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Congenital sporozoan encephalomyelitis in a calf
1Pathology Department, Ministry of Agriculture, Fisheries and Food, Central Veterinary Laboratory, New Haw, Weybridge, Surrey.
Abstract:
Protozoan encephalomyelitis was diagnosed post mortem in a five-day-old Friesian calf which had shown nervous signs from birth. The lesion was a subacute necrotising multifocal encephalomyelitis associated with protozoan bodies (6 X 6 microns to 16 X 30 microns). Ultrastructurally these bodies corresponded to apicomplexan meronts composed of eight to 89 merozoites which reproduced by internal budding to form paired daughter cells (endodyogeny). The merozoites were indistinguishable from Toxoplasma gondii; they reacted weakly with anti-Sarcocystis species serum and did not cross react with anti-T gondii serum. The generic identity of the sporozoan was not established, but it is unlikely to have been either Sarcocystis species or T gondii.
Insights
A protozoan infection caused fatal encephalomyelitis in a calf. The causative agent, an apicomplexan parasite, was identified through ultrastructural analysis but its exact species remains undetermined.
Area of Science:
- Veterinary Pathology
- Protozoology
- Molecular Biology
Background:
- Neonatal calf diseases can significantly impact livestock health and productivity.
- Protozoan infections are a notable cause of neurological disorders in young animals.
- Accurate diagnosis of encephalomyelitis is crucial for effective disease management.
Observation:
- A five-day-old Friesian calf presented with congenital nervous signs.
- Post-mortem examination revealed subacute necrotising multifocal encephalomyelitis.
- Microscopic examination identified protozoan bodies within the brain lesions.
Findings:
- Ultrastructural analysis characterized the protozoan bodies as apicomplexan meronts.
- Meronts contained 8-89 merozoites, reproducing via endodyogeny.
- Merozoites resembled Toxoplasma gondii but showed weak reactivity to anti-Sarcocystis serum and no cross-reactivity with anti-T. gondii serum, suggesting a novel or unclassified species.
Implications:
- This case highlights a potential new etiological agent of encephalomyelitis in calves.
- Further research is needed to definitively identify the protozoan species and its life cycle.
- Understanding this pathogen could lead to improved diagnostic tools and preventative strategies for bovine neurological diseases.