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Information about VirologyReview2005

Published on November 19, 2007

Author: Heather


NAVLE REVIEW:  NAVLE REVIEW But first, a few words on the exam PAUL GIBBS NBVME sets both the NAVLE and the PAVE Qualifying Examination:  NBVME sets both the NAVLE and the PAVE Qualifying Examination How does the NBVME function?:  How does the NBVME function? How does the NBVME function?:  How does the NBVME function? The NAVLE is based on a Job Analysis. (The PAVE qualifying examination is not based on a specific analysis as far as I am aware):  The NAVLE is based on a Job Analysis. (The PAVE qualifying examination is not based on a specific analysis as far as I am aware) The Structure of the NAVLE:  The Structure of the NAVLE Activities (Veterinary Practice Roles) I. Data Gathering and Interpretation: 140 (47%) A. Obtain History, Perform Physical Examination, and Evaluate the Environment: 56 (19%) B. Develop a Problem List, and a Differential Diagnosis List: 42 (14%) C. Establish an Accurate Working or Final Diagnosis or Conclusion: 42 (14%) II. Health Maintenance and Problem Management: 140 (47%) A. Identify and Evaluate Prevention, Treatment, and Management Options: 56 (19%) B. Implement Plan of Action: 42 (14%) C. Assess Outcomes: 42 (14%) III. Professional Behavior, Communication, and Practice Management: 20 (7%) Animal Species Canine: 72 (24%) Feline: 72 (24%) Pet Birds: 9 (3%) Other Small Animals: 6 (2%) Bovine: 51 (17%) Porcine: 12 (4%) Ovine/Caprine/Cervidae: 9 (3%) Equine: 51 (17%) Poultry: 6 (2%) Public Health and Food Security: 9 (3%) Non-Species Specific: 3 (1%) Item Writer’s Calendar of Events:  Item Writer’s Calendar of Events February: Workshop on Question Writing in Spring at National Board of Medical Examiners (NBME) Head Quarters in Philadelphia for new writers Review of August qualifying examination (compiled by NBVME and NBME staff from “question bank”) Summer: 50 questions written by midsummer and sent to NBME staff for criticism September: Review of questions in Philadelphia for entry into “question bank” Review of January qualifying examination (compiled by NBVME and NBME staff) Other duties as necessary such as assessing the difficulty of early qualifying examinations (“standard setting”) Preferred Format of the Questions:  Preferred Format of the Questions One-best-answer family Stem Lead In Options Styles to be avoided:  Styles to be avoided Slide11: Virology Review:  Virology Review Paul Gibbs Slide13:  Comparative Shapes of Viruses in the Various Families by Negative Contrast Electron Microscopy Page 9 Veterinary Virology 3. A: Pox B: Papilloma C: Filo D: Reo E: Herpes F: Rhabdo G: Calici H: Bunya I: Orthomyxo Viral capsid:  Viral capsid capsomeres Nucleocapsid (a nucleocapsid without a genome is a capsid) enveloped virus envelope a virion Groups, types, strains and isolates:  Groups, types, strains and isolates Group (e.g. bluetongue viruses) Types – 1 … 24 Group specific antigen Type 1 specific antigen Type 2 specific antigen A strain is a well characterised virus Different strains may have different properties, such as virulence. An isolate refers to the virus recovered from a specific host or location. Type generally means that immunity is not conferred by previous exposure to a different type eg Foot-and-mouth disease Cytopathic effects in cell culture:  Cytopathic effects in cell culture Herpes virus (Bovine herpes mammillitis) Parainfluenza virus (Newcastle Disease) Cell transformation can occur where cells pile up losing the property of cell inhibition. Localized v Systemic:  Localized v Systemic Viral infections can be localized or disseminated (systemic): Localized infections are limited to the sites of entry (epithelial surfaces) of the viruses: a. skin: papillomaviruses cause warts b. respiratory tract: orthomyxoviruses cause influenza; rhinoviruses cause "colds“ in humans c. alimentary tract: entero-, reo-, adeno-, rota-, corona-, and parvoviruses often replicate only in the gastrointestinal