrophils (type of white blood cell produced in bone marrow) , lymphocytes (lymph proteins), macrophages; fibroplasia (formation of fibrous tissue in wounds) Resistance: Primary Factors 3) Immune Response 1. 2. natural immunity: inherited (discussed in detail later) acquired immunity: either active or passive a) b) active: obtains antibody via contact with antigen passive: antibody obtained via donor (vaccination) discussed in following lecture Resistance: secondary factors Secondary factors associated with disease resistance are either environmental in nature or somatic (associated with host, itself) environmental factors: mainly stress resulting from deviation in temperature, dissolved oxygen, ammonia; inadequate nutrition; mechanical, etc. somatic factors: age, sex, species (e.g., IPN affects only largest fry, potential for exposure, immune experience via exposure, black spermataphore, TSV) Stages in Epizootic REM: epizootic is an outbreak of disease 1. incubatory: agent has penetrated host barrier, found home and multiplying 2. clinical or subclinical: host adversely affected (manifestations) depression (reduced activity) color change interrupted feeding behavior body contortions respiratory change mortality Stages in Epizootic 3. terminal: host either dies or recovers exception: in some very acute, highly pathogenic diseases (e.g., MBV) death may occur so fast that obvious signs don’t develop NEXT: Immune Response in Aquaculture Organisms Today’s Lab: Shrimp External/Internal Anatomy External anatomy: 30 minutes Internal anatomy: 60 minutes Read your protocol!!