Gasterophilus nasalis infection: prevalence and pathological changes in equids in south-west England.

The research is a study on the prevalence and pathological impact of Gasterophilus nasalis, a botfly species, infections in horses and ponies in South West England. It investigates the population of this fly species in two separate periods and the resulting pathological changes in the duodenum of the animals.

Objective of Research

• The study aimed to determine the commonality of Gasterophilus species, particularly Gasterophilus nasalis, in horses and ponies in the south-west of England.
• The researchers wanted to understand how the use of ivermectin, a common drug for nematode control, influences the prevalence of this botfly species.
• They were also interested in identifying any pathological changes in the animals’ duodenum tied to G. nasalis infections.

Methodology

• The researchers visited a licensed horse abattoir in south-west England at different periods (December 1995-January 1996 and February 1997).
• Stomach and duodenum parts of 62 healthy equids (horses, ponies etc.) were collected for counting and speciating of the bots.
• In the second period, the same parts from 27 healthy Dartmoor ponies were analysed as well. Tissue samples from 21 of these ponies were further processed and stained for a histological examination.

Findings

• The prevalent species was G. intestinalis, as it existed in all animals that had not received boticide treatment for the previous six months.
• G. nasalis was only found in the Dartmoor ponies and a horse owned by the same person. These animals had received no treatment, making the occurrence of the botfly species significant.
• The larvae were found in clusters in the duodenum of the Dartmoor ponies, causing visible pathological changes such as firming of the submucosa and inflammation.

Conclusion

This study highlights the potential for G. nasalis infection in regions where horses do not receive ivermectin treatment. The identifiable pathological changes associated with the infection also underscore the need for a preventative measure, like ivermectin, to control the prevalence of Gasterophilus species, especially in Dartmoor ponies.