tract causing subclinical to severe gastroenteritis. Variations on the theme:  Variations on the theme Inapparent infections: Not all infections lead to clinical disease, most do not Tropism: Some viruses have specific affinity for particular systems, e.g rabies virus is neurotropic Congenital infections: infection of the fetus either in utero or as it is born is not uncommon. No disease may be apparent in the mother e.g. bunya viruses such as Akabane Persistent and latent infection are features associated with several viruses, particularly herpes viruses Slow virus infections occur where the incubation period is prolonged e.g. retro viruses Some virus infections induce immunopathologic disease e.g. eastern equine encephalitis Patterns of virus excretion:  Patterns of virus excretion Acute Recurrent Chronic Disease may not always be apparent Slow clinical signs virus shedding In arbovirus infections no virus excretion occurs ------------------------------------------------------------------------------------------------- In acute infections as much as 7.0 log10 TCID 50 per ml of virus may be excreted Viremias in arbovirus infections can also rise to this level and even higher. Laboratory Techniques:  Laboratory Techniques Diagnostic virology is an expensive service. The laboratory diagnosis of disease caused by viruses and bacteria has many similarities but in most cases the isolation and identification of a virus requires more time and effort. A virology laboratory cannot examine as many samples as its counterpart of similar size in bacteriology.   A virus infection may be confirmed by one or more of six ways:   (a) isolation of virus;  (b) identification of the causal virus in clinical material by electron microscopy; (c) identification of viral antigen or viral induced antigen in clinical material by serology; identification of viral DNA or RNA by molecular probes and polymerase chain reaction (PCR); identification of characteristic cellular pathology; demonstration of an antibody response.   The clinician does not require extensive knowledge of these techniques for him or her to submit the correct samples or to interpret subsequently the laboratory report Virus Detection by Virus Isolation :  Virus Detection by Virus Isolation Cultured cells Cytopathic effect Immunofluorescence (anti-herpesvirus antibody) H & E Virus Isolation: Embryonated Eggs:  Virus Isolation: Embryonated Eggs Used for isolation of influenza viruses by allantoic and amniotic inoculation Historically, used for pox virus isolation Diagnosis by Electron Microscopy - Negative Staining:  Diagnosis by Electron Microscopy - Negative Staining Detail of the Immunomigration Technology:  Detail of the Immunomigration Technology Canine parvo Feline leukemia Identification of Characteristic Histopathology :Immunological detection:  Identification of Characteristic Histopathology :Immunological detection Immuohistochemistry Immunofluorescence Bovine herpesvirus antigens in endothelial cells BHV-1 antigens in neuron In trigeminal ganglion Viral Vaccines on the Market:  Viral Vaccines on the Market With a few exceptions, most vaccines on the market are either inactivated or attenuated (in both cases the virus is grown in cell cultures or embryonated eggs) An example of an inactivated vaccine is Eastern equine encephalomyelitis vaccine An example of an attenuated vaccine is Feline infectious peritonitis vaccine Inactivated Vaccines… Pro’s and Con’s:  Inactivated Vaccines… Pro’s and Con’s Advantages Stability No danger of spread No problem with viral interference Disadvantages Multiple doses often required to protect No local immunity or interferon produced High concentration of antigen causes them to be expensive Immunity often short lived Any non-inactivated virus can cause disease Attenuated Vaccines..Pro’s and Con’s:  Attenuated Vaccines..Pro’s and Con’s Advantages Single dose may be effective Can be given by a natural route stimulating local and systemic immunity Produces long lived immunity Inexpensive Disadvantages