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Flashcards in Final Exam - Coronaviridae Deck (49):
1

Transmissible gastroenteritis virus of swine (TGEV)

Group 1a. Highly infectious viral disease of pigs characterized with vomiting, dehydration, diarrhea and high mortality in piglets. Older pigs are also susceptible, but often exhibit milder clinical signs. Classified as OIE list B disease.

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Transmissible gastroenteritis virus of swine - Etiology

The causative agent, TGE virus (TGEV) belongs to the genus coronavirus of the family Coronaviridae.

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Epidemic TGEV form

When the virus is first introduced into a susceptible herd, and is observed most often in winter. Rapid spread, high morbidity and mortality in piglets.

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Endemic TGEV form

When virus persists in partially immune herd, or due to concurrent porcine respiratory coronavirus (PRCV) infection (a deletion mutant of TGE virus). Less severe form of disease and much lower mortality or morbidity.

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Transmission of TGEV

Exact mode is not clear. But fecal oral transmission appears to be a major route of transmission. Can also be spread by aerosol.

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Pathogenesis of TGEV

Normal intestinal villi is infected with TGEV. Villus atrophy results in malabsorption which leads to diarrhea

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Clinical signs TGEV

Profuse diarrhea in piglets, vomiting, severe depression and dehydration, watery, yellow-green stool with offensive odor. Feces contains clots of undigested milk. Distended intestine showing translucent intestinal wall and fluid ingesta. Dilated stomach containing undigested milk. Bloated gut. Presence of gases of atrophy on intestinal villi.

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Diagnosis of TGEV

Clinical findings, necropsy and histopathology. Detection of viral antigen by fluorescent antibody assay (FA), immunohistochemistry (IHC). Microscopic detection of virus using electron microscopy (EM), isolation and identification of virus by tissue culture. Detection of nucleic acid by reverse transcriptase polymerase chain reaction (RT-PCR). Serological tests to measure antibody titers to the virus.

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Control of TGEV

Isolation of sow due to farrow. Discontinuation of selling and purchasing breeding stock. Partial culling. Planned exposure to virulence virus. Biosecurity measures. All-in all-out management system. Complete depopulation and establishment of new herd. Vaccination of pregnant sows and neontal pigs.

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Porcine Epidemic Diarrhea (PED)

Caused by Corona virus (group 1b). Although clinical signs are similar, PED virus is unrelated to TGE virus (group 1a).

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PED - Transmission

Spread via the fecal oral route. Cause acute outbreaks of severe diarrhea, vomiting, high morbidity. Endemic and problematic pig disease.

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Porcine Hemagglutinating Encephalomyelitis (Vomiting and Wasting Disease in Pigs)

Coronavirus with Hemagglutinating properties. Aerosol route/contact with nasal secretion from infected or carrier swine. Replication in nasal mucosa. Replication in lungs, tonsils, small intestine. Spread via peripheral nervous system to CNS. Replication in brain stem, cerebrum, cerebellum.

Can either become:
1. Wasting (usually piglets

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Porcine Hemagglutinating Encephalomyelitis (Vomiting and Wasting Disease in Pigs) - Clinical Findings - Encephalomyelitic form

Muscle tremors, hyperesthesia, stilted gait, blindness, opisthotonos, nystagmus, paddling convulsions, death. Morbidity and mortality high in neonatal pigs. Nonsuppurative encephalomyelitis, hematoma, meningeal and cortical hyperemia. Cortical neuronal edema.

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Porcine Hemagglutinating Encephalomyelitis (Vomiting and Wasting Disease in Pigs) - Clinical Findings - Vomiting and Wasting Disease (VWD) form

Repeated retching and vomiting, yellow green vomitus, anorexia, constipation rapid emaciation. Neonatal pigs become dehydrated, cyanotic and comatose and die. Anterior abdomen distended from impaired emptying and accumulation of gas.

