Infectious Diseases Lecture 3 PDF

Infectious diseases Lecture 3 Dr.Emad  1- Malignant Catarrhal fever (Malignant head catarrhal fever) Definition Highly fatal pan systemic infectious disease of cattle and buffaloes Characterized clinically by- − Mucosal lesions: erosive...

Infectious diseases Lecture 3 Dr.Emad  1- Malignant Catarrhal fever (Malignant head catarrhal fever) Definition Highly fatal pan systemic infectious disease of cattle and buffaloes Characterized clinically by- − Mucosal lesions: erosive stomatitis (erosion of palate) N.B − Severe rhinitis: erosion in upper resp. tract Mucosal diseases are: − Corneal opacity (from peripheral to center) BVD-FMD-IBR-MCF − encephalitis, lymphadenopathy − and diarrhea. The disease is commonly sporadic but sometimes appears in epizootic form. Etiology Alcelaphine Natural host: herpesvirus-1 wildebeest in Sub family: (AHV-1) Africa Family: Gamma Herpesviridae herpesvirus Ovine Natural host: herpesvirus-2 domestic sheep (OHV-2) worldwide Epidemiology: ❖ Distribution o AHV-1 primarily in Africa ▪ Carried by wildebeest, hartebeest ▪ Also, in zoologic and wild animal parks o OHV-2 worldwide ▪ Carried by domestic and wild sheep and goats ❖ Morbidity/Mortality Carrier species have asymptomatic infection o Wildebeest, sheep, goats Low morbidity in cattle High Mortality in Cattle (100%) but sporadic ❖ Animals susceptible Cattle of all ages are susceptible Sheep and goats are considered the natural host of the virus and are infected sub clinically. ❖ Sources of the virus AHV-1 cell associated ( ‫)مش بيطلع بسهوله‬ Rarely transmitted (sporadic cases) 1  Stress (lambing of sheep or calving of wildebeests) induces shedding cell-free virus in its secretion as: - 1. Nasal secretions via aerosol 2. Contaminate feed, water 3. Arthropods Finally infect the cattle &buffaloes ❖ Transmission − Cattle is infected from sheep or wild animals and it is considered dead end host (no cattle to cattle transmission). − Direct contact between cattle not transmit infection − Sheep to cattle − Wildebeest to cattle − Sheep to sheep Ovine Herpes Virus Transmission not understood, occurs during lambing of sheep and infects cattle Clinical signs: 1- Per acute form: Sudden death 2- Head and eye form (common cases) Progress through stages 3- Intestinal form Initial head and eye but die of severe diarrhea 2- Head and Eye Forms Head and Eye Form Early stages Head and Eye Form Later stages ▪Persistent high fever (2-3 weeks), anorexia ▪Erosions on the buccal mucosa ▪Reddened eyelids, lacrimation, conjunctivitis ▪Erosions on the tongue ▪Bilateral corneal opacity (peripheral to central) ▪Superficial lymph nodes swelling ▪Crusty muzzle, nares ▪Horn, hoof coverings slough ▪Mucopurulent thickened Nasal discharge ▪At terminal stage: Nervous signs appear ▪Salivation Incoordination, head pressing, Hyperesthesia Muscle tremors - convulsion – paralysis recumbency - death ▪There is diarrhea in some cases but it is not a constant signs and some cases had constipation ▪In some cases there is inflammation and necrosis of the skin of the udder and teats, between the hind legs 2 3- In the enteric form of the disease(intestinal) The same signs are observed but the diarrhea is more prominent signs than other signs. The urine may be red due to hemorrhagic lesions in the urinary bladder. Most cases die within 1-3 weeks. Post Mortem Lesions 1- Erosions on palate 2- Necrotic areas in the Specifi sign omasal epithelium 3- Multiple erosions and 4- Greatly enlarged lymph node hemorrhages of intestinal epithelium compared to normal 5- Necrotic areas in the larynx Diphtheritic membrane often present 3  6- Urinary bladder mucosa 7- Kidney often has raised hyperemic and edematous white foci on the cortex Diagnosis: 1- History: high mortality - sporadic cases - exposure to wild animals or sheep, goat and contact with cattle & buffaloes 2- clinical signs 3- PM Any susceptible animal with sudden death, fever, erosions of the mucosa, nasal/lacrimal discharge, bilateral corneal opacity should be tested for MCF o Particularly with a history of exposure to sheep, goats, antelope, or wildebeest during parturition Differential Diagnosis