Pasture borne smt

• Platyhelminthes - flatworms:

  • Bilateral symmetry
  • Body cavity lacking (acoelomata)
  • Three layers
  • Hermaphrodites (some exceptions)
  • No respiratory and circulatory system
  • Simple excretory system
  • Centralized nervous system
• Classes of Platyhelminthes:

  • Monogenea (direct life cycle)
  • Trematoda
  • Cestoda
  • Turbellaria (non-parasitic)
• Characteristics of class Trematoda:

  • Endoparasites, occasionally ectoparasites
  • Parasites of vertebrates
  • More than 2700 genera and 8000 species
  • Oral and ventral sucker
  • Parasitizing all organ systems
  • Complex indirect life cycle with 1-3 intermediate hosts
• Taxonomy of trematodes:

  • Aspidogastrea
  • Digenea
  • Diplostomida
  • Plagiorchiida
  • Brachylaimoidea
  • Diplostomoidea
  • Schistosomatoidea
  • Other superfamilies: 19 (including Echinostomatoidea, Opistorchioidea, and Gorgoderoidea) (None of veterinary or medical importance)
• Characteristics of Digenean Trematodes:

  • All digenea are parasitic endoparasites of vertebrates
  • Dorso-ventrally flattened body with simple anatomy and without segmentation
  • No coelom, but animals are filled with mesodermal parenchyma
  • No blood vessels, simple ladder nervous system
  • Possess two suckers (oral and ventral acetabulum) for attachment within the host
• Reproductive system of Digenean Trematodes:

  • Most trematodes are hermaphrodites
  • Cross as well as self-fertilization occurs
  • Gonochorists (family Schistosomatidae) show sexual dimorphism
• Life cycles of trematodes:

  1. Fasciola hepatica (Fasciolidae)

  2. Opisthorchis viverrini (Opistchorchiidae)

  3. Schistosoma (Schistosomatidae)
• Trematode families of veterinary importance:

  • Paramphistomidae
  • Fasciolidae
  • Dicrocoeliidae
  • Opisthorchiidae
  • Paragonimidae
  • Schistosomatidae
• Family Fasciolidae:

  • Fasciola hepatica
  • Fasciola gigantica
  • Fascioloides magna
• Fasciola hepatica (common liver fluke):

  • Adults: 2-4 cm, feed on blood
  • Localization: liver (bile ducts)
  • Definitive hosts: cattle, sheep, goat, buffalo
  • Worldwide distribution
  • Infection of humans: more than 2.6 million are infected
  • Intermediate host: freshwater snails (Galba truncatula)
• Epidemiology of F. hepatica (and Galba spp.):

  • Summer and winter infection periods for intermediate hosts
  • Risk periods year-round in the UK and France
• F. hepatica in France:

  • Pathogenicity includes parasitic migration within liver parenchyma and flukes in biliary ducts
• Clinical signs of fasciolosis:

  • Acute, subacute, and chronic forms
  • Symptoms include sudden deaths, anemia, hypoalbuminemia, enlarged and painful livers, poor body condition, decreased milk production, and reduction of weight gains
• Clinical signs of Ovine fasciolosis depend on the burden of infection
• Acute infection with many metacercariae (>2000) over a short period of time can lead to diffuse liver hemorrhages from flukes' migrations
• Signs of acute infection in autumn/winter include sudden death of many animals 2 weeks post-infection, with surviving animals becoming anemic and weak
• Sub-acute infection with fewer metacercariae (500-1500) over a longer period of time can result in parasites in biliary ducts and others still migrating in hepatic tissue
• Signs of sub-acute infection in autumn/winter include anemia, jaundice, and potential death 8-10 weeks post-infection if not treated, with 1-2 weeks of clinical signs before death
• Chronic infection with few metacercariae (200-500) over a diffuse period of time can lead to several hepatic damages such as hepatic fibrosis, cicatrization of migratory lesions, parasites in biliary ducts, and hyperplastic angiocolitis from physical damage
• Signs of chronic infection in late winter/spring include anemia, weight loss, edema, and ascites
• Cattle develop immunity to fasciolosis and can remove the infection in less than one year, while in sheep, the infection can be life-lasting
• Diagnosis of F. hepatica can be done through post mortem examination, coprology (faecal egg counts), immunodiagnosis (ELISA, WesternBlot), biochemical analysis, and molecular methods (PCR, LAMP)
• Post mortem diagnosis involves observing typical pathological changes in livers like fibrosis, calcification of bile ducts, and hyperplasia of bile ducts
• Coprology for diagnosis includes sedimentation technique or flotation with zinc sulfate, with eggs detectable from 9-12 weeks post-infection, but with intermittent excretion leading to false negative results
• Immunodiagnosis methods include ELISA for detecting specific antibodies in serum or milk, as well as detecting F. hepatica antigen in serum or faeces
• PCR can be used to detect F. hepatica larval stages in snails and eggs in faeces, allowing for distinguishing between different parasite eggs
• Control of fasciolosis involves the use of anthelmintics (flukicides) and alternative approaches, with considerations for timing, drug selection, and withdrawal periods
• Active compounds can be used for different stages of liver fluke infection in sheep and cattle, with the possibility of resistance to flukicides
• Other related parasites include Fascioloides magna, Dicrocoelium dendriticum, Paramphistomum cervi, Calicophoron daubneyi, and Schistosomes, each with specific characteristics and hosts
• Cestodes in ruminants have a segmented body with scolex and proglottids, are hermaphrodites, and have a 2-host life cycle, with examples like Anoplocephala, Moniezia, Taenia spp., and Echinococcus spp.
• Anoplocephala species include A. magna, A. perfoliata, and Paranoplocephala mamillana, with different sizes and habitats in the intestine, with Oribatid mites as intermediate hosts
• Moniezia species include M. expansa and M. benedeni, parasites of ruminants with oribatid mites as intermediate hosts
• Symptoms of Anoplocephala infections include enteritis, colic, and diarrhea, with treatment options like praziquantel and pyrantel
• Moniezia eggs are triangular with a piriform apparatus