Possible reversion to virulence Possible spread to in contact animals and fetus Possible contaminating viruses or mycoplasmas Some reasons why vaccines of either type fail to protect:  Some reasons why vaccines of either type fail to protect Improper use Genetic differences between animals Antigenic differences Blocking by maternal antibodies Administration following infection (Rabies excepted) Disease Eradication through use of Marker Vaccines:  Disease Eradication through use of Marker Vaccines US is eradicating Pseudorabies with gene deleted vaccines Similarly the European Union is working towards eradication of Infectious Bovine Rhinotracheitis (IBR) by application of gene deleted marker vaccines Review of Previous Lectures on Diagnostics and Vaccination:  Review of Previous Lectures on Diagnostics and Vaccination ELISA and PCR are the workhorses of diagnosis Virus isolation valuable but expensive Attenuated live virus vaccines and inactivated vaccines represent most commonly used vaccines Recombinant and marker vaccines now in the market place EPIDEMIOLOGY:  EPIDEMIOLOGY Epidemiology is the study of the determinants, dynamics, and distribution of diseases in a population The risk of infection and/or disease is determined by characteristics of the virus (e.g antigenic variation), the host, and host population (innate and acquired resistance) and behavioral, environmental, and ecological factors that affect virus transmission from one host to another Epidemiology attempts to meld these factors into a unified whole; ! look at it as a branch of population biology Transmission routes of viruses:  Transmission routes of viruses Equivalent diagrams Veterinary Virology 3 pages 94 and 100 Infection Excretion Simplistic Analysis of the Mechanisms for Ensuring the Perpetuation of a virus:  Simplistic Analysis of the Mechanisms for Ensuring the Perpetuation of a virus Short cycle infection Persistent infection Resistance of the virus to environment Involvement of an intermediate host Congenital/vertical transmission Short cycle infection (Acute self limiting):  Short cycle infection (Acute self limiting) High efficiency of transmission Virus excretion of short duration to limit reducton of suceptibles Immunity forces variants; antigenic drift and shift Persistent/Latent Infection:  Persistent/Latent Infection Prolonged period of excretion reduces population necessary for transmission Promotes transmission for non-herding species by venereal route Antibody and virus can co-exist promotes antigenic variation Cow with infectious bovine rhinotracheitis: a herpes infection Resistance of the virus to the environment:  Resistance of the virus to the environment Survival favors fomite transmission or transmission in meat products Virus is not highly infectious, hence number of susceptibles does not fall as animals born compensate for those infected Equine warts: papilloma virus African swine fever virus in salami Perpetuation through Intermediate Host:  Perpetuation through Intermediate Host Intermediate host is often an arthropod in which virus replicates. Infection is persistent and can be passed vertically There may be several animal hosts and several arthropod vectors ! Biological transmission indicates the virus replicates in the arthropod, compare mechanical transmission through contaminated mouthparts West Nile encephalitis Perpetuation through Congenital/Vertical Transmission:  Perpetuation through Congenital/Vertical Transmission Virus may be transmitted transplacentally without necessarily causing either death or fetal abnormalities. Virus may be recognized as “self” i.e. immune tolerance. Viral genome may be integrated into the genome of the gametes (occurs only in poultry as far as we know) Border disease: pestivirus Caprine arthritis encephalopathy: a lentivirus Viral Diseases of Cattle :  Viral Diseases of Cattle How many cattle are there in the USA? About 100 million in USA About 2 million in Florida Bovine Papular Stomatitis:  Bovine Papular Stomatitis Common incidental