BVD mucosal disease N.B Bluetongue Rinderpest Erosion of dental pad FMD and tongue: FMD Vesicular stomatitis Hard palate erosion: Theileriosis 1. BVD Salmonellosis 2. MCV Pneumonia complex Laboratory diagnosis Sampling Blood in EDTA tube for virus isolation Fresh tissue collected and immediately after death o Spleen, lung, lymph nodes, adrenal glands Paired serum samples refrigerated 4 Laboratory Tests Histopathology, PCR Virus isolation for AHV-1 Serology Treatment Survival is rare Mortality reaches 100% Supportive therapy, antibiotics for secondary bacterial infection ❖ Recovered animals will remain virus carriers Control: 1- Isolate sheep from cattle esp. during calving and lambing 2- Avoid breeding sheep, goat, wildebeests & wild ruminants with cattle and buffaloes 3- Avoid importation of ruminants from enzootic areas 4- Zoological parks: − Introduce seronegative animals only There is No vaccine available B- Rinderpest (Cattle plaque) Definition Acute fatal highly contagious viral disease of cattle, buffalo Characterized clinically by: - o Oral lesions and diarrhea o High mortality rate (95%) and high morbidity rate Relatively fragile virus Etiology Family :Paramyxoviridae Genus :Morbillivirus Rinder pest RP Members of this family include: (antigenically related) Peste des Petits Ruminants virus PPR Measles virus Canine distemper virus 5 Epidemiology Geographic Distribution How did this virus disappear??? 1- Sensitive virus (die quickly) 2- Fragile virus that easily killed 3- No antigenic difference 4- No carrier 5- No chronic cases: (only infected animals can affect other animals, so it is an acute infectious disease) 6- Very effective vaccine: solid immunity 3 years a. The vaccine that eliminates this virus is live attenuated tissue culture RP vaccine P.M lesion Zebra marks on rectum C- Enzootic bovine leukosis (Bovine lymphosarcoma - Bovine leukemia) Definition Fatal systemic malignant neoplasia of the reticuloendothelial system of cattle and buffaloes Characterized by development of aggregation of neoplastic lymphocytes in any organ with a variety of clinical syndromes. Etiology BLV is RNA virus Family Retroviridae Subfamily Oncovirinae 6  Inside the mammalian cells, the viral RNA acts as a template to form its own DNA which it incorporates into the cows DNA. Then the virus multiplies within the cell each time the cell divides, this results in the animal being permanently infected. Epidemiology ❖ Distribution In Egypt: associated with imported animals from America 1989 in upper Egypt Disease signs appear 1996 ❖ Animals susceptible The disease affects cattle and buffaloes Infection can occur at any age, but clinical onset usually begins at three years of age and up depending on time of infection. ❖ Sources of the virus BLV found persistently in lymphocytes of clinically diseased or carrier animals. These animals shed the virus in secretion & excretion as o Blood o Milk o Colostrum o Semen o Saliva o Nasal discharge o Intermittent in urine ❖ Transmission 1- Vertical: from dam to calf through: Uterus, Milk, and colostrum 2- Horizontal: Blood transfusion, The use of contaminated surgical instruments and syringes(iatrogenic) Rectal palpation. Insects. 7 Pathogenesis: Differ according to genetic resistance &immunity status of animal: There are 4 possible pathways: 3- Persistent 4- Clinically diseased 1- Resist infection: 2- Latent carrier: lymphocytosis (malignant (benign): lymphosarcoma): Failure of animal to be Permeant infection - Increase number of Development of infected may be due without clinical signs abnormal aggregation of cells to previous immunity but produce Ab lymphocytes without in form of tumor or genetic resistance 70% of cases tumor 2-5% of cases 30% of cases - No Ab in blood Clinical signs When diagnosing a BLV infection in a herd it is important to realize that only approximately 5% of the infected cattle show clinical signs of the disease. The animals that show clinical signs were probably affected previously prior to the onset of clinical disease due to long I.P BLV is difficult to diagnose clinically because the clinical signs depend on what organ systems are being affected by