Histopathological changes in the coeliaco-mesenteric ganglia of horses with ‘mal seco’, a grass sickness-like syndrome, in Argentina.

This research analyzes the cellular level changes in a specific nerve group in horses suffering from ‘mal seco’, an illness similar to grass sickness. The study found that the severity and range of the nerve damage were more extensive in horses with shorter disease durations, and these changes were also similar to those observed in European horses with grass sickness, suggesting a possible link between the conditions.

Detailed Explanation

The research conducted entailed an in-depth histopathological examination of the coeliaco-mesenteric ganglia which are crucial nerve centers in the horses’ bodies. This was performed on a total of eight horses – four with ‘mal seco’ and four who died from unrelated causes (acting as controls).

• The most substantial damages were found in the two ‘mal seco’ horses with the shortest clinical course, indicating a faster-progressing disease may exacerbate the severity and extension of the nerve damage.
• The main nerve degenerations comprised of ‘Nissl substance’ reduction (a material found in nerve cells), cellular cavities, neuronophagia (neuronal damage or death), foreign and internal eosinophilic bodies (types of white blood cells), as well as abnormal nuclei. This assessed the extent of cell damage within nerve groups and its consequences on their function.
• No similar anatomical defects were present in the control horses, implying the observed nerve damages were likely disease-specific and not common in healthy horses.

Comparison to Grass Sickness

The research found the pattern of lesions in the affected ‘mal seco’ horses to be strikingly similar to histological changes seen in horses suffering from grass sickness in Europe. The similarity provides evidence that the diseases may, in fact, be identical.

• This comparison involves assessing the same type of nerve damage across different geographical locations and potentially different strains of disease – a critical step in understanding the biological mechanism of the disease.
• Grass sickness, also termed dysautonomia, is a disease prevalent primarily in horses in the United Kingdom, but its cause is still largely unknown. If ‘mal seco’ and grass sickness are indeed one and the same, insights from one can facilitate the understanding, prevention, and cure strategies for the other.