infection in beef cattle Suckling calves or up to 1 year of age No treatment necessary Diseases Caused by Herpesviruses:  Diseases Caused by Herpesviruses Infectious Bovine Rhinotracheitis (IBR), "Red Nose", Infectious Pustular Vulvovaginitis (IPV), Infectious Pustular Balanoposthitis, (IPB). Malignant Catarrhal Fever, Malignant Head Catarrh, Bovine Malignant Catarrh - African and North American types. Dermopathic Bovine Herpesvirus Infection Allerton Virus Disease, Bovine Herpes Mammillitis; Pseudo- Lumpy Skin Disease Pseudorabies, Mad Itch, Aujezsky's Disease BHV1- Infectious bovine rhinotracheitis:  BHV1- Infectious bovine rhinotracheitis note pustular character of lesions BHV1- Infectious pustular vulvovaginitis and infectious balanoposthitis :  BHV1- Infectious pustular vulvovaginitis and infectious balanoposthitis !Note does not lead to abortion May be the historical form of BHV1 infection BHV1 Infection of the young calf:  BHV1 Infection of the young calf Infection acquired shortly after birth may lead to a systemic infection and death with microscopic lesions throughout the body in addition to respiratory signs Pustular lesions affecting the reticulum Malignant Catarrhal Fever African and North American types:  Malignant Catarrhal Fever African and North American types Caused by a cell associated herpes virus Both types occur in the USA North American type mostly associated with sheep; virus has not been isolated Can occur in American Bison Diseases Caused by Papovaviruses. Bovine Papillomatosis :  Diseases Caused by Papovaviruses. Bovine Papillomatosis Very common infection in young animals and humans Self healing Teat warts may need to be removed Several genotypes associated with different clinical appearances Related to bladder cancer with co-carcinogen (bracken fern) Cannot be grown in cell culture Spread by curry combs etc as is resistant virus Cause sarcoids in horses Compare with human warts Bovine respiratory syncytial virus disease :  Bovine respiratory syncytial virus disease “For many years, the feedlot industry identified a respiratory problem in cattle that was diagnosed as an allergic reaction to changes in feed. Because of the microscopic lesions found in the lungs, a virus was suspected, but when tissue samples were submitted to the laboratory, no virus could be found. It was later determined that the virus would not survive the transport techniques. Only after taking the lab to the field was the virus isolated. When grown in the lab, the virus caused specific changes in the culture cells; the same changes found in the microscopic lesions of the lungs. The lesion, called a syncytium, became incorporated into the common name of the virus” BRSV infections appear to be common in the United States. Nationwide studies have shown that BRSV is present in 38% to 76% of beef and dairy herds. Vesicular Stomatitis:  Vesicular Stomatitis An important disease per se, but particularly because it may be confused with Foot-and-Mouth Disease Endemic in some very localised areas of the USA, but major impact occurs when epidemics spread quickly in summer in south western and central states Affects cattle, horses and pigs Epidemiology is enigmatic, behaves like an arthropod borne disease, but no viremia. FMD in Domestic Species:  FMD in Domestic Species Cattle Pigs Sheep Humans are rarely infected Cliff Notes: Epidemiology of FMD:  Cliff Notes: Epidemiology of FMD Pigs are amplifiers, cattle indicators, and sheep silent spreaders FMD: fast moving disease Transmission is by aerosol once fomite and animal movement is controlled Ruminants can become carriers Incubation is 2-14 days Prodromal virus excretion Virus titer 10,000,000 tissue culture infectious doses/ml in vesic. fluid. Aerosol infective dose for cattle ~ 10 tissue culture infectious units Relatively fragile virus; stable for days rather than months Wildlife can become infected Bovine Viral diarrhea (BVD/Mucosal Disease) :  Bovine Viral diarrhea (BVD/Mucosal Disease) Recognized in North America in 1945 when all