the growing tumors. ❖ General signs: associated with tumor Enlargement of Emaciation, Pale mucosal superficial lymph muscular surface nodes without weakness fever as TB ❖ Specific signs: differ according to organ affected 2- Tumor in 3- Tumor in spinal 4- Tumors in 5- Tumor in lymph 1- Tumor in heart abomasum & cord orbital cavity nodes intestine oHydropericardium oPersistent oParalysis of hind 1.Occlustion of eye oMarked oHydrothorax chronic incurable limb ball enlargement of oEdema of the diarrhea (endopthalmia) several superficial brisket and the oFollowing lymph nodes intermandibular infiltration of the oRetropharyngeal: region abomasum wall snoring, dyspnea oDyspnea,laboured by neoplastic breathing cells 8 Post Mortem Lesions 1- Enlarged lymph nodes throughout the body. 2- The spleen, liver and kidney may be enlarged and pale due to infiltration of lymphocytes. 3- The wall of abomasum and intestine is thickened. 4- Tumor masses, which are firm and white of varying size, are present in any organs. Diagnosis: 1- Clinical signs. 2- Differential diagnosis with other diseases like o Tuberculosis (Enlarged lymph nodes without fever) by tuberculin test.(do rectal smear) o John's disease (chronic diarrhea) by characteristic lesions in intestine. o Traumatic pericarditis if the lesions in the heart. N.B Laboratory diagnosis Neutrophilia: TRP Sampling Lymphocytosis: BL Section from tumor in formalin Impression smear from tumor Whole blood in anticoagulant (buffy coat) Serum Histopathology PCR Virus isolation Hematology: blood film - CBC AGID (Agar Gel Immunodiffusion) control ‫ من الحجات الي بستخدمها في‬or ELISA Hematological Findings Numerous lymphocytes in a blood film of a cow suffering from bovine leukosis. AGID and ELISA − Used to measure antibody levels − Because BLV acts as a persistent infection, the animal will produce antibodies against the virus which we can us to diagnose, control, and eradicate infected animals. − The animal produces circulating antibodies between 3 weeks and 3 months post infection. PCR − It is very accurate and reliable. − It can be performed on tissues submitted for histology, but is most commonly performed on peripheral blood lymphocytes and lymphosarcoma in tissue sections 9 Treatment − No specific treatment is available Control − Test & slaughter: serologically by AGID or ELISA o Positive cattle and calves > 6m of age: slaughter immediately o Positive calves < 6m separated and retested at 9m of age, if +ve: culling − BLV can be eliminated from a herd if all the animals are tested serologically at 2–3-month intervals. − Vaccinate negative by Inactivated bovine leukosis viral vaccine. Sporadic bovine leukosis Affect animals < 3 years of age BLV not cultured from infected animal No Ab detected Defect in multiplication of cells There are 4 forms of sporadic bovine leukosis: 1- Juvenile form 2- Thymus form 3- Cut form 4- Bone form D- Akabane Curly calf disease Epizootic abortion Congenital arthrogryposis Hydranencephaly syndrome Definition − Arthropod borne viral disease of cattle, sheep & goats (ruminants). − Characterized clinically by abortion or still birth esp. in sheep & congenital anomalies in newly born calves Etiology Akabane virus RNA virus Family Bunyaviridae 10 Epidemiology: ❖ Distribution − Asia (Japan) − Africa − Middle east ❖ Transmission − Blood sucking insects − Intrauterine (dam - fetus) ❖ Susceptibility: - − Cattle − Sheep − Goat ❖ Source of Infection − Blood Pathogenesis: Virus in dam (viremia) for 3-4 days Fetus Cessation of differentiation in its growing neural tube At 76-104 day of pregnancy: Hydranencephaly At 105-174 day of pregnancy: Arthrogryposis Clinical signs − Virus replication within the tissues of adult cattle, sheep & goats not cause any clinical signs − Non pregnant cows or ewes: not show any clinical signs − Pregnant cattle: o Infection at early pregnancy: abortion of normal or deformed fetus o Infection at late pregnancy: dystocia esp. in case of abortion and arthrogryposis 11 Signs appear only on fetus (intrauterine infection)!!!!!!! 