Epidemiology, chronobiology and taxonomic updates of Rhinoestrus spp. infestation in horses of Sardinia Isle, Western Mediterranean (Italy).

The research examines the prevalence and characteristics of Rhinoestrus spp. infestations in horses from Sardinia, Italy, over a year (2008). It discovered that a significant percentage of horses were infested, and provided insights into the life cycle of the pest and the most effective time for applying control measures.

Study Overview and Methodology

• The research was conducted over a year (2008) on 265 horses that were slaughtered in Sardinia, Italy. The horses were examined for the presence of Rhinoestrus spp., a species of fly whose larvae infest horses, through analyzing the nasal cavities and pharynges.
• A total of 2108 larvae were collected for the study. These were classified into stages of development, or instars, with 66% being first instar (L1), 22% second instar (L2) and 12% third instar (L3). The most common location for the larvae was the ethmoid, while the least was the larynx.

Epidemiology and Chronobiology

• 49% of the examined horses were found to be infested with the larvae, indicating a high level of infestation. The average number of larvae per infested horse was approximately 16, with an abundance of around eight.
• The research suggested three periods in the lifecycle of the larvae: the diapause (September-February) where the first larval stage dominated; the active endogenous phase (February-September) which saw increases in L2 and L3; and the exit phase (May-September), which was marked by a further increase in L1.

Taxonomic Findings

• Morphological examination of the L3 larvae identified different features. 8% were identified as Rhinoestrus purpureus, 8% as Rhinoestrus usbekistanicus, and 84% had intermediate features, not clearly identifiable as either.
• However, biomolecular analysis of the COI gene showed uniform genetics across the larvae, suggesting the presence of a single species in the Mediterranean region.

Recommendations

• The study highlights the need for control measures to manage the infestation given its widespread occurrence among Sardinian horses. The researchers recommend the use of chemotherapy during the diapause period to reduce the presence of L1 stages and interrupt the lifecycle of the infestation.