From Parasite Cycle Study to Control Methods Definition
Each year, in cattle farms worldwide, strange series of abortions strike between the 5th and 7th month of gestation, with no apparent cause. The culprit: bovine neosporosis, a silent parasitic disease that represents the leading cause of abortions in France, ahead of Q Fever, and causes economic losses estimated at $1.3 billion annually worldwide 1 3 .
Primary cause of bovine abortions in France
$1.3 billion in annual losses worldwide
Parasite identified in the 1990s
Behind these figures lies a parasite called Neospora caninum, whose complex cycle involving dogs and cattle was only discovered in the 1990s. In the absence of treatment and vaccines, the fight against this disease relies on a detailed understanding of its parasitic cycle and the implementation of rigorous management measures.
Dog ingests infected tissues
Oocysts excreted in feces
Cattle ingest oocysts
Neospora caninum is a protozoan parasite of the coccidia family, very close to the agent of toxoplasmosis 1 5 . Like many parasites, its cycle involves two types of hosts.
In cattle, transmission can follow two distinct but sometimes intertwined paths:
This pathway represents approximately 5% of cases but is crucial for the initial introduction of the parasite into a herd 5 .
1 Dog becomes contaminated by ingesting infected tissues (placentas, aborted fetuses, calf carcasses) 2 6
2 Parasite reproduces in its intestine and the dog excretes oocysts in its feces 2
3 These oocysts, highly resistant in the environment (can persist for up to one year), contaminate the environment, grass, forage, or water 2
4 Cattle ingest these oocysts while grazing or drinking 2
Fact: A single contaminated dog stool can potentially infect up to 1,000 cows, with the risk increased by the use of feed mixers 6 .
This is the predominant transmission route (95% of cases), where the parasite is transmitted from mother to fetus through the placenta 5 .
This transmission is almost systematic (80 to 100% of cases) if the mother was herself born infected 2 9 .
Animals infected by this route remain infected for life, becoming chronic carriers of the parasite.
Dormant forms (bradyzoites) are maintained in muscle cysts or in the central nervous system, protected from the immune system 1 .
| Aspect | Horizontal Transmission | Vertical Transmission |
|---|---|---|
| Frequency | Approximately 5% of cases 5 | Approximately 95% of cases 5 |
| Source | Environment contaminated by dogs | Infected mother |
| Carriers | Cattle can become negative again after a few months 7 | Lifelong carriage 2 |
| Herd Impact | Waves of abortions 8 | Occasional and repeated abortions 8 |
| Placental Transmission | Possible if infection during gestation | Almost systematic (80-100%) 2 9 |
Neosporosis manifests its severity almost exclusively in pregnant animals. This phenomenon is explained by the immune changes that occur during pregnancy 1 .
A recent epidemiological study (2024) conducted in the Huila region of Colombia provided valuable insights into the factors influencing transmission of neosporosis, particularly in humid tropical areas where the disease has a significant impact 3 .
This cross-sectional study covered 150 farms from 24 municipalities, with 360 cattle sampled. Researchers used a structured questionnaire of 128 questions covering farming practices, management, biosecurity and socioeconomic aspects 3 . Serological diagnosis was performed using the indirect ELISA technique, the reference method for detecting antibodies against N. caninum 3 .
The overall seroprevalence observed was 53% (191/360 animals), confirming intense circulation of the parasite in this region 3 .
The marked regional disparity, with particularly high prevalence in the South (80%), suggests the influence of environmental factors or specific farming practices 3 .
To date, no drug treatment or vaccine is available against bovine neosporosis 1 2 . Several concordant sources explain this absence by the lack of economic interest of veterinary pharmaceutical laboratories to develop necessarily expensive solutions, creating a "gap between the importance of the disease in the field and its knowledge by scientific circles" 1 .
Faced with this therapeutic impasse, professionals have developed management methods based on a detailed understanding of the parasitic cycle:
| Tool/Technique | Function | Application |
|---|---|---|
| ELISA Test (INgezim® Neospora 3.0) | Detection of specific anti-N. caninum antibodies | Serological diagnosis on serum or milk 3 |
| PCR | Detection of parasitic DNA | Direct diagnosis on fetal tissues 6 |
| Epidemiological Questionnaire | Collection of farming practices | Identification of risk factors 3 |
| Statistical Analysis by Logistic Regression | Measurement of associations between variables | Identification of risk and protective factors 3 |
The fight against bovine neosporosis perfectly illustrates how detailed understanding of a parasitic cycle can compensate for the absence of conventional therapeutic solutions. By dissecting the relationships between definitive and intermediate hosts, science has enabled the development of targeted control strategies that, although restrictive, prove effective.
Recent research, such as the Colombian study, emphasizes the importance of environmental factors and farming practices in disease dynamics. They pave the way for increasingly integrated prevention approaches, combining biosecurity, management of dog populations and reasoned genetic selection.
As climate change and the evolution of farming systems could modify the epidemiology of neosporosis, collective vigilance and diagnostic innovation will remain our best assets to contain this discreet but formidably effective parasite.