age groups affected and name BVD was coined Now associated with wide range of disease presentation and pathology Inapparent, acute sporadic with death (mucosal disease), chronic, abortion and congenital deformities Spreads by contact and most secretions/excretions contain virus Vaccines widely used Acute form clinically similar to rinderpest but can also be similar to IBR and MCF. There are no corneal opacities with BVD Pathogenesis and Epidemiology:  Pathogenesis and Epidemiology Start at circle to follow virus cycle Mucosal Disease Virus Diseases of Sheep and Goats:  Virus Diseases of Sheep and Goats Orf. Contagious Ecthyma, Contagious Pustular Dermatitis, Sore Mouth, :  Orf. Contagious Ecthyma, Contagious Pustular Dermatitis, Sore Mouth, DISTRIBUTION: Occurs in sheep-raising areas throughout the world. CLINICAL FINDINGS: Most common 3-6 month old lambs, although adults may be severely affected. Lesions develop as papules, then pustules, then thick tenacious scabs, first at oral mucocutaneous junctions, usually the oral commissures, then spreading to muzzle and nostrils. Caprine Arthritis Encephalitis:  Caprine Arthritis Encephalitis Bluetongue in Sheep:  Bluetongue in Sheep CLINICAL FINDINGS: Incubation period = 2-6 days. Fever (40.5-41oC or 105-106oF) persists for 5-6 days. Nasal discharge, salivation, reddening of buccal mucosae. Swelling and edema of lips, gum, dental pad and tongue. Ulceration of lateral aspects of tongue. Foot lesions, including laminitis and coronitis, cause lameness and recumbency. Rapid loss of condition. Lower parts of face, ears and jaws become edematous. Partial or complete loss of fleece is common. Wrinkling and cracking of skin around lips and muzzle; abortions and congenital deformities may occur. Bluetongue Epidemiology:  Bluetongue Epidemiology TRANSMISSION: The midge or gnat, Culicoides variipennis, is the biological vector in North America. Different species elsewhere. In 1980’s situation in the Caribbean required clarification for trade to continue safely Viral Diseases of Dogs:  Viral Diseases of Dogs Dogs are remarkably healthy now that the major viral diseases can be prevented by vaccination. What is the dog population of the USA? Diseases Caused by Herpesviruses:  Diseases Caused by Herpesviruses Canine Herpesvirus Infection Pseudorabies, Mad Itch, Aujezsky's Disease Diagnosis of Canine Herpes Infection in the Puppy:  Diagnosis of Canine Herpes Infection in the Puppy Lesions found at necropsy: 1. Disseminated focal necrosis and hemorrhage of multiple organs: lungs, kidneys, adrenal glands, liver, and GI 2. Splenomegaly (enlarged spleen) 3. Diffuse lymph node enlargement 4. CNS lesions Slide62:  Animal species Number of Disease Mammals serotypes Horses 2 Usually asymptomatic or mild upper respiratory disease; generalized disease in foals with congenital immunodeficiency Cattle 9 Usually asymptomatic, or mild upper respiratory disease Swine 4 Sheep 6 Goats 2 Dogs 2 Infectious canine hepatitis (type 1) Infectious canine tracheobronchitis (type 2) Birds 11 Chickens Inclusion body hepatitis and egg drop syndrome Turkeys Bronchitis, marble spleen disease, enteritis Ducks Duck hepatitis Quail Bronchitis Diseases Caused by Adenoviruses in the Dog Canine Warts:  Canine Warts Occur principally in the mouth Can be very florid Offensive breath May require surgery Very occasionally euthanasia is necessary Canine Parvovirus Infection:  Parvovirus is a highly contagious disease that affects dogs of all ages but puppies less than six months of age are most susceptible.  Breeds that are primarily affected include Rottweilers, Dobermans, Labradors, American Staffordshire Terriers, German Shepherds, and Alaskan Sled Dogs.  This is a highly resistant virus and can persist in the environment on inanimate objects for more than five months Canine Parvovirus Infection Depression - dull, sleepy, not interested in anything, not as active as before Anorexia - loss of appetite Vomiting - which may or may not be bloody Diarrhea - which may or may not be bloody; usually appears 1 to 2  days after infection Fever Parvovirus Vaccination and Disinfection:  Parvovirus Vaccination and Disinfection Bleach is one of the few household cleaners that can inactivate the virus.  