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Neosporosis

Neosporosis is the infectious disease of animals caused by Neospora caninum (Neospora or N. caninum for short). Neospora is a protozoan parasite (i.e. a microscopic, unicellular parasite organism) that can invade, live and multiply inside animal cells. It is one of the most frequently diagnosed infectious causes of abortion in cattle worldwide.

The parasite is closely related to Toxoplasma gondii. Unlike T. gondii, which is an important infectious cause of abortion in sheep and goats, Neospora causes disease primarily in cattle and dogs. Another significant difference to Toxoplasma is that Neospora can cause repeat abortions in successive pregnancies and that the parasite is very effectively transmitted from an infected dam to its foetus.

Since its identification in the 1980s, Neospora has emerged as one of the most common infectious causes of abortion in cattle worldwide, resulting in significant economic losses and production inefficiency. Cattle may become infected by ingesting oocysts (parasite eggs) or by acquiring the parasite in the uterus from their mothers.

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The video below from a 2012 episode of BBC Landward highlights how oocysts shed in the faeces of infected dogs can contaminate the environment and pose a risk to cattle:

 

Key Points

  • Neospora caninum is a protozoan parasite and is a commonly diagnosed cause of abortion in cattle in UK and other countries worldwide
  • The dog is the definitive host of the parasite, and if dogs eat tissue contaminated with Neospora, the parasite develops in the gut of the dog, and Neospora oocysts (eggs) are shed in faeces into the environment
  • Cattle may become infected through ingestion of infective oocysts on pasture or in contaminated feed and water
  • In pregnant cattle Neospora parasites may pass from an infected mother to the developing foetus and depending on when this happens during gestation the outcome can be death/abortion of the foetus, still birth or birth of a congenitally infected calf
  • Neospora parasites establish persistent infections in cattle and during pregnancy the parasites becomes active and are vertically transmitted to the developing foetus, this can occur over successive pregnancies and is an efficient way to spread Neospora infection in a herd
  • Buying in cattle that are persistently infected with Neospora is a common way to introduce infection to the herd
  • Neospora is not transmitted from cow to cow
  • Diagnosis of the disease is done through detection of the parasite in foetal and/or placental tissues and through detection of specific antibodies in blood or milk samples or foetal fluids
  • There are currently no vaccines to prevent disease or infection with Neospora and no licenced treatments
  • Prevention and control of neosporosis relies on biosecurity and management practices to: limit access of dogs to cattle areas, prevent introduction of persistently infected cattle and apply a test and cull policy and informed breeding strategy for the herd
  • There are various Cattle Health Certification Standards (CHeCS) health schemes that include testing for Neospora

Research at Moredun

Current interests and future aims:

  • Development of a vaccine that prevents bovine abortion and transmission of the parasite.
  • Development of improved diagnostic tests, which can reliably detect carrier animals.
  • Identify N. caninum antigens that are recognised by protective immune responses.
  • Improve understanding of N. caninum pathogenesis to determine how infection of N. caninum leads to abortion and may lead to immunological tolerance.
  • Identify factors involved in parasite reactivation during infection as these may be targets to reduce vertical transmission.
  • Evaluate N. caninum transmission dynamics on farms and in wildlife hosts to identify targets that will reduce the spread of the pathogen.
  • Assessment of disease impact depending on route of original infection i.e. congenital infection versus horizontal transmission.
  • Assessment of the economic impact of the disease.
  • Improve N. caninum control strategies to provide better advice for farmers.

Research Funding

Moredun is conducting research on Neospora parasites within the Scottish Government Strategic Research Programme (2016-2021) looking at developing new diagnostics to determine prevalence and to distinguish different abortifacients in abortion cases of ruminants.

 

BBSRC-Zoetis PhD studentship: Specific diagnostic tools for protozoan infection of ruminants.

This PhD studentship is conducted at the Moredun Research Institute in collaboration with the University of Edinburgh Veterinary School and focuses on the development of molecular tools for the discrimination of Neospora caninum, Toxoplasma gondii and Sarcocystis species in pathology specimens from clinical cases. To achieve this, the PhD project will produce of species specific antibodies against recombinant proteins of protozoan parasites that can be used for the diagnosis of protozoan causes of abortions in ruminants. A second aim of the PhD is to develop a species specific PCR that can detect and distinguish common protozoan abortifacient of ruminants.

 

BMGF project, Supporting Evidence-Based Interventions (SEBI): Causes and extent of mortality of domestic ruminants in Tanzania.

Scientists at the Moredun Research Institute are working closely with colleagues at the University of Glasgow and colleagues from several organisations within Tanzania in order to determine the significance of Neospora caninum, Toxoplasma gondii and Chlamydia as infectious causes of abortion in sheep, cattle and goats in Tanzania.

A news release with further information about this project can be found here.

 

AHDB funded PhD studentship entitled: Development of diagnostics for the detection of Neospora caninum infected carrier cattle.

The aim of this PhD project is to identify different stage specific antigens of the protozoan parasite Neospora caninum that are immunogenic, express them as recombinant proteins and to evaluate them for use in an ELISA that will be able to identify cattle persistently infected with Neospora caninum.

Farming and Veterinary Outreach

For further Information about Neosporisus please see Moredun Newssheet 7.4 - Control of Neosporosis in Cattle:

Moredun has also produced a Farmer's Guide along with Arla and Morrisons.  This booklet is available to view online or to order a free hardcopy please email info@moredun.org.uk.