1- Hydranencephaly: (at 76 -104 d of pregnancy) Partial or complete failure of development of cerebral cortex Absence of brain tissues and replaced by fluid, Skull cavity filled with fluid According to part of the brain absent, animal show variety of clinical signs Signs: Ataxia - incoordination - paresis, paralysis – blindness PM: muscular atrophy - limb deformity, hydranencephaly (brain cavity filled with fluid) 2- Arthrogryposis: (at 105 - 174 d of pregnancy) Neurotropic failure of development of muscle No muscle formation or short Fixation of joints (flexion position)There is congenital articular rigidity Sometimes also, torticollis Signs, PM: hook like limbs in one or limbs - short limb or complete absent Unable to stand, rise or walk Diagnosis: Clinical signs. Differential diagnosis With diseases causing congenital anomalies o BVD o Blue Tounge o BD o Weeslsborn disease o Toxoplasmosis 12  With diseases causing abortion o Campylobacter o Listeria o Brucella Laboratory diagnosis Sampling: − Fetus: placenta - fetal membrane - fetal fluid-CSF- peritoneal fluid - pericardial fluid − Dam: serum Tests 1- Detection of viral Ag in fetal tissue or isolation by IC inoculation in suckling mice & identify by FAT 2- Detection of Ab by AGID Control − Insect control − Inactivated vaccine: not available in Egypt but available in Japan, Australia Prion diseases ❖ Group of slowly progressive, degenerative neurologic diseases in animals and man ❖ classified as Transmissible Spongiform Encephalopathies (TSE). 1- Cattle: spongiform encephalopathies (BSE) 2- Sheep: Scrapie 3- Human spongiform encephalopathies (Kuru, Creutzfeldt-Jakob Disease (CJD) 4- Transmissible Mink Encephalopathy (TME). 5- Chronic Wasting Disease (CWD) of elk, deer These diseases share same character: 1- Fatal termination 2- Experimentally transmissible 3- Cause vacuolation of neurons in brain 4- Have the same causative agent: prion 5- A prolonged incubation period of months or years 6- The transmissible agent elicits no detectable specific immune response in the host. Etiology Not caused by virus or bacteria or fungi But its cause is infectious protein (prion) o Smaller than smallest known virus o Not yet completely characterized o Prion= Proteinaceous Infectious particle 13  o No envelope, no DNA o Resist boiling, rapid freezing and thawing, heat, U.V radiation, ether, and formalin 20% o But inactivated by NaoH 4% (caustic soda), chlorine 2% and steam sterilization (autoclaving) o Not immunogenic due to its low molecular weight and lack of foreign Ag o Occur normally in CNS, converted to abnormal modified form (PrPSC) that accumulate in neurons lead to its destruction Normal protein PrPC (C for cellular) Glycoprotein normally found at cell surface inserted in plasma membrane Abnormal Protein Prpse (Sc for scrapie) Same amino acid sequence and primary structure as normal protein Destruction of disulfide bonds Non-soluble protein Insoluble in all solvent except strongest solvents Highly resistant to digestion by proteases oSurvives in tissues post-mortem Pathogenesis: normal protein transfer to Prpse then go to brain that cause vacuolation in brain tissue E- Bovine Spongiform Encephalopathy ESE Mad Cow Disease History 1986 o First confirmed case in United Kingdom 1988 o UK bans meat and bone meal from ruminants in cattle feed Geographic Distribution 95% of all BSE cases in U.K. o Outside U.K. due to importation or contaminated feed No cases reported from o Australia, New Zealand, Central America, South America 2003 o Canada and U.S. reported single cow 2005 o Additional Canadian cases o U.S. reported single case - June 14 Transmission − Not!!!!!! by contact − Spreads orally o Ingesting infected brain, spinal cord, skull, vertebrae and ileum − Cattle o Eating contaminated meat and bone meal − People (vCJD) o Eating contaminated ground meat ❖ Human transmission ✓ Possible modes of transmission − Transmission from surgical instruments used on tonsils, appendix, or brain tissue − Growth hormone injections − Vaccines ✓ Unlikely modes − Blood transmission Incubation period All TSEs have incubation periods of months or years. The incubation period of BSE is more than a year and often several years. The peak incidence of disease occurs in 6- to 8-year-old cattle. Species affected BSE is seen in cattle and can be experimentally transmitted to cats, mink, mice, pigs, sheep, goats, monkeys Clinical signs: The clinical signs are neurologic and once the symptoms appear, the disease is progressive and fatal. 