1A Drew CSF OIE BJ 2018.Pptx
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29/07/18 Economic impact of CSF • Netherlands 1997 – 11 million pigs killed – 2.3 billion US dollars (Meuwissen et al., 1999) Classical swine fever • Significant losses in endemic areas – Around 26% mortalities Trevor Drew – Abortions, returns to service Lead Scientist, Animal & Zoonotic Viral Diseases OIE Reference Laboratory for CSF – Additional costs of control APHA Weybridge – Also losses to abattoirs, processors and retailers United Kingdom • In extensive pig-holding systems in developing countries the animal and economic losses may be less obvious – provide an important source of protein in communities that are very poor – Also “piggy bank” – up to 42% of family income OIE Regional Workshop, Beijing, July/Aug 2018 2 Pestiviruses - four genotypes: Survival of CSF virus • Classical swine fever virus • Can be regarded as moderately fragile • May survive long periods under favourable conditions •Bovine viral diarrhoea virus – Cool, moist, protein rich type I (BVDV-I), BVDV-II), BVDV- III (atypical) • Frozen meat - 4 years • Refrigerated meat - 3 months •Border disease virus (BDV) • dry-cured meat - 6 months – Environment • Sheltered surfaces – 7-14 days • Manure - 15 days • Water - 6-24 days Single strand positive sense RNA, • Disinfection – an enveloped virus 40-60nm, 12.5kB, one ORF/polyprotein – Sensitive to organic solvents Family: Flaviviridae – Also all commonly used disinfectants 3 4 Natural hosts of classical swine fever Transmission of CSF Genus Sus ASSUMED: • Sus scrofa (wild boar) Sus barbatus (bearded pig) • Very contagious • Sus scrofa domesticus(domestic pig) Sus bucculentus (Vietnam warty pig) – Pig-to-pig contact • Chinese breeds? Sus cebifrons (Visayan warty pig) Sus celebensis (Celebes wild boar) • Oral and aerosol spread – Some say variable… Sus heureni (Flores warty pig) • Semen Sus philippensis (Philippine warty pig) • transplacental Other Tribes of Suinae? Sus timoriensis (Timor wild boar) – Feeding of food scraps/swill • Peccary (Tayassu spp), Sus verrucosus (Javan pig) – Infected pig pens, lorries, equipment, clothing • Warthog (Phacochoerus spp) – Transmission by needles/instruments • Bushpig (Potamochoerus spp) • pygmy hog (Sus salvanius) – Vaccine contamination • All Yes • Babyrousa - unknown 5 6 1 29/07/18 Epidemiology of CSF Molecular epidemiology – Genotypes of CSF virus • Virus endemic in wild pigs • Also in village pigs in many countries • Compares nucleotide sequences of different • Introduction into free countries by: regions of the viral genome – pigs – pig products, incl semen • Can distinguish groups and sub-groups – Semen • Can assess the degree of inter-relatedness of – Contamination of other biologicals isolates – Inadequate containment within laboratories • Spread by: • Can indicate the likely source of a virus in an – All of the above outbreak – Fomite transmission, incl. visitors clothing • Utilize complex computer algorithms EPIDEMIOLOGY and PATHOGENESIS ARE LINKED 7 8 CSF - distribution • Worldwide – Endemic in many countries, controlled by vaccination – Particularly prevalent in SE Asia • Husbandry systems are a challenge to control • Also reported in wild pigs in many countries in Asia □ South & Central America □ Much effort at eradication – some success □ Village pigs a problem □ Still in some Caribbean islands □ Developed countries – mainly free CSFV □ But still occasionally appears in wild boar in Europe DIVERSITY 9 10 Pathogenesis of classical swine fever CSF virulence • Many factors can affect the clinical signs • Field strains vary widely in virulence and pathology • High virulence – Virulence of the virus – acute disease, high mortality – Health of the pigs – Outcome independent of host factors • concurrent / 2° infections • Moderate/low virulence • Other stress factors eg environment, crowding – subacute/chronic, low mortality – Age of the pigs • but may be high mortality in fetuses and newborns – immune competence – Host factors can affect outcome of infection – nutritional condition 11 12 2 29/07/18 CSF infections - three forms Epidemiology of infection - high virulence strains 1. Acute – postnatal, high virulence • Highly contagious 2. Chronic – large amounts of virus excretion – postnatal, moderate virulence – oronasal & lacrimal secretions, urine, faeces 3. Late-onset - congenital infection • Fast spread – prenatal, low virulence – pig-to-pig – mechanical vectors □ personnel, pets, birds, arthropods • Pig density a significant factor 13 14 CSF - early clinical signs Epidemiology of infection • First appearance - only a few affected pigs - low virulence strains – Drowsy, less active – arched backs / chilled – drooping head / straight tail • Infection often unnoticed – reduced appetite – in utero transmission • marked anorexia • short period of virus excretion during acute – fever - to 42°C or more infection – lower levels of virus • Large quantity of virus at farrowing – drop in leukocyte count - 3 to 9 x 103 per mm3 • congenitally infected piglets a continuous – eyes - marked discharge/conjunctivitis source of spread – constipation, turning to grey diarrhoea – vomiting - bile 15 16 CSF - the outbreak • More pigs show clinical signs CSF: • Early-affected pigs:- very – gaunt, hollow-flanked – weaving, staggering gait - weak sick hindquarters – posterior paresis sow – purplish discoloration over abdomen, ears, snout, medial IP9 sides of legs – High virulence - death 10 to 20 dpi – medium virulence - death within (UK 30 days infectious premise 2000) 17 18 3 29/07/18 CSF : erythema of sow IP9 19 20 Chronic CSF (Mengeling & Packer, 1969) – clinical improvement after acute phase • persistent leukopenia – second phase of illness • anorexia and depression • fever, death • survivors - growth retarded, skin lesions, arched backs. Can live for 100+ days • live for 100+ days – “Textbook” lesions of CSF are seen – Seropositive – ab levels may fluctuate • Difficult to diagnose by serology if vaccine used – Virus positive • PCR or antigen ELISA – Antibody may interfere with AgELISA – “Textbook” lesions of CSF are seen 21 22 CSF (IP1) X2.5 Note skin lesion Distribution - not typical CSF - encrusted eyelids - conjunctivitis 23 24 4 29/07/18 CSF - skin lesions CSF (IP6) - skin lesions on perineum x2 25 26 Late onset disease - Congenital infection CSF - more extensive skin lesions (EURL Hannover) (van Oirschot & Terpstra 1977) – High amounts of virus excreted – gradually aggravating depression and anorexia – normal to slightly elevated temperatures – conjunctivitis, dermatitis, locomotory dysfunction – Death - 2 to 11 months – Seronegative – MUST detect virus to identify them! • PCR or antigen ELISA • If one detected, cull whole litter 27 28 Gross pathology: lesions of acute CSF (1) • Multiple haemorrhages - various sizes – haemorrhages of lymph nodes • peripheral or diffuse - marbled red to near-black • LN swollen, oedematous, haemorrhagic • virtually all LN may be affected – haemorrhages of kidney □ petechiae to acchymotic □ more frequently on cortex □ Also seen in urinary bladder, larynx, epiglottis, heart, intestinal mucosa, serous and mucous membranes, skin (cyanotic) 29 30 5 29/07/18 Hepatogastric lymph nodes - enlarged & haemorrhagic CSF (IP6) ASF CSF (IP11) 31 Gross pathology: lesions of acute CSF (2) Splenic infarcts • Infarction of the spleen CSF (IP11) – almost pathognomonic • disrupted blood flow - occlusion of capillaries by thrombi – Raised, dark blebs of various sizes □ singly, or as a series, coalescing along the edge of the spleen ASF □ Similar lesions in gall bladder and tonsil • septicemic complications □ - suppurative tonsilitis □ - fibrinous bronchopneumonia PDNS 33 34 Kidney haemorrhages lymphosarcoma PDNS CSF - textbook & (IP11) - fetus ASF 35 36 6 29/07/18 CSF: fetal death, mummification and size variation Gross pathology: lesions of acute CSF (3) • mummification, stillbirth, malformations • in stillborns: • subcutaneous oedema • hydrops ascities • hydrothorax • deformities of head and limbs • hypoplasia • in newborns: □ petechial haemorrhages of skin and internal organs 38 Gross lesions of chronic CSF CSF - caecal ‘button ulcers’ • Infarction of the spleen – less pronounced than acute disease Farm IP8 • Ulceration of caecum and colon – often with necrosis - “button ulcers” • Rib lesions Farm IP6 – transverse line of semisolid bone across rib, proximal from costochondral junction □ growing pigs □ sudden calcification of cartilage cells □ maybe also on growth plates of long bones 10mm 39 40 Gross lesions of late-onset CSF Sick pigs - some other causes PMWS PDNS • Relatively few overt lesions • thymic atrophy – most pronounced lesion • lymph node swelling PRRS swine influenza 41 42 7 29/07/18 Pleuropneumonia Benign periparturient erythema Salmonella choleraesuis septicaemia (Eich K- Warfarin poisoning O, 1993) Transit erythema Smith, Taylor and Penny (1990). Diseases Salmonella enterica Choleraesuis and Disorders of the Pig. Wolfe streptococcal Thrombocytopenic purpura Publishing infection 43 meningitis 44 Live CSF vaccines Prevention and control Use of vaccination - the theory • Chinese “C” strain • Does NOT prevent infection OR excretion – Rabbit attenuated • Japanese GPE-negative strain • Should result in: – Attenuated in guinea pig cells – Temperature sensitive • A lower susceptibility of vaccinated pigs to infection • Thiverval • And if subsequently infected: – Cell culture and low temperature attenuation – Reduced severity of disease • Also: – Decreased virus excretion – Russian CS & LK strains – rabbit attenuation & cell culture passage – Prevention