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Bovine Coronavirus Infection in Calves.

Diarrhea in calves (1 day to 3 months of age, mostly 1-2 weeks). More common during winter months. Fecal oral transmission.

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Bovine Coronavirus Infection in Calves - Pathogenesis

Sick calf or carrier cow transmit to healthy calf. Virus primarily replicates in small intestine and also in large intestine. Atrophy villi, destruction of crypt epithelium. Malabsorption, increased secretary function. Profuse diarrhea.

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Bovine Coronavirus Infection in Calves - Clinical Findings

Profuse liquid diarrhea, feces may contain flecks of blood, explosive outbreaks in a herd (sudden and rapid spread). Complicated with bacterial infections, such as enterotoxigenic E. coli. Rehydration therapy such as administration of fluids buy IV route.

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Bovine Coronavirus Infection in Calves - Prevention

Commercial bovine rotavirus-coronavirus E. coli F5 (K99) vaccines. Vaccination of healthy pregnant cows and heifers. Revaccination before each subsequent calving. Increased levels of protective antibodies against coronavirus, rotavirus and E. coli in colostrum and milk of vaccinated cows. Antibodies. Passive immunity to calves against these enteric pathogens after drinking colostrum and milk.

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Winter Dysentry in Cows

Disease occurs in mature cattle, most common in recently calved lactating cows. Young cattle may be infected, but normally exhibit mild clinical signs.

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Winter Dysentry in Cows - Etiology

A coronavirus exhibiting a close serological relationship to coronaviruses causing calf diarrhea. However, antigenic differences between different isolates have also been reported.

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Winter Dysentry in Cows - Transmission

Mainly transmitted by fecal oral route

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Winter Dysentry in Cows - Pathogenesis

Similar to coronaviruses, causing diarrhea in calves. In rare fatalities, severe hemorrhage and hyperemia of colonic and cecal mucosa.

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Winter Dysentry in Cows - Clinical Signs

Sudden, explosive outbreak of diarrhea, short, dark green to black colored feces, presence of blood flecks, dehydration, decline in milk production, some coughing.

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Feline Infectious Peritonitis (FIP)

A highly fatal immune mediated disease of cats and wild felids, such as Cheetahs. Triggered by systemic infection of cats with feline coronavirus (FCoV). An enigmatic disease: its biology is poorly understood and prevention is difficult.

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Feline Infectious Peritonitis (FIP) - Transmission

Infected or transiently infected cat OR chronic carrier cat shed FCoV in feces. Fecal oral transmission to uninfected cat. FCoV can be also transmitted by other routes: inhalation or transplacental transmission.

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FIP - dispersion

5-10% - resistant
70% - Transient infection (mild diarrhea)
5-10% - Persistent Carrier
1-3% - FIP

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FIP Hypothesis-1

FCoV (FECV, feline enteric corona virus). FCoV (FECV) avirulent/less virulent. Mutations. Avirulent/less virulent variants. FIP FCoV (FIPV) virulent).

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FIP Hypothesis-2

Avirulent and virulent forms are simultaneously circulating in cat populations

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FIP Pathogenesis

Feline enteric coronavirus is less virulent or avirulent to cats and in most cases causes mild diarrhea in cats. In the cat, the feline enteric coronavirus undergoes mutations. Most of these mutations give rise to more numbers of avirulent or less virulent feline enteric coronaviruses. Feline enteric coronaviruses have no affinity for macrophages. Do not replicate efficiently in macrophages.

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FIP Pathogenesis - Sometimes

Some mutation give rise to a highly virulent form of the virus, known as FIPV. It is not clear what specific mutations cause the less virulent/avirulent feline enteric coronaviruses to transform into the virulent FIPV. FIPV has increased affinity for macrophages. Can replicate efficiently in macrophages. Lose tropism (affinity) for enterocytes of intestine. FIP enters the macrophages through the CD13 receptor. Infected activated macrophages traffic/spread throughout the body, resulting in a disseminated infection.