A dilution of 1 part bleach to 30 parts water is sufficient in most cases. Canine Influenza:  Canine Influenza January 2004 Respiratory disease with several deaths in racing greyhounds at Jacksonville race track Inside the Kennels:  Inside the Kennels Slide68:  eqalvdalen96 Amino acid tree of H3 Equine Influenza isolates Courtesy Ruben Donis CDC Ed Dubovi (Cornell) Equine vaccine strain Possible origins of Virus Flu avert Equine Vaccine? Clinical signs of Distemper:  Clinical signs of Distemper Neurological Disorders incoordination and clumsiness head pressing poor balance Chorea (muscle tremors) weakness of all four limbs more reactive to pain or stimulus Seizures nystagmus - uncontrollable eye movements Other species affected by canine distemper:  Other species affected by canine distemper Lions Hyenas Coyotes Wolves African hunting dogs Ferrets Raccoons Foxes Jackals Clinical Rabies and Diagnosis:  Clinical Rabies and Diagnosis Negri bodies in brain Mann’s methylene blue eosin stain Viral Antigen Detected by immunofluorescent antibody staining of brain smear J Bowen Davies and P Lowings In Practice, April 2000 170-175 Clinical Photos Courtesy of Michel Aubert EM of Negri body with budding virus particles Pathogenesis: infection and incubation period:  Pathogenesis: infection and incubation period infection other (corneal transplants) bites mucosal exposure replication at site No antibody induced (antibody can prevent further spread - post exposure vaccination) Incubation period generally 14-90 days Viral Diseases of Cats:  Viral Diseases of Cats Differentiation of Feline Upper Respiratory Conjunctival Disease Complex:  Differentiation of Feline Upper Respiratory Conjunctival Disease Complex Herpesvirus Calicivirus Chlamydia conjunctivitis - to + - to +/- ++ rhinitis ++ - to +/- - to +/- pharyngitis +/- to ++ - to +/- glossal or palatine ulcers +/- + to ++ pneumonia - to +/- - to ++ Summary: Chlamydia and mycoplasma: conjunctivitis Herpesvirus: rhinitis, pharyngitis, oral ulcers Calicivirus: oral ulcers only or pneumonia Feline Panleukopenia (Feline Infectious Enteritis, Feline Distemper, Feline Ataxia) :  Feline Panleukopenia (Feline Infectious Enteritis, Feline Distemper, Feline Ataxia) Affects all members of the family Felidae and the raccoon, coatimundi, and mink Mortality may be high Clinical presentation varies FeLV: Feline leukemia virus:  FeLV: Feline leukemia virus Gammaretrovirus Discovered in 1964 in cats with contagious lymphoid malignancies Occurs worldwide and relatively common Virus excreted in saliva and spread horizontally by close contact (grooming etc) Thanks to Julie Levy for assistance with FIV and FeLV FeLV transmission:  FeLV transmission ! Queen to kitten before or after birth (vertical) Cat to cat via close or prolonged contact (horizontal) Saliva most efficient, also litter boxes, food bowls, grooming, fighting 1/3 of cats in household become infected Iatrogenic: needles, instruments, transfusions FIV: Feline immunodeficiency virus:  FIV: Feline immunodeficiency virus Lentivirus Evolved from exotic cats Spread to cats more than 1,000 years ago Discovered in 1986 in cats with “AIDS” Testing available in 1987 (Idexx) Clinical Syndromes Associated with FIV Immunosuppression:  Clinical Syndromes Associated with FIV Immunosuppression Neoplasia associated with FIV infection Stomatitis:  Stomatitis Most common clinical disease in FIV Also occurs with FeLV Late-stage event Lymphocytic-plasmacytic inflammation Calicivirus commonly isolated Etiology? Treatment? Feline Infectious Peritonitis:  Feline Infectious Peritonitis CLINICAL SYNDROME Induced by infection with FIPV Immune response to virus causes disease immune complexes,complement activation vasculitis TNF, IL1, IL6 serum exudation - “wet” form granulomas - “dry” form Current theory for FIP