Neospora

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Revision as of 22:41, 9 April 2010 by Bara (talk | contribs) (Created page with '*2 main species **''Neospora caninum'' in the dog **''Neospora hughesi'' in the horse *Sporulated oocysts measuring just 10μm *Oocyst contains 2 sporocysts with 4 sporozoites …')

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  • 2 main species
    • Neospora caninum in the dog
    • Neospora hughesi in the horse
  • Sporulated oocysts measuring just 10μm
  • Oocyst contains 2 sporocysts with 4 sporozoites
  • Route of transmission not fully understood
  • Often misdiagnosed as Toxoplasma gondii
    • Sarcocystis cysts have thicker walls
  • Infection diagnosed by IFAT, ELISA or PCR
    • Identification of lesions and organisms in tissue using immunohistochemical staining
    • Eliminate other causes of abortion first

Life cycle

  • Life cycle similar to Toxoplasma gondii
  • Limited range of warm-blooded intermediate hosts
    • Asexual reproduction occurs in intermediate host forming tissue cysts
  • Host range of sexual stage is unknown for N.caninum
    • Intermediate host for N.hughesi is the horse, but the definitive host is unknown
  • Final host
    • Dogs pass oocysts
    • Role not fully understood in pathogenesis
    • 5 day prepatent period
    • Other wild canids may also act as final definitive hosts
  • Intermediate host
    • Mostly cattle
    • Natural infection has been documented in other herbivores
  • Transmission
    • Transplacental infection occurs in all intermediate hosts and in the canine final host
      • Transplacental transmission can occur in successive pregnancies
    • In cattle, vertical transmission occurs
      • Post-natal infection occurs but is less common

Pathogenesis

  • Dogs
    • Occurs mainly in puppies
    • Causes ascending paralysis, especially of hind limbs, with muscle wasting
    • Causes sudden collapse due to myocarditis
    • More than 1 puppy in a litter may be affected, although this may not occur simultaneously
    • Successive litters affected
  • Cattle
    • Commonest cause of infectious abortion in dairy cattle
    • Congenitally infected calves can have encephalomyelitis and paresis
    • Abortion usually occurs between 5-7 months of gestation but can occur as early as 3 months
    • No other clinical signs in the cow
    • Repeat abortions possible in same cow (persistently infected)
  • Horses
    • Myeloencephalitis
    • Transplacental infection occurs
    • Disease only diagnosed in USA

Prevention and Control

  • Do not allow dogs access to calving cows, placental membranes and aborted or dead calves
  • Do not allow dogs to defecate in cattle feeding areas
  • Identify and cull seropositive cattle, or do not breed from them or their progeny
  • Select seronegative cattle for breeding
  • Vaccinate
    • Only in the USA
    • Neoguard or Intervet
    • Killed protozoal vaccine for healthy, pregnant cows
    • Dosed in first 3 weeks of pregnancy and then every 3-4 weeks during gestation
    • Revaccination with 2 doses during each subsequent pregnancy