1- Changes in posture and movement 2- behavioral changes such as 3- Terminal state o Hind limb ataxia, pelvic o Apprehension, oDecreased rumination swaying, o Nervousness oLoss of body weight o Tremors, falling, o Fear and condition despite o Apprehension, fear, easily o Easily startled startled, depressed good appetite, o Depressed oRecumbancy o Excitable o Hyperreflexia oParalysis and Death There is no treatment for BSE Affected herds o 2% morbidity o 100% mortality 15  o Average age when symptoms appear 3 to 6 years of age o Affected cattle die o Death-2 to 6 months after symptoms begin Post Mortem Lesions − No way to test live cattle − Spongy appearance of brain tissue − Abnormal prion protein Diagnosis: − Slowly progressive, fatal neurologic disease Differential Diagnosis Disease confused with disease causing nervous signs:- 1- Infectious causes o Rabies, IBR, Pseudorabies, MCF, Listeriosis 2- non infectious causes o Nervous ketosis o Hypomagnesemia o Brain tumor o Lead poisoning o Spinal cord trauma Sample Brain: The red box indicates the region of the obex, which is the portion of the brain that must be obtained for the diagnosis of BSE and other spongiform encephalopathies such as scrapie and chronic wasting disease 1- Histopathology of brain tissue − Spongiform changes in gray matter 2- Detection of abnormal prion protein 16  All are based on antibodies to detect prion protein in tissue Immunohistochemistry is considered the gold standard o Expensive o Labor intensive Various rapid diagnostic tests have been developed o Western blotting o ELISA Control 1- Prevent importation of live ruminants and ruminant products (especially meat, bone meal, and offal) from countries where BSE may exist. 2- The prohibition of feeding ruminant proteins to ruminants. Scrapie in sheep Age Most cases of scrapie occur in sheep 2 -5 years of age. Although rarely seen in sheep < 1 year of age or > 5 years old. Age alone cannot be used to rule out the presence of scrapie. Transmission Scrapie is spread through fluid and tissue from the placentas of infected females. o It can be transmitted from an infected female to her offspring at birth, o or to other animals exposed to the same birth environment. Development of clinical signs 2- Changes in 3- Changes in posture 4- Later 1- Irritation behaviour and movement clinical signs Repeated rubbing of flanks and Becoming excitable Trembling (mainly of Weight loss hindquarters against objects such as the head) fences, posts or hay racks Drooping ears Death Grinding teeth when rubbing Increased Severe incoordination themselves or when rubbed nervousness or fear Weak hind legs firmly on the back response Unable to stand Continued scratching of the shoulder Lagging behind or ear with a hind foot Aggression Unusual or agitated nibbling of the fest, legs or other parts of the body Depression or vacant Excessive wool loss or damage to the stare skin − Most sheep show a gradual development of clinical signs over a period of several weeks or even months, − Some sheep and goats affected with scrapie may just be found dead without showing any clinical signs beforehand. 17 Scratch test − Most scrapie cases respond to scratching of the back with lip licking and nibbling o positive nibble reflex − Test sites should be scratched repeatedly (at least 3 times) and with a pause between each stimulus − Ideally, handlers should stand next to the sheep and use their legs to "press" the animal against a wall Diagnosis 1- Scrapie is diagnosed after death by microscopic examination of the brain tissue, tonsils, lymph nodes, or spleen that have been treated with a special stain. Control Sheep should not be permitted to eat placenta 2 Regular cleaning of buildings used for lambing Culling the relatives of scrapie cases from the lock/herd. To be successful this requires clear identification of animals and adequate record Sheep are purchased from verified sources 18