pathogenesis :  Current theory for FIP pathogenesis Feline enteric coronavirus Mild diarrhoea or respiratory illness persistent infection = FIP virus immune system low level of replication in epithelial and lymphoid cells Virus Diseases of Horses:  Virus Diseases of Horses Equine rhinopneumonitis (equine herpes virus 4):  Equine rhinopneumonitis (equine herpes virus 4) INCIDENCE AND OCCURRENCE: A common infection of horses, world wide. ETIOLOGY: At one time EHV 1 and 4 were considered the same virus causing rhinopneumonitis and occasionally abortion or neurological disease. Now it is realized by DNA analysis that EHV1 is the cause of abortion and neurological disease and EHV4 is associated with rhinopneumonitis Equine rhinopneumonitis (equine herpes virus 1):  Equine rhinopneumonitis (equine herpes virus 1) PATHOGENESIS: Following droplet infection, virus replicates in upper respiratory tract. There is leukocyte-associated viremic spread to other tissues, including the uterus with subsequent invasion of the fetus. The fetus is “fresh” when expelled. There is a generalised infection of the fetus. Virus can be isolated from the liver. Equine rhinopneumonitis (equine herpes virus 1):  Equine rhinopneumonitis (equine herpes virus 1) Neurological disease arises from ascending infection (the detail is not understood well) of nerve tissues seeded by the viremia. Most horses exhibit progressive ataxia and die or are euthanized. Equine Coital Exanthema:  Equine Coital Exanthema INCIDENCE AND OCCURRENCE: Worldwide in distribution. Often subclinical. Persistence and recurrence in mares and stallions have been observed. ETIOLOGY: Equine herpesvirus type 3, a single antigenic type. CLINICAL FINDINGS: Vesicles on the skin of the vulva or penis, progress to erosions, scabs, heal in about 2 weeks. Secondary bacterial infection common. May leave depigmented areas. TRANSMISSION: Venereal, possibly also other forms of contact. Equine Infectious Anemia:  Equine Infectious Anemia CLINICAL FINDINGS: In primary, acute cases, there is often marked weakness and depression, intermittent fever, edema of dependent parts, icterus and petechial hemorrhages on the conjunctiva and the ventral suface of the tongue. Increased heart rate and heart sounds, tachycardia and cardiac arrhythmia. Anemia in the initial episode is not marked but it becomes more noticeable in recurrent attacks. Relapses occur at varying intervals and death commonly occurs during a recurrent attack. The case fatality rate is around 50%. Animals that survive are liable to develop relapses at any time and also may serve as a source of infection for others. Vesicular Stomatitis:  Vesicular Stomatitis An important disease per se, but particularly because it may be confused with Foot-and-Mouth Disease Endemic in some very localised areas of the USA, but major impact occurs when epidemics spread quickly in summer in south western and central states Affects cattle, horses and pigs Epidemiology is enigmatic, behaves like an arthropod borne disease, but no viremia. Equine Influenza:  Equine Influenza Segmented, single stranded RNA enveloped viruses in the Orthomyxoviridae family ortho “standard or correct” and myxo, “mucous” HA and NA Proteins A/Prague/1/56, (H7N7); equine type 1 A/Miami/2/63 (H3N8); equine type 2 Causes upper respiratory disease in horses and ponies Drift and Shift of HA protein in Equine Influenza:  Drift and Shift of HA protein in Equine Influenza Virus Diseases of Horses Caused by Viruses in the Arteriviridae :  Virus Diseases of Horses Caused by Viruses in the Arteriviridae SPECIES AFFECTED: Horses ETIOLOGY: Caused by an RNA virus, family Arteriviridae. CLINICAL FINDINGS: Fever, respiratory signs, nasal discharge and lacrimation. Edematous swellings of dependent parts. A high percentage of pregnant mares abort during the course of the clinical disease, not as a sequel, as is the case with equine viral rhinopneumonitis. TRANSMISSION: Virus is shed in pharyngeal secretions, urine and semen. Spread by droplet infection, contact