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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

  • Neosporosis is caused by a microscopic protozoan parasite called Neospora caninum
  • Neospora is one of the most frequently diagnosed infectious causes of abortion in cattle worldwide
  • Cows that are infected with Neospora are 5 to 7 times more likely to abort than uninfected cows, although they will not show any other clinical signs
  • Oocysts are shed in the faeces of acutely infected dogs and contaminate the environment
  • Cattle may become infected by ingesting oocysts (parasite eggs) or by acquiring the parasite in the uterus from their mothers
  • Neospora transmission from mother to foetus is very efficient and, in infected animals, may occur in up to 95% of pregnancies
  • Since the parasite establishes persistent infections that may reactivate during successive pregnancies, infected animals may pass the infection to their offspring over several generations
  • Dam to foetus transmission is the most common route of infection for Neospora
  • Buying in infected animals is one of the most likely ways to introduce the disease into a herd
  • Diagnosis of bovine neosporosis can be reached by submitting aborted foetuses for post-mortem investigation or by detecting parasite specific antibodies in the blood or milk of infected live animals
  • Positive antibody tests are reliable but a negative results does not mean that an animal is not infected
  • Currently, there are no effective vaccines to prevent Neospora infection and/or abortion
  • At present, there are no licensed drugs for bovine neosporosis
  • Control of bovine neosporosis is based on biosecurity and management practices
  • Enhanced biosecurity measures should aim at limiting dog access to cattle areas, feed and water sources as well as preventing the introduction of persistently infected animals
  • Testing cows for Neospora specific antibodies and removing positive animals will help to reduce the prevalence of the disease in a herd and therefore the risk of Neospora abortion cases
  • If you think you may have Neospora problems on your farm, contact your veterinary practice to assess the risk and impact of the parasite on your herd and to decide the best course of action
  • Bovine neosporosis has recently been included in CHeCS (Cattle Health Certification Standards) therefore CHeCS licensed health schemes include control programmes that are specific for bovine neosporosis
  • There is no evidence that cow to cow transmission can occur
  • There is no evidence that Neospora can infect or cause disease in humans

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 Cryptosporidiosis please see Moredun Newssheet 6.9 - 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.