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FIP - Strong Cell Mediated Immunity

Prevents FIP

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FIP - Weak Cell Mediated Immunity and Strong Humoral Response

Effusive (wet) form FIP. Peritonitis, pleuritis, vasculitis, intravascular coagulation, ascites, glomerulonephritis.

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FIP - Intermediate response

Non-effusive/dry form FIP. Small granulomas, ocular lesions, CNS involvement.

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FIP - Effusive Form

Distended Abdomen, diffuse fibrinous peritonitis, ascites, pyogranulomatous foci on the serosal surface of the intestines. Pyogranulomas in liver.

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FIP - Non-effusive form or dry form

Granulomatous inflammation and enlarged mesenteric lymph node. Pyogranulomatous lesions (kidney). Granulomatous meningoencephalitis. Granulomatous uveitis. Keratic precipitates on the inner cornea.

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FIP - Diagnosis

Effusion Analysis: Rivalta Test, in a test tube, add one drop 98% acetic acid + 5 ml distilled water and mix thoroughly. Add one drop of effusion to tube. If drop disappears and solution = negative for FIP. If drop retains its shape, drops down or attached to surface of tube = positive for FIP.

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Remember

The ELISA, IFA, and virus-neutralization tests detect the presence of coronavirus antibodies in a cat, but these test cannot differentiate between the various strains of feline coronavirus.

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FIP - Prevention

An intranasal vaccine was developed to prevent FIP in cats, but it has controversial. It is not recommended.

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Avian Infectious Bronchitis (IBV)

There is a respiratory form and nephrotopic form. Pathology is commonly observed in respiratory tract. Some strains are highly nephropathogenic.

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Transmission of IBV

Aerosol/inhalation. Direct Contact. Contact with contaminated poultry, litter, food, water, equipment, or other fomites.

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Clinical signs - IBV Respiratory

Severity enhanced by immunosuppression. Depression, ruffled feathers, gasping respiratory distress, dyspnea, tracheal rales. Congestion, hemorrhages in trachea. Inflammation of trachea and bronchi, white caseous exudate in syrinx and primary bronchi.

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Clinical signs - IBV Nephritis

Nephritis, kidney swollen, urolithiasis, ureter distended with urates. White urates in swollen kidney, visceral gout, urates on liver, heart.

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Infectious bronchitis virus reproductive disorders

Soft-shelled, Misshapen, discoloured eggs, albumen thin and watery, separation between thick and thin albumen absent, involuted flaccid ovarian follicles, stunting, dwarfing or emrbyo.

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Infectious Bronchitis Virus - Control

Bio-security - proper hygiene, use of disinfectants, restricted entry, verification of day-old chicks received on farm with vaccination of history of parents.

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IBV - Live Vaccines

Live vaccines are used in meat type (broiler) chickens and for the initial vaccination and priming of breeders and layers pullets.

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IBV - Inactivated vaccines

Intended for use in layers and breeders. The vaccines are administered by subcutaneous inoculation at thirteen to eighteen weeks of age to pullets which have been previously primed with live attenuated vaccines.

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Toroviruses

Torovirus named after unique shape of nucleocapsid, doughnut shaped. Cause gastroenteritis in mammals, primarily cattle. Transmitted by fecal oral route.

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Bovine Toroviruses

Also known as Breda virus. Two serotypes: bovine torovirus serotypes 1 and 2. Calves up to 4 months of age are susceptible, but occur frequently in 2-5 days old calves. Transmission of virus by fecal-oral route, also by nasal route. Causes profuse diarrhea in young calves.

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Bovine Toroviruses

BoTV rapidly infects epithelial cells from the lower half of the villi, extending into the crypts throughout the mid-jejunum, ileum. BoTV infects the surface and crypt epithelium of colon and cecum. Cause villous atrophy, crypt hyperplasia and in some cases fused villi.