during breedings. Persistent infection occurs in stallions. Equine Viral Arteritis Slide93:  Life cycle of eastern equine encephalitis Slide94:  West Nile Virus Transmission Cycle VIRUS VIRUS Direct ? Virus VIRUS Dead - end Hosts ? Avian reservoirs Mosquito vectors Culex species West Nile Virus Infection of Horses Florida 2001:  West Nile Virus Infection of Horses Florida 2001 West Nile 5 & 6 West Nile 3 West Nile 2 Crows as a WNV Surveillance Species :  Crows as a WNV Surveillance Species Ideal Because Widely distributed throughout the United States Found in multiple habitats – urban, suburban, rural, wilderness Relatively local species, especially during nesting and fledging time of year Conspicuous bird even when sick or dead Highly susceptible to infection with WNV and thus good indicator of virus presence Virus titers in tissues high enough to allow delayed testing; however, fresh carcasses encouraged Vaccines for West Nile Equine Encephalitis:  Vaccines for West Nile Equine Encephalitis “West Nile Vaccine failures” In 2001, 132 horses (107 in Fl) developed disease after vaccination of which 19 were after 2 doses Recombitek based on Canary Pox Vector System Virus Diseases of Swine:  Virus Diseases of Swine DISEASE: Swinepox SPECIES AFFECTED: Swine INCIDENCE AND OCCURENCE: Worldwide ETIOLOGY: 1) Distinct poxvirus 2) Vaccinia virus (historical) CLINICAL FINDINGS: Red papules appear in 4-5 days and develop into raised, hard elevations which may be 1-3 cm in diameter. Hard crusts develop and drop off over a period of 12-14 days. Benign disease with slight fever and mild reaction. If the swine louse is involved in transmission of the virus, lesions develop on the lower parts of body, belly, axillae, and insides of thighs. TRANSMISSION: Direct pig to pig transfer is not common; the transmitting agent is Hematopinus suis, the swine louse. DIAGNOSIS: Virus isolation - EM. CONTROL: Elimination of lice. Pseudorabies:  Pseudorabies Pathogenesis in domestic pigs portals of entry nasal, oral epithelium early replication in upper respiratory tract may be a short, ill defined viremia spread to brain is via cranial nerves or other peripheral nerves viral excretion primarily from nose and mouth for up to 17 days post infection THEN LATENCY! Swine Flu:  Swine Flu CLINICAL SIGNS: Swine flu is a herd outbreak problem with a sudden, explosive onset. It is usually seasonal in the Midwest in fall and early winter. The pigs are so sick for 4-6 days that they may be expected to die but most recover dramatically within one week of onset. Rectal temps may be as high as 106o -108oF, pigs do not eat, breathing will be jerky (thumps), and pigs are reluctant to move. Currently 45% 45% 10% respective isolation rate in the USA Bark!! Bark!! PRRS = Porcine Respiratory and Reproductive Syndrome (Blue Ear Disease):  PRRS = Porcine Respiratory and Reproductive Syndrome (Blue Ear Disease) CLINICAL SIGNS incubation period 3-5 days first signs anorexia, fever, cyanosis consequent signs depend on age and breeding status of animals young piglets preweaning mortality 10-40% survivors may have abdominal breathing, diarrhoea grower and finisher pigs influenza-like illness may be ill up to 3 weeks mortality 1-5% PRRS:  PRRS Clinical Disease Continued breeding sows sudden deaths 1-2% late abortions 1-2% premature farrowing 1-20% farrowings with dead, live and dead and/or mummified foetuses increased farrowing interval retained placentae In older pigs mortalities associated with pneumonia often complicated by secondary bacterial infection Slide103:  The Transmissible Spongiform Encephalopathies (TSE’s) Characteristics of TSE’s:  Characteristics of TSE’s Brain degeneration with vacuolation Long (2.5 years and >) incubation period Cause is believed to be a unique infectious agent called a prion which is an infectious protein Infectivity very hard to inactivate No host immune response is detectable Invariably fatal And now for a little fun:  And now for a little fun

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